discussion questions - f. Which is hotter, Mercury or Venus? Why? h. Explain why there are two general families of planets, rocky terrestrial and gaseous jovian. j. What knowledge do comets and asteroids provide to studies of the origin of the solar system?

The origin of the Moon. - What do observations of the Moon suggest about its origin?

The discovery of Uranus and Neptune. - The first planets discovered since ancient times were Uranus and Neptune. Compare how they were discovered.

How scientists determine the internal structure of the Earth. - 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?