The Effective Field Theory of Everyday Life, Revisited

By Sean Carroll | July 18, 2011 9:42 am

For some reason Nature News was inspired to tweet about my old blog post on Seriously, The Laws of Physics Underlying Everyday Life Are Completely Understood. Which I mentioned on Facebook, which led to an interesting comment, which I then mentioned on Google+… but now it’s substantive enough that I feel like I am neglecting our loyal blog readers! So here is a copy of my G+ comment, and a lament that I suck at proper use of the internet.

Not sure what brought this back to life. Like the Lord of the Rings, this is part of a trilogy; don’t miss the first installment, or the exciting conclusion.

As Michael Salem points out on an alternative social-media site (rhymes with “lacebook”), some of the resistance to this really quite unobjectionable claim comes from a lack of familiarity with the idea of a “range of validity” for a theory. We tend to think of scientific theories as “right” or “wrong,” which is hardly surprising. But not correct! Theories can be “right” within a certain regime, and useless outside that regime. Newtonian gravity is perfectly good if you want to fly a rocket to the Moon. But you need to toss it out and use general relativity (which has a wider range of validity) if you want to talk about black holes. And you have to toss out GR and use quantum gravity if you want to talk about the birth of the universe.

Just because there is something we don’t understand about some phenomenon (superconductivity, cancer, consciousness) does not imply that everything we think we know might be wrong. Sometimes we can say with confidence that certain things are known, even when other things are not.

Not only do theories have ranges of validity, but in some cases (as with the Standard Model of particle physics) we know what the range is. Or at least, we know where we have tested the theory and where we can be confident it is valid. The Standard Model is valid for all the particles and interactions that constitute our everyday existence.

Today we think of ourselves and the stuff we see around us as made of electrons, protons, and neutrons, interacting through gravity, electromagnetism, and the nuclear forces. A thousand years from now, we will still think precisely that. Unless we destroy the planet, or are uploaded into computers and decide that the laws of physics outside the Matrix aren’t that interesting any more.

  • Jean Spoto

    The universe is interesting for containing emergence and phase transitions. Perturbative physics fails outside its interval. As with economics, mensicus and continuous fluid are two extremes of bottle washing and button sorting. Critical opalescense is the big ride! Scintillate, for the universe wants to be explained.

    You cannot manage discovery, you can only manage to end it. Imagination is intelligence having fun. Mourn the dead, fix the problem, and get on with the job.

  • jpd

    ok, except that a proton isn’t a proton, its three quarks.

  • Julien

    Our everyday existence includes consciouness, and we have no idea whether our “effective field theory of everyday life” can explain it. The problem is not that we do not understand it all. The problem is we may come to understand behavior without gaining any understanding of counsciousness. That makes this hard problem very different from, say, superconditivity and cancer.

  • Georg

    “”Like the Lord of the Rings, this is part of a trilogy; “”

    Any good trilogy has a forth, maybe fith part,
    eg the Hitchhikers Guide…..

  • Moshe

    I am late for all that, but I am confused about the precise statement. My confusion is that you are not making claims about the EFT relevant to everyday life’s scales, but on that “underlying” it, and I am not sure what makes an EFT “underlie” another one. Do you mean that we have a complete understanding of the effective field theory in distance scales just below that of those relevant to daily life? why is that a privileged length scale? In other words, in what way are we “made of” protons instead of quarks?

    Hard to make prediction for the far future, but FWIW: one possibility for how we describe things around us a thousand years is that we may have a different idea of what “things are made of” means, we may not even be using that language anymore. In strongly coupled QFTs it is already very hard to make precise this Russian doll picture of bigger things made of smaller ones. In different physical regimes you have different excitations, some small and some large, and there is no universal way in which some of them are “made of” others. The EFT relevant for each physical regime is unambiguous, but that “underlying” it may not be. Again, hard to make predictions but this is one way in which our description of the physics underlying everyday life can fundamentally change in the future.

  • Low Math, Meekly Interacting

    “Underlying” is a crucial qualifier. Seems impossible, though, to avoid the debate about the existence of other “fundamental” laws of emergent phenomena not reducible to the SM and relativity. I tend to be highly doubtful that any such fundamental laws are there to be discovered, but am less sure the matter is resolved. Hence, I’m not sure there is no controversy. It may be mistaken controversy, but, as of yet, it seems impossible to say with much certainty one way or the other.

  • Sean

    jpd– The fact that protons are made of quarks does not mean that protons do not exist. And what protons are made of is completely irrelevant to our everyday life.

    Julien– There is zero evidence that consciousness involves physics beyond the Standard Model. That doesn’t mean that it certainly doesn’t, but the evidence in favor of quantum field theory as it is understood is so overwhelming that you need to do much better than point to something complicated and say “well explain that.”

    Moshe– We could argue about the precise definition of the “everyday life regime,” but I doubt that would be much fun or very enlightening. Regardless, I feel confident that the effective theory of atomic nuclei plus electrons interacting via gravity and E&M is sufficient to account for what a reasonable person would judge to be “everyday life.” The point is that it doesn’t matter what lies beneath. There is no question you can ask about everyday phenomena that cannot in principle be addressed within that theory.

    LMMI– The known laws are mathematically complete; either they are incorrect, or they suffice to say we understand what underlies everyday life. There can also be emergent laws that are fascinating in their own right, but that is not an incompatibility with the underlying description.

  • jpd

    the fact that protons exist is irrelevant to 99% of the population of the planet

  • Low Math, Meekly Interacting

    OK, I see the distinction when put in those terms.

  • rob

    sure Sean, but WWDCS?

