Motion of the Celestial bodies across our Sky

Observations

• Sun Rises in the East and Sets in the West ... so the Sun moves, right?
• Moon also seems to rise in the East and set in the West (and sometimes collides with the Sun!) - so it moves, right?
• The Stars rise in the East and set in the West ... well some of them .. the North Pole is always there in the Northern Hemisphere .. they move?
• Some planets seem to move very slowly relative to the stars, but others move more quickly?

We went through great pains to try to prove an Earth-Centered Universe made sense .. but even greater pains to understand our errors!

The Earth centered Universe seemed logical at the time, but the more we piled on "fixes", the more cumbersome the theory became (not unlike a certain PC Operating System, huh??).

Motion of the "heavenly bodies" in the sky is most directly caused by our own Earth's rotation on its axis.

Current model :

• Stars form a background that is essentially unchanging (too long a time to wait for our short lifetimes)
• Solar system orientation is essentially fixed relative to the star field
• Planets move relatively rapidly (in close) around the Sun
• Earth (and all the other bodies) rotates around an axis .. as it revolves around the Sun.

Results :

• Because we spin in a counterclockwise direction (seen from the top), all the other objects in our sky seem to rotate clockwise (from the top) - thus East to West
• In one years time, we come back to essentially the exact same star pattern in our skies (thus we can make star charts that don't have to be updated every year!)
• Since the planets close to the Sun move rapidly, they appear to move (against the background stars) more rapidly than the stars.
• Some of the distant planets hardly appear to move at all relative to the background stars
• You sometimes get some weird behavior (retrograde motion!) - stars going backwards in the sky!