Gravity may behave differently across the universe: study

Gravity may weaken differently across vast cosmic distances, potentially removing the need for dark matter to explain how galaxies behave, according to a new study by physicist Naman Kumar.

In the research, Kumar proposes a modified model of gravity in which Newton’s gravitational constant varies with distance.

Instead of weakening according to the traditional inverse square law, where gravity falls off as one over r squared, the new model allows gravity to decline more slowly at very large distances, following a one over r relationship. This adjustment, he argues, can explain the flat rotation curves of galaxies using visible matter alone.

Galaxy rotation curves describe how stars orbit the centers of galaxies. Observations have long shown that stars at the edges of galaxies move faster than expected based on visible matter, leading scientists to propose the existence of dark matter. Kumar’s model suggests this discrepancy can instead be explained by a change in how gravity behaves on large scales.

Building on quantum field theory, the study introduces what Kumar calls an infrared running of gravity. He applied the model to observed galactic data and found that it could reproduce galaxy rotation patterns without adding unseen matter. He said the results indicate that this approach could account for galaxy dynamics without invoking dark matter.

The findings were published in the journal Physics Letters B in 2025.

Kumar cautioned that any variation in gravity must remain subtle to stay consistent with observations of the early universe. He said further work will compare the model’s predictions with data from gravitational lensing and galaxy clusters.

While the research does not yet fully replace dark matter, Kumar said it points to possible hidden complexity in gravity itself.