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Hubble La1

# Hubble La1 - the expansion of space For now use the figure...

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Hubble Law At first glance it looks like the Milky Way is at the center of the universe and it committed some galactic social blunder because all of the other galaxies are rushing away from it (there are a few true galactic friends like the Andromeda Galaxy that are approaching it). The Hubble Law shows that there is actually not a violation of the Copernican principle. Because the more distant galaxies move faster, this means that the galaxies (or galaxy clusters) are all moving away from each other---the universe is expanding uniformily. Every other galaxy or galaxy cluster is moving away from everyone else. Every galaxy would see the same Hubble Law. In the next chapter you will see that the expansion of the universe is the expansion of space itself---the galaxies are not moving through space, but, rather, they are being carried along with

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Unformatted text preview: the expansion of space. For now, use the figure above to see how a uniform expansion gives us the Hubble Law. Since space itself expands, all distances will increase by the same factor in the same amount of time. Galaxy (a) is 10 megaparsecs from galaxy (b) and galaxy (c) is 10 megaparsecs from galaxy (b). If the Hubble constant this time is 77 km/sec/Mpc, then galaxy (a) sees galaxy (b) moving at 770 kilometers/second away from it and galaxy (c) is moving away from galaxy (b) at 770 kilometers/second. Astronomers on galaxy (a) will see the galaxy (c) moving away at (770 + 770) kilometers/second = 1,540 kilometers/second, twice as fast as galaxy (b), because galaxy (c) is at a distance of (10 + 10) megaparsecs from galaxy (a), twice as far as galaxy (b)....
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Hubble La1 - the expansion of space For now use the figure...

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