Unraveling the Cosmic Mystery: Why Gravity Behaves Differently Across Scales in the Universe

Scientists have confirmed that gravity behaves exactly as predicted by Albert Einstein’s general relativity and Isaac Newton’s laws across the largest cosmic scales, resolving a long-standing question about whether the fundamental laws of physics change over vast distances in the universe.

The finding comes from a new analysis of data collected by the Atacama Cosmology Telescope in Chile, which measured how the universe’s oldest light — known as the cosmic microwave background — bends around massive galaxy clusters. By tracking this gravitational lensing effect, researchers were able to map how gravity pulls on matter across billions of light-years.

According to the study, published in Physical Review Letters on April 15, 2026, the observed behavior of gravity matches theoretical predictions with high precision, effectively ruling out alternative theories such as Modified Newtonian Dynamics (MOND) that would require changes to our understanding of gravity on large scales.

David Spergel, president of the Simons Foundation and co-author of the study, emphasized that the results reinforce confidence in the Standard Model of Cosmology, which relies on dark matter and dark energy to explain the universe’s structure and expansion. “While the standard model with dark matter and dark energy seems strange, it continues to do a remarkable job of describing the universe that we are observing,” Spergel said.

This is another triumph for general relativity and our ‘standard model.’

David Spergel, Simons Foundation

Patricio A. Gallardo, a research associate at the University of Pennsylvania’s Department of Physics and Astronomy, noted that the research addresses a longstanding puzzle in astrophysics: whether the laws of gravity hold true everywhere or if discrepancies in galactic motion signal a need to revise fundamental physics. “Astrophysics has been plagued by a massive discrepancy in the cosmic ledger,” Gallardo said, referring to observations of galaxies moving faster than expected under visible matter alone.

The study used the Atacama Cosmology Telescope’s high-resolution measurements of gravitational lensing to test gravity’s behavior across cosmic distances. Unlike earlier probes that focused on smaller scales or relied on assumptions about galaxy dynamics, this approach directly observed how spacetime curvature affects light from the early universe, providing a cleaner test of gravitational physics.

By confirming that gravity operates consistently from solar system scales to the largest observable structures, the findings remove a key motivation for alternative gravity theories and strengthen the case that dark matter and dark energy — rather than modified gravity — are responsible for the observed anomalies in galactic and cosmic motion.

The research represents one of the most precise large-scale tests of gravity to date and supports the continued use of Einstein’s framework in cosmological modeling, space mission planning, and the interpretation of data from space telescopes such as the James Webb Space Telescope and upcoming missions like the Vera C. Rubin Observatory.