In 1913, Danish scientist Neils Bohr (1885-1962) developed a quantum theoretical model of the hydrogen atom in which the electrons orbit the nucleus. His model predicted the frequencies of spectral lines that other physicists had only observed, and he received the 1922 Nobel Prize for Physics for his work. Bohr also helped develop the atomic bomb. In this photo, he discusses an equation at Princeton University, N.J., on March 21, 1950.
Can you spot your holiday? The incredible images that reveal exactly where we fly EVERY day