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Monday, 29 March 2021

Niall Deacon: Twenty Worlds

Niall Deacon:
Twenty Worlds: The Extraordinary Story of Planets Around Other Stars (1*, but possibly 5* for some)
 
I have a backlog of books to write up. 
 
Twenty Worlds is a clear account of difficult concepts explained by means of well-chosen analogies to make them accessible to non-specialists. Enthusiasts of the undoubtedly brilliant scientific reasoning behind astronomical discovery might well give it five stars (there is, after all, no shortage in the universe) but I couldn’t finish it. Unjustly, under my system, that scores only one.

It is a personal starring system, as personal as the giving and receiving of books. You express how much you like a particular book – namely Andrew Cohen and Brian Cox’s The Planets, reviewed previously in November – and receive others perceived to be similar. This isn’t. My expression should have been more specific. What it does is to select twenty planets orbiting distant stars and explain the methods by which they were discovered, and what they tell us. They have names like 51 Peg b. There is little about what these worlds might be like.

There are some interesting ideas. For example, how can we know there are planets around distant stars if our telescopes cannot see them? It turns out, in a sense, that when a planet orbits a star, the star also orbits the planet. It is a bit like a seesaw with you or me on one end and an elephant on the other. It would balance, but the balance point would be very close to the elephant. Strictly, Jupiter does not orbit the sun, it orbits a balance point just above the sun’s surface. The sun orbits the same balance point. Viewed from a distance, Jupiter’s orbit makes the sun appear to wobble towards and away, and from side to side. The earth makes it wobble too, but almost undetectably because the earth is much smaller and lighter than Jupiter. The earth-sun balance point is inside the sun close to its centre. This phenomenon reveals only huge, heavy planets.

But how do we know a star wobbles when we cannot even see that? Another analogy explains it: the Doppler Effect, i.e. the way the sound of a fire engine changes from a higher to a lower pitch as it passes by. This happens because, when the fire engine is moving towards you, the sound waves are closer together than when it is moving away (the waves still travel at the same speed but are emitted from increasingly closer points and then increasingly distant points). The same happens with light. So, if the orbit of a planet causes a distant star to wobble repeatedly towards and away from us, the frequency of the light keeps changing. The spectrum of light from a star contains dark lines where some frequencies have been filtered out by local conditions, and these dark lines will oscillate towards one end and then the other end of the spectrum. That is what we are able to detect.

It gets cleverer, such as detecting planets by variations in the brightness of stars as planets move in front of them, and analysing the spectrum of light emitted by a planet to determine the constituents of its atmosphere. It is even possible to photograph some of these planets: the book includes a picture of four white spots around star number HR 8799 and discusses the imaging techniques that make this possible. 
 
And so it continues. In essence, this is astrophysics without the mathematics. I gave up. Lazy, I know, but just like in a neutron star, electron degeneracy pressure was unable to stop my brain from collapsing in upon itself and pulsing out radio waves.

If you find this fascinating, this may be the book for you.


Key to star ratings: 5*** wonderful and hope to read again, 5* wonderful, 4* enjoyed it a lot and would recommend, 3* enjoyable/interesting, 2* didn't enjoy, 1* gave up.

19 comments:

  1. I could not read such a book so good on you for getting as far as you did. As for 51 Peg b, I hereby propose that it should be renamed Planet Tasker. As such it must either be a place of unparalleled beauty or a lifeless lump of rock swathed in noxious gases. You decide.

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    1. Thank you for reading this review. It was a test. The result: you do not suffer from electron degeneracy pressure.

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  2. Umm sorry. You lost me by the first few paragraphs.

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  3. It sounds like a book I might skim over but not read word for word. I am fascinated by astronomy but not good with the details. You should get an "A" for giving it a good try!

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    1. When you get a book as a gift you feel obliged to try, but it felt too much like a difficult school book that needs a lot of effort.

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  4. I'd like a book that explains why the full moon sometimes looks so much bigger. But then again I've managed without knowing for over 70 years so.... But then again I've got time now so.....
    Twenty Worlds is a bit above my requirements. Thanks for the rating.

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    1. Thanks for commenting. It was well beyond any of my requirements, but I did enjoy Andrew Cohen and Brian Cox's The Planets and the associated TV series (see https://www.taskerdunham.com/2020/11/the-planets.html)

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  5. Potty, just look up the term apogee and perigee and the light bulb may go on. The moon doesn’t orbit the earth in a perfect circle, it is more of an oval route. At it’s closest to us the moon is about 10% closer to the earth than at its farthest from us. That mt is why some full moons look bigger than others.

    Tasker, my theory is that electron degeneracy pressure is what causes flatulence. I devised my theory after reading this post. Before that, I had never heard of electron degeneracy pressure. The field is called arsetrophysics.

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    1. You cannot simply say that without the mathematical equations to justify it. Is it something to do with 'as p increases' ?

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  6. You get 5 stars for that summary. I enjoyed that bit at least. Our Mr B likes this sort of stuff, but maybe we will start with the Brian Cox book - Mr B doesn't have a long attention span.

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    1. The Cohen-Cox book is all you need. It's as good as the tv series that goes with it, and complements rather than duplicates. See: https://www.taskerdunham.com/2020/11/the-planets.html

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  7. I'm glad there are people out there who are doing this kind of work, but I agree -- I don't need to know too much about it!

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    1. Expertise is the ability to bore everyone to death about your specialist subject.

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  8. Maybe instead of complaining that this book was bought for you when all you had expressed an interest in was the Cox/Cohen book, you could instead answer the question 'what do you want for you birthday?' with an actual answer. In any case, you didn't actually ask for the Cox/Cohen book, you simply asked for astronomy related books which this clearly is.

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