Customer Reviews

Just Six Numbers: The Deep Forces That Shape the Universe

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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.

This book is full of repititious metaphors which seem to be designed to impress the reader with the author's knowledge, or perhaps to rouse mindless support for more research in cosmology. Although I agree with the author's sense of awe at the 'fine tuning' of our universe and his admission that it could not be found to be otherwise, I find that this book does very little to explain or explore crucial concepts which would have made this book imensely deeper without neccissarily introducing needless complexity and confusion. All in all, I get the sense that the author writes in the manner of a high school student, who writes the same thing over and over again in only slightly different words because they didn't get it quite right the first time, and in order to achieve a requisite length. A sumary of this book, however, would likely be quite enjoyable as a substitution for the real thing.

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This eleven chapter book (with seven excellent illustrations) by U.K. Astronomer Royal (a title bestowed upon a distinguished astronomer) Sir Martin Rees is about the following:

(1) Cosmology (branch of astronomy concerned with the origin, properties, and evolution of the universe)
(2) Theoretical cosmology (that establishes models which attempt to describe the universe's observed properties)
(3) Speculative cosmology (which is based on hypotheses).

These are large topics that can be incredibly complex and detailed but Rees manages to explain these topics in only 160 pages! As well, the language involved in explaining these topics can be very technical but Rees manages to reduce the technicality resulting in a book that's easy to follow and thus that's "intended for general readers."

I agree that this deceptively concise book is written for the general reader. However, for those not used to this kind of material, I suggest reading this book slowly since Rees cuts out extraneous detail. Whether you are used to this kind of material or not, you'll find that this book offers a stimulating and accessible account of new discoveries, and perceptive insights into cosmology. In fact, this book is so well-written, that according to Rees' internet site, this book is being considered for translation into twenty languages!

Rees, in the last paragraph of this book, summarizes its contents: "A theme of this book has been the intimate links between the microworld and the cosmos...Our everyday world...[shaped] by subatomic forces...owes its existence to our universe's well-tuned expansion rate, the processes of galaxy formation, the forging of carbon and oxygen in ancient stars, and so forth. A few basic physical laws set the 'rules'; our [universe's] emergence from a simple Big Bang was sensitive to six 'cosmic numbers.' Had [any one of] these numbers not been 'well-tuned' [or precise enough], the gradual unfolding of layer upon layer of [the universe's] complexity would have been [suppressed]." That is, "there would have been no stars and no life."

This book has a framework that is centered around the above six cosmic numbers or as Rees states: "[T]his book is the story of six [numbers] that are crucial for our universe, and our [that is, biological life's] place in it." What are these six numbers? Three of them relate to forces in the universe (two of these numbers are basic forces while one of them deals with an "unsuspected new force"); one number is concerned with the basic "texture" of the universe; and two deal with the properties of space itself. As already mentioned, all these numbers have a precise value that allow our universe (and us) to exist. Rees asks: "Is this [precision] just...a coincedence? Or is it providence of a benign Creator?"

Besides learning about these six critical numbers, the reader will learn much more. Some other things you'll learn about are antimatter, atomic structure, atoms, neutrinos, quarks, the periodoc table, the importance of hydrogen, deuterium, and helium, biological evolution, dark matter, black holes, cosmic background radiation, protoplanets and planets, galactic clusters, the strong nuclear force, extraterrestrial intelligence, particle physics, quantum theory, relativity theory, supernovae, and superstring theory. You'll read about such people as Einstein, Arthur Eddington, Michael Faraday, Richard Feynman, Galileo, Newton, Stephen Hawking, Fred Hoyle, and Edwin Hubble.

At the end of the book, Rees asks more questions: "Are there an infinity of other universes [called collectively the 'multiverse'] that are "badly tuned," and therefore sterile? Is our universe an "oasis" in a mutiverse? Should we seek out other reasons for the...values of our six [cosmic] numbers?"

My only minor complaint (and I'm nit-picking here) is that in chapter one Rees states the value of one of these six cosmic numbers. (It is a one followed by 36 zeros.) Instead of expressing this number in scientific notation, he actually writes out all the zeros. I reasoned that by doing this he was attempting to convey a sense of the immensity of this number. However, in chapter three he does the same thing. Why? Writing this long number out once was quite sufficient.

In conclusion, this book offers an accessible account of the forces that shape -- everything. You'll find this book to be an enjoyable and provocative intellectual adventure!

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For the universe to be as the universe is, the author traces this fact to the happenstance of six numbers or ratios, of forces. Examples of this forces are, gravity, nuclear binding force, weak and strong force, density of the universe etc. The author's thinking is something like this, If gravity was stronger the big bang would have spent its outward force already and be contracting. A two-billion year cyclical universe would not have the time to form planets, or for life to form. If gravity was less strong then planets would not have appeared. The author proceeds through each ratio, considering the min and max values. Vary too much from the present ratio and we would not exist, or life, the earth or the universe would not exist. Interesting concept. The surprising thing is the narrow range of some of the values. It shows that we exist from a combination of these numbers within such a narrow range that it borders on the miraculous that we exist at all. Is this. an argument for infinite universes with infinite chances to form or a universe built upon a master plan ?

The Astronomer Royal (the Queen's own?) seems to take seriously Linde's chaotic inflation and the idea that our universe is just one among countless others in a "multiverse." I find it significant that even so great an authority as Steve Weinberg does not dismiss it out of hand.