    (what would deepak chopra say?)

    p.s. good post. i liked rereading your older trilogy too.

  • Julien

    >you need to do much better than point to something complicated and say “well explain that.”

    Sean, my post was precisely to point that the hard problem of consciousness is not of the “well explain that” kind. Did you take some time to read the link? Another one:

  • Moshe

    Sean, I was trying to make a different point, related to the imprecise nature of the word “underlying”, not that of “everyday life”. To give an analogy: is the physics underlying the quark-gluon plasma that of quarks and gluons interacting via the QCD lagrangian (which is in principle the complete story but in practice not all that useful), or is it that of 5 dimensional black hole in asymptotically AdS space?

    I would say that neither, or both, and in any case “underlying” in that context is not a very precise, unique or ultimately useful concept. Same may well hold for everyday phenomena that are “in principle” described by your effective field theory.

  • Lord

    Until we discover wormholes permeate our everyday life without our knowing about it.

  • Physicalist

    @ Julien:

    The “hard problem of consciousness” is based on philosophical confusion and gives us no reason to question the sort of physicalism that Sean is advocating. Philosophers just need to get a better understanding of what’s involved with understanding.

    Likewise, the common intuition that (phenomenological) zombies are possible is based a failure to conceive of all relevant physical facts. The arguments against physicalism just don’t hold up.

  • nick herbert

    “[Before one can apply quantum theory] the existence and general nature of macroscopic bodies and systems IS ASSUMED AT THE OUTSET. These facts are logically prior to the interpretation and are not expected to find an explanation in it”–Wendall Furry on the measurement.

    If Sean claims that quantum theory can “explain the world” when it has to assume “the existence and general nature of macroscopic bodies” is to really stretch the meaning of the word “explain”.

    Until physicists can come up with a convincing narrative about what happens in a measurement, quantum mechanics may be a useful tool but it does not “explain the world” on any scale.

  • Physicalist

    quantum mechanics may be a useful tool but it does not “explain the world” on any scale.

    Quantum mechanics explains the stability of atoms and molecules regardless of one’s interpretation of QM or one’s solution to the measurement problem.

    The predictive/formal accuracy of QM is enough for us to say that we have in hand the physics that is relevant for all neural processes. We therefore have very good evidence that all mental states are physical.

  • Julien


    Always glad to learn something. Please let me know where I’m wrong:

    If consciousness can in principle be explained by some EFT, then computationalism is right (we can describe ourselves as binary vectors, got uploaded in some Matrix, etc). If that’s true, as I also tend to think, then all we can do could be done in principle using a coin and a lot of chance. This coin tossing, I call it a philosophical zombie. Don’t you?

    The point is, if philosophical zombies are possibles in principle, then we have the problem of deciding what computation is or is not conscious, and this is hard because we can’t rely on behavior.

  • Loki

    Sean, i have a question to you
    You often remark that we don’t have any idea how consciousness works, that this problem is probably beyond our current methods and such. This is puzzling. You either didn’t read the literature on the subject, serious researchers and philosophers like Dennett, Ramachandran, Pinker, Mynsky etc. (An excellent book “Consciosness Explained” by a prominent 100% materialist philosopher Dennett is 20 years old!). Or you did read, but find all their models and arguments not just unconvincing but kind of empty ..

  • Sean

    Moshe– There are certainly interesting questions of principle here, but I don’t see how they are relevant to this claim in practice. By “the laws of physics underlying everyday life” I mean “the theory of nuclei and electrons interacting via E&M and gravity.” Maybe there is some other dual description of that physics, but even if so it wouldn’t change the claim. As long as there is one description that works, we’re okay. Unless you are suggesting that there are some everyday phenomena that really don’t fit into that description because of some subtle nonlocalities or strong-coupling issues.

  • Physicalist

    @ Julien

    Computationalism about the mental may or may not be correct, but it does not follow directly from physicalism. Physicalism (at the level of EFT) says that anything that is *physically* identical to you will also be identical with respect to its mental properties.

    However, a Matrix-computer process is not physically identical to the complex system of carbon, hydrogen, oxygen (etc.) atoms that is your brain.

    Philosophical zombies are not possible in principle. Physics is not only about behavior, it is also about the *causes* of behavior — specifically the forces, charges, and laws that *produce* behavior. The reason many philosophers erroneously believe that zombies are possible is that they conceive of physical behavior, but they don’t take proper account of the causes of behavior.

    Look at it this way:
    a) A physically identical world has to be causally identical to this world.
    b) Our conscious experiences (qualia) cause some behavior (my saying “ouch”).
    c) So any physically identical world has to include that cause; there has to be a conscious experience there; there cannot be a zombie.
    d) When you *think* you’re imagining a zombie, you’re really imagining a being that behaves like you, but that does not have the same causal-dynamical features that you have. So you’re not imagining a physically identical being.

  • Loki

    Julien. i think the answer to your question is in the old say: “If it looks like a cow and moos like a cow, than it is probably a cow”. If there is no way to find a difference between a zombie and a “conscious” human – than zombie is a conscious human. We are incredibly complex biological machines and consciousness is an emergent phenomenon. As Dennett puts it: “- Yes, we have a soul. And it is made of thousands of tiny simple robots.”
    It’s like color vision – you have no doubt about your color 3D vision, right? Yet is is easy to check with just a deck of cards that what you actually see in color (and any decent detail) is dime-sized spot right ahead. All the colorful world around is a creation of small and fast automatic modules in your brain that you have no conscious access to.
    Same with consciousness. Lots of small modules work incessantly. Some on higher level formulate phrases and an urge to speak out ir write in this chat. All demand attention. The one that has the most strong signal at the moment gets attention of others, and so on. Imagine a big crowd of people on the town square. Some are silent, some murmur to the neighbours, some shout. What you feel like “You”, is not an observer of this crowd, but the most loud person at any particular moment!

