| OUR COSMIC HABITAT Martin Rees Princeton: Princeton University Press, 2001 |
Rating: 5.0 High |
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| ISBN-13 978-0-691-08926-3 | ||||
| ISBN 0-691-08926-4 | 205pp. | HC/GSI | $22.50 | |
Physicist Martin Rees is currently the principal explainer of the "Multiverse" concept — the idea that our universe is not all there is; that it may be merely one of a multitude of generally similar structures.
This mind-blowing idea is on the far frontier of cosmology. At first glance, it seems logical that it should lie beyond that frontier; that it must be in the realm of metaphysics or philosophy rather than science. But Rees argues that there are observable phenomena that bear on the question. As an example, he gives lambda, the value for the repulsive force that caused the inflationary phase of the Big Bang and that was recently hypothesized to be operating even today. Our universe puts rather narrow limits on this value. If it were too low, everything would long since have collapsed back into the "monobloc" from which it emerged in the Big Bang; if too high, galaxies and stars would never have a chance to form.
If lambda was found to be unrelated to the expansion, Rees says in chapter 11, and if it had a value thousands of times less than the minimum, that would be evidence that ours was the only universe. At the bottom of page 175 he asserts, "Lambda in our universe obviously had to be below that threshold [that disrupts galaxies]. But if our universe were drawn from an ensemble in which lambda was equally likely to take any value, we would not expect it to be too far below it." (Emphasis in original) Statistically, this makes no sense; if all values are equally likely, a random sample of one might have any value within the possible range. However, if the values follow the normal distribution ("bell curve") — which future theories might confirm — Rees' assertion would have merit.
On another point, he is on firmer ground. Lee Smolin theorizes that new universes form within black holes. If he's right, when our understanding of these enigmatic structures improves, we might indeed find ways to test the multiverse concept scientifically.
Don't think that this text is either very technical or very esoteric. Drawn from the Scribner lectures, which Rees gave at Princeton, it is intended for a general audience. It covers all of cosmology in a very readable way. The text is well supplemented by Richard Sword's illustrations, and enhanced by quotations from Olaf Stapledon's Starmaker. I'll recommend it, with the proviso that one of Rees' other books might serve a technical audience better.
One other mistake exists. In the footnote on page 47 is this statement: "Despite its initial handicap, amounting to 36 powers of ten, gravitational forces become dominant when more than about 1054 protons are packed together (36 being two-thirds of 54)." The meaning of this two-thirds ratio is not explained. It could be an application of the square-cube law1, but that's just a guess. I also question the use of the term "anthropic principle" (as on page 178). But that is not Rees' error; the term is inherited from a book by Barrow and Tipler.
I also found two grammatical errors and a typo.
| Page 47: | "Despite its initial handicap, amounting to 36 powers of ten, gravitational forces become dominant when more than about 1054 protons are packed together (36 being two-thirds of 54)." |
| Error of number; S/B either "its ... gravity becomes" or "their ... gravitational forces become |
| Page 81: | "...and the temperature difference between hot and cold patches on the sky are 10,000 times smaller still." |
| Error of number; S/B "differences". |
| Page 171: | "Einstein's theory of gravity, or general relativity — dates from 1916." |
| Improper punctuation; S/B "Einstein's theory of gravity — or general relativity — dates from 1916." |
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