Arno A. Penzias, 90, Dies; Nobel Physicist Confirmed Big Bang Theory

Arno A. Penzias, whose astronomical probes yielded incontrovertible evidence of a dynamic, evolving universe with a clear point of origin, confirming what became known as the Big Bang theory, died on Monday in San Francisco. He was 90.

His death, in an assisted living facility, was caused by complications of Alzheimer’s disease, his son, David, said.

Dr. Penzias (pronounced PEN-zee-as) shared one-half of the 1978 Nobel Prize in Physics with Robert Woodrow Wilson for their discovery in 1964 of cosmic microwave background radiation, remnants of an explosion that gave birth to the universe some 14 billion years ago. That explosion, known as the Big Bang, is now the widely accepted explanation for the origin and evolution of the universe. (A third physicist, Pyotr Kapitsa of Russia, received the other half of the prize, for unrelated advances in developing liquid helium.)

Until Dr. Penzias and Dr. Wilson published their observations, the Big Bang theory competed with the steady-state theory, which envisioned a more static, timeless expanse growing into infinite space, with new matter formed to fill the gaps.

Dr. Penzias and Dr. Wilson’s discovery finally settled the debate. Yet it was the serendipitous product of a different investigation altogether.

In 1961, Dr. Penzias joined AT&T’s Bell Laboratories in Holmdel, N.J., with the intention of using a radio antenna, which was being developed for satellite communications, as a radio telescope to make cosmological measurements.

“The first thing I thought of was — study the galaxy in a way that no one else had been able to do,” he said in a 2004 interview with the Nobel Foundation.

In 1964, while preparing the antenna to measure the properties of the Milky Way galaxy, Dr. Penzias and Dr. Wilson, another young radio astronomer who was new to Bell Labs, encountered a persistent, unexplained hiss of radio waves that seemed to come from everywhere in the sky, detected no matter which way the antenna was pointed. Perplexed, they considered various sources of the noise. They thought they might be picking up radar, or noise from New York City, or radiation from a nuclear explosion. Or might pigeon droppings be the culprit?

Examining the antenna, Dr. Penzias and Dr. Wilson “subjected its electric circuits to scrutiny comparable to that used in preparing a manned spacecraft,” Walter Sullivan wrote in The New York Times in 1965. Yet the mysterious hiss remained.

The cosmological underpinnings of the noise were finally explained with help from physicists at Princeton University, who had predicted that there might be radiation coming from all directions left over from the Big Bang. The buzzing, it turned out, was just that: a cosmic echo. It confirmed that the universe wasn’t infinitely old and static but rather had begun as a primordial fireball that left the universe bathed in background radiation.

The discovery, Dr. Penzias said years later, intensified his interest in astronomy. He and Dr. Wilson went on to detect dozens of types of molecules in interstellar clouds where new stars are formed.

“Their discovery marked a transition between a period in which cosmology was more philosophical, with very few observations, and a golden age of observational cosmology,” Paul Halpern, a physicist at St. Joseph’s University in Philadelphia and the author of “Flashes of Creation: George Gamow, Fred Hoyle, and the Great Big Bang Debate,” said in a phone interview.

The discovery not only helped cement the cosmos’s grand narrative; it also opened a window through which to investigate the nature of reality — all as a result of that vexing hiss first heard 60 years ago by a couple of junior physicists looking for something else.

Arno Allan Penzias was born on April 26, 1933, in Munich to Jewish parents, Karl and Justine (Eisenreich) Penzias. Dr. Penzias would later point out, to just about anyone he met, that his birth coincided to the day and place with the establishment of the Gestapo, the German secret police.

His father was a leather wholesaler; his mother, who managed the home, had converted to Judaism from Roman Catholicism in 1932.

In the fall of 1938, the Penzias family was arrested and put on a train for deportation to Poland.

“Fortunately for us, the Poles stopped accepting Jews just before our train reached the border,” Dr. Penzias said in a eulogy at his mother’s funeral in 1991. The train returned to Munich. In late spring 1939, 6-year-old Arno and his brother, Gunter, 5, were put on a train as part of the Kindertransport, the British rescue effort that brought some 10,000 children to England.

