Hans Bethe, the nuclear physicist whose elegant calculations explained how stars shine and laid the foundation for development of both the atomic and hydrogen bombs, has died. He was 98.

Bethe, who received the Nobel Prize in Physics in 1967, died Sunday at his home in Ithaca, N.Y., Cornell University announced Monday.  (And did you know that famous Ithacans include: “Roots” author Alex Haley, astronomer Carl Sagan, television writer Rod Serling, and former World Bank president Paul Wolfowitz.)

A reluctant but crucial participant in the World War II effort to develop nuclear weapons, Bethe later became one of the country’s most passionate and persuasive proponents of disarmament. He argued that the use of such weapons would cost not only countless lives, but “liberties and human values as well.”

A brilliant, prolific and engaging theorist with an encyclopedic knowledge of nuclear physics, Bethe spent more than 60 years working with only a slide rule, a stack of blank paper and his enormous intellect, turning out page after page of mistake-free, complex calculations that fundamentally altered how scientists viewed the microscopic world of the atom.

“He was the last of the old masters,” said astrophysicist Edward Kolb of the Fermi National Accelerator Laboratory. “He turned out classic paper after classic paper.”