Planck Dies: Father of Quantum Theory Leaves Lasting Legacy

Max Planck did not want to overturn physics. He wanted to solve a narrow technical problem: why hot objects glow the colors they do. His answer, that energy comes in discrete packets rather than continuous waves, was so radical he spent years trying to walk it back. He could not. Born in Kiel, Germany, in 1858, he studied physics at the University of Munich despite being told by a professor that the field was essentially complete and there was nothing left to discover. He took the advice as a challenge. The problem that consumed him in the late 1890s was black-body radiation: classical physics predicted that a heated object should emit infinite energy at high frequencies, a result so absurd it was called the "ultraviolet catastrophe." Planck resolved it in December 1900 by proposing that energy was emitted and absorbed in discrete quantities he called "quanta." The constant that related energy to frequency, now called Planck's constant, became one of the fundamental numbers of physics. He did not fully appreciate what he had done. He viewed the quantization as a mathematical trick rather than a physical reality, and he spent years trying to reconcile it with classical physics. It was Einstein who recognized in 1905 that quantization was real, using it to explain the photoelectric effect. Planck won the Nobel Prize in Physics in 1918 and became the elder statesman of German science, leading the Kaiser Wilhelm Society through the political upheavals of the Weimar Republic and the Nazi era. His son Erwin was executed by the Gestapo in 1945 for his role in the plot to assassinate Hitler. Planck died on October 4, 1947, at eighty-nine, having lived long enough to see his reluctant revolution produce both the atomic bomb and the foundations of modern technology.