Adam Riess

Adam Riess
Born	Adam Guy Riess 12/16/1969
Birthplace	Washington, D.C., U.S.
Nationality	American
Occupation	Astrophysicist, professor
Known for	Accelerating expansion of the universe, dark energy, Hubble constant
Education	Harvard University (PhD) Massachusetts Institute of Technology (BS)
Spouse(s)	Nancy Joy Schondorf (m. 1998)
Awards	Nobel Prize in Physics (2011) Shaw Prize in Astronomy (2006) MacArthur Fellowship (2008)

Adam Guy Riess (born December 16, 1969) is an American astrophysicist at Johns Hopkins University and the Space Telescope Science Institute. His work has centered on one obsession: light from distant supernovae could reveal the universe's fate. That pursuit led to something extraordinary. In 1998, he discovered the universe isn't just expanding. It's accelerating. For this, Riess shared the 2011 Nobel Prize in Physics with Saul Perlmutter and Brian Schmidt. He was only 41. The foundational research started when he was 27.

These days, Riess sits at the center of something equally puzzling: the "Hubble tension." Different measurement methods give different expansion rates, and that gap keeps growing. It raises fundamental questions. Does our standard cosmological model still work? His sustained work in observational cosmology has brought him multiple honors: the Shaw Prize in Astronomy (2006), a MacArthur Fellowship (2008), and election as a Fellow of the American Astronomical Society (2020).

Early Life

Riess was born on December 16, 1969, in Washington, D.C. He grew up in Warren, New Jersey, in the northern part of the state. Journalism ran in the family. His distant relative Curt Riess was a German-American author and journalist who wrote extensively on the Nazi era. Riess died in 1993 at 90.

Education and curiosity weren't optional in his household. His father was a naval engineer, his mother a clinical psychologist. At Watchung Hills Regional High School in Warren Township, science and mathematics were his natural habitats.

From childhood, Riess had a gift for physics. The universe's mechanics fascinated him. That fascination would pull him toward astrophysics, a field being transformed in the late twentieth century as new technologies opened up the deepest reaches of space with unprecedented clarity.

Education

MIT came first. He earned his Bachelor of Science in physics there, getting a serious grounding in both theory and experiment that set him up for observational cosmology work.

Then Harvard. He worked under Robert Kirshner and William H. Press, two giants in the field. His dissertation, finished in 1996, was titled "Type Ia Supernova Multicolor Light Curve Shapes." The focus: developing ways to use Type Ia supernovae as precise distance markers in cosmology. Out of this work came something crucial. The Multicolor Light Curve Shape (MLCS) technique. It let astronomers account for variations in how bright and colorful Type Ia supernovae are, cutting down the scatter in distance measurements dramatically. Suddenly, these supernovae became far more reliable "standard candles" for measuring cosmic distances.

Career

Discovery of the Accelerating Universe

After Harvard, postdoctoral work at UC Berkeley. That's where Riess joined the High-z Supernova Search Team under Brian Schmidt. The team's goal was straightforward: measure how fast the universe's expansion was slowing down using distant Type Ia supernovae. Everyone expected deceleration. Gravity should have been braking the expansion since the Big Bang.

Riess was 27 when he began leading the data analysis. In 1998, something shocking emerged from the numbers. The expansion wasn't slowing. It was speeding up. Those distant supernovae were dimmer than theory predicted, which meant they were farther away than models of a decelerating universe suggested. One conclusion followed inescapably: some unknown form of energy existed, pushing the cosmos apart faster and faster. They called it "dark energy."

That same finding came independently from Saul Perlmutter's team at Lawrence Berkeley National Laboratory, the Supernova Cosmology Project. Two independent teams. Same conclusion. The physics community reacted with shock. Science magazine named it the "Breakthrough of the Year" for 1998.

The implications were staggering. Dark energy makes up roughly 68 percent of everything in the universe. And we don't actually know what it is. The discovery reshaped cosmology entirely, replacing old models with the Lambda-CDM framework, where the cosmological constant represents that dark energy powering acceleration.

"Shocked even him," as he'd later describe it in talks and interviews.

Career at Johns Hopkins University and the Space Telescope Science Institute

Johns Hopkins came next. So did a position at the Space Telescope Science Institute (STScI) on campus, the operations center for both the Hubble Space Telescope and the James Webb Space Telescope.

In 2016, Johns Hopkins appointed Riess as a Bloomberg Distinguished Professor. Michael Bloomberg had committed $350 million to the university in 2013 to establish these positions, which are explicitly designed to break down silos between departments and schools. For Riess, it meant bridging the Krieger School of Arts and Sciences and the Whiting School of Engineering.

