Without gravity there would be no solid matter in the universe, just energy and particles floating around, and without stars there would be nothing but hydrogen, helium and lithium, elements formed shortly after the Big Bang. Many of the heavy elements we find in the universe today are forged within stars like our sun, Sol. I've always regarded stars with some fascination, they are the alchemists of the universe and, in the case of Sol, the source of the energy that life has needed to evolve and flourish on Earth. Really, if humans really must have gods, its the creative forges that are the stars. 15 Million Degrees is a thorough overview of everything you need to know about our Sun and more, including the pioneer scientists who slowly built knowledge about Sol, not just in the core where fusion occurs, but also in the other layers of the Sun, all of which have their own characteristics and complexities. Without going into detail (it would be best to read this book), the Sun is an extremely complex object with features such as the photosphere, the corona, the heliosphere and the magnetosphere. There's convection zones, sunspots, plasma, the radiation zone, and my favourite, the flux ropes, which are magnetic field lines that have been twisted by the intense movements of the Sun's rotation, trapping the plasma and taking it on a wild ride.
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| Just some of the Sun's structural features |
Professor Green is an engaging writer, conveying not only her own enthusiasm and research about Sol, but also everything that is known about the Sun and what is theorised but not proven as yet. The chapter about sunspots is particularly fascinating. Sunspots can be readily observed and it turns out that they reveal a great deal about how the Sun functions, including the Sun's eleven year cycle of activity and how it behaves magnetically. There are many facts about the Sun that would astound the average person, for example, the heliosphere helps to shield the Earth from interstellar radiation, which would otherwise damage DNA and possibly make life untenable; essentially we live inside the atmosphere of the Sun. Coranal mass ejections are another incredible phenomenon, as the Sun's magnetic forces eject mass equivalent to that of Mt Everest from the surface of the Sun and into the solar system. Known as space weather, such phenomena can have profound effects on Earth and if one should directly interact with Earth at this point in history, then most of our electronic equipment would suddenly cease to function, fortunately temporarily, but with great cost to the economy. My only real criticism of 15 Million Degrees is that there could have been more photos and plates throughout, in particular a better map of the different parts of the Sun for easy reference. Otherwise this is an absorbing and illuminating read, no pun intended, but you get it anyway.
