Discovery of cosmic microwave background radiation

The accidental discovery of cosmic microwave background radiation in 1964 is a major development in modern physical cosmology. Although predicted by earlier theoretical work around 1950, it was first discovered accidentally by American radio astronomers Arno Penzias and Robert Woodrow Wilson as they experimented with the Holmdel Horn Antenna. The discovery was important evidence for a hot early Universe (big bang theory) and was evidence against the rival steady state theory. In 1978, Penzias and Wilson were awarded the Nobel Prize for Physics for their joint discovery.

By the middle of the 20th century, cosmologists had developed two different theories to explain the creation of the universe. Some supported the steady-state theory, which states that the universe has always existed and will continue to survive without noticeable change. Others believed in the Big Bang theory, which states that the universe was created in a massive explosion-like event billions of years ago (later to be determined as 13.72 billion)(13 720 million).

The first published recognition of the cosmic microwave background (CMB) radiation as a detectable phenomenon appeared in a brief paper by Soviet astrophysicists A. G. Doroshkevich and Igor Novikov, entitled "Mean Density of Radiation in the Metagalaxy and Certain Problems in Relativistic Cosmology", in the spring of 1964.

Working at Bell Labs in Holmdel, New Jersey, in 1964, Arno Penzias and Robert Wilson were experimenting with a supersensitive, 6 meter (20 ft) horn antenna originally built to detect radio waves bounced off Echo balloon satellites. To measure these faint radio waves, they had to eliminate all recognizable interference from their receiver. They removed the effects of radar and radio broadcasting, and suppressed interference from the heat in the receiver itself by cooling it with liquid helium to −269 °C, only 4 K above absolute zero.

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