Overview: George David Birkhoff (1884-1944), mathematician and Perkins Professor of Astronomy and Mathematics and Astronomy at Harvard College, taught mathematics at Harvard from 1912 until 1944. Birkhoff discovered what is now called the ergodic theorem in 1931, and his research focused on differential and difference equations and the calculus of variations, relativity, dynamical systems and stability. The Papers of George D. Birkhoff, 1902-1946, chiefly contain correspondence, writings, speeches,...