Penzias, Arno Allan
(1933– ) US astrophysicist: discovered the 3 K microwave background radiation.
A refugee from Nazi Germany, Penzias was educated in New York and joined Bell Telephones in 1961.
In 1948 and R Herman (1914–97) hypothesized that the radiation released during the ‘Big Bang’ at the creation of the universe ought to have permeated the universe and progressively cooled, to a present-day temperature of about 5 K. In 1964 and P J Peebles (1935– ) at Princeton repeated and extended this theoretical work. At the same time, but unknown to them, Penzias and his colleague were exploring the Milky Way with a radio telescope having a 6 m horn reflector at the Bell Telephone Laboratories in New Jersey, a mile or two away. Working at a wavelength of 7 cm they found more radio noise than they had expected, or could account for from any known terrestrial source (they even excluded the effect of pigeon droppings on the radio telescope’s surface). The signal was equally strong from all directions (including apparently empty sky), and corresponded to that emitted by a black body at about 3.5 K. Their discovery provided some of the strongest evidence for the ‘Big Bang’ theory for the origin of the universe, and is arguably the most important discovery, bearing on cosmology, made in the 20th-c. Penzias and Wilson were awarded the Nobel Prize for physics in 1978.
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