The accelerations of Solar System objects are clearly much larger than those for stars in galaxies or for galaxies in clusters. (This statement is not true for the Oort Cloud comets, but they are not ...The accelerations of Solar System objects are clearly much larger than those for stars in galaxies or for galaxies in clusters. (This statement is not true for the Oort Cloud comets, but they are not relevant currently to the arguments presented here because we cannot track them when they are not close to the Sun.) And of course, accelerations are much, much larger for falling bodies near the surface of Earth.
If we take the observations of the motions of stars and gas in galaxies, and the motions of galaxies in galaxy clusters, at face value, then they imply the existence of additional mass that is unseen:...If we take the observations of the motions of stars and gas in galaxies, and the motions of galaxies in galaxy clusters, at face value, then they imply the existence of additional mass that is unseen: dark matter. The unseen mass could take several forms. Some are fairly simple, others quite exotic. We will consider several possibilities and explore what evidence exists for and against them.
