Astronomy quiz question: horizon problem

Astronomy 10 Quiz 12, Spring Semester 2008
Cuesta College, San Luis Obispo, CA

Astronomy 10 learning goal Q12.4

[3.0 points.] Which one of the following statements best explains how inflation explains the "isotropy" of the universe today (equal amounts and same temperatures of cosmic background radiation coming from every direction)?
(A) Equal amounts of luminous matter and dark matter canceled each other out.
(B) The first generation of stars were pulled back apart into gaseous nebulae.
(C) Tiny quantum fluctuations in the universe expanded to become galaxy cluster formations.
(D) The curvature of the early universe expanded to become nearly flat.
(E) A very small part of an infinite universe increased to become the entire universe that we can see today.

Correct answer: (E)

This is the horizon problem of the cosmic background radiation, which is solved by the inflationary era. Since the universe is not old enough for the entire visible universe to have reached near thermal equilibrium, it must have experienced a brief, sudden expansion soon after recombination.

Student responses
Section 5166
(A) : 14 students
(B) : 5 students
(C) : 13 students
(D) : 10 students
(E) : 11 students