A recent paper is causing a stir among cosmologists and bloggers because it
appears to present evidence that dark matter may not exist. The authors’
observations reveal a strong correlation between the gravitational acceleration
observed to be acting on stars in galaxies and the gravitational acceleration
inferred from the distribution of luminous (baryonic) matter. If dark matter is
a particle, as almost everyone has been assuming, it can’t explain this
behavior. Ethan Siegel at Starts with a Bang comments on the situation here and Sabine Hossenfelder at
Backreaction discusses it here.
The authors of the paper, who are believers in
modified gravity or MOND (MOdified Newtonian Dynamics), suggest that the
observed behavior might indicate that something is missing from the current
paradigm for galaxy formation, that something like MOND is going on, or that
new dark sector physics is responsible, for example, perhaps dark matter is not
a particle but behaves more like a fluid.
Of course, as readers of this blog should know,
dark matter is not a particle, but a remnant of inflation. The oscillations of
spacetime that are the end product of inflation don’t decay completely to form
particles. Only about 16% of the energy decays to form baryonic matter. The
rest of the energy is still there in spacetime. It’s not a particle but it is
energy and it has gravitational effects. A number of mainstream cosmologists
have published papers suggesting this possibility (see here, for example), but most of their colleagues reject it (see here). One group of authors has
published a paper showing how spacetime energy
without matter could mimic dark matter, but they rejected their own idea
because they couldn’t see how such a thing could happen.
In fact, it can’t happen in the current paradigm
for particle physics and cosmology because the spacetime model is all wrong.
Actually, it’s nonexistent. If you have the right spacetime model, that is, the
model that’s the principal subject of this blog, none of this stuff is very
mysterious. See here for a discussion of
inflation and dark matter.
