If astronomers could have turned a receiver toward the heavens in hopes of observing the cosmic microwave radiation 4.5 billion years ago, at the time the solar nebula was forming, what would they have found?
A) They would have seen nothing since the cosmic microwave background had not yet been created.
B) They would have seen the same blackbody curve seen now, with a peak intensity at a wavelength of about 1 mm.
C) They would have seen a blackbody curve of the same shape seen now but with a peak intensity at a wavelength shorter than 1 mm.
D) They would have seen a blackbody curve of the same shape seen now but with a peak intensity at a wavelength longer than 1 mm.

Question

Quizplus · Accepted Answer

The cosmic microwave background (CMB) radiation is the afterglow of the Big Bang, and as the universe expands, this radiation cools down. 4.5 billion years ago, the universe was younger and hotter, so the peak intensity of the CMB would have been at a shorter wavelength than it is now.

If Astronomers Could Have Turned a Receiver Toward the Heavens