mspohr writes: The Guardian has a news article about a recently published journal entry proposing a way to test the theory that the speed of light was infinite at the birth of the universe: "The newborn universe may have glowed with light beams moving much faster than they do today, according to a theory that overturns Einstein's century-old claim that the speed of light is a constant. Joao Magueijo, of Imperial College London, and Niayesh Afshordi, of the University of Waterloo in Canada, propose that light tore along at infinite speed at the birth of the universe when the temperature of the cosmos was a staggering ten thousand trillion trillion celsius. Magueijo and Afshordi came up with their theory to explain why the cosmos looks much the same over vast distances. To be so uniform, light rays must have reached every corner of the cosmos, otherwise some regions would be cooler and more dense than others. But even moving at 1bn km/h, light was not traveling fast enough to spread so far and even out the universe's temperature differences." Cosmologists including Stephen Hawking have proposed a theory called inflation to overcome this conundrum. Inflation theorizes that the temperature of the cosmos evened out before it exploded to an enormous size. The report adds: "Magueijo and Afshordi's theory does away with inflation and replaces it with a variable speed of light. According to their calculations, the heat of universe in its first moments was so intense that light and other particles moved at infinite speed. Under these conditions, light reached the most distant pockets of the universe and made it look as uniform as we see it today. Scientists could soon find out whether light really did outpace gravity in the early universe. The theory predicts a clear pattern in the density variations of the early universe, a feature measured by what is called the 'spectral index.' Writing in the journal Physical Review, the scientists predict a very precise spectral index of 0.96478, which is close to the latest, though somewhat rough, measurement of 0.968."