The constancy, or otherwise, of the speed of light
  New varying speed of light (VSL) theories as alternatives to the inflationary model of the universe are discussed and evidence for a varying speed of light reviewed. Work linked with VSL but primarily concerned with deriving Planck's black body energy distribution for a gas-like aether using Maxwell statistics is considered also. Doubly Special Relativity, a modification of special relativity to account for observer dependent quantum effects at the Planck scale, is introduced and it is found that a varying speed of light above a threshold frequency is a necessity for this theory. 
Daniel J. Farrell and J. Dunning-Davies