The Motion of Stars, the Wanderers or Planets, as Well as the Stationary or Fixed Stars

Abstract

It can he ascertained from early writings that twenty-five hundred years ago several philosophers came to observe movements in certain individual stars other than their aforementioned twenty-four hour cycle. By reason of this unusual movement, they called these stars wanderers or planets, and for this reason they began to formulate certain hypotheses according to which they calculated the motions that were made, to analyse these motions, and to divide them arithmetically into certain periods expressed in years, months, days, hours, and minutes. They were of the opinion, moreover, that these planets rise and set, now in these regions of the horizon, now in those, and that they swing from the direction of the south up higher into the north and decline again lower into the south, both movements being, however, within certain bounds. Similarly at times the planets move more rapidly, at others more slowly, and appear now larger and again smaller. In appearance, moreover, they differ from one another as well as from fixed stars and at times are close together and at others are separated. Occasionally they hide one or another of the fixed stars and then in turn are themselves covered. Furthermore they are not equally visible to all inhabitants of the earth.