I examine the role of human and physical capital for the creation of scientific knowledge. I address the endogeneity of human and physical capital with two exogenous shocks: the dismissal of scientists in Nazi Germany and World War II bombings. A 10% shock to human capital reduced output by 0.2 SD in the short run, and the reduction persisted in the long run. A 10% shock to physical capital reduced output by 0.05 SD in the short run, and the reduction did not persist. The dismissal of star scientists caused much larger reductions in output because they are key for attracting other successful scientists.