Friday, September 23, 2022

A Brief History of Black Holes: And Why Nearly Everything You Know About Them is Wrong, by Becky Smethurst (author, narrator)

Macmillan, September 2022

Becky Smethurst is an astrophysicist with a great love of black holes, and a desire to share her enthusiasm for them with the rest of us.

She tries to cover, concisely but with absorbing detail, everything important about them, starting with the important facts that they're not black, and they're not holes. They're not black because an active black hole has an accretion disk which generates a great deal of light and other radiation. They're not holes, because that absolute darkness inside the accretion disk isn't a void. It's an immensely dense accumulation of matter, usually many, many times the mass of a star--certainly our star. Smethurst compares  black holes to mountains, which I find not personally satisfying, but entirely reasonable.

More unexpected is her comparison of black holes to sofas; things get swallowed up and lost in them, never to be recovered.

But this isn't just a book of what we should compare black holes to (she says she prefers "dark stars," but admits that's a lost chance), but their history, formation, development, and possible end.

The formation of stellar mass black holes is, apparently, pretty well understood. If  a collapsing star at the end of its life is massive enough, when it collapses, it will collapse not into a neutron star, but a black hole. The problem is supermassive spring holes. There simply doesn't appear to have been enough time since the birth of the universe for supermassive black holes to form. And yet, we're now reasonably certain that every galaxy has a supermassive black hole at its center. Where do they come from?

Perhaps from the collision of smaller black holes? It's one of the things Smethurst looks at.

She also discusses the first detection of gravity waves, the first picture of a black hole, and the fact that black holes will, eventually, evaporate. They'll evaporate very slowly, though, and only after they've stopped growing, and it's not at all clear that the largest black holes will have time to evaporate before the end of the universe, depending on what sort of end the universe is going to have. However, we do still have a shot at finding a primordial black hole, very small in size, which might have had time to evaporate. If we detect that, we may be able to detect Hawking radiation, which we're unlikely to be around to detect from any supermassive black hole.

There's lots of fascinating information in this book, and Smethurst has both an engaging enthusiasm, and a lively sense of humor. She also has a good reading voice, which overall makes this a wonderful book to listen to. 


I bought this audiobook.

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