Variable speed of light contribute to the above refractive index, Dicke considered a cosmology where "c" decreased in time, providing an alternative explanation to the cosmological redshift (p. 374). Dicke's theory is compatible with the SI definition of c since the time and length units second and meter can vary in concert, keeping the value of c fixed (p. 366). Spatial variation of the speed of light is implicitly present in general relativity, occurring in the coordinate space description.: "note that the photon speed is ... formula_9." (formula_10 denoting the gravitational potential −"GM"/"r") Based on this observation, variable speed of light models, including Dicke's,
Speed of Darkness fiction, named The Science of Discworld, written by Terry Pratchett, Ian Stewart and Jack Cohen. In a 2011 interview on BBC Radio 1, frontman Dave King explained that the title track and album title was taken from a quote of Dino Misetić, the artist who designed the album cover, which appeared in the book Sarajevo Marlboro. Dino, who grew up in the Balkans during the Balkan Wars, is quoted in the book, saying: "They taught us what the speed of light is, but nobody can teach you what the speed of darkness is." Flogging Molly: Additional musicians: Speed of Darkness