Ernst Friedrich Ferdinand Zermelo made major contributions to mathematics in the area of set theory, especially by extending David Hilbert's work in solving the continuum hypothesis. The Zermelo-Fraenkel set theory is still in wide use.

Zermelo was born in Berlin, Germany on July 27, 1871. His father was a college professor, which helped set the academic tone of Zermelo's childhood. He attended a gymnasium (a classical college-preparatory school) in Berlin, graduating in 1889. Then, as was customary at the time, Zermelo took classes in mathematics, physics, and philosophy at a variety of universities--namely those at Berlin, Freiburg, and Halle.

Earning his doctorate in 1894 from the University of Berlin, Zermelo began working as an assistant to physicist Max Planck. Soon he began studying for a teaching certificate, which he obtained in 1899 at the University of Gôttingen with a dissertation on hydrodynamics. The school, which then was the world's leading center...