I should have read the thread before responding, because so many proposes the same thing. So I’ll promote the response I did to Dark Jaguar:
@Dark Jaguar, Robert Oldershaw, Ranjeet Tate:
That — modifications of gravity — has been ruled out by the Bullet Cluster collision experiments that Ethan describes as the last, conclusive evidence in his bullet list. (So yes Ranjeet, Woit’s speculations are discredited from the start.)
The problem is that you would need a different gravity for each collision description, there are a number of them, and just having two irreconcilable theories would be a problem.
@Tim Nimsic: No, a spinning or else non-uniform universe was just ruled out by Planck observations a few week ago.