Astronomy quiz question: Copernicus' model of planetary motion

Astronomy 210 Quiz 2, spring semester 2013
Cuesta College, San Luis Obispo, CA

Copernicus' model explained the retrograde motion of a planet by:
(A) having it orbit at a different speed than Earth's orbit around the sun.
(B) moving it on a circle that itself moves around Earth.
(C) using elliptical instead of circular orbits.
(D) disregarding parallax.

Correct answer: (A)

Copernicus' heliocentric model of planetary motion features Earth and the rest of the planets orbiting the sun, with the other planets orbiting at different speeds such that retrograde motion is observed when Earth is laps (or is lapped by) a planet. Response (D) describes Ptolemy's geocentric model of planetary motion.

Section 30676
Exam code: quiz02Sl1v
(A) : 15 students
(B) : 9 students
(C) : 18 students
(D) : 0 students

Success level: 40% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.64