Caption: A cartoon of the full Ptolemaic system.

Features:

1. The Ptolemaic system an is elaborated epicycle model.

2. The equants and the eccentric placement from Solar System are NOT shown.

3. Note that Mercury and Venus have their epicycles on the Earth-Sun line. This must be so at all times since the inferior planets exhibit an apparent oscillation around the Sun position on the sky.

4. The order of the planets (which here include the Sun and the Moon) is NOT set by the rules of epicycle models.

5. You can put the planets at any distance from the Earth---only there angular positions must match the observations---i.e., save the phenomena.

6. However, Ptolemy (c.100--c.170 CE) got the planets in a mostly sort-of-right order going outward from the Earth.

   He had to use extra hypotheses to get the order.

   The main hypothesis was that planets all move at about the same speed in space. Therefore, the slower a planet moved in angle, the farther away it must be.

   Since the angular velocities do change, Ptolemy had to use other considerations to fully determine his order.

7. Ptolemy did know the Moon was about 60 Earth radii away and was almost certainly the closest astronomical object.

   He knew NO other distances which is why he didn't get the correct Solar System model.