Yonatan Zunger2013-06-28 05:43:23
This is a great illustration of collective phenomena. If you look closely, each dot is just moving around in a regular circle; but because the different circles are out of phase with each other, when you back away you see waves steadily moving across the screen. It's a simple demonstration of how large-scale, collective phenomena can emerge from very simple small-scale behavior. Things like this happen all over the place: water waves and sound waves, for example, work in basically the same way, with the small back-and-forth motions of individual molecules leading to compression patterns moving through the air. 

Originally from http://i.imgur.com/ckxfccq.gif , and found via +Jane Shevtsov and +W Younes. (Edited: Originally by david & brian of Bees & Bombs: http://beesandbombs.tumblr.com/)
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  • Yonatan Zunger2013-03-07 19:04:34
    Jupiter and the Sun are the two largest objects in our Solar System, and as they orbit around one another, they create regions where their gravity roughly cancels out. These are the Lagrangian points, created whenever two objects orbit one another: places where gravity is such that another small object can follow along in the orbit without being pulled in or out. And since things aren't getting pulled out of there, they get stuck in there as well: and so we have two large clumps of asteroids (and miscellaneous smaller space debris) in Jupiter's orbit. These are called the Trojan Asteroids; the group ahead of Jupiter is known as the Greek Camp, and the group behind it the Trojan Camp, with the asteroids in each camp being named after famous people in that war. Together, these two camps have as many asteroids as the Asteroid Belt.

    Other stable patterns are possible, too: another one is what's called a 3:2 resonance pattern, asteroids whose motion gets confined to a basically triangular shape by the combined pull of Jupiter and the Sun. This group (for Jupiter) is called the Hilda Family, and their route forms a triangle with its three points at the two Lagrange points and at the point on Jupiter's orbit directly opposite it from the Sun. 

    None of these orbits are perfectly stable, because each of these asteroids is subject to pulling from everything in the Solar System; as a result, an asteroid can shift from the Lagrange points to the Hilda family, and from the Hilda family to the Asteroid Belt (not shown), especially if it runs into something and changes its course. 

    The reason that Pluto was demoted from planet to dwarf planet is that we realized that these things are not only numerous, but some of them are quite big. Some things we formerly called asteroids are actually bigger than Pluto, so the naming started to seem a little silly. So our Solar System has, in decreasing order of size, four gas giant planets (Jupiter, Saturn, Neptune and Uranus); four rocky planets (Earth, Venus, Mars, and Mercury); five officially recognized dwarf planets (Eris, Pluto, Haumea, Makemake, and Ceres); and a tremendous number of asteroids. (We suspect that there are actually about 100 dwarf planets, but the job of classifying what's an asteroid and what's actually a planet is still in progress -- see the "dwarf planet" link below if you want to know the details)

    Ceres orbits in the Asteroid Belt, about halfway between Mars and Jupiter, just inside the triangle of the Hilda Family; Pluto and Haumea are both in the distant Kuiper Belt, outside the orbit of Neptune but shepherded by its orbit in much the same way that the Hildas are shepherded by Jupiter; Makemake is what's called a "cubewano," living in the Kuiper Belt but unshepherded, orbiting independently; and Eris is part of the Scattered Disc, the even more distant objects whose orbits don't sit nicely in the plane of the Solar System at all, having been kicked out of that plane by (we believe) scattering off large bodies like Jupiter.

    But mostly, I wanted to share this to show you how things orbit. This picture comes from the amazing archive at http://sajri.astronomy.cz/asteroidgroups/groups.htm, which has many other such pictures, and comes to me via +Max Rubenacker

    More information about all of these things:
    http://en.wikipedia.org/wiki/Lagrangian_point
    http://en.wikipedia.org/wiki/Trojan_(astronomy)
    http://en.wikipedia.org/wiki/Hilda_family
    http://en.wikipedia.org/wiki/Dwarf_planet
    http://en.wikipedia.org/wiki/Kuiper_belt
    http://en.wikipedia.org/wiki/Scattered_disc

    #ScienceEveryDay
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  • Yonatan Zunger2012-05-17 07:51:30
    There's really no point to this except that they got a bunch of really fast cars on a runway and put them through a quarter-mile. A Bugatti Veyron, a Lamborghini Aventador, a Lexus LFA, and a McLaren MP4-12C. If that doesn't sound kind of awesome to watch, then this is probably not the video for you.

    h/t +Abe Rahey for the link...
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  • Yonatan Zunger2014-01-17 02:38:00
    "Sleeping Between His Parents," by Abdulaziz al-Otaibi.

    I wanted to share this with you because it served as such a potent reminder of why I do what I do. My family has been shaped by war; everyone's lives were shaped by the wars they survived (and others didn't), by the places they fled to, by the fears of other wars to come. 

    Our world is broken. It is broken in so many ways that sometimes it's hard to count. This is the consequence of things we cannot control: of the lack of infinite resources, of our natural tendencies to want to protect ourselves at the expense of others, of history, of habit. It is the consequence of a universe with free will in it.

    These are things we can change. We have exceptional power in the world: not infinite power, but some power in each of our hands, and great power combined. If we have any useful purpose, it is to fix the evils of the world.

    The Rabbis tell us that on the day the Messiah comes, we will all be instituted into perfect health, want will be eliminated from the world, and a regime of perfect justice will be instituted: and that on that day, nobody will notice, because the condition for the Messiah to come is that we will have first created, by our own hands, the Messianic kingdom in the world. 

    This is not an easy task, nor is it one we should expect to achieve in our lifetimes. That's OK. But it is important to work towards it, every day.

    Not all of these things are obvious. It's not hard to guess what a teacher or a doctor does to repair the world, but that's only a small part of it. The construction worker who builds a house with all of his abilities, the parent who raises a child to be kind and thoughtful, the writer who puts our thoughts into words so that we can understand ourselves better, the public servant who honestly and diligently works to create justice and wealth, the scientist who adds to our store of knowledge and opens new doors of understanding, all help to build up the world. And the builder who leaves something shoddy because nobody will ever know, the parent who encourages their child's baser instincts, the propagandist, the corrupt official, all take down the work that the rest of us are trying to build.

    I'm sharing this image with you because you should never, in all the days of your life, forget the stakes of what we do. Will the things we build prevent this? Will they comfort the child, help him in the days that are to come? What could we have done differently, and what can we do in the future?

    Think about these things night and day: write them on the doors of your house, hold them in front of your eyes. Spend your time thinking about the choices you make individually and the choices we make as a society: are these the choices which will lead to the best consequences? Why? Why not? Debate these things every day with your friends and your family, and with strangers and people who disagree with you. Make your work an offering, every day, towards the repair of the world.

    The Mishna says: It is not yours to finish the task, but neither are you free to set it aside. Never forget that.

    (The image was shared with me by +Sreek Menon. The original photograph is by Abdulaziz al-Otaibi, a Saudi photographer who created it as part of a project discussing the love of a child for his parents. You can see more of his work at http://instagram.com/abdulaziz_099)
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  • Yonatan Zunger2012-07-16 03:10:12
    This is an amazing photo. One of those that looks like it couldn't possibly be real.

    (Has it ever occurred to you how spectacularly fortunate we are to live on a planet which can have total eclipses? It requires that the apparent size of the Moon and the apparent size of the Sun match to within a few percent, so that the Moon can hide the body of the Sun and reveal its corona alone. The coincidence required is so extraordinary that I doubt that one planet out of a thousand has it. Even if planets are commonplace, this is rare and beautiful. If there are aliens travelling our cosmos, then a solar eclipse may be the best place to find them: it's something you might come a long way to see. « Ça vaut le voyage, » as the Michelin guide says.)

    h/t +Ahmed Amer.
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  • Yonatan Zunger2012-08-01 19:25:36
    Yesterday +Michelle May shared this quote, and I think it's worth talking about. Something I like about this is that it's a meaningful argument from both a theistic and an atheistic perspective. It directly wrestles with the question Euthypro asked: is something good because God loves it (well, the Gods, this is from Plato's dialogues) or does God love it because it is good? If the former, then "good" is completely arbitrary and defined as "whatever the gods happen to like;" if the latter, then divine goodness is arbitrary, rather than a fundamental property of the gods. 

    Marcus Aurelius takes the second approach without hesitating. If the gods exist and are good, then they will like you because you have been a good person. If the gods' opinion of you depends on something other than whether you're a good person, then the gods aren't that great and you shouldn't give a damn what they think. And if the gods don't exist at all, then none of that matters, but being good is its own reward.

    Plato and Marcus Aurelius were both discussing this in a much older religious context. In more modern contexts, the Christian approach -- that God is intrinsically good, and ought to be worshiped -- dominates the conversation so much that we often forget that there are other ways to talk about this.

    Judaism deals with this in a very different way. For one thing, there are many different views of the afterlife in Judaism, no particular consensus on it, and it's not considered particularly central to the religion. Rather, moral behavior and having a close relationship to God are seen as two independent ends in their own right. You want to be a good person for basically the reason Marcus Aurelius says; and you want to be close to God because being close to God is awesome in its own right. It still runs up against Euthypro's dilemma, but at least in this case, the dilemma doesn't affect your individual behavior as much: you want to be good because that's the right thing to do. If God doesn't want you to be good, for some reason, then there are going to be some serious problems here, but the choice is clear: be good yourself.

    Part of the way that this manifests is that in Judaism, the divine hand in human morality primarily takes the form of perpetually encouraging humans to make laws, establish codes of behavior, and debate and improve them at length. The suggestion that God, or God's chosen, is automatically good doesn't actually get a very strong basis; to take an obvious example, David, the Messianic king, is an utter dick and behaves in obviously shady ways (e.g. involving Batsheba and her husband). He even gets some divine ass-kicking for it. And sometimes God is a dick, too; how many times does Abraham, or Moses, or someone else, have to talk God out of killing a bunch of people? And they don't even always succeed at it. 

    I think that there's a powerful lesson in this: that even God is not always right. The powerful are not good by virtue of their power, and it is expected and anticipated that we maintain our own moral compasses, and speak truth to power when it is needed. 

    (I can also give a much more technical theological answer and explanation for this, but I'll save all of your sanity unless someone really wants to argue deep questions of Judaism)

    This problem is simply harder in Christianity. Here you have God who is manifest in the world, and who judges people based on their conduct in life, with extremely serious consequences. Christianity doesn't distinguish between the ends of moral behavior and of closeness to what God wants; in general, it tends to prefer the latter. That brings Euthypro's question right to the forefront, and it now dictates how you should act. Most people largely fudge this question by assuming that the two do, in fact, line up pretty closely; but this tends to fail when, e.g., preachers start preaching hate from the pulpits. At this point, there are two basic things you can do: tacitly assume an independent moral standard, and that these preachers are wrong, or align with the preachers and justify hate as good. I would say that the split between people who do the first and the second is basically the split between people I do and don't want to spend any time around.

    I'm not as familiar with approaches to this in Islam. I get the sense that the approach is largely more similar to the Jewish one -- not surprising, as they developed side-by-side for millennia -- but does someone with more experience in this have something to add?
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  • Yonatan Zunger2012-09-06 05:01:30
    Bill Clinton gave one of the best speeches I've heard in a decade tonight. I know that a lot of you are expecting me to give a deep analysis, but I'm kind of wiped right now, so just some quick thoughts:

    He clearly outlined the difference between the two parties, especially on economic matters. Gave a picture of two competing visions, and argued for why he thinks one is better than the other. He called out specifics about what each party has done, both in and out of power, and about what Obama did in particular. And he managed to do this in a speech that was rousing and passionate without being condescending, electrifying without pandering to the audience's basest instincts – something I've seen way too often in speeches lately.

    But what was really important to me about this speech was its deeply positive message. This wasn't, all told, an attack speech of the sort we're used to hearing at conventions: it was a speech about a vision for where we have been and where we can be in the future. It convinced me that there was a real plan here, and that if we get together and pull on this plan, we can make our country a better place than it is today.

    And that's not something I get from a politician every day.

    Go watch this speech. Not as a campaign speech, go watch it to hear where our country could be if we pull together. It's that good a speech.

    (And BTW, don't bother looking for transcripts as-prepared; he went very far off-script and seems to have ad-libbed half of it)
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  • Yonatan Zunger2013-05-08 15:24:03
    How the price of paint is set in the hearts of dying stars

    Today I’m going to try to explain the real reason that barns are painted red: nuclear fusion. And yes, this is an excuse to take a mad ride around some of the stranger corners of physics and chemistry in order to give you the real, this-is-not-BS, answer to a simple question.

    This question got stuck in my head as a result of an episode of a long-forgotten sitcom called Head of the Class, about a high school class full of smart kids. (Sort of like Welcome Back, Kotter in reverse) This being an American show, it’s obligatory to occasionally emphasize the superiority of the ordinary virtue of “plain folk,” so in one episode the protagonists face off in some kind of academic contest with kids from a rural school, and end up losing because their city-slicker knowledge can’t answer the question “why are barns red?” (And this episode appears to have annoyed me enough that, several decades later when I have only the haziest memory of the show’s existence, I still remember it) The answer the show gives is “because red paint is cheaper,” which is absolutely true, but it doesn’t really tell you why red paint is cheaper. It clearly isn’t because the Central Committee for the Pricing of Paints has decreed that red shall be in vogue this century, or because of the secret Communist sympathies of early American farmers. In fact, to answer this we have to go all the way to the formation of matter itself.

    Paints & Pigments & The Sun

    First of all, let’s think about what paint is. At a minimum, paint is a combination of a binder (some material that dries to form a film, like acrylic or oil) and a pigment, some material which gives it a color. A pigment is a material which absorbs some colors of light and reflects others; most pigments are minerals. (There are also organic pigments, such as the Imperial Tyrian purple made from the snot of the Murex snail, but not as many, and they tend to be much more expensive for the simple reason that there are a lot more rocks than there are animals and plants.) So for something to be a cheap pigment, it has to be a good pigment, and it has to be cheap. So let’s figure out what makes each of these happen.

    To be a good pigment, first and foremost, something has to have a nice, bright color. The way pigments produce color is that light shines on them, and they absorb some, but not all, of the colors of light. (Remember that white light is a mixture of many colors of light) For example, red ochre, a.k.a. hematite, a.k.a. anhydrous iron oxide (Fe2O3), absorbs yellow, green and blue light, so the light that reflects off of it is reddish-orange. (This happens to be the pigment that’s used in barn paint, so we’re going to come back to it.) Light is absorbed when a photon (a particle of light) strikes an electron in the pigment and is absorbed, transferring its energy to the electron. But quantum mechanics tells us that an electron can’t absorb just any amount of energy: the particular energies (and therefore colors) that it can absorb depend on the layout of the electrons in the material, which in turn depends on its chemistry.

    The detailed calculations, or even the not-so-detailed calculations, are way beyond the scope of this post. (There are even whole books about it, like Nassau’s The Physics and Chemistry of Color) But there’s one important pattern which I can at least tell you about, which is that if you look at the various atoms which form a pigment, and you look at their outermost electrons (not the inner electrons, which are so tightly bound to their atom that they don’t participate in chemistry; all of chemistry is determined by the behavior of the outermost electrons around an atom) then it turns out that certain kinds of outermost electrons form pigments, and certain ones don’t.

    The magic property is what’s called “angular momentum,” which basically measures how fast these outermost electrons are rotating around the nucleus. Electrons in atoms get angular momentum only in fixed increments (there’s that quantum mechanics again, only fixed increments allowed) and for historical reasons, the first few increments are named “s,” “p,” “d,” and “f.” On the periodic table, (http://www.webelements.com/) the elements whose outer electrons are “s” form the two tall leftmost columns; the “p” elements are the big square on the right; the “d” elements are the big block in the middle; and the “f” elements are the two rows off at the bottom. (If we ever make element 121, it would be the first “g” element) 

    Electrons with less angular momentum spin in more spherical (rather than deformed) orbits, and when multiple electrons are trying to fly in the same spherical orbit, they repel each other pretty strongly. The result of this is that two “s” electrons meeting will have very different energies -- and it turns out that, in quantum mechanics, the amount of energy an electron can absorb is exactly the difference between these energy levels. So “s” means a big gap, “p” a slightly smaller one, and so on. And it turns out that “d” electrons are right at the sweet spot where that gap corresponds to visible light. 

    Well, why are those particular colors of light visible? It’s because of the temperature of the Sun: our eyes didn’t evolve to see X-rays because there aren’t many X-rays to see around here. Instead, they’re very sensitive in the range of colors that the Sun produces, from red (around 780nm wavelength) to a peak brightness of yellow (around 600nm) all the way up to violet (around 400nm). Those colors correspond to energy gaps of about 0.3 electron volts (eV, a good unit of energy for studying atoms) which are right around the energies of chemical bonds involving d electrons. S- and p- bonds involve energies of 1-3 eV, corresponding to wavelengths around 100nm, in the far ultraviolet range.

    Did we just get lucky that the Sun is yellow, and if we lived orbiting another star might the useful pigments come from p bonds? Surprisingly, the answer is no. The Sun’s color comes pretty directly from its temperature: it’s literally glowing yellow-hot, with a surface temperature of about 5,800K. The coolest stars, red dwarfs, are about 2,800K and glow red. The hottest stars, the type O stars, go up to about 40,000K, only 72nm; but it turns out that when a star gets any hotter than class F (about 7,000K, about 400nm -- blue) its lifespan starts to decrease precipitously. This is because the temperature of stars is actually fixed by the kinds of fusion reaction going on in their core, which I’ll get back to in a moment, and those hotter reactions burn through their fuel a lot faster. The net result is that any star that’s going to last long enough to have planets with life on them might be a bit redder or a bit bluer than our sun, but not radically so: and it’s those d-orbitals that are going to make the best pigments for anyone whose eyeballs evolved there.

    How the price of iron is determined in the centers of stars

    So now we know what makes a good pigment. What makes a cheap pigment? Obviously, that it’s plentiful. The red pigment that makes cheap paint is red ochre, which is just iron and oxygen. These are incredibly plentiful: the Earth’s crust is 6% iron and 30% oxygen. Oxygen is plentiful and affects the color of compounds it’s in by shaping them, but the real color is determined by the d-electrons of whatever attaches to it: red from iron, blues and greens from copper, a beautiful deep blue from cobalt, and so on.

    So if we know that good pigments will all come from elements in that big d-block in the middle, the real question is, why is one of these elements, iron, so much more common than all of the others? Why isn’t our world made mostly of, say, copper, or vanadium?

    The answer, again, is nuclear fusion. 

    To explain this, we need to think about how fusion actually works. The basic principle is that two small atomic nuclei combine to form a bigger nucleus. Now, there are two forces at work here: there’s an electromagnetic force, which makes the positively-charged nuclei repel each other, and repel each other more and more as they get closer. And there’s the strong nuclear force, which is what holds nuclei together: it’s powerfully attractive, much stronger than the electromagnetic force, but it has the interesting property that it simply shuts off at distances of much more than about 1fm. (10^-15m, the size of a medium nucleus) So to make fusion happen, you need to somehow push two nuclei together with enough force (generally in the form of heat and pressure) to overcome their repulsion until they get within range of the strong force, at which point it will yoink them together with spectacular force and release a good deal of energy in the process.

    This gives us two rules of thumb. As the nuclei involved get bigger, the amount of energy (heat and pressure, in particular) required to set fusion off gets higher, because you have more repulsion that you have to overcome before fusion can start. And second, as the nuclei get bigger, the amount of energy you get back from the fusion gets smaller: in the bigger nucleus that you would form, you still have all of this repulsion, but the strong force can only bind together the nucleons that are close to each other, so as the nucleus gets bigger you keep adding repulsion but you don’t keep adding attraction. 

    This means that fusion of really small elements is very efficient; combining two hydrogen atoms is just great. (For various technical reasons, the slightly heavier isotopes of Hydrogen -- deuterium (a proton with a neutron) and tritium (a proton with two neutrons) do better than bare protons. That’s where the “D-T” of D-T fusion comes from, and it’s the kind that powers both the Sun and H-bombs.)

    In fact, once the atoms get too big, you no longer get back any net energy from fusion: the last reactions which turn out to be net-positive are the ones that form atoms with 56 total neutrons and protons in them. Beyond that, fusion starts consuming more energy than it produces, and won’t light up anything. (If you go far enough beyond that, to 232 nucleons or more, you start to see nuclei that are so unstable that a swift kick will make them separate enough that repulsion takes over, and they explode with a bang: that’s nuclear fission, a subject for another time)

    Now imagine a star. It starts out its life as a giant ball of primordial hydrogen from the formation of the universe, and under the tremendous pressure of gravity, it starts to fuse. As it fuses, it starts to form heavier elements like helium: but (rule 1) it takes higher temperatures than these mere hydrogen fusion temperatures to make helium do any fusing, so the Helium basically acts as a pollutant and just gums up the works. Ultimately, it reduces the efficiency of fusion so much that power levels start to go down.

    But the only thing holding the star up was the energy of the fusion reactions, so as power levels go down, the star starts to shrink. And as it shrinks, the pressure goes up, and the temperature goes up, until suddenly it hits a temperature where a new reaction can get started. These new reactions give it a big burst of energy, but start to form heavier elements still, and so the cycle gradually repeats, with the star reacting further and further up the periodic table, producing more and more heavy elements as it goes.

    Until it hits 56. At that point, the reactions simply stop producing energy at all; the star shuts down and collapses without stopping. This collapse raises the pressure even more, and sets off various nuclear reactions which will produce even heavier elements, but they don’t produce any energy: just stuff. These reactions only happen briefly, for a few centuries (or for some reactions, just a few hours!) while the star is collapsing, so they don’t produce very much stuff that’s heavier than 56. 

    If the star is small, it will end up as a slowly-cooling cinder, or as a white dwarf. But if it’s big enough, then this collapse will send shock waves through the body of the star which bounce off the star’s core, pushing the collapsing wall of matter outward with more than enough energy to escape its gravity: the star explodes in a supernova, carrying off a good ⅓ of its total mass, and seeding the rest of the universe with elements heavier than the simple hydrogen we started with. Those elements, in turn, will join the mix for the next generation of stars, as well as the accretion clouds of stuff around them which turns into clumps rather than falling into those stars: that is, the planets. And this is how all of the chemical elements in the universe were formed.

    How do we know that this is really where the elements came from? There’s a whole field of science around this, but the classic paper is commonly known as “B2FH” for its authors -- Burbidge, Burbidge, Fowler, and Hoyle. Using only the physics and the computational resources available to them in 1957, they calculated all of the various processes by which elements would be formed in stars, in enough detail to predict the ratios of elements which would be formed, and to predict the abundance ratios of chemical elements in our solar system. Amazingly enough, they made a pretty damned good and thorough prediction, enough that even then it was clear that this was a smoking gun -- and it’s been refined considerably since. 

    So how does this tie in to red paint? Well, I told you before that the magic cutoff for ordinary fusion is at 56 nucleons. Because it’s the last point in the normal reaction chain, a lot of the fusion products tend to “build up” there before the star explodes, and so you get a lot more of isotope 56 than you do of anything except for the really light elements that didn’t fuse at all, or didn’t fuse much. (Check out the first figure in the B2FH paper, linked below) And what has 56 nucleons in it and is stable? A mixture of 26 protons and 30 neutrons -- that is, iron.

    So it’s because of the details of nuclear fusion -- the particular size at which nuclei stop producing energy -- that iron is the most common element heavier than neon. And as we saw before, you have to be a d-block element to make a decent pigment, which means that iron is going to be, by far, the most plentiful pigment for any species which lives on a star that isn’t about to blow up. And it’s going to bond to oxygen, the most plentiful thing around in planetary crusts for it to bond to (only hydrogen and helium are more common, and they tend to evaporate), to form iron oxides: those rich, red ochres that we mix with oils to form a cheap, stable, red paint.

    And that’s why barns are painted red.


    To learn more:
    Something a lot more interesting than you would guess: http://en.wikipedia.org/wiki/Paint
    http://en.wikipedia.org/wiki/Pigment
    The color of the Sun: http://en.wikipedia.org/wiki/Sunlight
    Colors of stars, and a place to start about how they get them: http://en.wikipedia.org/wiki/Main_sequence
    The abundance of elements in the universe, the Earth, the human body, and other places:
    http://en.wikipedia.org/wiki/Abundance_of_the_chemical_elements
    A nice diagram of how much energy you get from fusion and fission for various elements, thanks to +Jas Stronghttp://hyperphysics.phy-astr.gsu.edu/hbase/nucene/imgnuk/bcurv.gif
    The 1980’s sitcom that inspired this: http://www.imdb.com/title/tt0090444/

    To learn a lot more about color:
    http://www.amazon.com/Physics-Chemistry-Color-2nd/dp/0471391069
    To learn a lot more about how the elements are formed, the original B2FH paper: http://rmp.aps.org/pdf/RMP/v29/i4/p547_1

    Photo by John Christopher: http://www.flickr.com/photos/67382043@N06/6153955066/
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  • Yonatan Zunger2013-06-08 00:03:43
    I have a tremendous number of thoughts about the various revelations about the NSA's domestic espionage programs revealed this week. But first and foremost, I wanted to share this message from +Larry Page and our Chief Legal Officer +David Drummond. Google had no involvement in the PRISM program and the first we heard of it was when Greenwald's article hit the press.

    I'm not sure what the details of this PRISM program are, but I can tell you that the only way in which Google reveals information about users are when we receive lawful, specific orders about individuals -- things like search warrants. And we continue to stand firm against any attempts to do so broadly or without genuine, individualized suspicion, and publicize the results as much as possible in our Transparency Report. Having seen much of the internals of how we do this, I can tell you that it is a point of pride, both for the company and for many of us, personally, that we stand up to governments that demand people's information. 

    I can also tell you that the suggestion that PRISM involved anything happening directly inside our datacenters surprised me a great deal; owing to the nature of my work at Google over the past decade, it would have been challenging -- not impossible, but definitely a major surprise -- if something like this could have been done without my ever hearing of it. And I can categorically state that nothing resembling the mass surveillance of individuals by governments within our systems has ever crossed my plate.

    If it had, even if I couldn't talk about it, in all likelihood I would no longer be working at Google: the fact that we do stand up for individual users' privacy and protection, for their right to have a personal life which is not ever shared with other people without their consent, even when governments come knocking at our door with guns, is one of the two most important reasons that I am at this company: the other being a chance to build systems which fundamentally change and improve the lives of billions of people by turning the abstract power of computing into something which amplifies and expands their individual, mental life.

    Whatever the NSA was doing involving the mass harvesting of information, it did not involve being on the inside of Google. And I, personally, am by now disgusted with their conduct: the national security apparatus has convinced itself and the rest of the government that the only way it can do its job is to know everything about everyone. That's not how you protect a country. We didn't fight the Cold War just so we could rebuild the Stasi ourselves.
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  • Yonatan Zunger2012-12-09 22:43:03
    I have no idea why I find this clip so amusing, but I do. Some students figured out how to have a staged rendition of silent monks singing the Halleluia chorus from Handel's Messiah. I particularly like the short one on the far right.

    h/t +Christine Bogart for the awesomeness.
  • 886 plusses - 123 comments - 549 shares | Read in G+
  • Yonatan Zunger2013-03-30 20:45:35
    Since I’ve heard that there’s some kind of religious festival going on this weekend, I thought it might be an interesting time to write something about the history of how Christianity came to have such a blend of non-Christian origins in it. There’s actually a very interesting history to this: in essence, it isn’t so much that Christianity absorbed external elements, as that through the tumult of the first six centuries CE, a bunch of European religions mixed and combined, and the Christianity we know today was the result of that -- it got its name on the label, so to speak.

