Book Review: Just Six Numbers by Martin Rees

Posted On Nov 09, 2008 at 3:54 pm
Just Six Numbers by Martin Rees
Just Six Numbers
Martin Rees
Nonfiction - Cosmology
8 out of 10
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In Just Six Numbers, Martin J. Rees, Astronomer and Royal Society Research Professor at Cambridge University, explains six of the most important numbers that shape our universe. These six numbers are seemingly "tuned" to specific ranges that have allowed our universe to evolve to where we are at now.

  • Ratio between Strong Force and gravity. N = 1038: This number really is about the importance of two numbers: gravity and strong force, also called strong interaction. Strong force is the most powerful of four fundamental forces which holds sub-atomic particles together to form protons and neutrons. This force is 100 times the strength of the electromagnetic force, 1013 times as great as that of the weak force, and finally about 1038 times that of gravity, which is where the ratio of N comes from. Interestingly, this book claims that strong force is 1036, whereas modern resources online indicate 1038. The book also seems to lump strong force and nuclear force together as the same thing which I found rather confusing. During the chapter on nuclear efficiency, Rees refers to what is technically nuclear force as strong interaction. Strong interaction is actually strong force; so Rees inadvertently inferred that the strong and nuclear forces are the same thing. Maybe in 1999 they were thought of as the same or maybe he just made a mistake? Or perhaps I am just mistaken and they are technically the same force, but just described with different terms to differentiate its effects between subatomic particles and protons/neutrons. Unfortunately I cannot find any online resources that answer this for me.
  • Nuclear Efficiency. ε = 0.7% (.007): The nuclear efficiency is more of a result from the "tuning" of the nuclear force that binds protons and neutrons together, however Rees has chosen to explain the subsequent efficiency and its importance of allowing a wide range of elements to form while not consuming all the hydrogen; this allows stars to burn for billions of years. If ε was too weak, Hydrogen would not be able to form any other elements. If ε was too strong, all hydrogen would have been converted to higher elements during the big bang, resulting in there being no fuel for stars and no water - thus no possibility of life as we know it.
  • Density parameter (Omega Ω): Ω measures the amount of material in our universe - galaxies, diffuse gas, and dark matter. Ω tells us the relative importance of gravity and expansion energy in the universe. If this ratio were too high relative to a particular critical value, the universe would have collapsed long ago; had it been too low, no galaxies or stars would have formed. The initial expansion speed seems to have been finely tuned.
  • Repulsive force λ A relatively newly discovered force - a cosmic anti-gravity - controls the expansion of the universe, even though it has no discernible effect on scales less than a billion light years. It is destined to become ever more dominant over gravity and other forces as our universe becomes ever darker and emptier. Fortunately for us, λ is very small. Otherwise its effect would have stopped galaxies and stars from forming, and cosmic evolution would have been stifled before it could even begin.
  • Texture of the universe Q = 1/100,000: In order for galaxies to form as they have, there needed to be an irregularity in the "texture" of the universe. This "texture" was imprinted into the fabric of space during the big bang and initial expansion. Rees tells us that this number is the "ratio of two fundamental energies," however he does not clearly explain what these two energies are and how exactly they created the "texture." This section of the book I felt was very poorly written for the goal of explaining this number.
  • Dimensions D=3: The sixth crucial number has been known for centuries, although it's now viewed in a new perspective. It is the number of spatial dimensions in our world. Rees very, and I mean VERY, vaguely discusses the string theory which involves 10 spacial dimensions and the importance of us being in a three dimensional universe.

Overall, I was disappointed with the way Rees approached writing this book. I understand it was written to be a layman's introduction, but I feel that Rees could have written it more concisely. Much of the book was reminiscent of an old man rambling on about his journey of something trivial like checking the mail. Much of the good information that this book should have been more focused on was instead only vaguely covered.

Even though I was left wanting more, I still rate this book highly because I did in fact learn a few new things. It is worth reading by anybody who is interested in cosmology who might not already know a lot about it - but don't expect to come out satisfied and fully informed. I have already ordered two more books by Rees - Before The Beginning and Our Cosmic Habitat - which I hope will probe more deeply into the details of our wondrous universe.

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