A longtime resident of Bala Cynwyd who lived most recently in Jenkintown, Dr. Mann was born in New York and attended the University of Virginia for both his undergraduate and graduate studies. He spent two years working on a way to enrich uranium - an effort he later learned was part of the Manhattan Project, the U.S. effort to build the first atomic bomb.
A different uranium enrichment method was ultimately used to make the bombs that were dropped on Japan, yet Dr. Mann was nevertheless shaken when he learned of the purpose of the research, his son Brian said. The physicist heard about the first bomb from a newsboy hawking papers on the street, his son said.
"He said he stopped and grabbed the paper, and literally felt like he was going to pass out," Brian Mann said. "The effect of what that meant to the world really struck him."
Dr. Mann joined the faculty at Penn in 1949 after a stint at Columbia University. He was perhaps best known for his discoveries of fundamental properties of neutrinos, which are essential to the process of fusion.
"The stars could not burn without them," said Beier, who joined Dr. Mann on several of his findings.
Neutrinos are emitted in countless numbers by the sun and other stars. The South Dakota mine was seen as a good place to detect them because the earth acts as a filter. Most cosmic radiation is blocked from reaching that deep into the Earth, whereas neutrinos can slip right through.
During their careers, Dr. Mann and Beier helped make the first direct measurements of neutrinos emitted by the sun, and also measured the particles coming from a supernova, an experience Dr. Mann recounted in the 1987 book, Shadow of a Star.
Brian Mann said his father was not openly affectionate but rarely became angry. Rather than give his children the answer to a problem, he would urge them to seek it on their own, offering guidance by quoting Lincoln, Jefferson, and Franklin.
"That's just the kind of intellectual property that was being thrown about the house routinely," Brian Mann said. "It was not, 'Hey, how'd the Phils do today?' "
In addition to his son, Dr. Mann is also survived by his wife, Lucy; another son, Stephen; a daughter, Cecile; six grandchildren; and two great-grandchildren. Another son, David, died in 2009. Dr. Mann's first wife, Jayne Bowers Mann, died in 1999.
Services were held Wednesday, Jan. 16.
Contact Tom Avril at 215-854-2430 or firstname.lastname@example.org