    To realize how big the difference between what came out and what came in is, just pick up the Christian Bible and read through the discussions between Jesus and the Apostles. This was, originally, a Jewish reform movement, responding to the particular skews and corruptions that had shown up in the (Pharisaic) leadership, concerned with economic reform, (e.g. Luke 12) a hard shift away from ritual towards personal piety, (e.g. Matthew 15) and a serious mystical trend. (Largely cut out of the “canonical” texts, but very present in the Egyptian texts) The first radical change came with Paul, who was interested in converting outsiders -- something that the earlier “followers of the Way,” as they called themselves, had very little interest in. But if you compare even Paul’s early churches with (say) medieval Christianity, or even most modern branches, you’ll see very little in common. How did this happen?

    Let me start by setting up a few bits of history. We’re in the Classical Roman Empire, say around the year 100 CE. Rome is expanding everywhere; there’s a well-practiced routine when a new barbarian tribe is encountered. The Romans make offerings to the gods of that tribe, saying that they will build them a temple in Rome if they let this tribe be joined to the empire; then they go to war, win, and start to fold yet another tribe into the center. The erection of that temple isn’t something accidental: it’s part of what’s called the “Pax Deorum,” the peace of the gods, and what it really is is a public statement that these new people are being folded in to the society. These conquered barbarians aren’t at quite the same level as true Roman citizens, but they’re part of the Empire now, and light-years above those barbarians outside the gates. The physical mechanisms of the Empire are backed by a deep civic notion of “Romanitas;” to be a Roman is to be part of this great thing, to have a particular relationship to the outside world: we will conquer you and you will join us. And to be part of Romanitas is to have the weight of the Empire behind you.

    And then it stopped working. Hadrian makes it halfway up Britain and builds a wall; and the Romans start to realize that they’re at the logistical endpoint of where they can conquer. A climate cycle drops food production down and leads to widespread famine and disease across Europe. Worse climate cycles to the east start to push nomadic tribes further out in search of resources, and they start to hit an already-weakening Empire. Without the constant influx of resources from conquered tribes, the underlying lack of planning in the Roman economy (and system of succession) starts to show; and from about 180 to 280, the Empire essentially collapses into an infinite sequence of famines, plagues, civil wars, and barbarian incursions. The last of these wars, the War of the Seven Emperors, is ended in 287 when Diocletian personally executes his last rival, and sets up a new regime. 

    Diocletian’s empire was very different from Caesar’s in a lot of interesting ways, but the one I want to talk about today is that notion of “Romanitas.” Once, to be a Roman meant that you were ready to conquer everyone that you met; but the later Roman Empire was in no state to do such a thing. The central question of civic identity -- of what it even meant to be a part of this empire -- didn’t have a good answer, and with it, the whole question of what held the Empire together at all was up in the air as well.

    Now switch over and look at the religion of the time. If we rewind back to the year 100, the Latin word religio had a very different meaning from what we think of today: it was the set of public rituals that the society participated in. These were tremendously important in a lot of ways. First of all, they were a key economic glue. Roman society didn’t have a notion of “taxation” in the modern sense; but instead, leading citizens were expected to regularly have sacrifices to the Gods to honor their good fortune in various things. At a sacrifice, animals would be killed, their first fruits given to the Gods with various prayers, and what followed is what we would today call a “big damned barbecue.” A Roman could expect to go to a sacrifice every week or so on the average, and this was the primary access that most Romans had to meat. (So when I say “key economic glue” I mean “a major part of how the society got access to food.”) Second, they were the way in which people defined their civic nature. Today, we define our nationality in terms of things we learn in school, what we read in the papers and discuss in the media -- all things which didn’t exist in Rome. The expression of nationality was the common rituals that people went to. (And this, incidentally, is why the cult of the Emperor was so important: by sacrificing to the Emperor, you were indicating your loyalty to the Emperor and the Empire) Public actions were the main way that people communicated their thoughts.

    One thing you may notice is missing from that list is anything which resembles our modern notion of “faith.” This wasn’t an unfamiliar concept, but it wasn’t considered to be part of “religio.” People had household gods with which they had a personal relationship, and actual priests had relationships with their gods, but nobody was generally expected to have a deep and abiding religious faith in each god that showed up through the gate. But the urge for deeper religious experiences was certainly there, and ever since the time of Alexander the Great (around 300BCE) one of the main ways this manifested was in “mystery cults.”

    Mystery cults were the religious secret societies of the ancient world. You could join some of them by simply walking in the door, and for others you had to know someone, but what they all had in common was that you would be initiated, participate in secret rituals, gradually learn more and more of the secrets of this god. These cults often taught a combination of mysticism, philosophy, and theology; they offered a chance to see into the world beyond; and they offered a close confraternity among the members. And they were quite separate from “religio” proper, bearing it about the same relationship that gentlemen’s clubs in Victorian England bore to Parliament. 

    There were a few categories of mystery cult which were becoming particularly popular in the first few centuries CE. The first was the cult of Magna Mater, which was basically the worship of Isis gradually transmuted into a pan-European religion. Consider that ancient Egyptian religion was already extremely, incomprehensibly ancient: the pyramids are a great work of the late Stone Age, as much older than the Romans as the Trojan War is older than us. The knowledge of hieroglyphs had already passed out of the world, but the infinite number of mummies and inscriptions and magical practices were still very much there. Add on to this that, even thousands of years earlier, Egyptian religion had highly favored spectacular, awe-inspiring temples where people went for rituals, healing, miracles, surrounded by fire, strange smokes, talking statues -- and that this tradition was still very much alive -- and you have a great factory of religious beliefs which were immensely popular in the Roman world.

    Second was Mithraism, a religion that we still understand relatively little. Mithras was a warrior-god, of Persian origin; he has many similarities to similar warrior-gods spread across the Near East, not least the version of Yahweh worshipped in the western Levant which later became a core part of Judaism. In Rome, his worship became very popular among the army, starting with soldiers who had served in the east. The rituals were very secret, part of the brotherhood of joining the Roman Legions; underground caverns, secret dances, sacrifices, rituals that we know very little about today because they were actually fairly good at keeping their secrets, and quite deliberately didn’t write many things down. 

    The third was ascetic monasticism, something which never really caught on in Europe but which was a huge deal in Egypt for hundreds of years. There was a tradition of hermits retreating off into the desert to pray, fast, and generally mortify themselves, and these hermits were considered to be avatars of purity itself, holy, powerful, capable of great magics, and mad as a bag of clams. (As a side note, The Book of the Fathers, a book on how to be a good monk written in fragments from the 4th through 10th centuries, has lots of examples of the stories of early monks, who were basically Christian Egyptian ascetics. Something like two thirds of these stories end with either “and then he/she starved to death” or “and then he/she died in a sandstorm.” These guys were hard-core.

    And Christianity -- Paul’s Christianity, the kind that wanted to spread -- joined in to this mix. This early Pauline Christianity worshipped in secret, because it was defiantly anti-religio; this was honestly a holdover from its Jewish roots, with the Jews being rather famous for their (often violent) unwillingness to sacrifice to other gods. But it had many other familiar features: secret meetings in (literally) underground churches, intense personal faith, mystical healing, close confraternity between the followers. Unlike many of the other mystery cults, it was built fairly strongly around concepts of morality -- another holdover both from its Jewish antecedents and from Jesus’ own focus on reforming Judaism towards personal religiosity. 

    These religious traditions competed with each other pretty openly. If you read Apuleius’ The Golden Ass (arguably the first novel), you’ll see all these conflicts show up in people’s daily lives. Laws were passed banning Christians from serving in the army -- it would destroy unit cohesion, you see, and the men might feel uncomfortable. (Le plus que ça change...) And they also combined: Christianity became popular in Egypt, and people combined it with both Egyptian asceticism (to form the seeds of monasticism) and Manichaeanism, another Persian import from which Christianity got its notions of the duality of God and the Devil. The healing magics of Magna Mater stayed popular across the board, and Christians found themselves doing basically the same things. 

    (There’s a whole history here, too, of how these religions related to the earlier Roman political order.)

    And around the year 300, these religious and political trends started to come together. The political order of the old religio made less and less sense: giant, formal, public rituals to the gods of old Rome didn’t pull people together the way they once did. But the underlying needs behind them, both civic and economic, were still there. By the time of the civil war that followed Diocletian’s retirement (a very interesting story in its own right), Mithraism was in a bit of a downturn, apparently not providing quite enough mysticism relative to simple brotherhood; Christianity had folded most of the magical elements of Magna Mater into itself, and had done a better job of conversion through its strategy of focusing on women, and soldiers, many of whose mothers had been converts, started to use it as their secret brotherhood ritual. Against this background, Constantine (one of the warring emperors) made it the quasi-official religion of his army, and soon after won control of the Empire. 

    What happened here was that a religious trend of secret societies, previously illegal in many situations, which thus tended to forge close relationships among the practitioners, suddenly became an official Thing which people realized they could further their careers by converting to. Many is the Roman nobleman of this period who went to bed one night, a contented pagan, and woke up the next morning a bishop, and a few hundred thousand solidi poorer. (That was the going rate for a bishopric) But this new religious system had communal identity baked so deeply into it, and held people together well enough (after all, that’s one of the big things Constantine used it for!) that it started to become a substitute for this now-missing identity.

    Several things happened over the next hundred years which reinforced this, but perhaps the most dramatic was the sack of Rome in 410. It’s hard to express how world-shaking this was: imagine if, on 9/11, rather than destroying the Twin Towers in New York, the Taliban had simply marched in to New York City and sacked it, and the government was powerless to do anything about it. That’s roughly what happened then. And yet: the Goths who sacked Rome left the churches untouched -- they, too, were Christians. Augustine used this as the jumping-off point for his book, The City of God, which crystallized the ideas that had been building up over the years: Christianity united its believers in a sort of world-spanning empire. This notion of Christianity as a social identity, rather than as a religious faith, became the cornerstone of European society for the next thousand years.

    This answered the question of “how do we deal with those barbarians?:” If they were Christians, then you could use this common language of Christianity to establish relations with them. If they weren’t, you could convert them or kill them -- or point your own friendly barbarians their way. It also provided a new social glue for the society, so long as everyone came over and converted.

    And what you might notice is missing, again, from this picture is the modern notion of “faith.” It was important that everyone be a Christian because that was part of being part of the Empire, but the details weren’t quite as important. So the common variety of “conversion” in the Late Antique Empire went something like this:

    A priest shows up in a village. The village is generally having some kind of major problem or another, whether it be a failed local irrigation system, or a famine, or a plague. The priest calls people together in the name of his god, and fixes the problem: either by prayer, or by getting people together to fix the well, or by pulling in external resources. (Most of the time, incidentally, the priest didn’t successfully fix the problem, in which case he simply would move on to the next village and try again) On success, the village praises God and converts. They have to give up “pagan rituals” -- i.e., they have to adopt the forms of Christian religio rather than whatever they did locally. But the underlying importance of the sacrifices (economic, civic, etc) was still there, so what was important was to do them in a Christian way. Do them in a church, not a cemetery. Praise a saint rather than a god, and so forth.

    And then the priest would move on to the next town, racking this up as yet another successful conversion. But nobody was left behind in this town who actually had a particularly deep understanding of Christian doctrine; and in fact, owing to how bad travel was in the Empire at this point, it was often 100 years until the next priest would reach a particular village! So Europe “Christianized” by adopting a shared set of practices and religious language, but not a shared religious faith in the modern sense of the word. 

    The results of this weren’t fully appreciated until nearly a thousand years later, during the Counter-Reformation: in response to the rise of Protestantism, the Catholic Church started to try to root out “heresy” in its own world, and discovered (much to its shock) that the average Christian had absolutely no idea what the religion was supposed to mean. (A truly fascinating account of this can be found in The Cheese and the Worms: The Cosmos of a Sixteenth-Century Miller, which studies the record of the heresy trial of some random schmuck who was grabbed by the Inquisition. The title comes from his attempt to explain just how the world was created.) 

    So when we talk about a “Christian syncretism,” what was happening wasn’t that Christianity deliberately or accidentally took on bits of other religions. Rather, most of the conversion of Europe -- and very similarly, most of the conversion of other parts of the world later on -- happened very quickly, with groups of people agreeing to take on the structural forms of Christianity, praying to saints in churches and so on, but with very little emphasis on constructing a shared “faith” in the modern sense.

    In fact, this modern notion of faith came largely out of the Protestant reformation. The Protestants started out with a notion that people should have a direct, personal familiarity with scriptures and a much more personal relationship with God: ideas which hadn’t really entered much into the Christianity of the preceding millenium. The Catholics, in response, tried to “purify” their own faith and make sure that everyone was on the same page, using much the same techniques which they had developed for ensuring that there were no secretly practising Muslims or Jews in Spain after the Reconquista. (Yes, I know. You were expecting that the Spanish Inquisition would show up in here at some point.) Several centuries of spectacular bloodshed later, it was a commonly accepted idea in all branches of Christianity that Christianity was, first and foremost, about individual faith, and a common understanding of doctrine was what bound Christians together. But this hadn’t actually been a feature of Christianity ever since the days of Paul, and the Christianity of the 19th century is a very different beast from that in too many ways to count. It was a new thing.

    So today, when people tell you about how Christianity has “borrowed” ideas from non-Christian religions, or that this or that holiday is actually a pagan festival in disguise, your surprise isn’t coming from the fact that Christianity ever was really a common religious language rather than a unified faith: it’s coming from the fact that, over the past few hundred years, Christianity has deeply rewritten its creed, and largely forgotten its own history. These things aren’t alien to Christianity at all: they’re the deepest part of its origins.


    For more information, some places to start:
    http://en.wikipedia.org/wiki/Cybele
    http://en.wikipedia.org/wiki/Mithraic_mysteries
    http://en.wikipedia.org/wiki/Constantine_I_and_Christianity
    http://en.wikipedia.org/wiki/City_of_God_(book)

    The best sources of all on this subject are books. Peter Brown’s The Cult of the Saints or The Rise of Western Christendom give an excellent snapshot of the Late Antique transition and can get you started looking for other things. Carlo Ginzburg’s The Cheese and the Worms is a great way to see what ground-level faith in the sixteenth century looked like.

    Photo by Robobobobo: http://www.flickr.com/photos/45493477@N05/4178051127/
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  • Yonatan Zunger2012-10-06 19:53:46
    +Dirk Talamasca shared a video by this guy of Beethoven's Hammerklavier sonata, and I started digging through more of them and found this awesome visualization of Rimsky-Korsakov's Flight of the Bumblebee. I really love creative ways to visualize music, especially when it shows the relationship between different parts of the piece in ways which aren't at first obvious.
  • 913 plusses - 135 comments - 402 shares | Read in G+
  • Yonatan Zunger2013-10-17 18:12:01
    RESHARE:
    At high enough speeds, solids aren't actually that solid. The force of an impact can create waves in hard objects that are as big as the objects themselves... thus making a golf ball look like jelly.

    via +Alex Scrivener.

    Reshared text:
    Golf ball hitting a steel plate at 150mph in 70,000 fps.
  • 1010 plusses - 99 comments - 344 shares | Read in G+
  • Yonatan Zunger2014-02-06 07:38:21
    Because making the invisible visible is beautiful. And because fire.

    In almost any fire, only the topmost layer of the flammable material -- the area in direct contact with oxygen -- is actually on fire. Even there, it often isn't the body of the fuel which is burning; instead, the heat of the fire is causing a small amount of the fuel to evaporate, and it's the fuel vapor that burns.

    (That's how both wood and gasoline fires work; in their solid and liquid states, respectively, the forces holding them in place are strong enough that they suppress the burning reaction. This is why it takes a while for wood to catch fire: you're using the fire to heat the wood enough to make it give off pre-soot, and that's what actually catches fire. If there's water, it will absorb a tremendous amount of the heat energy without itself heating up (see https://plus.google.com/+YonatanZunger/posts/hhDyY4DjuLv) and thus prevent the fire from spreading. This is why water is used to put out fires.)

    There are a few exceptions, but they're unusual: things like monopropellant rocket fuels which contain both the fuel and the oxidizer inside them, thoroughly mixed, so that the entire thing can burn if ignited. But even in a normal rocket engine, it's only a small bit of the fuel that's burning at a time -- or if not, you are having a big problem and you will not go to space today.

    http://i.imgur.com/0w87emS , via +Effie Seiberg.
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  • Yonatan Zunger2014-04-01 00:14:36
    Several people have been asking me about the new "view count" number which shows up on your profile, and I've been answering on a bunch of threads, so let me give you the key answers in one place.

    What does this number count? This is total views on your profile, your posts, your photos, and your videos. 

    What constitutes a "view?" For your profile, when someone goes to view your profile page. For other things, it's when they look at it -- e.g., when one of your posts shows up on someone's screen. (That's because this is how most people read posts: showing up in a stream, without clicking on it explicitly) Looking at your hovercard doesn't count.

    Is this related to +1's, reshares, etc.? Only in that someone who +1'ed your post also probably saw it. You can already see counts for those on individual posts, etc., and before today you could see view counts for each photo if you looked carefully at the one-up view -- now you can see that for everything.

    If someone reshares my post, does that count? Yes, since a viewer is seeing your content. Ditto if someone sees your post through an "Alice +1'ed this," through a post embedded on a page, or any other way that someone encounters it.

    I don't want to show this on my profile! You can hide this by going to your settings page. Go to plus.google.com/settings and look for "Show how many times your profile and content have been viewed."

    This seems strange: Some people seem to have a lot more views relative to their number of followers than others. Is something broken? Not at all. Some people have a lot of followers but don't engage with them well, while other people engage amazingly with a smaller group. 

    I want to find out more. Check out the Help Center article at http://goo.gl/8BjroH .
  • 528 plusses - 273 comments - 528 shares | Read in G+
  • Yonatan Zunger2011-08-05 07:00:20
    [Resharing as public]

    Something awesome. I understand our financial markets so much better, now that I realize that the trading desks are actually manned by infants with access to e-trade.
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  • Yonatan Zunger2013-04-13 19:43:59
    I want to tell you a very unpleasant truth about climate change. It's a lot more serious than we've been discussing in public.

    (Warning the first: This is not going to be a cheerful sort of post. It will, very likely, leave you feeling deeply unsettled. If you do not want this, you should stop reading now.)

    (Warning the second: This is not a post on which to say "I don't believe climate change is happening!" or "this is a left-wing plot!" or "I don't believe there's adequate proof that humans are causing it!" There are times that I have the patience and interest to discuss what are essentially political arguments about science, and this is not one of them. If you believe this stuff, it's because you have a deep personal need to do so, and best of luck to you with that. But I'll just delete such comments on this post.)

    The paper referenced here is one that +Larry Smarr shared. We have a new paper running several parallel models of Arctic ice collapse, and the one thing that even the most conservative models agree on is that the Arctic will be ice-free in summer within the next 20 years. This is pretty much right; anyone who's been watching the development of climate indicia and thinking about the positive feedback loops in ice melting has known it for a while.

    But we don't really talk about positive feedback loops, much, and when we do, we stop soon afterwards because it's a bit too horrifying to think about. But climate systems are full of them; ice melting is a simple example. If you have a big sheet of ice, it reflects sunlight and stays cool. But if it melts, the top of it melts first, and then you have a puddle of water, which is great at storing heat and doesn't reflect as much sunlight, sitting on top of your ice. That puddle gets warmer, and melts the ice under it much faster than pure light would; lather, rinse, repeat, and ice melts fast. (You can test this out in your own backyard; take two pieces of ice and put them in the sun. If you keep draining the water from the top of one as it melts, it will melt much more slowly than the other one)

    The best way to know that climate systems are a big hornking bag of positive feedback loops is to look at the Earth's climate record. (We can get this quite nicely from things like deep ice cores, tree cores, etc.) You can see a good summary graph here: http://www.scotese.com/climate.htm. What's distinctive are those sudden vertical spikes; these represent times when the climate suddenly and rapidly became a lot hotter, on time scales much shorter than any other variation. That sort of thing can only happen when you get a massive external driving force (think "giant comet") or a positive feedback loop.

    What's important to understand about this is that, when you hit a loop like this, the consequences aren't measured in the ways that IPCC climate models talk, about so many degrees rise in mean temperatures, changes in the biomes of infectious diseases, crop failures, sea level rises making cities into ruins, giant storms wiping cities off the map. They change the entire ecosystem of the Earth -- the basic kinds of plants and animals which can live on it.

    The last big spike like this was the Paleocene-Eocene Thermal Maximum, about 55 million years ago. Average temperatures rose by 6C over a period of 20,000 years -- which is enough to look like a giant, sharp spike on the history-of-the-entire-planet graph. During the PETM, the Earth looked like the inside of a giant greenhouse; hot, wet, tropical. Swamp cypress grew as far north as Ellesmere Island, the northernmost part of Canada. The large mammals of the Paleocene vanished, to be replaced by a huge variety of new species, mostly dwarf-sized. Many of our modern kinds of creature -- birds, ungulates, etc -- emerged in this period. Life before the PETM favored much bigger critters, like a snake the size of a school bus. (See below for a link)

    As far as climate swings on the Earth, this one wasn't close to the biggest, although it was one of the fastest: the temperature rose by 0.0003C per year, enough to completely reset the biota of the planet. 

    By comparison, since 1920, the mean temperature has been rising an average of 0.01C per year. Yes, that's about 30 times faster than the run-up to the PETM.

    Some things you need to understand about these shifts.

    * They've happened quite a few times. Look at that first graph I linked, and read about any of the times the climate changed sharply. Each of these was associated with a complete rewriting of the planet's biota -- which is a nice way of saying "almost all the life died out and was replaced by something completely different."

    * Because of positive feedback loops, when a climate shift starts, it can speed itself up. There are a lot of different loops, ranging from ice melting to methane clathrates to ocean circulation pattern changes. Unfortunately, we don't understand these loops very well -- because if any of them had gone off full-force while we were around to study them, we wouldn't be around to study them. Because of loops like that, once something gets started it's not always possible to shut it off by reversing what you're doing, no matter how much you do so.

    * When the biota of a planet get rewritten, the creatures that require the most delicate maintenance die first. This tends to mean really big creatures, that rely on large supplies of their foods; apex predators, which rely on the entire food chain beneath them; and "canary" species like many frogs, which are very sensitive and tend to be the first to die when something is going wrong. Historically, the cutoff for "large creatures" (that tend to not survive extinction events) seems to be in the ballpark of 20 pounds; things bigger than that just require the ecosystem to be too healthy.

    So, yes, that includes you, it includes your dog, it includes most of the animals you eat. It probably also includes lots of the grains you eat, since large-scale agriculture is quite fragile as well. (As evidenced by the tremendous amount of work put in every year to keep crop yields high enough to feed humanity) 

    * Technological methods of helping are actually more limited than you think, because so much of our technology stack is built on top of society being basically functional. Manufacturing microchips requires pretty much the full scope of human industry, from mining to power generation to transport logistics to chemical engineering. Growing the quantities of plants required to support humanity is, if anything, even more delicate. We're fairly robust against small perturbations because we can put in technological solutions -- but when problems start to knock out the basic infrastructure on which we can depend, the descent and collapse is fairly rapid.


    Now, you may think that I'm writing this to make a political point, or to urge you to do something or other. Sometimes I would be, but this time I'm not: I'm just writing to show you a bit about the science, and give you an idea of just what the situation we're talking about could potentially entail. It's not clear where we are on the positive-feedback loop right now; it's very likely, for example, that the Arctic ice will collapse at this point, no matter what we do in the next 20 years. Whether we've gone far enough to trigger other catastrophes is still up in the air. 

    But if it is, what we're looking at isn't a world where we all live like Bangladeshis, or a world where we're living in technological bubbles. It's a world where there are tropical rainforests going up to the poles, where there are millions of new and unfamiliar species... and we're simply dead.


    If you want to know more about the history, here are some places to start:
    http://en.wikipedia.org/wiki/Paleocene-Eocene_Thermal_Maximum
    Life in the Eocene: http://en.wikipedia.org/wiki/Eocene
    Temperature change in the 20th century: http://en.wikipedia.org/wiki/Temperature_record
    Titanoboa, and other giant creatures of the Paleocene: http://www.smithsonianchannel.com/site/sn/show.do?show=140671
    One of the kinds of positive feedback loop that could be a problem for us: http://en.wikipedia.org/wiki/Clathrate_gun_hypothesis
  • 610 plusses - 423 comments - 301 shares | Read in G+
  • Yonatan Zunger2011-06-29 00:05:56
    Some useful-but-maybe-not-obvious features of Google+:

    * In your stream, "Incoming" means "other people who are sharing with me" -- people who aren't yet in your circles. You can browse through it to see people who have added you.

    * "Notifications" gives you the same sort of stuff that you can see in the notifications menu in the top right. (The one that turns bright red when you have an update -- not yet available in all countries) Who's added you, when you've been mentioned in a post or tagged in a photo, etc. Also, that menu at the top? Very useful.

    * "Sparks" lets you get cool content relevant to your interests. Random side note: While debugging the system, we often used "Chocolate Cake" as a test interest. It turned out to be a really distracting interest.

    * Hangouts are more awesome than you may suspect, because they require so little work.

    * You have to click on the "Chat with people on Google+" link to enable chat within Google+ (long story as to why), but then you get IM functionality.

    * The mobile app has two features of surpassing awesomeness: Huddles and Instant Upload. Huddles are everything that messaging was supposed to be but never was -- group of people, persistent conversations so you can keep chatting with people, a hell of a lot faster delivery than SMS, etc. Instant upload means that you will never have photos stranded on your phone again.

    * The delete circle animation is enough fun that one is tempted to create circles and delete them just for the heck of it. Andy Hertzfeld FTW.

    I'll probably think of more of these later... there are a lot of features in here, and there are even more on the way. This is called "The Google+ Project" for a reason; the future is bright and exciting.
  • 38 plusses - 21 comments - 821 shares | Read in G+
  • Yonatan Zunger2012-04-22 23:55:54
    Isn't this what a capella is really for? Playing the Mario Bros. theme?

    h/t +David Nachum for the link.
  • 713 plusses - 131 comments - 352 shares | Read in G+
  • Yonatan Zunger2012-08-28 18:10:33
    I suppose that, in a way, this is refreshingly honest: Romney's senior campaign staff seems to be publicly and openly saying that they will, in fact, be lying about Obama and his policies in their campaign ads, and they don't see anything wrong with that.

    I don't really know what to say about that.

    via +Tammy McLeod.

    Edited to add: Do not read the comment thread below unless you want to lose faith in the American political process. ::facepalm::
  • 668 plusses - 426 comments - 227 shares | Read in G+
  • Yonatan Zunger2013-03-14 18:02:28
    I have a question for avid Google Reader users: what are the aspects of the way Reader works that made it so useful for you? I've heard a number of things floated in the past day -- e.g., the particular sources available, the way of managing read/unread state, various aspects of the UI -- but I'd like to understand better what the concrete things about Reader were which people found the most useful, because I'd like to integrate those ideas into future versions of many Google products, and try to capture that value.

    (NB: If you're seeing this via a reshare, please remember to comment on the original post if you want me to see what you're saying!)

    Warning: This is not a thread to simply complain about the shutdown, or to ask Google to keep Reader. That's not something that I can help you with, nor is it a decision that I had anything to do with, and this is not a good place to get anyone's attention about that. This thread is a place to talk about specific things which are useful about it so that we can think about good ways to capture that usefulness in the modern world.

