Earth and Space 21.1
Why do the planets "drift" east relative to the stars and then move west for periods of time? They are moving in separate orbits around the sun as it goes around the earth, producing the periodic backtracking.
They are moving in the same rotation sense as the earth around the sun, but as the earth moves faster (or slower, depending on the planet) the motion appears to be backwards.
How did the Greeks estimate the size of the earth?
They measured the angle of the sun above the horizon at midday in two places with different latitude and used the angle to estimate the circumference of the earth.
In the Ptolemaic (Greek) model of the universe, the stars are attached to the ________.
celestial sphere
The earliest astronomical records appear to have been made by the ancient Chinese, Egyptians, and Babylonians in order to ________.
determine when to plant crops or hunt animals based on seasonal changes
According to the Ptolemaic (Greek) system, the planets have circular orbits.
true
