Merged Puzzling results from CERN

[I Ratant]

Any findings that "violate" SR will be investigated really well.
That's how science works.
It ain't gonna occur overnight.
Whatever the results, either showing a "violation" or an error, science will do the job.

 

[Anders Lindman]

I don't know if this has already been discussed, but the relative velocity between source and destination can be larger than the speed of light from the observer's point of view. See: http://www.internationalskeptics.com/forums/showpost.php?p=7631147&postcount=563

So if the source is moving slightly away in relation to the destination at CERN due to some geological drift, then when they measure the velocity they will get a result larger than the speed of light without violating Einstein's special relativity.

The velocity from the particles' point of view relative to the source will still be below the speed of light for neutrinos with mass. For example, the relative velocity between two photons traveling in opposite directions is 2c from the observer's point of view, but only 1c from the point of view of each photon relative to the other photon.

They most likely already have taken this into account, but anyway, it would be interesting to have it confirmed.

EDIT: I read now that the time difference measured by CERN is 60 nanoseconds. That would require one helluva mudslide. My mistake.

 

[sol invictus]

I don't know if this has already been discussed, but the relative velocity between source and destination can be larger than the speed of light from the observer's point of view. See: http://www.internationalskeptics.com/forums/showpost.php?p=7631147&postcount=563

Yes. I explained that to you at least five times in this thread (before the posts got moved). I'm glad you've finally understood it.

So if the source is moving slightly away in relation to the destination at CERN due to some geological drift, then when they measure the velocity they will get a result larger than the speed of light without violating Einstein's special relativity.

The difference in speed they measured is about one part in 100,000 of the speed of light. Light moves at about 186,000 miles/second. Hopefully, CERN and Gran Sasso aren't drifting towards each other at 2 miles/second.

Their distances measures are precise enough to easily measure geological motions. For instance, the earthquake in L'Aquila altered the distance by several cm, and they easily measured that.

 

[Anders Lindman]

Yes. I explained that to you at least five times in this thread (before the posts got moved). I'm glad you've finally understood it.



The difference in speed they measured is about one part in 100,000 of the speed of light. Light moves at about 186,000 miles/second. Hopefully, CERN and Gran Sasso aren't drifting towards each other at 2 miles/second.

Their distances measures are precise enough to easily measure geological motions. For instance, the earthquake in L'Aquila altered the distance by several cm, and they easily measured that.

Yes, I read now that the time difference measured by CERN is 60 nanoseconds. That would require one helluva mudslide.

 

[Soapy Sam]

Or you could have read post 100. We already ruled out crust creep.

 

[Anders Lindman]

Or you could have read post 100. We already ruled out crust creep.

Ok, 20 meters movement in a fraction of a second. Averaged over all measurements. Yeah, unless the source at CERN is moving on rails or something at that speed, lol, it can't explain such a large difference.

 

[Anders Lindman]

An amateurish question: How does the neutrino cannon at CERN work? Since the neutrinos have mass, the cannon would work like an ordinary cannon for cannonballs with the difference that Einstein's relativity equations must be used since the velocity of the neutrinos is so large. A cannon creates a huge acceleration at the time it's fired. So the velocity does not go from zero to full speed according to a stepwise function, but instead as a function of acceleration for the first few attoseconds or something like that. Has this acceleration been taken into account for the calculations at CERN? Or are the neutrinos measured on the fly so to speak, without any acceleration involved?

 

[Jono74]

An amateurish question: How does the neutrino cannon at CERN work? Since the neutrinos have mass, the cannon would work like an ordinary cannon for cannonballs with the difference that Einstein's relativity equations must be used since the velocity of the neutrinos is so large. A cannon creates a huge acceleration at the time it's fired. So the velocity does not go from zero to full speed according to a stepwise function, but instead as a function of acceleration for the first few attoseconds or something like that. Has this acceleration been taken into account for the calculations at CERN? Or are the neutrinos measured on the fly so to speak, without any acceleration involved?

Anders, please tell me you are just joking with that last comment...

 

[Drachasor]

Yes, I read now that the time difference measured by CERN is 60 nanoseconds. That would require one helluva mudslide.

And the sensors that measure the distance are sensitive enough to pick up continental drift. So they seem to be pretty good here.

 

[Drachasor]

An amateurish question: How does the neutrino cannon at CERN work? Since the neutrinos have mass, the cannon would work like an ordinary cannon for cannonballs with the difference that Einstein's relativity equations must be used since the velocity of the neutrinos is so large. A cannon creates a huge acceleration at the time it's fired. So the velocity does not go from zero to full speed according to a stepwise function, but instead as a function of acceleration for the first few attoseconds or something like that. Has this acceleration been taken into account for the calculations at CERN? Or are the neutrinos measured on the fly so to speak, without any acceleration involved?

