Of celestial spheres and floaty discs 1

One of the scientific problems of being an astronomer is that you have to deal with the universe, and this simple word encompasses everything: planets, stars, galaxies, radiation, the composition of material, dark matter - the lot. But unfortunately, we still have very little idea as to where it came from, what it is really like at the present time, and how it is all going to end. It was ever thus.

At the dawn of civilisation, the natural philosophers envisaged a flat, disc-like Earth floating on water, with a distant heavenly sphere spinning around it. Then our cosmos included a host of gods, and we divided everything into an imperfect decaying inhabited planet made up of fire, earth, water and air, and a perfect, distant celestial sphere consisting of a mystical quinta essentia .

Since the Renaissance, we have introduced science and removed God. Today's universe is controlled by a combination of Newtonian gravitation and Einsteinian general relativity. The elements that make up the most distant heavenly bodies have been found to be just the same as those in the laboratory next door. The religious and philosophical views of yesterday have been replaced by reams of data from optical and radio telescopes, and the theoretical musings of a motley collection of applied mathematicians and astro-particle physicists.

Helge Kragh studies the history of modern physical sciences at the University of Aarhus in Denmark. He writes with engaging clarity and insight. His book is thought-provoking and enlightening, a joy from beginning to end. It's also accurately aimed at its university audience. Where notes are needed, they are provided. Where you thought it would be interesting to read more about a topic, there is a list of references.

What we now need to do is get this superb book used. Few respectable British universities are without departments of physics and astronomy. The later years of most of their undergraduate degree courses are enlivened by cosmology modules. Einstein's views, the Hubble expansion, the Robertson- Walker matrix, the early inflation, the physical and chemical wonders of the big bang, the cosmic microwave background and the newly found acceleration are all grist to the modern examination paper. But few students investigate the development of the subject. Are they too engrossed in physics and mathematics to bother with history? Or is the modern university science faculty devoid of anyone with a desire or ability to see and explain the "big picture"? Surely astronomers and physicists can appreciate the benefits and joys of a modicum of historical research.

And you cannot turn round and say: "We have no suitable textbook." Get students to read Kragh. Be thankful this professor has bothered to write such a superb book. They will benefit hugely, if only by realising the transitory nature of many of the historical "answers" to cosmological problems, and noting that many of today's scientific near-certainties might fade into obscurity in the not-too-distant future.

Who is it for? Students and professionals in astronomy, physics, history of science and anyone with an interest in the history of science.

Presentation: Excellent

Would you recommend it? Absolutely. Essential reading for astronomers.

David W. Hughes is professor of astronomy at Sheffield University.