Leon Heller, an eminent theoretical physicist, passed away on April 12, 2023, at the age of 93. He was born on December 16, 1929, in Brooklyn, New York, to E. Lawrence Heller and Henrietta Geller. Leon lost his mother when he was only 12. He and his father then lived with his aunt’s family for three years. Leon remembered this period as among the happiest times of his youth. Subsequently, Leon’s mother’s extended family had a significant role in his upbringing, and he enjoyed frequent visits with his cousins.
Leon attended Brooklyn College, a prized school with a reputation for high academic standards. He got a sterling education as well as meeting his future wife, Rosalie Liebschutz. Since Leon and Rosalie shared a love for classical music (which was an anchor for the remainder of their lives) it was entirely fitting that they met in the Classical Music Lounge. Professor Melba Phillips, part of the physics faculty, was influential in Leon’s life both as a physics instructor and adviser. Under her tutelage Leon began to comprehend the discipline of theoretical physics.
He subsequently pursued his Ph.D. in nuclear physics at Cornell University under Professor Phillip Morrison’s guidance. Leon’s thesis led him to understand the cosmic abundance of deuterium, which was later confirmed as a part of the Big Bang theory.
In 1956, Leon, his then wife Rosalie, and their one year old son moved to Los Alamos New Mexico where he joined the world renowned scientific laboratory as a physicist. Leon started his research on the force holding together the atomic nucleus. He became a prominent researcher in this field and his work led to numerous speaking invitations at conferences worldwide. In 1971, Leon became the Group Leader of the Theoretical Medium Energy Physics Group, newly formed to support the Los Alamos Meson Physics particle accelerator facility.
Leon was constantly curious and always looking to expand his knowledge. After 30 years of physics research he dramatically changed professional gears. In the mid-1980’s Leon became acquainted with Ed Flynn, who had been a nuclear physicist, but who’s research interest transitioned to the workings of the human brain. By using magnetoencephalography, Ed’s team could noninvasively detect magnetic fields produced by the brain’s electric currents. Ed’s team needed theoretical support which led Leon to a completely new career. Then, around 2010, after having worked over 55 years at the laboratory, Leon switched gears yet again. Since he’d always been interested in the gravitational force and became fascinated by Black Holes. Although Black Holes were increasingly well understood many aspects remained murky. Leon began researching the event horizon, the black hole’s outermost edge. Leon published papers regarding his research even into his early 90’s.
His outward appearance was always mild-mannered and soft-spoken, but he was a fierce defender of scientific integrity. Two of his favorite stories illustrate this. In 1986 Freeman Dyson gave a lecture at the University of Adelaide in Australia where Leon was working. Freeman said “there is a great deal we don’t understand about quantum mechanics.” Leon replied “that isn’t what you told us while teaching quantum mechanics at Cornell in 1954…rather you said it was settled science.” Dyson replied “I’m older and wiser now.”
Another favorite story was that Leon discovered a factor of two computational error in one of Richard Feynman’s more important papers. Leon spent years trying to get Feynman to acknowledge his error, until finally at a physics conference they were alone in an elevator and Feynman said he recognized and was aware of the mistake. Feynman never publicly acknowledged the error, but Leon was relieved that Feynman at least recognized it privately.
Leon was an excellent mentor to many postdoctoral researchers. To recognize their contributions he created the Postdoctoral Publication Prize in Theoretical Physics. In 1974, he proposed a weekly colloquium on theoretical physics, which became a popular event.
In 1997 Leon became a member of the J. Robert Oppenheimer Memorial Committee. The Committee’s primary mission is to preserve Oppenheimer’s legacy as a distinguished scientist, teacher, administrator, and humanitarian. A key objective was to redress the wrongful removal of Oppenheimer’s security clearance. This was finally accomplished after more than a decade involving multiple campaigns within the federal government. The Committee also provides scholarships to promising graduating high school seniors and sponsors an eagerly attended annual public lecture. Leon also created an annual scholarship in memory of Rosalie for gifted music students.
Leon derived great pleasure over the years from Rosalie’s musical performances, most often with her fellow chamber musicians. He also enjoyed observing the progress of her many music students, both adults and youngsters. Watching their three children Peter, Anthony, and Jean mature into fine, loving adults was a source of great happiness. He also had many dear friends and neighbors who he loved and who were great friends and supporters throughout his 67 years living in Los Alamos.
Hiking and skiing in the magnificent environment of Northern New Mexico and the opportunity to work at a very special laboratory provided an enduring reminder how fortunate Leon was to have chosen Los Alamos for his home and work. In 1991 he joined a Wednesday hiking group, the members of which became close friends. The hiking group also took annual trips to more distant locales such as the Grand Canyon. Leon reveled in these experiences and frequently Rosalie or his children would accompany him. Leon was also thrilled to combine his love of the outdoors and his mentorship skills by working as a volunteer docent at Bandelier National Monument. His knowledge of Bandelier was unrivaled and he thoroughly enjoyed imparting park information to visitors from many countries and walks of life.
Leon also had a lighter side. He enjoyed telling jokes and relished a good turn of phrase to delight his audience. He also enjoyed making wagers on a broad range of subjects including politics and science. The amount bet was always a nickel. When his good friend and collaborator Bill Beyer mentioned that Oxford University maintained a book in which wagers were recorded, Leon’s reaction was dismay, realizing that his prior bets had been lost to posterity. He immediately acquired a notebook in which all future bets were recorded.
Leon was a devoted husband, father, grandfather and great grandfather. Leon lost his beloved wife Rosalie in 2016. He is survived by his three children (Pete, Anthony and Jean), seven grandchildren (Nicole, Greg, Dmitri, Alexander, David, Mia and Maxwell) and twin great granddaughters (Sophie and Ella). His contributions to theoretical physics and his impact on colleagues, friends and relatives will be dearly remembered.