Earl Robert Callen, 77, a retired American University physics professor, founder and former chairman of the Montgomery County chapter of the American Civil Liberties Union and an amateur musician and dancer, died of cancer Dec. 9 at his home in Chevy Chase.

As a research physicist, Dr. Callen specialized in such matters as solid state and magnetism. But he also tried to relate science to social issues and popular culture, and he bolstered AU science enrollments with such courses as "Science, Human Values and Public Policy." He did statistical studies on such diverse subjects as menstrual period rhythms and the frequency of appointments to the Supreme Court.

When he was in his sixties, he began studying the piano, trombone and saxophone, and he played in the middle school band at Sidwell Friends School. In the late 1980s, he danced with a Japanese folk dance troupe, the Blue Bells. In 1993, as part of an otherwise all-female dance group, he danced in the lobby of the Kennedy Center.

He was an antiwar activist and a leader in a 1982 project known as Ground Zero, a nationwide program to educate Americans on the likely effects of a nuclear war. Leading media representatives through a hypothetical scenario that would accompany the detonation of a one-megaton bomb -- small by nuclear standards -- at the White House, Dr. Callen said the blast would produce a 200-foot-deep crater with a quarter-mile diameter. The White House, all of Lafayette Square, the Treasury Building, the Old Executive Office Building and all their occupants would be vaporized. Most of downtown Washington would be cooked to a crisp by a fireball 10,000 times hotter than the sun, he said.

Dr. Callen was born in Philadelphia. During World War II, he was an Army medical corpsman serving in the Philippines. After the war, he graduated from the University of Pennsylvania and received a doctorate in physics at the Massachusetts Institute of Technology.

He moved to this area in 1954. For eight years, he worked at the National Security Agency and the Naval Ordnance Laboratory's applied research department. He then joined the American University faculty.

From his home in Chevy Chase, Dr. Callen commuted on occasion by motorcycle to his AU office, where posters of the Beatles were taped on the walls. He was known socially in the physics department as the brewer of a powerful grain alcohol punch served at parties featuring music by the departmental band, the Strange Particles.

As the chairman of the Montgomery County ACLU in this period, Dr. Callen used his statistical studies to challenge the fairness of Montgomery County's selective service lottery, producing studies that appeared to show that men born in the second half of the year were being drafted with a greater frequency than men born in the first half. He said that when capsules for each day of the year were dumped in a giant glass bowl for drawing, the January capsules were always at the bottom and the December ones on top -- and much more likely to be picked. "They didn't mix up the bowl, at least not carefully enough," Dr. Callen said.

His statistical studies also produced evidence showing that women who give birth to boys subsequently have shorter menstrual periods than women who give birth to girls. He refused to draw conclusions from this, other than to speculate that the presence of a male child in a woman's body could affect the balance of female hormones.

In 1965, Dr. Callen took his family to Japan, where for a year he was a visiting professor at Osaka University. On his return to AU, he took up sailing and table tennis with other faculty members. He retired in 1984, then in the late 1980s returned to Japan, where he was a Navy scientist for three years.

He was a regular at the Saturday night dances at Glen Echo Park and an enthusiastic camper, tennis player and nature lover. He was said by relatives and friends to have been unabashedly optimistic, which he described as a "genetic disorder" that he had inherited from his mother.

Survivors include his wife of 54 years, Anita Blatt Callen of Chevy Chase; four daughters, Liza Callen of Crofton, Melany Guzikowski of Potomac, Jane Abigale Callen of Bethesda and Jody Madelon Callen-Dickerson of Mount Rainier; eight grandchildren; and a great-grandson.