Max Karl Ernst Ludwig Planck was a German physicist who provided the watershed between classical and modern physics. Around 1900 Planck came up with a mathematical solution to explain the nature of black-body radiation. He showed that energy is emitted and absorbed in discreet packets of what he called "quanta," and that these had a definite size -- an absolute constant now called Planck's constant (symbol h
). Planck's finding didn't get much attention until the idea was furthered by Albert Einstein
in 1905 and Niels Bohr
in 1913. Planck won the Nobel Prize in 1918, and, together with Einstein's theory of relativity, his quantum theory changed the field of physics. He spent most of his career at the University of Berlin. After his retirement in 1926 he was the president of the Kaiser Wilhelm Society for the Promotion of Science until 1937, when he clashed with Adolf Hitler
's Nazi party. Planck stayed in Germany during World War II, but Allied bombing destroyed his house toward the end of the war. He was rescued by American forces while trying to flee Germany and spent his last years in Göttingen.