Cycles of Time: An Extraordinary New View of the Universe

  • Roger Penrose
  • Knopf
  • 258 pp.

Respected physicist Roger Penrose theorizes on the beginning and end of our universe.

Reviewed by Y.S. Fing

This is the way the world ends Not with a bang, but a whimper

It seems as though T.S. Eliot was right after all, except Roger Penrose describes the end of the universe more prosaically, as a “pop.” According to his abstruse calculations, the entropy of the universe at the end of its existence (several billion years hence) will be so tremendous that there will be little energy for anything but an anticlimactic uncorking. Not to worry! The math (if we dare call it that) indicates there will be another universe.

If you like your cosmological physics served up a lá Carl Sagan, that is, with a minimum of mathematical symbolism and a maximum of literary metaphor, this book is not for you. However, if you are interested in an intellectual thrill ride, look no further. From the beginning, of both the Big Bang and the book, the momentum churns forward. 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.

The blurb on the back of the book says that Penrose is meditating upon “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 fate?” Any reader with the gumption to forge ahead through the infinite intricacies of the math (a word that simply fails to identify calculations my computer can’t even re-create) will positively burble with excitement about finding answers to these questions. It’s a cosmological page-turner!

But let’s start with the foundation. “The Second Law of thermodynamics is not an equality, but an inequality ... the entropy of an isolated system ... is greater at later times than it was at earlier times.” There is no escaping this, and it dominates every consideration going forward. But Penrose begins at small scale and lithely guides the reader to galactic and universal scales, so we can see “the central mystery that underlies the profound usefulness of this remarkable physical notion” in actuality.

No consideration of the universe would be complete, or trustworthy, if it didn’t attend to the questions and problems of Time. So Penrose asks, “Why is the past different?” His answer is no real surprise: “teleology is perfectly acceptable if we are looking towards the past, but it is not a feature of our experience that it apply towards the future.” In the very next sentence he turns to “the very origin of our universe ... [as] one of particularly small entropy.” And “the key issue is indeed the specialness of the Big Bang, and the extraordinary minuteness ... of this special initial state.”

In search of understanding “this special initial state,” the reader is transported backward in time 13 billion years to the moments immediately before the Big Bang (in the symbol ϐ-), and outward just past the edge of infinity (I+), slightly beyond the cosmic microwave background that surrounds the known universe like an electric eggshell. Penrose ultimately asks, “Could it be that our I+ and ϐ- are one and the same?” It’s impossible to describe the pleasure of such a consideration, that the universe is some gorgeously enormous mobius strip spinning around in space, a unity of past and future. Unfortunately, with Penrose, it’s just a tease. “I am not proposing this I+/ϐ- identification.” Awww ...

Spoiler alert! Penrose does offer a variation on this theme: “I am suggesting ... that there is a physically real region of space-time prior to ϐ- that is the remote future of some previous universe phase, and that there is also a physically real universe phase that extends beyond our I+ to become a big bang for a new universe.” Penrose calls this “conformal cyclic cosmology.”

It’s not as wondrous a notion as Lee Smolin’s multiple universes, which Penrose sketches out both respectfully and dismissively, but it does adhere to the foundational ideas of entropy accumulation and Newton’s Second Law. Penrose also considers and rejects string theory, extra-space dimensions and Steinhardt’s and Turok’s “collision of D-branes” because, in his words, “None explicitly addresses the question of suppressing gravitational degrees of freedom in the Big Bang, this actually being the key to the origin of the Second Law.”

There’s no science fiction here, no imaginative filling in the gaps. There is, however, a very strong scientific case for expanding the boundaries of our thinking. The remainder of the book discusses how we might gather more evidence for conformal cyclic cosmology, particularly from the cosmic microwave background, and how Penrose is doing just that. We can certainly look forward to those results.

It’s too bad T.S. Eliot isn’t around to read this book. He may have had to rewrite his poetry:

This is the way the world ends With the beginning of a new world    


Y.S. Fing, an instructor of English at a community college in the D.C. area, is the author of such unpublished works as “Socialize Yourself: A Teacher’s and Student’s Guide to College-Level Composition” and “Event Horizons: Aphorisms on the Life of D. Selby Fing” (

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