They fire a barrage of protons at near the speed of light, which produce collisions over a distance on the order of a kilometer or so (they factor in the slower speed of the protons during generation, but this produced a very tiny possible difference). This makes a ton of high energy neutrinos and other particles which then continue on through the Earth. Neutrinos interact weakly with ordinary matter, so all the other particles collide with the Earth (there's no tunnel, it is going THROUGH the Earth). The Neutrinos continue on to the detector, most of them pass right though it, some of them collide. They have a profile of the what the initial collisions should be like, and they make a statistical comparison with the detections at the other end to determine the overall speed. They did this a lot to get solid statistical results.

However, it is possible there's some bias during the particle generation, during the trip, or at the detector which is unaccounted for. This would skew the statistical analysis and could explain what is going on.

I'm a little fuzzy on how they are setting up the actual collisions so I didn't go into detail on that. I'll have to look it up.

 

[Dancing David]

An amateurish question: How does the neutrino cannon at CERN work? Since the neutrinos have mass, the cannon would work like an ordinary cannon for cannonballs with the difference that Einstein's relativity equations must be used since the velocity of the neutrinos is so large. A cannon creates a huge acceleration at the time it's fired. So the velocity does not go from zero to full speed according to a stepwise function, but instead as a function of acceleration for the first few attoseconds or something like that. Has this acceleration been taken into account for the calculations at CERN? Or are the neutrinos measured on the fly so to speak, without any acceleration involved?

maybe you should read the thread over...

 

[Anders Lindman]

They fire a barrage of protons at near the speed of light, which produce collisions over a distance on the order of a kilometer or so (they factor in the slower speed of the protons during generation, but this produced a very tiny possible difference). This makes a ton of high energy neutrinos and other particles which then continue on through the Earth. Neutrinos interact weakly with ordinary matter, so all the other particles collide with the Earth (there's no tunnel, it is going THROUGH the Earth). The Neutrinos continue on to the detector, most of them pass right though it, some of them collide. They have a profile of the what the initial collisions should be like, and they make a statistical comparison with the detections at the other end to determine the overall speed. They did this a lot to get solid statistical results.

However, it is possible there's some bias during the particle generation, during the trip, or at the detector which is unaccounted for. This would skew the statistical analysis and could explain what is going on.

I'm a little fuzzy on how they are setting up the actual collisions so I didn't go into detail on that. I'll have to look it up.

Thanks. Good explanation.

 

[Tim Thompson]

Superluminal Neutrinos IV

I joined in the JPL Astrophysics Journal Club meeting last Friday and we had quite s discussion about the OPERA superluminal neutrinos claim. The group agreed by the end of the 40 minutes or so that the reported superluminal velocity is unreliable for reasons disclosed here: The OPERA neutrino velocity result and the synchronization of clocks; Carlo Contaldi, 28 Sep 2011 (v1), 29 Sep 2011 (v2).

There is a clock at each end of the experiment (one at CERN and one at Gran Sasso) that time stamps the data stream for that end of the experiment. The clock rates are synchronized to the GPS system, assuring that the two clocks "tick" at the same rate (1 second of time interval on either clock is 1 second of time interval as seen by the ensemble of GPS satellites). Furthermore, the clocks are initially synchronized by placing them together in the same place and simultaneously synchronizing both clocks to the same GPS satellites. This sets the rate on both clocks, and the offset between them in absolute time scale is also recorded. The two clocks are then moved to their respective locations. And therein lies the first part of the problem.

Sitting at the two ends of the experiment, the two clocks sit in different gravitational potentials and would naturally "tick" at different rates. That is compensated for by tying both clocks to the GPS signal, guaranteeing the same rate for both clocks. However, moving the clocks from their point of synchronization introduces a change in clock rate and therefore changes the previously measured offset in an essentially unpredictable manner that depends on the specific trajectory of the clocks through Earth's gravitational field. Re-synchronization to GPS at the final locations makes sure the clock rate is fixed, but does nothing to address the issue of the new offset between the two clocks.

According to the original OPERA paper (Measurement of the neutrino velocity with the OPERA detector in the CNGS beam; The OPERA Collaboration, 22 Sep 2011), the offset was tested by the German Physikalisch-Technische Bundesanstalt using a "portable time transfer device" (presumed to be a high precision atomic clock) and found to be 2.3 +/- 0.9 nano-seconds (preprint page 9). However, the portable time transfer device, whatever it is, has still to be moved between the two ends of the experiment in Switzerland & Italy. There will be an offset induced between the reported absolute times between the two ends of the experiment, because of the motion of the portable time transfer device through Earth's gravitational potential. This offset depends on the trajectory of the clock through Earth's gravitational field, and is actually the sum of several effects due not just to the gravitational field, but the fact that Earth is rotating (i.e., the Sagnac effect has also to be considered). It is a big job to reliably calculate this offset induced in the portable time transfer device, as well as the initial offset induced by moving the two clocks from their original synchronization point.

