Just a little niggling re: If Occam were to have had his way, we would all still believe the earth was flat, or was the center of the universe...
Actually, the geocentric model was much, much more convoluted than the correct heliocentric one:
But, the geocentric model was not simple. If everything were to orbit about Earth, then they should have a regular motion in a constant direction. This model would be represented by the Earth surrounded by spheres upon which the planets, moon, and sun would move, plus a sphere for the fixed stars.
This is not accurate, for there were times when planets would move in a retrograde direction. In an attempt to account for this, scientists added extra circles onto the spheres. Thus, the planets moved upon the little circles, and the little circles moved on the bigger circles. These circles upon circles were called "epicycles," and the larger circles were called "deferents." This is shown in the image to the right. This is a "three planet" system, with the Earth at the center, and two planets around it. The red and yellow circles represent the deferents, while the green and orange the epicycles. The green and orange balls represent the two planets.
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Excerpted from:
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