The cosmic background radiation that was left over after the Big Bang of the universe and that pervades all observable space has an effective blackbody temperature of approximately
A) 273 K.
B) 0 K.
C) 10 K.
D) 3 K.

Question

Quizplus · Accepted Answer

The cosmic background radiation, also known as the Cosmic Microwave Background (CMB), has an effective blackbody temperature of approximately 2.725 K, which is very close to 3 K. This radiation is a remnant from the early universe, specifically from a time about 380,000 years after the Big Bang, when the universe cooled enough for electrons and protons to combine into neutral hydrogen atoms, allowing photons to travel freely.

The Cosmic Background Radiation That Was Left Over After the Big