Saul Perlmutter

Saul Perlmutter
Born	Saul Perlmutter 22 9, 1959
Birthplace	Champaign-Urbana, Illinois, U.S.
Nationality	American
Occupation	Astrophysicist, professor
Title	Franklin W. and Karen Weber Dabby Chair in Physics
Employer	University of California, Berkeley; Lawrence Berkeley National Laboratory
Known for	Discovery of the accelerating expansion of the universe, dark energy
Education	University of California, Berkeley (PhD)
Spouse(s)	Laura Nelson
Children	1
Awards	Nobel Prize in Physics (2011), Shaw Prize in Astronomy (2006), Breakthrough Prize in Fundamental Physics (2015)
Website	[http://supernova.lbl.gov/ Official site]

Saul Perlmutter (born September 22, 1959) is an American astrophysicist and professor of physics at the University of California, Berkeley, where he holds the Franklin W. and Karen Weber Dabby Chair. He also serves as head of the International Supernova Cosmology Project at the Lawrence Berkeley National Laboratory. Perlmutter is known for his leadership of one of two research teams that, in the late 1990s, independently discovered that the expansion of the universe is accelerating — a finding that upended prevailing assumptions in cosmology and implied the existence of a mysterious force now termed dark energy. For this discovery, he shared the 2011 Nobel Prize in Physics with Brian P. Schmidt and Adam Riess. He also shared the 2006 Shaw Prize in Astronomy and the 2015 Breakthrough Prize in Fundamental Physics with the same colleagues. A member of the National Academy of Sciences, the American Academy of Arts and Sciences, and the American Philosophical Society, Perlmutter was appointed to the President's Council of Advisors on Science and Technology (PCAST) by President Joe Biden in 2021. In recent years, Perlmutter has become an advocate for applying scientific reasoning to broader societal challenges, co-authoring the book Third Millennium Thinking with social psychologist Robert MacCoun and philosopher John Campbell.

Early Life

Saul Perlmutter was born on September 22, 1959, in Champaign-Urbana, Illinois, into a family with strong academic and cultural roots. His father, Daniel D. Perlmutter, was a chemical engineering professor at the University of Pennsylvania, and his mother, Felice Perlmutter, was a professor of social administration at Temple University and later at Bryn Mawr College. His sister, Shira Perlmutter, went on to a career in intellectual property law.

The Perlmutter family moved to Philadelphia when Saul was young, and he grew up in the city's intellectual milieu. The family had ties to Yiddish culture and Jewish intellectual traditions; a 1989 article in The Philadelphia Inquirer noted the family's involvement with Jewish cultural organizations. Perlmutter attended elementary and secondary school in the Philadelphia area, where he demonstrated early aptitude in science and mathematics.

Growing up in a household where both parents held academic positions, Perlmutter was immersed in an environment that valued rigorous inquiry and intellectual curiosity from a young age. This upbringing would later inform not only his scientific career but also his broader advocacy for scientific thinking as a tool for addressing societal problems.

Education

Perlmutter attended Harvard University as an undergraduate, earning his Bachelor of Arts degree in 1981. He then pursued graduate studies at the University of California, Berkeley, where he worked under the supervision of physicist Richard A. Muller. His doctoral dissertation, titled An Astrometric Search for a Stellar Companion to the Sun, explored the possibility of detecting a hypothetical companion star to the Sun through precise astrometric measurements. He completed his PhD in 1986. Following the completion of his doctorate, Perlmutter remained at Berkeley and the Lawrence Berkeley National Laboratory, where he would build his career and eventually lead the research that transformed modern cosmology.

Career

The Supernova Cosmology Project

After completing his PhD at Berkeley in 1986, Perlmutter joined the staff of the Lawrence Berkeley National Laboratory (LBNL), where he began developing techniques for the systematic discovery and study of distant Type Ia supernovae. In the late 1980s and early 1990s, he founded and led what became known as the Supernova Cosmology Project (SCP), an international collaboration of researchers dedicated to using Type Ia supernovae as "standard candles" to measure cosmological distances and, ultimately, to determine the rate at which the expansion of the universe was changing over time.

