Lenard showed an interest in science at a young age. The son of a very wealthy winemaker, he was educated by some of the most eminent scientists of the time, including Robert Bunsen and Hermann von Helmholtz. After graduating from the University of Heidelberg he worked at several universities before serving as assistant to Heinrich Hertz in 1892, taking over Hertz's laboratory after his death in 1894. He returned to Heidelberg as a professor in 1907 and remained there until 1937, when he left academia to serve as an advisor to Adolf Hitler. Lenard became interested in cathode ray as a teenager after reading a paper by William Crookes. At that time it was impossible to study the rays themselves--they could be easily observed within a Crookes tube, but they were too weak to penetrate the tube's glass. During his studies with Hertz, Lenard designed a modified Crookes tube that included a...