Just Six Numbers

In 'Just six numbers' Rees examines the question of why the universe seems so finely tuned for life. He looks at six dimensionless parameters of the universe, and explains why each had to have the value that it does in order for life to arise. The book is well written, by an expert in the subject, although sometimes I felt that it lacked the enthusiasm that a less knowledgable writer might bring. But there are no equations, and a few well placed diagrams, so I can recommend it to anyone who wants an expert view on some of the intruiging questions of life in the universe.

The first number is N, the ratio of the electric force to the gravitational force between two protons. This is followed by the efficiency of hydrogen fusion ε and then the two cosmological parameters Ω and λ. The last two numbers are Q,the measure of inhomogeneity in the early universe and 3, the number of space dimensions.

In between the chapters on the numbers themselves there are 'Our Cosmic Habitat' chapters, leading towards Rees' favoured explanation of the fine tuning - that of multiple universes. Possibly Rees decided that the 6 numbers weren't the best way to get his ideas across, since a couple of years later he wrote a whole book with the same title as these intermediate chapters.