London: Time travel will remain a sci-fi fantasy, according to scientists who claim to have proved that nothing can travel faster than the speed of light.
An international team says their findings reveal that a single photon obeys Albert Einstein's traffic law of the universe - thus putting an end to a decade-long debate about speed of a single photon, the fundamental unit of light.
Einstein claimed that the speed of light was the traffic law of the universe - or, simply, that nothing can travel faster than light.
"The results add to our understanding of how a single photon moves. They also confirm the upper bound on how fast information travels with light.
"By showing that single photons cannot travel faster than the speed of light, our results bring a closure to the debate on the true speed of information carried by a single photon," lead scientist Shengwang Du of Hong Kong University of Science and Technology, was quoted by the 'Daily Mail'.
In fact, the team claims to be the first to show that optical precursors exist at the single-photon level, and that they're the fastest part of the single-photon wave packet even in a "superluminal" - or faster than light - medium.
Mankind's long-held dream of time travel was given a shot in the arm 10 years ago with discovery of superluminal propagation of optical pulses in some specific medium. But, it was later realised that it is only a visual effect - where the superluminal ‘group’ velocity of many photons couldn't be used for transmitting any real information.
Researchers then set their hope on single photons because of the possibility that a single photon may be able to travel faster. Due to a lack of evidence of single photon velocity, this has also been an open debate among physicists.
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