One Last Stab

I’ve been too busy to contribute much to the laws of physics discussion, and now I’m about to hop on a plane to bluegrass country. But I am sincerely seeking the best way to make this point clear, so one more quick try. And I do appreciate the back-and-forth thus far; sometimes frustrating, but certainly very useful to me.

If you were to ask a contemporary scientist why a table is solid, they would give you an explanation that comes down to the properties of the molecules of which it is made, which in turn reflect a combination of the size of the atoms as determined by quantum mechanics, and the electrostatic interaction between those atoms. If you were to ask why the Sun shines, you would get a story in terms of protons and neutrons fusing and releasing energy. If you were to ask what happens when a person flexes a muscle, you would hear about signals sent through nerves by the transmission of ions across electromagnetic potentials and various chemical interactions.

And so on with innumerable other questions about how everyday phenomena work. In every single case, the basic underlying story (if that happens to be what you’re interested in, and again there are plenty of other interesting things out there) would involve the particles of the Standard Model, interacting through electromagnetism, gravity, and the nuclear forces, according to the principles of quantum mechanics and general relativity.

One hundred years ago, you would not have heard that story, because it hadn’t yet been put together.

But — here’s the important part — one thousand years from now, you will still hear precisely that same story.

There might be new layers underneath, but it won’t be necessary to refer to them to give a sufficient answer to the original question. There will certainly be much greater understanding of the collective behavior of these underlying particles and forces, which is where most of the great work in modern science is being done. And hopefully there will be a deeper story about why we have the laws we do, how gravity and quantum mechanics play together, how best to interpret quantum mechanics, and so on.

What there won’t be is some dramatic paradigm shift that says “Oops, sorry about those electrons and protons and neutrons, we found that they don’t really exist. Now it’s zylbots all the way down.” Nor will we have discovered new fundamental particles and forces that are crucial to telling the story of everyday phenomena. If those existed, we would have found them by now. The view of electrons and protons and neutrons interacting through the Standard Model and gravity will stay with us forever — added to and better understood, but never replaced or drastically modified.

I’m not actually trying to say something controversial. I think it is pretty unambiguously correct, once I actually say it clearly. But it’s something I think is not as widely appreciated as it really should be.

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60 Responses to One Last Stab

  1. bete noir says:

    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.

    Whereas I mostly agree with you, on behalf of all contrarians in this world here’s my attempt at a counterexample of the kind you describe. There’s an everyday phenomenon that is, to say the least, not well understood: mass. We know the masses we experience in our everyday lives are related to confinement and chiral symmetry breaking in QCD, but don’t know exactly how those happen.

    Now, imagine that 100 years from now somebody would be able to give an explanation for confinement and chiral symmetry breaking in QCD as simple and intuitive as Einstein’s explanation of the photoelectric effect. Wouldn’t that explanation deserve the title of “basic law of Nature”? I think it would. So, people living in the next century would rightly say “Well, that guy Sean Carroll didn’t really know the most basic law of everyday life, how ordinary baryonic matter has mass.”

  2. Slide2112 says:

    ugh. Always a dissapointing moment here at CV. Wood builds a beautiful home so why consider anything else?

  3. Boaz says:

    @bete noir, 51
    But, it sounds like you’re saying that the explanation would still be in terms of QCD, so it doesn’t violate the standard model.

    We say the table is made of atoms, and the atoms are made of protons, neutrons and electrons, and the protons and neutrons are made of quarks. And we can rearrange those basics in our accelerators and predict the results. We understand some aspects of the standard model, and so we say that we understand the table.

    I think this way of looking at things would say that the future mass law (or explanation) is not a basic law of nature. Or at least, the standard model rules are the underlying story.

    This line of thinking is certainly important in order to support particle physics, cosmology and other “basic” research. Once one gives up on finding practical results from one’s research, you do have to have explain why other people should support you in what you do. Being part of a generally healthy intellectual adventure and attempt to come to terms with our world is certainly one approach to interact with other people. But if it comes across as, “our theory is the best, it underlies everything, and no, I can’t really explain it to you”. Then its hard to keep people’s interest and support. And not just non-scientists. Chemists who mainly rely on non-relativistic quantum mechanics, and a lot of other stuff, or biologists who use some physics concepts, and some other stuff may also not want to support basic physics research if its not relevant to what they do.

