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)100 million years after the Big Bang, 1 million years after the Big Bang, today
B)today, 100 million years after the Big Bang, 1 million years after the Big Bang
C)1 million years after the Big Bang, 100 million years after the Big Bang, today
D)today, 1 million years after the Big Bang, 100 million years after the Big Bang

Question

Quizplus · Accepted Answer

The peak intensity of the cosmic background radiation corresponds to a certain wavelength, which is determined by the temperature of the universe at that time. As the universe cools down, the peak intensity moves to longer wavelengths (or lower frequencies). Therefore, the earlier the time, the shorter the wavelength of the peak intensity. According to the Big Bang theory, the universe was much hotter and denser in the past, so the temperature was higher and the peak intensity was at shorter wavelengths. Among the given options, choice C is the correct ranking, with 1 million years after the Big Bang having the shortest wavelength, followed by 100 million years after the Big Bang, and then today, which has the longest wavelength.

Rank These Times Based on the Wavelength of the Peak