Tuesday, October 16, 2007

Something for nothing and your universe for free

One argument I keep running into that is supposedly evidence for God (sometimes a generic god, sometimes a specific one) is that the universe began, therefore it must have been created. Sometimes it's more elaborate than this, sometimes not. In the cases where it's just this simple, it's effectively a God of the gaps argument. Since that type of argument has been dismantled repeatedly, I'm going to focus on the more elaborate versions today.

The most common elaboration to this argument is that the creation of the universe violates conservation of energy. "It's a well-known fact of science that you can't get something from nothing," they say. Interestingly, it seems that the people who say this sort of thing rarely have any real background in physics, much less a background in theoretical physics or cosmology. Before making big assumptions like this, wouldn't it make sense to check with someone who knows what they're talking about in this area to see if they could explain it?

Now, if only we had a cosmologist on hand... Wait a second, I'm a cosmologist! Well, I guess I'd better try to make some sense of these problems then. So, to the claims that the creation of the universe violates conservation of energy, my response can be summed up in two simple retorts: "Says who?" and "Even if so, so what?" Allow me to elaborate.

The first catch is that we don't know for sure that the creation of the universe actually does violate conservation of energy. First, let's keep to known science, and use an example taking place within our own universe. Let's say that somehow, a massive particle was created. Since mass = energy, this took up energy to create it. Now, what could have happened to allow this creation? A few possibilities:

1. Some physical process took place which resulted in an excess of energy. This extra energy was converted into this particle.
2. Even a vacuum doesn't have zero energy. It's possible that this particle borrowed energy from the vacuum in order to form (possibly along with its antiparticle if it has other properties such as charge which need to be conserved).
3. This particle was created alongside a mirro version of itself which has negative mass, resulting in a net change of zero energy. Note that we've never observed negative mass particles, but our current laws of physics don't bar them from existing.

So, let's expand to the creation of our universe. It turns out that for each of these, there's a nice parallel for the creation of the universe as well:

1. Some physical process took place outside our universe which resulted in an excess of energy. This extra energy was converted into our universe.
2. Whatever medium exists outside our universe might not necessarily have zero energy. It's possible that the creation of our universe simply borrowed some energy from this medium. A parallel anti-universe might also exist to balance quantities which must be conserved.
3. Our universe was created alongside a negative energy version of itself, so the net change in energy is zero.

There's also one more explanation which works for our universe, but not for the particle example:

4. Our universe has a net energy of zero. It is possible that the mysterious phenomenon we've termed "Dark energy" actually has negative energy, and this balances out the positive energy all of the mass in the universe provides. A little catch is that there's likely much more dark energy in the universe than all the other mass, so we'd actually be at an excess if this were true. That's little problem though, as it could easily have just been radiated away or whatever outside our universe.

So there you have it, four possible reasons why the creation of our universe might not violate conservation of energy. But even going into all that isn't really necessary. The catch is, violating conservation of energy isn't necessarily a problem when it comes to the creation of the universe. The reason for this is a bit complicated, but a simple version is as follows: Conservation of energy is an observation we've made which always seems to hold within our universe. We have no evidence that it holds outside our universe, or even that any of our laws of physics are the same out there. Therefore, we don't have reason to believe it must hold at the point of creation.

Now, for the more complicated explanation. We actually do have one explanation for why energy (and other properties, for that matter) is conserved. The reasoning is complicated, so I won't go into it here, but the key point is that it relies on what are known as symmetries. In the physics world, a symmetry is more than simply being able to mirror something and have it be the same. What it means here is that we could move the whole frame of reference in some way, and all the physics would remain the same.

There are three big symmetries of this type you'll know of. There's translational symmetry, which means if you move a foot to the right for instance, physics stays the same. There's rotation symmetry, which means whichever way you turn, the physics is the same. And there's temporal symmetry, which means that physics stays the same over time. There are also some others you probably haven't heard of it you haven't take college physics, such as gauge symmetry, but you don't need to worry about those here.

The important point about this is that there's a law of physics which states that for every symmetry, there must be some conserved quantity. This is completely unintuitive, but it's provable. Not easily provable, and most people reading this probably wouldn't understand the proof in any case, but it is provable, so just trust me on this. When we apply this law, we get the following conservations from the following symmetries:

-Translational symmetry gives us conservation of momentum.
-Rotational symmetry gives us conservation of angular momentum.
-Temporal symmetry gives us conservation of energy.
-Gauge symmetry gives us conservation of charge.

The important one for our purposes is the third: Temporal symmetry gives us conservation of energy. What happens if we no longer have temporal symmetry? Well, we can no longer guarantee conservation of energy. Now, think back to the beginning of the universe. At this point, all of the universe is compressed to a single, zero-dimensional point. Are the laws of physics the same here? Not at all. Temporal symmetry must be broken at this point, so we have no reason to believe that conservation of energy must apply. The instant after it, we start to have temporal symmetry, so whatever energy we start with we're stuck with, but there's no way to say what this might be.

So there you have it: a cosmologist's perspective on conservation of energy at the beginning of the universe. We don't know that the beginning of the universe violates conservation of energy at all. Even if it does, this isn't necessarily a problem. Even if all this is a problem, it's still at best a God of the gaps argument, and that's really no reason to believe at all.


Techskeptic said...

Good post. I'm sure there are even more propositions about how to reconcile this. The only thing I dont like about them, and the multiverse theory, is that as far as I can see, there really isnt a good way to test any of it. Just like you can't test for god. so is it really any better?

I for one would be interested to at least see the proof you were talking about. Is there a link somewhere?

the universe began, therefore it must have been created.

I like to just correct them

The Universe began and therefore there must have been a cause.

so thats a pretty quick retort to that silliness. Now I have one for you. Its also something I have been reading a lot recently

"Well I, too, value critical thinking and use evidence that i see around me, and I have come to the conclusion that God does exist"

If I try to let in about the way they are valuing evidence, or even what constitutes evidence, I will come off cocky and arrogant (i.e. my evidence or lack of evidence is better than your evidence).

Any thoughts on how to explain evidence to someone who already thinks they have evidence?

Infophile said...

Yeah, I was originally planning to link to the proof, but the internet from campus was being buggy and I couldn't find a good one online. Anyway, Wikipedia has about the best explanation you'll come across online: Noether's theorem.

Actually, I'm not sure if I'd even agree that something which has been created must have a cause. The problem is that once you have a cause, you just regress back a step. You'll either have to eventually regress to something that extends infinitely backwards in causality, get an infinite series of regression, or find something finite with no cause. Blah, it gets all complicated from here, but the point is that if you demand a cause for everything, it eventually leads into multi-temporal-dimensional insanity.

As for your particular problem, unfortunately I don't think there is any good way to handle it which doesn't involve going into how one evaluates evidence. The best thing I could recommend is to ask them to explain something to you. When they get to a part you don't agree with, then ask questions to see if they can come to a realization about it on their own (or point out fallacies/perceptional flaws).