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Unformatted text preview: Homework 2 solutions (1.) The following observational evidence led Aristotle to conclude that the earth is spherical: 1. The border of the shadow of the earth on the moon during the course of a lunar eclipse is always circular, no matter how high the moon is over the horizon. Only a sphere casts a circular shadow in every direction; if the earth were a disk, the shadow would be elongated (elliptical) except directly above and below. 2. Travelers going south see southern constellations rise higher above the horizon. This is only possible if their horizon is at an angle to the horizon of observers farther north and therefore the earth cannot be flat. A small change in position to south or north causes an alteration of the horizon: there is much change in the stellar constellations as one moves southward or northward. There are some stars that are seen in Egypt which are not seen in the northerly regions and vice versa....
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