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Gravitational Waves - Brian Clegg ****

The message of this book is summed up in its subtitle: 'How Einstein’s spacetime ripples reveal the secrets of the universe.' Gravitational waves really do reveal secrets – astronomical phenomena that can’t be observed any other way. The Einstein connection comes via general relativity – his alternative to Newton’s theory of gravity which is, notoriously, almost indistinguishable from it for most practical purposes. There are a few situations where the two theories make slightly different predictions, and in these cases general relativity comes out on top. When the Laser Interferometer Gravitational Wave Observatory (LIGO) reported the detection of gravitational waves in February 2016, most journalists treated it as just another of these academic “ticks in the box” for Einstein.

 That’s underselling one of the most exciting breakthroughs in modern science – and this book aims to put the record straight. According to Brian Clegg, the LIGO announcement 'signalled the beginning of the biggest change to astronomy since the introduction of telescopes.' I’m not sure I’d go quite that far – the radio astronomy revolution of the 20th century was probably bigger – but gravitational waves may end up a close second. In principle they offer a means of directly observing hitherto purely theoretical concepts – from black holes and dark matter to the Big Bang itself.

When that first LIGO detection occurred, it wasn’t just a sharp spike above the noise background that people assumed had to be a gravitational wave (which is how I’d pictured it, based on media reports, before I read this book). It was a structured signal that, brief though it was, contained a huge amount of meaningful information. When properly interpreted, it told researchers not just  that the signal came from the merger of two black holes, but that they were located about 1.4 billion light years away, and had masses approximately 36 and 29 times that of the Sun. That’s not just 'confirming a theory' – it’s doing proper observational astronomy.

 This is relatively short book, but it covers most of what an interested, non-specialist reader is going to want to know. It succinctly explains what gravitational waves are, how their existence was predicted, and methods by which they might be detected. It describes the design and construction of LIGO, the detections that have been made with it, and their physical interpretation. And there’s a substantial concluding chapter on what the future holds for gravitational wave astronomy.

 With such a tightly packed book, it’s inevitable that some topics get covered in depth at the expense of others. For my taste, there was rather too much about the statistical analysis of the data to remove false alarms, and not enough about actually interpreting the data in terms of the astrophysical processes that produced it. But issues like that aren’t really a problem now that we have the internet. If you finish a book and your head is buzzing with unanswered questions, at least you know what to type into a Google search.


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Review by Andrew May
Please note, this title is written by the editor of the Popular Science website. Our review is still an honest opinion – and we could hardly omit the book – but do want to make the connection clear.

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