… by modified way to calculate inertial mass

A comparison of the observed rotation speeds in km/s (black dots) with the predictions of MoND (dotted) and MiHsC (dashed) for galaxies and galaxy clusters of increasing baryonic mass (in Solar masses). Image credit: M.E. McCulloch

One of the first observations suggesting the existence of an invisible dark matter came in 1933 when astronomer Fritz Zwicky noticed that galaxy clusters were more energetic than they should be, according to the mass of visible stars in them, and he proposed dark matter to explain the discrepancy. Later observations of galaxies (by Rubin & Ford, among others) showed that the galaxies’ edges were rotating as fast as the insides of the galaxies, even though acceleration is supposed to decrease with radius.

Read more at: phys.org and arxiv.org/pdf