  Massive gravity provides a natural solution for the dark energy problem of
cosmology and is also a candidate for resolving the dark matter problem. I
demonstrate that, assuming reasonable scaling relations, massive gravity can
provide for Milgrom's law of gravity (or "modified Newtonian dynamics") which
is known to remove the need for particle dark matter from galactic dynamics.
Milgrom's law comes with a characteristic acceleration, Milgrom's constant,
which is observationally constrained to $a_0\approx1.1\times10^{-10}$ m/s$^2$.
In the derivation presented here, this constant arises naturally from the
cosmologically required mass of gravitons like $a_0\propto
c\sqrt{\Lambda}\propto c H_0\sqrt{3\Omega_{\Lambda}}$, with $\Lambda$, $H_0$,
and $\Omega_{\Lambda}$ being the cosmological constant, the Hubble constant,
and the third cosmological parameter, respectively. My derivation suggests that
massive gravity could be the mechanism behind both, dark matter and dark
energy.
