FIRAS Overview
FIRAS (Far Infrared Absolute
Spectrophotometer) - The cosmic microwave background (CMB)
spectrum is that of a nearly perfect blackbody with a temperature
of 2.725 +/- 0.002 K. This observation matches the predictions
of the hot Big Bang theory extraordinarily well, and indicates
that nearly all of the radiant energy of the Universe was
released within the first year after the Big Bang.