  The irrefutable successes of MOND are predicated upon the idea that a
critical gravitational acceleration scale, $a_0$, exists. But, beyond its role
in MOND, the question: 'Why should a critical gravitational acceleration scale
exist at all?' remains unanswered. There is no deep understanding about what is
going on.
  Over roughly the same period that MOND has been a topic of controversy,
Baryshev, Sylos Labini, Pietronero and others have been arguing, 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
scale, $\Sigma_F$ say, and an associated characteristic gravitational
acceleration scale, $a_F = 4 \pi G \Sigma_F$. If, furthermore, the
quasi-fractal structure is taken to include the inter-galactic medium, then it
is an obvious step to consider the possibility that $a_0$ and $a_F$ are the
same thing.
  Subsequently, via a modern geometric realization of the Leibniz-Mach
worldview, we obtain a detailed theoretical understanding of how galaxy disks
should interact with a $D\approx 2$ quasi-fractal IGM. This understanding takes
the form of a superficially unremarkable scaling relationship which, used with
standard photometric mass-modelling applied to SPARC data, shows that $a_F
\approx 1.2\times 10^{-10}\, mtrs/sec^2$ is explicitly embedded in that data.
Since the scaling relationship also gives rise to the Baryonic Tully-Fisher
Relationship, but with $a_0$ replaced by $a_F$, we are led unambiguously to the
conclusion that $a_0$ and $a_F$ are, in reality, one and the same thing.
