Speed of light special theory of relativity, in which the speed of light in vacuum "c" featured as a fundamental constant, also appearing in contexts unrelated to light. This made the concept of the stationary aether (to which Lorentz and Poincaré still adhered) useless and revolutionized the concepts of space and time. In the second half of the 20th century much progress was made in increasing the accuracy of measurements of the speed of light, first by cavity resonance techniques and later by laser interferometer techniques. These were aided by new, more precise, definitions of the metre and second. In 1950, Louis Essen
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