Rank these times based on the wavelength of the peak intensity of the cosmic background radiation at those times, from shortest to longest. (Hint: consider how the temperature of the universe or the cosmic background radiation changed with time.)
A) today, 1 million years after the Big Bang, 100 million years after the Big Bang
B) 100 million years after the Big Bang, 1 million years after the Big Bang, today
C) today, 100 million years after the Big Bang, 1 million years after the Big Bang
D) 1 million years after the Big Bang, 100 million years after the Big Bang, today
Question 2
All of the following hypothetical planets orbit a star with the same mass as the Sun (one solar mass).
Which one has the shortest orbital period? (If two objects would have the same orbital period to within a difference of less than 1 consider them as having identical periods.)
A) Planet A: one Earth mass and 1 AU from the star
B) Planet B: two Earth masses and 1 AU from the star
C) Planet C: two Earth masses and 2 AU from the star
D) Planets A and B
E) Planets B and C
F) All of them have the same period.
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