  • Moshe

    I think we both agree about the facts, but I an a bit uncomfortable with the language which seems stronger than the claim one can make. One can certainly envision a scenario where the best description of some everyday phenomena involves microscopic ingredients and mechanisms currently unknown, especially if the current ingredients become strongly coupled at the relevant physical regime. Even if such future description is consistent in principle with the current one, I suspect future physicists would claim the simpler description “underlies” that particular everyday phenomena, if they still use that language.

  • Julien


    1) I did not say computationnalism follows from physicalism. I said computationnalism must follow from current EFT (from QM, in fact).

    2) it seems your vision of physicalism is non standard. More precisely, it does not includes supervenience: the fact that two pictures can be be identical despite not physically identical. Was it for clarity purpose?

    3) there are several evidences that most of the time you say “ouch” before your brain construct the conscious interpretation that you decided to say “ouch”.

    4) your right I’m extending the philosophical zombie notion to something that present identical behavior, not physically identical being. So I’m not arguing against physicalism, I’m arguing against the idea that we can have a great confidence that ” The Laws of Physics Underlying Everyday Life Are Completely Understood.”

    @ Loki

    “If it looks like a cow and moos like a cow, than it is probably a cow”

    Well said. 😉

    So, will you accept to provide citizenship to any computer program that statistically can’t be differentiated from a significant proportion of humans, or will you restrict it to the computer programs whose inner computations are closes enough to the human way?

  • Physicalist

    @ Moshe

    What sort of strong coupling of current ingredients do you have in mind, and how would it undermine any of Sean’s claims? Are you suggesting that such couplings might occur in brain processes? Or are you just pointing out that if you slam together two electrons hard enough then current physics can’t predict what will happen?

  • Physicalist

    @ Julien,

    1. I don’t see that computationalism follows from EFT. I’m not even sure what this would mean. What sort of computationalism are we talking about?

    2. By physicalism I do mean that all facts supervene on the physical facts. This means that if the physical facts are the same, then all other facts are the same also (which is what I tried to say above).

    3. Yes, I often say “ouch” before the qualitative feeling of pain really sets it. Which is why when I’m being careful, I instead talk about the action of my carefully and deliberatively describing a pain. In this case it seems clear to me that the feeling itself is playing a crucial causal role. I was trying to be brief in making my point that experiences obviously have physical effects.

    4. But once we accept physicalism, it seems that arguments about zombies and the so-called hard problem are completely irrelevant to the question of whether we understand the physics underlying life and cognition. For this question, the relevant points are the ones that Sean rightly points to: We know the domain of applicability of QED and Newtonian Gravity, and life and cognition are processes that lie safely within those domains.

  • Loki

    Julien, it’s a moral and political question, and as such doesn’t have any “right” answer. Should we provide citizenship to a smart AI? To my big gray parrot (looks smarter than a dog and speaks!) ? How about 12-year olds? Clinical imbeciles? Criminals in jail?
    I don’t know … I think when they appear, smart computer programs, the world will change big time.
    I think the smart AI will not need our concept of “citizenship”. Besides, how can you infringe on its “rights” ? Good to know what are those in the first place :-) Take the right to exist: we have hard time dealing with stupid computer viruses! AI will have no problem making and storing as much copies of itself as it fancies.

  • Julien

    @ Physicalists

    1. The idea that our mind is a computation.
    2. Physicalism means two physically identical systems share all the same properties. Supervenience means that some properties are the sames despite not physically identical. Do you agree with that?
    3. “Maybe” more than “obviously”. To me this is an experimental question for when we will be able to test it.
    4. If we accept supervenience, which is part of the standard physicalist point-of-view, then we have to decide what system are conscious, as we know we are. But at this point there is just no experiment we can do to test it. This why this is hard. Maybe one day we will understand this better, and provide a description of consciousness as an emergent properties. I would bet on that. Or maybe this will requiere to include some modification of QM, as Penrose think. I don’t know, but the lack of experimental ways to test for consciousness -even in principle- makes this problem fondamentally different from a simple lack of knowledge.

    Sorry, I did meant to ask for a legal issue. My question should have been: would you consider human any program winning a Turing test, or just those that are constructed to emulate humans both from the point-of-view of behavior and inner mecanisms?

  • Physicalist

    @ Julien,

    1. But there’s no reason that accepting Effective Field Theories would imply that mental processes are nothing but computational processes. As I said above, one could accept that life and the mind are nothing but QED processes and still hold that something that is computationally equivalent (e.g., a computer simulation) is not mentally equivalent. This is because the QED descriptions of computers differs from the QED description of our brain.

    2. It seems like your account of supervenience is a bit fuzzy.
    (a) To say that some higher-level properties supervene on lower-level properties is just to say that the higher level properties cannot be different unless the lower level properties are different. Equivalently, if the lower level properties are the *same*, then the higher level properties have to be the same too.
    (b) Multiple realization is the claim that higher level properties can be the same even if the lower level properties are different.
    (c) The standard account of physicalism allows for multiple realization by saying that all higher level properties supervene on physical properties (it does not require that the higher level properties be *identical* to the lower level properties).

    3. Well, if the property dualists are right and consciousness has no physical effects whatsoever, then it’s going to be pretty hard to test. Fortunately, we have no reason to believe that they are right, and we can safely say that conscious states just are the brain processes that result in my saying, “There’s a tickling feeling in my left knee.”

