ABSTRACT
Sir Frederick William Herschel, the 18th-century English astronomer, was not one to let his curiosity go unsatisfied. His first love had been music, but after a few years of playing oboe in a German military band, he had grown restless. He set a prism in a window exposed to direct sunlight, then projected the spectrum of colored light streaming out of the prism onto the top of a table. On the table he placed two thermometers-one resting in the colored light, and the other, an experimental control, outside the projected light beam. Twentieth-century science has put the infrared spectrum to work in a number of ways. Soldiers find targets in the dark with sensors that “see” in the infrared, as they demonstrated dramatically in the Gulf War. The most vivid image for understanding the nature of electromagnetic waves was devised by the 19-century English physicist and chemist Michael Faraday.
