On the Origin of Time - Thomas Hertog ****

Perhaps the most remarkable thing about Stephen Hawking's A Brief History of Time is that it says hardly anything about the nature of time. (The second most remarkable thing is how few of the people who bought it actually read it.) This book from Thomas Hertog, one of Hawking's former students, subtitled 'Stephen Hawking's final theory' very much follows the same line. Again it's far more about cosmology and black holes than it is about the nature of things temporal. And although I would say it's probably better written than the earlier book (and certainly far better than The Grand Design), this is a book that probably needs the reader to have a greater ability to take in technical details than A Brief History.

What I really like about this book is that it gives fascinating insights into the way that theoretical physics evolves. Hertog gives us an inside view of how Hawking and his colleagues worked - he is clearly in awe of Hawking to the point of hero-worship, but it remains enlightening. Things progress sometimes with major shifts of approach, sometimes by patching up flaws where an apparently beautiful theory doesn’t match reality. This was the case with the original big bang, and Hawking’s no boundary approach described here (where the universe begins without a beginning), which as originally formulated would have resulted in a universe bearing no resemblance to our own. Interestingly, Herzog doesn’t really explain why when Fred Hoyle did something similar for his steady state theory it was ignored - fashion makes a significant contribution to the success or otherwise of these kinds of highly speculative theories. 

In an attempt to get away from the idea of taking a 'god's eye' external view of the universe we are part of, we are told that Hawking et al developed a 'top down cosmology'. Here things start to feel very hand-waving - far more a matter of philosophy than physics. Herzog describes how they see the present influencing the past - but this feels very circular, along the lines of 'things are like they are now so we can ignore outcomes that don't lead to that, even if they seem very unlikely from the theory'… but it feels harder to justify the theory in the first place if this is the case. There are echoes too of Heinrich Päs' recent The One.

Broadly, there are two ways to write a popular science book about a complex theory. You can attempt to explain it as well as you can without the underlying mathematics, or you can not explain it at all, but just state what the theory does without looking under the hood. Each approach has its problems. The explanations of those trying to put forward a maths-based theory without equations inevitably fall short of what the theory is really about. And the 'never explain' approach, which is used by Hertog, can easily present as fact what is in reality highly speculative and quite likely impossible to prove through experiment or observation. Reading this book, for example, you would not suspect that string theory or the existence of dark matter particles were in any way contentious. 

Depending on your approach to such things, this is either fascinating, leading edge theoretical physics or something more akin to theology - ascientific rather than science in the traditional sense. You pays your money and you takes your choice. Personally, the 'science' leaves me cold, but the insider view of the way highly speculative theoretical physics was developed by Hawking and colleagues made this an unmissable read.

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Review by Brian Clegg - See all Brian's online articles or subscribe to a weekly email free here