Time and Man by L. R. B. Elton and H. Messel (review)

Leonardo, Vol. 12. pp. 333-347 Pergamon Press 1979. Printed in Great Britain BOOKS Readers are invited to recommend books to be reviewed. In general, only books in English and in French can be reviewed at this stage. Thosc who would like to be added to Leonardo’s panel of reviewers should write to the FounderEditor . indicating their particular interests. The CosmicFrontiersof GeneralRelativity. W. J. Kaufmann, 111. Little, Brown, Boston, 1977.306pp.. illus. Reviewed by Hendrik Van Dam* This book concerns a topic that should be of interest to any lay person: the present ideas of physicistsand astronomers about the structure of space and time. These ideas have to do with the structure of the universe on a larger scale (cosmology) and on a somewhat smaller scale (hypothetical black holes). The text is well written and contains a large number of attractive illustrations several of which are original. There is a tremendous amount of detail about the exciting structure of space-time associated with black holes. The book contains a number of technical errors that I shall list at the end of this review. These errors arenot disturbing, but what isdisturbing isthat hardly any attempt has been made to explain the basic ideas underlying the structure of black holes. The notion of ‘curvature’ is not explained, not even a reference is given [such a reference could have been C. 1. J. Dodson, Physics Bulletin, p. 387 (1976)], and yet things such as the Ricci tensor are mentioned. As Dodson, and others, have shown these crucial ideas about curvature can be quite well explained to the lay public. The special theory of relativity is not well explained either; this could have been done clearly and briefly. As a consequence, the tools needed to understand black holes are not given. Without these tools someone who is not already an expert and who tries to understand this book will have a hard and frustrating time. Another book that does a muchbetterjobexplainingthisexciting material is P. C. W. Davies Space and Time in the Modern Universe (Cambridge: Cambridge Univ. Press, 1977). Technicalcriticism:( I ) Almost I20 pages of this book are used to give a discussion of the ‘inside’of black holes. This discussion is based on the known structure of a small family of solutions to Einstein’s equations. It has been shown that the outside of the black holes in this family is typical for what will be observed for realisticblack holes. Recent research indicates, however, that the insidestructure of the black holes in this family is not typical for what one may find in nature. (2) Figures 3-8 and 13-8 suggest, erroneously, that, in order to maintain a constant velocity, one needs to keep the propelling rockets running. (3) Figure 7-7 is somewhat confusing; the main cause for the deflection of light is the curvature of space-time, not the curvature of space as suggested by this illustration. (4) There is a mistake in Figures 14-3 to 14-6. The first three describe Schwarzschild solutions, the last describes a black hole. None of these figures describes a hypothetical white hole. (5) In Figure 8-1 I, the sideways compression typical of tidal forces is not shown. Again, there is no explanation at all of tidal forces, let alone of their relation to curvature. Time and Man. L. R. B. Elton and H.Messel. Pergamon Press, Oxford, 1978. 114pp., illus. Paper, f 1.95. Reviewed by Peter L. Young** *Dept. of Physics and Astronomy, University of North Carolina, Chapel Hill, NC 27514, U.S.A. **2 Hakea Court, Churchill, Victoria, Australia 3842. This is a friendly little book that gently leads the reader through the avenues of enquiry directed towards answering a question that mocks humans in its simplicity--‘What isTime?’. I sayit is a friendlybook becauseit seeksto coax the reader through difficult topics. At all stages it presumes that readers know less than the writers about the latest developments in contemporary physics, astronomy, geologyand biology. For this reason, it is well suited to an educated lay public and the first-year tertiary student. It is a little book. In order to make this series (Pergamon International Library of Science...