Cosmologists observing galaxies have been aware of apparent aberrations with standard theories of gravity since at least the 1930s, and in this century exploration of the "dark matter" hypothesis has got most attention in the science press ─ if the explanation is extra mass that we can't see, what could the source of that extra mass be?
But an alternative to dark matter has never been off the table ─ that the problem lies not with unseen forms of matter, but with our standard theories of gravity itself.
Here's a link to a computer simulation of galaxy formation in which no dark matter is assumed but instead a particular variation of how gravity works is applied ─
and
but not perfect ─
But an alternative to dark matter has never been off the table ─ that the problem lies not with unseen forms of matter, but with our standard theories of gravity itself.
Here's a link to a computer simulation of galaxy formation in which no dark matter is assumed but instead a particular variation of how gravity works is applied ─
According to the [hypothesis] the attraction between two masses obeys Newton's laws only up to a certain point. Under very low accelerations, as is the case in galaxies, it becomes considerably stronger. This is why galaxies do not break apart as a result of their rotational speed.
and
the attraction of a body depends not only on its own mass, but also on whether other objects are in its vicinity.
The result of the simulation was encouraging ─
the distribution and velocity of the stars in the computer-generated galaxies follow the same pattern that can be seen in the night sky. "Furthermore, our simulation resulted mostly in the formation of rotating disk galaxies like the Milky Way and almost all other large galaxies we know," says the scientist. "Dark matter simulations, on the other hand, predominantly create galaxies without distinct matter disks -- a discrepancy to the observations that is difficult to explain."
but not perfect ─
the [...] results [...] do not correspond to reality in all points.
So ─
"Our simulation is only a first step," emphasizes Kroupa. For example, the scientists have so far only made very simple assumptions about the original distribution of matter and the conditions in the young universe. "We now have to repeat the calculations and include more complex influencing factors. Then we will see if the MOND theory actually explains reality."