Physicist George Smoot, known for his work that confirmed the Big Bang theory, died on September 18 in Paris at age 80 from a heart attack. Smoot was a professor emeritus of physics at the University of California, Berkeley, and held positions at Lawrence Berkeley National Laboratory and Université Paris-Cité.

Smoot, along with John Mather, led NASA’s Cosmic Background Explorer (COBE) mission, which in 1992 detected minute temperature fluctuations in the cosmic microwave background (CMB). This discovery provided strong evidence for the Big Bang theory and earned both scientists the Nobel Prize in Physics in 2006. At a press conference announcing the findings, Smoot said, “If you’re religious, it’s like seeing God.”

The APC laboratory in Paris noted in an obituary: “Today cosmology is at the center stage of physics, due in no small part to this [Smoot’s] and subsequent measurements of the CMB. This discovery prompted many researchers to switch to cosmology. A host of experiments, from the ground, from stratospheric balloons and from space have now followed the pioneering COBE measurements.”

Smoot’s instruments aboard COBE detected variations as small as one part in 100,000 within the CMB’s 2.7 degree Kelvin glow. These tiny differences represented early universe fluctuations that eventually developed into galaxies and galaxy clusters. The late Stephen Hawking described this detection as “the greatest scientific discovery of the century.” Reflecting on his work at the time, Smoot stated: “Those measurements really confirmed our picture of the Big Bang. By studying the fluctuations in the microwave background, we found a tool that allowed us to explore the early universe, to see how it evolved and what it’s made of.”

Smoot joined Berkeley Lab in 1971 and became a UC Berkeley faculty member in 1994. The Nobel committee recognized him and Mather for their work on “the discovery of the blackbody form and anisotropy of the cosmic microwave background radiation.” In 2007, he contributed $500,000 from his Nobel winnings to endow UC Berkeley's Center for Cosmological Physics.

Beyond research and teaching, Smoot engaged with public science communication—appearing on television shows such as "The Big Bang Theory" and winning $1 million on "Are You Smarter Than a Fifth Grader?" He also traveled extensively as a speaker.

Saul Perlmutter, fellow UC Berkeley physicist and Nobel laureate for discovering dark energy, recalled: “He was somebody who always enjoyed looking ahead to what was happening in the world and what was coming next… Almost always, I had that feeling that he was right.”

According to APC’s obituary: “He revolutionized our understanding of the cosmos and placed cosmology on a firm experimental footing.”

Born February 20, 1945 in Yukon, Florida, Smoot grew up partly in Alaska before attending MIT for undergraduate studies and earning his PhD there in experimental elementary particle physics. He moved to Berkeley Lab after graduation where he initially worked under Luis Alvarez before focusing on CMB research.

In collaboration with Richard Muller at UC Berkeley during the early 1970s, Smoot developed detectors flown by balloon to measure CMB temperatures above much of Earth’s atmosphere. His team later built instruments used aboard U-2 spy planes that measured galactic motion through space.

Smoot submitted a proposal to NASA for satellite-based measurement of CMB fluctuations; this effort merged with others under Mather’s leadership at Goddard Space Flight Center leading to COBE's launch after fifteen years' development.

Following COBE's success detecting CMB anisotropies in 1992—which marked an important milestone for precision cosmology—Smoot continued working on projects such as ESA's Planck satellite aimed at refining measurements further.

He helped establish research centers internationally—including institutes in South Korea, Spain and France—and played key roles founding educational programs like “Teaching the Universe” for secondary teachers as well as developing MOOCs such as “Gravity!” with Pierre Binétruy.

With journalist Keay Davidson he co-authored "Wrinkles in Time," documenting COBE's story for general audiences.

Among numerous honors throughout his career were Switzerland’s Einstein Medal (2003), Department of Energy’s Lawrence Award (1995), NASA Medal for Exceptional Scientific Achievement (1991), membership in the National Academy of Sciences and several others.

Survivors include his sister Sharon Smoot Bowie; two nieces; and partner Nóra Csiszár.