Astronomy final exam question: expansion, not explosion

Astronomy 10 Final Exam, Spring Semester 2008
Cuesta College, San Luis Obispo, CA

Astronomy 10 learning goal Q12.2

[3.0 points.] Which one of the following statements best explains why the universe is not expanding like an explosion?
(A) The cosmic background radiation is nearly equal in all directions.
(B) Recession velocities of galaxies get faster with increasing distance.
(C) Ages of galaxies get younger with increasing distance.
(D) The cosmic background radiation has a very low temperature.
(E) Brightnesses of galaxies get dimmer with increasing distance.

Correct answer: (B)

In an explosion, debris travels slower as it gets farther from the explosion, which is the opposite of what is actually observed. (Response (B) is Hubble's law.)

Student responses
Section 5166
(A) : 7 students
(B) : 28 students
(C) : 1 student
(D) : 1 student
(E) : 3 students

Section 4160
(A) : 9 students
(B) : 20 students
(C) : 3 students
(D) : 0 students
(E) : 3 students