Tuesday, August 10, 2010

A case of fine tuning

Nearly a quarter century ago, back when my son was a high school senior or thereabouts, he wandered into our living room and asked what I was reading. I said the book was about the "fine tuning problem:" The fact that if you change almost any of the laws of physics and their parameters - the speed of light, Planck's Constant, the force of gravity, the weight of a proton or neutron, you name it - the universe would be utterly unable to support any form of life. Just how lucky are we?

Don, taking about half a second to recognize a tautology when he heard one, answered, "So?"

"I know," I said, somewhat defensively, "but they did write a whole book about it."

Well, tautology or not, the fine tuning problem remains a bone of contention today. Physicists and cosmologists still are sharply divided about what it really means.

There are four main answers, none of which has attracted a majority following:

1. In the future, a deeper understanding of physics will show that the constants have no choice but to be what they are. (This is a common sort of thing in science - mysteries get explained.)

2. A creator wanted it that way.

3. This isn't a real problem. Of course the constants support life, because here we are! End of story. (For instance, of all the planets in our solar system, only one is known to support life. Guess which one we live on!)

4. We are in a multiverse containing many universes - most sterile because of different laws of nature, but a few fertile. Guess which type universe we live in!

I like Number 4. It turns out that inflation, according to our current understanding, not only could create a universe out of practically nothing, but could be part of a chain of inflations constantly spinning off new universes ... forever. This idea has gained support since it has been shown that both inflation and string theory can indeed generate universes with different physical constants. I like it, however, because it's cool.

Hey, none of this means you don't still need to get out there and smell the flowers.

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