Rainer Weiss obituary: Nobel prizewinning physicist

Early in the American morning on September 14, 2015, researchers made a discovery that would advance the field of astrophysics and promise to deepen our understanding of the universe.

On holiday in Maine, Rainer Weiss logged on to his computer, saw the news and yelled “My God!” The observatory he helped to build had registered the “chirp” that he had longed for: a faint signal converted into an audible sound representing a cataclysmic crash that rippled through the cosmos. The triumph earned him the Nobel prize in physics.

The Laser Interferometer Gravitational-Wave Observatory (Ligo), with its vast installations nearly two thousand miles apart, had spotted gravitational waves from the last fraction of a second of a ferocious clash of two merging black holes some 1.3 billion years ago. Predicted a hundred years before by Albert Einstein in his general theory of relativity, the waves are ripples in space-time, the four-dimensional “fabric of the universe”, caused by violent events such as supernovas and collisions of neutron stars. Detecting them gives astrophysicists new tools for observing the universe.

Funded by the United States government at a cost of more than $1.1 billion (about £800 million today) and jointly operated by the Massachusetts Institute of Technology (MIT) and the California Institute of Technology (Caltech), Ligo began operating in 2002 after eight years of construction with the goal of perceiving processes that, despite their force, are extraordinarily tiny once their effects arrive on Earth. “By the time gravitational waves from Ligo’s first detection reached us, the amount of space-time wobbling they generated was 10,000 times smaller than the nucleus of an atom,” the observatory noted.

Einstein came to doubt whether gravitational waves would ever be measured. “It would have been wonderful to watch Einstein’s face had we been able to tell him,” Weiss remarked after the finding was publicly announced in February 2016.

The observation was not only a validation of Einstein’s theory but of the work of Weiss, a German-born American MIT physics professor who was a central figure in the conception and development of Ligo, having designed a laser antenna to detect gravitational waves and built a prototype in 1972.

Feats of design and engineering, the interferometers in Louisiana and Washington state each consist of two 2.5 mile-long antennae fitted with laser beams that travel along vacuum chambers that extend like arms in an “L” shape. The beams of light reflect off mirrors at the end of the tubes and recombine to generate patterns, allowing scientists to track minuscule changes in length caused by the squeezing and stretching of space-time as gravitational waves reach our planet. Ligo is, according to its operators, akin to the most precise ruler in the world, capable of measuring on scales ten thousand trillion times smaller than a human hair.

Securing significant public funding for such an esoteric venture was predictably tricky. “Everybody thought we were out of our minds,” Weiss recalled. The sensitive and delicate equipment required extensive upgrades to improve performance and proved vulnerable to external damage. Weiss walked along the chambers and found cracks and other flaws caused by rodents, wasps and black widow spiders.

Ligo evolved into a project involving a thousand people. The 2017 Nobel was awarded to three, for their “decisive contributions” to the observatory and to gravitational wave detection: Weiss received a half share, with the rest allotted to the Caltech physicists Barry Barish and Kip Thorne.

Weiss, Thorne — an affable, Utah-born friend of Stephen Hawking who was the science adviser for the Christopher Nolan film Interstellar — and Ronald Drever, a Scottish scientist described by Weiss as a “scientific Mozart”, were dubbed the original “troika” for their early efforts. Barish, a gifted manager born in Omaha, joined Ligo in the mid-Nineties and guided it to fruition after some turbulence.

Personality clashes were easy to detect. Weiss, a collaborative and pragmatic New Yorker, supported recruiting Drever from the University of Glasgow. While brilliant, Drever’s propensity for independent thought did not always delight his colleagues. An entrance to his office was bricked up to make it harder for him to bother the group’s secretary and he was forced off the project in 1992 after falling out with Rochus Vogt, the head of Ligo at the time. Drever (obituary, March 18, 2017) later suffered from dementia and died seven months before the Nobel was announced, making him ineligible for the prize.

Weiss uses a prop as he makes the gravitational waves announcement in Washington DC in February 2016

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Rainer “Rai” Weiss was born in Berlin in 1932. His father, Frederick, was a neurologist and a Jewish communist who was abducted by a “Nazi gang”, Weiss said, after speaking out against Nazis at his hospital. He was released after lobbying by Rainer’s mother, Gertrude Loesner, an actress and a Protestant. The family then moved to Prague. On holiday in a hotel in the Tatras in 1938 they adjusted the dials on an old wooden radio to hear Neville Chamberlain’s voice clearly after the Munich Agreement was signed. Realising the ominous implications for Czechoslovakia, the family emigrated to the US in January 1939.

They settled in New York City, where Rainer pursued his passions for music and tinkering with gadgets, combining the two by acquiring cheap military surplus electronic equipment and making and modifying amplifiers, loudspeakers, ham radio transmitters and FM radio receivers.

His father, who became a psychoanalyst and saw patients in the family’s apartment, rebuked him for playing music too loudly. But the teenager was soon invited to build hi-fi sets for his father’s friends. A piano player and a fan of classical music, Weiss grew irked by distortion from scratchy 78 rpm records, a hiss that he found especially bothersome during slow movements while listening to Beethoven. “I started life with one ambition. I wanted to make music easier to hear,” he told the scientist and author Janna Levin.

Aiming to acquire specialist knowledge for his goal of improving sound quality, Weiss enrolled at MIT to study electrical engineering but found the curriculum too rigid and switched to physics. However, distracted by lovesickness from a failed long-distance relationship with a student in Illinois, he failed his studies and “flunked out” in 1953. He found a way to stay at MIT, securing a role as a technician at the Atomic Beam Laboratory, where a professor, Jerrold Zacharias, took him under his wing. Weiss’s hands-on electrical skills were valuable as they worked on atomic clocks.

Weiss was allowed to resume his undergraduate degree then completed a PhD in 1962. He enjoyed a formative spell at Princeton under the prominent physicist Robert Dicke before returning to MIT as a faculty member in the mid-Sixties, where he started a laboratory focused on cosmology and gravitation. Before long he applied his experimental talents and boyhood interest in instrumentation and background noise reduction to the challenge of gravitational wave detection.

In 1959 he married Rebecca Young, a plant physiologist at Harvard who became a children’s librarian. She survives him along with their children, Sarah, an ethnomusicologist, and Benjamin, an art historian and museum curator, and a sister, Sybille, who became a playwright.

Weiss also had a hand in another Nobel-winning endeavour. He chaired the science working group for the Nasa Cosmic Background Explorer project. The satellite operated from 1989 to 1993 on a mission to map and measure cosmic background radiation. Its findings provided evidence to support the big-bang theory and secured the 2006 Nobel prize for physics for two of its scientists.

His turn would come a little over a decade later. The Nobel was one of many prizes awarded to Weiss to mark the fulfilment of a near 50-year quest. “It’s a spectacular signal,” he told MIT News after the initial detection. “This is the first real evidence that we’ve seen now of high-gravitational field strengths: monstrous things like stars, moving at the velocity of light, smashing into each other and making the geometry of space-time turn into some sort of washing machine.”

Rainer Weiss, Nobel prizewinning physicist, was born on September 29, 1932. He died on August 25, 2025, aged 92