Theory Tests Constancy of the Speed of Light

A team of Australian scientists has proposed that the speed of light may not be a constant, a revolutionary idea that could unseat one of the most cherished laws of modern physics: Einstein’s theory of relativity.

The team, led by theoretical physicist Paul Davies of Sydney’s Macquarie University, says it is possible that the speed of light has slowed over billions of years. Davies and astrophysicists Tamara Davis and Charles Lineweaver from the University of New South Wales published the proposal in the Aug. 8 issue of the journal Nature.

The suggestion that the speed of light can change is based on research collected by New South Wales astronomer John Webb, who posed a conundrum when he found that light from a distant quasar had absorbed the wrong type of photons from interstellar clouds on its 12-billion-year journey to Earth.

Davies said that, fundamentally, Webb’s observations mean that the structure of atoms emitting quasar light was slightly but ever so significantly different from the structure of atoms in humans. The discrepancy could only be explained if either the electron charge or the speed of light had changed.