To Explain Away Dark Matter, Gravity Would Have to Be Really Weird, Cosmologists Say
Dark matter, the invisible stuff whose gravity is thought to hold galaxies together, may be the least satisfying concept in physics. But if you want to get rid of it, a new study finds, you’ll need to replace it with something even more bizarre: a force of gravity that, at some distances, pulls massive objects together and, at other distances, pushes them apart. The analysis underscores how hard it is to explain away dark matter. Concocting such a theory of gravity “is so complicated that it seems very unlikely that anyone could come up with a scenario that would work,” says Scott Dodelson, a theoretical physicist at Carnegie Mellon University, who wasn’t involved in the new work. Still, some theorists say it may be possible to pass the test.