Scientists at CERN believe they have clocked subatomic particles travelling faster than the speed of light, invalidating a tenet of Albert Einstein's theory of relativity.
The team said a neutrino fired from a particle accelerator near Geneva to a lab 730 km (454 miles) away in Italy travelled 60 nanoseconds faster than the speed of light, a speed which Einstein believed could never be exceeded.
A margin for error was calculated to be just 10 nanoseconds, meaning the results are statistically significant and could lead to the unpinning of one of the cornerstones of the laws of physics.
Einstein believed that nothing could travel faster than light - 300,000 km (186,282 miles) per second - and he reasoned that anything travelling faster than the speed of light would theoretically arrive before it set off.
"This would be such a sensational discovery, if it were true, that one has to treat it extremely carefully," said physicist John Ellis. Special relativity underlies "pretty much everything in modern physics. It has worked perfectly up until now," he added.
Before claiming the discovery as fact, the researchers have asked that the data they have collected be independently verified.
"We have not found any instrumental effect that could explain the result of the measurement," physicist Antonio Ereditato said.