- Hardcover: 320 pages
- Publisher: Knopf; 1 edition (November 9, 2010)
- Language: English
- ISBN-10: 0307272850
- ISBN-13: 978-0307272850
- Product Dimensions: 6.6 x 1.2 x 9.6 inches
- Shipping Weight: 1.4 pounds (View shipping rates and policies)
- Average Customer Review: 16 customer reviews
- Amazon Best Sellers Rank: #2,277,005 in Books (See Top 100 in Books)
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Once Before Time: A Whole Story of the Universe 1st Edition
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From Publishers Weekly
Starred Review. If it's possible to write a literary treatment of cutting-edge cosmology, groundbreaking physicist Bojowald has done it, complete with illustrations of abstract sculpture and quotes from thinkers as diverse as Nietzsche, Schopenhauer, Charles Dickens, and Joseph Heller. Bojowald, a professor of physics at Penn State, explores loop quantum theory, an idea he developed as a postdoctoral student in 2000, to fill in the gaps left by 20th-century physics. Despite advances like relativity theory, curved space, and quantum theory, physics falters when it comes to explaining what happened before the Big Bang, when time, space, matter, and energy were all shrunk into a bizarre entity called a singularity, where math and logic as we know them failed. Later, string theory, with its extra dimensions and elegant equations, offered promise, but only with loop quantum cosmology were physicists able to see the universe be born, expand, shrink, and be reborn, over and over again. Bojowald largely avoids mathematics for accessibility, but that can leave his writing dense with rigor as he strives to cover "the Whole Story." Readers willing to meet his challenge will find a fascinating new universe revealed by his enthusiastic firsthand approach. 37 illus. (Nov.) (c)
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In theoretical physics, gravity can be an intractable problem. At extreme values prevalent near the big bang or black holes, general relativity can’t accommodate it. String theory purports to be a solution, but not all physicists are on the string bandwagon. One such recalcitrant, Bojowald champions a rival theory called loop quantum gravity, which he here valiantly presents to the nonmathematical. If his explanation daunts some science readers, its implications will be sufficiently clear and exciting to pull them through his text, because those involve the start of the big bang and the interior of a black hole. Notionally, each one is a singularity as Bojowald describes the failure of mathematics when energy density goes to infinity and space collapses to zero volume. Loop quantum gravity offers an escape from these terrifying places by acting like a quantum-mechanical Atlas who holds space open just enough so that physics—the universe—can continue to exist. Complex but comprehensible, Bojowald’s treatment of loop quantum gravity should compete with popular string-theory titles such as Endless Universe (2007), by Paul Steinhardt and Neil Turok. --Gilbert Taylor
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The book opens with introductions to gravity and quantum theory, giving a particularly interesting account of general relativity, using the GPS as an example. These themes combine in the central chapter describing loop quantum gravity, a candidate 'theory of everything'. Essentially it is a quantum version of Ashtekar's formulation of general relativity based on space alone rather than space-time. ( Its widely followed rival, string theory, is more of a fresh start, based on complicated geometries of many dimensions. ) The fundamental unit is the loop as a quantum of space, determined by its quantised area and orientation; with space being a discrete 'wave function' of a vast grid of intersecting loops. Its successive states may be numbered in order, to play the role of time, and they evolve according to difference equations rather than the familiar differential equations. However a fully covariant list of equations has yet to be found.
A big advantage of loop quantum gravity is that infinities of compression are prevented as intense energy waves, unable to be accommodated by the grid, turn into a repulsive force. This leads to very different accounts of black holes and the big bang from those of general relativity with its singularities. In cosmology, extrapolating back to to the beginning of our universe, Bojowald himself was able to formulate and solve simplified equations to show that space would pass through a single empty cell to an inside-out 'mirror' space, where each loop has a reversed orientation. In physical reality the discreteness of time would 'jump' the universe across the gap, missing out the single empty cell. Another chapter discusses the issues of inflation and dark energy in this context.
A chapter on black holes points out the recent realisation that the singularity attributed to a black hole in general relativity is a final time for its interior, rather than a final destination within it. Under loop quantum gravity a black hole could be passed through, perhaps into a daughter universe. Alternatively, when the event horizon of a black hole eventually evaporates through Hawking radiation, its compressed interior could be released with a huge amount of energy.
There is a more philosophical chapter seeking to remove the fish-hooks from the notion of the 'arrow of time' and from common considerations of the entropy of the universe. The passage on the arrow of time is in itself worth the price of this volume, though I feel that the remarks on entropy do not finally clinch the matter. Beyond this the book tails off in short chapters on wider issues such as the history of cosmogony and the limits of science.
provides the reader with a nice overview of general relativity (GR) and quantum mechanics (QM) and then addresses current attempts by physicists to merge GR and QM into a theory of Quantum Gravity. He gives the reader an intuitive feel for the two major current theories of Quantum gravity; string theory and loop quantum gravity. In addition , he discusses black holes, the arrow of time, and cosmogony. Bojowald concludes the book with chapters on a theory of everything and the limits of science. This book does not read like
a light novel but for anyone wanting to delve into a theory which may take us to a time before the big bang, it is a great read.
Finally, the current low price allows anyone to obtain an excellent book on current attempts to create a new theory of gravity and it also takes the reader to the cutting edge of contemporary theoretical physics. If you have ever wondered about the beginning of time and space and what may have come before, spend a few bucks and get a copy of this book.
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