Sean Carroll

Author: Sean Carroll

  • Seriously, The Laws Underlying The Physics of Everyday Life Really Are Completely Understood

    While the primary purpose of last week’s post on the laws of physics underlying everyday life was to convey information like a good blog post should, there was another agenda as well: to test the waters. This is an issue I’ve been thinking about a lot lately, but I wanted to get a better idea for how it’s perceived in the outside world. I honestly wasn’t sure whether there would be more of “you arrogant physicist, we don’t have any idea what the laws are” or “you moron, why are you wasting our time with this self-evident crap?”

    So much for that ambiguity. Responses, for example at Fark and Reddit but even here in our very own comment section, displayed a greater than average internetitude, defined as a tendency to not read the article, set up straw men, and miss the point. But at least the direction of disagreement was fairly uniform. The issue under discussion is important, so it’s worth taking the time to counter the three most common arguments, from completely silly to almost-sensible.

    1. Are you serious? There’s so much we don’t understand: turbulence, consciousness, the gravitational N-body problem, photosynthesis…

    To which my years of academic training have prepared me to reply: duh. To conclude from my post that I was convinced we had a full understanding of any of those things represents, at a minimum, a rather uncharitable reading, given that no one in their right mind thinks we have such an understanding. Nevertheless, I knew people would raise this point as if it were an objection, which is why I was extra careful to say “We certainly don’t have anything close to a complete understanding of how the basic laws actually play out in the real world — we don’t understand high-temperature superconductivity, or for that matter human consciousness, or a cure for cancer, or predicting the weather, or how best to regulate our financial system.” And then, at a risk of being repetitive and boring, I added “Again, not the detailed way in which everything plays out, but the underlying principles.” And for emphasis there was something about “the much more jagged and unpredictable frontier of how the basic laws play out in complicated ways.” Nevertheless.

    The distinction I’m drawing is between the laws underlying various phenomena, and how the phenomena actually behave, especially on macroscopic scales. Newtonian gravity provides an excellent example of the difference: we certainly know the laws underlying the behavior of gravitating particles in the Newtonian regime, but that obviously does not mean we have a complete solution to the N-body problem, or even a qualitative understanding of how large collections of particles behave. It’s the difference between knowing the rules by which chess is played, and being a grandmaster. Those are not the same thing. In particular, taunting “you’re no grandmaster!” is not actually a refutation of the claim that I know the rules of chess. My claim was that we know the basic equations governing the behavior of matter and energy in the everyday regime — not that we have a complete understanding of every observable phenomenon.

    It is of course completely legitimate not to care that we know the basic underlying laws. You may not think that’s interesting, or very important. That’s fine, I certainly wasn’t making any claims at all about priority or importance or interestingness. But it should still be possible to understand the claim I was making, and judge it on its own merits, such as they are.

    Let me just emphasize how non-trivial the claim is. First, that there is such a thing as an “underlying” set of laws. That is, that we can think of everyday objects as being composed of individual pieces, such that those pieces obey laws that are the same independently of the larger context. (Electrons obey the same equations of motion whether they are in a rock or in a human heart.) That’s the reductionist step. Again, for people who enjoy taking offense: this is not to say that the reductionist description is the only interesting one, or to imply that the right way to attack macroscopic problems is to reduce them to microscopic ones; only that the microscopic laws exist, and work, and are complete within their realms of validity. And second, that we know what those laws are. There’s nothing in the everyday world that is inconsistent with Standard Model particles obeying the rules of quantum field theory, plus general relativity to describe gravity. Amazing.

    (more…)

  • Aristotle on Household Robots

    At Science Not Fiction, Malcolm MacIver reports on Roombots — robots that can assemble themselves into different pieces of “furniture,” depending on the demands of the situation. Meanwhile, in the middle of a lecture on Marx, Brad DeLong mentions that Aristotle long ago pointed out that the drudgeries of everyday life would prevent most people from becoming true lovers of wisdom. Too much time cooking and cleaning made it hard to curl up with a good philosophy book. In Aristotle’s time, the solution was clear: have your slaves do the dirty work while you contemplated deep thoughts. But he was smart enough to realize that there was another possible route to carving out free time: automation. In the Politics (c. 350 BCE) he writes:

    There is only one condition in which we can imagine managers not needing subordinates, and masters not needing slaves.

