  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 modelling 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.
