Merged Puzzling results from CERN

[Hellbound]

I think the cynic in every physicist is going: "Oh great another case of mistaken measurement making us targets for every kook and nut bar out there."

At the exact same time, the giddy school kid in every physicist is going: "New physics! new physics! new physics! this is going to be soooooo awesome!"

^This²

 

[rjh01]

I'm trying, for my own edification, to enumerate the possible outcomes of this ....

1) A mistake was made and the neutrinos didn't arrive faster than they would have traveling at the speed of light.

2) The "speed of light" speed limit was broken - and, therefore, isn't really a limit.

3) The value we've been using as the speed of light is wrong.

4) The neutrinos traveled at less than the speed of light, but took a short-cut through space.

5) ... any other options?

Whatever the result, it's obvious we're going to learn something important.

-- Roger

5) Someone made a deliberate error which has not been detected. This is different from 1 above because this is a deliberate error rather than an accidental error.

6) GPS gave the wrong space time co-ordinates. This is different from 1 above because this error is outside of the experiment.

 

[Anders Lindman]

5) Someone made a deliberate error which has not been detected. This is different from 1 above because this is a deliberate error rather than an accidental error.

That was a clever one. I didn't think of that possibility. Maybe unlikely but interesting alternative.

 

[Michael Mozina]

....Sitting at the two ends of the experiment, the two clocks sit in different gravitational potentials and would naturally "tick" at different rates. .....

......

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.

That was a really nice explanation Tim. Thanks.

 

[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.

They do not say that, and it isn't true.

Instead, they say that it's true for standard GPS receivers. With specialized receivers, which they used, the accuracy is of order a ns - and that can probably be improved further.

That explains my confusion about your comment.

Why doesn't the same averaging work as well for a derived clock synch, then?

It's a differential measurement between signals received from different satellites, which obviously travelled through different paths in the atmosphere. So why aren't those measurements also affected by this 100ns uncertainty?

Something isn't quite adding up here.

 

[dasmiller]

They do not say that, and it isn't true.

Instead, they say that it's true for standard GPS receivers. With specialized receivers, which they used, the accuracy is of order a ns - and that can probably be improved further.

According to my sources (which work in meters, not ns), a consumer-grade single-frequency GPS receiver could see an instantaneous timing error of up to ~100 ns on a bad day at sea level. Averaging would reduce that substantially, as would simply waiting for a good day (~5 ns) or, of course, being well above sea level. A dual-frequency receiver would reduce the error dramatically, although it would not reduce it to zero. The GPS almanac (part of the GPS signal) includes some iono/tropo correction information, but I don't know how complete it is. Finally, working from memory, I believe that there are sources that publish measurement-based parameters for iono/tropo correction models that are used for post-processing GPS data if you're not in a hurry.

So <1 ns error due to atmospheric effects sounds very doable to me for a fixed site with a good budget and some time. Of course, that's <1 ns at the antenna of the GPS receiver.

ETA: The above was strictly for atmospheric effects. Of course, there are many sources of error and many mitigations.

 

[sol invictus]

According to my sources (which work in meters, not ns), a consumer-grade single-frequency GPS receiver could see an instantaneous timing error of up to ~100 ns on a bad day at sea level. Averaging would reduce that substantially, as would simply waiting for a good day (~5 ns) or, of course, being well above sea level. A dual-frequency receiver would reduce the error dramatically, although it would not reduce it to zero. The GPS almanac (part of the GPS signal) includes some iono/tropo correction information, but I don't know how complete it is. Finally, working from memory, I believe that there are sources that publish measurement-based parameters for iono/tropo correction models that are used for post-processing GPS data if you're not in a hurry.

So <1 ns error due to atmospheric effects sounds very doable to me for a fixed site with a good budget and some time. Of course, that's <1 ns at the antenna of the GPS receiver.

ETA: The above was strictly for atmospheric effects. Of course, there are many sources of error and many mitigations.

Thanks for the information. That's consistent with what I had thought.

 

[Sati1984]

So any news on a second experiment which will try to confirm the result?

 

[Cuddles]

So any news on a second experiment which will try to confirm the result?

They haven't even published this result yet. Big experiments like this aren't something you throw together in a few days. Unless they manage to find an error somewhere, there's very little chance of us seeing confirmation one way or the other for at least a few years.

 

[aggle-rithm]

They haven't even published this result yet. Big experiments like this aren't something you throw together in a few days. Unless they manage to find an error somewhere, there's very little chance of us seeing confirmation one way or the other for at least a few years.

Why do scientists take years to come to conclusions, when a McDonald's employee can make a hamburger in two minutes?

Is the McDonald's employee smarter?

 

[Dave Rogers]

Why do scientists take years to come to conclusions, when a McDonald's employee can make a hamburger in two minutes?

Pointy Haired Boss: Why does it take us months to develop software, when frying potato chips only takes a couple of minutes?

Tina the Technical Writer: I think they oil the chips.

Dave

 

[Michael Mozina]

Thanks for the information. That's consistent with what I had thought.

http://xxx.lanl.gov/abs/1109.6160

I think you'll like that paper.

 

[sol invictus]

http://xxx.lanl.gov/abs/1109.6160

I think you'll like that paper.

Thanks - I saw that before. At first I thought there might be something to it. But given that the GPS-derived clock agrees with the transported clock at closer than 3ns accuracy, it's hard to see how that can be the problem.

