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The Natural Philosophy of Space and Time I need to apologize for the formality of the title of this review: I think most other reviewers (and even the editorial blurb writers) miss the importance of this book. This is not just an introduction to modern physics for the general reader, but a deep discussion of the nature of space and time. It is of interest to everyone, including physics, math and philosophy students. Even specialists with PhDs will find priceless insights in this book. Apparently the only exceptions are insecure snobs who are turned-off by the informal language and by the use of "down-home American analogies that mention Marge and Bart and Springfield". (How terrible!) I will give a summary of this book in the following. Section I (chapters 1 to 4) discuss space. In chapter 3 the author explains the relativistic aspects of space. In this chapter the author gives one of his priceless explanations of difficult concepts of physics: He explains the slowing down of moving "clocks" by the fact that everything moves through space-time at the speed of light. If you don't move in space, you move with maximum speed in time. The faster you move in space, the slower you move in time. This is not just a qualitative explanation, by the use of Pythagoras's theorem you can derive from it the correct quantitative result! Chapter 4 discusses the nonlocal aspects of Quantum mechanics (QM). It contains one of the best explanations of Quantum entanglement and of the Bell's inequalities available. It shows that the correlation of measurements done at different location cannot be explained by the Quantum systems being "pre-programmed" to give correlated results. The measurements really do influence each other, at a distance! All of this has been experimentally tested (by Alain Aspect, a French physicist, among others). Section II (chapters 5 to 7) deals with time, especially the reason why the future is different from the past. (We grow old, never younger, eggs splatter, never unsplatter, etc.) This is a difficult problem, because the basic laws of physics (Classical, Relativistic and Quantum alike) are symmetric in time. If the entropy grows in the future, it also has to grow in the past, contrary to everyday experience! The provisional solution to this problem is that the universe must have started in an extremely low-entropy state. Low entropy means low probability, so the universe must have started in a very unlikely state. Why this is possible is the theme of Section III (chapters 8 to 11), dealing with cosmology. Here it is shown that inflation, the theory that the universe underwent very fast, immense (of over 1000000000000000000000000000000 times) growth early on in its history, can explain the extremely unlikely nature of the original universe. This is the best explanation of why time has a definite direction. (The connection of the "arrow of time" with inflation was first pointed out by the physicist Paul Davies.) Inflation has been tested experimentally and confirmed, to an incredible level of accuracy. This is discussed in chapter 11, "Quanta in the Sky with Diamonds", where Green shows that satellite experiments have confirmed the prediction of inflationary theory for the fluctuations in the Cosmic Background Radiation (CBR) to an extraordinary degree of accuracy. This is particularly noteworthy because inflationary theory derives these fluctuations from Quantum effects! So the fluctuations that seeded the formation of clusters of galaxies have a Quantum origin! In Section IV, Green goes beyond inflation, into the full Quantum Gravity regime, and into Super String theory. In this section he shows his prejudices in favor of String Theory. This is normal, because scientists are people too and they are biased in favor of the theories they work on. In Section V, chapter 14 deals with near-term experiments that could confirm aspects of General Relativity and, possibly, String Theory. Discussed are "frame dragging" satellite experiments, gravitational wave detection, and the hunt for extra dimension. Also covered is the possibility of detecting suspersymmetric particles (this is necessary, but not sufficient to prove String Theory), the possibility of creating mini black holes at an accelerator lab, dark matter detection experiments and even more accurate CBR experiments. Chapter 15 deals with REALLY strange possibilities, like time travel, wormholes and teleportation. Chapter 16 goes back to the entropy of black holes and what it says about the intimate structure of space (time). The "Holographic Universe" idea is also discussed. In conclusion, this is a great discussion, at a level appropriate for all readers, of questions about space and time, both theoretical and experimental. This book is highly recommended: if you plan to read only one science book this year, "The Fabric of the Cosmos" should be it!