    Comments which disregard the previous paragraph will simply be deleted. Comments complaining about my deleting those comments will result in me blocking and/or mercilessly mocking you for failing to read instructions. Comments complaining about that will lead to some interesting replies in a combination of languages, probably starting with Yiddish and moving on from there. Comments interested in the Yiddish language should instead go on my post from last night. (http://goo.gl/xxn7h, but I should say that I'm not an expert or a fluent speaker of the language)

    NB: The comments have filled up! Please check out my comment at the end of the post.
  • 473 plusses - 495 comments - 268 shares | Read in G+
  • Yonatan Zunger2012-09-26 02:37:53
    A few things I have learned while posting on Google+:

    If you post about science, cars going fast, interesting animals, or the like, lots of people will enjoy it, especially if it comes with a video. If you post a cool photograph of a person or place, people will enjoy it but will +1 more than they comment. If you post inspirational quotes, people seem to like that a lot, but the comments get a lot more incoherent.

    If you post about religion, people will be surprisingly civil even if you say something controversial, and they'll want to talk about it a lot, especially if they disagree. However, at least one commenter out of 20 will feel strongly that if you mention religion and don't say anything contemptuous about it, you are wrong and must be corrected. Most people will ignore this commenter.

    If you post about politics, especially if there is an election coming, everyone will get extremely excited and will soon be not at all civil. 

    The most effective way to troll a conversation appears to be to utter the words "Romney" or "Obama." Doesn't really matter which.

    If you post about law, economics, or any bit of politics which isn't related to a current election, at least one commenter will feel strongly that all these problems are just symptoms of the evils of the existence of government, and that we must replace all laws with voluntary contracts.

    If you post about art, music, or something else you personally think is cool, you will likely discover that someone else you know also thinks it's cool, even though you wouldn't have guessed that about them.

    If your post has a photo on it, people will look at it more. It doesn't matter if the photo is relevant. This photo is of some stuff on my desk.

    What have you learned?
  • 729 plusses - 267 comments - 187 shares | Read in G+
  • Yonatan Zunger2013-02-24 03:22:05
    This is not what you think it is.
    This is kind of disturbing.
    This is sort of like Microsoft meets Charles Stross meets Aleister Crowley.

    I blame +Rob Bush.
  • 761 plusses - 122 comments - 217 shares | Read in G+
  • Yonatan Zunger2012-10-25 04:12:16
    Do you have an election plan?

    If you are a U.S. Citizen, then there's an election coming up in just under two weeks – on Tuesday, November 6. Now, I bet that some of you are saying that you aren't sure if you're going to vote – aren't the candidates all the same? Is any of this stuff really going to make a difference?

    If you're wondering about this, I found that there's a simple thing you can do to check if you really should vote or not. I'll bet that no matter how little you watch the news, there's some issue that's guaranteed to bring out the people who tick you off. The sort of issue that's the exact reason why you don't listen to the news. I want you to do something unusual for me.

    Go open another tab in your browser, and go to your favorite social network or search engine. Now go do a search for something about that topic, the sort of search that will bring up people's opinions. Maybe that's as simple as searching for "Obama" or "Romney" or "socialism" or "abortion." But go over there, and check to see if you can find one spectacular jerk out there, saying the sort of thing that makes you lose all faith in humanity.

    That jerk? He or she cares a lot about the issue. In fact, that person almost certainly cares enough to vote, and come November 6th, that jackass is going to be out there at a ballot box. I'll bet you can guess how they're going to vote on at least one issue.

    So here's the special prize I'm offering you: Pick that one jackass, and save a link to their post. Now on November 6th, if you go out and vote, you can cancel out that jackass' vote. You don't have to vote for anything; you can just go to the polls, and make sure that this particular jackass' vote ends up not counting. And if you feel like it, on the afternoon of November 6th, you can even go back to that post and let them know what you did. Or you can just hold that fact in your heart, that you managed to undo all of this person's efforts to vote some utter lunatic into office.

    Doesn't that feel good?

    But OK, maybe you've decided to vote. Have you got a plan? Do you know what you're going to do that day, or maybe a few days in advance if you can do early voting, or vote absentee?

    Here's my plan: My polling place is at St. Timothy's Church in Mountain View, at the corner of Grant and Sleeper. (It's on the sample ballot my state sent me) I'm planning on getting up 15 minutes early that day, driving down to the polling place before work to vote, and then stopping off for a cup of coffee on the way in to work.

    What's your plan? Are you going to vote absentee, vote early, vote on the day itself? Do you know how you're going to get to the polls? Do you need help getting there? (If you call up the campaign office of one of the candidates, they'll often help you get a ride if you need one!)

    Remember: You're not just voting. You're making sure that at least one jackass out there fails at being a jackass, for one important day. Isn't that worth it?

    Also: If you want to check your local election information, or get summaries of the things that are going to be on your ballot, try smartvoter.org. It's a nonpartisan site that gives you pointers to local election info.
  • 637 plusses - 290 comments - 179 shares | Read in G+
  • Yonatan Zunger2012-02-19 01:36:19
    Because recursive dogs are cool.

    h/t +Noritoshi Takeuchi for the pic.
  • 647 plusses - 126 comments - 221 shares | Read in G+
  • Yonatan Zunger2014-01-18 21:03:37
    RESHARE:
    And here, for no particular reason, is a clouded leopard cub curled up in its trainer's lap. Because not all posts need to be serious.

    via +mary Zeman.

    Reshared text:
    An eight-month-old clouded leopard cub named Ganda at the San Diego Zoo curls up in her trainer’s lap even though she's getting to big for it.
    Photo: Deric Wagner
    http://goo.gl/v40xF7
  • 884 plusses - 64 comments - 100 shares | Read in G+
  • Yonatan Zunger2012-06-29 17:53:45
    This is pretty fascinating, even though it's not something I'd normally watch -- this guy bought an engine for his Triumph Spitfire on eBay, stripped it down to its parts and rebuilt it. In this movie, you get to watch an engine disassemble and reassemble itself as if by magic. It's sort of hypnotic...

    via +Jennifer Ouellette.
  • 549 plusses - 67 comments - 286 shares | Read in G+
  • Yonatan Zunger2012-07-12 06:07:40
    Something awesome, via +Adam Lasnik – a Hong Kong architect's 344 sq ft apartment, made amazingly pleasant and livable by turning into a massive sort of transformer.
  • 540 plusses - 74 comments - 273 shares | Read in G+
  • Yonatan Zunger2013-06-29 07:16:56
    This video is definitely worth five minutes of your time. Steve Mould does something really simple -- takes a really long beaded chain in a beaker, and drops the chain over the side. And what happens is pretty magical, so he films it in slow motion and explains, very clearly, why it happens.

    What are you seeing here? Part of it is simply gravity: the weight of the chain that's hanging over the side is pulling the rest of the chain over. Part of it is waves in the motion of the chain. Part of it is the fact that the chain can't change direction infinitely quickly. And all of it will, as io9 puts it (http://io9.com/this-is-the-bead-chain-experiment-its-about-to-melt-y-602029455), melt your brain.

    via +Jennifer Ouellette, who finds the coolest damned stuff on the Internet. If you're not following her, you should be.
  • 363 plusses - 52 comments - 384 shares | Read in G+
  • Yonatan Zunger2013-10-15 15:40:11
    RESHARE:
    Now here's a great shot. I posted a few months ago about max-Q, and how rockets fly up to about 26,000' and then turn East (instead of up) in order to get to space -- and now +Chris Hadfield provides an amazing photograph of exactly that, at sunset. 

    Original article here: https://plus.google.com/+YonatanZunger/posts/VsYyUDxFUDr

    Reshared text:
    Good morning! Perspective: first you have to get above the air - then your ship can go fast enough to stay in orbit.
  • 715 plusses - 48 comments - 95 shares | Read in G+
  • Yonatan Zunger2013-04-18 16:11:55
    I'm excited to announce something else we've been working on: Google+ Comments, launching today on Blogger. This provides you with some features that you won't have seen in other commenting systems; my own favorite is that it brings the conversation from G+ into your blog, so that the social media conversation doesn't get segregated from the comment thread.

    This is a purely opt-in launch for blog owners: if you have a blog and want to try it out, follow the instructions in this post. We'll be rolling it out over the course of today!
  • 377 plusses - 179 comments - 241 shares | Read in G+
  • Yonatan Zunger2011-06-30 21:17:27
    More useful-but-maybe-not-obvious features of Google+

    * If you want to send a private message to someone, just create a normal post and share it only with them. Bam! Instant one-on-one conversation! If you want to make a post publicly visible but aim it specifically at someone, share it with them and also with Public (or also with your circles, etc).

    * Speaking of sharing only with someone: If you type +<name> or @<name>, it shares the post directly with them, just like if you added their name in the sharing targets. You can also do this in a comment, to pull someone else into the conversation.

    * Want to see who can see a post? Next to the dateline at the top of a post, you’ll see something like “Public” or “Limited.” “Limited” is a link -- click on it to see who has access.

    * At the top right of each post, there’s a little circle-and-triangle menu. For your own posts, this menu lets you edit or delete the post, or disable commenting or resharing. For other people’s posts, it lets you link to the post, mute it, block the person completely, or report abuse.
  • 88 plusses - 51 comments - 469 shares | Read in G+
  • Yonatan Zunger2014-03-30 21:17:58
    With recent outbreaks of measles, pertussis, and even polio across the United States, I think it's time to revisit our laws about vaccination.

    Refusing to vaccinate your children doesn't simply put them at risk: it puts at risk everyone who, for medical reasons -- extreme youth, old age, health, allergy -- can't be vaccinated, as well as everyone whose vaccinations have lost potency over time. Personal objections to vaccination, whether it be because of (unsubstantiated) fears of side effects or religious reasons, put everyone around you at risk of death or serious injury. This is a classic case where your right to swing your fists around ends at my nose: the individual liberty interest in allowing people to decide which medical procedures to undertake is outweighed by the safety and survival interest of those around you.

    I believe that it is time to end all non-medical exemptions from critical vaccination requirements such as MMR, DTaP, and polio --  for epidemic diseases which kill and maim by the thousands when our immunity, as a population, is compromised. 

    My preference would be to treat this as a criminal matter: to fail to do this amounts to reckless endangerment. (Public endangerment, that is, not simply endangerment of a minor) More important, however, is the prevention of harm from people who do this: in particular, individuals unvaccinated without medical reason should be barred from all public accommodations where their presence could put other lives at risk, including schools, parks, pools, and transit.

    Such a barring would, of course, have a nearly-catastrophic effect on the life of anyone not living in a remote, rural area; it essentially would reduce a person to second-class citizenship. However, I believe that this is a reasonable accommodation of the public safety interest, as by definition it is something which the person can circumvent by simply not putting the general public in danger by their mere presence.

    There are times when I'm willing to be fairly forgiving. When the rightness of a course of action is unclear, I'm generally in favor of letting said action be a matter of individual conscience. However, when an individual's actions put those around them at risk, this is exactly what we have laws for. You have no more personal right to expose others to deadly diseases than you do to fire a gun blindly into the street.
  • 363 plusses - 429 comments - 103 shares | Read in G+
  • Yonatan Zunger2013-06-02 00:11:30
    How to count to infinity

    One of the most basic questions in math is how to count things. You would think that this would be pretty simple, but it actually has a number of surprises in it -- some of which drove noted mathematicians mad. It turns out, for example, that “infinity” has a real and concrete meaning which you can talk about, and there are even sizes of infinity. Today I’m going to take a walk through the infinite -- and mind your sanity, please!

    Let’s start with a simple question: what does it mean for there to be three somethings? In fact, what does “three” actually mean? “The number that comes after two” is a bit of a cheat, since then you just have to define “number” and “two.” You can point to three oranges and indicate taking some away and adding them, which tells you how to work with three, but actually giving a definition is a bit tricky. The trick (as discovered in the 19th century) is that what you can define is “as many as:” I can say that there are as many apples in a pile as oranges if I can pair them up, one to one, without any left over. Then “three” can be defined by pointing at any group of three objects, say three oranges: there are three of any group of objects if they can be paired up, one-to-one, with that fixed group. And you can start to define adding (combine two groups), subtracting, and so on, and do math.

    OK, that seems like a fairly complicated way to define the obvious, but it turns out to be really important to define things carefully. For example, how many whole numbers are there? Well, it’s clearly bigger than any particular whole number, because you could always just add one. So the answer to this can’t be a whole number, and so traditionally this was called “infinity.”

    What’s interesting is that you can compare infinite numbers by pairing them up, just like you can with ordinary numbers. For example, there are exactly as many even numbers as there are whole numbers: simply pair 0 with 0, 1 with 2, 2 with 4, 3 with 6, and so on, and there you have a list with all the whole numbers on one side, all the even numbers on the other, and nothing left over. Even though there are whole numbers which aren’t even, there are still just as many of them.

    You can actually do this with every infinite sequence of numbers: there are as many whole numbers as there are odd numbers (0->1, 1->3, …), prime numbers (0->2, 1->3, 2->5, …), perfect squares (0->0, 1->1, 2->4, …), integers (0, 1, -1, 2, -2, 3, -3, …) and so on.

    Now let’s try something more interesting: there are as many whole numbers as there are fractions. To see this, let’s draw them all in a grid. At the bottom, let’s have an infinite row … -3/1, -2/1, -1/1, 0, 1/1, 2/1, 3/1, … Above that, the row …-3/2, -2/2, -1/2, 0/2, 1/2, 2/2, 3/2, … And so on. Every fraction appears in the grid; in fact, it appears repeatedly, since 1/1 = 2/2 = 3/3 = 1. But you can still pair off these numbers with the whole numbers: simply start at zero, then walk around in a spiral. You’ll walk along a path that crosses every one of these numbers exactly once, and by counting them off as you go, you’ve paired up the whole numbers and the fractions.

    In fact, until 1891, people thought this was great: a way to show that infinity is infinity, and you could always do this trick. Until, one day, Georg Cantor realized you couldn’t.

    Here’s what he did: Cantor asked if there are as many real numbers -- basically, decimals -- as there are whole numbers. And it’s really easy to see that the answer is no, and here’s how. Let’s just look at the numbers between 0 and 1. Imagine that you could, somehow, pair them up with the whole numbers. Then you’d have a list; maybe it would start out like

    0: 0.*1*000000......
    1: 0.1*2*34567......
    2: 0.98*7*6543.....

    (Or it could start out some other way. The point is that what we’re about to do works for any list.) Now we’re going to construct another real number, X, as follows: pick the first digit of the first number, and add one to it. (If it’s a 9, turn it into a 0) That’s the first digit of X. Now pick the second digit of the second number, add one to it, and that’s the second digit of X. And so on. So for our list above, X would be 0.238.... 

    And here’s the magic: X can be nowhere on that list. It can’t be the first number, because its first digit is different. It can’t be the second number, because its second digit is different. And so on. Which means that, no matter what list we made, we’ve always missed at least one number: there are more real numbers than there are whole numbers.

    You should know that mathematics doesn’t always attract the most stable personalities. The reaction to Cantor’s proof -- this argument we just went through -- was instant and rabid. He was called a scientific charlatan, a corrupter of youth, his work “laughable,” and even a heretic: some people believed that, by proving that there were different sizes of infinite number, he was challenging the uniqueness of God (!). His fiercest critic, fellow mathematician Leopold Kronecker, ended up so firm in his opposition to Cantor that he denied the existence of fractions: he was famously quoted as saying “God made natural numbers; all else is the work of man.” Cantor was already prone to depression, and ended up spending much of the rest of his life in mental hospitals; as the attacks mounted, he added paranoia to his repertoire. (See the graphic novel “Logicomix” if you want to hear the full story; it’s fascinating.)

    Cantor did a lot more than just this proof, and his “diagonal argument” -- the argument above -- can actually prove even more than that there are more reals than integers. In fact, he proved that if you start with any set, finite or infinite, you can build a bigger set out of it called its power set.*

    This led to a whole branch of mathematics of coming up with bigger and bigger infinities. It’s kind of a fringe branch, but it’s interesting. Start with the number of whole numbers. The power set of that is a bigger infinity; in fact, you can prove that it’s the same size as the number of reals. And then you can take the power set of that, and of that, and so on, forever -- making an infinite tower of infinities. 

    One of the great mysteries of math for nearly 100 years was the “continuum hypothesis:” are there any infinite numbers between the number of whole numbers and the number of real numbers? It wasn’t answered until 1963: it turns out that you can prove that it’s impossible to either prove that such a number exists, or that it doesn’t. Which means that you’re free to accept either that there are, or that there aren’t, such numbers as an axiom. The consequences, and in fact the structure of mathematics, depends on which one you pick; there are two different mathematics.

    And there’s more! Now that we have an infinite stack of infinities, we can ask: are there any bigger infinities? Such a number is called an “inaccessible cardinal.” Turns out that you can’t prove the existence or nonexistence of these, either; you can have math either with or without them. And then there are more and more kinds of infinity you can define, each one bigger than the rest: a sort of hierarchy of different maths, each one with bigger numbers in it.

    And you would think that this could just go on forever, which (to be honest) would be kind of boring, at least if you’re over the age of 12. But it turns out that you can’t. If you define an infinite number that’s too big, then mathematics itself becomes inconsistent. For example, imagine you defined a really big infinite set, “the set of all possible sets.” This is obviously going to be bigger than any other possible set. But Bertrand Russell (the same guy who famously told Oswald Mosley, founder of the British Fascists, to get stuffed) proved that it doesn’t work: because if you had that set, you could define a slightly smaller set, “the set of all sets which don’t contain themselves.” Like the barber who shaves those who don’t shave themselves, the problem is who shaves the barber: does this set of Russell’s contain itself, or not? If it does, then by definition, it doesn’t; and if it doesn’t, by definition, it does.

    So the mathematics of infinity contains a strange world: you have infinite numbers, you can talk about their sizes, some infinities are bigger than others, and there’s even an infinite stack of infinite numbers; and you can keep extending math to add more and more; but at some point you get stuck, and there’s actually a largest infinite number which is logically possible.

    We’re still on the tail of this largest possible infinity. The big infinities we know have rather odd names -- Vopěnka, n-superhuge, Reinhardt -- and incredibly technical definitions. We know that, at least if you want many of the normal axioms of math, Reinhardt doesn’t work, nor does ω-superhuge, but n-superhuge does for any finite number n. 

    And why do we care? I think it’s because numbers are such a fundamental thing. We can imagine a world where the sky is green, or where gravity repels instead of attracts, but we can’t imagine a world where 2+2 isn’t 4, because that follows from the definitions of 2, +, and 4. And those definitions come out of the basic notion of counting and comparing things. So if we discover that some numbers simply can’t exist, we’ve found the limits of logic and counting itself. That’s a strange outer limit to probe, but it’s one of the farthest ones that human minds can reach. And sometimes, you need to explore just for the sake of seeing how damned far you’ll get.


    To learn more about some of the people I wrote about, you can start here:
    http://en.wikipedia.org/wiki/Georg_Cantor
    http://en.wikipedia.org/wiki/Leopold_Kronecker
    https://en.wikipedia.org/wiki/Bertrand_Russell

    The famous proofs and questions:
    http://en.wikipedia.org/wiki/Cantor's_diagonal_argument
    http://en.wikipedia.org/wiki/Continuum_hypothesis
    http://en.wikipedia.org/wiki/Inaccessible_cardinal

    There’s a whole crazy branch of math around this:
    http://en.wikipedia.org/wiki/Large_cardinal

    And to learn the mad stories of the lives of these people and their work, I highly recommend the graphic novel Logicomix: An Epic Search for Truth, (http://www.amazon.com/Logicomix-An-Epic-Search-Truth/dp/1596914521) which gives you a real sense of the people involved, and their work.

    Photo is the sculpture "Infinity," by José de Rivera; photo by Salticidae. (http://www.flickr.com/photos/salticidae/)


    * The power set of a set is a set of sets: it’s the set of every subset of the original set. For example, if you start out with the set {A, B}, containing two letters, then that set has four subsets: the empty set { }, the single-item sets {A} and {B}, and the original set {A, B}. The power set is the set of these sets: { { }, {A}, {B}, {A, ‘B} }. In fact, for any finite set with N elements in it, the power set has 2^N elements. Cantor showed that the power set is bigger than the original set for any set; the proof is almost the same as that for the reals, and essentially works by writing out each member of the power set as an infinite binary number. For example, in our set above, you could denote { } by “00” -- neither present; {A} by “01” and {B} by “10”; and {A, B} by “11.” Then you can apply the same sort of diagonal trick to lists of these binary numbers. 

    If you prefer this in very mathematical speak, let S be a set, and P(S) be its power set. Imagine there were a function f from S to P(S) which claims to list all the members of P(S). Now define the set X by being the set of members s of S such that s is not in f(s). Since X is a set of members of S, it’s a subset of S, and therefore by definition X is a member of P(S). If our list is really complete, then X must be in it; there must be some s such that f(s) = X. Now we have a problem: if s is in X, then by the definition of X, s is not in f(s), which is to say s is not in X, a contradiction. And if s is not in X, then by the definition of X, s is in f(s), which is to say in X. And therefore, there can be no such s and so our list must be incomplete!
  • 388 plusses - 156 comments - 206 shares | Read in G+
  • Yonatan Zunger2013-06-28 23:58:43
    RESHARE:
    Since so many people were enjoying the dance of circles and waves in my previous post (https://plus.google.com/+YonatanZunger/posts/Q8Hn9HuCiQG), I thought I'd reshare an old post about the orbits of the asteroids which goes with it. Look carefully: the dots in red (called the Hilda Group -- read the post to learn more) form a triangle, but the motion of each individual asteroid is a circle around the sun. No asteroid is ever making a sharp turn at the corner.

    Reshared text:
    Jupiter and the Sun are the two largest objects in our Solar System, and as they orbit around one another, they create regions where their gravity roughly cancels out. These are the Lagrangian points, created whenever two objects orbit one another: places where gravity is such that another small object can follow along in the orbit without being pulled in or out. And since things aren't getting pulled out of there, they get stuck in there as well: and so we have two large clumps of asteroids (and miscellaneous smaller space debris) in Jupiter's orbit. These are called the Trojan Asteroids; the group ahead of Jupiter is known as the Greek Camp, and the group behind it the Trojan Camp, with the asteroids in each camp being named after famous people in that war. Together, these two camps have as many asteroids as the Asteroid Belt.

    Other stable patterns are possible, too: another one is what's called a 3:2 resonance pattern, asteroids whose motion gets confined to a basically triangular shape by the combined pull of Jupiter and the Sun. This group (for Jupiter) is called the Hilda Family, and their route forms a triangle with its three points at the two Lagrange points and at the point on Jupiter's orbit directly opposite it from the Sun. 

    None of these orbits are perfectly stable, because each of these asteroids is subject to pulling from everything in the Solar System; as a result, an asteroid can shift from the Lagrange points to the Hilda family, and from the Hilda family to the Asteroid Belt (not shown), especially if it runs into something and changes its course. 

    The reason that Pluto was demoted from planet to dwarf planet is that we realized that these things are not only numerous, but some of them are quite big. Some things we formerly called asteroids are actually bigger than Pluto, so the naming started to seem a little silly. So our Solar System has, in decreasing order of size, four gas giant planets (Jupiter, Saturn, Neptune and Uranus); four rocky planets (Earth, Venus, Mars, and Mercury); five officially recognized dwarf planets (Eris, Pluto, Haumea, Makemake, and Ceres); and a tremendous number of asteroids. (We suspect that there are actually about 100 dwarf planets, but the job of classifying what's an asteroid and what's actually a planet is still in progress -- see the "dwarf planet" link below if you want to know the details)

    Ceres orbits in the Asteroid Belt, about halfway between Mars and Jupiter, just inside the triangle of the Hilda Family; Pluto and Haumea are both in the distant Kuiper Belt, outside the orbit of Neptune but shepherded by its orbit in much the same way that the Hildas are shepherded by Jupiter; Makemake is what's called a "cubewano," living in the Kuiper Belt but unshepherded, orbiting independently; and Eris is part of the Scattered Disc, the even more distant objects whose orbits don't sit nicely in the plane of the Solar System at all, having been kicked out of that plane by (we believe) scattering off large bodies like Jupiter.

    But mostly, I wanted to share this to show you how things orbit. This picture comes from the amazing archive at http://sajri.astronomy.cz/asteroidgroups/groups.htm, which has many other such pictures, and comes to me via +Max Rubenacker

    More information about all of these things:
    http://en.wikipedia.org/wiki/Lagrangian_point
    http://en.wikipedia.org/wiki/Trojan_(astronomy)
    http://en.wikipedia.org/wiki/Hilda_family
    http://en.wikipedia.org/wiki/Dwarf_planet
    http://en.wikipedia.org/wiki/Kuiper_belt
    http://en.wikipedia.org/wiki/Scattered_disc

    #ScienceEveryDay
  • 469 plusses - 38 comments - 196 shares | Read in G+
  • Yonatan Zunger2013-03-15 20:56:01
    There's been so much news lately from Mars, Europa, and Antarctica about the search for life in space that I thought it might be good to explain what's been quietly happening in science on this front. For centuries, people believed that the universe was full of life: there were people on the Moon, wise aliens on Mars and Venus, and so forth. This took a huge hit after the Viking landing on Mars in 1976 showed a dry and cold world, something that looked like it could never have supported life; and for some time, there was an increasing hunch that life was actually very rare, that the search for it outside of Earth was actually a vain hope, that we were alone.

    The past few years have made us rethink this. The gut feeling now -- though many have been reluctant to say this out loud, to risk making the prediction that proves wrong, or simply to jinx it -- is that life might be extremely common in our universe. Here are the things that have really changed that.

    Exoplanets: The first thing is that we discovered that planets aren't rare at all. For some time, we suspected that very few stars even had planets; but over the past few decades, we've found better and better ways to spot them, and now we're realizing that planets seem to be the common thing for stars to have. So far, we can only directly detect fairly large planets, mostly gas giants; they're bigger and exert more gravity so they're easier to spot. But large planets often have moons (and as I'll get to below, those can be great places for life!) and where there are large planets, there are likely also smaller ones. So the number of possible places where life could simply sit down and exist has gone up by a lot.

    Organic matter: Turns out there are more carbon compounds tooling about the universe than we suspected at first. Interstellar gas clouds, etc., tend to have good amounts of carbon (coming from old supernovae), and from spectroscopy it appears that they'll form the simple precursors of amino acids even floating on their own, in space. The building blocks of life are pretty common.

    Moving matter: Also, it looks like matter moves from planet to planet a bit more easily than we'd initially feared. There are plenty of meteorites on Earth which started their lives on Mars, and presumably vice-versa; comets ship materials all the way from the outer Solar System. Shipping things across star systems is obviously harder, but it's no longer something that's completely out of the question to imagine. Life in one place could easily spread to nearby places.

    More habitats: We used to think that, for example, Jupiter and the whole Jovian system had to be dead. But now we've discovered that its moon Europa (pictured below) is basically a giant saltwater ocean the size of Australia under a protective layer of ice. Jupiter not only acts as a giant solar mirror, bringing Europa much more light than it would otherwise get, it also emits a nearly equal amount of heat just from its own contraction. Its magnetic field shields its moons from the Solar Wind, and its moon Io's perpetual volcanoes fill the entire Jovian magnetosphere with a steady bath of some very interesting ions. 

    Similarly, the more we probe Mars, the more we discover that it had some useful conditions for life in its past: free-flowing surface water, chemical gradients in the ground of the sorts that many Earth microorganisms use for fuel, etc. Even though Mars may have never been good for large-scale amounts of life (it never had that great an atmosphere), it could have held something, at least for a while.

    Life is tenacious: We've been studying "extremophiles" on Earth -- life forms which can live in insane environments. Volcanic vents at the bottom of the ocean support worms that live at temperatures as high as 400C. Tardigrades are small water-dwelling creatures which can survive in the vacuum and radiation of outer space. The Vostok Sea, locked two and a half miles beneath the Antarctic ice for tens of millions of years, and far from any source of light or outside food, nonetheless turns out to sustain life forms all of its own. And now we're finding microbes living in the rock hundreds of meters under the sea floor of the Juan de Fuca Ridge. It increasingly appears that life will survive, and thrive, anywhere that it gets a chance. And there are more places that give it a chance than we ever thought before.

