Beautiful book on cosmology from a wise astronomer
Martin Rees, who is the Astronomer Royal of Great Britain, returns here to the speculative cosmological mode that he so successfully employed in Before the Beginning: Our Universe and Others (1997) and brings us up to date on his latest thinking. He sets the tone by featuring a quotation from acclaimed science fiction writer Olaf Stapledon's novel Star Maker (1937) to the effect that all that we are and have been is "but a flicker in one day of the lives of the stars." The title Our Cosmic Habitat reinforces the long and distant view that Rees wants to assume, seeing the universe as enormously large and long-lived. The book was composed from the Scribner Lectures that Rees gave at Princeton University.
The ground covered reflects a growing trend in cosmology, that of thinking aloud and in public about matters that have little or no chance of being scientifically tested now or perhaps ever. In particular Rees speculates on the possibility and nature of other universes beyond our own. Indeed, he refers to a "multiverse" with the implication that the universe we experience is just one of a possibly infinite number of other universes, distant from us spatially, temporally and even dimensionally. In other words he seems to be talking about things we can never have any information about!
To the old physicists this must seem a sacrilege, but then Rees himself is no spring chicken! I find it refreshing that a man of his stature and reputation can so freely speculate on matters that are of such complexity and distance, as he notes on page 156, that they "may never be explained or understood." But what I think Rees is getting at, and why he feels justified as a scientist in making these speculative ventures, is that although these other possible universes are completely removed from ours in terms of any possible perception, they may in fact affect our universe in some way that may eventually be measured or otherwise discerned. For example (this is my speculation) suppose we finally did get an indisputable, proven theory of everything, somehow wedding gravity and quantum mechanics, and found that our universe was in some way--again indisputably--different from what that theory predicted. Such a difference would have to come from something outside, perhaps as the signature of an effect from another universe.
As one would expect from a senior scientist, Rees gives us some political guidance in scientific matters. On page 31 he expresses his view that a justification for going into space is to free the human race from the possibility of extinction from a "catastrophe that we bring on ourselves," through "experimental misadventure or a terrorist act that deploys techniques from bioscience." Incidentally Rees estimates that the chance in a lifetime of anyone alive today of encountering an Earth-crossing asteroid at less than 1 in 10,000, which he describes as "no lower than the risk...of being killed in an air crash." Consequently, he finds it "fully worthwhile to devote modest efforts to survey the sky for potentially dangerous...asteroids." (pp. 30-31)
Rees's treatment of string theory, now called M-theory, with its ten or eleven dimensions, is cautious. In chapter ten after remarking on the non-surprising cancellation of the Superconducting Super-Collider project, he obliquely advises young physicists to think twice before devoting their lives to string theory. He writes, "...an undue focus of talent in one highly theoretical area is likely to be frustrating for all but a few exceptionally talented (or lucky) individuals." He reminds us of Peter Medawar's "wise remark that ‘no scientist is admired for failing to solve a problem beyond his competence’." (pp. 155-156)
As in his book mentioned above, Rees confronts what he calls the "puzzlingly biophilic" (p. 45) nature of our universe and again addresses the anthropic principle. See especially Chapter 11 where he uses a metaphor from philosopher John Leslie to account for our justified surprise or lack thereof at living in our "interesting" universe rather than one with laws that "had boring consequences." Leslie has us before a firing squad with fifty marksmen who all miss. Rees writes, "If they had not all missed, you would not have survived to ponder the matter." As it is, "you would seek some further reason for your luck." The analogy here is with our luck in having a universe with "interesting consequences" that "allowed us to exist." (pp. 162-163) But I think the comparison breaks down because we had in the case of the firing squad a fine expectation of being hit, whereas no such expectation of a "boring" universe is necessarily justified. The anthropic principle is in full force here, it seems to me: we only exist in "interesting" universes.
Bottom line: this is a compelling book, written by a man who can speculate but speculate reasonably so that we are intrigued and interested rather than set awash in a sea of fanciful maybes. Rees writes with charm and a most reserved sense of humor. (Example: on page 151 he speculates on whether a universe could have more than one time dimension, wryly observing that to describe such a universe we would need "a language with more tenses.") He always qualifies his statements to the nth degree and, reflecting the wisdom of his years and experience, is never out on a limb by saying that anything possible is "impossible," as senior scientists have carelessly done in the past.
By the way, this is a beautifully designed book, with a splendid jacket designed by Tracy Baldwin. The black and white artwork illustrating the text by Richard Sword is something close to exquisite.
--Dennis Littrell, author of “The World Is Not as We Think It Is”