دانلود کتاب ماهیت زمان

This book reviews and contrasts contemporary and historical perceptions of time from scientific and intuitive human points of view. Ancient and modern clocks, Augustinian ideas, the deter-ministic Newtonian universe, biological clocks, deep time, thermodynamics, quantum mechan-ics, and relativity all contribute to the perspective. The focus is on what can be inferred from established technologies and science as opposed to futuristic speculation. Chapter 1 describes clocks, including the cesium atomic clocks establishing the current global time standard, a history of clock development, biological clocks, phylogenetic trees, radioac-tive dating, and astronomical methods to determine the age of the universe. Chapter 2 poses ancient questions about time not fully addressed by an understanding of the technical nature of clocks. An early summary of some of these questions as described by Augustine in the 3rd century CE is followed by a description of how Newton, 1300 years later, introduced a concep-tion of time which provided some answers, such as the nature of an infinitesimally short present. Implications concerning the reality of events in the past, present, and future are also discussed. The Newtonian picture is contrasted with the intuitive human one and the possibilities of time travel and temporal recurrence are briefly discussed. Chapter 3 introduces the second law of thermodynamics and addresses how it is compatible with a time-reversible Newtonian descrip-tion of a universe, even though it appears to define an “arrow of time.” The nature of entropy and its relation to coarse graining and emergence play a central role in the discussion. Chapter 4 discusses ways in which quantum mechanics has altered the Newtonian perspective, accounting for various interpretations of the meaning of quantum mechanics with regard to time. Chapter 5 describes basic elements of special relativity and their implications for the nature of time. Time dilation and the fact that even the temporal order of events can be different as recorded in differ-ent frames of reference are described. The examples are chosen to avoid evocation of currently summarizes how the development of science since then has addressed them. This book was originally developed for an interdisciplinary seminar for beginning undergradu-ates at the University of Minnesota. It uses a small amount of algebra, mainly in supplemen-tary appendices, and does not assume any prior knowledge of physics, chemistry, biology, or astronomy. In contrast to many semipopular books on time, it avoids speculation either about engineering (techno-optimism) or physical theory (strings, loop quantum gravity, black hole en-tropy). Instead, it takes a more grounded approach and describes what is currently known (and not known) to help both students and the general reader make better sense of time. J. Woods Halley is a Professor at the University of Minnesota in Minneapolis. His research group studies electrochemical phenomena, including the origin of life, as well as low temperature phas-es of many-body systems, including superfluidity and superconductivity, using analytical theory and computer simulation. He was educated at the University of California, Berkeley and the Massachusetts Institute of Technology and is a Fellow of the American Physical Society. He has previously published books on the likelihood of extraterrestrial life and statistical mechanics.