    4. We do face a problem in that we don’t have a good science of mentality right now. But this set of problems is what Chalmers calls the “easy problem” of consciousness. Once we have an account of belief, desire, representation, memory, psychological awareness, etc., there won’t be some extra “hard problem of phenomenal consciousness” left over.
    (And Penrose’s reasons for thinking that quantum gravity comes into play in conscious thought are unconvincing, to put it mildly.)

  • Justin Loe

    Essentially this post states that current physics is true and complete at the scale of everyday life. I think this is an uncontroversial statement. Put differently, are there any advances in theoretical physics since 1980 [edit] that add to what previous theories held about everyday life? I’m not sure that there are any. [If there are, that would be interesting to know]

    It could probably also be said that the pace of advances in theoretical physics, in terms of theories that are testable or falsifiable, has been minimal since 1980. Perhaps, we’ve already reached the point of diminishing returns in terms of advances in new theories, that can tested by experimental evidence. [a speculative statement, and certainly one to be made cautiously, since Lord Kelvin’s famous quotation, paraphrasing, “there’s nothing left to discover.”]

    [I am not suggesting that something akin to the “End of Physics” has occurred]

  • jpd

    since 1970 : chaos,
    sorry you just changed your cutoff to 1980
    i’ll get back to you if i think of anything

  • Justin Loe

    @jpd: That seems like a reasonable example. Still it may be that since Mandelbrot’s work was accepted in the scientific community (~early 1980s?), there have been no advances since then in theoretical physics as applied to everyday life, and no apparently testable advances.

  • Julien

    @ physicalist.
    1. You have no choice to accept computationalism once you accept current EFT.
    2. Sure. It contredicts your previous point, thought.
    3. As I said, we have experimental evidences that this issue is not as obvious as you may think.
    4. Well, thanks for the discussion, and let’s agree to disagree.


    Decoherence maybe?

  • Justin Loe

    @Julien: At the moment, decoherence is a competing hypothesis, but unproven. So it’s not yet an established theoretical advance. Perhaps it has a better chance of experimental testability, though.

  • Oleg

    @Justin: How would you define domain of “everyday life physics”? How did the set of questions about “everyday life physics” changed since 1900’s? Were any new questions added since then (don’t mind the answers) ?

  • Justin Loe

    @Oleg: I think I’m just using the definition that Sean is using which is the domain of our scales of experience, i.e. essentially conceivable scientific applications in everyday life. Even if some alternative to relativity or quantum theory were developed, my understanding of Sean’s argument is that at the scale of our experience, such as engineering applications, chemistry, biology, and electronics, the predictions of that new theory would be empirically identical to existing theories. At different scales, a new theory would more accurate.

    I believe that was the intent of the analogy that Newtonian physics is true at a certain scale, and not true, clearly at relativistic speeds. That’s my interpretation.

    Of course, it is conceivable that some new theory could have an impact at our scale of experience, but that impact would likely not be significant.

    [Of course, predicting the course of science is a bit like predicting the weather 1,000 years from now]

  • Hilbert space
  • Oleg

    @Justin: How does second law of thermodynamics relate to all this? Imagine you already know quantum theory, standard model of particles and theory of relativity, but you don’t know thermodynamics. Will you still need second law to explain “everyday life” physics? And how can you a priori figure out what’s missing?

  • Justin Loe

    [some amateur thoughts on your question]
    @Oleg: Well, we don’t see a broken egg reassemble itself; we don’t see high entropy states spontaneously converting into low entropy states. So, the other problem I’ve read about is that there is no arrow of time in quantum theory, the standard model, or relativity. We have experience of a succession of events, of remembering the past, and not remembering the future. If we want to account for our experience of time in this sense, the second law of thermodynamics has been invoked as an explanation, since the direction of events is from low entropy to progressively greater entropy. From my reading, there’s no arrow of time in quantum mechanics. In relativity theory there’s a block universe, and so the experience of the flow of time is an illusion, and the standard model, according to Baez,, has time reversal symmetry. So, as I read it, the arrow of time can’t be derived from the standard model or relativity theory.
    The textbook derivation of the 2nd law was by Boltzmann, but, apparently, the 2nd law can also be derived from quantum mechanical systems, which also increase their entropy over time [yet are time symmetrical].
    Yes, the second law is certainly required to explain “everyday life” physics or to explain why we don’t see a gas remain condensed in a small region of that space rather than spread throughout a given space, or why we perceive the flow of time from past to present to future.
    I believe you’re also asking how to derive the 2nd law? Well there’s a set of observations that a gas spreads throughout a given volume, that objects decay over time, etc. Without the second law it wouldn’t be possible to explain why don’t see high entropy -> low entropy changes, such as spontaneously growing younger.
    [It’s a little puzzling as to why it seems that the 2nd law can be derived from quantum mechanics and yet quantum mechanics is itself time symmetrical. I’m not familiar with this issue.]

  • Justin Loe

    EDIT: I just realized that the arrow of time is apparently a primary area of expertise for the author of this blog. Caveat: this is definitely not my area of expertise.

  • Sean the Mystic

    I think it’s wonderful news that the laws of physics of everyday life are completely understood, but the reason science still fails, and religion wins, is pretty simple: physical laws of fields and particles don’t offer any narrative or guidance for everyday life — they’re utterly devoid of purpose.

    Atheism will never eradicate religion because religion provides a higher myth to live by, which is what people really crave. Until science can find an inspiring story, maybe something like what Carl Sagan offered but more overtly religious, it will continue to lose to the religious myth-makers.

