Arno Allan Penzias

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Lore & Background

Penzias was born in Munich, Germany, the son of Justine (née Eisenreich) and Karl Penzias, who ran a leather business. At age six, he and his brother Gunther were among the Jewish children evacuated to Britain as part of the Kindertransport rescue operation. His parents also fled Nazi Germany, first for the UK, then for the US, and the family settled in the Bronx, New York City, in 1940. Penzias became a US citizen in 1946. After graduating from Brooklyn Technical High School in 1951, he enrolled at the City College of New York to study chemistry, but changed majors to physics and graduated in 1954, ranked near the top of his class. He then served in the U.S. Army Signal Corps as a radar officer for two years. His radar work led to a research assistantship at the Columbia University Radiation Laboratory, where he worked under Charles H. Townes. Penzias enrolled as a graduate student at Columbia University in 1956, earning a master's degree and a PhD in physics, the latter in 1962. At Bell Labs in Holmdel Township, New Jersey, he and Robert Woodrow Wilson built ultra-sensitive cryogenic microwave receivers for radio astronomy. In 1964, on building their most sensitive antenna/receiver system, the pair encountered radio noise they could not explain. It was far less energetic than radiation from the Milky Way and isotropic, so they assumed terrestrial interference. They examined the microwave horn antenna and found it full of bat and pigeon droppings, which Penzias described as 'white dielectric material.' After removing the dung buildup, the noise remained. Penzias contacted Robert H. Dicke, who suggested it might be the background radiation predicted by some cosmological theories. They agreed to publish side-by-side letters in the Astrophysical Journal, with Penzias and Wilson describing their observations and Dicke suggesting the interpretation as the cosmic microwave background (CMB), the radio remnant of the Big Bang. This proved to be landmark evidence for the Big Bang and confirmed predictions by Ralph Asher Alpher, Robert Herman, and George Gamow.

Reader's Guide

Arno Penzias's significance rests on his discovery of the cosmic microwave background radiation with Robert Woodrow Wilson, which provided landmark evidence for the Big Bang theory. Working at Bell Labs in Holmdel Township, New Jersey, they built ultra-sensitive cryogenic microwave receivers. In 1964, they detected unexplained isotropic radio noise that persisted even after removing bat and pigeon droppings from their antenna. Penzias contacted Robert H. Dicke, who suggested it was the cosmic microwave background, the radio remnant of the Big Bang. They published side-by-side letters in the Astrophysical Journal. This discovery confirmed predictions made by Ralph Asher Alpher, Robert Herman, and George Gamow in the 1940s and 1950s. Penzias and Wilson shared the 1978 Nobel Prize in Physics for this work, with Pyotr Kapitsa receiving the other half for unrelated low-temperature physics. Penzias was elected a Fellow of the American Academy of Arts and Sciences and the National Academy of Sciences in 1975, and received the Henry Draper Medal in 1977. In 2019, the Nürnberger Astronomische Gesellschaft e.V. inaugurated a 3 m radio telescope at the Regiomontanus-Sternwarte in Nuremberg, dedicated to Penzias. In 2023, the Radio Club of America announced the Dr. Arno A. Penzias Award for Contributions to Basic Research in the Radio Sciences.

Did You Know?

• Penzias and his brother Gunther were evacuated from Nazi Germany to Britain via the Kindertransport when he was six years old.
• The unexplained radio noise Penzias and Wilson detected in 1964 was initially thought to be interference from New York City or pigeon droppings in their antenna.
• Penzias described the pigeon droppings in their microwave horn antenna as 'white dielectric material.'
• Penzias earned his PhD in physics from Columbia University in 1962, after working under Charles H. Townes, who later invented the maser.
• On September 11, 2023, the Radio Club of America announced the Dr. Arno A. Penzias Award for Contributions to Basic Research in the Radio Sciences.