  The primary argument levelled against Milgrom's MOND is that it has no
theoretical support, even though considerable effort has been expended in
attempting to provide it. Against that criticism, MOND irrefutably enjoys an
expanding portfolio of success and so is almost certainly tapping into
something fundamental. But what?
  Over roughly the same period that MOND has been a topic of controversy,
Baryshev, Sylos Labini and others have been claiming, with equal controversy in
earlier years, that, on medium scales at least, material in the universe is
distributed in a quasi-fractal $D\approx 2$ fashion. There is a link: if the
idea of a quasi-fractal $D\approx 2$ universe on medium scales is taken
seriously, then there is an associated characteristic mass surface density,
$\Sigma_F$ say, and an associated characteristic acceleration scale $a_F = 4\pi
G \,\Sigma_F$.
  The whole success of MOND is predicated upon the idea of a critical
acceleration scale, $a_0$. It is an obvious step to make the association $a_0
\sim a_F$ and then to consider the MOND critical acceleration boundary simply
as a marker for a characteristic mass surface density boundary separating
'galaxy' from an environment characterized by $\Sigma_F$. This provides a route
to the synthesis of conservative MOND from first principles.
  The radial acceleration relation (RAR) for conservative MOND when applied to
the SPARC sample is the unity line. There is no mass discrepancy.

Astrophysics of Galaxies