    This condition would be that each (inanimate) instrument could do its own work, at the word of command or by intelligent anticipation, like the statues of Daedalus or the tripods made by Hephaestus, of which Homer relates that

    “Of their own motion they entered the conclave of Gods on Olympus”

    as if a shuttle should weave of itself, and a plectrum should do its own harp playing.

    I suspect Aristotle would have been quite tickled at self-reassembling robots.

  • Sharktopus

    “Greatness comes with a price. It always has.”

    Premiering tonight on SyFy. I trust no more needs be said.

  • The New Objectivity

    Great post yesterday by fellow Discover denizen Ed Yong, asking “Should science journalists take sides?” Honestly, it shouldn’t be a hard question, although the answer depends on how you visualize the sides. If you have in mind

    He said vs. She said,

    then the job of a journalist is not to take sides. But there’s another possible dichotomy that is much more crucial:

    Truth vs. Falsity.

    In this case, it’s equally clear that journalists should take sides: they should be in favor of the truth. Not just passively, by trying not to make things up, but actively, by trying to figure out whether something is false before reporting it, even if it’s been said by someone.

    All sounds kind of trivial, but it’s easy to lose sight of this principle by hewing to a misguided definition of “objectivity.” Ed pulls an extremely damning quote from medical journalist Jeremy Laurance:

    Reporters are messengers – their job is to tell, as accurately as they can, what has been said, with the benefit of such insight as their experience allows them to bring, not to second guess whether what is said is right.

    That sounds about as wrong as it it possible to be wrong. It reflects a kind of lazy pseudo-objectivity that stems mostly, I would uncharitably suggest, from fear — the fear that one will make a mistake in trying to judge whether someone is lying or telling the truth. If journalists are just mindless stenographers, they can’t be accused of making that particular mistake. But they are actually making a much more serious mistake, abandoning the search for truth in favor of the goal of not being blamed.

    It’s hard to argue against this mindset, which is often mis-labeled as “objectivity.” So maybe we should be defending the New Objectivity: the crucial duty of reporters to separate what is true from what is false. If a scientist says “this drug will cure cancer,” but the peer-review study doesn’t back that up, it should be a journalist’s duty to make that clear. If a politician says “my plan will cut the deficit,” but a GAO report suggests otherwise, it should be a journalist’s duty to highlight the inconsistency. “Objectivity” shouldn’t mean “report what is said and don’t pass judgment”; it means “uncover the truth, no matter who says what.”

  • Time Dilation in Your Living Room

    Einstein tells us that the time you experience between two events depends on the path you take through the universe. In particular, it can depend on the curvature of spacetime along your trajectory. At a quick-and-dirty level: clocks in a strong gravitational field tick more slowly than ones far away from any gravity. (At the event horizon of a black hole, they wouldn’t tick at all.)

    Or not so far away: James Chin-Wen Chou and colleagues at NIST have measured the difference in clocks that are separated by 33 centimeters in elevation. That’s one foot for you Americans. (See NPR, Science News, press release. And because this is a blog rather than Old Media, I’ll even link to the research paper in Science.) As predicted, the elevated clock ticks faster by a factor of (1 + 4×10-17). If you stand on a chair, you’ll move into the future that much faster.

    Not a surprise, of course; it’s a straightforward application of general relativity. Still, we need to look pretty hard to find GR showing up on human scales. These guys worked very hard!

  • The Laws Underlying The Physics of Everyday Life Are Completely Understood

    Not sure why people don’t make a bigger deal out of this fact. Physicists (and scientists more generally) are infamous for making grandiose claims about how close we are to Figuring It All Out, only to be shocked by some sort of revolutionary discoveries soon thereafter. Personally I have no idea how close we are to a comprehensive theory of absolutely everything. But I do know how close we are to having a comprehensive theory of the basic laws underlying the phenomena we encounter in our everyday lives — without benefit of fancy telescopes or particle accelerators or what have you. Namely, we already have it! That seems to be worth celebrating, or at least remarking upon, but you don’t hear it mentioned very much.

