Infrared radiation was discovered by William Herschel in 1800. He used a prism to refract sunlight and held a thermometer just beyond the red end of the spectrum. This thermometer – meant to be a control to measure the room temperature – recorded the highest temperature of all pic.twitter.com/3dXxPW3nCy

— Fermat's Library (@fermatslibrary) December 24, 2018