Type Ia supernovae are thermonuclear explosions of white dwarf stars that, because of their relatively uniform peak luminosity, can be used to estimate the distances to far-away galaxies. By comparing the observed brightness of distant supernovae with their known intrinsic luminosity, and correlating this with the redshift of the host galaxies, Perlmutter's team aimed to measure the deceleration parameter of the universe — that is, the rate at which the cosmic expansion was expected to be slowing down due to the gravitational pull of matter.

Early progress reports from the Berkeley group documented their collaboration with the Anglo-Australian Observatory to search for high-redshift supernovae. By the mid-1990s, the SCP had developed a reliable method for discovering batches of supernovae on a predetermined schedule, a technique that revolutionized the field. Previous efforts to find distant supernovae had been sporadic and opportunistic; Perlmutter's approach involved scheduling telescope time in advance and then searching wide fields of sky during two observing windows separated by a few weeks, virtually guaranteeing the discovery of multiple supernovae at cosmological distances.

A key early milestone was the discovery of what was then the most distant supernova ever observed, which the team reported as part of their quest to measure the cosmological density parameter Ω. The team also published findings on a supernova explosion observed at half the age of the universe and its cosmological implications.

Discovery of the Accelerating Expansion of the Universe

The Supernova Cosmology Project's most consequential result came in 1998. After analyzing observations of dozens of distant Type Ia supernovae, Perlmutter and his team found that the supernovae were dimmer than expected — indicating that they were farther away than models predicted for a universe that was decelerating. The data were consistent with a universe whose expansion was not slowing down but, contrary to all expectations, was accelerating.

This finding was independently confirmed by a rival team, the High-z Supernova Search Team, led by Brian P. Schmidt and Adam Riess. The convergence of the two independent results provided strong evidence for what was, at the time, an astonishing conclusion: approximately 70 percent of the energy content of the universe consists of a previously unknown form of energy — dubbed "dark energy" — that exerts a repulsive gravitational effect, driving galaxies apart at an ever-increasing rate.

Perlmutter described the discovery's impact in an article for Scientific American, outlining how the observations of distant supernovae had revealed a "dark universe" in which the dominant component of cosmic energy was entirely unknown and unexplained by existing physics. The discovery has been described as one of the most important findings in the history of cosmology, fundamentally altering scientists' understanding of the composition, fate, and evolution of the universe.

The SCP also contributed to measurements of the distant Type Ia supernova rate, further refining the tools and data that underpin modern observational cosmology. The project's data were also used in the Supernova Legacy Survey, which provided precision measurements of the cosmological parameters Ω_M and Ω_Λ.

Academic Career at UC Berkeley

Throughout his career, Perlmutter has held a dual appointment as a professor of physics at the University of California, Berkeley, and a senior scientist at the Lawrence Berkeley National Laboratory. He was awarded the Franklin W. and Karen Weber Dabby Chair in Physics at Berkeley. At LBNL, he heads the Supernova Cosmology Project, which continues to investigate the nature of dark energy using increasingly precise supernova observations and other cosmological probes.

Perlmutter has maintained an extensive publication record in astrophysics and cosmology, with research spanning supernova discovery techniques, cosmological parameter estimation, and the properties of dark energy.

Science Communication and Public Engagement

In addition to his research, Perlmutter has increasingly focused on promoting scientific thinking as a means of addressing complex societal problems. In 2024, he co-authored the book Third Millennium Thinking: Creating Sense in a World of Nonsense with social psychologist Robert MacCoun and philosopher John Campbell. The book argues that the tools and habits of scientific reasoning — including embracing uncertainty, questioning assumptions, and demanding evidence — can help individuals and societies navigate misinformation, polarization, and other contemporary challenges.

