Rating: 
Summary: A simply written little book on a difficult topic
Review: The author, noted astrophysicist Sir Martin Rees, is Astronomer Royal and Royal Society Research Professor at Cambridge University. His life time achievements in areas such as the cosmic microwave background, quasars, black holes and gamma ray bursts was recently recognized by the Peter Gruber Foundation which bestowed it's Cosmology Prize on him last year (2001). His credentials as an author on the subject are thus well founded. Just Six Numbers is a very concise discussion of the defining factors that shape the universe as we know it, and although the underlying physics of the book would probably consume volumes, Rees' little (165 pages) book certainly does a very adequate job of clearly putting the topic across for the lay reader. It adds very little that is truly new, however, except the discussion of the recent concept of Lambda, the so-called cosmic antigravity constant which may control the expansion of the universe. Rees is one of the proponents and designers of the multiverse theory of reality, about which he was recently interviewed by a popular science magazine, but the book dwells very little on this philosophically intriguing subject, dedicating only about 13 pages to it. This would be a good book for young people with an interest in the subject of cosmology to begin their research on the topic of the physics of the universe. It requires adequate reading skills but little actual math. Unfortunately, the bibliography is essentially nonexistant, although the footnotes to the text contain some references that the student might pursue. A simply written little book on a difficult topic by a very competent scientist.
Rating:
Summary: Is this "just the way things are?"
Review: This book is about cosmology, and specifically the manner in which our universe is constructed. The basic premise is that six dimensionless numbers govern the state of our universe so precisely that if any of them changed by even a tiny amount the result would be the impossibility of life, as we know it. The term "number" here is important, as these are all dimensionless ratios and fractions. According to Rees the numbers are:
1)Ratio of electrical force to gravitational force (10^36)
2)Fraction of rest mass converted to energy when hydrogen fuses (0.007)
3)Ratio of actual density to critical density in universe (close to 1.0)
4)Ratio of gravity to antigravity (very small)
5)Ratio of gravitational binding energy of galaxies to their rest-mass energy (10^-5)
6)Number of spatial dimensions in our universe (3) Rees argues that if any of these numbers were slightly different from what they really are, the universe as we know it would not exist. For example, if the ratio of electrical force to gravitational force was larger (by just a "few zeros") the universe would exist for only a short time and there would be no time for the biological evolution that led to animals such as us. Similarly, if the fusion of hydrogen to helium released much more energy than it does, stars would burn out more quickly, again leading to a universe in which animals like us would not have time to evolve. Punctuated throughout the book are references (sometimes abbreviated) to the larger question of why these six numbers, and why the values they have. There's a natural sense of awe and amazement that these numbers all just happened to have precisely the values needed to make life, as we know it, possible. Such amazement leads, naturally enough, to various attempts to explain the apparent coincidence. Perhaps the first question is whether it's a coincidence at all. That is, perhaps the universe was "designed" by a "god" who picked the numbers, knowing before hand exactly what values were needed. Of course this explanation leaves us asking why there is a "god," which seems like as big (or bigger) question than why a half-dozen ratios have the values they do. So this line of reasoning doesn't seem to take us very far. Another approach is to invoke the anthropic principle (I think this is the one Rees prefers). In other words, we see the universe the way it is because if it were any other way we would not exist to wonder about it. Okay, so that doesn't really "explain" anything, either - or, at the very least, it seems just a little too convenient. After all, couldn't we invoke the anthropic principle for just about anything? And if we did, what would happen to our sense of wonder and our desire to learn more - to push back the string of "why?" questions at least one more level? On the other hand, suppose the apparent coincidence is just that; apparent? Suppose these numbers are all somehow related. Suppose that if any one of them is in the right range, all the others will be in the right range, too. That might be the case, but as Rees explains, "At the moment ... we cannot predict any one of them from the values of the others." Although we don't know for sure, it's possible that physics will eventually uncover the "theory of everything" and the ratios will all be in there, in a very nateral and logical way. Or, perhaps the answer is simply "because that's the way things are." Anyone who's been around children (or been a child themselves) knows about the "why?" game. It starts out with something like this: "Daddy (or Mommy), why is the sky blue?" So you explain about Rayleigh scattering and the fact that molecules in the atmosphere scatter photons with an efficiency that's inversely proportional to the fourth power of the wavelength. You are hardly finished when the next question shoots across your bow: Daddy (or Mommy) why is there an atmosphere?" So you dutifully explain planetary evolution, the expulsion of vast quantities of carbon dioxide that facilitated the evolution of life forms that exploit photosynthesis, producing oxygen, etc. Then the third question comes "Daddy (or Mommy) why do planets form?" You follow this question with a short lecture on the planetary nebular hypothesis. But the questions don't stop; they just keep coming and coming and coming. There is, it seems, never an answer that cannot be followed with "why?" If we did have a "theory of everything," and if it did explain these six ratios, there would still be the question "why this theory of everything?" And if we answer that, there undoubtedly will be another "why" question after it. Is there ever an answer that cannot be followed with "why?" That's the real question, for me, in Rees' book. Would the string of questions stop if we could answer why there are just "six numbers," and why they have the values they have? Or, could it be that we might answer that question simply to discover a new "why" question? And if not, how would we know if or when we've arrived at the final answer: "Because that's just the way things are?" This book covers a lot of ground, and does so in abbreviated style in many instances. It's something of a quick cosmic tour. I liked it best for the way it helped me think a little more deeply about the bigger picture. It's a fun book to read, and definitely well worth the time.
Rating:
Summary: Intriguing study of the cosmos
Review: This was a very interesting, and enlightening, book. I didn't know much about cosmology (certainly not the delicate balace that exists) to begin with, but learned a lot by the end. The author, as evidenced by the previous reviewers, analyzes six numbers that give shape, order, etc. to the universe; if there values were slightly changed we could not exist. Rees figures there has to be some reason for things being as they are, so he arives at three possibilities: providence (in the terms of a creator), we're here, so it doesn't matter, or multiverse. He choose a multiverse, but, strangely, gives scant evidence to back up his claim. Most of the book serves to put the reader in awe of the cosmic balance rather than teach about a multiverse. As I've reflected on this during the past month or so, the idea of a multiverse is rather odd. Rees was right when he said it'd be meaningless to think of these other universes existing "before, or alongside" ours. As for what contemporary physicists think of the idea of a multiverse, other than Rees, I don't know. I was reading the latest issue of Discover magazine, though, and in an article about Dark Energy (yet another mind boggling part of the universe), Steven Weinberg invoked the 'anthropic principle:' we're here to question it, so that's it. He admited it was rather embarassing to have no other explanation, but, "right now, nothing else comes close." The point? Experts disagree, and since he didn't (nor did the article) mention anything about a multiverse option, that makes me thing is grasping at straws. The recent demise of Hawking's eternaly contracting and expanding universe (Turner proved the universe is actually going to forever expand), makes it even more mysterious. I too (as does Rees), find Weinberg's explanation unsatisfying, and the multiverse seems implausible (when you ctually think about an infinite number of objects, you'll see what I mean - and a reader would be right to reject Rees' proposition on metaphysical grounds, regardless of how he feels), so what's left? Why not providence? And why does everyone when they here the word "God" immediately assume it's the Hebrew God, Jesus notwithstanding? I don't see any reason why there can't be some mysterious force or being or whatever that shapes and forms the universe so that we can live.
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