Could a different theory of gravity explain the dark matter mystery?
If gravity worked differently across large distances, would that solve the mystery of dark matter? I can’t say that it’s impossible. Alternative ideas have been offered to challenge even extremely well-tested theories like general relativity. It’s actually not so difficult to come up with an alternative theory that explains the observations better than the standard theory, since you can always fine-tune parameters in the alternative theory to match what’s observed. One could even make the case that alternative theories of gravitation aren’t any more ad hoc than a standard model that includes both dark matter and dark energy that we’re as yet unable to identify! But the standard “cold dark matter” scenario actually does an excellent job of explaining the structure of the universe across a broad range of scales. Any competing theory would have to explain that just as well. And in fact, the ultimate test of an alternative theory is whether it can both explain existing observations *and* p