His mother instructed Arno to take care of his brother. “I only realized much later that she didn’t know if she would ever see either one of us again,” he said in his eulogy.

Gunter Penzias recalled over the phone: “Each of us was given a large box of chocolates. I fell asleep on the train, and mine was stolen. So Arno shared his with me.”

The boys’ parents managed to leave Germany for England, and the family arrived in New York City in 1940. Karl and Justine found work as superintendents in a series of apartment buildings in the Bronx, giving the family places to live.

Dr. Penzias attended Brooklyn Technical High School and “sort of drifted into chemistry,” he told The New Yorker in 1984. He entered the City College of New York in 1951 intending to study chemistry, but he found that he had already learned much of the material. After one of his professors assured him that he could make a living as a physicist, he switched majors, graduating in 1954. That year, he married Anne Barras, a student at Hunter College. They divorced in 1995.

After two years as a radar officer in the Army Signal Corps, he entered graduate school at Columbia University, where he earned both his master’s and doctoral degrees in physics, the latter in 1962.

But Dr. Penzias’s path to stumbling onto the answer to one of humanity’s most central questions started a year earlier, when he joined Bell Laboratories as a member of its radio research group in Holmdel.

There, he saw the potential of AT&T’s new satellite communications antenna, a giant radio telescope known as the Holmdel Horn, as a tool for cosmological observation. In teaming up with Dr. Wilson in 1964 to use the antenna, Dr. Wilson said in a recent interview, one of their goals was to advance the nascent field of radio astronomy by accurately measuring several bright celestial sources.

Soon after they started their measurements, however, they heard the hiss. They spent months ruling out possible causes, including pigeons.

“The pigeons would go and roost at the small end of the horn, and they deposited what Arno called a white dielectric material,” Dr. Wilson said. “And we didn’t know if the pigeon poop might have produced some radiation.” So the men climbed up and cleaned it out. The noise persisted.

It was finally Dr. Penzias’s fondness for chatting on the telephone that led to a fortuitous breakthrough. (“It was a good thing he worked for the phone company, because he liked to use their instrument,” Dr. Wilson said. “He talked to a lot of people.”)

In January 1965, Dr. Penzias dialed Bernard Burke, a fellow radio astronomer, and in the course of their conversation he mentioned the puzzling hiss. Dr. Burke suggested that Dr. Penzias call a physicist at Princeton who had been trying to prove that the Big Bang had left traces of cosmological radiation. He did.

Intrigued, scientists from Princeton visited Dr. Penzias and Dr. Wilson, and together they made the connection to the Big Bang. Theory and observation were then brought together in a pair of papers published in 1965.

Dr. Penzias stayed at Bell Labs for nearly four decades, with 14 years as vice president of research. His interests reached well beyond science, into business, art, technology and politics. After his 1978 Nobel Prize acceptance speech in Stockholm, he flew directly to Moscow to give a lecture about his findings to a group of refusenik scientists. He later helped several of them leave the Soviet Union.

In 1992, Dr. Penzias arranged for the donation of the Holmdel Horn’s receiver and calibration equipment to the Deutsches Museum in Munich, where it remains as part of a permanent exhibition.

“It was very important to my father to remind them what they lost,” his daughter, Rabbi L. Shifra Weiss-Penzias, said in an interview. “He wanted his work to be a living reminder of the refugees who left and the people who died.”

Dr. Penzias married Sherry Levit, a Silicon Valley executive, in 1996. In addition to his daughter; his son, David; and his brother, Gunter, Dr. Penzias is survived by his wife; another daughter, Mindy Dirks; a stepson, Carson Levit; a stepdaughter, Victoria Zaroff; 12 grandchildren; and three great-grandchildren.

Soon after the announcement of the Nobel Prize, President Jimmy Carter sent a congratulatory telegram to Dr. Penzias. He replied, “I came to the United States 39 years ago as a penniless refugee from Nazi Germany,” adding that for him and his family, “America has meant a haven of safety as well as a land of freedom and opportunity.”