A recent study has identified a potential “glitch” in the gravitational behavior around ancient structures, challenging Einstein’s theory of general relativity, our best description of the universe at large scales.
An artistic representation shows an observer crossing a black hole’s event horizon (Image credit: NASA’s Goddard Space Flight Center/J. Schnittman and B. Powell).
Researchers suggest a “cosmic glitch” in gravity might explain the universe’s peculiar behavior on the largest scales. Albert Einstein’s 1915 theory of general relativity remains the most accurate model of how gravity functions from medium to large scales. However, when examining vast groups of interacting galaxies, some inconsistencies suggest that gravity might weaken slightly over cosmic distances.
A study published on March 20 in the Journal of Cosmology and Astroparticle Physics describes this discrepancy as a “cosmic glitch.” The researchers propose that this could help us understand some of the universe’s most enduring mysteries.
“It’s like making a puzzle on the surface of a sphere, then laying the pieces on a flat table and trying to fit them together,” explained study co-author Niayesh Afshordi, a professor of astrophysics at the University of Waterloo in Ontario, to Live Science. “At some point, the pieces on the table will not quite fit each other because you are using the wrong framework.”
The “glitch” may indicate a fundamental violation of Einstein’s equivalence principle, potentially leading to new perspectives on quantum gravity, the Big Bang, or black holes, Afshordi added.
**Cosmos for Concern**
Einstein’s theory of general relativity excels in describing the universe above quantum scales and has predicted various cosmic phenomena like black holes, gravitational lensing, gravitational waves, and the Big Bang. However, discrepancies remain. Attempts to apply general relativity to quantum scales result in unusable equations. Additionally, the need to introduce dark matter and dark energy to complete our current model of the universe, despite these entities never being directly detected, raises questions. These components fail to explain the varying expansion rates of the cosmos.
To address these issues, the authors of the new paper suggest a simple modification to Einstein’s theory at different distance scales. Afshordi proposes that the universal constant of gravitation varies on cosmological scales compared to smaller scales like those within the solar system or galaxies. He calls this a “cosmic glitch.”
This tweak affects patterns in the cosmic microwave background—radiation from 380,000 years after the Big Bang—and the universe’s structure and expansion. The changes are subtle but imply significant shifts in our understanding of gravity. “We find evidence for the glitch: cosmic gravity is about 1% weaker than galactic/solar-system gravity,” Afshordi noted.
The researchers believe next-generation galaxy surveys, such as those using the European Space Agency’s Euclid space telescope, the Dark Energy Spectroscopic Instrument, and the Simons Observatory, could confirm this glitch. These instruments should provide measurements four times more precise than current capabilities.
However, some scientists argue that simply modifying Einstein’s relativity might not suffice. Scott Dodelson, a professor and chair of the physics department at Carnegie Mellon University, who was not involved in the study, suggests the discrepancies might indicate a need for a completely new understanding of the universe.
“It’s not that surprising that this new model is a slightly better fit to the data, but maybe that is telling us something,” Dodelson said. “If so, it means we understand even less than we thought we did. My hunch is that instead of adding more new stuff, we need a new paradigm. But no one has come up with anything that makes any sense yet.”
