How can planet retrograde motion be explained by the Earth center hypothesis? By the Sun-center hypothesis? - How can planet retrograde motion be explained by the Earth center hypothesis? By the Sun-center hypothesis?

Ptolemaic theory - How did Galileo's observations show that the Earth-center theory (Ptolemaic) was wrong?

Explain how an object is put into orbit - Explain how an object is put into orbit about the Earth (to become a satellite). Include the relationship between gravity and velocity.

discussion questions - a. Explain how the age of rocks can be determined by radioactivity. Give an example. b. How can scientists determine the internal structure of the Earth, if the depth of the deepest well is only a tiny fraction of the earth's diameter?

Comparing the ages of the Earth and Moon. - If the ages of the Earth and Moon are nearly identical, as believed, why are most rocks found on the Moon so much older than earth rocks?