Gravity May Behave Differently Across the Universe, Study Suggests

Recent scientific studies imply that dark matter, which is estimated to far outweigh normal matter, may not exist at all. Instead, physicist Naman Kumar suggests that gravity, which holds planets in orbit and keeps galaxies from flying apart, may actually weaken at different distances. Newton's constant runs with distance in his equation, which comes out as 1/r, the result being that dark matter is not needed to explain galaxy rotation curves.

A new gravitational model

According to the new research, while building on quantum field theory, study author Naman Kumar allowed Newton's gravitational constant to vary with scale. In this "infrared running" model, gravity's pull falls off more slowly: at very large distances, it follows a 1/r rule rather than 1/r². This naturally produces the flat rotation curves seen in spiral galaxies without extra matter. Kumar applied the model to actual galactic data and found it reproduced observed rotations using only visible matter. As Kumar explains, "These results suggest the infrared running scenario could account for galaxy rotation without invoking dark matter".

Implications and outlook

The results of Kumar's research were published in the journal Physics Letters B in 2025. He is keen to point out that any variation in gravity must be subtle to match the results observed in the early universe. His model is slowly evolving while at the same time maintaining consistency with the results from the cosmological background as it diverges at a late stage. The next line of research is comparing the results to those observed in gravitational lensing as well as those from clusters of galaxies. Although the research "does not yet fully replace dark matter," Kumar believes the method "highlights gravity's possible hidden complexity."