Wednesday, 11 January 2017

Astrophysics: A Very Short Introduction - James Binney ****

For many readers, the very word ‘astrophysics’ is a daunting one. That’s ironic, because astronomy is one of the most popular of popular-science subjects, and it’s almost 100% applied physics. You can’t understand planetary orbits without invoking the theory of gravity; you can’t understand how stars shine without invoking nuclear fusion; you can’t understand a galaxy’s spiral arms without invoking the physics of waves. Yet apart from a few exotic topics like black holes and dark matter, the crucial role played by physics is all too often glossed over in popular astronomy books.

So this ‘Very Short Introduction’ is a welcome antidote to all that. It would be ideal for a reader who is already keen on astronomy, and has some basic school-level physics, who wants to see how the two fit together. Most amateur astronomers will have heard of ‘main sequence stars’ and the Hertzsprung–Russell diagram, but this book shows you how the mysteries of stellar evolution all have their roots in solid physical principles like gravitation, nuclear fusion, heat convection and black-body radiation. 

Another thing that comes across is that, although the universe is very big, there really aren’t that many laws of physics. So the same physics gets used over and over at different scales – with, for example, the same principle of ‘conservation of angular momentum’ shaping the structure of the solar system, black hole accretion discs and entire galaxies. Other areas of physics, which may not be very prominent here on Earth, really come into their own in an astronomical context. This applies most obviously to relativity – both the special and general theories – which can explain a whole range of phenomena from the stability of the solar system to cosmic rays and gravitational lenses.

A short, wide-ranging book like this is always going to lack depth, but that’s not a bad thing with a potentially heavy subject like this one – especially when, as in this case, the author is a professor of astrophysics. Fortunately James Binney doesn’t try to blind readers with science, but he doesn’t talk down to them either. That’s probably a good thing, too, since I suspect the very title of the book is going to have a self-selection effect on its readership. The sort of people who buy this book won’t want to be talked down to.

A few months ago it was mentioned to me that these OUP ‘Very Short Introduction’ books tend to be dry summaries rather than narrative-driven. That’s pretty much the case here. Essentially the author presents a long list of facts, rather than posing a series of rhetorical questions (of the sort the reader might have) and then answering them, or showing how they were tackled in a historical context. I think I might have liked that better, but I can’t mark the book down on that account because it’s obvious that it is simply sticking to the house style for the series. Even so, it’s an enjoyably easy read, and a long way from being a stodgy textbook – I mean, what textbook would tell you the Galaxy contains ‘zillions of dark-matter particles’?

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Review by Andrew May

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