An experiment to repeat a test of the speed of subatomic particles known as neutrinos has found that they do not travel faster than light. Results announced in September suggested that neutrinos can exceed light speed, but were met with scepticism as that would upend Einstein's theory of relativity.
A test run by a different group at the same laboratory has now clocked them travelling at precisely light speed. The results have been posted online.
The results in September, from the Opera group at the Gran Sasso underground laboratory in Italy, shocked the world, threatening to upend a century of physics as well as relativity - which holds the speed of light to be the Universe's absolute speed limit.
Now the Icarus group, based at the same laboratory, has weighed in again, having already cast some doubt on the original Opera claim. more...