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.

2. We don’t even understand gravity! And the Second Law of Thermodynamics! And quantum mechanics! (Magnets! How do they work???)

Unlike the previous objection, this one is not correct-but-misplaced, it’s just wrong. But it’s wrong in an interesting way. We actually do understand gravity: it is described by Einstein’s general relativity. Not deep down at the quantum level, of course, but that’s very far from the world of the “everyday.” You might try to make some profound epistemological claim that we don’t really understand gravity, we just have a set of rules that it unambiguously obeys. Fine; I would argue that this isn’t an especially helpful distinction in this case, but in any event it’s beside the point. What I meant was that we have a clear set of rules that are unambiguously obeyed. That’s also true for the Second Law — it was explained by Boltzmann. Sure, we have to invoke a low-entropy boundary condition at the Big Bang, but guess what? The Big Bang is not within the realm of our everyday experience. Even the collapse of the wave function, which comes closest to a true mystery, doesn’t qualify. For one thing, wave function collapse isn’t something you see happening in your kitchen on an everyday basis. But more importantly, we do have a theory that describes what happens, handed down to us by Bohr and Heisenberg. You might think that this theory is unsatisfying and incomplete, and I would be extremely sympathetic. But it fits all the data we have. I’m not trying to make a deep philosophical point about the meaning of “understanding”; just noting that things obey laws, and in the everyday regime we know what those laws are.

3. You’re too presumptuous. New physics might be required to understand consciousness, or wave function collapse, or…

This comes closest to an actual argument, and I wish that the entire conversation could have focused on relatively sensible points of this form. But ultimately, I don’t buy it, not even close. Take consciousness as an example. Obviously there are a lot of things about the workings of the human mind that we don’t understand. So how can we be so sure that new physics isn’t involved?

Of course we can’t be sure, but that’s not the point. We can’t be sure that the motion of the planets isn’t governed by hard-working angels keeping them on their orbits, in the metaphysical-certitude sense of being “sure.” That’s not a criterion that is useful in science. Rather, in the face of admittedly incomplete understanding, we evaluate the relative merits of competing hypotheses. In this case, one hypothesis says that the operation of the brain is affected in a rather ill-defined way by influences that are not described by the known laws of physics, and that these effects will ultimately help us make sense of human consciousness; the other says that brains are complicated, so it’s no surprise that we don’t understand everything, but that an ultimate explanation will fit comfortably within the framework of known fundamental physics. This is not really a close call; by conventional scientific measures, the idea that known physics will be able to account for the brain is enormously far in the lead. To persuade anyone otherwise, you would have to point to something the brain does that is in apparent conflict with the Standard Model or general relativity. (Bending spoons across large distances would qualify.) Until then, the fact that something is complicated isn’t evidence that the particular collection of atoms we call the brain obeys different rules than other collections of atoms.

What would be a refutation of my claim that we understand the laws underlying everyday phenomena? Easy: point to just one example of an everyday phenomenon that provides evidence of “new physics” beyond the laws we know. Something directly visible that requires a violation of general relativity or the Standard Model. That’s all it would take, but there aren’t any such phenomena.

A century ago, that would have been incredibly easy to do; the world of Newtonian mechanics plus Maxwell’s equations wasn’t able to account for why the Sun shines, or why tables are solid. Now we do understand how to account for those things in terms of known laws of physics. I am not, as a hopelessly optimistic scientist from the year 1900 might have been tempted to do, predicting that soon we will understand everything. That’s an invitation to ridicule. Indeed, we know lots of cases where the known laws of physics are manifestly insufficient: dark matter, dark energy, electroweak symmetry breaking, the Big Bang, quantum gravity, the matter/antimatter asymmetry, and so on. We might answer all these questions soon, or it might take a really long time. But these are all rather dramatically outside our everyday experience. When it comes to everyday phenomena that are incompletely understood, from consciousness to photosynthesis, there is every reason to believe that an ultimate explanation will be obtained within the framework of the underlying laws we know, not from stepping outside that framework. An impressive accomplishment.

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125 Responses to Seriously, The Laws Underlying The Physics of Everyday Life Really Are Completely Understood

  1. bittergradstudent says:

    @Nullius:

    there are compelling theoretical reasons to believe that Quantum Gravity exists. But there is no definitive proof that semiclassical gravity is fundamentally false. Not one quantum gravitational phenomenon has ever been observed. At best, we’ve deduced that one has happened–the big bang. But we know so little about the very, very early universe, that it’s basically guesswork to say what happened in the full quantum gravitational regime of big bang cosmology.

