These observations were made with the naked eye and with the help of some simple instruments as the gnomon. The Babylonians, in particular, were rather advanced observers. Archeologists have found an abundance of cuneiform texts on astronomical observations. In contrast, there exists only one report of an observation made by Anaximander, which concerns the date on which the Pleiades set in the morning. This is no coincidence, for Anaximander’s merits do not lie in the field of observational astronomy, unlike the Babylonians and the Egyptians, but in that of speculative astronomy. We may discern three of his astronomical speculations: (1) that the celestial bodies make full circles and pass also beneath the earth, (2) that the earth floats free and unsupported in space, and (3) that the celestial bodies lie behind one another. Notwithstanding their rather primitive outlook, these three propositions, which make up the core of Anaximander’s astronomy, meant a tremendous jump forward and constitute the origin of our Western concept of the universe.