Review of "Just Six Numbers"

Just Six Numbers: the deep forces that shape the universe, by Martin Rees. ISBN 0-75381-022-0.

The laws of nature seem to have too many arbitrary constants in them; numbers for whose values we can see no explanation; numbers that, for all we can tell, were chosen at random by whatever gods there may be. One interesting thing about these numbers (which has led some people to think that those gods shouldn't be taken too metaphorically) is that it seems that some of them couldn't be very different from what they are without making life as we know it impossible. In other words, we seem to have been very lucky that there was a universe fit for us to live in.

In this book, Martin Rees discusses six of them:

I find myself unconvinced by several of these (but, note, I am not a cosmologist or even a physicist, so maybe I'm missing important things); the obvious hole in claims of fine tuning is that there may be a big difference between life as we know it and life simpliciter.

Anyway, the discussion of these six numbers gives Rees a chance to digress on black holes, antimatter, nucleosynthesis, inflation, dark matter, and all the other usual suspects of popular cosmology. He does so very competently.

Finally, Rees addresses the question of how come these constants are (allegedly) so finely tuned. He doesn't think much of the prospects for a theory that makes their values inevitable; he prefers, like most people at present, a "multiverse" theory (in which there are many "universes" with different values for the constants) plus the anthropic principle. (I was surprised to see no mention of Smolin's evolutionary variation on this theme.) He dismisses the possibility that the tuning is a one-off coincidence, and passes over the theistic (or deistic) explanation almost without comment.

Rees does a good workmanlike job of explaining this material for a lay audience.