From Tony Cheney
Perhaps an explanation for the anomalous velocity of neutrinos from CERN to Gran Sasso in Italy (1 October, p6), compared with the velocity of light in a vacuum, depends on what you mean by a vacuum. Measurements of the speed of light in a vacuum may have a hidden error. We all know these days that the vacuum is not empty – it is an energy field seething with virtual particles.
Perhaps light, when ploughing through the vacuum, is slower by 60 billionths of a second than neutrinos covering the same distance. Since neutrinos can zip through Earth as if it weren’t there, the quantum vacuum isn’t going to bother them much.
From Roger Schafir
The first reaction of many physicists, unsurprisingly, has been to doubt the neutrino experiment. And indeed, such an incredibly delicate experiment could be wrong. But never underestimate the skill of modern experimentalists. They have, after all, tested the theory of quantum electrodynamics with an accuracy equivalent to measuring the distance from London to New York to within the width of a human hair.
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London, UK
From Tim Hely
In his technology story, Jeff Hecht reports that light travels “just 330 metres” in one microsecond (1 October, p 24). I find this quite impressive as, traditionally, light would travel no more than 299.8 metres in that time. Now that it has competition from speedy neutrinos, has light done some extra sprint training?
Edinburgh, UK
Ipswich, Suffolk, UK
