Ultraviolet not necessarily coincide; for example one applied physics publication used a boundary of 190 nm between hard and soft UV regions. Very hot objects emit UV radiation (see black-body radiation). The Sun emits ultraviolet radiation at all wavelengths, including the extreme ultraviolet where it crosses into X-rays at 10 nm. Extremely hot stars emit proportionally more UV radiation than the Sun. Sunlight in space at the top of Earth's atmosphere (see solar constant) is composed of about 50% infrared light, 40% visible light, and 10% ultraviolet light, for a total intensity of about 1400 W/m in vacuum. However, at ground
Ultraviolet (Light My Way) dealt with themes of anxiety and despair. Bono has described "Ultraviolet" as "an epic U2 song [but] the key of it left my voice in a conversational place and allowed a different kind of lyric writing." Producer Eno wrote that a combination of opposites within each song was a signature characteristic of "Achtung Baby" and that as part of that, "Ultraviolet" had a "helicopterish melancholy". In "Achtung Baby"s album package, "Ultraviolet" is presented next to a photograph of a crumbling Berlin building that has a Trabant parked in front of it. "Rolling Stone" noted that "Ultraviolet" was one of the