William Herschel (1738-1822) German-born English astronomer. Artist: Unknown
1-152-405 - Ann Ronan Picture Library/Heritage-Images
William Herschel (1738-1822) German-born English astronomer. Herschel investigating the heating effect of infra-red light. He passed sunlight through a prism, positioning thermometers just beyond the visible red part of the spectrum. Herschel recorded that there was a temperature increase, leading him to conclude that there must be an invisible form of energy (the infra-red). He published his discovery in 1800. Herschel also discovered Uranus in 1781, the first new planet to be discovered since ancient times. In the background is Herschel's 40ft reflecting telescope, which he built himself.