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Bigravity

from Inside Science

Bigravity: A Hidden ‘Gear’ for Gravity?

Physicists come up with alternate explanation of gravity that may implicate dark energy, which comprises 70 percent of our universe.

by Yuen Yiu

An artist’s conception of our universe, where gravity (the green grid) is trying to keep everything together and a mysterious dark energy (the purple grid) is trying to tear everything apart. Image credits: NASA/JPL-Caltech

Two physicists from Montana State University in Bozeman propose a way to test an existing theory of gravity where a hidden “gear” may explain the mystery of dark energy — an unknown substance that makes up 70 percent of our universe.

The paper, published in Classical and Quantum Gravity, suggests that astronomers may be able to test models of bigravity — a theory in which there are two different components of gravity, as suggested by its prefix — using X-ray, radio and gravitational wave measurements of neutron stars.

An Ever-Expanding Universe

Scientists have known since at least the 1990s that our universe is expanding at an accelerating rate. But this doesn’t make sense, because gravity — an attractive force like a rubber band — is supposed to cause our universe to contract or at least slow down the expansion.

“It’s like if you took a ball and threw it up in the air, but instead of falling back down, it just kept going up faster and faster,” said Andrew Sullivan, a physicist from Montana State University and author of the paper.

Scientists theorized that some other force must be responsible for ripping the universe apart, and “dark energy” became the placeholder term for the mysterious force.

[ click to continue reading at Inside Science ]

Posted on May 30, 2018 by Editor

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