Neutrinos clocked at light-speed in new Icarus test

[muriel_volestrangler]

Last edited Fri Mar 16, 2012, 12:55 PM - Edit history (1)

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.

http://www.bbc.co.uk/news/science-environment-17364682

[bananas]

1. "precisely light speed" would violate relativity because they have mass. nt

[longship]

2. Neutrinos have mass, so...

...they can't travel at the speed of light. However, their mass is very low so it's possible that neutrinos could travel close to the speed of light.

The questions here are:

1. What are the accuracies of these velocity measurements?

2. Do the inaccuracies allow relativity to still hold?

3. This experiment is at the extreme cutting edge. Are there other systematic biases in the experimental protocol?

4. Answer likewise questions for the mass experiments.

Only then would I even entertain the possibility that relativity is wrong. There's something screwy here, but it would take something extraordinary if neutrinos both have non-zero mass and travel at light speed.

[muriel_volestrangler]

3. The average difference from the time of arrival for 'precisely the speed of light' was 0.4ns

and the estimated systematic error is ~9ns (of 7 measurements, 3 were slower, 3 faster, and one was spot on, to the nearest nanosecond). That compares with the earlier OPERA results that had the neutrinos arriving about 58ns early, but with systematic errors still under 10ns.

So this experiment is saying it's as close to the speed of light as we can measure it, and therefore can be fractionally under it, with no theoretical problems; the other experiment said it looked to be consistently faster than light.

[bananas]

4. So FTL is well within the error bounds. nt

[muriel_volestrangler]

6. Yes, but not the range that the earlier experiment got

If this had been the only set of results, no-one would have thought it remarkable at all.

[longship]

5. That's what I was thinking it would be

In other words, it looks like relativity holds...

...for now.

[ladjf]

7. Hey, that's still hauling ass. nt