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Monday, 29 July 2013
This book looks at time; why time seems to flow in one direction? Why can we not remember the future?

This is a more complex puzzle than it appears as the laws of physics are all reversable, they all work if you run them backwards - provided you make certain other changes. For example you could reverse time with the earth rotating around the sun, but you would need to also reverse the direction and angular momentum.

The author explains how the tendency of entropy to increase differentiates the future from the past. The future is more "chaotic". He does this by explaining statistical mechanics in a reality easy to explain way.

After this he asks why the Big Bang, the start of the universe, was such an ordered state and how we found ourselves to be here. The short answer is nobody knows so there is much speculation and he dips into quantum physics, black holes, whether we could build a time machine and multiple universes. The book becomes more speculative as it goes on.

The author ends with a model that involves our universe being a sort of bubble universe that broke away, it emerged as a flux in a larger empty space with just periodic fluctations(something called a De Sitter space which is basically empty space with just virtual particles popping in and out of existence). I read a similiar theory in Roger Penroses Cycles of Time, but I found that book far harder to read.

This is a good book, especially the first half. The author avoids the use of mathematics to describe his theories and so is forced to use analogies in the Stephen Hawkins style. I am sure this means leaving out some of the depth as analogies are rarely perfect. But most of us lack the ability to perform the mathematics, so this is probably a wise step especially when it comes to book sales. I found the second half grew a little more speculative, but it is a book I have read on more than one occasion. It seems a bit more advanced than other books that endless recount twin astronauts travelling at different speeds. And the range of material is quite vast.