Davies said the only possible explanation for the unusual data was that the speed of light had been faster six to 10 billion years ago than its current speed of around 300,000 kilometers per second (about 186,000 miles per second).
The theory, published Thursday in the journal Nature, raises the possibility that light may have travelled at infinite speed at the time of the so-called Big Bang, which physicists say marks the creation point of the universe.
"It's entirely possible that the speed of light would have got greater and greater as you go back (through time) towards the Big Bang and if so it could explain some of the great mysteries of cosmology," he said.
"If the speed of light were nearly infinite in the first split second it would explain why the universe is so uniform, for example, on a large scale," he said.
If his theory stands up, Davies said, it would be the biggest scientific revolution since Albert Einstein's theory of relativity, which the new hypothesis would demolish.
One of the most important elements of Einstein's theory that energy equals mass multiplied by the speed of light squared (E=MC2) is that the speed of light — 'C' in the equation — is an absolute constant.
"Einstein would have absolutely hated this," Davies said. "His entire theory of relativity was founded on the notion that the speed of light is an absolute fixed universal number."
"If these results hold out, we need to start re-examining the very nature of space and time," he said.
"It also affects other branches of physics like thermodynamics and quantum physics, the very basis of all our fundamental physical theories — if these observations are correct — seem to be in the melting pot," he said.
Davies said it also needed to be tested whether light was continuing to slow or whether it had hit a cosmological "speed bump" billions of years ago.
