Scientists test gravity on cosmic scales and find it behaves as expected, strengthening the case for dark matter

• Using measurements from the Atacama Cosmology Telescope and a large galaxy map, researchers estimated how galaxy clusters move toward one another — a direct way to test gravity on extremely large scales.
• In that test, the results show gravity weakens with distance in the expected way across hundreds of millions of light-years, consistent with the standard cosmological picture.
• As a result, the findings narrow the range of modified-gravity theories that aim to explain galaxy motions without dark matter, reinforcing the case that dark matter exists.

Read the full story or read the study in Physical Review Letters.