Physicist Arno Allan Penzias, who fled Nazi Germany as a child and co-discovered cosmic background radiation, a breakthrough that solidified the "Big Bang" theory.
In 1963, two young researchers at Bell Telephone Laboratories began adapting a sophisticated radio antenna for astronomical observations. The antenna, originally intended for satellite communications, had become available after the completion of a satellite communication project. Bell Labs, known for fostering both applied and basic research, offered an ideal environment for such experimental endeavors. Arno Penzias, then 30 and two years into his tenure at Bell Labs, seized the opportunity to use the antenna to search for hydrogen molecules in distant galaxies. He was joined by Robert Wilson, a radio astronomer who had recently joined Bell Labs. To calibrate the antenna for sensitive astronomical observations, the pair aimed it at a region of the sky expected to be free of radio waves. Surprisingly, the antenna consistently detected high levels of "noise"—radio wave disturbances that did not match any identifiable source.
Penzias and Wilson embarked on a systematic effort to identify the source of the noise. They initially suspected external sources, such as satellites, airplanes, or even radio interference from New York City. However, the noise persisted regardless of where the antenna was pointed. Turning their attention inward, they examined the antenna's components for possible flaws, such as unstable parts or components that might emit radio waves. At one point, the researchers suspected the noise might be caused by droppings from a pair of pigeons nesting inside the antenna. The birds were respectfully relocated to a distant area, but they quickly returned, forcing the researchers to take permanent measures to remove them. Following this, Wilson and Penzias thoroughly cleaned the radio telescope, ensuring all possible sources of interference were eliminated. "They subjected its electric circuits to scrutiny comparable to that used in preparing a manned spacecraft," reported the New York Times in a 1965 article. Yet, the mystery of the noise remained unsolved. No matter where they pointed the antenna, the background signal was always present, with a consistent frequency and intensity.
Searching for the source of the noise, they uncovered the origins of the universe. The Bell Labs Holmdel Horn Antenna in 1962, shortly before the research that led to the historic discovery | Source: NASA / SCIENCE PHOTO LIBRARY
Secrets of the Universe
As early as 1948, several physicists led by George Gamow predicted the potential existence of cosmic background radiation – a remnant of the young universe's early activity, shortly after the Big Bang. Their calculations suggested that the formation of matter, occurring about 300,000 years after the Big Bang, when the universe had cooled sufficiently, would have produced radiation at a wavelength of one-thousandth of a millimeter. However, as the universe expanded, this radiation would have stretched over time to a wavelength of approximately one millimeter now, placing it within the range of radio waves.
At that time, the idea that the universe began with a single event—the Big Bang—and has been expanding ever since was far from the scientific consensus. Many researchers adhered to the belief that the universe was stable rather than expanding. The debate persisted into the 1960s, when a group of cosmologists at Princeton University, led by Robert Dicke and James Peebles, independently arrived at conclusions similar to those of Gamow and his colleagues, despite being unaware of their earlier work. Dicke and Peebles argued that the Big Bang would have left an imprint in the form of radio waves with nearly uniform intensity across all directions.
Wilson and Penzias could have dismissed the persistent noise detected by their antenna and proceeded with their planned research. However, the anomaly continued to trouble them. Penzias discussed the issue with a colleague at the Massachusetts Institute of Technology. About two months later, the colleague called him with excitement to share news of a draft paper by Dicke and Peebles. "Suddenly, everything fell into place for Penzias. At last, he understood the source of the noise that had plagued his radio telescope and appreciated how highly significant it was," wrote Simon Singh in his book "The Big Bang". "At long last the mystery of the omnipresent noise had been solved. It was nothing to do with pigeons, dodgy wiring, or New York, but it had everything to do with the creation of the universe."
Penzias promptly contacted Dicke to inform him that he and Wilson had discovered the cosmic background radiation that he and his colleagues had predicted in their paper. In 1965, the findings of both teams were published in back-to-back articles in the Astrophysical Journal: one by Penzias and Wilson detailing the discovery of cosmic background radiation, and the other by the Princeton researchers explaining the theoretical framework. This landmark discovery paved the way for the widespread acceptance of the expanding universe theory. The term "Big Bang", ironically coined by one of the theory's skeptics, gained popularity later.
“Suddenly, everything fell into place”.Penzias (right) and Wilson in front of the radio antenna in New Jersey. | Source: Bell Labs' X Twitter account
A Temporary Job
Arno Penzias was born in Munich on April 26, 1933, just months after the Nazi rise to power in Germany. Despite the increasing danger to his Jewish family—heightened by his father’s Polish citizenship—his early childhood years passed in relative tranquility. His father ran a leather trade business, and the family’s financial situation was fairly stable. However, after Kristallnacht in November 1938, his parents realized the severity of the threat and arranged for six-year-old Arno and his younger brother to be placed on the Kindertransport, an organized rescue effort that brought refugee Jewish children from Nazi-controlled territory to Great Britain. Fortunately, his parents also managed to escape Germany soon after, and a few months later, the reunited family sailed from England to New York.
