Cycles of Time: An Extraordinary New View of the Universe

Sir Roger Penrose, Emeritus Rouse Ball Professor of Mathematics in the University of Oxford, has written another marvellous book. Once again, he manages to discuss topics in modern physics in a way that will educate and enthuse the intelligent layman while retaining enough substance to engage the more sophisticated reader. This time, the topic is (in Penrose's words) "an extraordinary new view of the universe," a theory that he calls "Conformal Cyclic Cosmology (CCC)." As in his previous efforts, Penrose's success derives from his ability to actually teach some fundamental concepts before entering the more speculative domains. Hence, the first third of the book is devoted to an informative explanation of entropy and the second law of thermodynamics, and their place in describing the evolution of the universe. In the second third, Penrose emphasises the unique character of the low entropy state of the early universe before gravitational degrees of freedom had been activated. In this part, he also introduces the notion of "strict conformal diagrams" that provide a graphical description of the rather involved maths. The final portion of the book is devoted to an intriguing summary of CCC. This is based largely on Penrose's earlier introduction of the Weyl Curvature Hypothesis that requires the Weyl curvature tensor to vanish at the conformal hypersurface of the Big Bang. CCC proposes that beyond the distant future of the current universe lies another Big Bang and, conversely, before the Big Bang of the current universe lies the future infinity of a previous one, with space-time being merged at the boundary of each "aeon" by a conformal rescaling of the metric tensor. How this is reconciled with the continuing increase in entropy, consistent with the second law, is quite interesting and I won't spoil the surprise by revealing it here. The book concludes with a mathematical appendix that more fully describes some of the basic notions. This, in conjunction with the notes and cited references, will help the student on his way. To be sure, this book will challenge even the brightest and most motivated layman. Understanding just the elementary exposition of the basic ideas requires some serious thinking. And Penrose cannot help dropping terms like "tensor field" and "tangent space" that will baffle the novice. There are even a few equations. In addition to thinking, one should be prepared to consult additional references and ask many questions. But, after all, that is what learning is all about. Enthusiastically recommended!

The Great Roger Penrose deserves 5 stars just for the fabulous diagrams. I have a mathematics degree from a long time ago so I am not scared of equations and this book has plenty of them, along with all the physics you could want, and also quite a bit of philosophical conjecture. I am wondering whether the aeon we are currently living in regresses all the way back to the first aeon. But that is probably a chicken or egg problem. Our current aeon will last a google number of years, so I don't really care much what happens after that. Our current Universe is 13.7 billion years old, which is the blink of an eye in aeon time. Our Sun will die out in 5 billion years or so, which means we would have to move to Plant B, C, D, all to way up to Z for humanity to continue to survive. CCC requires that rest mass will decrease over time, which is hard to believe but maybe the improbability drive of the Hitch Hikers guide to the Universe will kick in. Personally I think that Professor Penrose believes in his CCC theory due to some wishful/sentimental thinking so that life has the possibility of continuing in some form forever in succeeding aeons. I would not discount the possibility that some time in future generations the physics of spacetime, and quantum field theory evolves and that there might be ways to modify the current dark energy source that is ripping spacetime further and further apart due to the cosmological constant. Maybe the constant itself can be changed, who knows certainly not I. Live Long and Prosper!

Four Stars: I gave it this because I still have faith that Penrose offers a way out of the singularity of the Big Bang. However ... PRINT: I have tried twice to read this and failed. It is NOT for the lay reader. It is perhaps challenging for a trained physicist/mathematician. I am still trying to absorb something anyway. AUDIO: My second attempt to "read" the book was as an MP3 download. Impossible! Whatever the merits of the book, and I have tried 4 times now to read it since I think Penrose is surely onto something important, to listen to it is quite impossible unless one already understands everything already. There are numerous equations and numerous drawings and numerous cross-references that are utterly impossible to follow w/o SEEING the pages. An audio version? Ridiculous! KINDLE: this version is severely crippled due to the fact that Kindle Reader does not SCALE anything except text. Damn. It is so annoying to have to double-click the graphics in order to enlarge them enough to read them. It is extremely annoying that the special characters embedded in the text, of which there are MANY!, are not scalable in Kindle Reader. When is Kindle going to handle EVERY aspect of the text as fully scalable? This is unacceptable. Of course, Kindle allows highlighting and linking which is good. But this particular book is EXTREMELY heavily laden with graphics and special characters such that multiple times on many many pages these features are totally out of proportion to the main text.

A great book if you like physics. Well written and easy to understand...

Wer die Grenzen dessen, was der Mensch im Mikro- und Makrokosmos heute weiss und wer erkennen will, dass wir erst am Anfang der "Erkenntnis" stehen, der sollte dieses neue Standardwerk der Physik lesen.Mathematik ist dafür nicht zwingend erforderlich. Es ist ein weiterer Beweis für das "anthropische Prinzip", das die theoretische Physik seit einiger Zeit einheitlich postuliert!!

宇宙をエントロピー増大の法則と一般相対性原理が成り立つように論じている。なぜ、宇宙の始まりでエントロピーが小さいのか？まず、エントロピーを相空間におけるcoarse-grainingの体積の増大として捉える。ペンローズは情報がブラックホールで失われるという立場をとり、ブラックホールではエントロピーの相空間の体積が減少するという。そして、ブラックホールの終焉はホワイトホールとなり宇宙は循環するのだという。証拠として「プレ」ビックバンのブラックホール衝突の痕跡が宇宙マイクロ波背景放射の中に観測されるはずだという。ペンローズは量子重力をstringではなく4次元時空の性質で説明する立場をとり、string theoryにおける余剰次元を必要としない。インフレーションも必要としない。CCC（コンフォーマル サイクリック コスモロジー）はランダムなマルチバースでもない。ペンローズは宇宙の始まりの前から未来までエントロピーの法則と時空の性質と量子力学で説明しようとする。時間はstring theoryにおけるパラメーターの置き換えではなくエントロピーの増大の方向と関連させている。string theoryにはほとんど触れていないが、時代の流れも汲み取りワイルテンソルとアインシュタインテンソルについてデュアリティーのような解釈もなされている。暗黒物質や暗黒エネルギー、宇宙定数、宇宙マイクロ波背景放射などを2008年の時点での最新の知見から論じている。時空を光円錐の集まりで表現したり、アインシュタイン方程式の解をダイアグラムで表すなど図解もセンスに満ち溢れている。

I'm not going to lie and say this book is easy, because it really isn't. While it's entertaining in the most part and even funny in places, in other places, it's very dense, and while Penrose tries to keep the book as close to layman's terms as he can, there are parts which require a pretty good grasp of advanced mathematics. The ideas put forward in the book are extremely interesting, and it's a very rewarding book once you get your head around the detachment caused by having to think about real-world events in terms of their mathematical analogues. There were times when I had to go over passages more than once, but it's worth sticking with it. An excellent read and a very big idea indeed.

a very easy technical book for everyone. We can also profit from his platonic view of what is behind pure physics