Kirchhoff, Gustav Robert (1824-1887), a German physicist. Investigations in spectrum analysis enabled Kirchhoff and Robert Wilhelm Bunsen to discover the elements cesium (1860) and rubidium (1861). Kirchhoff formulated laws concerning heat radiation and electrical circuits. He was born in the East Prussian city of Königsberg (now Kaliningrad, Russia) and studied at the university there. Kirchhoff taught physics at the universities of Breslau, Heidelberg, and Berlin.
The man immortalized on the left was behind the three laws of motion and the universal law of gravitation. He was also competitive, temperamental and fascinated with alchemy. How well do you know Newton?
He is famous for a phrase he never said, for wearing turtlenecks and for hosting the original 'Cosmos' TV series. As enthusiastic about the stars as he was about marijuana, Carl Sagan led a very surprising life. Here are 10 cool facts.