Note that in the original OPERA paper, the authors note that the absolute GPS time scale cannot be set absolutely between the two sites with higher precision than about 100 nano-seconds (preprint page 9) because of differences induced by propagation of the GPS signal through the atmosphere. The portable time transfer device is intended to circumvent this problem, and get the offset down to the reported value of ~2 nano-seconds. But it appears that the clock synchronization process actually employed cannot determine the offset in fact any better than this ~100 nano-seconds, which puts the ~60 nano-second "early arrival" of the neutrinos well inside the range of uncertainty in the offset between the two clocks.

I find it quite interesting that modern technology has reached the point where relativistic effects, perhaps previously considered obscure & esoteric, are now center stage in determining experimental precision in a really important & fundamental way.

 

[I Ratant]

The two clocks... that's the flaw.
If there were a way to reflect the neutrinos back to the source, so only one clock is involved...

 

[sol invictus]

Note that in the original OPERA paper, the authors note that the absolute GPS time scale cannot be set absolutely between the two sites with higher precision than about 100 nano-seconds (preprint page 9) because of differences induced by propagation of the GPS signal through the atmosphere.

I missed that - I had thought GPS-derived clocks were much more accurate than that.

I'm now a little confused how GPS can ever give accuracy of better than 20 meters.... it relies on phase differences between signals from several satellites, and since those signals must pass through different parts of the atmosphere, wouldn't there be a 100ns = 30m uncertainty in all GPS positions? And yet, you can get cm accuracy.

Maybe that's because the atmospheric differences average out over time, but if so, why wouldn't the same apply to the clock synchs?

 

[Anders Lindman]

Anders, please tell me you are just joking with that last comment...

Oh, my mistake. Measuring neutrinos on the fly at the source would greatly change the neutrinos themselves now that I think about it. The neutrinos are sent out by colliding protons at high speed. That might involve a kind of acceleration phase for the neutrinos for the first few attoseconds perhaps. An acceleration that has to be calculated relativistically, including quantum mechanics effects.

 

[Drachasor]

I missed that - I had thought GPS-derived clocks were much more accurate than that.

I'm now a little confused how GPS can ever give accuracy of better than 20 meters.... it relies on phase differences between signals from several satellites, and since those signals must pass through different parts of the atmosphere, wouldn't there be a 100ns = 30m uncertainty in all GPS positions? And yet, you can get cm accuracy.

Maybe that's because the atmospheric differences average out over time, but if so, why wouldn't the same apply to the clock synchs?

You take a TON of measurements and average them together, essentially. You can get really good numbers doing that.

 

[Anders Lindman]

Note that in the original OPERA paper, the authors note that the absolute GPS time scale cannot be set absolutely between the two sites with higher precision than about 100 nano-seconds (preprint page 9) because of differences induced by propagation of the GPS signal through the atmosphere. The portable time transfer device is intended to circumvent this problem, and get the offset down to the reported value of ~2 nano-seconds. But it appears that the clock synchronization process actually employed cannot determine the offset in fact any better than this ~100 nano-seconds, which puts the ~60 nano-second "early arrival" of the neutrinos well inside the range of uncertainty in the offset between the two clocks.

100 nanoseconds sounds like a huge margin of error for clocks used for this super advanced scientific experiment at CERN.

 

[Tim Thompson]

Superluminal Neutrinos V

I missed that - I had thought GPS-derived clocks were much more accurate than that.

100 nanoseconds sounds like a huge margin of error for clocks used for this super advanced scientific experiment at CERN.

It's the difference between an absolute measurement and a differential measurement. The 100 nano-second precision applies only to establishing the absolute time, as in "it is now 5 o'clock plus or minus 100 nano-seconds". However, if you ask what the difference is between multiple clocks, then yo can do much better. That's how differential GPS works, as I recall. That's how the GPS networks used to measure continental drift and earthquake offsets work.

 

[Anders Lindman]

It's the difference between an absolute measurement and a differential measurement. The 100 nano-second precision applies only to establishing the absolute time, as in "it is now 5 o'clock plus or minus 100 nano-seconds". However, if you ask what the difference is between multiple clocks, then yo can do much better. That's how differential GPS works, as I recall. That's how the GPS networks used to measure continental drift and earthquake offsets work.

Still, it can't be the first time in the history of science where high precision clock sync over vast distances has been needed for scientific experiments. Seems a bit suspect to me.