Philosophy, Film, Politics, Etc.

Tuesday, March 26, 2013

A Universe From Nothing?

There are various issues that I'd like to address regarding the 2013 Isaac Asimov Memorial Debate, but one in particular is bugging me.  Lawrence Krauss says that science can give us a plausible explanation of how a universe like ours could spontaneously "pop into existence" out of timeless, spaceless, lawless void.  Jim Holt says that Krauss is talking nonsense:  The idea of a universe "popping into existence" implies that there is a point in time in which that event occurs.  Yet, by Krauss' definition, there is no time (or space) for the universe to pop into.  I think Holt's point is valid, but it does not get resolved.

Here's the whole exchange (starting @ 0:50:00):

Krauss: Quantum mechanics says things fluctuate, and if gravity is a theory of space and time, if you make space and time quantum mechanical variables, then it is perfectly possible for universes to pop into existence--space and time to pop into existence where there was no space and time before.

Krauss wants to continue, but Holt interrupts.

Holt: Space and time pop into existence?  You make that sound like a temporal process, a process in time.

Krauss: Well, because I said it so you can understand it.

Holt: Huh?

Krauss: No, I mean I used words, and the problem with words are [sic], as T. S. Eliot says, they're sort of slippery.

Holt: But becoming implies time.  You can't have time coming into existence as itself a temporal process. That makes no sense. That's why it's good to have philosophers around, which I'm not one, to help you use language precisely.

Krauss: Okay, so let me just pretend there--let me just say there's a global time and at some time a space pops into existence. Okay, will that make you happier?

This does not satisfy Holt, however, and I can understand why.  Krauss started by claiming to have an explanation of how time itself can come into existence out of a timeless void.  Now, however, he's saying that there is a global time out of which the universe sprung.  So he's changed his story.  Something fishy seems to be going on.  But before Krauss and Holt can make headway, Neil deGrasse Tyson steps in to moderate.

Tyson: Lawrence, you are saying that because we have quantum phy--because we are illuminated by the actions of quantum physics, mentally, we can think about whatever is our best understanding of nothing, and quantum physics then pops into existence in that nothing an entire universe, and if that's the case, I would then pick up Jim's point and ask you--

Krauss: I was gonna try and ex--Where do the quantum physics come from?

Tyson: No, no, no.  No, no, no.  That's not what I'm gonna ask you.  I'm gonna ask you--that had to happen at some point.  Why isn't it happening all the time and everywhere at all times?

Krauss went on to answer that question.  Unfortunately, that is not the question that Holt was raising, and Holt never tried to raise the point again.  Holt's question was, what sense is there in talking about space and time coming into existence?

Krauss' claim is that the universe may have originated out of a timeless, spaceless void.  His theory (from what I gather) is that such a void would be inherently unstable, and so would tend to produce stuff.  The question then is, what sense is there in referring to a timeless, spaceless, lawless "nothing" as being unstable?  Stability and instability are properties which persist in objects over time.  If there is no space or time, then there is no instability.  Furthermore, what sense is there in claiming that the creation of the universe occured in a spaceless, timeless nothing?  If there is no space or time, then there is no such thing as occurence.   It defies logic to speak the way Krauss is speaking.

Now, maybe Krauss has a point about the limitations of ordinary language.  There's a long tradition, from Galileo to Heisenberg, of regarding math and math alone as suitable for grasping the truth of physics and, by extension, reality.  Once you start using non-mathematical terms, you lose the sense, beauty and truth of the model.  But if that is so, and mathematics is the only coherent way to talk about reality, then what does that say about reality?  Is all non-mathematical language incoherent?  Should we be Platonists, and accept that the only truth is purely mathematical?  Is everything else just illusion?  This is philosophy, not physics, but it's what Krauss might be suggesting.

Even if we avoid Platonism, isn't Krauss suggesting that physics is beyond comprehension?  Does that mean physicists should just shut up and calculate?  If so, then Krauss really shouldn't be trying to talk about these things at all, should he?  He says he's trying to describe the physics in a way so that we can understand it, but apparently that is impossible.  And that raises the question: How well do Krauss and other physicists understand it?

