Mordehai Milgrom

Mordehai Milgrom proposed modified Newtonian dynamics as an alternative explanation of the discrepancy between visible mass and inferred gravitational effects in galaxies. The modification becomes important below a characteristic acceleration scale $a_0$.

In the low-acceleration spherical limit, $a^2/a_0=GM/r^2$. For a circular orbit, substituting $a=v^2/r$ gives $v^4=GM{a}_0$, independent of orbital radius. The same limiting rule therefore links a flat outer galaxy rotation curve with a relation between baryonic mass and orbital speed. These are consequences of the proposed dynamics, not a direct detection of the underlying mechanism.^[ref]