What temperature has the Big Bang has cooled to by now?
A) About 3,000 K
B) 5,800 K
C) About 300 K
D) Just over 2.7K
E) 1.4 K

Question

Quizplus · Accepted Answer

The Big Bang has cooled to just over 2.7K due to the expansion of the universe, which causes a decrease in temperature via adiabatic cooling. This temperature is known as the cosmic microwave background radiation, which can be detected throughout the cosmos.

What Temperature Has the Big Bang Has Cooled to by Now