  2. Waveforms says:

    @Nullius in Verba

    +1. Another well written, and interesting comment.

  3. Craig McGillivary says:

    So why should we pay COsmologists when we could be paying people to study brains? Shouldn’t we spend research dollars on scientific questions that effect our daily lives?

  4. John says:

    @90 Ray, thanks for your reply.

    You state that I make a philosophical argument against the sufficiency of the standard model. That I object against. My observation is a direct consequence of the mathematical nature of QFT. Any physicist can tell you QFT is incapable of describing free will and consciousness. And it is not a matter of “not having a complete understanding of how the basic laws actually play out in the real world”. There is a huge difference between not understanding high-temperature superconductivity and not understanding free will. And Sean knows this.

    Forget about philosophers. They have no clue. Read Conway, read Penrose.

  5. Boaz says:

    A point on the chess analogy to physics/science. In chess, the rules refer to the pieces and board we see that are quite easy to identify. In the standard model and general relativity, the rules refer to fields, and the connection to stuff we see around us is quite elaborate. So in addition to the rules of QFT and general relativity, we need rules to go from what we see to the elements in the standard model or a spacetime structure. And really, most of the time, we don’t end up with some SU(3)xSU(2)xU(1) field in our explanations of everyday things. Its a part of the creativity, and difficulty of science to go from something we see/find, to an appropriate model for it.

    So, to continue the chess analogy, we might say that in addition to the rules of chess, we need to know how to identify the pieces and where they are on the board! Do we know the rules for this? I’m not sure. And this makes the whole claim that one can always find an explanation within the standard model/general relativity framework pretty hard to evaluate.

  6. Ray says:

    @104 John
    It has neither been demonstrated empirically that we have free will in the sense required by Conway’s theorem nor has it been demonstrated that subatomic particles don’t have it. It is your philosophical assumptions that lead you to believe Conway’s theorem is a problem for QFT.

    I am also familiar with Penrose and the argument he first put forward in “the emperor’s new mind”. He’s a smart guy, but he badly misunderstands Godel’s theorem. see http://www.mth.kcl.ac.uk/~llandau/Homepage/Math/penrose.html
    (yes it has philosophical in the title, but it’s written by a mathematician.)
    I think Penrose eventually decided to save face by saying his ideas about the mind were merely speculations.

    In conclusion, High T superconductivity is indeed very different from contracausal free will and immaterial souls in that it actually exists.

  7. John says:

    @106 Ray, let me try to summarize what we disagree upon (and then perhaps we can agree to disagree).

    Our current fundamental laws of physics don’t contain any elements that allow us to differentiate at a fundamental level between a lump of dead matter (e.g. a stone) and a brain. Agree?

    Your position seems to be: at a fundamental level there indeed is no difference between a stone and a brain, they both are lumps of matter that behave according to QFT. Right?

    My position, however, is: we haven’t yet discovered the fundamental laws of reality that describe both stones and brains. The laws we are currently working with provide excellent approximations to the behavior of stones (or turbulent flow, or high temperature superconductors, or …) but fail miserably when applied to brains.

    What is the likelihood that a century from now Sean will be the laughing stock of modern science? I don’t know, but surely I have no reasons to believe the likelihood is zero.

  8. Ray says:

    “The laws we are currently working with provide excellent approximations to the behavior of stones (or turbulent flow, or high temperature superconductors, or …) but fail miserably when applied to brains. ”
    — i think this is exactly backwards. We can model individual neurons extremely well and it doesn’t even hint at anything more exotic than run of the mill quantum electrodynamics with semi-classical approximations kicking in at the molecular level. We can even track brain activity by predicting the exact radio frequency given off by atomic nuclei in oxygenated blood in a magnetic field (fMRI.) High T superconductivity is not nearly so well understood.

    “What is the likelihood that a century from now Sean will be the laughing stock of modern science? I don’t know, but surely I have no reasons to believe the likelihood is zero.”

    It’s certainly not zero, but he’ll be in good company — feynman and hawking at least have said similar things in the 60s and 80s respectively, and we’re still talking about the same theories they were.

    You’re advocating vitalism. It’s an old idea and the majority of physicists and chemists have denied it since at least the mid 19th century. They haven’t been proven wrong yet.

  9. Bob says:

    There is no logical reason not to act as if free will exists. If free will exists then that is the only logical way to act and if free will does not exist then you are predestined to act as if it did exist.

