Not more than a generation ago a survival of the old idea of a fixed center was seen in the belief that Alcyone, in the Pleiades was a "central sun" about which all the stars revolved. It is now well known that the Pleiades form a moving star cluster. Alcyone is therefore drifting slowly onward through the universe and the idea of a fixed and immovable center to which man may anchor his ideas is drifting away also. There are, it is true, local centers of systems, such, for instance, as the sun occupies in the solar system or some group of stars may occupy in the stellar system to which our sun belongs, yet _as a whole_ these systems move on and their centers with them. There is no evidence today that any absolutely immovable point exists in the heavens.