James Bardeen, who helped elucidate the properties and behavior of black holes, setting the stage for what has been called the golden age of black hole astrophysics, died on June 20 in Seattle. He was 83.

His son William said the cause was cancer. Dr. Bardeen, an emeritus professor of physics at the University of Washington, had been living in a retirement home in Seattle.

Dr. Bardeen was a scion of a renowned family of physicists. His father, John, twice won the Nobel Prize in Physics, for the invention of the transistor and the theory of superconductivity; his brother, William, is an expert on quantum theory at the Fermi National Accelerator Laboratory in Illinois.

Dr. Bardeen was an expert on unraveling the equations of Einsteins theory of general relativity. That theory ascribes what we call gravity to the bending of spacetime by matter and energy. Its most mysterious and disturbing consequence was the possibility of black holes, places so dense that they became bottomless one-way exit ramps out of the universe, swallowing even light and time.

Dr. Bardeen would find his lifes work investigating those mysteries, as well as related mysteries about the evolution of the universe.

Jim was part of the generation where the best and brightest went to work on general relativity, said Michael Turner, a cosmologist and emeritus professor at the University of Chicago, who described Dr. Bardeen as a gentle giant.

James Maxwell Bardeen was born in Minneapolis on May 9, 1939. His mother, Jane Maxwell Bardeen, was a zoologist and a high school teacher. Following his fathers work, the family moved to Washington, D.C.; to Summit, N.J.; and then to Champaign-Urbana, Ill., where he graduated from the University of Illinois Laboratory High School.

He attended Harvard and graduated with a physics degree in 1960, despite his fathers advice that biology was the wave of the future. Everybody knew who my father was, he said in an oral history interview recorded in 2020 by the Federal University of Par in Brazil, adding that he had not felt the need to compete with him. It was impossible, anyway, he said.

Working under the physicist Richard Feynman and the astrophysicist William A. Fowler (who would both become Nobel laureates), Dr. Bardeen obtained his Ph.D. from the California Institute of Technology in 1965. His thesis was about the structure of supermassive stars millions of times the mass of the sun; astronomers were beginning to suspect that they were the source of the prodigious energies of the quasars being discovered in the nuclei of distant galaxies.

After holding postdoctoral positions at Caltech and the University of California, Berkeley, he joined the astronomy department at the University of Washington in 1967. An avid hiker and mountain climber, he was drawn to the school by its easy access to the outdoors.

By then, what the Nobel laureate Kip Thorne, a professor at the California Institute of Technology, refers to as the golden age of black hole research was well underway, and Dr. Bardeen was swept up in international meetings. At one, in Paris in 1967, he met Nancy Thomas, a junior high school teacher in Connecticut who was trying to brush up on her French. They were married in 1968.

In addition to his son William, a senior vice president and the chief strategy officer of The New York Times Company, and his brother, William, Dr. Bardeens wife survives him, along with another son, David, and two grandchildren. A sister, Elizabeth Greytak, died in 2000.

Dr. Bardeen was a member of the National Academy of Sciences, as is his brother and as was his father.

Although he was speedy at math, Dr. Bardeen didnt write any faster than he spoke. William Press, a former student of Dr. Thornes now at the University of Texas, recalled being sent to Seattle to finish a paper that Dr. Bardeen and he were supposed to be writing. Nothing had been written. Dr. Bardeens wife then commanded the two to sit on opposite ends of a couch with a pad of paper. Dr. Bardeen would write a sentence and pass the pad to Dr. Press, who would either reject or approve it and then pass the pad back. Each sentence, Dr. Press said, took a few minutes. It took them three days, but the paper got written.

One of the epochal moments of those years was a monthlong summer school in Les Houches, France, in 1972 featuring all the leading black hole scholars. Dr. Bardeen was one of a half-dozen invited speakers. It was during that meeting that he, Stephen Hawking of Cambridge University and Brandon Carter, now of the Paris Observatory, wrote a landmark paper entitled The Four Laws of Black Hole Mechanics, which became a springboard for future work, including Dr. Hawkings surprise calculation that black holes could leak and eventually explode.

In another famous calculation the same year, Dr. Bardeen deduced the shape and size of a black holes shadow as seen against a field of distant stars a doughnut of light surrounding dark space.

That shape was made famous, Dr. Thorne said, by the Event Horizon Telescopes observations of black holes in the galaxy M87 and in the center of the Milky Way, and by visualizations in the movie Interstellar.

Another of Dr. Bardeens passions was cosmology. In a 1982 paper, he, Dr. Turner and Paul Steinhardt of Princeton described how submicroscopic fluctuations in the density of matter and energy in the early universe would grow and give rise to the pattern of galaxies we see in the sky today.

Jim was delighted that we used his formalism, Dr. Turner said, and was sure we got it right.

Dr. Bardeen moved to Yale in 1972. Four years later, unhappy with the academic bureaucracy in the East and yearning for the outdoors again, he moved back to the University of Washington. He retired in 2006.

But he never stopped working. Dr. Thorne recounted a recent telephone conversation in which they reminisced about the hiking and camping trips they used to take with their families. In the same conversation, Dr. Bardeen described recent ideas he had about what happens as a black hole evaporates, suggesting that it might change into a white hole.

That was one aspect of Jim in a nutshell, Dr. Thorne wrote in an email, thinking deeply about physics in creative new ways right up to the end of his life.

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James Bardeen, an Expert on Unraveling Einsteins Equations, Dies at 83 - The New York Times