Big Picture Part Three: Essence

One of a series of quick posts on the six sections of my book The Big PictureCosmos, Understanding, Essence, Complexity, Thinking, Caring.

Chapters in Part Three, Essence:

  • 19. How Much We Know
  • 20. The Quantum Realm
  • 21. Interpreting Quantum Mechanics
  • 22. The Core Theory
  • 23. The Stuff of Which We Are Made
  • 24. The Effective Theory of the Everyday World
  • 25. Why Does the Universe Exist?
  • 26. Body and Soul
  • 27. Death Is the End

In Part Three we get our hands dirty diving into some of the central features of how our world actually works: quantum mechanics, field theory, and the Core Theory describing the actual particles and forces that make up the visible universe. The discussion of the basics of quantum mechanics itself is quite brief, and I mention the Many-Worlds formulation only to emphasize that there’s nothing about QM that implies we need to be idealist, anti-realist, or non-determinist. (Those options are open, of course — but they’re not forced on us by what we know about quantum mechanics.)

More directly relevant to this discussion are the ideas of effective field theory and crossing symmetry that let us conclude the laws of physics underlying everyday life are completely known. (I used to say “…completely understood,” but too many people chose to quibble about whether we “really understand” them rather than grasping the point, so I’ve switched to “known.”) (No, I don’t think it will really help either.) In early drafts I went on a bit too long about all the quarks and gluons and so forth, since personally I think that stuff is endlessly fascinating. But it dragged down the pace a bit, so now I have an Appendix in which I give the full Core Theory equation and explain — tersely but accurately! — every single term that appears in it.

In the body of the text I concentrate more on explaining what the claim actually says and why it has a chance of being true. For example, why it doesn’t matter for everyday purposes that we don’t yet understand quantum gravity.

Physicists divide our theoretical understanding of these particles and forces into two grand theories: the Standard Model of Particle Physics, which includes everything we’ve been talking about except for gravity, and general relativity, Einstein’s theory of gravity as the curvature of spacetime. We lack a full “quantum theory of gravity” — a model that is based on the principles of quantum mechanics, and matches onto general relativity when things become classical-looking. Superstring theory is one very promising candidate for such a model, but right now we just don’t know how to talk about situations where gravity is very strong, like near the Big Bang or inside a black hole, in quantum-mechanical terms. Figuring out how to do so is one of the greatest challenges currently occupying the minds of theoretical physicists around the world.

But we don’t live inside a black hole, and the Big Bang was quite a few years ago. We live in a world where gravity is relatively weak. And as long as the force is weak, quantum field theory has no trouble whatsoever describing how gravity works. That’s why we’re confident in the existence of gravitons; they are an inescapable consequence of the basic features of general relativity and quantum field theory, even if we lack a complete theory of quantum gravity. The domain of applicability of our present understanding of quantum gravity includes everything we experience in our everyday lives.

There is, therefore, no reason to keep the Standard Model and general relativity completely separate from each other. As far as the physics of the stuff you see in front of you right now is concerned, it is all very well described by one big quantum field theory. Nobel Laureate Frank Wilczek has dubbed it the Core Theory. It’s the quantum field theory of the quarks, electrons, neutrinos, all the families of fermions, electromagnetism, gravity, the nuclear forces, and the Higgs. In the Appendix we lay it out in a bit more detail. The Core Theory is not the most elegant concoction that has ever been dreamed up in the mind of a physicist, but it’s been spectacularly successful at accounting for every experiment ever performed in a laboratory here on Earth. (At least as of mid-2015 — we should always be ready for the next surprise.)

Princess Elisabeth of BohemiaOne of my favorite chapters in the book is 26, Body and Soul, where I relate the story of Princess Elisabeth of Bohemia and René Descartes. And how, you may ask, does quantum field theory relate to an epistolary conversation carried out in the seventeenth century? Descartes, of course, was famously a champion of mind/body dualism. Elisabeth challenged him on this, asking how something (the immaterial soul) that had no location or extent in space could possibly influence something (the physical body) that manifestly did. The updated version of Elisabeth’s challenge is to ask, “How could an immaterial soul possibly affect the evolution of the particles and fields in the Core Theory? How should that gloriously precise and well-tested equation be modified?”

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11 Responses to Big Picture Part Three: Essence

  1. Vaal says:

    Dr. Carroll,

    I love your example of the story of Princess Elisabeth of Bohemia and René Descartes and I look forward to reading more about it in your book.

