The Nine Numbers of the Cosmos by Michael Rowan-Robinson, Oxford University Press, ISBN 0198504446, £16.99/$32.50
IN THE beginning was the big bang. Our Universe began at a finite time in the past in a state of unimaginably high density and temperature. And it’s been expanding and cooling ever since. Cosmologists try to work out what’s happening in the evolving Universe from this model. But it’s incomplete. Because we don’t understand the big bang itself, we can’t predict many important parameters of the Universe—such as its age and density. Instead, we have to rely on observation.
For decades, astronomers have been trying to measure these unknown quantities to find the missing pieces of the cosmic jigsaw. In the past few years dramatic progress has been made, thanks to technological developments like the Hubble Space Telescope. Cosmologists now feel that the answers to many important questions are within reach.
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The Nine Numbers of the Cosmos is a survey of modern cosmology with the missing numbers as its theme. They are: the density of “ordinary” or baryonic matter; the Universe’s anisotropy or lumpiness; the Hubble constant or rate of expansion of the Universe; its age; temperature of the microwave background; the density of non-baryonic cold dark matter; the tilt, the string tension or density of hot dark matter—three numbers, two of which are probably zero, that might fix the failures of the cold dark matter model; the cosmological constant; and the Universe’s star formation history.
It’s a successful device that focuses attention on a series of well-defined issues. But there are many more than nine numbers to chose from, and I am not convinced that Rowan-Robinson has picked wisely. “The Universe’s star formation history” is not a number at all.
Crucially, none of Rowan-Robinson’s nine numbers relates to the fact that there must always have been more matter than antimatter in our Universe. If it weren’t so, we wouldn’t be here. Matter and antimatter would have annihilated each other, leaving only radiation. What caused this asymmetry is still unknown, but it was vital for our existence.
A few weeks ago Lawrence Krauss reviewed Just Six Numbers (91av, 4 December 1999, p 48). In that book Martin Rees paints a picture of the Universe in a similar numerological vein to Rowan-Robinson. The two authors do cover some similar ground, but these books are actually quite different in style and scope. Rowan-Robinson has produced a more comprehensive survey of the subject, at the price of a less coherent overall structure. Both convey very well the sense of excitement felt by cosmologists as a complete picture of the cosmos begins to take shape.
