General Relativity Instead of Dark Matter? |
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Written by spacetravel.org
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Tuesday, 11 October 2005 21:58 |
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The inference that a large amount of dark matter is present in the Universe comes from the assumption that Newtonian gravity can be used to approximate the rotation speed of stars in galaxies. A study by F I Cooperstock and S Tieu of the University of Victoria has now shown that when general relativity is used instead of Newtonian gravity, there is no need to assume the existence of a halo of dark matter to fit the observed rotation curves.
Using general relativity, the researchers showed that the rotation curves for the Milky Way, NGC 3031, NGC 3198 and NGC 7331 were consistent with the mass density distributions of the visible matter concentrated in flattened disks. Newtonian mechanics works in situations like our Solar System, because the planets do not contribute significantly to the overall field. However, this is not a good approximation when studying a galaxy, because in a galaxy, the rotating matter is also the source of the gravitational field itself.
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