    None of these things add up to a discovery of life not on Earth, but all of them mean that, rather than requiring an incredible set of coincidences never to be repeated, life may actually be a common phenomenon, requiring only a star, a planet or appropriate moon at the right temperature and gravity,  some chemicals occurring fairly frequently in space, and either a bit of luck or a boost from a nearby planet. 

    It's possible that, during our lifetimes, we'll see the first discovery of life that's not on Earth. And even if that life is no more than a bacterium, that means that there could be more life out there; that we could understand the ranges and possibilities of life, and perhaps even discover that there are other things out there that we could talk to.

    Some interesting places to start for more information:

    http://en.wikipedia.org/wiki/Europa_(moon)
    http://en.wikipedia.org/wiki/Hydrothermal_vent
    http://en.wikipedia.org/wiki/Tardigrade
    http://en.wikipedia.org/wiki/Vostok_Station
    http://news.sciencemag.org/sciencenow/2013/03/microbes-likely-abundant-hundred.html
  • 491 plusses - 113 comments - 136 shares | Read in G+
  • Yonatan Zunger2011-07-07 18:14:39
    Circle Strategies

    Lots of people have been posting strategies for organizing your circles on Google+, and I thought it would be nice to pull together some of the most interesting ones I've seen. (These come from a lot of people!)

    * Have circles corresponding to groups of people which match groups that you would chat with in your life; e.g., particular groups of friends, family, and so on. Don't obsess over how to partition people; if someone fits naturally into both circles, put them in both. These are your "sharing circles," and are great both to read (you're now hanging out with just this group!) and to share with.

    * Have other circles corresponding to groups of people you like to read, but don't necessarily want to follow or specifically share with. e.g., "Random interesting people," "Musicians," "Friends." (See how that's different? All your friends in one pile, rather than chopped up.) These are your "viewing circles."

    * A "local people to hang out with" circle can be very useful when you want to see who's up for dinner.

    * Create a couple of empty circles for your own purposes -- e.g., "drafts" or "bookmarks." That way, when you come across something that you want to save for your own reference, you can share it with that circle, and only you can see it.

    * If you have a lot of circles, give them slightly layered names. "Sharing: College Friends", "Sharing: Extended Family", "Viewing: Tech Press" will group circles together for easy access. (This is a temporary hack, of course, until there's a better way to do this -- but it's easy to rename your circles later to get rid of this)

    * Important point: When people you don't know start following you, don't sweat it, and don't add them to any circles. Circles are useful when you want to follow someone, or when you actually have a relationship with them and want to share things with them. If people are just following you asymmetrically, that means that they want to see your public posts. Basically, they're your fans. :) You can see what they're posting in your Incoming stream and then add them to circles if you decide to later on.

    Are there any good techniques I've missed? What methods have other people found useful?
  • 126 plusses - 70 comments - 366 shares | Read in G+
  • Yonatan Zunger2013-09-16 20:46:32
    Here's some interesting science for your day. Remember that famous experiment that rats, once addicted to heroin, will keep pushing the lever to get more heroin, no matter what, until they die? The experiment that gets cited all the time in DARE and similar anti-drug classes as proof that, if ever you touch drugs, you will instantly die a horrible death? Turns out that it's not that simple.

    The rats in Goldstein's original study lived in small, cramped cages. Bruce Alexander of Simon Fraser University decided to test if that had something to do with it, and so built "Rat Park," a facility 200 times the size of a standard laboratory cage, occupied by 16-20 rats of both sexes, with food, balls and wheels to play on, and all the things you need in life to be a normal rat. It turns out that rats in this environment -- even when they had been deliberately dosed with morphine for 57 days in a row prior to putting them into the rat park, something which you would think is pretty certain to create addiction -- preferred ordinary water to water laced with morphine. The control group of rats, kept in small cages, still loved the drugs.

    So it turns out that the relationship between drugs and addiction isn't as simple as "you take it, you're hooked on it, then you die." Rats locked in a small prison cell and given nothing but morphine for entertainment do, rather unsurprisingly, get pretty seriously into drugs -- but given the choice between being continuously stoned and having an actual rat life, most rats would prefer to just be rats. And importantly, this is true even for rats who had already taken plenty of drugs; apparently, most rats don't consider this to be the be-all and end-all of rodent existence.

    Which isn't really surprising; after all, if people didn't overall prefer not to be on drugs than to be on drugs, our society would be a lot more high than it is. I mean, if you're reading this right now -- are you feeling an urge for some smack? Are you thinking, "why am I reading yet another one of Yonatan's posts, when I could be shooting up?"

    It's possible that you are, in which case I should probably pep up my writing style. But if you aren't, then here's some science to help clarify why.

    Edited to add: +Harald Wagener provided a link to an excellent comic by Stuart McMillen telling you much more about the Rat Park experiment: http://www.stuartmcmillen.com/comics_en/rat-park/

    via +Aleatha Parker-Wood and +Chris Wassman.
  • 335 plusses - 81 comments - 231 shares | Read in G+
  • Yonatan Zunger2013-07-01 17:45:47
    Your random word of the day: Objectification

    If you ever hear people talking about women’s role in movies, or video games, or the like, you may have come across the word “objectification.” I spent years being confused about what this meant, because nobody ever explained it very well, and thought it meant something crazy when actually it turns out to be something really interesting and important. A few years ago I finally got a better explanation, so today I’m going to share it. (And side note: if you’re going to comment here, read what I have to say carefully. If you comment and it’s obvious that you didn’t read what I said and are instead having a rant about your own thing, I’ll just delete the comment. K?)

    So let me tell you what it isn’t, because you may have heard that, too. I had a teacher (way) back in high school who was very well-intentioned but absolutely terrible at explaining things, who somehow managed to communicate that “objectification” meant “treating people like things,” that any ad that “didn’t show the entire woman” -- e.g., had part of a woman’s body cropped -- was objectifying, and (via some lecture by Naomi Wolf) that such ads would therefore cause men to rape, murder, and dump women’s bodies in dumpsters. By the end of the week, the entire class thought she must be high as a kite, and that objectification was some kind of crazy nonsense.

    What I finally figured out a few years ago was that the word “objectification” doesn’t come from the word “object” as-opposed-to-person: it comes from the word “object” as-opposed-to-subject. 

    Here’s what it means: Say I’m telling a story. It can be a book, a movie, a video game, even the implicit “story” in a billboard, doesn’t matter. A character has a “subject perspective” if we see the story through their eyes: we get a sense of what they’re thinking, what the problems in the story mean to them, what choices they feel that they have and how they pick between them. A character has “object perspective” if they’re simply the thing that’s acted upon: we only really see them as they affect our main, subject, characters. 

    Every story is going to have plenty of characters in object perspective: if you tried to tell a story where the reader ended up knowing the detailed thoughts of every single person, down to the guy who sells the protagonist a bottle of water and whose only line is “One fifty, please,” or the mook whose job it is to get gunned down on the way to the enemy base and whose only line is “urk!,” the story would be a total mess. Object perspective just means that the character isn’t ultimately important except as an obstacle: it’s not a bad thing.

    Objectification is what happens when you have not only a single story, but a whole swath of stories -- something as wide as “the category of all spy movies” -- and you suddenly notice that there’s a pattern, for example “every single woman has an object perspective.” (It doesn’t have to be every woman for this to be the case, but if it’s happening a good 98% of the time then this is what we’re talking about)

    And here’s the problem when this happens: if you’re reading a lot of these stories, and you don’t notice that it’s a pattern, it starts to just have this regular drumbeat that gets into your head without you noticing, where women (or whoever’s being steadily treated as objects -- this isn’t just about women, that’s just the common example) are “the thing you deal with to get to your real goal.” 

    Just to understand this, remember the subtle way that stories can mess with your head. Have you ever watched a really good spy movie and then for the next day looked at every building around you as something you might want to infiltrate? Or played GTA5 for a couple of hours too many, and the next time you passed a police car had to remind yourself that no, the correct course of action is probably not to ram it? You’re not crazy: the whole point of fiction is to get you into other people’s heads, to show you what it’s like to think about the world from that perspective. And the way your head works is that you see the stuff, and for a little while your head mirrors it, until you’ve had time to really process through the story and it becomes part of your repertoire of ways to look at the world. 

    That’s why objectification isn’t an issue so much about any one book or movie or whatever: after you process one thing, it goes away and you’re not in its headspace anymore. But if you start seeing the same pattern in a bunch of the things you’re reading and watching and playing, if every couple of days you find yourself in a headspace that sees the world like X, then X -- whatever it is -- becomes more and more a part of the way you look at the world. 

    So why is this a problem?

    So if you have a bunch of stories where women only show up in an object perspective, the pattern you’re getting in your head is that women’s thoughts ultimately don’t matter that much -- what’s really important in the story is the men’s thoughts. And you can imagine how that would mess with your head: if you’re male, the pattern is “yeah, whatever, the women will sort themselves out -- we should just do what’s important”, and if you’re female, the pattern is “what goes on with me isn’t really important, what’s really important is what happens to the guy.” That’s a subtle sort of thing, but it can really mess you up either way, especially if you don’t notice it’s happening.

    So how can objectification mess you up in life? There are all sorts of ways, but they all have to do with turning your life (and other people’s lives) into a kind of script where you’re the star and they’re supporting characters, whether they like it or not -- or, even screwier, where they’re the star and you’re never anything but a supporting character.

    Just as an example, consider what this can mean in a relationship. On the one end, you end up trying to script the lines, and pushing the other person into acting out the roles that you need them to act out. Maybe into being the one who takes care of you, or the one who nags you and so you get angry at them, or the perfect one who can do no wrong. (And therefore can never be allowed to screw up) Or on the other end, you can end up objectifying yourself, and not even thinking too hard anymore about what’s important to you -- you’re too busy fitting yourself into some role for the other person. And either way, you both end up play-acting scripts instead of paying attention to what would actually make you happy. Needless to say, this will not end well.

    So it’s not that any one movie or book or whatever is making things bad. It’s that seeing a bunch of them, so many that it starts to seem normal, where all the people of one category are in object perspective gets you used to thinking of them that way, and then you start doing that the rest of the time without noticing it. And that screws up your life and generally makes you and everyone else miserable.

    Some things that objectification isn’t

    Something that objectification isn’t: It doesn’t have to do with whether the women are strong or weak characters. It’s just as true if all the women in the stories are super-powered killers that our hero has to fight through as it is if they’re all slaves of the evil Wombat Lord that the hero is rescuing. Of course, if you’ve got a bunch of stories where all the women are weak and powerless, you’ve got another pattern going which is going to be a problem in a similar way. 

    And another thing it isn’t: It’s not really about any single book. Lots of conversations go totally off the rails when people start saying “but that book is different!” or “but that character is different!,” because that’s actually not the point -- a single story gets out of your head after a few days. Objectification is a phenomenon that matters when you’re talking about an entire corpus: you can talk about objectification in, say, action movies as a whole, or first-person shooters, or romance novels, and how a single story contributes to that.

    And it’s not just about women, even though that’s the example you see most often. There are whole swaths of literature (e.g., what the marketers call “chick lit”) in which the men, for example, are all objects who exist solely to be problems or goals for the women. It’s not as big a problem because someone who’s reading those stories is also probably being exposed to a lot of other stories (via TV, movies, ads, etc) where the men are all subjects, so the pattern gets broken. That’s why people don’t spend as much time worrying about the objectification of men -- even though it certainly happens.

    Fortunately, you can do something about it (not just for writers)

    What’s great about objectification as a problem is that it’s actually relatively easy to solve when you’re telling stories. You don’t have to make all your protagonists and antagonists women, you don’t have to make all the female characters “strong” for some definition of “strong.” Even one little thing can make a big difference: look across the swath of characters that you’re writing about, and make sure that the reader is seeing the story from more than one perspective. The woman that James Bond seduces in Act I scene II? Don’t just tell me that she falls in love with his incredible manliness and they have great sex. Give me, the reader, a sense of how she’s weighing him in her mind -- the choices she’s thinking about, maybe what it is in her past and her life that makes this guy seem so damned interesting. When he vanishes the next day, let me see that from her side: is she glad? Upset? Does she feel betrayed? Relieved? Looking forward to telling her friends? To subtly hinting about it to her boyfriend? 

    You don’t need to do this to every female character, any more than you need to do it to that water seller -- just let me know, as a reader, that all of the characters that I’m reading about have rich internal worlds and that there’s something interesting going on there. That their thoughts and feelings have value, even if that value isn’t the main point of the story.

    If you tell a story like that -- and not just if you’re writing a book, but even when you’re telling me the story of what you did last week, or when you’re telling yourself the story of what happened on your trip -- you’re going to tell a much better story. And your readers, or listeners, or watchers, or you yourself, will come out of it feeling like they’ve seen more of the world.


    Side note: If you’re interested in the telling of stories, +Mary Anne Mohanraj once wrote a great article a  few years ago (http://whatever.scalzi.com/2009/03/13/mary-anne-mohanraj-gets-you-up-to-speed-part-ii/) that talked about very similar things in the context of writing about characters of color. All the same sorts of ideas apply, and ever since I read this essay I’ve looked at stories differently: you realize how crappy writing feels when a character is “just vaguely a white guy, instead of being a Polish-American second-generation teenage boy whose restaurant-owning father died in the Nazi camps and who now works as a line cook in a grimy diner on the north side of Chicago. It is the specificity, the detail of our lives that makes our characters live and breathe, creating the illusion that the people we write about are real.”
  • 263 plusses - 156 comments - 239 shares | Read in G+
  • Yonatan Zunger2014-03-17 07:05:02
    How Your Data is Stored, or, The Laws of the Imaginary Greeks

    If you don’t work in computers, you probably haven’t spent much time thinking about how data gets stored on computers or in the cloud. I’m not talking about the physical ways that hard disks or memory chips work, but about something that’s both a lot more complex and a lot more understandable than you might think: if you have a piece of data that many people want to read and edit at once, like a shared text file, a bank’s records, or the world in a multiplayer game, how does everyone agree on what’s in the document, and make sure that nobody overwrites someone else’s work? This is the problem of “distributed consensus,” and in order to discuss it, we’ll have to discuss bad burritos, sheep-tyrants, and the imaginary islands of ancient Greece.

    “The imaginary islands of what?,” you ask?

    It turns out that the original scientific paper about one of the most important methods used to solve this problem was written in the form of a lengthy discussion of how the part-time parliament of the imaginary ancient Greek island of Paxos managed to pass laws, despite nobody ever reliably showing up at the legislature. It was a wonderful metaphor for how a bunch of people can agree on what to write to a file, even though they might be unreachable or distant for a time – and the paper is both one of the funniest serious research papers ever published, and one of the best explanations of a complicated algorithm I’ve ever seen. And since this metaphor worked so well to explain one part of this problem, and because it’s a lot more fun than talking about file systems, I’m going to use it to explain all of it to you.

    The reason this metaphor works so well is that with both files and laws, we have some data which many people wish to change, many people wish to read, and none of these people want to spend forever doing so. Simultaneous reading of a law-book is limited by the number of people who can see the book at a time, just like reading a file can be limited by the speed at which data can come off a disk; simultaneous writing requires that everyone somehow agree not to overwrite one another, but without having to have lengthy debates before proceeding. Short of having every single person in the world take turns, with one person holding the book at a time, how can we solve this problem?

    So instead of a conversation about file systems and database transactions, let’s transport ourselves to the islands of the Fictional Aegean Sea, where everyone is obsessed with issuing decrees and making laws: they just need to make sure that everyone can read up on the law when they need to. We’ll go through some twisty passages, and by the time we’re done, you’ll actually understand distributed consensus the way professional computer scientists do. Only with more sheep.

    (Incidentally, there will be a bunch of islands, and their names are entirely made-up, except for the one which sparked this whole story, about which more later.)

    Of Hermits and Mexican Food

    We begin our story with the simplest of all of these islands, Pseudemoxos, home to a single hermit who is writing laws and decrees for her own use. At first, she used a very simple and obvious method: a notebook and a pencil. She could add laws, change laws, and reorganize laws at will, by simply erasing and writing new things down, wherever she pleased. (And this is, essentially, how the disks in your own computer worked until the late 1990’s)

    This method appeared to work reasonably well, except for the tendency of overly erased paper to wear thin. The hermit became horribly aware of the flaw in the design, however, when one day a crate of dubious burritos washed up on the shore. Halfway through writing a change in the law – having erased text and begun to write something – she experienced what we politely refer to in computer science as a “production emergency.” When our hermit returned to her law-book, somewhat the worse for wear, she found that not only had she forgotten what she was about to write, but there was now an empty space in the middle of the law-book filled with neither the old nor the new law, but scribbles written in such haste that even she couldn’t read them!

    (The metaphor, of course, is for what happens when a computer or a program suddenly failed partway through a write – the data on disk could get hopelessly corrupted. The metaphor extends as well to more serious failures of the hermit, where events like a head crash could cause damage not only to the words being written, but leave a rather unpleasant and permanent mark across the entire page.)

    Both of these problems are solved with what is known as journaling. The rule is to never erase anything – just like when people keep logbooks or lab notebooks. Now, our hermit keeps a stack of paper. When she wishes to make a change to the laws, she adds a note to her journal:

    June 4th, 10:32 – Append to the laws of food safety: The consumption of burritos which have been at sea for an undetermined length of time is forbidden.

    Every edit, be it an insertion, change, or deletion, is logged at the end of the journal, in pen. The hermit is protected from an emergency, because nothing is ever erased; at worst, there is an incomplete or damaged journal entry (missing, perhaps, its final period), the sign of a failed attempt at writing, which one may simply ignore. The journal has the additional advantage of serving as a record of all changes; to see how the law looked a year ago, for example, our hermit can simply read the journal and stop at that date.

    The one obvious flaw of the journal is that reading it is more difficult than reading a notebook: to know the current law on food safety, one has to start from the very beginning of the journal and read all the way through to the end, keeping track of all changes to the food safety law as one goes, a process which becomes steadily more onerous as time goes by and the journal gets longer.

    To simplify this, our hermit keeps a stack of empty law-books handy. Whenever the journal gets too long, she sets aside some time to make a digest of the law: she reads the journal from beginning to end, keeping notes on scrap paper if needed, forming a description of the current state of all of the law, and then writes out that current state into the law-book. On the cover of the law-book, she writes “This was the state of the law as of [some date].” Further reading of the law then only requires that she read the digest, and the journal of changes made after the digest’s date. Journals older than this can be kept, if a record of the change history prior to the digest is occasionally needed, or simply thrown away.

    If our hermit is too occupied with the business of drafting new legislation to regularly make a digest, she can simply employ a scribe (that is, a second computer program running in parallel to the first) to assist her. The scribe will simply read the journal up to some agreed-upon time, writing a digest and informing our hermit when he has finished, so that she can start using the new digest. The scribe need speak to nobody in order to do his job, so the hermit can continue in her labors, her silence unbroken.

    This method has still more benefits. Our hermit having become widely known for her wisdom (for example, her lessons on avoiding sea-borne Mexican cooking), many people may wish to read her law. So long as these readers are content to know the digest of the law up to a fairly recent time, they can simply make their own copies of a digest, and read freely without needing to disturb the sage at her work. Only a reader who needs an absolutely up-to-the-minute view of the laws need bother her directly.

    (The use of journaling for individual computers began in the late 1990’s, and became common in the mid-2000’s. Your computer today probably does this.)

    Chaos on the Island of Fotas

    Near Pseudemoxos is the somewhat larger island of Fotas. This island is sparsely inhabited, but there are enough people that the Fotans have all agreed that they need a mutual system of laws to govern their lives. However, the Fotans are known for their fierce independence: they are unwilling to allow any other Fotan, or group of Fotans, to have power over them, and so have decided that any and every Fotan shall have the power, independently, to enact a law, simply by writing down the law they wish to enact on a piece of paper, together with the date and time and their name, and sending it by messenger to the Library of Fotas, where a scribe will append it to the law-journals.

    (If it’s not clear, this represents the case where many people are trying to simultaneously write a single file without making any attempt to reach consensus about what goes into the file before they do so. It’s perhaps unsurprisingly difficult to do so without all hell breaking loose, but with a bit of cleverness – and some restrictions about how people learn about changes – it’s actually possible!)

    To see some of the ways in which this can go wrong, let us begin by considering Agnes, who lives on one side of the island and is very concerned with the purity of ritual sacrifices. She enacts a law:

    June 1st, Noon – Law 32.1.2 on the sale of sheep is amended to read: The sale or purchase of any sheep whose wool is not perfectly white shall be forbidden on penalty of death. Signed, Agnes.

    On the other side of the island, Basil, who has recently had a number of black sheep born which he is having trouble selling, enacts his own law:

    June 1st, Noon – Law 32.1.2 on the sale of sheep is amended to read: No person may refuse to buy or sell a sheep on the account of the color of its wool. Signed, Basil.

    Later that day, the scribe finds himself with two new laws, with the same time-stamp, even. What is he to do? When Basil next arrives in town to sell a black sheep to Galatea, and she refuses to buy a non-white sheep, and they go to read the law-book, which law should they obey? And what should happen when the scribe tries to write the next law-digest – what will Law 32.1.2 say? (In computer terms, two people have tried to write different data to the same part of the same file at once; the result could be absolutely anything. Agnes’s law may win, Basil’s law may win, we may end up with every other letter coming from each law, or anything else)

    To illustrate a more subtle kind of problem, imagine that Agnes wants to perform a “read-modify-write” of the law – that is, she looks at the current law, decides to make a change, and then writes the change. But just as she is doing this, Basil makes a conflicting change to the law. For example, at 10:00, Agnes reads the law to be

    Section 32.1.3. Any person selling a goat must pay a tax of one obol to the library general fund.

    She ponders this, and at 10:02 issues the following write:

    June 1st, 10:02 – Law 32.1.3 shall be amended to change “one obol” to “two obols.” Signed, Agnes.

    Unfortunately, at 10:01, Basil (who has little patience with goat-taxes) issued:

    June 1st, 10:01 – Law 32.1.3 shall be replaced with “The Ides of February is national olive day.” So there. Signed, Basil.

    Our scribe, attempting to reconcile the laws in order, is going to be very confused: when he reaches Agnes’ entry, law 32.1.3 is talking about National Olive Day, and doesn’t mention “one obol” anywhere. What is he to do? (And if you think this case is obvious, imagine if Basil’s law had instead replaced “the library general fund” with “Basil!” The scribe has no way of knowing if Agnes knew about this change or not before her own edit.)

    Situations like this happen whenever multiple writers can compete to edit the same book of law. There are numerous solutions, each with different pros and cons. These solutions fall into two basic categories. One is “eventual consistency” (or “weak consistency”), where a few rules about how writes work will allow everyone to write at the same time without speaking to one another. The cost of this is that nobody can know the exact state of the law at this instant; they can only know how it was a short time ago. The other is “strong consistency,” where all kinds of write are possible and everyone can know the current state of the law, but at the cost of each write requiring a process of consensus-building. 

    Both of these turn out to be useful. Sometimes, you have information where a bit of staleness is alright; for example, when the inhabitants of Fotas are making their annual yearbook, and exchanging pictures of one another’s profiles, there’s no pressing need to have the most up-to-the-moment pictures, and so the simpler eventually-consistent protocol will do nicely. On the other hand, for actual laws, strong consistency will prove the more useful, despite its cost. (This is true with computers as well. For example, images you upload to Google are stored using an eventually-consistent system, while the access control lists which define who can view what are stored using a strongly-consistent one)

    Let us return to the island of Fotas.

    Eventually, This All Makes Sense

    We could easily solve the first of our two problems – contradictory laws at the same timestamp – simply by agreeing upon a tie-breaking rule so that no two timestamps can ever match. For example, we could break ties in timestamp by the name of the author, in alphabetical order, so that in case of a race Agnes’ changes will always happen before Basil’s. (Or if names match, we could assign each Fotan a unique number ahead of time) Once the timestamps no longer match, there is no confusion: later laws always supercede earlier ones, and so when Galatea comes to town, Basil’s law is the one on the books.

    If mutual overwriting of this sort is a problem, it can be avoided by prior agreement about who can write what. For example, for one week Agnes might be allowed to edit only even-numbered laws, and Basil odd-numbered ones, switching the next week. (In computers, the space of files is often divided up so that two writers never attempt to write the same file at all, much less at the same time. For example, each newly-uploaded photo might be automatically assigned a unique name, so that only its uploader ever need write to that file)

    To solve the second problem, we simply decree it out of existence: we change the rules of the journal to forbid any “edit” statements, allowing only replacement, addition, or deletion. This means that no statement in the journal can ever depend on the current state of the law for its interpretation. Agnes would have had to instead write her law in the form

    June 1st, 10:02 – Law 32.1.3 shall be replaced with “Any person selling a goat must pay a tax of two obols to the Senate.” Agnes.

    and, since her write had a later timestamp, her version would win over Basil’s without confusion.


    Such a system of writing laws has the benefit of speed and simplicity: anyone can still write a law at any time, without consulting with anyone else. However, reading the laws becomes surprisingly tricky. Say you want to know the current goat-selling tax, and so you go to the library and ask to read Law 32.1.3. Arriving at 10:05, you read the digest and the journal, and find that it reads: “Any person selling a goat must pay a tax of one obol to the Senate.”

    You see, Agnes changed the law at 10:02 by her time – but her messenger hasn’t arrived yet! All you can know is that, as of the last time the journals were written, this was what the law said.

    To make things a little better, messengers can check in at the library: whenever a messenger arrives from a given Fotan, after they deliver their messages, they write a note on the board indicating that all of the given Fotan’s messages have been delivered at such-and-such a time. A visitor can then look at the board. If the last message from Agnes was at 9 that morning, and the last message from Basil was at 7 the previous evening, and so on, then you know, at least, that the laws you are reading were accurate as of 7 the previous evening – the earliest of the times shown on the board, since all edits prior to that must have arrived. (This time is known as the “low-water mark”)

    Of course, if a particular Fotan isn’t very litigious, their updates might be rare, and so everyone will be wondering if they have made a recent change which simply hasn’t arrived at the library yet, or if they simply haven’t had anything to report in weeks. To avoid this problem, each Fotan must send a messenger to the library at regular intervals, whether they have any updates to make or not, so that the board remains fresh.

    Now, the Fotans are a creative people, and so they quickly realized that this steady stream of messengers could simplify their lives further. Rather than having to make the tedious trek to the library themselves, they can simply maintain their own copy of the law-digest and law-journal. Their messenger simply returns, each time, with all of the changes to the law-journal which have been made since the last time they sent a messenger to the library, as well as a copy of the dates which were on the board then. They simply update their own copy of the law-journal, digesting as needed, and can now refer to their own copy with as much ease as they could to the central reference copy.

    As the Fotan population progressed, however, the traffic at the library became a problem, what with all of the messengers running back and forth and the scribes copying journals and digests, and the task of simply making a law to change the goat-tax became obnoxiously slow. Fortunately, the Fotans realized that they had solved their own problem: having their own copies of the law, they no longer needed a single central library!

    Instead, several branch libraries were opened. Messengers could simply deliver and receive updates at the nearest branch libraries, and other messengers would travel between each pair of branch libraries, transferring copies of all of the updates to the journals. Ultimately, a “tree map” was built: a diagram connecting each of the branches to one another, and each Fotan to a branch library. Updates were delivered only along the routes shown in the tree, but since each Fotan or library was connected to each other Fotan or library, eventually, any change made by any Fotan would reach every other Fotan. And since everyone would ultimately have the same journal in hand, their law-books would eventually be consistent!