The notion that our universe is finite and has a beginning in time is of course no longer speculation. But the idea that there are other universes out there with totally different fundamental constants and probably different number (some many more than ours) of dimensions as well is just so hard to fathom. It's mind-boggling to me how anyone can prove or disprove it; yet here it is and it's not a crackpot idea from some harebrained science-fiction writers. Sir Martin is a very eminent astronomer - far more credible than Carl Sagan even.

But if you look back on the astronomical discoveries in the past two millennia, clearly our place in the universe/multiverse has been found to be less and less unique. First we were found to be no longer the only planet, then no longer the planet in the center of the solar system, then no longer the only solar system, then no longer the solar system in the center, then no longer the only galaxy, then no longer the galaxy in the center (because the universe has no center).....and now, perhaps, no longer the only universe. It's all so logical.

Sir Martin seems to think, surprisingly given what he now believes, that intelligent life may be rare in the universe. I for one cannot believe that life, intelligent or not, is rare in our universe, and if there are other universes out there, the odds are considerably higher still. (The Drake Equation suggests there are billions of planets in our universe alone with intelligent lifeforms, and many millions in our galaxy alone.) Perhaps he doesn't want to be taken for a mad scientist encouraging "raelians", ufologists, X-file enthusiasts, "abductees" and other such idiots. The damage it can do to his career is all too real. But all he has to do is to draw a clear distinction between the odds for life, and in particular intelligent life, in other worlds on the one hand, and the odds that any of them have visited us on the other. Again, I think the odds are very high for the former, but almost certainly nil for the latter. In any case, the possibility of our finding these lifeforms is not very high, since considering the distances involved our space technology is still in the Stone Age.

Interestingly, the religious implications are profound if we are indeed living in a multiverse in which our own universe is merely one among countless others, all very different from one another. It may be impossible to prove the origin of such a multiverse, if in fact it even has a beginning. Perhaps the multiverse has always been there, more or less unchanging except at local levels. Or perhaps the multiverse itself has a beginning, and is again only one among countless others. Either way, the role of a Creator cannot be proven - perhaps never can be.

No math is needed to read this book, but it can still be heavy going for the uninitiated, despite its deceptive shortness. Have an astronomy dictionary handy, or else be very patient and careful when following his arguments. Referring back to his earlier book "Before the Beginning" may be a good idea, as is looking things up in an introductory astronomy textbook. If you're still stuck, skip & move on to other interesting topics. Eventually the pieces will fall into place. If not, it may not be your fault, but you're out of luck because Martin John Rees is one of the clearest & most admired educators in astronomy and astrophysics for laypeople.

I was disappointed by this book. I realised that Martin Rees is an experienced distinguished scientist and I hoped that his insight and experience would shine thru in Six Numbers. I feel it doesn't. The book feels like something written quickly to satisfy a publication deadline...written without passion...perhaps dictated in the shower with the details being filled in afterwards. I didn't find the central argument, that the numbers are too fortunate to have come about by chance, convincing.

It has long been debated in science and philosophy as to whether pure mathematics underlies the functioning of our universe. Mr. Rees does not really address this question in his book. What he does, however, is show how our understanding of the universe is based on numbers that have to be very finely tuned indeed for our universe to be the way it is. Just six numbers, in fact.

This is a very intriguing book. Rees gives a good introduction to many of the most fundamental things in science--forces like gravity and electromagnetism, the formation and structure of matter, cosmic expansion and many other things. Moreover, he is not afraid to give these concepts symbol and number and show how these values are determined by theory and observation. Most importantly, he then goes on to discuss how variations in these numbers by even very slight amounts in most cases would lead to a very different universe from the one in which we currently find ourselves. This does much to strengthen many of the arguments he makes concerning those parts of modern scientific theory that is mainly speculation.

If there is a weakness in this book, it is in the author's decision to frame his discussion around symbols and numbers. As a physicist and mathematician, I myself am quite comfortable with it but some readers might be frightened off by these Greek letters and numbers that are often so large or small as to be effectively meaningless. Even more so since these symbols and numbers are so far from what even a high school educated reader might come across in a math or physics class. It might have been more effective to link these ideas up to some concepts a high school educated person might have seen before.

Still, it is part of Rees' purpose, I think, to take us to the cutting edge of physics and cosmology without trudging through every detail. He wants to give us a taste of what are some of the most exciting and thought-provoking things happening today. This is a fair purpose and one that he achieves very well in only 161 pages. It is certainly worth a read.

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.

This book is about some of the numbers that shape our Universe, from the inner-world of atoms, to the whole visible space around us. It does describe the apparent fine-tuning of each of them, describing what the universe would be like if the value was changed. And the results are really suprising: from infinite voids to black holes smaller than an atom, with everything in between.

But this book does more than this: it really uses these numbers as a starting point to explain the latest understanding and theories on astronomy, cosmology, the Universe we exist in, its origin, its fate, and of course, the reason (or lack of) for us being alive in it in the first place.

Very well written and short enough to avoid digressing into personal philosophical opinions, it provides a humbling yet mind-opening introduction to the cosmos. A very good introduction to the vast world of cosmology.

Other reviewers, whose math and physics are much stronger than mine, have been able to review and explain the six numbers discussed in the book. I want to aim my comments to those who at present do not understand these topic but are thinking about reading this wonderful book. If you have the slightest curiosity about the relation between mathmatics and cosmology, please pick up this book and take some time reading it and thinking about its contents. It isn't heavy - it is beautiful. With the six concepts the author teaches us by showing us the numbers you will gain a greater insight into the cosmos than you have ever had (unless you are a professional in cosmology). It will help your reading of any other books on similar subjects and help reveal the true beauty and power of math. This book is on my shelf of treasured books.