    The example ties in so well with what, to me, is one of your most important contributions in the debate between naturalism, and competing accounts – e.g. theism (and other “isms”), that is: What makes for a useful explanation?

    As you pointed out in your debate with W.L. Craig, the basic problem of theistic explanations is that they are “not well defined.” And this characteristic extends to “supernatural/non-natural” explanations in general. Supernatural explanations tend to share this characteristic: “I have to explain X, therefore I’ll posit a cause “Y” which has the power to do X. There, now I’ve explained X.”

    Left out is any plausible explanation of HOW “Y” could cause X, or why this explanation has any more warrant than multiple similar explanations. Once we allow such non-substantive, “ill-defined” explanations they are functionally the equivalent of “then a miracle happens” or “magic.” Nothing really seems explained, nothing selects it from multiple other magic explanations, anything goes and it leads to epistemic chaos. (Which, by no coincidence, is just what we see in religion – vast numbers of multiple incompatible claims flourishing, with no principled method offered to justify one over the other). **

    Unfortunately, as you touched upon in your debate, much of humanity is under the impression this abliity-to-explain-anything is a “feature” not a “bug” of supernatural explanations . In other words, the infinite adaptability of non-natural explanations seems to them a GOOD thing – it has greater explanatory scope, and can always take over whenever natural, materialistic explanations won’t satisfy. The fact naturalistic explanations (scientific in particular), being constrained to specific conditions and predictions, can be shown sometimes to be wrong is seen a “limitation,” a sign of the weakness of naturalism, not a sign of it’s strength.

    You are well positioned, thankfully, to explain how people have things the wrong way around.

    And the fact that you have both true scientific credentials allied with philosophical awareness and great communication abilities, puts you in the perfect position to show how naturalism is an outgrowth of keeping consistent with epistemic virtues that derive from answering foundational problems of knowledge.: how do we make sense of our experience? What exists? How do we assign causation? And given we can come up with multiple explanations for the phenomena of our experience, what principled method can we put together for assigning more confidence to one explanation over the others? Etc.

    It turns out the strategies that arise for dealing with those variables are the ones that lead inevitably to an empirical approach and ultimately to science – science being our best refinement of what it looks like when one is being “epistemologically responsible.” This is what makes science so incompatible with (current) religious claims to knowledge: you can’t on one hand affirm the justifications that led to doing science and just abandon them elsewhere and slap the claim “knowledge” on both.

    Unfortunately, a lot of scientists have somehow acquiesced to this sequestered view of science, either from a squeamishness of ruffling religious feathers, or an apparently unexamined acceptance of a division of “ways of knowing,” ceding morality, free will, religious claims and the supernatural etc to “other ways of knowing.” It seems to be the attitude of “Look, as long as you don’t claim what you are doing is science, then don’t worry, I as a scientist can’t have anything to say about it.”

    This to me is what is so exciting about your new book: it seems you are out to say not simply “this is what we know scientifically thus far,” but “this is the BEST WAY WE KNOW OF KNOWING thus far, here is why, and look where it leads when we use it to tie everything together in a coherent manner!”

    I can’t wait to read your book!

    Cheers,
    Vaal

    **(This is what I argued at length here in the comments section with some theists, after your debate with Craig. Craig and his acolytes posit that an Agent employing “free willed choice” as the only eternal entity able to cause the temporal beginning of a universe. But with no mechanism other than the equivalent of “magic” being offered to make this plausible, we can posit ANY entity – a Blark particle, a wet wash cloth, a nest of rowdy bunnies wearing laser-shooting bonnets – and add that they had the magic powers of existing eternally and causing the universe).

  2. James Cross says:

    Got the book yesterday and read the chapter on the mind body problem

    Your argument if I understand it right is that mind is just an arrangement or positioning of physical material (neurons and such). So mind would be material.

    Would your Core Theory also be material and an arrangement of neurons in your brain and mine (to the extent I understand it)? The Core Theory seems to have existence outside any particular arrangement of matter. It is expressed in paper and ink in the Appendix. It is expressed in bits and bytes sent through the Internet. You may have drawn it on a white board or scribbled it on a napkin. If other readers and I read about it and understand it, the arrangement of material in our brains is likely to different from the arrangement in yours. Is it possible there is only one real version of the Core Theory in your brain? Or is there something immaterial about the Core Theory and that transcends any particular physical arrangement?

  3. Torbjörn Larsson says:

    “Is it possible there is only one real version of the Core Theory in your brain?”

