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,
Max Planck Institute for the Science of Light Max Planck Institute for the Science of Light The Max Planck Institute for the Science of Light (MPL) performs basic research in optical metrology, optical communication, new optical materials, plasmonics and nanophotonics and optical applications in biology and medicine. It is part of the Max Planck Society and was founded on January 1, 2009 in Erlangen near Nuremberg. The Institute is based on the Max Planck Research Group "Optics, Information and Photonics", which was founded in 2004 at the University of Erlangen-Nuremberg, as a precursor. The institute currently comprises five divisions. The institute currently is organized in five divisions, each