A family of optimistic intellectuals
Saul Perlmutter was born on September 22, 1959, and grew up in the Mount Airy neighbourhood of Philadelphia. All four of his grandparents were Jewish immigrants who came to America as young adults from Eastern European towns and villages early in the twentieth century. He described them as a generation of poor but optimistic intellectuals who believed education and creativity could build a better world. His maternal grandfather, Samuel Davidson, from Florești in Bessarabia, welded in the shipyards during the Second World War and later ran a sandwich stand, but by vocation was a self-taught scholar and teacher of Yiddish literature and history.
Their only children, Perlmutter’s parents, both became professors: his mother, Felice Davidson Perlmutter, in social work and social administration at Temple University, and his father, Daniel Perlmutter, in chemical engineering at the University of Pennsylvania. On weekends the house filled with friends arguing about politics, films, books and the arts late into the night. One of his sisters, Shira Perlmutter, later became the United States Register of Copyrights.
All the languages
As a boy Perlmutter wanted to learn all the “languages” of the world, music, literature, mathematics, science, architecture and psychology, especially those that seemed universal. He thought everyone needed the missing owner’s manual of the universe, since we all live in it. He attended Quaker schools, Greene Street Friends School and Germantown Friends School, which encouraged creativity, critical thinking and social concern. Music mattered deeply: his violin teacher taught him perfectionism in the service of warm communication, and he has played chamber music and sung in groups all his life, comparing the best scientific teamwork to a string quartet.
At Harvard, from 1977, he considered a double major in physics and philosophy, chose physics, and explored cognitive science and biology on the side. He graduated magna cum laude in 1981 and went to the University of California, Berkeley, for graduate school because it offered so many experimental research groups.
Robot telescopes
At Berkeley Perlmutter joined the eclectic group of the physicist Richard Muller, which followed the tradition of Muller’s mentor Luis Alvarez of chasing interesting problems wherever they led. Perlmutter worked on an automated telescope that searched for exploding stars, supernovae, writing much of the software that let computers spot new supernovae in images and reject false alarms such as asteroids and cosmic rays. For his 1986 PhD he used the same robotic telescope to search for Nemesis, a hypothetical companion star of the Sun proposed to explain periodic mass extinctions on Earth.
By then astronomers had found that one kind of supernova, called Type Ia, explodes with nearly the same brightness every time. That made it a potential cosmic yardstick: compare how bright one looks with how bright it really is, and you know how far away it is. Since the 1930s astronomers had hoped supernovae might one day measure how much the expansion of the universe was slowing down under gravity.
The Supernova Cosmology Project
In late 1987 Perlmutter and his colleague Carl Pennypacker proposed a bold project: build the widest-field digital camera yet used on a large telescope, and write software to search tens of thousands of distant galaxies in a single night for Type Ia supernovae. The Supernova Cosmology Project began in 1988 at Lawrence Berkeley National Laboratory. The early years were hard; in almost two years of scheduled nights at the Anglo-Australian Telescope in Australia, the weather allowed only two and a half nights of good observing. Still, by 1992, when Perlmutter took over as leader, the team had found a supernova more distant than any then known.
The decisive innovation came by 1994. Distant supernovae are rare and fade within weeks, so astronomers could not book time on the world’s great telescopes to study them. Perlmutter’s team learned to guarantee whole batches of newly exploding supernovae, all discovered on a chosen date and still brightening, so that follow-up observations, including with the Hubble Space Telescope, could be scheduled in advance. Looking back, he said the team had expected the project to take three years; three years in, it seemed to have got nowhere, and only after about nine years did the shocking results appear. What kept them going, he said, was the culture of science, which lets people stick with a hard problem far longer than most would, as long as each step brings them closer. Their international collaboration, with members from the United States, France, Sweden, Britain, Chile, Japan and Spain, raced against a rival group, the High-z Supernova Search Team led by Brian Schmidt with Adam Riess.
A universe speeding up
In 1997 the team analysed 42 distant supernovae and found something no one expected. The supernovae were fainter, and therefore farther away, than they should have been if the expansion of the universe were slowing. The expansion was speeding up. Perlmutter’s group announced the evidence in January 1998, and the rival team reported matching results at nearly the same time. Science magazine named the discovery its breakthrough of the year.
