German-born US radio engineer who in 1964, with radioastronomer Robert Wilson, was the first to detect cosmic background radiation. This radiation had been predicted on the basis of the 'hot Big Bang' model of the origin of the universe. Penzias and Wilson shared the 1978 Nobel Prize for Physics.
Penzias was born in Munich. His parents left Nazi Germany for the USA, and Penzias studied at the City College of New York and Columbia University. In 1961 he joined the staff of the Radio Research Laboratory of the Bell Telephone Company, becoming its director 1976 and vice president of research 1981. Concurrently he has held a series of academic positions at Princeton, Harvard, and from 1975 as professor at the State University of New York ay Stony Brook.
In 1963, Penzias and Wilson were assigned by Bell to the tracing of radio noise that was interfering with the development of a communications programme involving satellites. By May 1964 they had detected a surprisingly high level of microwave radiation which had no apparent source (that is, it was uniform in all directions). The temperature of this background radiation was 3.5K (269.7°C/453.4°F), later revised to 3.1K (270°C/454.1°F).
They took this enigmatic result to physicist Robert Dicke at Princeton, who had predicted that this sort of radiation should be present in the universe as a residual relic 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 when Penzias and Wilson presented their data.
Penzias's later work has been concerned with developments in radioastronomy, instrumentation, satellite communications, atmospheric physics, and related matters.