    Obviously there are plenty of things we don’t understand. We don’t know how to quantize gravity, or what the dark matter is, or what breaks electroweak symmetry. But we don’t need to know any of those things to account for the world that is immediately apparent to us. We certainly don’t have anything close to a complete understanding of how the basic laws actually play out in the real world — we don’t understand high-temperature superconductivity, or for that matter human consciousness, or a cure for cancer, or predicting the weather, or how best to regulate our financial system. But these are manifestations of the underlying laws, not signs that our understanding of the laws are incomplete. Nobody thinks we’re going to have to invent new elementary particles or forces in order to understand high-Tc superconductivity, much less predicting the weather.

    All we need to account for everything we see in our everyday lives are a handful of particles — electrons, protons, and neutrons — interacting via a few forces — the nuclear forces, gravity, and electromagnetism — subject to the basic rules of quantum mechanics and general relativity. You can substitute up and down quarks for protons and neutrons if you like, but most of us don’t notice the substructure of nucleons on a daily basis. That’s a remarkably short list of ingredients, to account for all the marvelous diversity of things we see in the world.

    A hundred years ago it would have been easy to ask a basic question to which physics couldn’t provide a satisfying answer. “What keeps this table from collapsing?” “Why are there different elements?” “What kind of signal travels from the brain to your muscles?” But now we understand all that stuff. (Again, not the detailed way in which everything plays out, but the underlying principles.) Fifty years ago we more or less had it figured out, depending on how picky you want to be about the nuclear forces. But there’s no question that the human goal of figuring out the basic rules by which the easily observable world works was one that was achieved once and for all in the twentieth century.

    You might question the “once and for all” part of that formulation, but it’s solid. Of course revolutions can always happen, but there’s every reason to believe that our current understanding is complete within the everyday realm. Using the framework of quantum field theory — which we have no reason to doubt in this regime — we can classify the kinds of new particles and forces that could conceivably exist, and go look for them. It’s absolutely possible that such particles and forces do exist, but they must be hidden from us somehow: either the particles are too massive to be produced, or decay too quickly to be detected, or interact too weakly to influence ordinary matter; and the forces are either too weak or too short-range to be noticed. In any of those cases, if they can’t be found by our current techniques, they are also unable to influence what we see in our everyday lives. We have very little idea how big the region of our understanding is, compared to all that there is to be understood; but we know that it’s bigger than what we need to understand to make sense of the world we see with our unaided senses.

    That’s pretty amazing. Science will certainly push forward along the frontier of phenomena that are too big or small or subtle to be detected without delicate instruments, as well as along the much more jagged and unpredictable frontier of how the basic laws play out in complicated ways. But getting the basic laws right is an extremely impressive accomplishment, especially for good old human beings who have only been doing science systematically for a few centuries. Way to go, human beings!

    (See follow-up posts here and here.)

  • Nut Up or Shut Up

    Observe as a striving young author demonstrates how to fluster an innocent morning TV host by dropping quotes from Zombieland. (If you don’t get the first clip, press pause and go to the menu on top.)

    DayPortPlayer.newPlayer({articleID:”841556″,playerInstanceID:”FEB04E69-C718-D8E8-2B18-8543AE193B23″,domain:”xetv.web.entriq.net”});

    There is a lesson here, in the reaction to the title The Calculus Diaries. You write a book to emphasize the fun and conceptual side of math, to reach an audience that doesn’t traditionally pick up science books. How do you get them to buy a book with “Calculus” in the title? Zombies and Vegas help, but it’s an uphill battle.

  • Working My Way Back

    Okay, I think it’s time to step down from hiatus and get back into this blogging thing. I missed you guys! And I notice that the science blogosphere has completely blown up and re-organized since I left. Which is a good thing.

    I don’t like to navel-gaze too much about the act of blogging, but a gradual evolution in my own style was the primary motivation for my hiatus. In the good old days I stuck mostly to very short posts, pointing to this or that and making simple comments without feeling obligated to provide elaborate justifications for every little thing. But over time, I found myself increasingly seeing every post as a multi-layered 3,000 word essay. (Even if they didn’t end up that way in actuality, that’s how they often were in my head.) Not a sustainable model for someone for whom blogging is a hobby, not a vocation. I promised myself long ago that if blogging ever started to take up too much time (roughly, more than 3 hours/week), something would be broken and I’d have to fix it.

