If you wanted to document the apparent retrograde motion of Mars, you would need to measure and record Mars's __________ over a period of __________.
Check two responses below: one for each of the two blanks in the question.

(Blank 1) position among the constellations
(Blank 1) angular distance from the Sun in the sky
(Blank 1) speed as it moves east to west across the sky
(Blank 1) altitude and direction in the sky
(Blank 2) about 4 to 6 hours
(Blank 2) one full night
(Blank 2) about one week
(Blank 2) several months


What is really happening in space during the periods when we see Mars going through apparent retrograde motion?

Earth is passing by Mars in its orbit around the Sun.
Mars is moving along its orbit in the opposite direction from the way it usually moves.
Mars and the Sun both appear to be in the same constellation as viewed from Earth.
Earth and Mars are moving in opposite directions around the Sun.


The Sun-centered system pictured in the lower window of the animation offers a simple explanation for observations of apparent retrograde motion. Should these facts alone have been enough to convince the ancient Greeks that Earth really does go around the Sun?

Yes, but the Greeks were unable to detect apparent retrograde motion and therefore didn't
know that it ruled out an Earth-centered universe.
Yes, but the Greeks did not realize it because they never even considered a Sun-centered model.
No, because apparent retrograde motion still happens in an Earth-centered system as the Sun passes by a planet in its orbit around Earth.
No, because the Greeks had an Earth-centered model that also accounted for apparent retrograde motion.