In interviews and public appearances promoting the book, Perlmutter has emphasized the importance of maintaining skepticism and intellectual humility, even — or especially — in the age of artificial intelligence. Speaking to Business Insider in December 2025, he cautioned that AI tools can create a "false sense of confidence" and urged users to practice constant error-checking and not allow automated systems to replace critical thinking. In a separate interview covered by the Korean newspaper Chosun Ilbo, Perlmutter advised audiences to distrust experts who present themselves as overly confident, arguing that genuine scientific understanding involves acknowledging what remains unknown.

Policy Advising

In September 2021, President Joe Biden appointed Perlmutter to the President's Council of Advisors on Science and Technology (PCAST), a body that advises the President of the United States on science, technology, and innovation policy. He was appointed alongside UC Berkeley colleague Inez Fung, a climate scientist. His service on PCAST reflects a broader engagement with science policy at the national level, bringing the perspective of fundamental physics research to discussions of government priorities in science and technology.

Personal Life

Saul Perlmutter is married to Laura Nelson, an anthropologist. The couple has one child. He resides in the San Francisco Bay Area, near the University of California, Berkeley campus and the Lawrence Berkeley National Laboratory.

Perlmutter's sister, Shira Perlmutter, has had a career in intellectual property law and has served as the Register of Copyrights and Director of the United States Copyright Office.

Recounting the moment he learned of his Nobel Prize in an interview with Harvard Alumni, Perlmutter noted that very few phone calls that come in the middle of the night are good news — except for the one informing the recipient that they have won a Nobel Prize.

Recognition

Perlmutter has received numerous awards and honors for his contributions to astrophysics and cosmology:

• Ernest Orlando Lawrence Award (2002) — awarded by the United States Department of Energy for outstanding contributions in research and development.
• Fellow of the American Association for the Advancement of Science (2003) — elected in recognition of his scientific contributions.
• Shaw Prize in Astronomy (2006) — shared with Brian P. Schmidt and Adam Riess for the discovery of the accelerating expansion of the universe.
• Gruber Prize in Cosmology (2007) — shared with the Supernova Cosmology Project and the High-z Supernova Search Team.
• Nobel Prize in Physics (2011) — shared with Brian P. Schmidt and Adam Riess "for the discovery of the accelerating expansion of the universe through observations of distant supernovae." The Royal Swedish Academy of Sciences noted that the three laureates had "studied several dozen exploding stars, called supernovae, and discovered that the universe is expanding at an ever-accelerating rate."
• Breakthrough Prize in Fundamental Physics (2015) — shared with Schmidt and Riess, as well as members of the Supernova Cosmology Project and the High-z Supernova Search Team.

Perlmutter is a member of the National Academy of Sciences, the American Academy of Arts and Sciences, and the American Philosophical Society.

Legacy

The discovery of the accelerating expansion of the universe, led in part by Perlmutter's Supernova Cosmology Project, is one of the landmark findings in the history of physical science. Before the results were announced in 1998, the prevailing expectation among cosmologists was that the gravitational attraction of matter in the universe would gradually slow the expansion that began with the Big Bang. The finding that the expansion is instead speeding up implied the existence of a previously unknown component of the universe — dark energy — which constitutes roughly 68 percent of the total energy density of the cosmos. This discovery reshaped the standard model of cosmology and opened an entirely new field of investigation that continues to be a central focus of modern astrophysics and fundamental physics.

The techniques developed by Perlmutter and the Supernova Cosmology Project for the systematic discovery and study of distant supernovae have become foundational methods in observational cosmology. The "batch discovery" approach pioneered by the SCP — in which large numbers of supernovae are found on a predictable schedule — enabled the statistical analyses that made the accelerating expansion result possible and has been adopted and refined by subsequent surveys.

Beyond his contributions to fundamental science, Perlmutter's work on Third Millennium Thinking represents an effort to extend the principles of scientific reasoning beyond the laboratory. By advocating for the application of evidence-based thinking, uncertainty quantification, and intellectual humility to everyday decision-making and public discourse, Perlmutter has sought to address what he and his co-authors see as a crisis of trust and epistemology in the modern world.

His appointment to PCAST in 2021 further placed him at the intersection of science and public policy, enabling him to bring the perspective of fundamental research to national discussions about the role of science and technology in governance.