The finding implied that something unknown, now called dark energy, pervades all of space and pushes the universe apart. Dark energy is thought to make up about three quarters of the universe, yet no one knows what it is; it has been called the most important unsolved problem in physics. In 2011 Perlmutter received half of the Nobel Prize in Physics, with Schmidt and Riess sharing the other half, “for the discovery of the accelerating expansion of the universe through observations of distant supernovae”. He stressed that the result belonged to two international teams and to ideas from almost every continent and culture.
Teaching the world to think
For general readers, Perlmutter’s most direct contribution may be what he has done since. Struck by how much of science’s strength comes not from facts but from habits of thought, ways scientists avoid fooling themselves that are usually learned only by apprenticeship, he began in 2011 to work with the Berkeley philosopher John Campbell and the psychologist Robert MacCoun on a course to teach those habits to everyone. Their Big Ideas course at Berkeley, Sense and Sensibility and Science, teaches the tools natural and social scientists use to understand the world and to avoid fooling themselves, and shows how to reach decisions together with people whose values differ.
In 2024 the three published Third Millennium Thinking: Creating Sense in a World of Nonsense, turning the course into a book for the public about using the tools scientists use “to stop us from fooling ourselves” in everyday decisions and problem-solving. He argues that science’s real superpower comes from what can look like weakness: a willingness to be wrong, to be only probabilistically sure, and to seek out the people who will disagree with you, because they are your best chance of finding your mistakes. In an age of misinformation, he believes, those habits matter to every citizen.
Science in public service
Perlmutter has continued to lead research on dark energy, including work toward a dedicated space telescope to measure the history of the universe’s expansion far more precisely. He took part in the Berkeley Earth project, which aimed to improve understanding of recent global warming through better analysis of climate data. Since 2021 he has served on the President’s Council of Advisors on Science and Technology.
His other honours include the E. O. Lawrence Award in 2002, the Shaw Prize in Astronomy in 2006, the Gruber Cosmology Prize in 2007 and the Breakthrough Prize in Fundamental Physics in 2015. A supercomputer at the Department of Energy’s National Energy Research Scientific Computing Center is named Perlmutter in his honour.
Jewish roots and private life
Perlmutter’s Jewish heritage is the heritage of Yiddish-speaking Eastern Europe carried into American universities in two generations: grandparents who were shipyard workers and Yiddish teachers, parents who became professors, and a household where social and political concern was a constant theme. In his Nobel autobiography he describes his grandparents’ generation as hoping a rational world would leave behind borders and boundaries to build a better one, an ideal visible in his own internationalism.
He is married to Laura Nelson, an anthropologist at Berkeley; they have a daughter, Noa. He designed a Physics and Music course for Berkeley undergraduates, discovering that music could be a way into some of the most fundamental ideas of physics and even of cosmology, has kept up string-quartet playing and group singing throughout his life, and was even name-checked on the television comedy The Big Bang Theory.
Legacy
Perlmutter’s discovery overturned what astronomers expected about the fate of the cosmos and revealed that most of the universe consists of something science cannot yet explain. It launched a worldwide effort, with new telescopes and satellites, to understand dark energy, and it changed the questions physics asks about space, time and gravity.
His second contribution reaches far beyond astronomy. By distilling the working habits of science into tools that anyone can use, from voters to patients, he is trying to help a whole society reason more clearly and disagree more productively. As he wrote in his Nobel autobiography, the best result science can hope for is not only answers but new, surprising questions about our world.
Sources & further reading
Saul Perlmutter, Biographical, NobelPrize.org · Berkeley Lab’s Saul Perlmutter Wins 2011 Nobel Prize in Physics, Lawrence Berkeley National Laboratory · Press release: The Nobel Prize in Physics 2011, NobelPrize.org · Interview with Saul Perlmutter, Issues in Science and Technology · Third Millennium Thinking (book excerpt), WBUR Here & Now · Saul Perlmutter, Wikipedia · Researched from the sources above and checked against them. Spotted an error? Tell us.
A life of tikkun olam. This is part of tikkun olam, the Jewish idea of repairing the world, and every one of us can add to it.