What was the approximate temperature of the universe at the time when the universe became transparent to radiation?
A) 30 billion K
B) 3000 K
C) 3 K
D) 300,000 K

Question

Quizplus · Accepted Answer

At the time when the universe became transparent to radiation, the temperature was approximately 3000 K. This is known as the epoch of recombination, which occurred about 380,000 years after the Big Bang. At this point, the universe had cooled enough for neutral atoms to form, allowing radiation to travel freely through the universe, creating the cosmic microwave background radiation we observe today.

What Was the Approximate Temperature of the Universe at the Time