Tuesday, April 15, 2003
More on multiverses.
Update: Here's Paul Davies speaking somewhat informally on the anthropic principle:
The evolution of the big-bang theory leads to a discussion of the anthropic principle, which says that the world we see must reflect, to some extent, the fact that we're here to see it — not only here but here at this particular location in space and time. There are different variants of the anthropic cosmological principle, and how much credence you can give it depends on which one you're talking about. What's quite clear is that there must be an anthropic companion to our science. To take a trivial and extreme example: most of the universe is empty space, and yet we find ourselves on the surface of a planet. We're therefore in a very atypical location, but of course it's no surprise that we're in this atypical location, because we couldn't live out there in space.
Obviously, there's an anthropic factor to what we observe and the position in the universe from which we observe it, or maybe the time, the epoch, that we observe it. Having said that, the question is whether it's just a comment about the universe or in some sense an explanation for some features of the universe. If there's only one universe, it's just a comment on it. But if we imagine that there is a whole ensemble of universes — a huge variety, with different conditions, different laws — then it starts to become an explanation, or a selection principle. Part of the reason for the order we observe in the universe is that this is one of the few universes out of the whole ensemble that is cognizable. Some people have tried to carry this principle to a ludicrous extreme by making out that ultimately there are no laws of nature at all, that there is only chaos, that the lawfulness of the universe is merely explained by the fact that we've selected it from this infinite variety of essentially chaotic worlds. That is demonstrably false, and an unreasonable extrapolation of the whole anthropic idea.
It's remarkable that the universe is lawful, that there exist underlying rational principles which govern the way the universe behaves. We can't account for that just on the basis of the fact that we're here to see it, as some people have tried to do. There's a dual principle at work. There's a principle of rationality that says that the world is fashioned in a way that provides it with a rational order, a mathematical order. There's a selective principle — which is an anthropic principle — that says that maybe out of a large variety of different possible worlds this type of world is the one we observe.
We can't avoid some anthropic component in our science, which is interesting, because after three hundred years we finally realize that we do matter. Our vantage point in the universe is relevant to our science. But it's very easy to misconstrue the anthropic principle, and draw ridiculous conclusions from it. You have to be very careful how you state it. What it is not saying is that our existence somehow exercises a theological or causative compulsion for the universe to have certain laws or certain initial conditions. It doesn't work like that. We're not, by our own existence, creating such a universe.
And check out the Counterbalance site, where, if you have more time on your hands than I do, you can listen to Davies talk about purpose in the universe, our place in the universe, or faith and reason. A bit of critical appraisal is here.
Copyright © 2003 by Philocrites | Posted 15 April 2003 at 12:57 PM