    This has many nice advantages: for example, when having to navigate a difficult or expensive road, such as the treacherous toll-road which is the only access from the central island to its eastern mountains, only one messenger need traverse that path; he will simply deliver updates from the West to the East, and vice-versa, with the branch libraries at opposite ends of the road propagating the information to the rest of their ends of the island.

    (You may notice, at this point, that there is no longer any meaningful difference between an individual Fotan and a branch library – and that’s exactly right! Everyone has a copy, and so long as they continue to send messengers along the appropriate routes, everyone can change the law simply by writing in their own journal, and trusting in their messengers to propagate the information elsewhere)

    This method is thus very efficient, but has three notable weaknesses. First, it is impossible for anyone to know the current state of the law with certainty. Unlike writing to one’s own journal, like a Pseudemoxian hermit, one no longer has the guarantee that, after finishing a change, anyone reading in the future will see that change; only that anyone reading sufficiently far in the future will see that change. (This is known as a lack of “read-after-write” consistency)

    Second, it is impossible to perform a read-modify-write. This means that, if there are ever two Fotans attempting to change the same law, the consequences are unpredictable: neither Fotan, at the moment that they issue the change, can know with certainty if another change hasn’t already begun, and whether that other change will end up happening before or after theirs, meaning which change will end up in their law-journals after all changes have arrived at both of their homes. To circumvent this, a Fotan has to both find some way to guarantee that he is the only Fotan attempting to change a given law, and that he has read an up-to-the-minute version of the law prior to changing it. 

    Third, this method is vulnerable to network failures: imagine that the road leading up to a single Fotan’s remote house is cut off by a rockslide. No updates can reach the outside world from him, and so nobody can assume that they have all the updates from any time more recent than the last message to get from this Fotan to the safe side of the road. But neither can they assume that he transmitted nothing since then; for all they know, he is blissfully unaware of the rockslide and continuing to write to his own journal, awaiting a messenger who will never come. The entire system therefore comes to a halt, with nobody’s low-water mark advancing, and therefore nobody able to form a new digest, all because a single road failed!

    In computing practice, such problems are real and serious. Whenever a single node (a computer, or perhaps a datacenter) becomes disconnected, production engineers need to immediately evaluate the situation and determine if it is likely to be fixed and reconnected quickly. If it does not, every other server will be unable to form digests, and so their journals will continue to grow, causing problems for readers, while the isolated writer becomes more and more out-of-sync. If the problem cannot be fixed quickly, the isolated nodes are often switched off completely, and other methods are used to route people who wish to connect to them to other computers elsewhere – often through a much slower external network, but hopefully one which was not compromised. However, the other nodes will continue to wait. If it becomes clear that a fix will not be short in coming at all, there is only one alternative: remove the missing nodes from the network entirely, telling the other nodes to pretend that they no longer exist and that no updates from them will ever be forthcoming. The other nodes progress, but any writes which the isolated node performed after the isolation – unless they can be copied off and transferred to the main network by other means – will be permanently lost. 

    The Clients of Fotas, and Strong Consistency

    So what we have seen above is a reasonable solution for fiercely independent islanders like the Fotans, who want to be able to write quickly and aren’t entirely concerned with being able to read the latest version of something. But what happens in situations where that simply isn’t acceptable? Laws are actually a good example – if you commit a crime at 10:00, it matters a lot whether the law against it was passed at 9:00 or 11:00. Knowing the law up-to-the-moment is important.

    The problem became far worse when Fotas went into the law-book business. You see, Fotas is surrounded by many much smaller islands, each of which has its own industry and thus requires its own law-book. Being small islands, they do not have the resources to maintain the intensive Fotian system of scribes and messengers themselves; and even if they did, they would never be able to train those scribes and messengers to work as quickly or efficiently as those of the Fotans, who are (one must admit) kind of obsessed with this. These small islands therefore continued for years to use the simplest and most brute-force solution: each island had its own hermit with a law-journal, in the Pseudemoxian Style, and everyone who wished to read or change a law simply lined up and dealt with the hermit one-by-one. It is slow and inefficient, and may the Immortal Gods protect them if their hermit happens to get sick, or be swept away by a tidal wave. But lacking the resources of an island like Fotas, they simply continued about their way.

    The Fotans therefore smelled an opportunity of offering their law-books as a service to their neighbors; those client islands could simply read and write their information from a part of the Fotian law-book, each island receiving its own dedicated chapter which nobody else could write. 

    The neighbors, at first, were thrilled: because everyone no longer had to line up to speak to a single hermit, the process became much faster, even taking into account the travel time to Fotas. (In fact, the Fotans worked to improve this travel time by setting up embassies on these various islands which were part of the Fotan network) It was also much more reliable, as everyone was reminded when a tidal wave destroyed several islands and severely damaged Fotas itself. Because each Fotan had replicas of the full law-book, it was easy to recover. (The Fotans later improved on the system by having each chapter maintained by only some Fotans, spread across the island; this gave them the same general reliability without the expense of copying each client island’s laws to absolutely every point on Fotas) And since Fotas was close to so many islands, the islands could even begin to use the Fotian system as a way to reliably send messages to one another.

    But the two problems we saw above became much more evident. For example, on the island of Parafoitas (one of the client islands), Andros’ wine company had been using Fotian storage to keep track of its orders. One day, Andros took an order for 100 amphorae of wine for a local politician’s wedding, and entered it in the order-book. The next day, one of his employees checked the order-book – but that employee’s messenger to Fotas happened to go to a different port than Andros’, and this port had not yet received the updates from the previous day’s write due to a mud-clogged road. The employee therefore didn’t know about the order, and the wine didn’t make it until the day after the wedding! (Andros considered keeping a board in his office listing at what time each order-entry had been made, which everyone would check prior to filing or fulfilling orders, but stopped when he realized that he had just made his very own hermit-board, in which case what the hell was he paying these Fotans for, anyway?) 

    On the island of Siranos, things went no better. There, they had tried to resolve the problem of read-modify-writes by having Baucis in charge of even-numbered laws on Monday and Galen the odd-numbered ones, switching on Tuesdays, and so on, so that only one person might try to affect a law at a time. But as it happened, Galen was quite impatient to change a certain even-numbered law, and so he did so at precisely midnight on Tuesday, as soon as he could. Unfortunately, Baucis had made a change to the same law at 11:58 the previous night, and her change was not yet visible to Galen when he made his own change – so Galen issued a change, thinking he was the only person doing so, and unintentionally overwrote Baucis’ work.

    Some of the neighboring islands, on the other hand, were quite satisfied; Epifoitas, for example, had been using Fotian storage to keep an archive of their poetry. Once a poem was committed to the archive, it would never be changed, only read, and new poems perhaps added in response; as such, there was never a concern that a poem might be overwritten. For them, the Fotian system was both reliable and inexpensive. But on the whole, there were enough islands who wanted to regularly read and write their texts that the inadequacies of the Fotian method became clear.

    The Part-Time Parliament of Paxos

    So now we come to the island of Paxos. This is the original imaginary Aegean island of Leslie Lamport’s invention which led to this whole metaphor, and in fact the method he described is universally known as “the Paxos algorithm” because of it. (All of the other island names in this article have been my own invention) 

    The good news about this algorithm is that it’s no more complicated than what we just discussed, and his paper discusses it in the same style; if you’re comfortable reading this, you can now simply pick up Lamport’s paper (“The Part-Time Parliament,” https://research.microsoft.com/en-us/um/people/lamport/pubs/lamport-paxos.pdf) and read it without difficulty. The bad news is that I can’t think of any way to explain it which is shorter than Lamport’s explanation, and that would make this already-long story insanely long, so I’ll leave you to his tender mercies for the details. But I can give you a summary of the idea:

    The Paxons were concerned with keeping track of their own laws, and as such were very concerned with having read-after-write consistency, so that everyone might know the current law of the land. They also wished to have read-modify-write consistency, since otherwise they might accidentally pass conflicting laws. Together, this kind of consistency is often referred to as strong consistency, whereas the weaker properties of the Fotian system are called eventual (or weak) consistency.

    The details of the Paxon problem (which you’ll learn more about if you read the paper) were slightly different: their laws were passed only by their Parliament, which met in a single house and so they didn’t have to worry about members suddenly becoming unreachable due to mudslides or tidal waves. But instead, they had a part-time parliament: legislators who were prone to coming and going as they pleased, becoming unreachable not because of a natural disaster but because of a particularly good amphora of wine. And due to poor acoustics in the hall, oratory was impossible, and legislators had to communicate with each other via messengers, just like the Fotans. So despite the superficial differences, the part-time parliament of Paxos posed all of the same logistical complications as the spread-out parliament of Fotas. 

    The core idea of the Paxos solution is simple: in order to make a change to the laws, you get a majority of Paxons to make the same change. At that point, if someone is trying to make a contradictory change, when they try to build up their own majority, it’s guaranteed to include at least one person who knows about the other change, and who can stop them and say “Wait! We are already voting on something different!” (Because if you have two sets of Paxons, each of which is bigger than half, there must be at least one person in common between them!) Likewise, when you wish to read the laws, you ask a majority of Paxons for the latest version of the law; again, if any change has been made, at least one of them must have heard of it. The details amount to a method of keeping track of which ballots are currently in progress, based on each Paxon having their own law-journal and note-pad where they track their own votes and the messages they have received. 

    Lamport’s method provides several important guarantees: it has read-after-write consistency, in that once the consensus condition has occurred for a proposed law, it is guaranteed that every future attempt to read that law will see that consensus; it makes read-modify-writes possible, in that once a change to a given law begins, either that change will end with no intervening writes having been allowed, or (if it was discovered partway through that an intervening write had already started) that change will fail unambiguously and everyone will know to try again; and it further satisfies the “progress condition,” that “if a majority of the legislators were in the Chamber and no one entered or left the Chamber for a sufficiently long period of time, then any decree proposed by a legislator in the Chamber would be passed, and every decree that had been passed would appear in the ledger of every legislator in the Chamber.”

    However, it does this at a cost. Passing a law – that is, writing to the system – requires building a consensus among a majority of members. If some of the members are distant from the originator, then this is potentially a very slow process; you can no longer add a law by simply writing it in your own journal. Reading a law becomes a slow process as well, as that process now requires asking a quorum of Paxons about their view of the law. 

    To moderate this, in practice Paxon systems provide two methods of reading: “Read-latest,” which performs the quorum read as above, and “read-recent,” which consists of simply checking your own log-book. Recent reads lack the consistency guarantees of the Paxos system, but they are quick, and in practice many systems require these strong guarantees only some of the time. (e.g., Agnes and Basil may wish to do a read-latest when they are resolving their dispute over the sale of sheep, but on an ordinary day when one of them is heading to market, they will content themselves with a read-recent before leaving the house)

    Nonetheless, this means that the Paxos method always has a nontrivial speed cost, and as the number of people involved grows, this cost increases rapidly. (Even in the absence of long transit times, simple random variation in the time-to-answer of the individual Paxons takes its toll, as each operation requires waiting for over half of them to answer, so you end up waiting for the slower individuals)

    Composite Systems and Master Election: Back to Siranos

    One interesting property of these systems is that they can be combined. For example, in both the Fotas and Paxos systems, each legislator had a copy of the law-journals and their own note-pad. The design of those systems relies only on the fact that the legislator can write in their own books with the guarantees of strong consistency. In the case of those being ordinary notebooks, written and read only by one legislator, this is trivially achieved.

    But there’s no reason that this could only be achieved with a notebook, and this lets us solve more problems. Imagine a network of islands, each individually small, but separated from each other by large seas, as in the Pacific. (Or in computer terms, imagine a network of datacenters, each within a building, but spread over the entire world) Providing a strongly-consistent store using Paxos over such distances is horribly impractical, because each read or write requires a quorum, which requires multiple inter-island trips. However, each island can maintain its own strongly-consistent store using any of the means above, and then a separate, inter-island organization can maintain its own laws using any means it wishes, simply replacing individual notebooks with single-island stores. A client limited to a single island can then deal only with their own island’s system, while clients doing inter-island business can use a different system but get all of the robustness advantages of having more than a single point of contact on their island.

    This possibility led the Siranoi to reconsider their own system. Remember that this island had tried to achieve strong consistency by dividing up their laws by day, so that Baucis could write even-numbered laws on Monday and Galen on Tuesday, and vice-versa. Even though this simple system ran in to problems, it revealed an important truth: someone interested in the laws on sheep-selling on Monday was likely to still be interested in it on Tuesday, and changes of interest were relatively rare; and likewise, accidents which caused people to simply vanish – leaving nobody to deal with the laws on sheep – were also relatively rare. And even though many strongly-consistent methods are slow, it’s OK if you have to do something slow on rare occasion, if your day-to-day is quick.

    This led the Siranoi to ask themselves if, for any subject, they could simply elect a Tyrant who would be responsible for all laws related to that subject. So long as everyone could easily find out the Tyrant for any particular subject, and the Tyrant himself did not become overloaded with requests, this would achieve an even simpler form of strong consistency: anyone wishing to change the laws on that subject, or know the latest laws on the subject would simply communicate with the Tyrant, Pseudemoxian-Hermit style; whereas anyone wishing to simply get a good idea of the latest situation would read their own copy of the general law-books, copied to them Fotan-style. 

    The basic principle is simple. Say Baucis wishes to know the sheep-law. Baucis inquires of the central registry of Tyrants, “Who is the current Sheep-Tyrant?” If the registry says that Philemon is, then Baucis immediately knows where to go. If the registry says that nobody is, then she simply proposes a law to this registry, “Baucis shall be the Tyrant of Sheep.” If this law passes, then Baucis is now the sheep-tyrant, and can proceed entirely on her own; if the law fails, then another law must have passed in the interim, so she simply repeats her query. 

    As you may have guessed, the central registry of Tyrants is nothing more than another strongly-consistent store. For very small groups, a single hermit may be workable, but both for reasons of scale and reliability, it’s typically better to use the Paxos method to build the central Tyrant-registry. While inter-island Paxos can be extremely slow, you only need to access it on rare occasion, when you want to find out (or become) the Tyrant for some particular subject; ordinary communication on that subject is then one-to-one.

    This method has some wonderful advantages. If only one person is interested in a given subject (a common case, especially if the subjects are fairly narrow) then that person can become the Tyrant of that subject themselves, and need not deal with any neighbors at all; they can simply proceed like a hermit, reading and writing from their own book, secure in the knowledge that nobody else is permitted to change the law on their subject. If many people share a particular interest, then all of those people will have to queue up to speak to one Tyrant, but the Tyrant can immediately give them an answer, without having to wait for information to be carried across the island.

    There are a few problems, however. The first is dead Tyrants. Baucis, having reigned as the Tyrant of Sheep for many years, one day had a heart attack. Nobody knew about this, though, and so everyone concerned with ovine matters ended up queueing at her door, waiting forever for her to show up, and all sheep-law came to a halt for several days, until finally the door was broken down, and discovering her death, the Siranoi passed a law revoking her Tyranny. After this happened once, the Siranoi formalized the solution in a simple fashion, namely terms of office: rather than passing “Baucis shall be the Tyrant of Sheep,” Baucis would propose “Baucis shall be the Tyrant of Sheep until Thursday at Noon.” If she is still alive, and interested in sheep, then sometime that Thursday morning she can propose another ballot measure to extend her reign.

    The second problem is overloaded Tyrants. It’s one thing to be the Tyrant of Sheep on a small Aegean island; quite another to be the Tyrant of Sheep of New Zealand, where sheep outnumber people 7:1. The queues outside the Tyrant’s door would become quite intolerable!

    Fortunately, nothing in this system requires the Tyrant to be an individual – simply that the Tyrant must provide a strongly-consistent representation of their subject, as well as transmit updates to all other law-journals using some robust method. So on New Zealand, rather than a single individual being elected Tyrant of Sheep, a group of interested ranchers joined to form the Kiwi Sheep Tyranny Combine. Being a relatively small group of relatively reliable people, they can maintain a shared law-book using Paxos (or any other system) with reasonable ease and speed. If they find themselves routinely overloaded, they can simply add new members to their organization, so that more people can service client requests. 

    And rather usefully, they can continually improve their methods. When the KSTC is small, they might use a large-print journal which everyone can read at once, and in-house simply take turns; or they might divide up subjects amongst themselves, and if someone is temporarily unavailable deal with the matter on an ad hoc basis, someone else filling in; or they might use Paxos; or ultimately, as the KSTC grows, they might even subdivide sheep-law in their own way and perform internal master elections to determine, say, the Sub-Tyrant of Shearing in the Otago Region. What’s nice about this is that their clients never need understand, or even know, the details of how they store information in-house; so long as the KSTC provides the guarantee that anyone coming to the door will be treated to a strongly-consistent representation of the sheep-law, the methods can change repeatedly.

    The classic version of this master election protocol is called Chubby, and you can read more about it at http://static.googleusercontent.com/media/research.google.com/en/us/archive/chubby-osdi06.pdf

    In Summary

    If you have made it this far, you have just learned some of the most challenging topics in distributed computing. Nearly every problem in datacenter- or planet-scale computing boils down to these issues: how do you get a bunch of computers, often distant from one another, connected via unreliable links, and prone to going down at unpredictable intervals, to nonetheless agree on what information they store?

    In practice, there are four methods which are commonly used:

    * Single data stores (the Pseudemoxian Hermit), where a single computer keeps its own copy, everyone wishing to use it must take turns, and the system is vulnerable to a single disaster; however, the system is strongly consistent, dead-simple, and all other systems are built on top of it.

    * Eventually consistent replication (the Fotan system), where each participant has their own (strongly-consistent) store, and everyone changes and reads their own copy, distributing and receiving updates to all of their fellows later on. This has the advantage of speed and simplicity, as well as robustness to many kinds of disaster, but lacks the strong-consistent guarantees that once you write, all future readers will know about it. This system is very useful in cases where that guarantee isn’t needed, such as distributing copies of images (or other bulky data) which will never change after it is written, and where freshness isn’t really required.

    * Quorum decisions (the Paxon system – and unlike the other examples, this one is actually called “Paxos” in normal CS conversations), where reads and writes involve getting a majority of the participants to agree. This provides strong consistency and robustness, but can be very slow, especially when spread out over a wide area.

    * Master election (the Siranon system), where an expensive, strongly-consistent store is used to decide who is in charge of any subject for a time, and then that responsible party uses their own, smaller, strongly-consistent store to maintain the laws on that subject.

    The choice of systems, and how to combine them, is therefore a matter of practicality. For example, if one wishes to maintain a system where many users can simultaneously see changes to a piece of shared data in nearly real-time – perhaps a shared document, or a computer game – then it is helpful for that single piece of shared data to be administered by as small a group as possible. Master election works well in this case, with the individual master being optimized to handle a single piece of data quickly. Latency comes from the message transit time from the client to the master, and from queueing delays at the master; the latter can be resolved by making the master itself bigger (even turning it into a small cluster itself), while the former is just a problem.

    On the other hand, if one wishes to serve billions of images – data which tends towards the bulky – which are uploaded by users, then there is little advantage to be had from strong consistency, except as far as the uploading user is concerned. You can then handle the upload process itself by having a single server communicate with the user until the data is fully uploaded; since we know that this user is the only one looking at the pictures until the upload is complete, that single server is the “master” of that data by default with no additional trickery. Once the upload is complete, eventual consistency is more than enough. (This brings up even more interesting questions, like the possibility of “partial replication:” only some sites having a copy of each picture, but any site being able to access another site’s pictures if need be. My own work, a few years ago, was in that field)

    The best thing about these systems is that, from a client’s perspective, they are defined not by the methods but by the guarantees they provide. If you tell your clients that there is a strongly-consistent system here, and they can perform writes, read-current, and read-latest by coming to this Greek, so to speak, then you can continually change the method which you use (from single data files up through master election which selects clusters which themselves use Paxos or what-not) as the needs of your clients grow and change, without requiring any sort of consensus or agreement among them. 

    And with this, I now leave you. You have wandered through a series of ridiculous stories about imaginary islands, Sheep-Tyrants, mudslides, and the like; but what you just learned isn’t a baby version of computer science at all, but the actual real thing, what professionals spend their time on every day. So I hope that, even if you’re not a computer scientist yourself and never plan to be, you now have a better understanding of what’s involved in modern computing – or at least, the part which involves sheep.
  • 324 plusses - 79 comments - 234 shares | Read in G+
  • Yonatan Zunger2013-06-13 21:19:27
    This is how you lead. (Edited: Includes transcript!)

    In a day when the US armed forces are under fire from all quarters for not responsibly dealing with soldiers, sailors, airmen, and marines raping one another -- frequently, and with such impunity that the Senate is looking at a bill which would, essentially, strip responsibility for handling this from the chain of command -- it's stunning to see what real leadership can sound like. 

    Australia's military is facing something that's by comparison much smaller -- but Lt. Gen. Morrison, the Chief of the Army, has made his position on it absolutely clear. This is leadership. 

    If the US' senior chain of command were this explicit and direct, we would not be in the situation we are in now. Because things would never have been allowed to fall this far out of control.

    Watch this video -- it's short, to the point, utterly free of weasel words or legal cavil, and is exactly what you want your senior leaders to do when things go wrong. I would not want to be working for him and have him mad at me -- but he's a man I would be proud to work for.

    Transcript:

    Earlier today, I addressed the media, and through them, the Australian public, about ongoing investigations into a group of officers and NCOs whose conduct, if proven, has not only brought the Australian Army into disrepute, but has let down every one of of you, and all of those whose past service has won the respect of our nation.

    There are limits to how much I can tell you, because the investigations into this network, by both the New South Wales police and the ADF investigative service, are ongoing. But evidence collected to date has identified a group of men within our ranks who have allegedly produced highly inappropriate material demeaning women, and distributed it across the Internet and Defense's e-mail networks.

    If this is true, then the actions of these members are in dirtect contravention to every value the Australian army stands for. By now, I assume you know my attitude towards this type of conduct. I have stated categorically, many times, that the Army has to be an inclusive organization in which every soldier, man and woman, is able to reach their full potential, and is encouraged to do so. 

    Those who think that it is OK to behave in a way that demeans or exploits their colleagues have no place in this Army. Our service has been engaged in continuous operations since 1999, and in its longest war ever in Afghanistan. On all operations, female soldiers and officers have proven themselves worthy of the best traditions of the Australian Army. They are vital to us maintaining our capability, now and into the future. If that does not suit you, then get out.  You may find another employer where your attitude and behavior is acceptable -- but I doubt it. The same goes for those who think that toughness is built on humiliating others.

    Every one of us is responsible for the culture and reputation of our Army, and the environment in which we work. If you become aware of any individual degrading another, then show moral courage and take a stand against it. No-one has ever explained to me how the exploitation or degradation of others enhances capability or honours the traditions of the Australian Army. I will be ruthless in ridding the Army of people who cannot live up to its values, and I need every one of you to support me in achieving this. The standard you walk past is the standard you accept. That goes for all of us -- but especially those who, by their rank, have a leadership role.

    If we are a great national institution, if we care about the legacy left to us by those who have served before us, if we care about the legacy we leave to those who, in turn, will protect and secure Australia, then it is up to us to make a difference. If you're not up to it, find something else to do with your life. There is no place for you amongst this band of brothers and sisters. 
  • 371 plusses - 62 comments - 206 shares | Read in G+
  • Yonatan Zunger2014-01-25 09:19:16
    In case you've heard the reports and are wondering: the rumors that Stephen Hawking just claimed that black holes don't exist are false. Someone seems to have written a story based on a talk he just gave without actually understanding what he said, and the press picked it up.

    Fortunately, +Brian Koberlein has a good explanation of what Hawking actually proposed over here. Let me try to give an even shorter version:

    A "classical" black hole is something whose gravity is so strong that nothing, not even light (and nothing can travel faster than light) can escape. Because gravity gets stronger the closer you get to something, this means you don't have to be extremely heavy to be a black hole; a black hole could be as light as a feather or as heavy as a galaxy, so long as all of that mass was compressed tightly enough that you could get close enough for gravity to get that strong. (For example, to turn the Earth into a black hole, you would have to compress it down to the size of a marble)

    When you add quantum mechanics to the mix, the situation gets more complicated. It turns out that you can prove (this is actually the result that made Hawking famous in the first place) that when quantum mechanics gets involved, black holes aren't perfectly black -- instead, they glow faintly, occasionally emitting very light particles like photons and electrons. The heavier a black hole gets, the dimmer it is, so an astrophysical black hole (one made out of a star) is for all means and purposes black -- specifically, it's going to be gaining mass from absorbing random bits of stellar dust far faster than it's losing it to Hawking radiation. But a smaller black hole may start to burn off its mass this way, becoming smaller, and so brighter, until finally it burns out in a spectacular blaze of glory. (And in fact, if any black holes weighing about 10^11 kg -- about equal to the total mass of all the humans on the Earth -- were formed at the beginning of the universe, they would be undergoing final burnout right about now, so astronomers are searching for signs of this)

    It turns out that the naive calculations about this lead to a somewhat complicated paradox: basically, one of the most important predictions of quantum mechanics is Conservation of Information, sometimes referred to as "unitarity." Basically, this means that information is never lost: if you have the initial state of a system, you can play the laws of physics forward and see how things turn out, and if you have the final state of a system, you can play the laws of physics backwards and see how things started. That means that you can't have any process which destroys information -- for example, you can't have any process which takes two different initial states and ends up in the same final state, because then you couldn't play it back and figure out where it started. (It turns out that violating unitarity would lead to things like matter being created out of nowhere at rather alarming rates, so it's one of those laws of physics we're pretty damned confident about)

    But these quantum black holes, if you do the math the naive way, seem to violate unitarity: information goes in (in the form of, say, exactly what matter fell in to form the black hole in the first place) and a big explosion comes out, but that explosion is the same no matter how the black hole was formed. Clearly, this means the math is wrong -- and for various technical reasons, it turns out that getting the math right on this will make it easier to get the math right on a whole lot of more interesting problems, like understanding the formation of the Universe or its shape. So people have been discussing it for a while.

    And that was the subject of the conference where Hawking just gave his talk, the "Fuzz or Fire" workshop at UCSB. These refer to the two candidate solutions which people are discussing -- one of them (favored by Hawking) says that a barrier of turbulent quantum foam would form at the surface of the black hole, which causes the information of what falls in to be consumed in a mass of chaos (much like the weather), but this foam barrier can be shown to prevent the formation of the sort of surface which would genuinely lose information. The other (favored by many others in the field) instead suggests that as matter falls in to the black hole, the information gets stored inside the black hole itself and released in the precise pattern of the explosion -- but it turns out that this transfer of information from the matter to the black hole would create a rather literal "firewall" around the black hole.

    Basically, this paper is Hawking giving some arguments for the fuzz theory over the fire theory. I'm not current enough in the field to have an opinion, but I wouldn't say that anyone is buying it simply on anyone's say-so. (Hawking only finally agreed that information is not, in fact, lost in black holes a few years ago -- being pretty close to the last person in theoretical physics to finally come to that conclusion. He's a smart guy, but his word isn't gospel any more than anyone else's is) The quantum fuzz smells a bit wrong to me because the theories in question aren't generally prone to creating turbulent solutions, but the firewall smells a bit fishy to me as well for the reasons Hawking states. The right answer could well be something else entirely.

