Question

Question #73543

Answer 1

I think that Background Radiation normally refers to the radiation left after the Big Bang and permeating our entire Universe. It was discovered in 1964 by A. A. Penzias and R. W. Wilson working at Bell Laboratories.

At the moment, if I remember correctly, it should be in the 2 mm wavelength region (microwave). It now represents, basically, the same radiation emitted by hot bodies.

One explanation of its origin is that the original "fireball" of the Big Bang produced radiation (very "hot" and so at very high frequency) that with the expansion of the Universe became gradually cooler up to the present time (representing `3 K`) and tending towards the absolute zero and towards longer wavelengths.

[Ref. H. C. Ohanian, Physics, 2nd ed.. London WW Norton & Co., 1985]