Gravity theory dispenses with dark matter
A modified theory of gravity that incorporates quantum effects can explain a trio of puzzling astronomical observations – including the wayward motion of the Pioneer spacecraft in our solar system, new studies claim.
The work appears to rule out the need to invoke dark matter or another alternative gravity theory called MOND (Modified Newtonian Dynamics). But other experts caution it has yet to pass the most crucial test – how to account for the afterglow of the big bang.
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The theory, called scalar-tensor-vector gravity (STVG), adds quantum effects to Einstein's theory of general relativity. As in other branches of physics, the theory says that quantum fluctuations can affect the force felt between interacting objects.
In this case, a hypothetical particle called a graviton – which mediates gravity – appears in large numbers out of the vacuum of space in regions crowded with massive objects such as stars. "It's as if gravity is stronger" near the centres of galaxies, Brownstein told New Scientist. "Then, at a certain distance, the stars become sparse, and the gravitons don't contribute that much." So at larger distances, gravity returns to the behaviour described by Newton.
The full article can be read at
http://www.newscientistspace.com/article.ns?id=dn8631
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