From Johns Hopkins and STScI, Riess has led an ambitious research program. Supernovae remain his main tools. He's pushed to pin down the Hubble constant with ever-greater precision. His team is called SH0ES (Supernova H0 for the Equation of State), and they work systematically to shrink the uncertainties in the cosmic distance ladder. That's the chain of methods astronomers use to measure how far away things really are.

One of his doctoral students, Daniel Scolnic, went on to become a major figure in supernova cosmology himself.

The Hubble Tension

Riess now stands at the heart of one of cosmology's biggest puzzles: the Hubble tension. Two different methods measure how fast the universe expands. They don't agree.

Riess's team observes Cepheid variables and Type Ia supernovae nearby. They get a Hubble constant of about 73 kilometers per second per megaparsec (km/s/Mpc). But measurements from the cosmic microwave background, the radiation left over from the early universe, observed by the European Space Agency's Planck satellite, give about 67.4 km/s/Mpc when run through the standard Lambda-CDM model.

That gap has gotten statistically worse, not better. By the mid-2020s, the tension had reached about 5 sigma, the kind of statistical significance particle physicists would call a discovery. Cosmologists now hotly debate: is this pointing to new physics beyond the standard model, or are there hidden systematic errors in one or both measurements?

Riess has been adamant. His local measurements are solid. The tension is real. He's stated his data has "prompted questions and further testing to determine if the Standard Model still adequately describes the universe." In a 2025 Atlantic interview, he explored what this might mean: perhaps unknown dark energy, a new particle, or physics we haven't even imagined yet.

The James Webb Space Telescope (JWST) started science operations in 2022. It's become crucial for testing these claims. Early JWST observations have largely confirmed Hubble's Cepheid measurements, strengthening the case that the tension isn't just measurement error in the local distance ladder.

But the story keeps evolving. Late 2025 brought new questions: might certain aspects of the accelerating expansion measurements themselves need re-examination? The debate grows more complex each month.

Public Engagement and Lectures

Riess doesn't hide his work in technical journals. He communicates it. In May 2025, he spoke at the University of Wisconsin–Madison. The lecture hall was packed. He "discussed how his research rewrote the fundamental story of the universe."

In April 2025, he delivered the Dirac Lecture at Florida State University, walking audiences through the latest on the expanding universe. September 2025 brought him to Pioneer Works in Brooklyn for a public discussion on the expansion of the universe as part of the "Scientific Controversies" series. December 2025 saw him sitting with PBS NOVA, discussing both dark energy and the Hubble tension in an extended interview.

Riess was also invited to deliver a public lecture at the PASCOS (Particles, Strings, and Cosmology) 2026 conference at the University of Sheffield in the United Kingdom.

Personal Life

In 1998, Riess married Nancy Joy Schondorf. The New York Times reported their wedding announcement. They live in Baltimore, where Johns Hopkins is based.

He's spoken about what it feels like to topple fundamental assumptions. In a 2013 NPR interview, he reflected on the process and impact of his discovery.

Recognition

The honors have accumulated steadily.

The Shaw Prize in Astronomy came in 2006, shared with Saul Perlmutter and Brian Schmidt for the accelerating expansion discovery. Awarded by the Shaw Prize Foundation in Hong Kong, it's sometimes called the "Nobel of the East" and comes with substantial money attached.

In 2008, the MacArthur Foundation gave Riess a MacArthur Fellowship, commonly called a "genius grant." These go to people showing exceptional creativity and promise for future achievement.

The Nobel Prize in Physics followed in 2011. He shared it with Perlmutter and Schmidt "for the discovery of the accelerating expansion of the Universe through observations of distant supernovae." Riess and Schmidt split one half for their High-z work; Perlmutter got the other half for leading the Supernova Cosmology Project. At 41, he was among the youngest Nobel physicists in recent memory.

There was also a Golden Plate Award from the Academy of Achievement.

In 2020, the American Astronomical Society named him a Fellow, recognizing his work in astronomy and astrophysics.

Legacy

Riess has changed how we understand the cosmos. That 1998 discovery wasn't just an update to existing knowledge. It was a reversal. The universe wasn't decelerating. Dark energy now sits at roughly 68 percent of all energy density in the universe. Its nature remains one of physics' deepest mysteries.

The finding shifted cosmological research entirely. The Lambda-CDM model became the standard framework. It sparked new investigations in theoretical physics, including fresh looks at Einstein's cosmological constant, which he'd abandoned but which might actually be real after all.

The Hubble tension could prove equally important. If it reflects genuine new physics rather than measurement problems, the standard cosmological model might need rebuilding. That would rank among the biggest developments in twenty-first century physics.

At Johns Hopkins and STScI, Riess mentors observational cosmologists and has helped build the field of precision cosmology, where increasingly exact measurements test and constrain our models. His ongoing work with Hubble and James Webb data continues pushing the boundaries of what we know about how the universe has expanded across all of time.