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Let’s start with the most important: this is a book worth reading. Whether you’re a professional physicist, a philosopher or just someone who’s interested in learning about the world in general, this book should be in your library and at hand.
The author, Sean Carroll, is a senior research associate at the prestigious California Institute of Technology, where he focuses mainly on questions related to cosmology, from inflation to dark energy. He has published a textbook on General Relativity and this is his first science popularization work.
Sean Carroll’s From Eternity to Here is a book about time, though not only about time. It starts with a simple question: why was the entropy so low in the past? This seemingly harmless question turns out to have so many ramifications that the author ends up driving us through the history of physics, from the 18th century to the present. The first chapters of the book are devoted to explaining the concept of entropy, which has had many -though compatible- formulations throughout history. Then, he goes on to tackle the book’s central issue: configurations with higher entropy are overwhelmingly more likely than configurations with lower entropy. Therefore, why is the entropy in our universe so low? The search for an answer takes him to explain relativity, first, then quantum mechanics and, finally, string theory. Carroll also explains the Big Bang and the theory of inflation, which is the current standard explanation for the origin of the universe. He then puts them into question and formulates a somewhat heretic hypothesis: what if the Big Bang wasn’t the beginning of time?
The explanations are simple but rigorous and not condescending, as is often the case in popularization books: the explanation of Boltzmann’s entropy is remarkable, as well as his defense of the so-called “many-worlds interpretation”, which should probably just be called “Quantum Mechanics Taken Seriously.”
Apart from how well it explains established physical principles, From Eternity to Here does a great job confronting physicists with what they still don’t understand, namely the arrow of time. His arguments are more than compelling, with the added bonus that Carroll is honest enough to label his speculations clearly and inform the reader whenever he’s treading on thin ice. His final explanation of the low entropy in the past is the only serious attempt this reviewer has seen that actually accomplishes what it intends.
From Eternity to Here is a long book, and Carroll doesn’t content himself with sticking to the subject matter, but also makes brief incursions into the nature of life and complexity and even comments on the meaning of existence at some stage. These are all welcome and refreshing stops along the way; his question about complexity -why does complexity go from low to high to low in our universe, as opposed to entropy?- is a deep one, and something worth looking into in itself.
In conclusion, From Eternity to Here is one of the best science popularization books around, and it is especially recommendable for professional physicists, many of whom unjustly disregard the questions presented in this book. Sean Carroll is a type of physicist that seems to have gone out of fashion: the type that wants to understand the world and not only predict experiment results. One can only hope this book helps to shift the tide his way.