  • Justin Loe

    ref: Apparently Dr. Charles Bennett believes that quantum mechanics ” helps resolves the paradox or puzzle of the origin of the second law of thermodynamics”, see lecture:

  • Baby Bones

    After embarrassing myself with speculations predicated upon long-lived neutrons, I have to ask, IS there a standard model explanation for the stability of the neutron in an atomic nucleus?

    To me, there seems to be a scale gap in knowledge separating QCD and nuclear physics. I recently did editing work on a science paper that involved the accurate calculation of the half life of a certain popular element that was done on a ginormous computer. What was interesting to me was that no mention of the standard model was made by the authors, despite it being a fundamental study and despite it involving a number of calculations that is so stunningly high I would break my non-disclosure agreement with the authors’ institutions by mentioning it. The authors reasonably assumed that quarks and gluons are at such a high energy scale they would never affect the nuclear physics of atoms.

    But, I had to go only one step further in asking myself if the standard model accurately predicts the lifetime of the neutron outside as well as inside the nucleus.

    I fuzzily checked Wikipedia, and it doesn’t say for sure how the lifetime outside the nucleus is calculated in the standard model. Note also that measurements of the precise lifetime seem to have significant error associated with them, so I wonder if the standard model’s predictions are considered to be accurate enough in this regard. A quick glance seems to indicate to me that the standard model should be able to give a number for the lifetime.

    On the other hand, regarding the stability of the neutron inside the nucleus, all I could get from Wikipedia is “When bound inside of a nucleus, the instability of a single neutron to beta decay is balanced against the instability that would be acquired by the nucleus as a whole if an additional proton were to participate in repulsive interactions with the other protons that are already present in the nucleus” (citation needed).

    The above explanation neither mentions the standard model nor sounds very convincing. Another source mentioned that the Pauli Exclusion principle is the reason for the stability of the neutron in the nucleus. More convincing, to me, is when one calculates the energies of free particles making up the nucleus and compare that total with the energy of the bound system.

    But I have to contrast this cookbook binding energy calculation with the standard model picture. Does something in the standard model prevent a quark changing from down to up and undergoing subsequent beta decay when it is inside one nucleus, say a deuterium nucleus, but not another, say iodine 131?

    More generally, can the standard model account for the magic numbers of nuclear physics?

  • Justin Loe

    @Baby Bones: Try posting that question at Physicsforums: There’s a good mix of advanced graduate students and a few professors under pseudonyms there.

  • Charon

    @jpd and Justin Loe: chaos isn’t fundamental, though. It’s emergent. It doesn’t involve any new fundamental theories of physics. (Not that it’s not interesting – most people, even most physicists, spend their lives studying things that are emergent.)

    @Oleg and Justin Loe: thermodynamics is reasonably easily derived from statistical mechanics, which is just an application of your underlying dynamics (classical or quantum). It’s only this last level Sean is calling fundamental. (The quantum version, anyway – the classical version can be derived by taking hbar -> 0. Except, sadly, general relativity.) Sean’s book about time/entropy/etc. is a pretty good read.

  • Charon

    @Baby Bones: it’s been a long time since I’ve taken nuclear physics, but as I recall, you can derive the magic numbers from the nuclear shell model. This was approximate the way we did it in undergrad, but presumably the actual hardcore method is better. A quick google scholar search turned up this review, although that may not be much use to you if you aren’t at a university that provides a subscription to that journal, and don’t have a PhD in physics, perhaps. It does at least tell you (in the abstract) that we have a fair but imperfect understanding of this.

    And on the lifetime of the free neutron, this article has an equation for the Standard Model prediction. (Which they say is from this paper, though a little manipulation is involved.) There are parameters in this equation that have to be measured experimentally, and others that can be calculated to high precision. The Standard Model has a lot of input that it needs… can’t predict everything. (Although note that this is not my area of expertise – I only care about electrons, and, well, I guess protons too. And dark matter. But forget neutrons.)

  • Justin Loe

    @Charon: What’s your opinion on the fact that the arrow of time is only found in the 2nd law of thermodynamics but not relativity, or quantum mechanics or the standard model? Admittedly, this wasn’t really the topic of Sean’s post, but is it correct to state that the arrow of time, i.e. the experience of time that we have, is currently only a result of the 2nd law as derived from statistical mechanics but not the three fundamental theories? (that is, the three fundamental theories all exhibit time reversal symmetry?

    Essentially, then is the 2nd law of thermodynamics required to account for our experience of the flow of time, or is the flow of time found in fundamental theories?

    Or, is it possible that the flow of time is itself an illusion as Julian Barbour,, has advocated?

    Thanks for the responses.

    Barbour’s take on the arrow of time is to dismiss that the universe formed from a “special” low entropy state, and to suggest that, instead, it is eternal, and has passed thru an infinite number of states, and that accounts for the particular low energy state that gave rise to our particular universe, at least as I read his interpretation.

  • Loki

    Julien, sorry for late reply, i live in a wildly different time zone.
    Off course, i won’t consider “human” any AI, whether it emulates human behavior or not. No more than my parrot is human when it pronounces “Nice bird Pushy!”. It is a different animal anyway :-)
    Doesn’t mean i’d feel ok to offend it. No more than hit a dog.

  • Justin Loe

    @Charon: Let me summarize, briefly: is it troubling that all the fundamental theories, which seem to explain all of “everyday” life, do not explain the arrow of time, and our experience of it?

