Monday, July 23, 2012

Why I'm agnostic on cosmology

In my previous post, I said that there were many solutions to the entropy problem, but I did not want to pick one.  I think I should better explain my motivations for this.  Why am I so agnostic about cosmology?

Part of it is that I really just don't know.  I'm a grad student in condensed matter.  I know a little about quantum field theory, general relativity, and cosmology.  But like the saying goes, the more you know, the more you know you don't know.  I know that there is a lot of cosmology I don't understand.  I know that cosmology is a complicated field that you can't truly understand just by reading Brian Greene.

I tend to think that if I don't have an opinion on cutting-edge questions of physics, nor should lay people.  I mean, if I don't know enough to speak, and lay people know less than I do, then clearly lay people shouldn't be speaking either.  Just because they read some Brian Greene doesn't mean they understand anything!  That's how physics cranks are born, you know.  They read some popular physics and think they understand.

But I am being unfair to lay people.  They can enthuse about physics all they want.  Physics is cool!

Of course, when lay people speak about physics, they don't get taken seriously.  When I speak about physics, I get taken more seriously.  If I were to even speculate on whether inflationary theory is correct, then I would appear to be giving my expert opinion.  But I don't have the necessary expertise, and I want to make that clear.  My expertise allows me to speak on certain things: the foundational theories of physics, the consensus of physicists, understanding what other physicists say.  But I do not have the expertise to go beyond the consensus.  For the most part, I cannot even go beyond the consensus in my own field, much less cosmology.

But there's another side to this too.  I don't like the idea of atheists being ideologically committed to one particular cosmological scenario.  The situation bears too much resemblance to Creationists, who are committed to a relatively young universe.  It bears too much resemblance to liberal Christians like William Lane Craig, who hold that the universe must have had a beginning.  Of course, mere resemblance to something bad does not mean it is bad.  But it makes me uncomfortable to see atheists advancing one particular cosmological theory in a philosophical argument.  What if that theory is wrong, huh?

Here's a specific example.  I most often see atheists advancing one particular solution to the entropy problem.  The solution is that when the universe was very small, its maximum entropy was also very small, and that's why we start with a highly ordered state.  As the universe expanded, the ceiling on the entropy rose, allowing the entropy to increase as described by the Second Law.  The purpose is to demonstrate that yes, there are possible explanations for the Second Law besides God.

Though I agree that there are many alternative explanations besides God, I am not convinced that this particular explanation is necessarily true or complete.  If a small universe has less maximum entropy, that seems to imply that if the universe undergoes a big crunch, then the entropy will decrease.  Does that mean the arrow of time will be reversed?  People have seriously proposed this, but Wikipedia calls it "a highly controversial view".  There's also the question of why the universe ever compact to begin with.  If a small universe has low entropy, this means that the there are very few possible ways for the universe to be small.  So why was the universe small and compact, out of all the ways it could have been? Some people would argue that at the universe has to be small and compact at its beginning (due to General Relativity), but this basically concedes that the Second Law implies that the universe has a finite age.   I don't think we should concede that.

Keep in mind that I am not an expert, and I could be completely wrong about these objections.  I don't wish to appear an expert where I'm not (see above).  However, I believe that experts in the relevant fields have raised similar objections.

And that is why I take an agnostic approach to cosmology in the cosmological argument.  I don't know enough about it, though I appear to be an expert.  I don't want us to be ideologically committed to a theory which may or may not be correct.  I don't believe this hinders our refutation of the cosmological argument.


Anonymous said...

Nice post and I see wisdom in your stance on it. But there is one thing I don't understand:

How is a theist who believes in an omnipotent being allowed to argue from thermodynamical principle, which is chaos and chance, to support his believe?

It is a direct contradiction of terms and I laugh at the intellectual attempt. I am not oblivious to the fact that there could be a difference between the notion of an omnipotent being and a creator. But lets be fair, creating a universe seems more miraculous than being omnipotent in one, and once the primal teleological case has been made the theist has little worry about the steps to complete vindication through either determinism or mysticism. But Oh divine and cosmic irony! The last steps he denies himself if he bases the teleology on thermodynamics. Moreover, both cosmology and the timelessness of God compel us to assume that the whole of time should be embedded in the creation of the universe, thus making omnipotence in a universe a virtual consequence of being its creator. And mathematics tells us it is not more work to create the whole of spacetime instead of just a timeslice anyway. But thus it means that the thermodynamical hypothesis of chance only holds if the universe is not created. So, let me rephrase my question:

How is a theist allowed to argue from chaos and chance that the world is not chaos and chance?

For what else is faith. And with allowed I mean taken seriously and not simply laughed away.

miller said...

The second law does not say that the world is purely chaos and chance (ie the universe is not in the state of maximum entropy). Rather, it says that the universe has some order, and this order decreases over time. Although perhaps you can argue that a god is more consistent with a universe that is ordered, and remains ordered over time.

Anonymous said...

Sure. But saying that all microstates are all evenly probable and that they change totally randomly each moment counts as "the world is chaos and chance" to me. Even if this representation of the basis of the second law is weakened, e.g. the magnitude of the change is limited or there exists a probability function for microstates, thermodynamics is based on chance and uncertainty. It is a statistical model that can't be used/does not apply* when everything is known and definite, which it is for an omnipotent, omniscient creator. And therefore it can't be used to proof that one exists either.

*It can be used, but it will give less information than you already have and is not assured to make correct predictions. You can't apply thermodynamics backwards in time and not be mightily 'surprised' for example.