    The "no black holes" line came from misunderstanding Hawking's argument, that with this fuzz black holes wouldn't have an event horizon, the line beyond which light can't escape. But he meant that statement in the very technical sense, where "event horizon" implies a number of other things which includes information loss -- instead, he says, black holes would have an "apparent horizon," which is the term for a boundary which you basically can't escape until the black hole explodes. That's undoubtedly true, because an apparent horizon is basically the definition of the edge of something that acts like a black hole but has a finite lifespan. In fact, the whole fuzz-or-fire argument is basically around the shape of this apparent horizon, and just what kind of nasty shock you would be in for if you ran in to it. (Torn apart by quantum fuzz or burned to death by a quantum firewall being your two leading options. Isn't annihilation fun!)

    So don't worry. The universe is still basically unchanged, and there is still a giant black hole at the center of the galaxy which we are all slowly spinning around. Because the universe is awesome that way.

    (Hawking's paper: http://arxiv.org/pdf/1401.5761v1.pdf)
  • 470 plusses - 44 comments - 130 shares | Read in G+
  • Yonatan Zunger2011-07-06 02:01:20
    OK, so I can now give a clarification to the whole circles issue, after some very useful internal conversations, and especially some great clarifications from +Jean-Christophe Lilot. Short version: The initial advice was right, but missing a few useful warnings.

    So here is your new and improved, little-known useful feature of Google+:


    * If you edit your profile and click on the set of people in your circles, you can control whether or not people can discover who is in your circles. Note that even if it's public, this just lets people know "Bob is in your circles" – it never reveals which circle people are in. (So it's completely OK to have a "Jerks, but I want to know what they're saying" circle.) I'd actually recommend leaving this fairly open; that way, people can go through you and find more people they know. I've got mine set so that my circles are visible to other people in my circles.

    But one particularly useful thing you can do with this is to change the visibility on a per-circle basis. In particular, you can have some circles that anyone can find out about, some circles which are connections that only other people in your circles can know about, and some circles whose membership is completely private. If you have relationships you're not comfortable broadcasting, use this feature, it gives you flexibility.

    What does it mean for a circle membership to be private? It means that, if you're only following a person via a private circle, the fact that you're following this person will not be visible on either your publicly visible profile or theirs; it will be known only to you and to them.

    Now, some caveats:

    * No, we don't have a "follow someone and don't tell them you're following them" mode. That would be creepy. You can always see who you're following and who's following you from your circles page, and when someone starts to follow you you get a notification.

    * If that person follows you back, they would need to hide that separately. (If they wanted to) You could still show up on their profile as someone they're following, and they could show up on your profile as someone following you, but you have control over whether or not you announce that you're following them.

    * If you add a person to both a private circle and a public circle, then the fact that you're following them is still publicly visible.

    * Also, if you change an existing circle from public to private, it may take some time until you disappear from their profile page. Don't panic if you don't disappear instantly... and if it's really important to you to keep a relationship secret, keep it secret from the beginning. (Which is good advice for life in general)

    * If you share with this private circle, and someone clicks on the "Limited" link, they'll still see who can see that post. So if you don't want members of this circle to know about each other, either, don't put them all in the same circle and then share with that circle. :)

    My apologies for the confusion, and thanks to +Stephen Pearson for the original hard question which started this. :)
  • 84 plusses - 97 comments - 338 shares | Read in G+
  • Yonatan Zunger2013-12-04 20:49:52
    RESHARE:
    A great image of just how a bubble bursts.

    Reshared text:
    How a bubble bursts in slow motion
  • 487 plusses - 35 comments - 117 shares | Read in G+
  • Yonatan Zunger2013-02-19 02:35:59
    Today, +David Archer and +STEM Women on G+ shared some things about Cecilia Payne-Gaposchkin, the first person to earn a Ph.D. from Radcliffe College, and later the chair of Harvard's department of Astronomy. However, her work is largely unknown today – and having just spent an hour reading through some of it, this is something which needs to be fixed.

    Her most critical work was actually her Ph.D. thesis in 1925, in which she calculated the chemical composition of the stars. (http://articles.adsabs.harvard.edu//full/1925PhDT.........1P/0000001.000.html – thanks to +Rajini Rao for finding the link. Be warned, it's long!) The use of spectroscopy to determine which elements are present in the stars had started in the 1860's (and had led to the discovery of Helium), but figuring out how much of those elements is present was much more complicated. The idea is simple: each element (and each molecule, and each ionized atom, etc) absorbs light at a particular pattern of frequencies, which can be measured in the lab; hot objects emit light in a particular pattern; put them together, compare with the light you see coming from a star, and you should be able to figure out what's there. The hard part is that the precise patterns of absorption (etc) depend on things like the structures of temperature and pressure inside the star, which are rather hard to measure directly. Payne did the theoretical work of figuring out how to estimate all the critical quantities (using only the scientific knowledge of the 1920's! Remember, this is when quantum mechanics itself was in its infancy, and the idea of being able to calculate these things from first principles seemed impossible) and build a model of how the patterns of light should correspond to the abundances of the elements, and used that to compute just what the stars are made of. 

    Some of her big results:

    - All stars are made of roughly the same material, no matter what color they are.
    - The composition of the Sun is apparently very similar to the composition of the Earth, lending support to the idea that they were made out of the same material; but
    - The Sun also contains an enormous amount of Hydrogen and Helium, and is in fact almost entirely made out of those two elements.

    Under pressure from Russell (a noted astrophysicist of the day) she stepped back from that last conclusion, saying that the high abundances of those materials suggests that there must be an error in her method. There wasn't; that's what stars are made of.

    (NB: Several years later, Russell got the same answer using other methods, and concluded that she was in fact right. He was quite up-front about giving her credit, but others tended to ignore this, and give Russell most of the credit for the discovery)

    It's hard to overstate the importance of this work. Pretty much all of modern astrophysics (and no small part of nuclear physics) derives from our ability to measure these quantities. The famous B2FH paper, for example, which explained how the chemical elements were formed in the first place (inside stellar furnaces and supernovae) is built pretty much entirely on these sorts of calculations, and the techniques which Payne pioneered.

    Despite this, Payne's work has remained mostly unknown. I myself worked in a fairly related field – high-energy physics – and had never heard of her until today. (And so my estimate of the work's significance comes from digging it up and actually reading it, and knowing the big picture of where those results are used – results which I had known for years without ever thinking about who originally found them) 

    In fact, this paper has a few weaknesses – the weaknesses that you see when the author can't get the full support of the community. She backs away from the most significant result; all of the most important results are fairly buried in chapter 13, rather than placed front and center. I've seen many papers do this, and it's quite clear that if her advisors (Shapely and Eddington, two of the preëminent astronomers of the day) had backed her more firmly, or if the community had followed Russell's lead and properly credited the work when it was confirmed by Russell's results years later, this paper would have been more forcefully stated, and its significance would be better-known today. Given the impact of these methods on astrophysics, it is highly likely that she would have been awarded the Nobel Prize.

    (As it is, credit for this discovery seems to have diffused out across many researchers in the astronomical community, and no one person is considered "the" discoverer. But having read the paper and knowing its date, I think that it's more than fair to mark Payne as such; she worked out all of the details years before anyone else)

    So today, let's take some time to remember this extraordinary discovery. We know what's on the insides of stars because of her.

    #STEMWomen #ScienceEveryDay 
  • 319 plusses - 32 comments - 207 shares | Read in G+
  • Yonatan Zunger2014-04-17 05:49:58
    A CS question that I don't know the answer to

    A conversation on another thread raised an interesting question about computers that I can't figure out the answer to: Is judging a Turing Test easier than, harder than, or equivalently hard to passing a Turing Test?

    I figured I would throw this question out to the various computer scientists in the audience, since the answer isn't at all clear to me -- a Turing Test-passer doesn't seem to automatically be convertible into a Turing Test-judger or vice-versa -- and for the rest of you, I'll give some of the backstory of what this question means.

    So, what's a Turing Test?

    The Turing Test was a method proposed by Alan Turing (one of the founders of computer science) to determine if something had a human-equivalent intelligence or not. In this test, a judge tries to engage both a human and a computer in conversation. The human and computer are hidden from the judge, and the conversation is over some medium which doesn't make it obvious which is which -- say, IM -- and the judge's job is simple: to figure out which is which. Turing's idea was that to reliably pass such a test would be evidence that the computer is of human-equivalent intelligence.

    Today in CS, we refer to problems which require human-equivalent intelligence to solve as "AI-complete" problems; so Turing hypothesized that this test is AI-complete, and for several decades it was considered the prototypical AI-complete problem, even the definition of AI-completeness. In recent years, this has been cast into doubt as chatbots have gotten better and better at fooling people, doing everything from customer service to cybersex. However, this doubt might be real and it might not: another long-standing principle of AI research is that, whenever computers start to get good at a task that was historically considered AI, people redefine AI to be "oh, well, not that, even a computer can do it."

    The reason a Turing Test is complicated is that to carry on a conversation requires a surprisingly complex understanding of the world. For example, consider the "wug test," which human children can pass starting from an extremely early age. You make up a new word, "wug," and explain what it means, then have conversations about it. In one classic example, the experimenter shows the kids a whiteboard, and rubs a sponge which he calls a "wug" across it, which (thanks to some dye) marks the board purple. Human children will spontaneously talk about "wugging" the board; but they will never say that they are "wugging" the sponge. (It turns out that this has to do with how, when we put together sentence structures, the grammar we use depends a lot on which object is being changed by the action. This is why you can "pour water into a glass" and "fill a glass with water," but never "pour a glass with water" or "fill water into a glass.") 

    It turns out that even resolving what pronouns refer to is AI-complete. Consider the following dialogue:

    Woman: I'm leaving you.
    Man: ... Who is he?

    If you're a fluent English speaker, you probably had no difficulty understanding this dialogue. So tell me: who does "he" refer to in the second sentence? And what knowledge did you need in order to answer that?

    (If you want to learn more about this kind of cognitive linguistics, I highly recommend Steven Pinker's The Stuff of Thought [http://www.amazon.com/The-Stuff-Thought-Language-Window/dp/0143114247] as a good layman's introduction.)

    In Turing's proposal, the test was always administered by a human: the challenge, after all, was to see if a computer could be good enough to fool a human into accepting it as one as well. But given that we're getting computers which are doing a not-bad job at these tests, I'm starting to wonder: how good would a computer be at identifying other computers?

    It might be easier than passing a Turing Test. It could be that a computer could do a reasonable job of driving "ordinary" conversation off the rails (that being a common way of finding weaknesses in a Turing-bot) and, once a conversation had gone far enough away from what the computer attempting to pass the test could handle, its failures would become so obvious that it would be easy to identify.

    It might be harder than passing a Turing Test. It's possible that we could prove that any working Turing Test administrator could use that skill to also pass such a test -- but not every Turing Test-passing bot could be an administrator. Such a proof isn't obvious to me, but I wouldn't rule it out.

    Or it might be equivalently hard: either equivalent in the practical sense, that both would require AI-completeness, or equivalent in the deeper mathematical sense, that if you had a Turing Test-passing bot you could use it to build a Turing Test-administering bot and vice-versa. 

    If there is a difference between the two, then this might prove useful: for example, if it's easier to build a judge than a test passer, then Turing Tests could be the new CAPTCHA. (Which was +Chris Stehlik's original suggestion that sparked this whole conversation) 

    And either way, this might tell us something deep about the nature of intelligence.
  • 365 plusses - 233 comments - 82 shares | Read in G+
  • Yonatan Zunger2014-03-06 04:42:40
    Space is big. It's so incredibly big, and so empty, that it can be hard for any of us -- even scientists -- to really emotionally grasp it. This site shows us one of those things that we almost never see, and for good reason: a scale drawing of the Solar System, with the Moon being one pixel across. Scale drawings you normally see will either show the planets to scale, or the distances between them to scale, but not both; if you show them both to the same scale, well... you're going to have a long way to scroll. Worth makes the time pass with little remarks and thoughts on the way.

    The way to Pluto, that is. This map doesn't show any of the trans-Plutonian dwarves; you would have to scroll for a long, long time to get to them. (See http://blogs.scientificamerican.com/guest-blog/2013/07/15/you-havent-so-much-lost-a-planet-as-gained-five-dwarves/ for why)

    So as you move off into the interplanetary void, just remember:

    Space is big
    Space is dark
    It's hard to find
    A place to park.
    Burma Shave
  • 373 plusses - 53 comments - 155 shares | Read in G+
  • Yonatan Zunger2014-04-03 21:17:40
    +Charlie Stross has a challenging and very interesting essay asking the question: Why should we work?

    http://www.antipope.org/charlie/blog-static/2014/04/a-nation-of-slaves.html

    We tend to talk around this issue a lot, but a key issue is this: as productivity (the amount of stuff of value we can create per hour of work) goes up, how much of that increase do we put in to increasing the amount of stuff of value we create, and how much do we put into decreasing the amount of work we do -- or put another way, what's the value of leisure?

    Another way to look at this is to consider an extreme limit. Say that tomorrow, someone invented a couple of Magic Boxes. One of them lets you pour cheap raw materials (dirt, rocks) in one end, push a button, and anything you request, from a hamburger to a car, comes out the other end. Another one will answer any question you ask, organize anything you need organized, do research for you, synthesize the data, explain things to you, and so on. A third one will pick up any physical item and take it anywhere in the world you need to be. If it's not obvious, these magic boxes are just the limits of technology we already have.

    Now in this post-Magic Box world, a lot of good things happen. For one thing, magic boxes themselves are cheap, because they can be made by magic boxes. (Someone will try to ban that, of course, and this will work about as well as banning people from humming songs) It's hard to go hungry when you can just dump dirt into your magic box and get a meal. Likewise, any clothing, shelter, and medicine you might need is just there, and another magic box can help you figure out which things will help you satisfy your needs. If you can afford the cheapest magic box, you can have the riches of Croesos.

    On the other hand, you might notice that a huge fraction of all jobs in the world would cease to exist as well. Almost the entire manufacturing, service, logistics, or information sectors would cease to exist. Pretty much the only jobs remaining would be to come up with new designs to fit in to the magic boxes -- and it's not hard to imagine that magic boxes could do a lot of that, too. 

    If we kept running the world the way we do now -- the way it would happen if someone literally invented these boxes tomorrow -- then we would find ourselves in a very strange state. Having successfully pushed productivity to infinity, and eliminated all possible cause for want in the world, almost everyone in the world would be suddenly unemployed, unable to access a magic box, and would starve to death.

    This is obviously stupid.

    The flaw in this, of course, is that our tendency to tie work to access to resources makes no sense in a world where the total amount of actual work to be done is much less than the total number of people around to do it. In this post-Box world, there simply aren't enough jobs for everyone.

    That's not a bad thing for the basic reason that Stross explains. Most jobs aren't things you would want for their own sakes. Consider: If you suddenly inherited £100M, would you stay in your job? If you would -- if you would do this job even if it had nothing to do with earning money -- then your job is actually worth something to you in its own right, and you would probably keep doing it in a post-Box world. If, on the other hand, you would leave your job immediately, then your job has no value of its own to you: it exists only as a means to an end, and as soon as you have a better means, you're out of there.

    The reason this is important is that we're already in the early days of the Magic Box Economy. When we see jobs disappearing around the world and not being replaced by new jobs -- entire trade sectors vanishing -- and the overall actual unemployment rate (not the rate of people looking for work, but the rate of people who aren't working for pay at all) rising, but at the same time overall global productivity is increasing, what we're seeing is that many of the jobs which used to be necessary for us as a species to survive are simply no longer needed. 

    However, our economy, and our thinking about the economy, continues to be based on the idea that jobs are good, and working is good, and if you aren't trying to work harder, something must be wrong with you. Which means that, as people's jobs become completely obsoleted, with no useful "retraining" available since the total number of jobs has permanently gone down, we conclude that these people must therefore be drains on our society, and cut them off from the magic box, even though a surprisingly small amount of money is (in our semi-Box economy) already enough to survive.

    What I've talked about above is the problem -- namely, how to manage the transition between a work-based economy and a magic box economy. There have been many solutions proposed to this, and I'm not going to go into all of them now. (For the record, I suspect that the "universal basic income" approach is probably the simplest and best solution, although my mind is by no means made up)

    But it's come time to start thinking about this: As our wealth goes to infinity, how do we avoid starving to death?

    (Image by ILO/Aaron Santos: https://flic.kr/p/hJVSyL)
  • 258 plusses - 194 comments - 149 shares | Read in G+
  • Yonatan Zunger2014-04-11 08:05:02
    RESHARE:
    XKCD gives a simple, clear, and very accurate explanation of how the Heartbleed bug works. The code which had this bug, unfortunately, is a core part of how servers create secure connections, which means that almost every server on the Internet had this vulnerability. 

    via +God Emperor Lionel Lauer.

    Reshared text:
    Heartbleed in pictures.

    This is the most accessible explanation yet, from xkcd.

    http://m.xkcd.com/1354/

    #Heartbleed #xkcd #security
  • 386 plusses - 71 comments - 120 shares | Read in G+
  • Yonatan Zunger2014-01-15 01:25:46
    When you freeze water, it expands -- this is an important and unusual property of water, since most substances are denser as solids than as liquids, and so a given weight of them is smaller when it solidifies. In fact, this tendency to expand is remarkably forceful, and if you try to freeze water in a box which doesn't give it room to expand, you're going to need a new box.

    No, really. This article tells you about some of the experiments people tried with this (e.g., sealing them in artillery shells; when the water finally froze, their cast-iron plugs ended up flying away at remarkable speed). The reason it doesn't, ultimately, work, is that ordinary ice -- what's technically known as "Ice-1" -- is just plain bigger than water, and the only way to make it smaller is to put enough pressure on it that the molecular structure of the ice changes. At a pressure of 1,736 atmospheres, it transforms into "Ice-II," which is denser than water: instead of forming hexagonal cells (the same hexagons which lead ordinary ice to form hexagonal snowflakes), the water molecules now arrange themselves into slanted rectangular prisms. 

    It turns out that ice actually has more than a dozen such forms, each with different physical and chemical properties; Ice-XV, for example, resists holding any kind of electrical charge, and the as-yet-uncreated (and unnamed) forms of ice above a pressure of 10 million atmospheres would be metallic. 

    h/t +Alex Scrivener and +Keith Wilson for the link.
  • 304 plusses - 48 comments - 173 shares | Read in G+
  • Yonatan Zunger2013-08-10 21:03:25
    RESHARE:
    A little fairy tale to start off your Saturday. (From steaksmoothie.com, by Joe Harden)

    Reshared text:
    Umirem.
  • 405 plusses - 57 comments - 94 shares | Read in G+
  • Yonatan Zunger2014-04-01 04:08:08
    Forget view counts. We know what really drives engagement on Google+: Photos. And we've always worked hard to make your photos awesome. But today, we can truly say that we're doing better than that: We can make your photos Hoffsome.

    Starting today, the power of Google+ will allow internationally renowned actor +David Hasselhoff to photo-bomb any one of your pictures. Why share a mere image of yourself with your spouse, your children, the President of the United States, when you can share one with the famed Baywatch star?

    And as an added bonus, when you tag +David Hasselhoff into your conversations, he will now show up with some words of wisdom.

    Google+: providing you the features that other social networks can only dream of.

    #AutoHoffSome  
  • 405 plusses - 62 comments - 83 shares | Read in G+
  • Yonatan Zunger2014-02-25 04:02:57
    RESHARE:
    Here is something truly extraordinary for you. The GIF shows a closeup animation of how DNA is copied. The extremely complex machinery that you see moving, with its spinning rotors and multiple arms, is a single large molecule known as DNA polymerase; its central rotor, a device known as the "replication fork" which splits the DNA strand into two, is spinning at 30,000RPM or more. (For comparison, the rotor of a jet engine at takeoff is generally spinning at 10-15,000RPM) 

    Click through to the video to see even more awesomeness.

    Reshared text:
    This is an animation of DNA replication by DNA polymerase and accurately shows the function of all its subunits.

    Source: http://youtu.be/OjPcT1uUZiE

    h/t: chemistrydoc
  • 334 plusses - 91 comments - 105 shares | Read in G+
  • Yonatan Zunger2013-11-06 20:45:03
    New YouTube Comments Rolling Out Today!

    As promised a few weeks ago, we are now rolling out the new YouTube commenting system. I've been using it in test for a while now, and I can tell you that it's a really different experience -- instead of "whoever speaks last speaking loudest," as one of our team put it, you see conversations involving your friends, involving interesting people, involving real engagement.* For channel owners, we're offering a whole host of new tools to moderate the conversation and create the environment you want on your videos. 

    This is a launch that's been a long time in the making, and is something I'm tremendously excited about. Many thanks to all of the teams who worked on it!

    http://youtube-global.blogspot.com/2013/11/youtube-new-comments.html

    * And since I know everyone's going to ask, we take into account everything from social proximity, to general interestingness of person and text, to freshness, so you won't see a bubble of just your friends and someone's notion of "important people." And you can also switch to "newest first" mode and see the raw firehose of everything, in time order.
  • 199 plusses - 292 comments - 97 shares | Read in G+
  • Yonatan Zunger2014-03-05 06:31:11
    Have you ever wondered how the Internet flows? Here are a couple of fantastic maps: of transoceanic cables and of public Internet links. 

    The first one (http://submarine-cable-map-2014.telegeography.com/) shows the lines that span the oceans; these are where almost all of the data flows from country to country. (Satellites are actually far less useful in the modern age; their bandwidth is a small fraction of what cables can provide) Fishing nets and ship anchors are the biggest threats to their day-to-day function, and for countries which only have one or two links, a single accident can easily have a huge impact. While it may not surprise you that much of Africa and South Asia are poorly connected, you may be surprised at how few lines flow in to Australia.

    The second map (http://global-internet-map-2012.telegeography.com/) shows public interconnect lines and bandwidth. This map is a bit older (2012) but it shows a lot of the real connectivity problems very vividly: North America, Europe, and the Middle East are well-connected, but Asia (except for a few major cities), Africa, and South America fare much worse. To see the real problems, zoom in carefully and try to trace (say) the shortest route you can find from Mumbai to Bangalore. You're not hallucinating: It's via Singapore. This is actually a big improvement; until a few years ago, it was via Zurich. In South Asia and South America, ISPs are sort of infamous for saying "this neighboring ISP is my competitor! Why would I peer [connect networks] with them?" In the rest of the world, everyone connects with everyone -- that's why the network is fast and robust.

    I'm not sure if this second map includes private networks or not; I suspect it doesn't, which actually hides a huge fraction of the Internet which you use. For example, when you connect to Google, you're really connecting to the nearest Google endpoint, and then all of the rest of the traffic (to wherever your e-mails, posts, videos, and so on are living) is routed over a very big network that we run -- and which is much faster than the public network, because it's used by a single organization which can carefully control and synchronize traffic.

    h/t +Kristin Milton for leading me to these.
  • 309 plusses - 39 comments - 143 shares | Read in G+
  • Yonatan Zunger2014-04-16 20:35:00
    This may seem more shocking to you than it actually is. The four Gospels of the canonical New Testament were never the only four; they were selected from a wide range of gospels ("god-spels," i.e. "good stories," a translation of the Greek "evangelion") by a series of meetings of bishops between the 2nd and 5th centuries. That selection process never pretended to be impartial: it was focused on picking gospels which gave a story which was consistent with a particular view of the role of the church and of priesthood in particular. (Irenaeus, one of the leading figures in this process, wrote a good deal about it in his book Adversus Haereses)

    Today, we know of roughly two dozen ancient gospels. (There are certainly many more) The ones which were rejected tended to fall into a few major categories: "Wisdom gospels," such as the Gospel of Thomas, which are essentially collections of Jesus sayings, were rejected both for lack of narrative and because their emphasis was rather personal rather than on the social fabric of the Church. Mystical gospels (many of which are often called "Gnostic Gospels," for rather complicated but boring reasons; they aren't actually Gnostic) tended to emphasize the miraculous powers which come with holiness, and these got excluded as part of the larger struggle for political power between urban and rural elites.*

    A common theme in many of the Gnostic gospels is the various other disciples of Jesus. A number of them, for example, refer to Mary Magdalene as one of his disciples, and shall we say strongly hint that she was his wife. (Which would have been perfectly consistent with the norms of the day; most men married, and being married was a near-requirement for rabbis)

    So the existence of an ancient manuscript mentioning the wife of Jesus isn't actually unusual in the larger scope of gospels. It doesn't mean anything in particular about its truth: remember that the oldest gospel (Didymos Thomas) was written 30 years after Jesus' death, and many of the later ones (such as John) were written over a century after that. 

    As with any historical text, the only thing you can really trust about it is that it had a writer who had an audience in mind, and you can learn a lot about how that writer saw the world and believed that his audience did as well. (Which is just as true for all of the other gospels!) There was definitely a strain of belief in Egypt around the second century that Jesus had a wife who was also a disciple, and this was almost certainly identified with Mary Magdalene. 

    So if you see this story, it's not earth-shakingly revolutionary, but it is an interesting further piece in the puzzle of how religious belief (and the associated social movements) evolved in the first few centuries CE in Europe. Which is a pretty fascinating topic.

    * If you want to know the story: starting around the 3rd century, as centralized Roman political power started to fall apart, local elites became more important power centers. The church became the political structure which unified them. In the cities, the leading power figure was the bishop, with his various priests, churches, etc. (Especially in the earlier days, this didn't mean so much that being the bishop made you powerful as that if you were powerful, you likely became the bishop.) In the countryside, where there weren't enough centralized people to form formal hierarchies of that scale, power instead tended to congregate around local holy men, whose authority derived from their general reputation for holiness. This tradition really started in Egypt, which was the breadbasket of the Empire and which had a very long history of holy men living in deserts, and this evolved into monastic orders. Bishops and monks proceeded to fight over power for the next thousand years. 

    A key issue which came up early on is what's called the "Arian Heresy." From a very technical perspective, the Arian controversy was over whether Jesus and God are of the "same substance" or "similar substance." You wouldn't think that an issue this subtle would lead to Empire-spanning riots and the near collapse of government, but it did. The real issue was this: if Jesus and God are of the "same substance," then Jesus' appointment of Peter as his successor (as the canonical gospels tell us) is a direct divine appointment, which means that priests have divinely granted power and are therefore different from monks, who don't. That means that an argument for the same substance is really an argument for urban power, often centralized in Rome, and an argument for different substance (which came to be known as the Arian Heresy, after a council of bishops decided that this was wrong) was an argument for rural power and specifically for power in Egypt. And that was something people would get very upset about. 

    And this is why the canonical gospels -- chosen by bishops, mind you -- are so pro-priest and pro-a certain notion of the divinity of Jesus.

    If you want to know more about this early power struggle, I recommend Peter Brown's The Cult of the Saints (http://www.amazon.com/The-Cult-Saints-Christianity-Religions/dp/0226076229).

    If you want to know more about the Gospels, these two Wikipedia articles are a good place to start:

    http://en.wikipedia.org/wiki/Gospel#Canonical_gospels
    http://en.wikipedia.org/wiki/List_of_Gospels

    If you want to actually read some of them, this is a good compendium and translation:

    http://www.amazon.com/Gnostic-Bible-Revised-Expanded/dp/1590306317/
  • 324 plusses - 105 comments - 104 shares | Read in G+
  • Yonatan Zunger2013-09-18 06:55:29
    Every so often, someone on the Internet does something crazy awesome. Here's an a capella cover of Bohemian Rhapsody, with the lyrics rewritten to be entirely about string theory.

    (And yes, they are all quite correct, and reflect the development of string theory from the first working quantum field theories in the mid-20th-century up through the second superstring revolution in the 90's. Just in case you were trying to learn superstring theory from a music video, which obviously you're going to go do now, because why wouldn't you? I mean, Bohemian Rhapsody.)

