In article , Steve Willner
writes:

Mod. note -- I suspect that the author has inadvertently omitted
"does NOT" or some similar wording in the previous sentence, and meant
to write something like this:
For those not
following, the argument is that in most galaxies and galaxy clusters,
the mass of detectable stars exerting Newtonian gravity does not
account for the observed motions.
My apologies if I've misunderstood the author's intent here!
-- jt
]]
Therefore, _either_ there is more mass than
that of the visible stars ("dark matter"), _or_ the Newtonian gravity
law is wrong. However, we know Newtonian gravity is right in our
solar system (except for tiny GR corrections) and in objects as large
as globular clusters, so if the gravity law is the problem,
modification ("MOND") is required only in objects as large as
galaxies. Here we have a large galaxy where no modified gravity law
is needed. If MOND is right, how can it fail to apply to this
galaxy?

Just a quick note since I am travelling with limited access and haven't
yet read the paper. In MOND, it is not the size which matters, but
rather the acceleration. MOND effects are supposed to kick in when the
acceleration is below some fiducial value. Accelerations are high in
the Solar System and low in the outskirts of galaxies.