Antigravity! Trumps “Dark Energy” for the Accelerated Expansion of the Universe


An exciting new theory says that antimatter could exist in the voids between galaxy clusters and superclusters and that some kind of repulsive gravity –- antigravity –- is pushing the Universe apart. The new theory is a direct challenge to the accepted theory for the Universe expanding at an accelerating rate: the presence of an unidentified X Factor labeled "dark energy," although several other possibilities have been proposed.

As a new study shows, general relativity predicts that the gravitational interaction between matter and antimatter is mutually repulsive, and could potentially explain the observed expansion of the Universe without the need for positing an elusive dark energy.

Ever since antimatter was discovered in 1932, scientists have been investigating whether its gravitational behavior is attractive –- like normal matter –- or repulsive. Most physicists think that the gravitational behavior of antimatter should always be attractive, as it is for matter. However, the question of whether the gravitational interaction between matter and antimatter is attractive or repulsive has not been answered until now.

In the new study, Massimo Villata of the Osservatorio Astronomico di Torino (Observatory of Turin) in Pino Torinese, Italy, has shown that the current formulation of general relativity predicts that matter and antimatter are both self-attractive, yet matter and antimatter mutually repel each other. But unlike previous antigravity proposals –- such as the idea that antimatter is gravitationally self-repulsive –- Villata’s proposal does not require changes to well-established theories.

The image at the top of page is a Chandra mosaic of images of the Fornax galaxy cluster which reveals that the vast cloud of ten-million-degree Celsius gas surrounding the cluster core has a swept-back cometary shape that extends for more than half a million light years.

Credit: NASA/CXC/Columbia U./C.Scharf et al.

The Daily Galaxy via and EPL (Europhysics Letters).

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Image credit: NASA and ESA.

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