This is a book about the meaning of time, what it is, when it has started, how it flows and where to. If you ever wondered about the puzzles and paradoxes of time, if you ever wanted to learn more about what Einstein's relativity implies about time itself, this is a book you will not want to miss.
Davies covers most of the questions about time; I found interesting how he explains the rather weird relationship between real time and our mental notion of it. The weirdness of bizarre possibilities should be enough to confuse anyone thinking about it for the first time; the way time relates to quantum physics, being sometimes even stranger to understand.
Black holes, the warping of space-time, theories about time travel, and the notion of "now": the division of past, present and future. From the inevitable "what existed before the Big Bang" to the Hartle Hawking theory, Wormholes, time dilation, etc, much is covered about time. Here are some of the subjects you will be able to read about:
1.Tachyons: Davies wonders if Tachyons can be ruled out. The special theory of relativity has been tested to unprecedented accuracy, yet tachyons are a problem. Allowed by the theory, they bring with them all sorts of unpalatable properties.
2.Black holes: Could there be really an end to time-a singularity- and the centre of all black holes? Can they form tunnels to other universes, or can we use them like wormholes that thread back into our universe? What happens to matter falling in them?
3.Time Travel: Just a fantasy? The investigation of exotic space-times that seem to permit travel into the past will, according to Davies, remains an active field of research, but there are no realistic time-travel scenarios known. But as with Tachyons, the absence of a no-go proof forces science to keep it on the agenda, along with the usual paradoxes, of course. :-)
4.Quantum questions: Davies spends some pages describing the wonderland of weird and perplexing temporal teasers in the quantum domain. The way relativity of time fits uneasily into the quantum picture of a world where the collapse associated with measurements occurs abruptly at specific moments. The measurements of time itself are fraught with problems, since all clocks are physical objects afflicted by quantum fuzziness.
5.The Origin of Time: You'll also be able to read about the usual topic of how time originated, with all sorts of questions concerning causality, God and eternity.
The Age of the Universe: Davies spends some time on the measurements of the expansion rate of the universe, which combined with realistic assumptions about dark matter lead to the absurd conclusion that there are objects in space older than the universe itself. What's going on anyway?
These are just some of the main issues. This title is definitely only for those who have questioned time. Davies book is a bit dry sometimes, and can probably bore the reader who is expecting more impact. Some parts like the explanation of the quantum eraser dreamed up by physicist Marlan Scully might be a bit challenging for those with no background in the subject, but in general, the whole book is very readable and clear. Little math is required, if you know how to square a negative (imaginary number), you probably know enough to keep up, almost no math is presented. And to help, we have Davies sense of humour; while it might annoy some readers, I thought it was helping the book to flow better. It all depends on who's reading. :-) The book has good recommended Bibliography, and a decent Index. Unfortunately, there is no glossary.
If I had to summarize the book in a paragraph, surprisingly, I would perhaps just write that we probably don't know much. Despite all the progress of the past decades, Time is still a mystery, and the revolution that Einstein started is still very incomplete. His word on the subject won't be the last.
Unfortunately, this book ends up raising more questions than those it answers. Not Davies fault, it's really the subject itself. :-)
Very interesting work for the layman who is curious about time.