    Thanks to +Bradley Horowitz for finding this piece of brilliance.
  • 283 plusses - 41 comments - 153 shares | Read in G+
  • Yonatan Zunger2014-02-08 09:33:52
    RESHARE:
    Fascinating: simply by adding two white lines, and letting the image either clip or not clip them, your eyes immediately start to process the image as 3D. Be sure to click on the link to see more examples.

    Via +Pierce Arner.

    Reshared text:
    Animations enhanced with 2 vertical lines for the full 3D effect

    Just came across this great collection (http://bit.ly/1o2Sf8p) of animated examples on how easy it is to trick your brain to make funny connections that your eyes are not really seeing :) Very cool!

    #opticalillusion   #illusion   #3deffects   #animatedgif   #3d
  • 364 plusses - 23 comments - 106 shares | Read in G+
  • Yonatan Zunger2013-07-06 02:38:52
    Remember the cops in Hawthorne who arrested a man for (legally) videotaping them, and then gunned down his dog and let it twitch to death in the street for barking at them? Apparently, they've been receiving death threats from around the nation. And they "have been pulled from street duty to avoid any confrontations with angry pet lovers."

    Not, you will note, pulled from street duty pending an investigation of wrongdoing on their part. Not pulled from street duty because they were arresting a man for trying to film them in the course of their uniformed and public duties, even though this is entirely legal. Not pulled from street duty because it is alarmingly clear that these men should not be wearing a badge or carrying a gun. No, they are being pulled merely to protect them from a public which is sufficiently outraged by their behavior that their very lives are in danger for showing their faces in the street.

    Are the police supposed to be able to do their jobs when they cannot command even this much respect from the public? Remember that the job of the police officer is one of the greatest public trusts we give -- they are trusted with tremendous powers of arrest, force, and legal standing. Whenever a police department has lost the respect of the public it claims to protect, it is no longer able to do its job.

    And from the incident and the official response, the only thing we can conclude is that it is not merely these three officers who were at fault, but their entire chain of command, who created the culture in which this could happen, and who after the fact have gone to lengths to protect them.

    It is not enough that these officers be removed from duty and held to account. The entire command structure must be held to account, up to and including the captain of the operations division and Chief Robert Fager. Whenever a police department finds itself in such utter disrepute as a consequence of its own actions, fixing that must be its highest priority. 
  • 266 plusses - 273 comments - 49 shares | Read in G+
  • Yonatan Zunger2013-11-05 06:17:40
    When I first heard about Helpouts, I wasn't sure what to make of it. A system for people to sell their face-to-face services over Hangouts? What would it be used for?

    It wasn't until I started hearing people telling me about ideas they had for it, like small business owners offering helpouts for people who need to (say) pick a phone or a piano, or teachers being able to teach classes from thousands of miles away, or even senior executives in major industries offering face time and advice for people who are starting up their own companies, that I realized just how wide the potential of this could be. And when I saw the interface to it, and how straightforward it was, I started to be convinced that this is something that could reach a really wide audience.

    I'm really looking forward to seeing the future of Helpouts. I think this is a technology which could grow into something huge. What we launched today is only a small first step -- when you use it, you'll notice all sorts of things which aren't there yet. But I think you can see which way this is going, and there's something tremendously exciting in our future.
  • 373 plusses - 60 comments - 72 shares | Read in G+
  • Yonatan Zunger2012-11-13 04:50:51
    A minor update for you all: Lots of people have gotten frustrated by the fact that, when you have more than 100 comments on a thread, you stop getting notified when people comment on it. We originally put that rule in to keep people from getting bombed with notifications if they comment on (say) one of +Robert Scoble's posts, but it makes it hard to have conversations. So we fixed it by making the algorithm smarter instead. New algorithm should now be live everywhere. Converse and enjoy.
  • 139 plusses - 481 comments - 26 shares | Read in G+
  • Yonatan Zunger2013-12-12 00:36:22
    RESHARE:
    OK, I know that the laws of physics really do work that way. Still, watching someone scoop up an invisible gas, pour it into a container, and have a physical reaction from that, seems like magic.

    Reshared text:
    Sulphur hexaflouride is much denser than air
  • 373 plusses - 46 comments - 73 shares | Read in G+
  • Yonatan Zunger2013-05-15 21:26:26
    Since several people have asked about this: If you want to see posts in a single column in the new Google+ UI, instead of in multiple columns, scroll to the top of your stream. To the right of your circles is a "More" menu. At the very bottom of that menu there's an option to switch between single- and multi-column mode.

    #googleplustips
  • 199 plusses - 156 comments - 129 shares | Read in G+
  • Yonatan Zunger2013-09-24 19:06:44
    Today I can finally tell you something about one of the big things that we've been working on. This is something I'm tremendously excited about -- we're rethinking commenting on YouTube to be about building communities among both viewers and creators. The blog post tells you some of the basics of what's going to happen, and we'll give more details at our creator event tonight.

    A tremendous amount of thought has gone into this, and into the things which make YouTube great and the things which make Google+ great. Today, we can start to show you the combination of these things, and how they can really work to make each other better.

    We're rolling this out on the discussion tab of YouTube, so you can experiment with it some and see how it's going to work, as of right now. It will be opt-out for YouTube channels who have merged during this public beta period, during which time we really want to get your feedback and comments, and will come to all of YouTube later this year. 

    Also, if you've been wondering why we've been asking you to merge your YouTube and Google+ accounts, this is it: it's because when the systems truly work together, you need to have an identity which works on both. Remember that when you merge, you can keep your identity: either a single identity for both YT and G+, or two separate identities, as you prefer.

    Many, many thanks to the team, who has been fantastic. :)

    Edited to add: You can read more here; these articles give lots more details of exactly what we're launching.

    http://www.theverge.com/2013/9/24/4766758/youtube-introduces-radical-redesign-of-comments-tied-to-google
    http://allthingsd.com/20130924/youtube-says-it-will-start-cleaning-up-its-comments-and-making-them-more-personal/
    http://techcrunch.com/2013/09/24/youtube-announces-a-new-google-powered-commenting-system/
    http://gizmodo.com/youtube-comments-will-soon-be-less-racist-homophobic-1377565582
  • 275 plusses - 172 comments - 73 shares | Read in G+
  • Yonatan Zunger2014-01-30 19:52:07
    RESHARE:
    I can't help watching this, over and over. Both men's speed is phenomenal -- Michael Dokes' arms are moving with such perfect fluidity, such speed, and nevertheless wherever his hands are, Muhammad Ali isn't. 

    And then Ali does a dance, just because he can.

    #GOAT  

    via +Gary Walker.

    Reshared text:
    Muhammad Ali Dodges 21 Punches in 10 Seconds
    ...and does a cute little dance LIKE A BOSS.

    #boxing   #gifoftheday   #gif   #animatedgif  
    Src: http://goo.gl/Q4c1dM
  • 346 plusses - 40 comments - 87 shares | Read in G+
  • Yonatan Zunger2013-08-29 22:48:19
    RESHARE:
    Yeah, yeah, I know. This post does not have any particularly deep intellectual connotations. Instead, it's an owl, because (a) owls are cool and (b) this owl looks like a muppet.

    What can I say? It's been a long day. Enjoy your owl.

    via +Lisa Borel.

    Reshared text:
  • 403 plusses - 47 comments - 44 shares | Read in G+
  • Yonatan Zunger2014-01-06 20:16:15
    You may not be aware that the FBI no longer considers itself to primarily be a law enforcement agency. At some point in the last year, it updated its official documentation to reflect that it now considers itself to be, first and foremost, a "national security" agency. When asked about the change by Foreign Policy's John Hudson, FBI spokesman Paul Bresson explained that this reflected a change in the Bureau's mission post-9/11, when they evaluated their top ten priorities, the top three were "[counterterrorism], counterintelligence, and cyber [security]." The change in their documentation simply publicly reflects this shift - which has also included a large-scale transfer of manpower from criminal investigation, both white-collar and violent, to secret investigations in the "security" sphere. The consequences are significant: white-collar prosecutions dropped from 10,000 per year to 3,500 per year from 2000 to 2005. (Interestingly, around the time that the mortgage industry skullduggery was heating up)

    Now, I may be old-fashioned, but I think there's a certain value to the United States having a federal law-enforcement agency, especially with the wide variety of complex new crimes that have arisen in the past decades. I'm far less convinced that the US needs its own Second Directorate, a police agency dedicated to secret investigations of a sort which might result in "detention," but rarely prosecution. The argument that these are unprosecutable because of the sensitivity of methods is, more and more, an argument that the secret investigations of police must never be examined, because the police must remain secret.

    I've seen secret police organizations before. I've even seen ones calling themselves departments, ministries, committees, and bureaus of national, state, and homeland security. Last time I checked, they were what America spent most of the twentieth century fighting. Did we just decide to chuck it all and say, "Hey, USSR - looks like you were right after all. Sorry about the whole 'democracy' bit. Hey, can you give us some tips on infiltration?"

    I sure as hell didn't. And I hope you didn't, either.

    h/t +Alex Scrivener for finding the story. 
  • 291 plusses - 47 comments - 111 shares | Read in G+
  • Yonatan Zunger2014-04-04 21:58:32
    RESHARE:
    Aside from the use of the word "impactive" (really? You felt a need to make this into a word?) this is some very good advice for how to make tables more readable. And readable data turns into people paying more attention to it.

    via +Chiu-Ki Chan.

    Reshared text:
    Wie Tabellen eigentlich aussehen sollten: 
  • 290 plusses - 63 comments - 101 shares | Read in G+
  • Yonatan Zunger2013-02-13 22:24:30
    Here's an amazing photo of a region of the Sun taken by Alan Friedman. The photo is taken through a filter which allows only a very narrow band of wavelengths through, in the Hydrogen-alpha band; this penetrates beneath the corona and shows the deeper chromosphere of the Sun, covered in fine "hairs" of plasma. Up in the sky above it is a detached prominence which erupted from the pit beneath it. 

    We're so used to thinking of the Sun as a bright, featureless orb that it can be shocking to look at it through filters which reveal its fine structures: layers of fine plasma hairs, million-mile-long rivers of fire, swirling currents, great arcs pulled by magnetic field and bending far above the surface. 

    http://lightsinthedark.wordpress.com/2011/03/07/detachable-prominence/
  • 349 plusses - 50 comments - 70 shares | Read in G+
  • Yonatan Zunger2013-09-12 08:13:51
    In case you haven't seen this yet... this is what YouTube is for. A chance to see trailers for the new, heart-pounding action movie - Monty Python and the Holy Grail.

    Wait, what?

    (via many) 
  • 239 plusses - 40 comments - 141 shares | Read in G+
  • Yonatan Zunger2014-03-01 21:41:56
    The top story in the NYT right now (http://nyti.ms/1eK5q67).

    This very distantly reminds me of the day when the USSR started to mass its tanks on the borders of Latvia, Lithuania, and Estonia -- in the heady days of Glasnost, they had started talking about independence, and as the army began to assemble, we all wondered, was the new openness of the past four years a dream? A fake? Would ideas of freedom or change be crushed the way Hungary was, the way Czechoslovakia was? 

    But that was a very different time -- days of promise and openness, and profound uncertainty mixed with hope. That tension was swept away in the torrent when the Berlin Wall came down, so suddenly and unexpectedly, and Lech Wałęsa came out and suggested that this would be a good time for Poland to have elections and the world became unrecognizable overnight.

    This is almost nothing like that. In real historical terms, it's more similar to the perpetual border questions between Armenia and Azerbaijan, or with South Ossetia, nestled between Georgia and Russia. Ukraine is profoundly demographically split, in no small part due to Stalin's habit of picking up ethnic groups and moving them around to create precisely this sort of situation: lands previously independent of Russia, now with large Russian populations that have every reason to actively want to remain part of the USSR and under Russian control. And all of the struggles in Ukraine ever since the USSR was shut down live in this shadow.

    Now Yanukovich has fled -- in Russia but far from Moscow, kept in Putin's reserve, in effect, in case it becomes useful to reinstall him somewhere -- and a new government in Ukraine is clearly anti-Russian, likely to want to ally themselves more closely with Europe: Putin's great bugaboo. (How many times has Russia threatened to cut off countries' fuel supplies, shut down their economies, cause "trouble" for them, if they got too close to Europe? The gradual failure of the Warsaw Pact was perhaps the greatest blow to Russia's geopolitical power, in its day)

    But even among the valuable sites of Ukraine, one stands out: the Crimean Peninsula, strategically located between the Black Sea and the Sea of Azov, site of so many critical battles in the past two centuries. It has had semi-autonomous power within the Ukraine nearly since that country's inception, something backed strongly by Russian force -- since Stalin ensured that this area would be majority-Russian, forcibly deporting most of its population to central Asia in 1944. 

    And now Russia has, in effect, invaded it. Russia would like to take all of Ukraine, and make it Russian territory, no doubt, but it's quite possible that Putin considers it to be an acceptable second choice for Ukraine to split in half, with Russia taking over the Russian-speaking regions -- which, not at all coincidentally, includes the entire Ukrainian coast.

    This will not be pretty. It's not going to turn into World War III -- nobody is insane enough to say "hey, let's start flinging nuclear weapons at each other!" over this -- but it's a significant turnover in just how far Russia is willing to go to assert its control over the areas which it considers to be its natural sphere of influence. And that's going to have repercussions throughout the former Soviet world, and beyond.

    A good map of the linguistic and cultural splits in Ukraine: http://www.businessinsider.com/this-map-explains-why-russia-is-invading-crimea-2014-3

    A good map of oil pipelines which flow through Ukraine, another of the reasons why it's so strategically critical: http://www.zerohedge.com/news/2014-02-20/ukraine-situation-explained-one-map

    Other key reasons being access to the Black Sea, its status as the major breadbasket of the Soviet world, and its strategic location for armies moving to and from the southwest.
  • 252 plusses - 178 comments - 67 shares | Read in G+
  • Yonatan Zunger2013-08-14 08:22:15
    Why yes, this is rocket science.

    Yesterday’s What If? (http://what-if.xkcd.com/58/) answered some great questions about why getting into space (and out of it again) is hard. But it left one reader question only partially answered, and that means I have a good excuse to talk about rocket science today. Kenny van de Maele asked, “Could a (small) rocket (with payload) be lifted to a high point in the atmosphere where it would only need a small rocket to get to escape velocity?” And as +Randall Munroe explained, most of the fuel you need for a rocket is needed to build up speed, not to punch through atmosphere. But it turns out that this is actually a good idea for other reasons.

    When you see a rocket take off, it looks like it’s going slowly -- but that’s an illusion simply because rockets are incredibly big. The space shuttle weighs about 2,200 tons at liftoff, about ten times the weight of the Statue of Liberty, and it pulls a maximum acceleration of 3g’s. (Which would take you from 0 to 60mph in 0.9 seconds) And when you accelerate through the air, the air pushes back, with a dynamic pressure that’s proportional to the density of air times the square of your speed.

    As you go up higher, the air gets a lot less dense: by the time you reach 20,000’, the air is less than half as dense as it is at sea level; by 35,000’, less than a quarter; by 50,000’, only ten percent. (This is why very high-altitude planes like the U-2 need very special designs; there isn’t enough air to hold them up) But since pressure goes up as the square of the velocity, and you need to fight through this pressure as you take off, it’s a really bad idea to build up too much velocity until you’re clear of the worst of the atmosphere. This is why spaceships take off vertically instead of horizontally: even though what you really want, if you’re trying to get into space, is to build up about 8km/s of horizontal speed, the best way to get a rocket up is to shoot up vertically as fast as you can, and climb up to 26,000’ or so before turning East (to take advantage of the extra rotation you get from the Earth itself) and thrusting like mad. 

    But since you start out at zero speed and increase, and since you start out at high pressure and decrease, somewhere in the middle that pressure is going to max out. This is called “max Q,” the moment of maximum dynamic pressure -- the moment at which the airframe is under the greatest aerodynamic stress it will experience during the flight. For a Space Shuttle, this happens about one minute after takeoff, with all the boosters and tanks still attached, and the peak pressure is about 5.2psi; this is the overpressure you associate with large bomb blasts, at which “Most buildings collapse. Injuries are universal, fatalities are widespread,” in the words of the Nuclear Weapons FAQ. Yet this device, the size of ten Statues of Liberty, has to survive it unscathed, with a payload full of people and delicate equipment. The Shuttle survives this, in part, by cutting back to 70% throttle while it ploughs through this; past max-Q, it turns the engines up to full open and heads for the stars.

    Needless to say, surviving max-Q is one of the major objectives of a successful launch. Apart from simply barrelling upwards, there are other techniques people have tried. One is a “drop-launch,” in the style of SpaceShipOne or the X-15, where the spaceship is carried to high altitude by a mothership (e.g. a B-52) and then dropped, to fire its rocket engines horizontally as soon as it gets clear. The aircraft (or occasionally, even balloon) can gain altitude slowly, without worrying about a dangerous max-Q, and then the spaceship can start out where the air is already thin and clear. The biggest problem with this approach is that the size of the spacecraft is limited by the size of the mothership; an airplane that could carry a fully-loaded Space Shuttle would be a rather impressive, not to mention impractical, sight. 

    Another approach is to make the spacecraft itself into an airplane, and have it take off in the usual way. The challenge with this is designing the engines: if you use rocket engines from the beginning, you’ve just returned to the problem you started with, but ordinary aircraft engines are unbelievably heavy things for a spaceship to have to carry around, and aren’t particularly aerodynamic at hypersonic speeds. There is therefore a great deal of interest in engines which can work effectively at a range of speeds; for example, the SABRE engine currently in development could take a craft from a standstill up to Mach 5, at which point traditional rocket engines could take over. (The article linked below gives a great summary of the challenges of building a spaceplane)

    But in short, it turns out that it is in fact very useful to lift your rocket up to a high point in the atmosphere in order to launch it: not because you need to acquire less velocity, but because you have less atmosphere to deal with. And as they say in the space biz, mo’ atmosphere, mo’ problems.

    Further Reading
    A video of the Discovery taking off:
    Space Shuttle Launch Audio - play LOUD (no music) HD 1080p
    The trajectory of a Shuttle, if you want to know the details: 
    http://spaceflightnow.com/shuttle/sts135/fdf/135ascent.html
    How air pressure drops with altitude:
    http://www.engineeringtoolbox.com/air-altitude-pressure-d_462.html
    Max-Q (not to be confused with Max Headroom):
    http://en.wikipedia.org/wiki/Max_Q

    If you want to know about things which go “boom,” there’s nothing better than Carey Sublette’s Nuclear Weapons FAQ:
    http://nuclearweaponarchive.org/Nwfaq/Nfaq5.html

    The North American X-15, the fastest manned aircraft ever flown:
    http://en.wikipedia.org/wiki/North_American_X-15
    The basics of the Space Shuttle itself:
    http://en.wikipedia.org/wiki/Space_Shuttle

    And an update about the SABRE engine:
    http://www.theguardian.com/science/across-the-universe/2013/jul/17/sabre-rocket-engine-reaction-skylon

    #Science #Space  
  • 288 plusses - 64 comments - 93 shares | Read in G+
  • Yonatan Zunger2013-08-12 20:17:20
    As we continue to get confirmations that not only is Russia sticking by its new laws, but that it is openly encouraging mass violence, and that it intends fully to enforce these laws against all present at the Olympics -- imprisoning (and potentially also beating and killing, if the past few weeks are any indication), among others, any athlete who is seen with their same-sex spouse, or any journalist who interviews an athlete who says anything perceived as pro-gay.

    Given that it is now clear that the IOC cannot make even basic guarantees of the safety of athletes, reporters, and spectators at the event, it does not appear to me that it is in any way reasonable to continue the planning for this event -- nor for any other event in Russia.

    Stephen Fry suggested that the Olympics be rerouted elsewhere. I don't believe that this is logistically possible at this point; an event of the scale of the Olympics would require a one-year lead time to prepare for, even in a city which already had the infrastructure ready from previous Olympics.

    I therefore believe that the only reasonable course of action at this time is to cancel the 2014 Olympic Games entirely. Russia has failed (dramatically) in its most basic duties as a host country, and the situation it has created is no less dangerous than if a war were raging in the area selected. 

    I recognize that the IOC is highly unlikely to do this; there is a great deal of money at stake, and quite frankly the IOC is not famous for caring about anything other than that. The onus will likely therefore fall upon the member states. Fortunately, it is easy for a state to shut this down: one can simply refuse to participate in games under these circumstances. 

    Russia's decision to descend further into barbarism should not oblige the rest of the world to smile, nod, and acquiesce, much less to put its citizens -- especially the ones it chooses to represent it at an international event -- in grave danger in order to do so.
  • 185 plusses - 177 comments - 104 shares | Read in G+
  • Yonatan Zunger2014-02-20 01:25:46
    RESHARE:
    I'm a dedicated vim user, but I have to admit that this is rather on the mark.*

    * Not that EMACS has anything to brag about in this regard, either.

    Reshared text:
    Something we always keep in mind while developing mobile apps and websites for our clients..
  • 323 plusses - 117 comments - 46 shares | Read in G+
  • Yonatan Zunger2013-10-28 00:18:02
    RESHARE:
    OK, that wins.

    Reshared text:
    This air show really outdid themselves.
  • 379 plusses - 22 comments - 54 shares | Read in G+
  • Yonatan Zunger2012-12-06 17:12:26
    We have several things to announce today at Google+ that I'm incredibly excited about. The first one is Google+ Communities. A lot of people have been saying that sharing circles wasn't really what they wanted: they wanted a way to have a group of people that people could join, talk with, form a community with. Today we're starting to roll out that feature to all of our users. You can form communities ranging from completely public (anyone can join, anyone can see what's happening) to completely private (need approval to join, membership lists are kept secret, nothing leaks out of the community), so they're meant to serve a wide variety of needs. This product is still very much in Beta, so please try it out, see how it works, and give us feedback: we want to know what should improve!

    The second is something for the photo world. Google recently acquired Nik Software, maker of both some very serious high-end photography software and some very neat cell phone software. Today we have an announcement on the cell phone front: Snapseed for Android is now available in the Play Store. Snapseed brings you some amazingly sophisticated filters and tools which are shockingly easy to use. It's a great deal of fun and I recommend you try it out. (There's already an iOS version for those of you with such devices)

    And finally, we have some numbers to announce about the size of the Google+ community. As of today, Google+ has over half a billion users; 235 million active users, visiting some social aspect of Google; and 135 million people who are actively using the stream alone, visiting plus.google.com to read and share things with the people they know. It's been an amazing first year and a half, where we've gone from "I really hope this works..." to having the equivalent of the population of a major country showing up on a regular basis to talk with one another. We've started to really see Google+ shine as both a place to talk very privately – all of those conversations that you don't see, because they're between small groups of friends or family – and very publicly, sharing photos, long-form text, and so on. It's become a place where a lot of people can meet, and I've been lucky enough to make a great many friends through the service. And in the next year, I hope that we can make it even more so, with more features, more people, and more community among our many users.
  • 151 plusses - 288 comments - 70 shares | Read in G+
  • Yonatan Zunger2013-08-23 18:27:21
    This is nonsense, but it's nonsense in an interesting way.

    This post has been getting shared around the internet a good deal today, mostly in a rather thoughtless way. It's a great excuse for people to go "hur hur -- look at yer stoopid book!," but really, what this is illustrating is something much deeper, which people of all faiths (and non-faiths) often miss: the Bible is not a single book. 

    Take the Torah, for example, the first five volumes of the Hebrew Bible, and the oldest layer of the text. It started out as two separate texts, known as "J" and "E," written in the southern area of Judah and the northern area of Israel respectively, ca 950BCE and 850BCE. (They get their names from the different names used for God in them: J uses YHWH ("Jehovah" in German, thus J) and E uses Elohim. This has deep roots in the fact that the two regions historically had different religions, and Judaism emerged in part from their fusion) These two texts were merged into a single text by an editor who made various changes in both to merge them, a few hundred years later; then further texts were added by a priestly author (P) in a very different context of having serious political authority, and more editing happened, etc. (If you want to see a good snapshot of this, I recommend The Bible With Sources Revealed, which is a Torah highlighted and color-coded by our best estimate of who wrote each line)

    Later texts get even more interesting. Job was written by three different people, who proceeded to have an argument over how to interpret the existence of evil by means of injecting their own bits into the same book. (If you want to read this book, I suggest The Wisdom Books, below, for its introductions that give you a good map of what's going on; the mutually contradictory opinions jammed in there by force make it really hard to follow otherwise) 

    The Christian texts have an even more varied history. To date, we know of 27 different Gospels, and more epistles and apocalypses than I can easily count. The decision of which of these books would be made "canonical" was an intensely political one, made over several centuries, driven primarily by the needs of bishops and emperors. The choice of the four canonical gospels, for example, was very specific: these were the gospels which gave the strongest support to the significance of the priesthood, to the orthodox view that the Son and the Father are "of the same substance," and therefore that the appointment of Peter and his successors as priests was divinely ordained, etc. Entire categories of texts, such as "wisdom gospels" (basically, collections of Jesus sayings, like the Gospel of Thomas), or mystical gospels (ones which focus more on personal holiness and the powers which derive from it, like Valentinus or Mary Magdalene) were excluded. The Revelation of St. John was put in because there was a huge fashion for apocalypses at the time, and there was a decision to pick one as canonical to end the fight over dueling revelations.

    In short, there is not, nor has there ever been, a way to think of the Bible as a single book with a single, consistent story or a single, consistent view. Rather, the Bible is the record of a centuries-long argument over the nature of the divine and the nature of humanity, mixed in with all sorts of other things: folk tales from Sumer (most of Genesis up to and including the Flood, except for the family history bits, is lifted straight from Sumerian texts, and you can find their cousins in the library at Nineveh), family history, political arguments including praise and criticism of the people who were in power at the time that the various books were being written, etc.

    If you try to read the Bible as a single consistent thread, you will either have to ignore half of what you read, twist yourself into knots to claim logic, or have your head explode. But if you read this book as a slice through a long and complex history, you'll start to see the tremendous richness of centuries of human life.

    Consider it this way: the Hebrew texts were edited in a few major layers, during the first Monarchy, during the periods of civil war which followed the first Monarchy, and with many addenda written in the Babylonian and post-Babylonian periods. The parts about the Monarchy itself -- about David and Solomon and so on -- were written in the immediate aftermath of their lives, with the country in the midst of perpetual civil war between their various successors. Yet people were writing about the "founders of their country" -- and said founders do not always come off particularly well in the story. (cf: pretty much anything involving Saul or Batsheba) 

    The infinite chains of begats and the stories of Abraham and so on are raw family history: it's literally a family's logbook of important events as they went from living in Ur to making a play for nationhood. And the family is sometimes sane, sometimes crazy. (I'm related to these people. Believe me, the family is sometimes crazy.)

    The "wisdom literature" -- the proverbs, Ecclesiastes, the Song of Songs -- is a bunch of text added on later, by people who were trying to understand the true meaning and nature of life. They did not have a perspective anything like most preachers you will encounter today; how many churches are going to tell you that life happens for reasons we can never really fathom, that sometimes evil wins over good, that everything we do is probably ultimately futile anyway, and so the best we can do is live fully but humbly, and enjoy the day? 

    Open up the Christian texts; better yet, go beyond the canonical ones and pick up Thomas. Look at the older gospels, at Mark and Matthew, before Paul showed up and started to turn this into a new religion. Read Jesus' words in the context of his own life: a radical reformer within Judaism, preaching against the formalism and the dedication to ritual and the deep integration with political power which had come to define the world around him, preaching instead that the path to the kingdom of heaven is through feeding the hungry and dedicating yourself to a life of service to others. Then read Paul's letters, watch him trying to apply his life of organization to building a whole new society, trying to express to nascent churches how they can form a community and make it work even as things change. (But read carefully! Some of Paul's letters are actually later forgeries, inserted by others. Ehrman's book is a good summary of where to be careful)

    There is no "Biblical view" of anything, because there is no single hand behind the Bible. There are dozens, hundreds of views, and they are arguing with each other. Of course the book is full of contradictions; it was never meant to represent a consensus!


