In the multiple choice questions, there may be more than one correct answer. You are to choose all the correct answers.

1)  Which describes the motion of a star across the sky over the
    course of one sidereal day?
    (a) Makes one complete circle around an axis through the
        North Star.
    (b) Makes slightly more than one complete circle around an
        axis through the North Star.
    (c) Makes an approximate circle around an axis through the
        North Star, but does not return to the original point.
    (d) Moves from west to east across the sky with occasional
        loops in the opposite direction.
Answer


2)  Planet E appears larger in the sky than planet F.  Which of these
    theories could account for that fact?
    (a) E is larger than F, and closer to Earth.
    (b) E is smaller than F, and closer to Earth.
    (c) E is larger than F, and farther from Earth.
    (d) E is smaller than F, and farther from Earth.
Answer


3)  Which of the following quantities must be measured in order to
    determine the mass of Mars?
    (a) The radius of Phobos' orbit around Mars
    (b) The radius of Mars' orbit around the Sun
    (c) The period of Phobos' orbit around Mars
    (d) The period of Mars' orbit around the Sun
    (e) The period of Mars' rotation about its axis
Answer


4)  Why is Mars less dense, on average, than Earth?
    (a) Mars has smaller moons
    (b) Mars has less iron in its core
    (c) Mars has weaker gravity, so it is less compressed
    (d) Mars has ice under its surface
    (e) Mars is colder
Answer


5)  Explain how to determine which of the points of light
    in the night sky are stars, and which are planets.
Answer


6)  Explain what is really happening when a planet (say, Mars)
    executes retrograde motion.
Answer


7)  Explain how to determine how long Mars takes to rotate once
    about its axis.  Why does the method not work for Venus?
Answer