I don't think physicists should just shut up and calculate.  However, I do think they sometimes need to be more careful in the way they present their ideas.  And they should also be more open to philosophical scrutiny in that area, since philosophers have experience and conceptual tools for exploring the logical space of our discourse.  (Krauss denies that philosophers have any expertise to bring to the table at all, which is unfortunate.)

Krauss' argument seems to be this:  Our universe may ultimately have sprung out of a timeless, spaceless, lawless void.  This could be so because, in such a void, every possible law obtains (which, for Krauss, is the same as saying that no laws obtain.)  The laws of quantum mechanics are possible, and so those laws also obtain in The Nothing.  And according to those laws, universes can pop into existence.  One problem with this view is that there must be something to exist in which those laws can obtain.  If there is really is nothing at all, then there is nothing on which the laws can act.  So the explanation doesn't work.

Let's say Krauss finds some way around that problem.  There is still another problem:  Couldn't there be some laws which are not consistent with quantum mechanics, and which, in fact, say that universes cannot pop into existence?  If all laws obtain in The Nothing, then we could have one law which says universes can pop into existence and another law which says they cannot.  In that case, a universe popping into existence would be physically impossible--it would break one of the laws of nature.  Krauss needs to explain why such a law--a law against universes popping into existence--is impossible.  If it's not impossible, then his account does not work.

Krauss also suggests a slightly different argument which starts with an assumption: Everything which is possible is actual.  In that case, every possible arrangement of quantum variables is real.  That means that every possible universe exists and also that the "ground state of a gapped quantum system" (as Eve Silverstein calls it) is also real.  So The Nothing is as real as our universe.  And so there is a temptation to say that our universe--all universes--came out of The Nothing.  However, this doesn't overcome Holt's objection.  We still can't say that all of the other states of the quantum system came from the ground state, because the ground state does not exist in any particular place or time.  It's not clear in what sense the ground state can exist at all.  Maybe we can still say that the ground state, like all the other states, is real, since reality does not necessarily imply existence (for example, it is not hard to admit that numbers are real, but it's very hard to say in what sense they might exist), but we're still left with the question:  How did the quantum system come into existence in the first place?

If you want to talk about what caused the universe, then you're asking for a first cause.  Krauss seems to want it both ways here.  He says science doesn't need a first cause.  That's true.  Philosophy doesn't, either.  But then Krauss hasn't explained how the universe (or multiverse) might have come into existence.  If he wants to explain that, then he really does seem to be looking for a first cause.

What many physicists seem to prefer--and I think J. Richard Gott is one of them--is to say that the universe (or multiverse) just is.  Nothing caused it to occur.   Krauss might even agree, in which case all his arguments about universes popping into existence seem like a waste of time.  Whatever Krauss thinks, it is philosophically respectable to say that the very question, What caused the universe to exist?, is meaningless, because "the universe" is not the sort of thing that can be caused to exist.  The universe, the multiverse--the quantum system--just is.  It didn't come from nothing.  It didn't come, period.

I'll end with a note on the meaning of the term "universe" as physicists today understand it.  According to Gott and Krauss, the word "universe" has a different meaning nowadays.  Krauss says "universe" is defined as "everything you could have once interacted with, or you can ever interact with.  So everything you can have physical contact with, either in the past or in the future, is a universe."  Different universes can share a causal history, but they don't have to.  They might be completely and utterly independent of each other.  Now, if we're talking about multiple universes which share a common history--a common trunk, as Gott puts it--then aren't there going to be moments in my universe which can have physical contact with moments that aren't in my universe?  In other words, the differentiation of universes is relative and not absolute.  While "my" universe has some unique physical properties, not everybody in "my" universe will draw the boundaries of their universe the same way I draw the boundaries of mine.  This isn't necessarily a problem, but I find it curious.

P.S. If you want to know what philosophers have to say about nothing, the SEP entry on Nothingness is a good place to start.