    [I had another edit on the above post, but I ran out of time…]

  • Justin Loe

    EDIT of previous post:
    Apparently this question has already been asked as Loschmidt’s paradox: “objection that it should not be possible to deduce an irreversible process from time-symmetric dynamics. This puts the time reversal symmetry of (almost) all known low-level fundamental physical processes at odds with any attempt to infer from them the second law of thermodynamics which describes the behaviour of macroscopic systems. ”'s_paradox (for some reason the link isn’t working, but I’m just referencing the wikipedia article on Loschmidt’s paradox)

  • Oleg

    @Justin: There are two points which are troubling me.
    The first point is ambiguity of the dividing line that separates laws of physics from mere boundary conditions. For example, it is clear that exact value of the distance between the Earth and the Sun is not a law of physics: the Earth’s orbit could be 1 million km closer or 1 million km farther from the Sun, and no law would be violated. I cannot see how the fact that the Big Bang had very low entropy differs from billions of other facts about our Universe. Still it is necessary to know boundary conditions of our universe in order to explain the arrow of time (and second law). The similar thing is dark energy versus matter/antimatter gravitational repulsion ( explanations of expansion of the Universe. How can we discriminate between the “law of physics” (lambda-CDM model) and “boundary condition” (living in a Universe where matter and antimatter have already clustered in separate galaxies) before measurments of gravitational interaction of antimatter? Of course, this is far beyond the realm of “everyday life” physics, but I wonder, how can we prove that laws of physics known today are not an emergent properties of our specific Universe?

    The second thing that is troubling me is that once we know all reversible laws of dynamics, we don’t really need second law of thermodynamics. We could have said that we already understand the laws of physics underlying everyday life, and this statement would be correct. Moreover, the question “why a table is solid?” has a simple, plain and correct answer “because it is made of wood”, so we don’t really need relativity, standard model of particles and quantum mechanics to generate correct explanations of “everyday life”. In general, I think that Sean’s statement cannot be falsified.

  • Loki

    Whether people 1000 years from now will need the same basic laws to explain everyday life, depends not on the progress of physics, but on the progress of technology, i.e.”everyday life”! Hence i think that Sean’s statement is wrong.
    You don’t need relativity to explain solid table, but you do need it to explain GPS navigator. And you can’t explain some modern gadgets without QM. A hypothetical time traveller can be sure to meet gadgets in 3000 A.D., that will be totally ordinary stuff for people of 3000, but seem a total magic beyond comprehension to him. Like IPad to Isaak Newton.

  • jpd

    chaos isn’t fundamental?
    the fact that i cant predict a n body orbit with arbitrary
    accuracy isn’t fundamental?

  • Justin Loe

    “how can we prove that laws of physics known today are not an emergent properties of our specific Universe”
    The project as I see it of various GUT approaches is to provide a theory that will account for the variety of constants that are in the standard model and which have arbitrary values. Unfortunately, none of these have been successful up until this point. Unanswered also is the question which is whether the particular physics of our universe is the only possible physics, or whether it is an emergent property of the initial conditions, and, in other universes, an entirely different set of physical laws applies.
    If one solution is the multiverse, which suggests the realization of all possible configurations of physical laws in other universes, it is not at all clear why that doesn’t produce the same outcomes as saying the initial entropic state can assume any possible set of configurations.
    Although it is possible that the multiverse is the explanation, that appears to explain physics via an infinite set of possibilities. That’s clearly at odds with Occam’s Razor. If a multiverse theory yields the same set of predictions as current theories, in what sense would it be testable? A brief search reveals that Tegmark argues that the information content of a multiverse would be lower than a single universe explanation. Puzzingly, an invocation of Occam’s Razor is itself problematic since it also seems that previous researchers erroneously favored proteins over dna as the carriers of genetic information, but that was obviously proven incorrect. So, intuitions about whether a particular explanation is or is not more parsimonious may not be a good guide that the theory is correct.

  • Benji

    We need to be clear what we mean by the term “understood”. If we mean it in the sense that given a set of inputs we can accurately predict the outputs, then the physics of everyday life is definitely understood.
    If, however we mean that we have a complete explanation of the physics of everyday life, then I think this is much less clear.
    Consider Newtonian gravity; this provides the necessary predictive power (ignoring gps and a few other things which arguably are part of everyday life). So without GR we could say that we “understand” gravity on this scale. So would we say that GR has no more value as a theory in everyday life? No, because GR is more than just it’s predictive power. It provides a better explanation of what is really going on with gravity.
    It is in this sense that I expect our ideas about the physics of everyday life to change in the coming decades. Yes, we’ll still have electrons, protons etc. but we’ll understand a bit more of the why.

  • Julien


    >Off course, i won’t consider “human” any AI, whether it emulates human behavior or not.

    If it looks like human behavior and moos like a human, then it is probably a cow. 😉

    But ok, allow me correcting my question again: would you consider self-conscious any program winning a Turing test, or just those that are constructed to emulate humans both from the point-of-view of behavior and inner mecanisms?

  • Justin Loe

    Thanks to a good tip from scientist in the field, I found this paper,, which appears to offer a plausible derivation of the second law of thermodynamics from quantum physics.

  • Baby Bones

    Thanks for the references. It’s good to know that SM has a strong connection to nuclear physics in that it can predict the decay of a neutron, and I checked your reference on the shell model to see if the SM can account for a nucleus environment, but there’s no mention of SM in the abstract.

    I imagine the only thing needed to validate the quark gluon picture is the existence of a strong force that the quarks of the neutron feel attracted to, and that in turn reflects the lower total energy of the neutron in comparison with its constituents.

