Driver's vision enhancer and DRS Technologies. All objects above Absolute zero (−273.15 °C / −459.67 °F) emit infrared radiation (IR), an invisible form of light beyond the optical spectrum. The optical spectrum is part of the electromagnetic energy spectrum which consists of ultraviolet, visible, and near, middle, and far-infrared energy. Only a small part of the optical spectrum is visible to the unaided eye. The Sun emits energy across the entire electromagnetic spectrum. Solar energy strikes the surface of objects. Some of that energy is absorbed and stored as heat (thermal energy). After sunset, this thermal energy remains and is emitted in the
Ultraviolet (Light My Way) naked eye and ultimately unknowable to the human intellect." Conversely, Steve Stockman, author of "Walk On: The Spiritual Journey Of U2", sees "Ultraviolet" as being about Bono's wife Ali Hewson, and "how when he feels like trash, she makes him clean," but says there is good reason to interpret the song as being just as much about God. The song's title supports this view: indigo and violet rarely appear in song lyrics as frequently as other colours, while ultraviolet represents an unseen wavelength beyond the visible spectrum. As such, the title evokes the image of black light or an invisible