Question 1: How did Ptolemy explain the retrograde motions of the planets? Be sure to include a well-labeled diagram.

Question 2: What is special about the position and speed of the Earth when it is at aphelion? Which law or theory tells us this?

Question 3: The Dwarf Planet Pluto orbits the Sun every 248 years, what is its average distance from the Sun?

Question 4: A penny is 1.5 millimeters thick.

(a) How many waves of red light could fit into this distance?

(b) How many waves of violet light could fit into this distance?

(c) How many times more energy does violet light have compared to red light?

Question 5: Which types of electromagnetic radiation from space pass through Earth's atmosphere to reach the ground? Which types don't pass through Earth's atmosphere? Provide an example of an observatory that looks at the type of radiation that reaches the ground, choose the closest one to where you live.

Question 6: Describe reflection and refraction. How do these processes enable astronomers to build telescopes?

Question 7: Compare the light-gathering power of SFSU's Big Red 0.4-m telescope (which most of you saw Jupiter and its Moons through) to that of a fully dark-adapted human eye (∼ 5 mm). Does this make sense why we can't see Jupiter's Moons with the naked eye?

Question 8: Make an initial guess as to which exerts a stronger gravitational force on the Earth, the Sun or the Moon. Then use Newton's law of gravitation to compare the gravitational force the Moon exerts of the Earth with the gravitational force that the Sun exerts on the Earth? Now move the Sun 10 times further away from Earth and do the same comparison. Did you results change?