    The quark-gluon picture is, to me at least, a far cry from a simple attractive force , and it is something that has always bothered me as being a bit unphysical. The gluon stretches while confined in a flux tube until another particle-antiparticle pair is formed in its place and the attached quarks are strongly confined. Furthermore, despite the confinement, a residue of the color force leaks out and is seen as the strong force. I don’t want to sound impolite but that idea smacks of convenience rather than insight even if it is a reasonable extension of SU2 for photon exchange in the electromagnetic field. Evidence of the quark-gluon plasma makes me feel a bit less uneasy, since I think more evidence for the standard model is what is needed.

  • Lab Lemming

    If Sean’s statement about everyday physics is correct, then does it follow that basic physics research no longer has practical societal value?

  • Aleksandar Mikovic

    Certain phenomena of the everyday life can be understood by using the Standard Model, but there are plenty of other phenomena (like consciousness, emotions, social interactions etc.) which cannot be explained by SM. The basic reason are the Goedel’s theorems in logic, which state that for any mathematical theory like SM, exist infinitely many undecidable statements, i.e. the statements which cannot be proven from the initial postulates. Hence for any physical theory there will exist phenomena in its domain of validity which cannot be explained.

  • Loki

    If an AI can win a real Turing test – and let’s say we mean by TT a reasonably long conversation with a very intelligent human, say me (:-)) – than it has to be as “self-conscious” as you! Sounds ridiculous and reminds you of Chinese Room argument? But consider this:
    I can choose to converse with it exactly about introspection and consciousness problem and philosophical zombies, in a way we do now. If AI can respond to a joke about mooing cows, for example, than it need subroutines that detect humor, irony, intentional stance of an opponent, relevance to other topics being discussed and a lot of other stuff. Basically, it has to do the same deconstruction as you. And the same subroutines for constructing response – among other things: when to answer with joke? with sarcasm? use some other rethorical trick? put a smile?
    Now, i can not easily imagine how one can discuss introspection and lack one at the same time. Could be just a lack of imagination though .. ))
    So, we know it is “just” an algorithm, but .. not all people, frankly, possess conversational algorithms of such complexity! As i consider self-consciousness nothing more (and less!) than a set of algorithms of vast complexity, operating in some computational substate (a brain in human case), including modules for self-assesment (=introspection) – such an AI is clearly self-conscious to me.
    Why .. imagine i’m actually a smart program here. What would be your argument agianst my self-consciosness ?! :-)

  • Julien


    Fun that, at least one time in my life, I can take the anticomp side :-)

    Well I will examine you from the inside (I’m biologist), and notice that in fact your answers have been produced by tossing a coin. That was very unlikely to see such “human like” text, but that does not violate any physical law. Dude I was discussing with a coin! Was the coin conscious?

    Well I will examine you from the inside (I’m biologist gniark gniark), and notice that in fact your answers were deterministically chosen from a big table that contains any possible answers allowing to pass a 5 minutes TT. Dude I was discussing with a table! Was the table conscious?

  • Loki

    Exponential branching produces big numbers very fast indeed. As a mathematician I bet the complexity of an intelligent 5 minutes discussion is such that:
    – the probability of it being produced by a coin tossing is negligible compared with the life time of the Universe;
    – the table one needs to produce it has more entries than the number of paricles in the Universe.
    Hence it just has to be an algorithmic process! and it has to be comparably complex to the one used by an actual human brain.
    So you were discussing with an algorithm! And it was as conscious as you are.
    .. Well, no soul there, but i don’t claim to have one ))

  • Alan

    “Just because there is something we don’t understand about some phenomenon (superconductivity, cancer, consciousness) does not imply that everything we think we know might be wrong.”

    But can what we know so far incorporate other possibilities.
    I came across this recently and this psychology professor is very very certain of the phenomena he and his fellow scientists witnessed over several years – basically consciousness without the so-called physical. I find these experiments/observations eternally fascinating. No explanations as yet.
    Of course the setting makes many balk but well…just listen to the full extract.

    There is also tremendous scholarship involved in some of the studies of these supposed “other properties” of life: e.g. Dr. Alan Gauld:


    “Conscious algorithms… And it was as conscious as you are.
    .. Well, no soul there, but i don’t claim to have one.”

    Don’t be too sure. There seem to be a few “promissory materialists” above who are quite cocksure (but haven’t worked it out yet) that you can only have awareness inside physical brains – you know the brain is a computer, make it all complex enough and up consciousness pops (and just in the brain). But the phenomena reported above seem to hole this because IT is there, quietly existing and thinking and with no apparent physical support.

    You have to go with the phenomena seen first, as the good professor above reports, then go from there (somehow). I think this – consciousness researchers will never, ever, solve the problem of what consciousness/awareness is without taking this stuff into account.
    They will publish and be cool and maybe convince others that they are getting there.
    Of course physics may incorporate such phenomena, just as Feynman said fluid dynamics contains Barber poles and other things – but I doubt it though.

    What physics can explain a complex organized structure, with sentience, existing apart from the brain? – answers please.

  • Julien

    Did you hear about the following equation? claim>>evidence=>don’t give it a shit

    Ok now you get use to my Socratic style, so let me change my question again :-)

    Is ELIZA conscious?

  • Alan


    The problem with your remarks is that it looks as if you are unaware of the evidence. One must put aside prejudice and see with new eyes. So important here. Firstly a huge range of phenomena were displayed; as example:

    “The Lights. The light phenomena were among the most dramatic features observed by the investigators. In most cases, these phenomena were consistent with those reported by past investigators in other settings. Briefly the lights consisted chiefly of the following.