    So here I am fixing it. I really do very much enjoy the idea of blogging, both exploring ideas for my own sake and the wider conversation with other bloggers and with commenters. But given unitarity constraints on my time and energy, I need to concentrate on punchier posts, and comments that are not fully supported against every possible counter-argument. If the experience of writing a book nudged me toward longer forms, the success of Twitter demonstrates the value of the quick hit & link. Of course I will mix things up, which is part of the fun — longer posts here and there, the occasional video. There may be LOLcats. But I’ll try to refrain from writing poetry.

    And now for dessert: chocolate extravaganza from my favorite restaurant, Alinea in Chicago. Ordinarily there are no tablecloths at Alinea, but for this course they cover the table with a thin sheet of silicone and — well, you’ll see.

    Some of you might find this presentation too precious and extravagant to be enjoyable. I understand, and I’m sure you’ll appreciate the Oreo Blender Blaster at Denny’s.

  • Stephen Hawking Settles the God Question Once and For All

    Stephen Hawking has a new book coming out (The Grand Design, with Leonard Mlodinow). Among other things, he points out that modern physics has progressed to the point where we don’t need to invoke God to explain the existence of the universe. This is not exactly a hot flash — I remember writing an essay making the same point for a philosophy class my sophomore year in college — but it makes news because it’s Hawking who says it. And that’s absolutely fine — Hawking has a track record of making substantial intellectual contributions, there’s every reason to listen to him more than random undergraduates waxing profound.

    This issue is, of course, totally up my alley, and I should certainly blog about it. But I can’t, because I’m on hiatus! (Right?) So, as an experiment, I made a video of myself talking rather than simply typing my words into the computer. Radical! Not sure the amount of information conveyed is anywhere near as large in this format, and obviously I didn’t sweat the production values. I fear that some subtleties of the argument may be lost. But if we’re lucky, other people elsewhere on the internet will also talk about these questions, and we’ll get it all sorted out.

    Let me know if the Grand Video Experiment is worth repeating and improving, or whether it’s just a waste of time.

    Something that I should have said, but didn’t: there doesn’t need to be some sophisticated modern-physics answer to the question “Why is there something rather than nothing?” The universe can simply exist, end of story. But it’s still fun to think carefully about all the possibilities, existence and non-existence both included.

  • Calculus Day!

    Yes, I know, I’m not very good at this hiatus thing. But there is important news that needs to be promulgated widely — the news of calculus. No more will innocent citizens cower in fear at the thought of derivatives and integrals, or flash back in horror to the days of terror and confusion in high-school math class. Because now there is a cure for these maladies — The Calculus Diaries: How Math Can Help You Lose Weight, Win in Vegas, and Survive a Zombie Apocalypse.

    The Calculus Diaries

    Yes, you read that subtitle correctly. Let’s be clear: this book is probably not for you. That’s because you, I have no doubt, already love calculus. You carry a table of integrals in your back pocket, and you practice substituting variables to while away the time in the DMV. This isn’t the book for people who already appreciate the austere beauty of a differential equation, or even for people who want to study up for their AP exam.

    No, this is the book for people who hate math. It’s for people who look at you funny and turn away at parties when you mention that you enjoy science. It’s for your older relatives who think you’re crazy for appreciating all that technical stuff, or your nieces and nephews who haven’t yet been captivated by the beauty of mathematics. The Calculus Diaries is the book for people who need to be convinced that math isn’t an intimidating chore — that it can be fun.

    Know anybody like that? Any gift-giving holidays coming up?

    Now it’s true, I know the author. In fact, I appear as a character in the book (to a certain degree of comic effect). I’m the one who gets soaked when we ride Splash Mountain at Disneyland, but also the one who maximizes his winnings at craps by clever betting in Vegas. You get the idea: this isn’t a textbook, it’s a tour through the real world (and occasional fantasy worlds), pointing out that math is all around us, and that perceiving it is kind of cool.

    When you understand math, how you think about the world changes. Every day, we all change position by accumulating velocity, or do informal optimization problems when making a decision. But most people don’t know about the wonderful insights that math can add to these processes. You know, because you are a mathphile. But you are outnumbered by the mathphobes. You have a secret that they don’t know, but now there’s a way to share it. What are you waiting for?