Still, it should certainly be checked, and it is remarkable that these tiny relativistic effects are some important here.

 

[Verde]

They haven't even published this result yet. Big experiments like this aren't something you throw together in a few days. Unless they manage to find an error somewhere, there's very little chance of us seeing confirmation one way or the other for at least a few years.

I agree, but also wonder if there even exist other facilities in the world that have the capability of replicating this experiment.

V.

 

[Malfie Henpox]

This is all very exciting. What's the general feeling? Error? Dimension swapping? It really happened?

I hope it holds up to scrutiny. It's the first time since Higgs Boson made the news that I've heard people talking science in the pub. Sure, they all thought CERN was going to destroy the universe. But still.

 

[rjh01]

This is all very exciting. What's the general feeling? Error? Dimension swapping? It really happened?

I hope it holds up to scrutiny. It's the first time since Higgs Boson made the news that I've heard people talking science in the pub. Sure, they all thought CERN was going to destroy the universe. But still.

I give you two choices.
1. The result is wrong.
2. The result is right.

1. Cannot be correct. The results have been checked and no errors can be found.
2. Cannot be correct. It would require certain well tested theories to be amended. It also conflicts with what was found when a star went super-nova in 1987.

Maybe not the universe being destroyed, maybe just what certain people know is wrong.

 

[Anders Lindman]

I give you two choices.
1. The result is wrong.
2. The result is right.

1. Cannot be correct. The results have been checked and no errors can be found.
2. Cannot be correct. It would require certain well tested theories to be amended. It also conflicts with what was found when a star went super-nova in 1987.

Maybe not the universe being destroyed, maybe just what certain people know is wrong.

"And there’s the rub: what we observed with Supernova 1987A (which was observed by astronomers in 1987 all over the world in real time) is not at all consistent with the findings of the CERN-OPERA group, because if these FTL results are to be believed then the neutrinos blasted out of Supernova 1987A should have been observed somewhere around 3 to 4 YEARS before the light from the explosion. And that didn’t happen… we observed the light from Supernova 1987A and related neutrino blast at essentially the same time." -- http://skepticalteacher.wordpress.com/tag/supernova-1987a/

BUT, I read somewhere that there are different kinds of neutrinos with different mass if I remember correctly. Then a bunch of neutrinos maybe traveled faster than the speed of light and did hit Earth 3 to 4 years before the light from the supernova and another bunch of neutrinos traveled slower and essentially with the speed of light. Just that nobody on Earth was measuring the faster kind of neutrinos back then.

 

[sol invictus]

"And there’s the rub: what we observed with Supernova 1987A (which was observed by astronomers in 1987 all over the world in real time) is not at all consistent with the findings of the CERN-OPERA group, because if these FTL results are to be believed then the neutrinos blasted out of Supernova 1987A should have been observed somewhere around 3 to 4 YEARS before the light from the explosion. And that didn’t happen… we observed the light from Supernova 1987A and related neutrino blast at essentially the same time." -- http://skepticalteacher.wordpress.com/tag/supernova-1987a/

BUT, I read somewhere that there are different kinds of neutrinos with different mass if I remember correctly. Then a bunch of neutrinos maybe traveled faster than the speed of light and did hit Earth 3 to 4 years before the light from the supernova and another bunch of neutrinos traveled slower and essentially with the speed of light. Just that nobody on Earth was measuring the faster kind of neutrinos back then.

The "different" species of neutrino oscillate into each other as neutrinos propagate. That's the effect that OPERA was actually built to see, but in any case, it's been observed by other experiments. So even if one species propagates faster than light and the other at the speed of light (which raises all sorts of problems, but never mind), the average speed is still going to be significantly faster than light, and hence almost certainly ruled out by 1987A.

A slightly more likely-to-succeed explanation is a strong energy dependence to the speed. 1987A's neutrinos were much lower energy than the ones OPERA detected.

ETA - on second thought, I'm not sure what I said is correct. The "average" speed may not be the speed deduced from any given detection (instead, you might always find one speed or the other, but never the average), since the neutrino wavefunction should be able to remain coherent as it propagates.

 

[phunk]

I give you two choices.
1. The result is wrong.
2. The result is right.

1. Cannot be correct. The results have been checked and no errors can be found.
2. Cannot be correct. It would require certain well tested theories to be amended. It also conflicts with what was found when a star went super-nova in 1987.

Maybe not the universe being destroyed, maybe just what certain people know is wrong.

I disagree with you on #1. No errors have been found, that doesn't mean no errors can be found.

 

[Anders Lindman]

The "different" species of neutrino oscillate into each other as neutrinos propagate. That's the effect that OPERA was actually built to see, but in any case, it's been observed by other experiments. So even if one species propagates faster than light and the other at the speed of light (which raises all sorts of problems, but never mind), the average speed is still going to be significantly faster than light, and hence almost certainly ruled out by 1987A.

A slightly more likely-to-succeed explanation is a strong energy dependence to the speed. 1987A's neutrinos were much lower energy than the ones OPERA detected.

ETA - on second thought, I'm not sure what I said is correct. The "average" speed may not be the speed deduced from any given detection (instead, you might always find one speed or the other, but never the average), since the neutrino wavefunction should be able to remain coherent as it propagates.

Ok, if the different neutrinos interact with each other then maybe they travel in a whole spectrum of different speeds, and what they measured from the 1987A supernova was only the end of the spectrum (the slowest part).