  10. Pingback: One Last Stab | Cosmic Variance | Discover Magazine

  11. Nullius in Verba says:

    #101,

    “there are compelling theoretical reasons to believe that Quantum Gravity exists. But there is no definitive proof that semiclassical gravity is fundamentally false. Not one quantum gravitational phenomenon has ever been observed.”

    Semi-classical gravity has to be fundamentally false, because it is not a fully integrated quantum theory. What I think you mean is that the false predictions it makes are outside the realm of the everyday (and indeed the experimentally achievable).

    And we have, of course, observed quantum gravity. All gravity is actually quantum gravity, so you observe it every time you drop something. Again, what I think you mean is that we haven’t observed a quantum gravity phenomenon that requires an explicitly quantum gravity explanation: one for which the semi-classical model gives false predictions.

    Having a theory that makes accurate predictions is different from knowing what the actual laws underlying the everyday world are. It is, in itself, a stunning achievement, but it is not the same. It is possible to be sure a theory will always give correct predictions in all the circumstances you can access, while knowing for certain that the theory is wrong.

    Any physical theory has a domain of validity – it makes accurate predictions within it; the existence of a complementary part outside it is acknowledged but otherwise avoided. We often have a patchwork of such theories that together predict over a wider range of circumstances, but which are mutually inconsistent. Before the 20th century, they had theories that explained why tables were solid, and theories that explained the forces between charged particles, and they knew that the two were not consistent with one another. Today, we have a single theory that covers both. That is indeed a major achievement. But the physics of the everyday is still a patchwork solution, even today.

  12. bittergradstudent says:

    Why does everything in nature have to be a fully integrated quantum theory?

    We haven’t even directly observed gravitational waves, and you’re saying, with 100% certainty, that those degrees of freedom have to be quantized. Maybe we can just solve the back-reaction problem (and the in/out state problem in cosmology) in semiclassical gravity, and no experiment will ever be able to contradict the resulting predictions.

    There are compelling theoretical reasons to believe that this probably not work out–defining a stress-energy tensor is complicated with a quantum source and a classical field interacting with that source is tricky, to say the least, and there are apparent contradictions that can be derived.* But there are apparent contradictions that can be derived from QM and from special relativity, which just show that we’re asking the wrong questions.

    All we know about gravity at high energies is that it limits to gravity at low energies. And maybe we can be clever and say that it has something to do with cosmology.

  13. Nullius in Verba says:

    I’m only saying that the real universe has to be consistent. So we know that any inconsistent patchwork has to be incorrect.

    Maybe you can solve the problems a different way – producing something that is not a quantum field theory of gravity in the currently understood sense, but is something else. Something that looks like quantum theory in one approximation and like general relativity in another, but is actually neither. Maybe one day you can find some sort of semi-classical theory that works, explaining how to stitch together a quantum superposition of differently curved mutually interfering vacua. I’m easy on the details. But you don’t have it yet. And until you do, you have an incomplete patchwork.

  14. Marty says:

    If our best physical theories rely on postulates, does the fact that we formulate those postulates mean we understand what they postulate?

    One of the most ordinary attributes of the macroscopic world, and one that any person (educated or not) can observe, is that three spatial dimensions are sufficient to describe the relative positions of macroscopic objects. General relativity postulates a smooth differentiable manifold on which the metric can be determined if we know the stress-energy tensor over all of spacetime. The metric will have signature -+++, by assumption (and of course, because that is what agrees with observation). Since we have postulated 3 spatial dimensions, one time dimension, and a Lorentzian signature, does that mean we “understand” those facts? Sure, we observe that those postulates are apparently correct, at least macroscopically, but to say we “understand” those facts is contrary to what I think of as understanding.

    I think similar comments can be made about other parameters and postulates of our theories — do we understand them because we observe them, in the same sense that we understand gravity from general relativity?

  15. Marty says:

    I should have posted my comment above in the more recent thread. I’ll repost it there.

  16. John says:

    @Ray (108)
    I don’t see where I made any remarks that allow you to call me a vitalist. I am awaiting a next revolution in physics that will give us a handle on things like consciousness.

    See me as a medieval bystander who looks at Ptolemy’s models and shakes his head saying “there must be something better, a deeper physics law”. You tell me “this is it, there is nothing better, we have reached supreme understanding in planetary dynamics”.
    I am dreaming of physics developments centuries in the future (Newtonian physics, General Relativity) and you ask me why I believe in angels pushing the heavenly bodies.

