Book review

Especially after 1965, when Penzias and Wilson discovered the 3K Cosmic background radiation, which seems to confirm the Big Bang model, the interest for general relativity and cosmology has grown rapidly. On the other hand, most of the books published until now in this area are or to sophisticated for a beginner, or nontechnical. There is a single notable exception: Weinberg - Gravitation and Cosmology, Wiley, 1972. Unfortunately, the cosmology itself grew in these twenty years and even this one is, in part, out of date. It is for these reasons that this book, written by a famous Indian cosmologist, was very good received at its first publication, ten years ago (Bartlett and Jones, 1983).

In the following, I'll try to reveal why is this book succeeful. It should be sayed that the author follows an approach much different from those found in ether texts. One of the main goal of this approach is to remove a common prejudgement, regarding cosmology more as an appendage of general relativity. As result, the relative importance of the two subjects has been inverted in the text. It is emphasized that, actually, at least for a beginner, it is not necessary to know much relativity in order to understand cosmology. So, the only role of general relativity in the book is to permit the construction of the geometric background for cosmology. After that, the Friedmann universe is studied in some details. Then, the author concentrates, for three chapters, on the physical aspects of the standard (Big Bang) model, the discussion including: the early universe, the nucleosynthesis, the very early universe, structure formation, a.o. At this stage, he tries to make justice to a class of alternative cosmologies, including a lot of personal contributions. It is not forgotten another important part of cosmology, namely the observational part. In two chapters there are discussed the most important local observations of cosmological significance, as well as the observations of the distant parts of the Universe. The author reports the most important observational results of the last years, emphasizing, at the same time, the possible sources of errors. The book finishes with a critical overview of standard and alternative cosmologies.

The level of the book is advanced undergraduate / beginner graduate and it is very suitable to be used as a textbook for courses of general relativity and cosmology at this level. There are a lot of exercises (about 400), most of them of computational nature, as well as many worked examples. For the use of the reader, the author added a table of constants, a glossary of symbols, a bibliography and an index. The new edition is updated, including the new achievments in the field (e.g. inflation theory, cosmic strings a.o.) and new observational results. Narlikar confirmes here, once more, his great talent of writer, not only that of scientist. (He is the author, or co-author of several books, e.g. "The Primeval Universe", Oxford University Press, 1988, an excellent nontechnical introduction to the science of the universe). On the other hand, only a remarkable teacher, as Narlikar is, could make accessible for the beginner this difficult part of science, removing the nonsignificant technical details, but keeping all the facts of physical relevance. To give a final appreciation, let me quote from the foreword, signed by Fred Hoyle, another great name of modern cosmology: "This is not only an important book. It is the best book, and I believe by a considerable margin. Pity the student who doesn't work from it".