What is time? Did it have a beginning? What makes it appear to flow? Why is there a directionality or 'arrow' of time, and can it ever be reversed? It time travel possible? And might the universe be older than we thought?

The puzzles and paradoxes of time have dazzled the world's finest thinkers and throughout the ages philosophers have wrestled with the tensions between time and eternity, linear time and cyclicity, being and becoming. When Einstein formulated his theory of relativity early this century, it brought about a revolution in our understanding of time, yet also presented a new set of mysteries. Einstein's time can be warped, leading to bizarre possibilities such as black holes and time travel, while making nonsense of our perception of a 'now' and a division of time into past, present and future. In relation to quantum physics, time takes on even stranger aspects.

In this, his latest book, acclaimed physicist and writer Paul Davies confronts the tough questions about time, including the weird relationship between physical time and our psychological perception of it. He gives straightforward descriptions of topics such as the theory of relativity, time dilation and Hawking's 'imaginary time'. Davies concludes that despite decades of progress in unravelling the mysteries of time, the revolution begun by Einstein remains tantalizingly incomplete.