A Short History of Astronomy

This book, which I had never even heard of, cost me a few francs at one of the second-hand stalls at the market, and it could easily have sat on our shelf for the next five years without being looked at; it didn't seem like anything special. But when I opened it the other day, I immediately discovered that my first impression had been quite wrong. Berry has written a truly excellent one-volume history of astronomy, and it was apparently a standard text for nearly fifty years after it first appeared in 1898. 


Berry is a good writer, neither too serious nor too frivolous, and with a pleasantly dry sense of humour; he evidently knows his subject very well. His presentation is impressively balanced: he devotes appropriate amounts of space to all periods of astronomical history up to his time (the Greeks, the Arabs, the Renaissance, the Newtonian period, the 19th century), and he favours neither observational nor theoretical aspects of astronomy but gives equal weight to both. He gives an excellent semi-technical summary of Ptolemaic astronomy and describes how it was further improved by the Arabs, and then by Copernicus; the continuity with Copernicus's work is particularly well done. 


He then explains how Kepler, thanks to Tycho Brahe's painstaking observations, was finally able to create something that was essentially different from Ptolemy's system; in general, one of the most appealing aspects of the book is the way in which it highlights the interplay between theory and practice. His chapter on Herschel, a person I had not known much about, was interesting. I was aware that he had discovered Uranus, but had not heard about his pioneering work on the classification of binary stars, clusters and nebulae. He also has a good chapter on the eighteenth century gravitational theorists - Clairaut, D'Alembert, Lagrange and Laplace - who achieved the remarkable feat of taking over Newton's work and converting a piece of English science into something that for over a century was quintessentially French. Berry's thought-provoking explanation is that the English mathematicians tried to follow the lines of the Principia too closely, and imitate Newton's geometrical style of proof; but this was something that only a genius of Newton's calibre could handle, and they got nowhere. The French, more pragmatically, developed the calculus, which turned out to be a far better direction in which to explore.


Up to about 1825, there is hardly a thing I can point to which I would want to criticize. (Well, he says nothing about the Babylonians; though when he was writing, no one knew about their work). But as he approaches what, for him, is the present day, it is fascinating to notice the things he is not seeing, which will soon become of critical importance. He chides Herschel for obstinately maintaining that some nebulae lie outside our own galaxy. He supports Lord Kelvin's theory that the Sun's energy comes from gravitational contraction, ignoring the fact that this gives an age for the Solar System that is at least an order of magnitude less than the age of the Earth, as determined from geological records. Although he mentions Michelson's accurate determination of the speed of light, there is not a word about the Michelson-Morley experiment (1887), which was just about to result in the Special Theory of Relativity. But the most striking passage of all was this one, concerning Bradley's explanation of the phenomenon of the aberration of light in terms of Newton's "corpuscular theory", then completely out of fashion:

One difficulty in the theory of aberration deserves mention. Bradley's own explanation, quoted above, refers to light as a material substance shot out from the star or other luminous body. This was in accordance with the corpuscular theory of light, which was supported by the great weight of Newton's authority and was commonly accepted in the 18th century. Modern physicists, however, have entirely abandoned the corpuscular theory, and regard light as a particular form of wave-motion transmitted through the ether. From this point of view Bradley's explanation and the physical illustrations given are far less convincing; the question in fact becomes one of considerable difficulty, and the most careful and elaborate of modern investigations cannot be said to be altogether satisfactory. The curious inference may be drawn that, if the more correct modern notions of the nature of light had prevailed in Bradley's time, it must have been very much more difficult, if not impracticable, for him to have thought of his explanation of the stellar motions which he was studying; and thus an erroneous theory led to a most important discovery.

Seven years later, Einstein would launch his idea of the "light-quantum", which would soon become the photon; and thus the corpuscular theory would live again. But Berry, evidently a very intelligent and knowledgeable person, has no inkling of this. One cannot help wondering: what vital clues are lying right under our noses, patiently waiting for us to discover them? Reviewed by Manny at Goodreads