Astronomy quiz question: Ptolemy's model of planetary motion

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

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

Correct answer: (B)

Ptolemy's geocentric model of planetary motion features Earth at (or very near) the center of a circular deferent, along which has a planet moving along a circular epicycle. Response (D) describes Copernicus' heliocentric model of planetary motion.

Section 30674
Exam code: quiz03Ne3v
(A) : 1 student
(B) : 14 students
(C) : 7 students
(D) : 9 students

Success level: 48% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.68