Showing posts with label Elburg. Show all posts
Showing posts with label Elburg. Show all posts

Monday, October 17, 2011

Whew!!! Faster-Than-Light Neutrinos Result of GPS Movement

Climb off that ledge, there was a mistake that allowed it to seem that neutrinos were observed traveling faster than light. It has to do with perspective and frames of reference. You have to remember to take into account when those reference frames are moving with respect to one another. This case: the neurtrinos were moving relative to earth but the satellites used to measure the neutrinos speed were moving with respect to both the neutrinos and the earth.

Although the speed of light is does not depend on the the frame of reference, the time of flight does. In this case, there are two frames of reference: the experiment on the ground and the clocks in orbit. If these are moving relative to each other, then this needs to be factored in.
So what is the satellites’ motion with respect to the OPERA experiment? These probes orbit from West to East in a plane inclined at 55 degrees to the equator. Significantly, that’s roughly in line with the neutrino flight path. Their relative motion is then easy to calculate.
So from the point of view of a clock on board a GPS satellite, the positions of the neutrino source and detector are changing. “From the perspective of the clock, the detector is moving towards the source and consequently the distance travelled by the particles as observed from the clock is shorter,” says van Elburg.
By this he means shorter than the distance measured in the reference frame on the ground.
The OPERA team overlooks this because it thinks of the clocks as on the ground not in orbit.
How big is this effect? Van Elburg calculates that it should cause the neutrinos to arrive 32 nanoseconds early. But this must be doubled because the same error occurs at each end of the experiment. So the total correction is 64 nanoseconds, almost exactly what the OPERA team observes.

Everyone can breathe now. Still nothing has been observed traveling faster than the speed of light!

Faster-Than-Light Neutrinos Result of GPS Movement
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