The Expanding Universe

The years followoing Einstein's development of general relativity were heady times for cosmology as the new thinking was applied to the universe as a whole. 'The Expanding Universe' by Sir Arthur Eddington gives the reader a taste of the state of play in the early 1930's, soon after Hubble had discovered the recession of the galaxies, and in particular shows the questions which were being asked. How did the expansion fit in with other ideas of the age of the universe? Did it support the 'fireworks' (big bang) theory of it's origin? The book is based on a public lecture given by Eddington, and so it is easy for the reader to follow Eddington's line of argument.

Despite the claim that the expansion of the universe made the cosmological constant redundant, Eddington was a strong supporter of a positive cosmological constant, which enabled the universe to start from a static model and gradually expand (no big bang here), but most of all Eddington wanted the universe to be finite. The book introduces the popular 'expanding balloon' model of the universe. Some of Eddington's ideas haven't stood the test of time so well though. In the last chapter he gives a long calculation based on all sorts of numbers such as 137 and the mass of the electron to show why the Hubble constant must be around 600 km/s/Mpc. It is now accepted that it is an order of magnitude less than that.