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Cycles of Time: An Extraordinary New View of the Universe

60 customer reviews
ISBN-13: 978-0307265906
ISBN-10: 0307265900
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Editorial Reviews


“The hyper-density of this book made my brain feel simultaneously wiped out and dazzled.”
            -Boston Globe Best Science Books of 2011
“Radical . . .  A surprising and unorthodox work disguised in the jacket of a popular science book, Cycles of Time should prove both deeply enlightening and just as deeply mystifying for anyone who dares to follow along.”
            -Peter Woit, The Wall Street Journal
“An intellectual thrill ride . . . As Penrose builds a solid foundation for his argument in analyzing universal entropic accumulation and Newton’s Second Law, the reader senses something tremendous looming—mysterious and compelling as a black hole . . . A cosmological page-turner.”
            -Y. S. Fing, Washington Independent Review of Books
“If you’ll forgive a skiing metaphor, Cycles of Time is a black diamond of a book. But like all steep slopes, sometimes you take a moment from your struggles and look up, and in front of you is an utterly gorgeous view.”
            -Anthony Doerr, Boston Globe
“Profound . . . This fascinating book will surely become a classic in the history of cosmology.”
“Controversial but intriguing . . . Well worth the effort.”
“Intriguing . . . Penrose makes provocative arguments for his challenging new theory.”                  
           -Publishers Weekly

About the Author

Roger Penrose is Emeritus Rouse Ball Professor of Mathematics at the University of Oxford. He has received numerous prizes and awards, most notably the Wolf Foundation Prize in physics, which he shared with Stephen Hawking. He is the author of three previous books, including The Emperor’s New Mind. He lives in Oxford, England.

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Product Details

  • Hardcover: 304 pages
  • Publisher: Knopf (May 3, 2011)
  • Language: English
  • ISBN-10: 0307265900
  • ISBN-13: 978-0307265906
  • Product Dimensions: 6.4 x 1.1 x 9.5 inches
  • Shipping Weight: 1.4 pounds (View shipping rates and policies)
  • Average Customer Review: 3.6 out of 5 stars  See all reviews (60 customer reviews)
  • Amazon Best Sellers Rank: #574,965 in Books (See Top 100 in Books)

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Customer Reviews

Most Helpful Customer Reviews

239 of 245 people found the following review helpful By Dr. Roy Simpson on October 16, 2010
Format: Hardcover
Many who wish to buy this book will be familiar with the other works of Professor Roger Penrose (such as The Road to Reality). Some will be curious to learn about a new theory of the origin of the Universe. This book presents a radical new idea which Penrose has been developing in the past few years on the Big Bang: essentially the idea is that there was a pre-Big Bang era and there will be a post-Big Crunch era too.

So one could review both the book and the idea itself. Firstly some will worry about the level of mathematics presented in this book. In the main chapters there are equations such as S = k log V - Boltzmann's Equation. If you are not comfortable with this, then maybe you will not get the most from the book. However if you are comfortable with this and similar physics equations and numbers then the first section of the book is readable. Of course there are plenty of diagrams too. There is some hard maths however and this has been relegated to the Appendix (30 pages). This maths is very advanced and another of Penrose's technical books (Penrose and Rindler Volume 2) would be needed to understand it fully - so that is only for the experts. Given that the reader wont be learning this material in the present book it shows that there is some more complex machinery behind the scenes needed to comprehend the full idea.

In the first section the book returns to an old concern of Penrose namely the entropy present in the early universe: less than today - but why so much less? The chapter then focusses in on the Big Bang described using "Conformal Diagrams". The key on page 115 is important for reading these diagrams.

Part 3 introduces the new idea called Conformal Cyclic Cosmology (CCC).
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167 of 177 people found the following review helpful By Patrick J. Sullivan on May 6, 2011
Format: Hardcover Verified Purchase
Roger Penrose's latest book is an exposition of his latest cosmological speculations. As usual Penrose cheerfully overestimates the mathematical capabilities and accomplishments of the typical scientifically educated lay person his books are ostensibly aimed at. He presents what he sees as a baffling fact, the unusually low entropy state of the early universe, and gradually leads the reader up to his explanation of the nature of our universe. Though Penrose is coy throughout the book's first two sections about the details of his conjecture, the title gives it away and indeed this book is ultimately a speculation about cyclical universes. There are definitely some points of interest, and readers who enjoyed Penrose's earlier works such as The Emperor's New Mind will likely be intrigued by parts of the book. But while less overambitious than the author's sweeping Road to Reality, Cycles of Time is far denser than more accessible popular science works such as Stephen Hawking's A Brief History of Time, so those who found that bestseller to be of use mostly as bookcase filler might want to give Penrose a pass here.

The book is divided into three main sections: entropy and the Second Law of Thermodynamics; the Big Bang and the puzzling low-entropy state of the early universe; then the largest and most detailed concluding section.
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50 of 53 people found the following review helpful By Light Pebble on November 1, 2011
Format: Hardcover
Penrose puts forth an old idea, that the end of our universe is the start of a new one, in a beautiful new way. That is, eventually the universe will lose track of the scale of space and time. So the whole giant universe turns into a Big Bang of about zero size!
Astronomers have recently found out that the expansion of the universe is accelerating, so it doesn't look like it will ever recollapse in the ordinary way. But in Penrose's theory, this apparently depressing reality is essential for a cyclic universe, because it means that the universe at the end of time is a spacelike surface, so its geometry can match the geometry of the Big Bang singularity in the next eon.
He offers a partial answer for an old puzzle: why did the Big Bang have such incredibly low entropy? The second law of thermodynamics tells us that entropy never decreases. The low entropy of the Big Bang defines the arrow of time, since entropy has been increasing since then, and life wouldn't be possible without a low-entropy state to start from. But where did the very low-entropy Big Bang come from?
Penrose's answer (or part of it) is that black holes destroy the information that goes into them (whether black holes destroy information is a big controversy in physics). That means that when the black hole eventually evaporates by Hawking radiation, the entropy that was in the matter that fell in has been permanently destroyed. I don't know if this can destroy enough entropy to explain the next very low entropy Big Bang.
Penrose doesn't believe the inflation theory, which is that space expanded incredibly rapidly right after the Big Bang.
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