    You totally missed my point.

  17. Ray says:

    “My position, however, is: we haven’t yet discovered the fundamental laws of reality that describe both stones and brains. The laws we are currently working with provide excellent approximations to the behavior of stones (or turbulent flow, or high temperature superconductors, or …) but fail miserably when applied to brains. ”

    I don’t know about you, but I’d call that vitalism, or at least Cartesian dualism (maybe you think the standard model is fine for simulating a ficus plant but not a brain? How about a fly’s brain? — that’s already been completely mapped.)

    My position is that if we ever do find necessary and sufficient conditions for a system to be conscious (or at least to act like it is as far as the outside world is concerned) They will not include anything that cannot be satisfied by a Turing complete cellular automaton, and they certainly will not include a requirement for physics beyond the standard model.

    I think careful philosophical investigation is enough to figure out that the primary arguments against this position (free will, qualia) are incoherent. That said, the best evidence is that the last 200 years of physics, chemistry, biology and neurology has made considerable progress by assuming that human behavior is explained by brains made up of neurons which are made up of molecules and ions, which in turn are made up of atoms of the sort that have been fully categorized by quantum electrodynamics. Yes, we make approximations at each level of reduction, and we calibrate empirically when we can’t calculate a precise enough answer for something, but there’s not anything going on that even looks particularly implausible given the underlying laws. You think your brain is a quantum computer? Great. Solve an RSA challenge. Maybe you think there’s something else your brain can do that a computer can’t. It’s possible, but there’s been steady progress for problems that are well defined, and even some that aren’t (natural language processing comes to mind — Google translator is pretty good. It makes dumb mistakes from time to time, but then so did our last president.)

  18. John says:

    Ray, vitalism postulates consciousness to be outside the realm of science. I consider consciousness within reach of physics but not contained in our current physics models. The difference is crucial, in particular in light of the discussion on Sean’s claim.

    If the standard model somehow describes consciousness, so does the game of life. To even entertain the thought that a large enough game of life could spring to life and develop consciousness, for me is just way beyond the boundary of irrationality.

  19. Nullius in Verba says:

    Ray, John,

    If brains are capabable of experiencing qualia and brains are no more than matter moving in suitably complicated ways according to Standard Model rules (perhaps modified), then all matter is capable of experiencing qualia by following the same rules. The Standard Model explains the mechanics, but doesn’t describe how the sensation of experiencing it works.

    That’s sounds more like panpsychism than vitalism. Or maybe panprotoexperientialism…

  20. Ray says:

    John
    http://www.merriam-webster.com/dictionary/vitalism

    The vitalism I accuse you of is definition 1, the vitalism you deny is definition 2.

    And yes, I believe a sufficiently large pattern in the game of life could behave as a conscious agent, but I don’t think you quite grok how large it would need to be or how slowly it would operate were it implemented using presently available technology.

    Nullius
    Your argument commits the fallacy of division: http://en.wikipedia.org/wiki/Fallacy_of_division

    You are certainly correct that if qualia are not identified with physical objects of some sort, we are faced with the uncomfortable conclusion that the reason we claim to have qualia is not because we have them. But, the qualia need not be simple objects.

    I think a more accurate way of describing what qualia are is as follows: a single person’s qualia are the primitive elements of a description of the universe in much the same way that quarks leptons and gauge bosons are the primitive elements of the standard model. I say it is a single person’s qualia, because if we admit another person’s qualia, inconsistencies can arise. If we describe a state of the universe where one person is looking at an fMRI of the other person and we claim the second person is experiencing a sensation other than what the fMRI says he is, we have uncovered a contradiction. (well, not a contradiction in the mathematical sense. The first person could be crazy. But if we suppose that the first person’s conscious experience contains enough of the clues we all use to confirm our own sanity, at some point Ockham’s razor kicks in.)

    Likewise, if we give a standard model account of what’s going on in the brain, and then we describe the qualia experienced by the owner of the brain, we have merely described the same thing twice in different language (although the second description may be incomplete.) In either case, the first description fully constrains what the content of the second can be. Furthermore, the whole of the standard model can be recovered from the conscious experience of any physics student who has learned it and has seen enough evidence to believe its predictions.

    I think the reason some people reject physical explanations of our qualia is that it’s hard to recognize the sensations we feel after they’ve been through two very ineffecient layers of re-encoding (the qualia described in the language of the standard model and the standard model described in the language of qualia).