    *Single light points, varying from the size of peas to that of medium-sized glass marbles, which variously darted around the room at great speed, appeared to pass through the surface of the seance room table (appearing immediately underneath in areas inaccessible to the Scole Group), settled on outstretched hands for close inspection, sustained circles in mid-air at a speed and with a precision inconsistent with manual manipulation (often “switching” off various segments of the circle), responded to requests and apparently entered investigators’ bodies, entered crystals placed upon the table and either illuminated the whole crystal or moved as a small point of light throughout their structure, entered a glass dome in the center of the table.

    * Small lights which appear to enter, illuminate and levitate crystals.” See:

    A documentary by a leading UK investigative reporter was produced over several years:

    The Director, Time Coleman, responds here to a similar but very biased critique:

    “This skeptical analysis is well intentioned, but so full of inaccuracies it completely discredits itself. I produced and directed the documentary – The Afterlife Investigations – in which I thoroughly examine all the evidence for the Scole Experiment. I spent several years interviewing all the leading participants and I got to know them all well. As unbelievable as the activities at Scole are I found no evidence of fraud. The authors [the skeptical commenter] arguments like – I consulted with a colleague who told me its possible to remove a luminous arm, therefore all experiments which used this control at Scole are fraudulent – are childish in their logic. Given the space I could demolish this entire analysis – but its easier if you watch the documentary.”

    These comments speak for themselves about the reality of these phenomena – evidence for consciousness/awareness without physical brains.

    And please do not swear – thanks.

  • Loki

    Look … all “spiritual” stuff is just boring. Looking for gods, ghosts, IDesigners and other transcendental cheburashkas reveals nothing but lack of imagination, in my opinion. Not interesting for creative sentient beings, really :-)
    It depends on what you mean by “Consciousness” (“C”). If that only relates to the ability to construct some internal identity, than probably only humans possess this “C” among animals. And one Julian Jaynes (google it, very cool reading, though a bit fantastic) claimed that Achilles and other Iliad heroes were NOT conscious in this sense. That this “C” evolved as a cultural phenomenon around 3000 years ago (before that people were like schisophreniacs or very drunk, smth like that).
    If we take a wider notion of “C”, like the ability to react to changes around, form some intentions etc. Than i’d say that a Crow is less conscious than a Human, but more conscious than a Cow, which is more conscious that a Fruit-fly. How it relates to a Dog – i don’t know (probably higher, as it was shown that crows can solve some puzzles without trial-and-error, hence have some introspective abilities. nothing like that was shown for dogs). Where os Elisa on this scale? Does it react and form intentions? Sure, it reacts to your question and intends to answer it, and does it. It doesn’t “think” about it’s actions, but that relates to the strong concept of “C”. Besides, 99% of human activity is unconscious in this sense. When you brush your teeth in the morning or drive a car to the office – do you “think” about it?
    Still, i guess a Fruit-Fly is much more consiouis :-)

  • Alan


    “Look … all “spiritual” stuff is just boring…” Mmm…

    Actually, you mentioned “spiritual” not myself. As to rest, well they couldn’t be further from my mind.

    Let’s be very clear here. These are multiply witnessed phenomena – evidence from scientists such as fellows who post here. So not “boring”! And as Professor Fontana says in the video above (@63), “I must stress, it changes your paradigm”. So… interesting! Paradigm changes are thus.

    It would have been great to see Dick Feynman as a witness to these little buzzing lights, bouncing off tables, entering his chest even (as happened BTW). He would have seen what they saw and wouldn’t have found the “strings” (didn’t like strings anyway).

    If it’s happening in the universe it should be studied – that’s science.

  • Julien


    Thanks for the link, I’ll take a look. Notice that if you think that, then you don’t really trust TT but rely on the idea that human consciousness depends on the content of its information processing.

    To me, but I can’t change my mind, consciousness is likely a feature that happened as part of the way our brain evolved to work, especially the neocortex. I’d expect that it’s almost a on/off phenomenon we share with Achilles, Apes, Elephant, Dog, but not Fruit-Fly, and the boundary should be somewhere arround Snakes.

    I’d also guess that we can software it, the day we will understand how it works in our brain, but I’m not sure we will one day be able to asses consciousness in non brain-like programs. My point with ELIZA was that we agree it’s less conscious than a Fruit-Fly, but that program already passed some form of TT. In the same vein, I don’t think it’d be so difficult to fill a table which could discuss hours and hours about any of the usual transcendental cheburashkas. Maybe we should do it and spare some time :-)

  • Ian

    Unfortunately, this post doesn’t rise above information consumerism. It’s welcome rhetoric for materialists who want to see their views confirmed, but it doesn’t participate in the real debate. Here are the problems:

    1. Dismissing consciousness as just “complicated” demonstrates ignorance regarding the problems qualia and intentionality pose for physicalism. If Dr. Carroll wants to make a case for his claim, he needs to educate himself regarding basic philosophy of mind. As it stands, he’s providing a straightforward example of an expert in one area naively assuming that he knows more about an issue outside his area of expertise than he really does.

    2. Dr. Carroll has given no reason to suppose that the range of validity in which physical theories work doesn’t end at consciousness, just as the range of validity in which Newtonian physics works ends at curved spacetime. In fact, if an experiment were to show that there’s something involved in a conscious system which physics can’t account for, that would in no way invalidate everything we know about how physics works for systems which do not involve consciousness. His conclusion does not follow from his argument.

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Cosmic Variance

Random samplings from a universe of ideas.

About Sean Carroll

Sean Carroll is a Senior Research Associate in the Department of Physics at the California Institute of Technology. His research interests include theoretical aspects of cosmology, field theory, and gravitation. His most recent book is The Particle at the End of the Universe, about the Large Hadron Collider and the search for the Higgs boson. Here are some of his favorite blog posts, home page, and email: carroll [at] .


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