In the United States, the family faced significantly harsher economic conditions. Both parents took jobs as building maintenance workers in New York City, struggling to make ends meet. Education became Penzias’ pathway out of poverty, and he enrolled in chemical engineering at the City College of New York, which offered subsidized tuition. During his first year, he became fascinated by physics and decided to shift his academic focus, despite the field’s more uncertain career prospects.
After completing his studies, Penzias volunteered for two years of military service in the Signal Corps, the modern equivalent of communication and IT units. His strong academic record and experience as a radar operator earned him a place in a master’s program, followed by a doctoral program at Columbia University. There, he conducted research under Charles Townes, a pioneer of maser technology for controlled microwave emission and a co-developer of the laser—a contribution that later earned Townes the 1964 Nobel Prize in Physics. Penzias constructed a highly sensitive radio receiver based on Townes’ maser, designed to detect radio waves from hydrogen gas clouds in intergalactic space. Although he successfully built the device, the observational results fell short of expectations, leading him to describe the project as “horrible.” Nonetheless, the research earned him a doctorate in physics, which he was awarded in 1961.
With limited job opportunities in radio astronomy, Penzias followed a friend’s suggestion to take a temporary position at Bell Labs. “You can always leave,” the friend assured him. Ultimately, Penzias stayed at this “temporary” job for 37 years.
From escaping Nazi Germany to receiving the Nobel Prize in Physics for uncovering one of the strongest pieces of evidence for the Big Bang.
Arno Penzias | Photo: HANK MORGAN / SCIENCE PHOTO LIBRARY
Science and Politics
Penzias began his career at Bell Labs working on a communication satellite project, where he developed a method to help align ground antennas with satellites by using radio waves from galaxies with known positions. However, his true passion lay in fundamental research, which he managed to pursue with the repurposed antenna. A combination of ingenuity, persistence, and luck led to one of the most significant discoveries in cosmology. In 1978, Wilson and Penzias were awarded the Nobel Prize in Physics for their groundbreaking discovery of cosmic background radiation, jointly with the Russian physicist Pyotr Kapitsa.
The discovery provided strong support for the "Big Bang" theory, but there were still some issues with the theory. One major issue was that the cosmic background radiation appeared uniform in intensity in all directions, which seemed to contradict the asymmetry in the distribution of matter in the universe—the very asymmetry that allowed stars and galaxies to form. This problem was resolved in the 1990s with measurements from the COBE (Cosmic Background Explorer) satellite, which revealed that the radiation was indeed not uniform, solidifying the theory as the leading explanation for the origin of the universe. This discovery earned physicists John Mather and George Smoot the 2006 Nobel Prize in Physics. In 2019, James Peebles was also awarded the Nobel Prize in Physics for predicting the existence of cosmic background radiation and providing a theoretical explanation for Penzias and Wilson's work (Robert Dicke had passed away by then).
The non-uniformity of the background radiation supports the theory of the universe’s creation and expansion. Radiation map provided by the WMAP satellite in 2008 | Source: NASA / WMAP SCIENCE TEAM / SCIENCE PHOTO LIBRARY
Despite his monumental contribution to cosmology, Penzias did not shift his research focus. In the years following the discovery, he continued working with Wilson on their original research, using radio waves to identify hydrogen in space. Later, the two detected the radio wave signatures of numerous other molecules. Penzias remained at Bell Labs in New Jersey until his retirement in 1998. Among his various roles, he served as Vice President for Research for 14 years, a position that required him to step away from active research. "At that point my responsibilities got so large that I think after my elevation to vice president, which is having about 1,000 PhDs working in my organisation and a budget of 100s of millions of dollars, it just stopped being fun to do astronomy," he said in a 2004 Nobel Prize website interview. Over the years, he received numerous awards and honors for his significant contributions to science.
In 1954, while still in his undergraduate studies, Penzias married Anne Barras. The couple had three children, later followed by 12 grandchildren and three great-grandchildren. They divorced in 1995, and a year later, Penzias married Sherry Levit, a businesswoman from California. After his retirement, the couple moved to San Francisco, where Penzias passed away on January 22, 2024, at the age of 90, due to complications from Alzheimer's disease.
In addition to his scientific work, Penzias was active in politics. In 1978, shortly after receiving the Nobel Prize, he traveled to Moscow to lecture on his research to Soviet scientists who had been denied permission to leave the country—many of them Jews seeking to immigrate to Israel. He later helped some of them emigrate.In 1992, he arranged for part of the original equipment from the radio telescope used in his historic discovery to be donated to a museum in Munich, his birthplace. “It was very important to my father to remind them what they lost,” his daughter, Rabbi L. Shifra Weiss-Penzias, said in an interview quoted in the New York Times. “He wanted his work to be a living reminder of the refugees who left and the people who died.”
The antenna that broke boundaries. A video by Bell Labs about the radio telescope and the work of Penzias and Wilson.The antenna that broke boundaries. A video by Bell Labs about the radio telescope and the work of Penzias and Wilson (in English):