ABSTRACT
In 1800, the English astronomer William Hershel was working on a seemingly trivial astronomical question: Which color in the visible spectrum delivered heat from the sun? He used a glass prism to produce a spectrum, while a thermometer, its bulb wrapped in black paper, was used to measure the temperature change within each color. Slight increases were noted throughout the spectrum, but they were nothing when compared with that of “pure” sunlight, i.e., all the colors combined. Going out for a meal, he left the thermometer on the table just outside the spectrum, next to the red band.
