Can we see the Big Bang’s afterglow?
The cosmic microwave background, discovered in 1965, is the radiation left over from the Big Bang. It has been mapped in great detail by satellites. Tiny temperature fluctuations reveal the seeds of the Universe’s large-scale structure.
In 1965, radio astronomers Arno. Penzias and Robert Wilson accidentally discovered a faint, almost uniform glow of microwave radiation. This cosmic microwave background (CMB) is the afterglow of the Big Bang. It was produced when the Universe was some 380 000 years old, and had cooled down enough for photons (light particles) to travel freely through space. Tiny deviations from the CMB’s average temperature of -270.4° C are produced by small density fluctuations in the early Universe – the seeds of clusters of galaxies.
The newborn Universe was very hot. It produced a lot of energetic radiation. That radiation has cooled down ever since, but it can still be observed. The cosmic microwave background is the afterglow of the Big Bang.