Arno Penzias, born in 1933, German-born American radio engineer who, with American engineer Robert Wilson, was the first to detect the cosmic microwave background radiation. This radiation seems to be evenly distributed throughout the universe, leading scientists to believe that it is the cooling remains of energy released at the big bang, the explosion that released all the matter and energy in the universe. The background radiation represents some of the strongest evidence in favor of the big bang theory. Penzias and Wilson shared half of the 1978 Nobel Prize in physics for their discovery. The other half of the prize went to Soviet physicist Peter Kapitza for his work in low-temperature physics. See also Radio Astronomy.

Penzias was born in Munich, Germany. His parents fled Nazi Germany in 1940 and emigrated to the United States, taking their two young sons with them. Studying at the City College of the City University of New York, Penzias earned his bachelor's degree in physics in 1954. He served in the U.S. Army Signal Corps for two years, then returned to New York. He continued his studies at Columbia University, where he was awarded his master's degree in 1958 and his doctorate in 1962, both in physics.

Since 1961 Penzias has been associated with the Radio Research Laboratories at Bell Laboratories in New Jersey. When Penzias began work at Bell Labs, the laboratory was part of AT&T Corp. Since 1996 the laboratory has been a division of Lucent Technologies, a spin-off company of AT&T. From 1961 to 1972, Penzias was a staff member of the radio research department, and from 1972 to 1976, he was head of the radiophysics research department. In 1976 he became the director of the Radio Research Laboratory, and he served as director of the Communications Sciences Research Division from 1979 to 1981. From 1981 to 1995, Penzias was vice president of research for Bell Labs. He served as vice president and chief scientist from 1995 to 1998. Penzias retired from his vice presidency and chief scientist position in 1998 to work as an advisor and spokesperson for Lucent Technologies.

In addition to his posts in the telecommunications industry, Penzias also concurrently held a series of academic positions. The first of these was as lecturer in the department of astrophysical science at Princeton University in New Jersey from 1967 to 1982. After that, he held many yearlong honorary lecturer positions at diverse institutions, including the National Radio Astronomical Observatory in West Virginia and Stanford University in California.

In 1963 Penzias and Wilson were assigned to trace the source of radio noise that was interfering with the development of a communications program involving satellites. By May 1964 the two physicists had detected a surprisingly high level of radiation at a wavelength of 7.3 cm (2.9 in). The radiation seemed to have no particular source; it was isotropic, or came equally from all directions. Penzias and Wilson excluded all known terrestrial sources of such radiation and still found that the noise they were detecting was one hundred times more powerful than they could account for.

Penzias and Wilson took this result to Robert Dicke, professor of physics at Princeton University. Dicke was interested in microwave radiation and had predicted that this sort of radiation should be present in the universe as a residue of the intense heat associated with the birth of the universe following the big bang. His department was in the process of constructing a radio telescope designed to detect precisely this radiation, at a wavelength of 3.2 cm (1.3 in), when Penzias and Wilson presented their data.

Since Penzias and Wilson’s detection of this radiation, background radiation has been the subject of intense study. The wavelengths at which it exists and its peak intensity very closely match the pattern of radiation that a blackbody, or a perfectly radiating object, would emit at a certain temperature. The temperature that the background radiation seems to represent is just below -270° C (just below -454° F). For cosmologists, the background radiation is the most convincing evidence in favor of the big bang model for the origin of the universe.

Penzias’s later work has been concerned with developments in radio astronomy, instrumentation, satellite communications, and atmospheric physics.