1898 – 1964
Leo Szilard (1898–1964) was a Hungarian-American physicist whose work bridged physics, thermodynamics, and the philosophy of information. He is best known for conceiving the nuclear chain reaction and co-patenting the nuclear reactor, but his 1929 analysis of Maxwell's Demon made a foundational contribution to the thermodynamics of information by demonstrating that measurement itself has an entropic cost. His career spanned theoretical physics, nuclear weapons development, and later, bioethics and arms control advocacy.
Resolved Maxwell's Demon paradox by showing that information acquisition (measurement) entails entropy increase, anticipating Landauer's principle
Conceived the nuclear fission chain reaction (1933) and co-patented the nuclear reactor with Enrico Fermi
Co-authored the Einstein–Szilard letter (1939) alerting Roosevelt to the possibility of nuclear weapons
Contributed to founding the Bulletin of the Atomic Scientists and the Pugwash Conferences on nuclear disarmament
Pioneered work connecting thermodynamics, information theory, and computation decades before Shannon's formal framework