PREFACE As a research scientist at NASA Kennedy Space Center working on planetary exploration, I am very fortunate to be able to experi ence first hand the excitement of discovery. As a physicist, it is not surprising that I find science in general and physics in particular captivating. I have written this book to try to convey my excite- ment and fascination with physics to those who are curious about nature and who would like to get a feeling for the thrills that scientists experience at the moment of discovery The advances in physics that have taken place during the twentieth century have been astounding. One hundred years ago, Max Planck and Albert Einstein introduced the concept of the quantum of energy that made possible the development of quantum mecha panics. This revolutionary theory opened the doors for the breathtaking pace of innovation and discovery that we have witnessed during the last fifty years At the beginning of the new century, physics continues its inexorable pace toward new discoveries. An exciting new theory might give us the"theory of everything, the unification of all the forces of nature into one single force which would reveal to us how the universe began and perhaps how it will end Although these exciting new theories are highly mathemati cal, their conceptual foundations are not difficult to understand As a college professor for many years, I had the occasion to teach physics to nonscience students and to give public lectures on physics topics. In those lectures and presentations, I kept the mathematics to a minimum and concentrated on the concepts The idea for this book grew out of those experiences This book is intended for the informed reader who is inter- ested in learning about physics. It is also useful to scientists in other disciplines and to professionals in non-scientific fields The book takes the reader from the basic introductory concepts.       
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