https://newatlas.com/physics/modified-gravity-evidence-dark-matter/

"First proposed in 1982 by physicist Mordehai Milgrom, MOND suggests that at low accelerations, gravity’s effects are stronger than Newton’s laws describe. A side effect of this is that the motions of objects would depend not just on their own mass, but all other masses in their neighborhood. This phenomenon is known as the external field effect (EFE).

And now, researchers on the new study say they’ve observed the EFE in action in 153 different galaxies. The team was studying the rotation curve of the galaxies, which plots the orbital speed of stars and gas against their distance from the center of the galaxy.

The researchers discovered that galaxies in strong external fields slowed down much more frequently than galaxies in weaker external fields did. That’s a prediction made only by MOND, and the discovery surprised even the astronomers themselves."

"It’s an intriguing result, and it may lend some weight to the MOND hypothesis for further study. But it’s important to keep in mind that so far the bulk of the evidence still points towards dark matter, and it’ll take much more work to topple that hypothesis entirely."