Astronomers have been searching for a mysterious substance called “dark matter” since the 1930s. Most scientists still believe it exists, despite many fruitless decades. Now we propose a new theory of general relativity that may ultimately get rid of the need for dark matter, and perhaps get physicists to think in terms of things we know exist.
One reason why physicists have been trying to find dark matter is because of anomalies in the “galaxy rotation curve” data. Matter, such as gas and stars, tends to rotate around the centre of individual galaxies. The variation of this rotation speed if plotted against distance from the centre of the galaxy gives what is known as that galaxy’s rotation curve.
Matter that orbits quite far away from the centre of the galaxy is expected to have a lower rotational speed than matter orbiting closer to the centre. This expectation comes from either those laws based on Newton’s theory or the predictions of Einstein’s theory of general relativity.
But observations consistently show a “flattening” of the rotation curves – in which speeds remain essentially constant beyond a certain distance from the galactic centre. Rather than challenge the theories of Newton and Einstein, it has been accepted that each galaxy must be surrounded by a vast halo consisting of dark matter (termed so because it cannot be directly observed).
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