  21. Nullius in Verba says:

    Ray,

    I assume by fallacy of division, you mean that I say because part of the universe is sentient, it all is. But what I said was that because part of the universe is sentient, and that part is not fundamentally different in any physically meaningful way from any other part, that it all has the potential to be sentient – whether it constitutes a biological brain or not. Sentience has to be inherent in the laws of physics (which are not necessarily just the standard model), not in brains. Thus, it isn’t vitalism, because it’s not distinguishing brains or life generally from physics, and it’s not dualism, because it posits no material of mind distinct from matter, but it does assert an observed phenomenon – a property of matter – that does not appear to be explained/described by the current model of those laws.

    I didn’t say qualia were not identified with physical objects (simple or complex). Although as it happens I’d be more likely to identify them with abstract properties of patterns in the arrangements and interactions of those objects. And we have qualia irrespective of whether or not we claim to.

    There is nothing in the standard model to distinguish an entity with qualia from one without – what the philosophers call a zombie: a purely mechanical agglomeration of particles that looks, acts, thinks, and speaks like a person, that even claims to have qualia, but which is internally insensate – particles moving in mechanistic orbits like a baroque tape-recorder. It may be that such a thing is impossible; that anything that simulates a person with sufficient fidelity will have the sensation of being a person. But if so, it isn’t clear how or why from any description of how the particles will move.

    What people are rejecting are not physical explanations of qualia, but explanations of the experience of sensation in terms of descriptions of particle motions alone. “Physics” does not necessarily have to be identified with just the types and motions of particles. It may well be an implied consequence of those particle motions, but there does not appear to be anything in the standard model (other than the basic symmetry saying brains are nothing special) to say whether it is or not.

  22. Ray says:

    Nullius:
    Ok. I may have misinterpreted you. I thought you were claiming subatomic particles had qualia or something to that effect.

    My position is that qualia does not provide evidence of macroscopically important physics beyond the standard model because

    1) there is certainly no reason to suppose that anything in the standard model prevents one from building a computer which would claim to have qualia and describe them in the terms humans generally do.

    2) once you accept 1, it’s very hard to accept that the qualia themselves are not accounted for by the standard model, since to do so would suppose that our claim that we have qualia does not arise from our observing the qualia but from an independent process.

    perhaps we do not in fact disagree.

  23. Nullius in Verba says:

    Ray,

    1. I agree with. A tape recorder would do. Question is, is there anything in the standard model to stop one building a computer that actually experiences qualia?

    2. “…independent process” Independent of what? Physics? Or those aspects of physics described by the standard model?

  24. Ray says:

    1) A tape recorder would not work. by describing qualia in human terms I don’t mean just giving a description and leaving it at that. I mean carrying on a conversation about it the way you do. I see no reason to doubt this is possible.

    2) I think I misphrased what I was trying to say here. Suppose we have a physical account within the standard model of why we claim to have qualia and defend that claim in the way we do. My feeling is that it’s a lot easier to imagine a satisfying explanation for that than a satisfying explanation for why we have qualia in the first place. However, given a standard model account for the behavior (claiming to have qualia and defending that claim vigorously in human terms) if we do not further accept that qualia can be accounted for by only standard model physics, then we are in the uncomfortable position of saying that our claim to have qualia is caused by something other than their actual existence.

    Now I think there’s a lot of good physics reasons for thinking nothing in our brain violates the standard model in any important way (it’s actually pretty hard to modify the standard model to get effects that would only be detectable in the brain) and good biology reasons to boot (biological processes that are very sensitive to small changes in chemistry tend not to be selected for, which means that what we’re looking for ought to be easy to produce in nature if it depends on fundamental physics rather than the complexity of biology.) I think in the end, it doesn’t seem that implausible that the reason we have trouble duplicating the exact structure of human thought is that it solves a very complicated problem which we really don’t understand (surviving and reproducing in a very complex environment which is made more complex by our fellow humans) and it seems very implausible that conditions in the brain make physics beyond the standard model important.

  25. We think & create a meaning & purpose to our Life; it’s a structuring device in our lives. In a universe of absolute(c) & relative(0 to c) spatial instantaneous propagations that had no beginnings & has no endings it is foolish to assume to have a divine, 5- year planned meaning. Nevertheless humans must learn the real nature of reality&harmonize with it, if for no any other reasons than self/serving reasons…Valentine S. Goroshko,NYC