Is Dark Energy Really "Repulsive Gravity"?

A powerful repulsion between normal matter and hidden pockets of antimatter could be an alternate explanation for the mysterious force known as dark energy, according to a controversial new theory.
In 1998 scientists discovered that the universe is not only expanding but that its expansion is accelerating.
This totally unexpected behavior has been called the "most profound problem" in physics, because our current understanding of gravity says that attractions between mass in the universe should be causing the expansion to slow down.
The leading theory to explain the accelerating expansion is the existence of a hypothetical repulsive force called dark energy.
But in the new study, Massimo Villata, an astrophysicist at the Observatory of Turin in Italy, suggests the effects attributed to dark energy are actually due to a kind of "antigravity" created when normal matter and antimatter repel one another.
"Usually this repulsion is ascribed to a mysterious dark energy that would uniformly permeate the cosmos, but nobody knows what it is nor why it behaves this way," Villata said in an email.
"We are replacing an unknown force caused by an unknown element with the repulsive gravity of the well-known antimatter."

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