Testing the Hypothesis of Modified Dynamics with Low Surface Brightness Galaxies and Other Evidence

The rotation curves of low surface brightness galaxies provide a unique data set with which to test alternative theories of gravitation over a large dynamic range in size, mass, surface density, and acceleration. Many clearly fail, including any in which the mass discrepancy appears at a particular length scale. One hypothesis, Modified Newtonian Dynamics (MOND), is consistent with the data. Indeed, it accurately predicts the observed behavior. We find no evidence on any scale that clearly contradicts MOND and much that supports it.