Astronomy quiz question: expansion, not explosion

Astronomy 210 Quiz 6, Spring Semester 2009
Cuesta College, San Luis Obispo, CA

__________ is evidence that the universe is not expanding like an explosion.
(A) The finite speed of light.
(B) The night sky is dark, and not blindingly bright.
(C) Galaxy redshifts are proportional to galaxy distances.
(D) Matter and antimatter annihilate to convert into energy.

Section 30674
(A) : 5 students
(B) : 3 students
(C) : 19 students
(D) : 3 students

Correct answer: (C)

In an explosion, debris travels slower as it gets farther from the explosion, which is the opposite of what is actually observed, which is Hubble's law (response (C). Response (A) is the cause of lookback time, and response (B) is Olber's explanation of why the universe cannot be infinite in extent.

A similar version of this question was asked on a Final Exam in Spring 2008.

"Difficulty level": 63% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.53