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Paul J.
Steinhardt (BS '74)

Albert Einstein Professor in Science and Director of the Princeton Center for Theoretical Science, Princeton University

For seminal contributions to theoretical physics and cosmology. Among his many achievements, Steinhardt developed new inflationary models of the universe, advanced the theory of quasicrystals, and discovered the only known naturally occurring quasicrystals.

 

Article

Caltech Degree
BS ’74, Physics

Current Title
Albert Einstein Professor in Science and Director of the Princeton Center for Theoretical Science, Princeton University

Sample of Achievements and Awards

  • Proposed the first successful working model of cosmic inflation in 1982
  • Advanced the theory of quasicrystals in 1984
  • Led the discovery of the first—and to date only—naturally occurring quasicrystal
  • Recipient of the Oliver E. Buckley Prize of the American Physical Society in 2010 for his contribution to the theory of quasicrystals
  • Simons Fellow in Theoretical Physics at Princeton; Radcliffe Institute Fellow at Harvard; and Moore Fellow at Caltech
  • Author of over 200 refereed articles, six patents, two patents pending, three technical books
  • Co-authored Endless Universe: The Big Bang and Beyond, 2007
 

Model of a quasicrystal.

The rock fragment was just a speck, sent over from a museum collection in Italy, and was the only known sample on the planet to have a naturally occurring quasicrystal formation within it.

Paul Steinhardt had to know where it originally came from.

A distinguished theorist at Princeton, Steinhardt is perhaps best known for two of his main interests: cosmology and quasicrystals.

His cosmological contributions have shaped our understanding of the early formation of the universe. In 1982, together with his graduate student Andreas Albrecht, Steinhardt proposed the first successful working model of cosmic inflation: the theory that soon after the Big Bang, the universe underwent a short burst of exponential expansion. While that work helped to make inflation the dominant study of early cosmology, Steinhardt was unsatisfied with the model’s flaws. So 20 years later, he and physicist Neil Turok, director of the Perimeter Institute for Theoretical Physics, developed radical alternatives, the ekpyrotic and cyclic models, which proposed that the evolution of the universe is an endlessly repeating cycle and that certain key conditions occurred long before the Big Bang. [related news: First Direct Evidence of Inflation and Primordial Gravitational Waves]

While the perfect model has yet to be found, Steinhardt is hopeful. “The data on both a macro and micro scale points to a universe that is very simple,” Steinhardt says. “I think that’s an enormous hint. If there's any chance of trying to explain the universe in its entirety, what gives me hope is that simplicity.”

Then there’s Steinhardt’s other interest: quasicrystals—a term he coined 30 years ago.

The name refers to a new phase of solid matter with symmetries previously thought to be impossible. The laws governing crystal formations state that they can possess symmetries in only two, three, four, and six folds, and this determines many of their physical properties and applications. Quasiperiodic crystals (or quasicrystals for short) broke those laws entirely.

In the early 1980s, while at the University of Pennsylvania, Steinhardt and his then-graduate student Dov Levine developed the first working theory for how these “impossible crystals” could exist.

At the same time, independent researcher Dan Shechtman spotted quasicrystal formations in an aluminum alloy in his lab and in 1984 published his findings (for which he won the Nobel Prize in Chemistry in 2011). “Shechtman had a material without a theory, and we had a theory without a material.” Steinhardt says. “The discovery that these structures could exist opened the door to a whole new spectrum of solid materials.”

New experimental technologies, new discoveries, new ways of teaching and sharing information—these are all the earmarks of exciting times.

Since then, numerous examples have been found, but all had been discovered in the lab. This left the question—did these quasicrystals occur in nature? In 1999, Steinhardt began reaching out to colleagues around the world and asked them to keep an eye out for possible candidates. He met with little success. Eight years later and half a world away at the University of Florence, mineralogist Luca Bindi found a fragment in his museum collection. 

“Luca sent us a promising sample that, when we tested it, gave a beautiful diffraction pattern, as perfect as any laboratory-made specimen I had seen,” Steinhardt says. “If it was natural, this was an important fragment.”

The search for the rock’s origins played like an international detective story, involving a deceased rock collector in Amsterdam, a shady Soviet-era geologist retired in Israel, and a Romanian mineral smuggler. The trail led to the Koryak Mountains, northeast of the Kamchatka peninsula in Russia. There, Steinhardt and his team—with the help of his son William Steinhardt (BS ’11), who majored in geophysics—discovered more samples containing the quasicrystal formation. Steinhardt and his collaborators theorize the shards came from a meteorite impact long ago.

The search team in Koryak Mountains. Photo by William Steinhardt (BS ’11)

“Paul is a scientist of remarkable accomplishment,” says Tom Lubensky (BS ’64), the Christopher H. Browne Distinguished Professor of Physics at the University of Pennsylvania. “He has played a leading role in our theoretical understanding of the universe.”

“I’m very optimistic about the future of science generally but in particular the science that I work in,” Steinhardt says. “New experimental technologies, new discoveries, new ways of teaching and sharing information—these are all the earmarks of exciting times.”

 
Next: Richard K. Miller (PhD '76)

Next:
Richard K. Miller
(PhD '76)