Measuring Radio Signals from Hydrogen.

In 1961 German-American physicist Arno A. Penzias completed work on his Ph.D., studying the use of masers to amplify radio signals, and began work at Bell Laboratories with Robert W. Wilson measuring radio signals from hydrogen in space. They had access there to the world's most sensitive radio telescope, a six-meter horn antenna used to send and receive signals from the passive Echo satellite.

A Constant Noise.

In 1961 the Echo chief engineer E. A. Ohm noted electronic noise in this antenna carefully measured at three kelvins. Penzias and Wilson tried to eliminate the noise without success. They cleaned a family of birds out of the horn and eliminated mechanical vibrations, but a constant three kelvins of noise was always there.

The Big Bang.

Finally, they concluded that the noise came from space itself, from...