Relativistic Doppler effect invisible ultraviolet wavelengths, infrared light is blueshifted into the visible range. Precisely what changes in the colors one sees depends on the physiology of the human eye and on the spectral characteristics of the light sources being observed. The Doppler effect (with arbitrary direction) also modifies the perceived source intensity: this can be expressed concisely by the fact that source strength divided by the cube of the frequency is a Lorentz invariant This implies that the total radiant intensity (summing over all frequencies) is multiplied by the fourth power of the Doppler factor for frequency. As a consequence, since Planck's
Ultraviolet (Light My Way) singing the repeated "baby"s, one of the most heavily used clichés in pop songs and one that he had avoided up to that point in his songwriting; Flood later commented that "he got away with it alright." Although the song is ostensibly about love and dependency, like many U2 songs, it also lends itself to religious interpretations. Listeners have heard an allusion to the Book of Job and its tale of God serving as a lamp upon Job's head walking through the darkness. Robyn Brothers suggests that ultraviolet light is "a metaphor for a divine force both unseen to the