Tully-Fisher relations and retardation theory for galaxies

Galaxies are huge physical systems having dimensions of many tens of thousands of light years. Thus any change at the galactic center will be noticed at the rim only tens of thousands of years later. Those retardation effects seem to be neglected in present day galactic modeling used to calculate rotational velocities of matter in the rims of the galaxy. The significant differences between the predictions of Newtonian theory and observed velocities are usually explained by either assuming dark matter or by modifying the laws of gravity (MOND). In this essay, we will show that taking retardation effects into account one can explain the azimuthal velocities of galactic matter and the well known Tully-Fisher relations of galaxies.