Friday, March 23, 2012

Neutrinos must be slower than light

The UK BBC reports on the Faster-than-light neutrino anomaly:
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. ...

"We are completely compatible with the speed of light that we learn at school," said Sandro Centro, co-spokesman for the Icarus collaboration. ...

"In fact I was a little sceptical since the beginning," he told BBC News. "Now we are 100% sure that the speed of light is the speed of neutrinos."
Physicist Michio Kaku writes:
Headlines blared that Einstein, an iconic figure in science for a century, was finally proven wrong. The world of physics was thrown into turmoil because the bedrock of modern physics would disintegrate if that were true. My research is in string theory, for example, which extends Einstein's theory of relativity. So if his theory is wrong, my own life's work would go out the window as well. ...

But the floodgates finally burst open last week when a second group of physicists announced that they redid the entire experiment and found that Einstein was correct all along: Their neutrinos traveled at precisely the speed of light, not faster or slower.

This is not correct. The consensus is that neutrinos have rest mass:
All evidence suggests that neutrinos have mass but that their mass is tiny even by the standards of subatomic particles. Their mass has never been measured accurately.
Relativity requires that all massive particles go slower than the speed of light. Neutrinos do not travel at the speed of light.

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