Researchers Focus on Potential ‘Cosmic Glitch’ in Gravity

In a paper published in the Journal of Cosmology and Astroparticle Physics, scientists examined the theoretical and observational cases for a ‘cosmic glitch’ in Universe’s gravity.

Wen et al. investigate a model that modifies general relativity on cosmological scales, specifically by having a ‘glitch’ in the gravitational constant between the cosmological (super-horizon) and Newtonian (sub-horizon) regimes. Image credit: M. Weiss / Harvard-Smithsonian Center for Astrophysics.

For the last 100 years, physicists have relied upon Albert Einstein’s theory of general relativity to explain how gravity works throughout the Universe.

General relativity, proven accurate by countless tests and observations, suggests that gravity impacts not simply three physical dimensions but also a fourth dimension: time.

“This model of gravity has been essential for everything from theorizing the Big Bang to photographing black holes,” said Caltech researcher Robin Wen.

“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 1% weaker when dealing with distances in the billions of light-years.”

For more than twenty years, researchers have been trying to create a mathematical model that explains the apparent inconsistencies of the theory of general relativity.

“Almost a century ago, astronomers discovered that our Universe is expanding,” said University of Waterloo’s Professor Niayesh Afshordi.

“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.”

The team’s model of a ‘cosmic glitch’ modifies and extends Einstein’s mathematical formulas in a way that resolves the inconsistency of some of the cosmological measurements without affecting existing successful uses of general relativity.

“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,” Professor Afshordi said.

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Robin Y. Wen et al. 2024. A cosmic glitch in gravity. JCAP 03: 045; doi: 10.1088/1475-7516/2024/03/045

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