Infrared a wave and like its quantum particle, the photon. Infrared radiation was discovered in 1800 by astronomer Sir William Herschel, who discovered a type of invisible radiation in the spectrum lower in energy than red light, by means of its effect on a thermometer. Slightly more than half of the total energy from the Sun was eventually found to arrive on Earth in the form of infrared. The balance between absorbed and emitted infrared radiation has a critical effect on Earth's climate. Infrared radiation is emitted or absorbed by molecules when they change their rotational-vibrational movements. It excites vibrational modes
Ultraviolet (Light My Way) it. "Ultraviolet" played a featured role during the encores of the group's 1992–1993 Zoo TV Tour, 2009–2011 U2 360° Tour, and the Joshua Tree Tour 2017. "Ultraviolet (Light My Way)" began as two different demos, one variously called "Ultraviolet" and "69" (which eventually evolved into the B-side "Lady with the Spinning Head") and an alternately arranged demo called "Light My Way". Over the course of the recording sessions, U2 added various overdubs to the song, but producer Brian Eno believed these additions negatively impacted the track. Eno aided the group in editing down the song, and he explained his assistance