Cycles of Time: An Extraordinary New View of the Universe

Cycles of Time: An Extraordinary New View of the Universe

2.8 5
by Roger Penrose

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A groundbreaking book providing a new take on three of cosmology’s most profound questions: What, if anything, came before the Big Bang? What is the source of order in our universe? What is the universe’s ultimate future?

Current understanding of our universe dictates that all matter will eventually thin out to zero density, with huge black… See more details below


A groundbreaking book providing a new take on three of cosmology’s most profound questions: What, if anything, came before the Big Bang? What is the source of order in our universe? What is the universe’s ultimate future?

Current understanding of our universe dictates that all matter will eventually thin out to zero density, with huge black holes finally evaporating away into massless energy. Roger Penrose—one of the most innovative mathematicians of our time—turns around this predominant picture of the universe’s “heat death,” arguing how the expected ultimate fate of our accelerating, expanding universe can actually be reinterpreted as the “Big Bang” of a new one.

Along the way to this remarkable cosmological picture, Penrose sheds new light on basic principles that underlie the behavior of our universe, describing various standard and nonstandard cosmological models, the fundamental role of the cosmic microwave background, and the key status of black holes.

Intellectually thrilling and accessible, Cycles of Time is another essential guide to the universe from one of our preeminent thinkers.

From the Hardcover edition.

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Editorial Reviews

Publishers Weekly
Where did the universe come from, why is it the way it is, and what is its ultimate fate? Eminent Oxford mathematician Penrose (The Road to Reality) finds "a profound oddness underlying the Second Law of Thermodynamics and the very nature of the Big Bang" theory of the universe’s origins. In response, he proposes tweaking the old theory to answer these questions. Armed with some fairly hairy math (logarithms, tensor calculus), Penrose argues that increasing entropy, a natural consequence of the Big Bang, supports space-time models in which an increasing number of hungry black holes should yield matter-spewing white holes as well. Instead, we have an entirely too uniform universe more suited to a "conformal cyclic cosmology" where black holes grow and eventually "pop," yielding a fresh new Big Bang in an infinite "succession of aeons." Although Penrose makes provocative arguments for his challenging new theory (relegating his denser mathematical explorations to the appendixes), readers will need a solid grounding in college-level math and physics to wade through this intriguing work. B&w illus. (May)
From the Publisher
“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

Kirkus Reviews

Award-winning physicist Penrose (The Road to Reality: A Complete Guide to the Laws of the Universe, 2006, etc.) challenges current theoretical models of the Big Bang.

The author reprises the discovery of the Doppler shift by Edwin Hubble, which established the fact that our universe was expanding at an increasing rate, and he explains how this allowed astronomers to extrapolate backward to a moment approximately 14 billion years ago "when the matter of the universe would have to have been all together at its starting point." In 1964, the observation of the cosmic background radiation allowed scientists to elaborate a detailed model of the evolution of the universe, beginning in the fraction of a second after an explosive Big Bang. Penrose points out that this picture is problematic because it appears to violate the Second Law of Thermodynamics. Except for minor violations, entropy—a measure of disorder—always increases over time. At the instant of the Big Bang, entropy would be extremely high, then energy would be decreased as the universe entered its expansionary phase, elementary particles formed and gravity kicked in. The author suggests that what is called the Big Bang was not an explosion but a transition point from an earlier cycle of the universe. To resolve this theoretical conundrum, he suggests that in the far-distant future, stars and galaxies will be compressed into tremendously massive black holes that will clump together and ultimately disappear leaving only cosmic radiation in their wake, after which a new expansionary cycle will begin.

A controversial but intriguing theory that will challenge readers but is well worth the effort.

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Product Details

Knopf Doubleday Publishing Group
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Random House
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Read an Excerpt


One of the deepest mysteries of our universe is the puzzle of whence it came.
When I entered Cambridge University as a mathematics graduate student, in the early 1950s, a fascinating cosmological theory was in the ascendant, known as the steady-state model. According to this scheme, the universe had no beginning, and it remained more-or-less the same, overall, for all time. The steady-state universe was able to achieve this, despite its expansion, because the continual depletion of material arising from the universe’s expansion is taken to be compensated by the continual creation of new material, in the form of an extremely diffuse hydrogen gas. My friend and mentor at Cambridge, the cosmologist Dennis Sciama, from whom I learnt the thrill of so much new physics, was at that time a strong proponent of steady-state cosmology, and he impressed upon me the beauty and power of that remarkable scheme of things.
Yet this theory has not stood the test of time. About 10 years after I had first entered Cambridge, and had become well acquainted with the theory, Arno Penzias and Robert Wilson discovered, to their own surprise, an all-pervading electromagnetic radiation, coming in from all directions, now referred to as the cosmic microwave background or CMB. This was soon identified, by Robert Dicke, as a predicted implication of the ‘flash’ of a Big-Bang origin to the universe, now presumed to have taken place some 14 thousand million years ago—an event that had been first seriously envisaged by Monsignor Georges Lemaître in 1927, as an implication of his work on Einstein’s 1915 equations of general relativity and early observational indications of an expansion of the universe. With great courage and scientific honesty (when the CMB data became better established), Dennis Sciama publicly repudiated his earlier views and strongly supported the idea of the Big Bang origin to the universe from then on.
Since that time, cosmology has matured from a speculative pursuit into an exact science, and intense analysis of the CMB—coming from highly detailed data, generated by numerous superb experiments—has formed a major part of this revolution. However, many mysteries remain, and much speculation continues to be part of this endeavour. In this book, I provide descriptions not only of the main models of classical relativistic cosmology but also of various developments and puzzling issues that have arisen since then. Most particularly, there is a profound oddness underlying the Second Law of thermodynamics and the very nature of the Big Bang. In relation to this, I am putting forward a body of speculation of my own, which brings together many strands of different aspects of the universe we know.
My own unorthodox approach dates from the summer of 2005, though much of the detail is more recent. This account goes seriously into some of the geometry, but I have refrained from including, in the main body of the text, anything serious in the way of equations or other technicalities, all these being banished to the Appendices. The experts, only, are referred to those parts of the book. The scheme that I am now arguing for here is indeed unorthodox, yet it is based on geometrical and physical ideas which are very soundly based. Although something entirely different, this proposal turns out to have strong echoes of the old steady-state model!
I wonder what Dennis Sciama would have made of it.

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