###
Author: Steven Weinberg

Published in: Fontana Paperbacks

ISBN: 978-1470-89054-4

File Type: pdf

File Size: 2 MB

Language: English

Author: Steven Weinberg

Published in: Fontana Paperbacks

ISBN: 978-1470-89054-4

File Type: pdf

File Size: 2 MB

Language: English

Published in: Fontana Paperbacks

ISBN: 978-1470-89054-4

File Type: pdf

File Size: 2 MB

Language: English

__Description__
The First Three Minute book grew out of a talk I gave at the dedication of the Undergraduate Science Center at Harvard in November 1973. Erwin Glikes, president and publisher of Basic Books, heard of this talk from a mutual friend, Daniel Bell, and urged me to turn it into a book. At first I was not enthusiastic about the idea. Although I have done small bits of research in cosmology from time to time, my work has been much more concerned with the physics of the very small, the theory of elementary particles. Also, elementary particle physics has been extraordinarily lively in the last few years, and I had been spending too much time away from it, writing non-technical articles for various magazines. I wanted very much to return full time to my natural habitat, the Physical Review. However, I found that I could not stop thinking about the idea of a book on the early universe. What could be more interesting than the problem of Genesis? Also, it is in the early universe, especially the first hundredth of a second, that the problems of the theory of elementary particles come together with the problems of cosmology. Above all, this is a good time to write about the early universe. In just the last decade a detailed theory of the course of events in the early universe has become widely accepted as a 'standard model'. It is a remarkable thing to be able to say just what the universe was like at the end of the first second or the first minute or the first year. To a physicist, the exhilarating thing is to be able to work things out numerically, to be able to say that at such and such a time the temperature and density and chemical composition of the universe had such and such values. True, we are not absolutely certain about all this, but it is exciting that we are now able to speak of such things with any confidence at all. It was this excitement that I wanted to convey to the reader.

I had better say for what reader this book is intended. I have written for one who is willing to puzzle through some detailed arguments, but who is not at home in either mathematics or physics. Although I must introduce some fairly complicated scientific ideas, no mathematics is used in the body of the book beyond arithmetic, and little or no knowledge of physics or astronomy is assumed in advance. I have tried to be careful to define scientific terms when they are first used, and in addition I have supplied a glossary of physical and astronomical terms (p. 165). Wherever possible, I have also written numbers like 'a hundred thousand million' in English, rather than use the more convenient scientific notation: 1011 However, this does not mean that I have tried to write an easy book. When a lawyer writes for the general public, he assumes that they do not know Law French or the Rule Against Perpetuities, but he does not think the worse of them for it, and he does not condescend to them. I want to return the compliment: I picture the reader as a smart old attorney who does not speak my language, but who expects nonetheless to hear some convincing arguments before he makes up his mind.

For the reader who does want to see some of the calculations that underlie the arguments of this book, I have prepared 'A Mathematical Supplement', which follows the body of the book (p. 175). The level of mathematics used here would make these notes accessible to anyone with an under graduate concentration in any physical science or mathematics. Fortunately, the most important calculations in cosmology are rather simple; it is only here and there that the finer points of general relativity or nuclear physics come into play. Readers who want to pursue this subject on a more technical level will find several advanced treatises I should also make clear what subject I intended this book to cover. It is definitely not a book about all aspects of cosmology. There is a 'classic' part of the subject, which has to do mostly with the large-scale structure of the present universe: the debate over the extra galactic nature of the spiral nebulae; the discovery of the red shifts of distant galaxies and their dependence on distance; the general relativistic cosmological models of Einstein, de Sitter, Lemaitre, and Friedmann; and so on. This part of cosmology has been described very well in a number of distinguished books, and I did not intend to give another full account of it here. The present book is concerned with the early universe, and in particular with the new understanding of the early universe

that has grown out of the discovery of the cosmic microwave radiation background in 1965.

Of course, the theory of the expansion of the universe is an essential ingredient in our present view of the early universe, so I have been compelled in Chapter 2 to provide a brief introduction to the more 'classic' aspects of cosmology. I believe that this chapter should provide an adequate background, even for the reader completely unfamiliar with cosmology, to understand the recent developments in the theory of the early universe with which the rest of the book is concerned. However, the reader who wants a thorough introduction to the older parts of cosmology is urged to consult the books listed under 'Suggestions for Further Reading'.

I had better say for what reader this book is intended. I have written for one who is willing to puzzle through some detailed arguments, but who is not at home in either mathematics or physics. Although I must introduce some fairly complicated scientific ideas, no mathematics is used in the body of the book beyond arithmetic, and little or no knowledge of physics or astronomy is assumed in advance. I have tried to be careful to define scientific terms when they are first used, and in addition I have supplied a glossary of physical and astronomical terms (p. 165). Wherever possible, I have also written numbers like 'a hundred thousand million' in English, rather than use the more convenient scientific notation: 1011 However, this does not mean that I have tried to write an easy book. When a lawyer writes for the general public, he assumes that they do not know Law French or the Rule Against Perpetuities, but he does not think the worse of them for it, and he does not condescend to them. I want to return the compliment: I picture the reader as a smart old attorney who does not speak my language, but who expects nonetheless to hear some convincing arguments before he makes up his mind.

For the reader who does want to see some of the calculations that underlie the arguments of this book, I have prepared 'A Mathematical Supplement', which follows the body of the book (p. 175). The level of mathematics used here would make these notes accessible to anyone with an under graduate concentration in any physical science or mathematics. Fortunately, the most important calculations in cosmology are rather simple; it is only here and there that the finer points of general relativity or nuclear physics come into play. Readers who want to pursue this subject on a more technical level will find several advanced treatises I should also make clear what subject I intended this book to cover. It is definitely not a book about all aspects of cosmology. There is a 'classic' part of the subject, which has to do mostly with the large-scale structure of the present universe: the debate over the extra galactic nature of the spiral nebulae; the discovery of the red shifts of distant galaxies and their dependence on distance; the general relativistic cosmological models of Einstein, de Sitter, Lemaitre, and Friedmann; and so on. This part of cosmology has been described very well in a number of distinguished books, and I did not intend to give another full account of it here. The present book is concerned with the early universe, and in particular with the new understanding of the early universe

that has grown out of the discovery of the cosmic microwave radiation background in 1965.

Of course, the theory of the expansion of the universe is an essential ingredient in our present view of the early universe, so I have been compelled in Chapter 2 to provide a brief introduction to the more 'classic' aspects of cosmology. I believe that this chapter should provide an adequate background, even for the reader completely unfamiliar with cosmology, to understand the recent developments in the theory of the early universe with which the rest of the book is concerned. However, the reader who wants a thorough introduction to the older parts of cosmology is urged to consult the books listed under 'Suggestions for Further Reading'.

## 0 comments: