ASTRON 1101 Lecture Notes - Lecture 6: Resistance 3, Celestial Sphere, Geocentric Model
8 Sep 2016
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A geocentric model was the standard model of the universe, beginning with aristotle. Aristarchus of samos proposed that the earth rotates on its axis and goes around the sun: first heliocentric model. Heliocentric model was rejected by the contemporaries of aristarchus; we know of his model only from passing references in other works. 230 time the radius: what is the sun"s radius? of its distance. How far away is the sun: further away than the moon. The moon comes between the sun and the earth during a solar eclipse. The moon, like the earth, is an opaque sphere that can block light: as a consequence, it shows phases. Aristarchus: at last quarter or first quarter, we see the bright part of the moon as a perfect half circle. When we see the moon as a half circle, the earth-moon-sun angle must be 90 .
