Dancing mergers and hungry giants

chris impey

Chris Impey, at least when it comes to publishing, is doing things somewhat backward. The professor of astronomy’s 2010 book is called How It Ends, and his latest (non fiction) book is called How It Began. Unlike physics professors’ usual fixation with how it all began, Impey starts off with where we are going. How It Ends is a book about funnily enough, endings, beginning with the science of death and gradually expanding its scope to accommodate predictions as to how the universe will end (the science retains some degree of speculation about what the future holds). It takes a more scientific approach to the rather forlorn topic of the last section of H G Well’s Time Machine.

Impey covers the eventual turning of our sun into a red giant that engulfs the inner planets of the solar system, the eventual merger of our galaxy and Andromeda (the new combined galaxy has been given the name ‘Milkomeda’), which would be a sort of dancing merger of stars that are so sparsely scattered that there wouldn’t be much of a crash, the dying of stars into ‘cinders’, and the heat death of matter itself.

Along the way we get the physics of black holes, reminders of the strange, as yet virtually untraceable entities dark matter and dark energy, which make up most of the matter in our universe, and speculations about what shape the universe is (no, you can’t just think of it as a globe).

We also get a reminder of the vast emptiness of space. The night sky in the countryside may look full of stars – a crowded firmament – but the following example shows just how empty and vast the universe is. If we shrank the solar system 300 million times, and the Earth was the size of a golf ball, the nearest star would be 35,000 kilometres away. Or if that doesn’t do it, try thinking about how big our Milky Way is, and then think that the universe is filled with billions of galaxies, some of them so far away that they are beyond the “horizon” of being visible because of the expansion of the universe.


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