Speed-of-light experiment 'was wrong after all'
An experiment which appeared to contradict Einstein by showing that particles could travel faster than the speed of light is wrong after all, a rival group of scientists says.
7:39PM GMT 21 Nov 2011
52 CommentsThe claim comes from an independent team of researchers working at the Gran Sasso facility in Italy – the same laboratory as the group who shocked the world with their physics-defying announcement in September.
That experiment, known as OPERA, seemed to show that tiny particles known as neutrinos fired from the CERN research centre in Switzerland had arrived at Gran Sasso a fraction of a second faster than light would have done.
Because Einstein's theory of special relativity states that nothing can travel faster than light, the results run contrary to an assumption on which much of modern physics is based.
Proof that the OPERA team was correct would fundamentally alter our understanding the universe and raise the alarming possibility of time travel.
Amid widespread scepticism from the scientific community, the researchers challenged the world to prove them wrong, and last week announced they had run a slightly modified version of their experiment which produced the same result.
But now another group of scientists conducting a separate study on the same beam of neutrinos at Gran Sasso claims their findings "refute a superluminal (faster than light) interpretation of the OPERA result."
Rather than measuring the time it took the neutrinos to travel from CERN to Gran Sasso the second experiment, known as ICARUS, monitored how much energy they had when they arrived.
Physicists believe that travelling even slightly faster than light would cause the particles to lose most of their energy in the process.
But the ICARUS team's calculations, published online last weekend, seemed to show they arrived with exactly the amount of energy particles moving at light speed should have had – and no more.
Tomasso Dorigo, a CERN physicist, wrote on the Scientific Blogging website that the ICARUS paper was "very simple and definitive."
He said it showed "that the difference between the speed of neutrinos and the speed of light cannot be as large as that seen by OPERA, and is certainly smaller than that by three orders of magnitude, and compatible with zero."
Prof Jim Al-Khalili, the University of Surrey, who threatened to eat his boxer shorts if the original OPERA result was proved right, said: "Usually we see this effect when particles go faster than light through transparent media like water, when light is considerably slowed down.
"So these neutrinos should have been spraying out particles like electrons and photons in a similar way if they were going superluminal – and in the process would be losing energy.
"But they seemed to have kept the energy they started from, which rules out faster-than-light travel."
