PHYS 2600 Chapter Notes - Chapter 3-4: Deferent And Epicycle, Geocentric Model, Inferior And Superior Planets
25 Sep 2017
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3 eclipses and the motion of the moon. 3-6 ancient astronomers measured the size of earth and attempted to determine distances to the sun and moon. Eratosthenes devised a way to measure the circumference of the spherical earth. Aristarchus determined the relative distances of the sun and moon. Knew sun, earth and moon form a right triangle at first or third quarter moon (90 degrees at the moon) & angle b/w moon and sun is 87 degrees or 3 degrees less than a right angle. Concluded sun is 20x farther from us than is the moon. He erred in measuring angles and that avg distance to the sun is 390x larger than the avg distance to the moon. Time it takes moon to move through earths shadow during a lunar eclipse he estimated that the diameter of earth to be 3x larger than the diameter of the moon.
