1. Imagine that you are looking at an object a short distance away from you. What do you have to do to see parallax of that object?

2. Complete this sentence: If you are observing the parallax of an object, the farther away the object is ____________.

3. Why do we see stellar parallax?

4. Imagine you are observing the parallax above set of objects by alternately opening and closing your left and right eye. Sort the objects by how much parallax you will observe, in order of least to greatest parallax.

5. If you try to model lunar eclipses using a flat disk (like a coin) to represent Earth, you cannot reproduce the shadows that we actually observe on the Moon during these eclipses. What does this say about the possibility of a model with a flat Earth being correct?

6. Today we know that the Greek model that placed Earth in the center of the universe was wrong. Why, then, did it remain in use for such a long time?

7. According to the Earth-centered model of the ancient Greeks, the apparent retrograde motion that we observe for Mars occurs when:

8. With our modern, Sun-centered model of the solar system, the apparent retrograde motion that we observe for Mars occurs when: