If the wavelength of the background radiation peaked at 1 µm at the time of recombination, how old was the universe then compared with its age today?
A) one second old
B) 1/100th of a second old
C) 1/1,000th of a year old
D) 3,000 years old
E) several hundred thousand years old

Question

Quizplus · Accepted Answer

The peak wavelength of the cosmic microwave background radiation at recombination corresponds to a time when the universe was several hundred thousand years old, as this was the era when atoms first formed and the universe became transparent to radiation.

If the Wavelength of the Background Radiation Peaked at 1