By Lee Smolin
Houghton Mifflin Harcourt (April 23, 2013)
This is a difficult review for me to write because I disagree with pretty much everything in Lee’s new book “Time Reborn,” except possibly the page numbers. To begin with there is no “Crisis in Physics” as the subtitle suggests. But then I’ve learned not to blame authors for title and subtitles.
Oddly enough however, I enjoyed reading the book. Not despite, but because I had something to complain about on every page. It made me question my opinions, and though I came out holding on to them, I learned quite something on the way.
In “Time Reborn” Lee takes on the seemingly puzzling fact that mathematical truth is eternal and timeless, while the world that physicists are trying to describe with that mathematics isn’t. The role of time in contemporary physics is an interesting topic, and gives opportunity to explain our present understanding of space and time, from Newton over Special and General Relativity to modern Cosmology, Quantum Mechanics and all the way to existing approaches to Quantum Gravity.
Lee argues that our present procedures must fail when we attempt to apply them to describe the whole universe. They fail because we’re presently treating the passing of time as emergent, but as emergent in a fundamentally timeless universe. Only if we abandon the conviction, held by the vast majority of physicists, that this is the correct procedure, then can we understand the fundamental nature of reality – and with it quantum gravity of course. Lee further summarizes a few recent developments that treat time as real, though the picture he presents remains incoherent, some loosely connected, maybe promising, recent ideas that you can find on the arXiv and I don’t want to promote here.
More interesting for me is that Lee doesn’t stop at quantum gravity, which for most people on the planet arguably does not rank very high among the pressing problems. Thinking about nature as fundamentally timeless, Lee argues, is cause of very worldly problems that we can only overcome if we believe that we ourselves are able to create the future:
“We need to see everything in nature, including ourselves and our technologies, as time-bound and part of a larger, ever evolving system. A world without time is a world with a fixed set of possibilities that cannot be transcended. If, on the other hand, time is real and everything is subject to it, then there is no fixed set of possibilities and no obstacle to the invention of genuinely novel ideas and solutions to it.”I’ll leave my objections to Lee’s arguments for some other time. For now, let me just say that I explained in this earlier post that a deterministic time evolution doesn’t relieve us from making decisions, and it doesn’t prevent “genuinely novel ideas” in any sensible definition of the phrase.
In summary: Lee’s book is very thought provoking and it takes the reader on a trip through the most fundamental questions about nature. The book is well written and nicely embedded in the long history of mankind’s wonderment about the passing of time and the circle of life. You will almost certainly enjoy this book if you want to know what contemporary physics has to say, and not to say, about the nature of time. You will almost certainly hate this book if you're a string theorist, but then you already knew that.