Speed of light the fundamental excitations (or quanta) of the electromagnetic field, called photons. In QED, photons are massless particles and thus, according to special relativity, they travel at the speed of light in vacuum. Extensions of QED in which the photon has a mass have been considered. In such a theory, its speed would depend on its frequency, and the invariant speed "c" of special relativity would then be the upper limit of the speed of light in vacuum. No variation of the speed of light with frequency has been observed in rigorous testing, putting stringent limits on the mass of the
Speed of Light (Speed song) Speed of Light (Speed song) "Speed Of Light" is the second single by South Korea boy group Speed. The single album by promotional singles "슬플약속 (That's My Fault)". In December 9, 2012, Core Contents Media released the first teaser photo for "It's Over" for their debut album Superior Speed. Before the release of the debut album, Speed's they released single album "Speed of Light" the title is 슬플약속 (That's My Fault) feat. Davichi's Kang Minkyung. Two music videos were released for the song "슬플약속 (That's My Fault)" featuring Davichi's Kang Minkyung; a dance version and a drama version featuring Park