Scientific Tweak May Fix Einstein Theory 'Glitch'

A bizarre "cosmic glitch" in the theory of how the gravity of the universe works may have been mended.

The strange glitch in Einstein's description of gravity in his theory of general relativity may explain some of the mysteries of how gravity works on a cosmic scale, according to a new paper in the Journal of Cosmology and Astroparticle Physics.

Einstein's theory of general relativity describes how gravity works across the cosmos, suggesting that gravity can impact the three dimensions of space, but also a fourth dimension: time.

The theory imagines the universe as a stretchy fabric called space-time. Every object with mass (like stars, planets, or even you) bends this fabric. The more massive the object, the more it warps the space around it. Think of setting a heavy ball on a stretched rubber sheet—the sheet dips around the ball.

In general relativity, gravity is not seen as a force acting at a distance—as Newton described it—but as the effect of the bending of space-time by mass. Objects move toward each other not because they are being pulled directly by some invisible force, but because they are following the curves in space-time created by their masses. For example, Earth orbits the sun not because it is being pulled directly by the sun, but because it is traveling along the curved space-time around the sun.

General relativity made predictions that were later confirmed by experiments and observations. For instance, it predicted the bending of light by gravity (gravitational lensing), the existence of black holes, and gravitational waves, which are ripples in space-time created by violent astronomical events.

However, there are some things that the theory cannot adequately explain.

"This model of gravity has been essential for everything from theorizing the Big Bang to photographing black holes," study co-author Robin Wen, a recent Mathematical Physics graduate at Canada's University of Waterloo, said in a statement.

"But when we try to understand gravity on a cosmic scale, at the scale of galaxy clusters and beyond, we encounter apparent inconsistencies with the predictions of general relativity. It's almost as if gravity itself stops perfectly matching Einstein's theory. We are calling this inconsistency a 'cosmic glitch': gravity becomes around one percent weaker when dealing with distances in the billions of light years."

Scientists have now come up with a new tweak to the theory that they hope explains some of these inconsistencies.

"Almost a century ago, astronomers discovered that our universe is expanding," study co-author Niayesh Afshordi, a professor of astrophysics at the University of Waterloo and researcher at the Perimeter Institute, said in the statement.

"The farther away galaxies are, the faster they are moving, to the point that they seem to be moving at nearly the speed of light, the maximum allowed by Einstein's theory. Our finding suggests that, on those very scales, Einstein's theory may also be insufficient."

Therefore, the new model should still explain the phenomena that general relatively works for, but also those that it cannot explain.

"Think of it as being like a footnote to Einstein's theory," Wen said. "Once you reach a cosmic scale, terms and conditions apply."

"This new model might just be the first clue in a cosmic puzzle we are starting to solve across space and time," Afshordi added.

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