Karl Schwarzschild

Karl Schwarzschild was born in Frankfurt am Main on October 9, 1873, the eldest of six children in a prosperous Jewish family. He was a prodigy: he published two papers on celestial mechanics — on the orbits of double stars — at sixteen, before finishing secondary school. He studied at Strasbourg and Munich, earning his doctorate in 1896, and rose quickly through German astronomy, holding posts at Vienna and Göttingen before becoming director of the Potsdam Astrophysical Observatory in 1909, then the most prestigious astronomical position in Germany.

Schwarzschild's research ranged across nearly the whole of early-twentieth-century astrophysics. He pioneered the use of photography for precise photometry, established the photographic magnitude scale, and worked out the theory of radiative equilibrium in stellar atmospheres — laying foundations for the understanding of how energy flows out of stars. He made early contributions to geometrical optics, spectroscopy, and the quantum theory of the Stark effect. He was, by 1914, one of the most versatile and respected scientists in the German-speaking world.

When the First World War began, Schwarzschild — already over forty and exempt — volunteered for military service. He was commissioned and posted to a unit computing artillery trajectories, eventually on the Eastern Front in Russia. There, in the winter of 1915, he read Einstein's just-published field equations and, within weeks, derived the first exact solution: the spacetime geometry outside a static, spherically symmetric mass. He communicated it to Einstein in a letter dated December 22, 1915. A second paper, giving the interior solution for a uniform-density fluid sphere, followed in February 1916.

He did not live to see the significance of his work. In the trenches he contracted pemphigus, a rare and then-incurable autoimmune blistering disease, possibly aggravated by the conditions of the front. Invalided home, he died in Potsdam on May 11, 1916, at the age of forty-two. Einstein delivered his eulogy before the Prussian Academy. The radius that bears his name, the metric that bears his name, and ultimately the theory of black holes all trace back to three weeks of work done under artillery fire.