    How the symbolic processing in our brain handles external impulses is irrelevant to the reality of Core Theory predictions/observations (robust features, i.e. reality). The impulses that we react to, and have memories handling them, has no direct correlation with the symbols, either internal or external.

    In fact, the absence of coupling between the two symbolisms (on the black board, and in the brain) , guarantees that the brain symbols are not identical to CT equations and their predictions. That doesn’t mean that what we do with our brain/body system isn’t connected to what we see on the black board (say). Evolution guarantees that what our bodies do takes the external environment into account. (Hence memories, analytic abilities, learning, et cetera.)

  4. James Cross says:

    Torbjörn Larsson

    I think what is missing in the analysis is the notion of information, signalling. I am using that in very loose sense. A message takes shape in Sean’s brain out of a particular arrangement of matter. This message can be put into various forms and sent to others. The message itself is not material but it is dependent on the material for it to be transmitted. It is also dependent upon other conscious beings with contextual familiarity for it to be understood. The Voynich manuscript, for example, might be a message we do not understand because we lack the context.

    “Evolution guarantees that what our bodies do takes the external environment into account. (Hence memories, analytic abilities, learning, et cetera.)”

    In a strict sense this is probably correct, but you might not want to draw too many conclusions beyond that. Taking the external environment into account doesn’t necessarily require we have an accurate perception of it. It only requires we have a presentation of it that is adequate for evolutionary purposes.

    https://broadspeculations.com/2016/04/26/world-stuff/

    Th

  5. Ben Goren says:

    James:

    The message itself is not material but it is dependent on the material for it to be transmitted.

    There may be different definitions of the term, “material,” being used here.

    Basically, with the same confidence that Sean uses for his assertion that the physics of human scales are completely known, we know that Claude Shanon and Alan Turing completely laid the groundwork for communication and computation. Whatever the message is, it’s as much a property of physical bodily function as the words you’re reading now are a property of the bit-flipping and display projection of the computer systems between the two of us.

    Cheers,

    b&

  6. James Cross says:

    Ben,

    The message can’t be material in the sense that it is dependent upon a particular arrangement or positioning of matter because the same message can be transmitted with different arrangements of matter as long as the sender and receiver understand the meaning and intent of the arrangements.

  7. Ben Goren says:

    James, by that logic, mass also isn’t material. There’re seemingly-infinite combinations of matter that would have a mass of exactly one kilogram, so, clearly, the particular arrangement or positioning of the matter is irrelevant to the mass.

    …but I dare you to propose to our host that therefore mass can’t possibly be material…..

    Cheers,

    b&

  8. James Cross says:

    Ben,

    How is mass a message?

    Mass is just an attribute of matter. Messages require arrangements of matter but the actual arrangement is arbitrary as long as there is mutual understanding of the context.

  9. Ben Goren says:

    James, nowhere did I write that mass is a message — though, of course, it would be trivial to devise a mass-based messaging system.

    Rather, the point is that, if messages are immaterial because the specific arrangement of matter is irrelevant to the message, then mass is equally immaterial because it also meets that definition.

    b&

  10. James Cross says:

    Ben,

    You’re missing the fact I said “messages require arrangements of matter”.

    Mass doesn’t. So the analogy doesn’t apply.

  11. Ben Goren says:

    James, if you sincerely think you can have mass without matter, then you need to remedy the defect in your basic science education by starting over again at the very beginning. Or, if you think you can use a balance scale (in its standard mode of operation) to differentiate between a kilogram of lead and a kilogram of feathers, you again need a remedial physics education.

    That is a direct and perfect analogy to the point you’re trying to make — that, for example, it makes no difference to the message, “ATTACK AT DAWN,” if you encode it in ASCII or EBCDIC or Morse or semaphore flags.

    So, again, either you’re right and the message is immaterial because you’ve still got “ATTACK AT DAWN” no matter how you encode it, in which case mass is also immaterial because you’ve still got one kilogram in the scale whether it’s lead or feathers; or you’re worng, entirely worng, and both are properties of matter. Different properties, to be sure — but I could trivially extend this analogy to, for example, kinetic energy. A 2,000-pound VW Bug at 55 MPH has (roughly) the same kinetic energy as a 4,000-pound pickup truck at 40 MPH. Since the matter and velocity is different yet the kinetic energy is identical, by your logic, kinetic energy must also be immaterial.

    Cheers,

    b&