    Further reading: 
    The Bible With Sources Revealed: http://www.amazon.com/Sources-Revealed-Richard-Elliott-Friedman/dp/006073065X
    The Wisdom Books: Job, Proverbs, and Ecclesiastes: A Translation with Commentary http://www.amazon.com/The-Wisdom-Books-Ecclesiastes-Translation/dp/0393340538
    Ehrman on forgery and injection of texts into the Christian works: http://www.amazon.com/Lost-Christianities-Battles-Scripture-Faiths/dp/0195182499/ref=sr_1_7?s=books&ie=UTF8&qid=1377282384&sr=1-7http://www.amazon.com/Misquoting-Jesus-Story-Behind-Changed/dp/0060859512/ref=sr_1_1?s=books&ie=UTF8&qid=1377282383&sr=1-1 .
  • 156 plusses - 249 comments - 84 shares | Read in G+
  • Yonatan Zunger2013-08-07 04:43:59
    RESHARE:
    Never let it be said that I unfairly shun posting inspirational quotes. This one, for example, reminds us that even the most difficult problems can have more than one solution. See? I'm feeling inspired already.

    Reshared text:
  • 294 plusses - 115 comments - 56 shares | Read in G+
  • Yonatan Zunger2013-12-05 06:36:08
    RESHARE:
    I love watching devices like this. This turns a simple rotational motion (input, along the big gear's axle) into rotating a certain number of degrees in one direction, then a different number in the opposite direction. (The exact amounts being adjustable by setting the number of teeth on each of the three surfaces) These are the parts mechanical computers are built from.

    via +Susan Beebe 

    Reshared text:
    Bi-Directional Gear
  • 345 plusses - 28 comments - 57 shares | Read in G+
  • Yonatan Zunger2014-03-25 00:40:55
    RESHARE:
    Jimmy Wales says it perfectly. 

    Reshared text:
    Jimmy Wales of Wikipedia responds to ridiculous petition seeking to force Wikipedia to take pseudoscience at face value.
    http://www.change.org/petitions/jimmy-wales-founder-of-wikipedia-create-and-enforce-new-policies-that-allow-for-true-scientific-discourse-about-holistic-approaches-to-healing/responses/11054
    Via +David Gerard 
    #wikipedia   #alternativemedicine   #woowoo   #pseudoscience  
  • 340 plusses - 43 comments - 52 shares | Read in G+
  • Yonatan Zunger2014-01-05 18:39:25
    RESHARE:
    I wholeheartedly approve.

    via +Bliss Morgan

    Reshared text:
    Library, Hopkinton, Massachusetts
    http://imgur.com/pOuUPES
  • 381 plusses - 24 comments - 32 shares | Read in G+
  • Yonatan Zunger2013-11-15 17:26:27
    RESHARE:
    Inductive heating: one of those things that seems like magic no matter how many times you watch it. What's happening here is that a strong electric current is running through the copper coils (big tubes so that cooling water can run through them, and the entire furnace doesn't explode), which is creating a magnetic field in the chunk of metal in the middle. That magnetic field causes small eddy currents to flow inside the piece of metal -- but "small" is a relative thing, and those currents plus the electrical resistance of the metal make it heat up. A lot. 

    via +Aaron Wood.

    Reshared text:
    Melting steel with copper tubing: When a strong electric current runs through the copper, it acts as an electromagnet, holding the steel slug aloft. Then the electrical resistance of the steel converts part of the electrical energy into heat. Quiet a lot of heat.
    #scifunonfilm  
  • 284 plusses - 61 comments - 74 shares | Read in G+
  • Yonatan Zunger2014-02-07 05:42:16
    Such grammar. Very language. So mismatch. Much analyze. Wow. 
  • 220 plusses - 63 comments - 112 shares | Read in G+
  • Yonatan Zunger2013-06-11 18:36:53
    Our chief legal officer, +David Drummond, sent a letter to the Attorney General and the Director of the FBI today, asking the government to lift its restrictions on what we can say. As he says, we have nothing to hide -- and I personally welcome as much openness as possible.

    Simultaneously, a bipartisan group of eight senators has proposed a bill to declassify FISA court rulings: http://www.theverge.com/2013/6/11/4419006/senate-bill-would-declassify-fisc-orders-for-nsa-surveillance

    I'm entirely in favor of all of this. The scandal in this case is not that the NSA may have broken the law -- it's that they very likely did not. It's that the law of the land has gradually mutated into something that allows us to be watched 24/7, at the whims of people unknown, subject to safeguards unknown, for reasons unknown -- but keeping a log, so that if anyone ever becomes suspicious of us in the future, they can easily go back and see a full record of everything we've ever done. 

    The government has argued that this is necessary in order to protect the country. But we can't have that argument -- the talk about what freedoms we're losing, what security we're gaining, and what's worth it -- if both the things we're losing and the things we're gaining are kept secret. This isn't a small, obscure corner of policy which can be governed safely by small groups of specially-cleared senators. It goes right to the heart of what we are as a country.

    I've heard a lot of arguments in the past day or so that this surveillance is perfectly legal, so we shouldn't worry about it. That's backwards: it's legal because Congress hasn't passed laws about it, and Congress can't pass laws about something they themselves don't know about. Much less things the people don't know to demand they pass laws about.

    I've also heard the argument that, if this surveillance has saved so much as a single American life, it's worth it. That's even more backwards. How often do people say that the people of Iran should rise up against their government, or that no sacrifice was too great against Communism? Not every bit of security is worth arbitrarily much freedom. We have to make the choice ourselves, and we have to make it knowingly. I'll take the dangers of living in a free country over the safety of living in prison.
  • 254 plusses - 88 comments - 78 shares | Read in G+
  • Yonatan Zunger2013-11-05 20:49:51
    You need to stop and watch this video. It's about an automaton built in the late 1770's, shaped like a small boy. It writes, programmably, in an elegant cursive script, using a goose quill. On its back is a dial which stores the program; around the dial is a sequence of blocks, one for each letter, which can be arranged by the user and which tell it what to write. Vertically in the center of the device is a stack of hundreds of cam wheels, which encode the "font;" each letter is encoded by a set of three wheels which encode the three-dimensional (yes, including pressure) motion of the pen.

    It still works to this day, and in the video you can watch it write. The attention to detail in this is truly extraordinary; it refills the pen and shakes the quill, moves the page and moves its eyes to track what it is writing. This is truly one of the great works of mechanical computation. The automaton, along with his other works, are on display at the Musée d'Art et d'Histoire in Neuchâtel, Switzerland.

    More about this ingenious device, and his other works, here: http://www.thisiscolossal.com/2013/11/the-writer-automata/

    via +Jennifer Ouellette and +Daniel Estrada.
  • 156 plusses - 39 comments - 160 shares | Read in G+
  • Yonatan Zunger2012-09-02 03:52:45
    Oh hey, we launched a minor feature yesterday that makes me happy: if you fill in the "Tagline" field on your profile, it now shows up on your hovercard. So that's a great place to put a few short words about yourself; it's the first thing most people will see about you, after your name and pic. The hovercard, if you haven't heard the word before, is the card that pops up when someone hovers over your name.

    (And thanks to the hovercards team!)
  • 205 plusses - 92 comments - 105 shares | Read in G+
  • Yonatan Zunger2012-01-23 21:02:03
    RESHARE:
    Hi everyone,

    Today we made a small but important step in allowing people to be known on Google+ in the way that they’re known in the rest of the world. I’m very happy to announce some updates to our names policy, and some associated new features of the service.

    We really appreciate all of the feedback that we’ve gotten around this issue: it’s from active, engaged and passionate users who care about getting these things right that we can build the strongest communities.

    As +Bradley Horowitz says below, this is not the end, only a milestone: We’re going to be watching and listening to feedback, and will continue to evolve this going forward.

    And now, finally, I can answer your questions. :)

    Reshared text:
    Toward a more inclusive naming policy for Google+

    With Google+, we aspire to make online sharing more like sharing in the real world. And during the Google+ signup process, we've asked users to select the name they commonly use in real life.

    Since launch we've listened closely to community feedback on our names policy, as well as reviewed our own data regarding signup completion. The vast majority of users sail through our signup process -- in fact, only about 0.1% submit name appeals.

    When we analyze the set of all name appeals on Google+, we find that they generally fall into three major categories:
    - The majority (60%) of these users want to simply add nicknames.
    - About 20% of appeals are actually businesses (who are inadvertently trying to set up their business as a Profile, rather than using Google+ Pages which were intended for this purpose.)
    - And the remaining 20% would either prefer to use a pseudonym or another unconventional name.

    Today we’re pleased to be launching features that will address and remedy the majority of these issues. To be clear - our work here isn’t done, but I’m really pleased to be shipping a milestone on our journey.

    Nicknames and Names in Another Script

    Over the next week, we’ll be adding support for alternate names – be they nicknames, maiden names, or names in another script – alongside your common name. This name will show up on your Google+ profile and in the hovercards which appear over your name. In the next few weeks, we’ll be displaying it more broadly as part of your name in other areas of Google+ as well. So if you’re Dwayne “The Rock” Johnson, Jane Doe (Smith), or Saurabh Sharma (सौरभ शर्मा), you can now communicate your identity the way you want to.

    To add an alternate name, go to your Google+ profile, click Edit Profile, select your name and click on “More options.” (See attached photos)

    It’s important to remember that when you change your name in Google+, you’re changing it across all services that require a Google Profile.

    Other Established Identities

    On Google+, we try to flag names which don’t represent individuals, such as businesses or abstract ideas which should be +Pages. Sometimes we get this wrong, so starting today we’re updating our policies and processes to broaden support for established pseudonyms, from +trench coat to +Madonna.

    If we flag the name you intend to use, you can provide us with information to help confirm your established identity. This might include:

    - References to an established identity offline in print media, news articles, etc- Scanned official documentation, such as a driver’s license
    - Proof of an established identity online with a meaningful following

    We’ll review the information and typically get back to you within a few days. We may also ask for further information, such as proof that you control a website you reference. While a name change is under review, your old name will continue to be displayed. For new accounts without an old name, your profile will be in a non-public, read-only state during the review. Either way, you'll be able to see the status of your review by going to your profile.

    For more details, check out the Google+ Names Policy: http://support.google.com/plus/bin/answer.py?hl=en&answer=1228271

    To reiterate, the features described herein will be rolling out over the next couple days.

    Today is a small step towards improving the ways in which you can communicate your identity on Google+. We will be listening to feedback from the community and will continue to refine all aspects of how we handle names and identity over the coming weeks, months and beyond.

    Thanks for your continuing feedback and support.

    Bradley and Team G+

    #googleplusupdate
  • 62 plusses - 460 comments - 25 shares | Read in G+
  • Yonatan Zunger2013-08-28 21:34:39
    RESHARE:
    At some point I'm going to write a real post on this, but for now let me just remind you of the basic rule of the Middle East: The enemy of my enemy is probably my enemy, too, but it's an enemy with whom I have at least one mutual objective. 

    Welcome to the Middle East and have a nice day.

    via +U-Ming Lee.

    Reshared text:
    An awesome summary of the situation in the Middle East right now. By @FT, via @minafayek(on Twitter).
  • 242 plusses - 99 comments - 76 shares | Read in G+
  • Yonatan Zunger2013-09-13 02:08:37
    The Sounds of Space

    You would think that interstellar space is silent. After all, in a vacuum, nobody can hear you scream... but interstellar space isn't a perfect vacuum. In fact, once you get out beyond the Solar System, and the Sun's protective field, there's actually more plasma than there is in the outer reaches of the Solar System: a whopping one electron per 13 cubic centimeters of space.

    OK, that's not a lot, but it's enough that you can have sound waves moving through the plasma, and enough that the very delicate ears of Voyager I could actually hear it. 

    And that's what brings up this story today: astrophysicists have finally reached a consensus that on August 25th, 2012, Voyager I did indeed leave the Solar System, becoming the first man-made object ever to sail beyond our shores. (I've always had a soft spot for the two Voyagers: they were launched only months before I was born, and so I've been growing up with their mission. So now I can look up at the sky and think, it's spacecraft like these who make you realize how little you've accomplished. Why, if I had started travelling when I was born, I could have left the Solar System by now...)

    The reason it took over a year to confirm that this had happened is that there isn't a big sign at the edge saying "You Are Now Leaving The Solar System; Come Again Soon!" But there is an actual edge to it, called the heliopause. The Sun emits a steady stream of particles called the Solar Wind; the heliopause is the point at which this stream breaks up against the interstellar wind, the stream of particles which flows through our galaxy. Inside the heliopause, the Sun's magnetic field keeps out many of the particles of the interstellar wind, so when you cross that line, you start to feel the somewhat more powerful currents of interstellar space. 

    Which brings me to the video below: a recording of the sounds heard by the Voyager, transposed up quite a few octaves so that you can hear them. These are the sounds of individual plasma waves crashing against the bow of the ship; the graph shown in the video shows the density of the wave vertically, and the time horizontally. 

    We've never explored this area before. We can look at it via telescope, but a telescope won't reveal sounds, won't reveal what particles are there. Voyager I is somewhat limited in what it can reveal, since it was designed not for this, but to explore the planets of our Solar System; it sent back extraordinary photos of Jupiter and Saturn (as its sister-ship, Voyager II, did of Saturn, Jupiter, Uranus, and Neptune) and its technology is rather fascinatingly archaic, running on 22W of total power and using an 8-track tape for storage. But it continues to fly, 35 years into its mission, and is now bringing us our first images of the world beyond the solar shores.

    For more information about the Voyagers:
    http://voyager.jpl.nasa.gov/
    http://voyager.jpl.nasa.gov/imagesvideo/imagesbyvoyager.html  (pictures!)
    http://en.wikipedia.org/wiki/Voyager_1
    http://en.wikipedia.org/wiki/Voyager_2

    The heliopause and the edge of the Solar System:
    http://en.wikipedia.org/wiki/Heliopause_(astronomy)#Heliopause

    Article about Voyager's exit, with links to more:
    http://blogs.scientificamerican.com/life-unbounded/2013/09/12/voyager-has-entered-the-interstellar-medium/
  • 250 plusses - 34 comments - 100 shares | Read in G+
  • Yonatan Zunger2013-05-09 18:24:03
    This is something I'm very happy to hear. My own feeling is that patents (and similar intellectual property rights) serve the purpose of encouraging innovation when they're in a field that's already mature, development is expensive, and people need time to recoup these costs. They hinder innovation when the field is in rapid flux, and any invention is likely to be independently produced by many people: at that point, it becomes a way for companies (and other IP holders) to draw arbitrary fences about what other people can and can't do, and demand fees for work that other people did on their own. Software is one such field. (Whereas refrigerators probably aren't)

    My own preferred reform would be to establish a 20-year moratorium on the granting of new patents for software, as well as a moratorium on causes of action emerging from such patents. We can look again in a few decades to see if the situation has changed enough to merit switching this.

    (I would also reform quite a few other things: e.g., I would explicitly mark business methods as non-patentable, and make quite a few reforms to copyright law as well. But those are separate matters)

    h/t to +Gary Walker and +Dirk Talamasca for the link.
  • 257 plusses - 63 comments - 80 shares | Read in G+
  • Yonatan Zunger2014-02-18 17:51:04
    RESHARE:
    We're used to seeing maps which paint the US as split between different groups. Around election seasons in particular, you'll see huge swaths of red and wonder how the country could ever be narrowly split -- unless, of course, you look at the country by population, and you realize that "square miles" makes a very poor map of where people are. 

    This is another good map which shows how far from uniform the country is: the orange areas shown account for 50% of the country's economy; the blue areas, the other 50%. (I'm not sure where Alaska and Hawaii fit in to this, but I'm guessing mostly blue)

    Increasingly, we're a country of cities which are densely populated, economic powerhouses, with a wide range of complex benefits and problems, and generally politically blue, and a sea of sparsely populated, much more locally homogenous areas, suffering from a loss of economic power and generally politically red. That's at the heart of a lot of US politics today.

    via +Aaron Wood .

    Reshared text:
    50% of the US economic strength is in the orange section. 50% is in the blue. To quote a civil engineer I am friends with (who really needs to come to the better service):

    "national economies are just grab-bags of city economies...and rural areas depend on urban productivity to survive. When cities get weak and stagnant, the entire country slides into deeper poverty--rural areas, by contrast, are stagnant by default, except when made prosperous by economic forces from cities: demand for resources, labor, etc."
  • 250 plusses - 86 comments - 72 shares | Read in G+
  • Yonatan Zunger2014-01-09 23:00:21
    RESHARE:
    Without a doubt, this is one of the most important scientific results of the year: an optimal chocolate chip cookie. The research also includes a bunch of results you can use to adjust this recipe in case you disagree about what optimality means.

    The final recipe is here: http://www.seriouseats.com/recipes/2013/12/the-food-lab-best-chocolate-chip-cookie-recipe.html

    Reshared text:
    The Food Lab baked 1,536 cookies to uncover the perfect chocolate chip cookie recipe

    "Cookies are fickle and the advice out there is conflicting. Does more sugar make for crisper cookies? What about brown versus white? Does it matter how I incorporate the chocolate chips or whether the flour is blended in or folded? How about the butter: cold, warm, or melted?"

    check out the science here:
    http://sweets.seriouseats.com/2013/12/the-food-lab-the-best-chocolate-chip-cookies.html
  • 219 plusses - 56 comments - 104 shares | Read in G+
  • Yonatan Zunger2014-01-08 01:28:26
    RESHARE:
    When something orbits a single body, like the Earth orbits the Sun or the Moon orbits the Earth, its trajectory is simple: it can only be a circle, an ellipse, a parabola, or a hyperbola. But when more than two bodies are involved, the trajectories can become fearfully complex, and generally end either with objects being flung away or crashing into one another.

    And, of course, they make for great animations. Here's a recently-discovered piece of space debris: the third-stage engine from Apollo XII.

    Reshared text:
    What goes around, comes around

    On September 3, 2002, an amateur astronomer named Bill Yeung looked into his telescope and discovered a strange object near Earth.  Experts were surprised to discover that it was orbiting Earth!  The orbit was unstable, which meant this object hadn't been here long.  But there was no recently launched spacecraft that matched the orbit of this thing!

    It got the name J002E3.  It's fun to watch this animated gif and see how J002E3 came in from the Lagrange point L1 between the Earth and Sun, went around the Earth a few times, and then got kicked out.

    But what was it?

    University of Arizona astronomers found that its electromagnetic spectrum was consistent with white titanium dioxide paint - the same paint used by NASA for the Saturn V rockets. Tracing back its orbit, they found that it had probably been orbiting the Sun for 31 years.  The last time it was near Earth was1971.

    This seemed to suggest that it was a part of the Apollo 14 mission. But NASA knew the whereabouts of all hardware used for this mission!  The third stage of that rocket, for example, was deliberately crashed into the Moon for seismic studies. 

    So, the most likely explanation seems to be that J002E3 is the third stage of the rocket for Apollo 12.  NASA originally planned to shoot this into an orbit around the Sun.  But they used more of the propellant than planned, and it seems that venting the rest didn't give this rocket stage enough energy to escape the Earth–Moon system.   So, it ended up in a complicated orbit around the Earth after passing by the Moon on November 18, 1969.

    It may hit earth someday!   It weighs 10 tonnes.  But don't worry: a 10-tonne meteor hits the Earth every few years, and most of them don't cause much trouble.

    I saw this animated gif without much explanation last night on G+.  Who should I thank?   The explanation here is adapted from Wikipedia:

    https://en.wikipedia.org/wiki/J002E3

    and the animated gif was made by Paul Chodas & Ron Baalke of NASA.

    #astronomy  
  • 303 plusses - 34 comments - 60 shares | Read in G+
  • Yonatan Zunger2013-10-07 08:23:14
    In re: http://xkcd.com/1274/

    There is a basic problem with the belief that a secret conspiracy runs the US government. It boils down to this: for the past few decades, the entire structure of the American society and economy has been moving towards a situation in which only the most powerful have access to core services, ranging from housing to medicine to police protection, and that everyone else is essentially dependent upon the goodwill of their benefactors to maintain their access to such things. This creates a profound social stratification which is tremendously to the advantage of those few people who end up on top of it, and tremendously to the disadvantage of everyone else, and to the existence of a civil society and democracy as a whole.

    So you have two options. Either this isn’t the actual objective of the secret conspiracy, in which case the government is apparently being run by a conspiracy of total idiots who have nevertheless managed to keep an iron grip on the reins of power. Or this is their actual objective, in which case the conspiracy isn’t a secret. 

    (Having ties to several of the below-mentioned conspiracies -- I am, apparently, even a member of the “Google+ Jewish Mafia,” although I’m still waiting for my membership card -- all I have to say to my fellow conspirators is: Wait, you thought we were doing this? I thought you guys were controlling the government. Who the fuck is driving this thing, anyway?)
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  • Yonatan Zunger2013-12-02 17:49:09
    RESHARE:
    Alright, someone has been working overtime to come up with good ideas.

    Reshared text:
    Someone missed their Amazon drone delivery :)

    via Reddit. 
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  • Yonatan Zunger2014-01-30 08:39:24
    Academia in a nutshell, via +Sarah Lester, to which +Christina Talbott-Clark adds this illustration of adjunct instructors: http://goo.gl/v42TUJ

    Although I left academia several years ago, in my heart, I still hope to look like a Professor Emeritus one day.

    (I cannot, alas, find the original source, as apparently it has been bouncing around the Internet with great vigor.)
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  • Yonatan Zunger2014-03-20 19:55:31
    Fred Phelps, of "God Hates Fags" infamy, died today. +George Takei had some good words to say on the subject. But in one thing I disagree: I do, actually, wish that I had the time to go to his funeral and picket it.

    My sign would say, "God loves you too, Fred."

    I would like to get some friends to come as well. Maybe some other signs could say "You are a person worthy of love and respect," or "Being good to other people makes the world a better place." There are a lot of good signs we could stand there with.
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  • Yonatan Zunger2013-09-22 17:26:17
    RESHARE:
    Here's something interesting for your Sunday morning. This team took stacks of pictures of people from different countries and assembled an "average face" for each of them. It's striking to me how well this works -- from each of the countries that I know, the faces have the deep familiarity of "the face I would expect to see on the street."

    A few notes on this: The fstoppers article notes that there has been a controversy around these faces looking "too beautiful" rather than average; as they note, this is what happens when you average out facial features, because any anomalies or asymmetries in any individual face are going to be averaged out. The result is likely to be very symmetric and free of any individual differences simply by the law of averages. 

    Also, no word on whether they're going to do a similar analysis on men; I'd be quite curious to see that, as well.

    h/t +Mary Robinette Kowal.

    Reshared text:
    The Average Face (zoom in to enjoy)
    Psychologists at the University of Glasgow in Scotland have combined the faces of women around to world to approximate the "average face" of each country.
    http://faceresearch.org/
    Complete list: http://goo.gl/Uuu9Ry
    Source: http://goo.gl/ywwkFt
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  • Yonatan Zunger2013-09-14 00:03:04
    RESHARE:
    OK, this is kind of spellbinding: the motion of the terminator (the line between night and day) superimposed on the graph of commercial air traffic. You can watch how time of day affects the rate of flights.

    I could watch this for hours.

    via +Daniel Estrada.

    Reshared text:
    We can see on this animations the airplanes commercial flight everyday.

    The main today trafic is still in US ans Europe but Eastern countries are growing and pull the aircraft market.

    We can see also that during the second part of the night there are far fewer planes flying.
  • 249 plusses - 24 comments - 84 shares | Read in G+
  • Yonatan Zunger2014-01-20 20:53:19
    Irving Finkel of the British Museum reports here (and at more length in his new book) about the discovery of a new cuneiform tablet with a flood story -- this one containing precise boat-building instructions, and one of our best pictures of Sumerian boat-building techniques.

    So, why is this interesting? Because it's a crucial link in understanding the Near Eastern part of the roots of our society. 

    This tablet dates from the Old Babylonian period, somewhere between 1900-1700BCE, making it over a thousand years older than the oldest parts of the Bible. However, its version of the story is significantly closer to the Biblical version than any yet found, even including animals marching aboard "two by two."

    This is both surprising and not surprising. The not-surprising part is that basically all of Genesis up to and including the Flood story, except the parts which are family history, have direct parallels in Sumerian cuneiform texts. The Bible gives an internal explanation for this -- that Abraham came from Ur -- and we have a much more coherent explanation of this in the fact that much of the writing of the Bible, as well as its editing, happened during the period of the Babylonian Exile, a period in the 6th century BCE where (following a conquest by the Neo-Babylonian Empire) the elites of Judah were packed off to Babylon (this being standard N-B practice as a way of avoiding rebellions in conquered areas), and a movement formed among them to build up a national identity among the exiles.

    The surprising part is that there is no way that these exiles could have seen this tablet, since it was written over a thousand years earlier, and yet the texts are surprisingly close; not a thousand years' worth of drift. Clearly, the people who wrote down the Biblical text had heard the story in very similar form -- which means it had been well-preserved!

    We can learn more by looking at the Biblical text. The Flood story that we have today is the work of two hands. The core of the story shows up from the J source, written in the southern kingdom of Judah (the same place that the exiles were taken from) ca 950BCE; the rest is added by the P source, written post-exile, between 600-400BCE, when this core group of Judean exiles had returned, and the area was now part of the Persian empire. The J source contains the basic idea of the Flood, God deciding to annihilate the planet, and Noah building an ark. The P source adds the building instructions, details about Noah's family, and the idea of a "second divine covenant" -- an idea that was very important to the P author(s), who were focused on defining a much more priest-centered society around a national mythology of exile and return.

    So we can see two interesting things here.

    (1) (Which we already knew) The Flood story was current across the entire Near East for a long time, and the J author in Judah in 950BCE knew a story which was basically the same as the core one which everyone knew.

    (2) (Which we didn't know) The Babylonian version of the story, which the P sources knew, seems to have been remarkably stable over time, including its emphasis on the methods of boat-building and the two-by-two motif. 

    The question this immediately raises for me is why the Flood story was considered important enough in Babylon to be preserved so well over time. Its importance to the priestly community post-Exile is easy to understand, and since that community established a written text that has stayed current ever since, it's not hard to see how the story stuck around. But what was the role of this story in the rest of the Near East? Why did everyone know it so well?

    In a way, this is a minor chunk of history. But there's something big behind it as well: this is a story that was known so well that children likely heard it at bedtime. It's a story which was apparently so important that it was considered one of the "basic" stories of the Near East -- part of how the society defined itself. What we have here is direct contact with the daily life of a society nearly four thousand years in our past; one of the few times we can directly reach in and see something which they interacted with every day, and get a sense of what it might have meant to them. 

    That's kind of amazing.


    If you want to know more about the different authors of the Bible, you can start with the Wikipedia article: http://en.wikipedia.org/wiki/Documentary_hypothesis . For detailed breakdowns of what was written by whom, the best summary of current scholarship is Friedman's The Bible with Sources Revealed.  

    There are three major known Sumerian flood stories: one starring Zi-ud-sudra from the Eridu Genesis story, one starring Ut-napishtim from Gilgamesh, and this one, starring Atra-Hasıs. You can get the basics of those here:

    http://en.wikipedia.org/wiki/Sumerian_creation_myth
    http://en.wikipedia.org/wiki/Gilgamesh_flood_myth
    http://en.wikipedia.org/wiki/Atra-Hasis

    h/t +Joseph Moosman for this article.
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