Tuesday, November 29, 2011

The multiverse -- Part 2

(This continues a discussion from last Friday.)

Philosophers, theologians, and even some scientists have made much of the fact that the universe has exactly the properties that make possible life and intelligence as we know it. For example, if the nuclear force were slightly stronger all the hydrogen nuclei in the early universe would have fused into helium and there would be no water to nurture life. If the force were slightly weaker, then heavier atoms like oxygen and carbon would not hold together. Other examples of apparent fine-tuning abound. This gives rise to the "anthropic principle": the universe must have exactly the properties it has because we are here to observe it.

Or, as theologians are wont to say, the universe is apparently designed just for us.

Or as I would say, we are here because the universe we live in allows our existence. The fuss about the anthropic principle always seemed to me to be a tempest in a teapot.

In any case, as Alan Lightman points out in his Harper's essay, the multiverse idea -- if it's true -- renders the intelligent-design implications of the anthropic principle moot. We're here because among the supposed gazillions of universe that exist, one of them just happens to have the parameters that allow our existence. We are a cosmic accident.

All of this makes great cocktail party fodder, but it leaves me cold. Drawing grand philosophical or theological conclusions from whatever is the hottest current cosmology seems to me a fool's game. I like my speculations to have an empirical handle. The big bang? OK. We have lots of evidence for that. What came before the big bang? Your guess is as good as mine. The multiverse? Give me a call when you have some observational data.

I don't think physics is having a crisis of faith, as Lightman's subtitle suggests. Physicists will go on doing what they have always done, refining the physical laws of the universe in light of empirical observations. In the course of that search, they will come up with highly speculative ideas, like string theory and multiverses, but such ideas rise and fall on the basis of observation.

One can't have a crisis of faith unless one has a faith to begin with. Faced with choice between an intelligent designer and 10-to-the-500th-power accidental universes, I'll stick with a healthy agnosticism. For the time being.