Thursday, 11 January 2007

the anthropic principle

Why are string theorists using the anthropic principle? The anthropic principle begins with the recognition that the universe is shockingly hospitable given our current theories on how it all got started. Complex structures like galaxies, planetary systems, and life itself are famously unlikely to occur--but they have. The anthropic principle is the observation that if the universe had not turned out to have all of those complex structures, there would be no one around to notice. I am a fan of snarkiness, but it is not helpful in this case. The fact that a situation obtains is not an explanation for its obtaining. It of course occurs to me that string theorists are pretty smart, and maybe I've simply misunderstood. I just don't see how.

Is there something privileged about our location in space and time? Yes, but only in a restricted sense. Earlier in the universe, there was no life. Later on, there won't be life either. We're in the privileged middle ground, where things are Goldilocks--just right. But again, that's at best a statement of condition. It doesn't explain anything.

Perhaps the complex structures of the universe should not have been so unexpected after all. I'm not mathematician or cosmologist enough to know the details of the models that have been explored, but my guess is they're highly simplified and linearized--how else could we solve them? If my work in complexity theory has taught me anything, it's that natural systems are rarely simple or linear. There is no contradiction in the universe starting out simple and homogeneous, becoming briefly complex and heterogeneous, and then fading into simplicity and homogeneity again. In fact, in a nonlinear world, it's to be expected.

Then again, maybe I've just made the same error as those who cite the anthropic principle as explanation: I'm expanding an observation about present conditions into a hypothesis about the overall condition of the universe.

1 comment:

island said...

Why are string theorists using the anthropic principle?

String theory produces about 10^500 different possible "meta-stable" vacuum solutions, so physicists have to use a weak interpretation of the anthropic principle to choose our vacuum from the "megaverse", since they've given up trying to identify a stability mechanism that would necessitate the particular configuration that we ended up with.

It's a bunch of crap.

The anthropic principle begins with the recognition that the universe is shockingly hospitable given our current theories on how it all got started.

Which sure as hell should not make anybody think that there is no particularly good physical reason for it, but there are only about two honest people researching the problem from the perspective of a strong interpretation.

You should check out my blog:

http://evolutionarydesign.blogspot.com/