SUPERSTRINGS AND OTHER THINGS to discussions about the current theories about the structure of matter, the nature of time, and the beginning of the univers Since the book is conceptual, I have kept simple mathematical for- mulas to a minimum. I have used short, simple algebraic deriva- tions in places where they would serve to illustrate the discovery (for example le, in describing Newton s incredible beautiful discovery of the universal law of gravitation). These short forays into elementary algebra can be skipped without loss of continu- ity. The reader who completes the book will be rewarded with basic understanding of the fundamental concepts of physics and will have a very good idea of where the frontiers of physics lie at the present time I have divided the book into seven parts. Part 1 starts with some introductory concepts and sets the stage for our study of physics. Part 2 presents the science of mechanics and the stud of energy. Part 3 follows with an introduction to the structure of matter, where we learn the story of the atom and its nucleus The book continues with thermodynamics in Part 4, the concep- tual development of electricity and magnetism in Part 5, waves and light(Part 6), and finally, in Part 7, with the rest of the story of modern physics, from the development of quantum theory and relativity to the present theories of the structure of matter Acknowledgments I wish to thank first my wife, Dr Luz Marina Calle, a fellow NASA research scientist and my invaluable support throughout the many years that writing this book took. She witnessed all the ups and downs, the difficulties, setbacks, and the slow progress in the long project. She read the entire manuscript and offered many suggestions for clarification, especially in the chapters where, as a physical chemist, she is an expert wish to thank Professor Karen Parshall, of the University of Virginia, who very carefully and thoroughly read the first draft of the first four chapters and made many suggestions. I also thank Professors George H Lenz, Scott D Hyman, Joseph Giammarco, and Robert L Chase in the physics department at Sweet Briar College, who read all or part of the manuscript and offered
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Preface many comments. I am grateful to Karla Fauld coner for many of the illustrations that appear in the book. For their help with different spects of the preparation of the manuscript, I am indebted Gwen Hudson, Rebecca Harvey, and Rachelle Raphael. I would especially like to acknowledge the invaluable help of my son Daniel, now a software engineer at Digital Paper, who read entire manusc cript, made many important suggestions and was my early test for the readability of many difficult sections No book can be written without the important peer review process. The criticisms, corrections and, sometimes, prais made the completion of this book possible. Over a dozen university physics professors reviewed this book during the different stages of its development. I wish to thank them for their invaluable advice. The work of two reviewers was particu- larly important in the development of the book. I appreciate the comprehensive reviews of Professor Michael J Hones at Villanova University, who reviewed the manuscript four times, offering criticism and advice every time. Professor Kirby W Kemper at Florida State University reviewed the book several times and suggested changes, corrections, and better ways to describe or explain a concept. The book is better because of them Finally, I wish to thank Nicki Dennis, Simon Laurenson and Victoria Le Billon at IOP Publishing, and Graham Saxby, for their understanding and for their efficiency in converting my manu- script into this book Carlos i calle Kennedy Space Center, Florida XVIl
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PHYSICS: THE FUNDAMENTAL SCIENCE What is physics? Physics deals with the way the universe works at the most funda- mental level. The same basic laws apply to the motion of a fallin nowflake, the eruption of a volcano, the explosion of a distant star, the flight of a butterfly or the formation of the early universe It is not difficult to imagine that, some thirty thousand years ago, during a cold, dark spring night, a young child, moved per haps by the pristine beauty of the starry sky, looked at his mother nd, in a language incomprehensible to any of us today, asked her: Mother who made the world? To wonder how things come about is, of course, a universal man quality. As near as we can tell, human beings have been preoccupied with the origin and nature of the world for as long as we have been human each of us echoes the words of the great Austrian physicist Erwin Schrodinger, "I know not whence I came nor whither i go nor who I am,and seeks the answers Here lies the excitement that this quest for answers brings to our minds. Today, scientists have been able to pierce a few of the veils that cloud the fundamental questions that whisper in our minds with a new and wonderful way of thinking which is firmly anchored in the works of Galileo, Newton, Einstein, Bohr, Schrodinger, Heisenberg, Dirac and many others whom we shall meet in our incursion into the world of physics Physics, then, attempts to describe the way the universe works at the most basic level. Although it deals with a grea variety of phenomena of nature, physics strives for explanations with as few laws as possible. Let us, through a few examples, taste some of the flavor of physics
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SUPERSTRINGS AND OTHER THINGS Figure 1.1. The laws of physics apply to a falling snowflake(courtesy WPWirgin), the explosion of a star or the eruption of a volcano(courtesy NASA) We all know that if we drop a sugar cube in water, the sugar dissolves in the water and as a result the water becomes thicker denser; that is, more viscous. We, however, are not likely to pay a great deal of attention to this well-known phenomenon. One inquisitive mind did One year after graduating from college, the young Albert Einstein considered the same phenomenon and did, indeed pay attention to it. Owing to his rebellious character, Einstein had been unable to find a university position as he had wanted and was supporting himself with temporary jobs as tutor or as a substitute teacher. While substituting for a mathematics teacher in the Technical School in Winterthur, near Zurich, from May to July 1901, Einstein started thinking about the sweetened water 4
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Physics: The Fundamental Science problem. The idea . may well have come to Einstein as he was having tea, writes a former collaborator of Einstein Einstein simplified the problem by considering the sugar molecules to be small hard bodies swimming in a structureless fluid. This simplification allowed him to perform calculations that had been impossible until then and that explained how the sugar molecules would diffuse in the water, making the liquid more viscous This was not sufficient for the twenty-two-year-old scientist. He looked up actual values of viscosities of different solutions of sugar in water, put these numbers into his theory and obtained from his equations the size of sugar molecules! He also found a value for the number of molecules in a certain mass of substance(Avogadros number). With this number, he could calculate the mass of any atom. Einstein wrote a scientific paper ith his theory entitled"'A New determination of the sizes of Molecules Figure 1.2. Albert Einstein
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