A Universe from Nothing?

• A Universe from Nothing?

  • One question is, within some framework of physical laws that is flexible enough to allow for the possible existence of either “stuff” or “no stuff” (where “stuff” might include space and time itself), why does the actual manifestation of reality seem to feature all this stuff?
  • The other is, why do we have this particular framework of physical law, or even something called “physical law” at all?
  • Ever since Newton, the paradigm for fundamental physics has been the same, and includes three pieces. First, there is the “space of states”: basically, a list of all the possible configurations the universe could conceivably be in. Second, there is some particular state representing the universe at some time, typically taken to be the present. Third, there is some rule for saying how the universe evolves with time.
  • Quantum mechanics, in particular, is a specific yet very versatile implementation of this scheme. (And quantum field theory is just a particular example of quantum mechanics, not an entirely new way of thinking.) The states are “wave functions,” and the collection of every possible wave function for some given system is “Hilbert space.”
  • And then there is a little machine — “the Hamiltonian” — that tells you how to evolve from one state to another as time passes.
  • Within this framework, specifying “the laws of physics” is just a matter of picking a Hilbert space (which is just a matter of specifying how big it is) and picking a Hamiltonian.
  • The first possibility is that the quantum state of the universe really does evolve in time — i.e. that the Hamiltonian is not zero, it truly does push the state forward in time.
  • as the quantum state of the universe evolves, it can pass through phases where it looks an awful lot like “nothing,” conventionally understood — i.e. it could look like completely empty space, or like some peculiar non-geometric phase where we wouldn’t recognize it as “space” at all. And later, through the relentless influence of the Hamiltonian, it could evolve into something that looks very much like “something,” even very much like the universe we see around us today. So if your definition of “nothing” is “emptiness” or “lack of space itself,” the laws of quantum mechanics provide a nice way to understand how that nothing can evolve into the marvelous something we find ourselves inside.
  • The other possibility is that the universe doesn’t evolve at all — the Hamiltonian is zero, and there is some space of possible states, but we just sit there, without a fundamental “passage of time.”
  • We certainly think that we perceive time passing, but maybe time is just emergent rather than fundamental.
  • That is, perhaps there is an alternative description of that single, unmoving point in Hilbert space — a description that looks approximately like “a universe evolving through time,” at least for some period of duration.
  • In this case, unlike the previous one, time could end (or begin), because time was only a useful approximation to begin with, valid in a certain regime.
  • In this kind of picture, there is literally a moment in the history of the universe prior to which there weren’t any other moments. There is a boundary of time (presumably at the Big Bang), prior to which there was … nothing. No stuff, not even a quantum wave function; there was no prior thing, because there is no sensible notion of “prior.”
  • a bit of contemplation should reveal that this kind of reasoning might, if we grant you a certain definition of “nothing,” explain how the universe could arise from nothing. But it doesn’t, and doesn’t even really try to, explain why there is something rather than nothing — why this particular evolution of the wave function, or why even the apparatus of “wave functions” and “Hamiltonians” is the right way to think about the universe at all.
  • Do advances in modern physics and cosmology help us address these underlying questions, of why there is something called the universe at all, and why there are things called “the laws of physics,” and why those laws seem to take the form of quantum mechanics, and why some particular wave function and Hamiltonian? In a word: no.
  • But the universe, and the laws of physics, aren’t embedded in some bigger context. They are the biggest context that there is, as far as we know. It’s okay to admit that a chain of explanations might end somewhere, and that somewhere might be with the universe and the laws it obeys, and the only further explanation might be “that’s just the way it is.”
  • As long as you admit that there is more than one conceivable way for the universe to be (and I don’t see how one could not), there will always be some end of the line for explanations. I could be wrong about that, but an insistence that “the universe must explain itself” or some such thing seems like a completely unsupportable a priori assumption
  • If your real goal is to refute claims that a Creator is a necessary (or even useful) part of a complete cosmological scheme, then the above points about “creation from nothing” are really quite on point. And that point is that the physical universe can perfectly well be self-contained; it doesn’t need anything or anyone from outside to get it started, even if it had a “beginning.”

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