  4. bete noir says:

    But you still cannot tell me how matter gets a mass.

  5. bete noir says:

    To be more explicit: yes, of course, in my hypothetical example the answer would still be in terms of the SM. It obviously couldn’t be otherwise. But not necessarily in terms of quarks and gluons, and that’s the point. The relevant degrees of freedom may be completely different. Just like in the photoelectric effect the relevant degrees of freedom are not the electromagnetic fields, but the photons.

    Hand-waving arguments about chairs made of atoms will not cut it. We do not know the origin of baryonic mass.

  6. Boaz says:

    But how is this different from say high TC superconductivity? Ok, not exactly an every day phenomenon. But the basic elements that give rise to it- the “mechanism” behind it, isn’t understood.
    I’d guess there’s still things about turbulence that aren’t understood, and other weather phenomenon.
    The point in understanding such a thing is to find the right degrees of freedom. Find a few basic element that work together in a certain way, and show that the phenomenon you’re interested in comes out of that. With weather phenomenon, one expects that some fluid mechanics equations may be sufficient. Sean is saying we can do it all “using” the standard model and general relativity, and you seem to agree. The photoelectric effect was different in that photons were not really a part of the existing E&M, classical mechanics, etc of the time. It seemed quite hard to say what this photon thing was. And it really only made a bit more sense with quantum mechanics.
    Maybe you’re saying that in some sense the solution to the mass problem would use such weird degrees of freedom, that in some sense they really wouldn’t fit into the standard model all that well?

  7. bete noir says:

    But how is this different from say high TC superconductivity? Ok, not exactly an every day phenomenon.

    Exactly, I didn’t mention high-Tc superconductivity because it’s not part of our everyday experience (yet).

    Maybe youu2019re saying that in some sense the solution to the mass problem would use such weird degrees of freedom, that in some sense they really wouldnu2019t fit into the standard model all that well?

    A good example is low-Tc, BCS superconductivity. Explaining it didn’t require drastically changing QED, say at the Lagrangian level. But it did require extending it non trivially. The notion of dynamical breaking of U(1) gauge symmetry by an electron-pair condensate may seem familiar now, but it was very tough to figure out at the time BCS did. It is a non-trivial, non-perturbative extension of our notion of QED.

    Similarly, our understanding of baryonic mass will doubtlessly happen in the context of QCD, but it will probably require a similar non-trivial extension of our notion of what QCD is in the non-perturbative regime. Whether it will involve some kind of duality, holographic formulation, topological degrees of freedom, whatever, we don’t know yet. But then, that means we still don’t know what the fundamental physical law is that governs mass generation in ordinary matter.

    (Or, to be precise, the generation of 90% of the mass of baryonic matter. About 10% or so comes from quark masses, and for those we do not even know what the microscopic law is. Maybe the SM Higgs mechanism, or something else. The LHC will tell, hopefully.)

    (By the way, that’s another counter example to Sean’s statement. We do not know what microscopic law gives rise to about 10% of our own mass. And no, it’s not beer.)

  8. Boaz says:

    Good points, bette noir.
    I guess your distinction gets at what we mean by a fundamental physical law.
    In the case of low-Tc superconductivity, would we say that the fundamental law is the BCS mechanism, or is it QED?
    It seems to me that the basic theories (classical E&M, QED, stat-mech…) are kind of like tool kits out of which to build more specific theories/models. And they may even come in different forms, like we have Lagrangians or Hamiltonians or forces for classical mechanics. And we have wave functions, or matrix operators or Wigner functions for quantum mechanics.
    I think things like axiomatic quantum field theory aren’t very popular because we like to have a little bit of wiggle room in our basic theories so we can mold them to fit the phenomena we actually want to describe.
    With string theory, we could say that it hasn’t been very easily able to describe the standard model, so it hasn’t been widely used. But they have tried to use it to describe condensed matter and nuclear physics phenomena.

  9. Boaz says:

    I guess this comment thread is done, but here’s a philosophy thesis I’ve been trying to read that formalizes the “More is Different” idea that would say that the microphysics laws aren’t the only fundamental ones. http://philsci-archive.pitt.edu/8339/. I think it might put the claim of bette noire on stronger grounds- that different degrees of freedom may imply new laws. He goes into a lot about symmetry breaking.