He found and summarized arguments for a spherical Earth, thus ruling out older models with a flat Earth. Moreover, he constructed a world system of concentric spheres around Earth in the center (i.e., a geocentric system), carrying planets and the outermost the "Fixed" stars - thus forming a finite, spherical universe. He believed that "nebulous" objects like comets or the Milky Way belonged to the near-Earth space, the domain of meteorology instead of astronomy. He considered meteorological phenomena short-lived, while the "heavenly" spheres would never change.
Aristotle's view of the world was more dogmatic than empirical. These philosophic views, further developed and enriched with Ptolemy's astronomical theories, later became the foundations of Western European understanding for more than a millennium.
Aristotle probably recorded ancient observations of the open star cluster M41 in Canis Major around 325 BC. Also, he possibly described open cluster M39 in Cygnus about the same time, both as nebulous, comet-like objects.
Aristotle is honored by the naming of a Moon Crater: Aristoteles (50.2N, 17.4E, 87.0 km; officially named 1935). Also, there is asteroid (6123) Aristoteles, discovered on September 19, 1987 at Smolyan Observatory by E.W. Elst and provisionally designated 1987 SH2; pre-discovery observations had been labelled 1955 RU, 1969 QE, 1971 BJ2, 1975 EL3, 1980 TR10, and 1982 DF6.
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