Giant space-time ripples may cause cosmic expansion* 17:43 18 March 2005 * NewScientist.com news service * Maggie McKee Dark energy is not necessary to explain the accelerating expansion of the universe observed by astronomers, suggest controversial new calculations. Instead, gigantic ripples in space-time - larger than the observable universe - may be the cause. Astronomers have known since the 1920s that space itself has been expanding since the big bang about 14 billion years ago. But in 1998, they discovered the expansion must have sped up about a billion years ago, based on observations of supernovae that appeared farther away...