# Can neutrinos travel Faster Than Light **URL:** \ **Category:** Factual Questions\ **Created:** [September 22, 2011, 10:59pm UTC](https://boards.straightdope.com/t/can-neutrinos-travel-faster-than-light/597266 "2011-09-22T22:59:06Z")\ **Posts on this page:** 20\ **Page:** 3
**Author:** ![sevenwood](https://avatars.discourse-cdn.com/v4/letter/s/6de8d8/32.png) [@sevenwood](https://boards.straightdope.com/u/sevenwood)\ **Post date:** [September 23, 2011, 12:52pm UTC](https://boards.straightdope.com/t/can-neutrinos-travel-faster-than-light/597266/41 "2011-09-23T12:52:47Z")
> [@leahcim](#): > > I’d put a moderate wager on the results not being confirmed, though. i take it you’ve read today’s [XKCD](http://xkcd.com/955/). 😃 ---
**Author:** ![Jinx](https://avatars.discourse-cdn.com/v4/letter/j/c6cbf5/32.png) [@Jinx](https://boards.straightdope.com/u/Jinx)\ **Post date:** [September 23, 2011, 1:38pm UTC](https://boards.straightdope.com/t/can-neutrinos-travel-faster-than-light/597266/42 "2011-09-23T13:38:29Z")
I only wish I followed such things closer, but: (A) Isn’t Einsteins work predicated on the assumption all matter has mass? And, (B), didn’t he not like the idea proposed by his contemporaries that some subatomic particles sometimes have mass and sometimes don’t? And, in work after his lifetime, haven’t such subatomic particles been theorized to exist based on results from greater and greater studies with particle accelerators? If so, isn’t it possible scientists simply seeing the behavior of a massless particle that many always believed existed from all their theortical work? ---
**Author:** ![NineToTheSky](https://avatars.discourse-cdn.com/v4/letter/n/b5a626/32.png) [@NineToTheSky](https://boards.straightdope.com/u/NineToTheSky)\ **Post date:** [September 23, 2011, 1:42pm UTC](https://boards.straightdope.com/t/can-neutrinos-travel-faster-than-light/597266/43 "2011-09-23T13:42:15Z")
As others have mentioned, I don’t see how this affects causality. It’s not as if the neutrinos arrived before they had left. Could some kind person explain this for me? ---
**Author:** ![Grumman](https://avatars.discourse-cdn.com/v4/letter/g/43a26b/32.png) [@Grumman](https://boards.straightdope.com/u/Grumman)\ **Post date:** [September 23, 2011, 1:43pm UTC](https://boards.straightdope.com/t/can-neutrinos-travel-faster-than-light/597266/44 "2011-09-23T13:43:02Z")
> [@Darth\_Ayebaw](#): > > Like others have asked, what practical applications are there for this, assuming it’s true? I mean it’s ‘only’ 7.4km/s faster than c, so it’s not like we could send a message to Alpha Centauri and have it arrive in a few months. The practical application is that the answer might be “not yet” instead of “not ever”. If c is not an absolute limit as we believed, we might be back to incremental advances. If this one was only 7.4km/s faster than c, maybe it’s possible to get it up to 7.5km/s faster than c. And if we can get 7.5km/s faster than c, maybe we can get to 7.6km/s faster. And so on. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [September 23, 2011, 1:44pm UTC](https://boards.straightdope.com/t/can-neutrinos-travel-faster-than-light/597266/45 "2011-09-23T13:44:49Z")
While a very healthy dose of skepticism is of course justified, even with their six sigma claim, this would not, if I understand things at all correctly, “overturn” anything necessarily. “Tachyons” have always been a theoretical possibility within the current framework. This could merely provide some evidence that they are creating both neutrinos and tachyon-neutrinos, two populations one of which always travels below the speed of light and one that always travels above. Now that would be _exciting_ but not “overturning.” ---
**Author:** ![Half\_Man\_Half\_Wit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/half_man_half_wit/32/21766_2.png) [@Half\_Man\_Half\_Wit](https://boards.straightdope.com/u/Half_Man_Half_Wit)\ **Post date:** [September 23, 2011, 2:02pm UTC](https://boards.straightdope.com/t/can-neutrinos-travel-faster-than-light/597266/46 "2011-09-23T14:02:39Z")
The webcast of the OPERA collab’s talk at CERN is [live now](http://webcast.web.cern.ch/webcast/)… ---
**Author:** ![Tom\_Tildrum](https://avatars.discourse-cdn.com/v4/letter/t/e95f7d/32.png) [@Tom\_Tildrum](https://boards.straightdope.com/u/Tom_Tildrum)\ **Post date:** [September 23, 2011, 2:03pm UTC](https://boards.straightdope.com/t/can-neutrinos-travel-faster-than-light/597266/47 "2011-09-23T14:03:15Z")
> [@NineToTheSky](#): > > Subir Sarkar, head of particle theory at Oxford University, explained eloquently to the Guardian the significance of OPERA’s research. "If this is proved to be true it would be a massive, massive event. It is something nobody was expecting. > > “The constancy of the speed of light… underpins causality, which is the fact that cause comes before effect. Cause cannot come after effect and that is absolutely fundamental to our construction of the physical universe. If we do not have causality, we are buggered.” If we do not have causality, we might have been buggered already, and we just don’t know it yet. ---
**Author:** ![Hermitian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hermitian/32/470_2.png) [@Hermitian](https://boards.straightdope.com/u/Hermitian)\ **Post date:** [September 23, 2011, 2:35pm UTC](https://boards.straightdope.com/t/can-neutrinos-travel-faster-than-light/597266/48 "2011-09-23T14:35:37Z")
I remember reading some guy’s case a while back that the speed of light has been slowing down. Maybe it appears that they go faster than “c” becasue they haven’t measured “c” that accurately for a while. Not saying I have bought into such an idea, just throwing out crazy ideas like everyone else. ---
**Author:** ![Spatial\_Rift\_47](https://avatars.discourse-cdn.com/v4/letter/s/a8b319/32.png) [@Spatial\_Rift\_47](https://boards.straightdope.com/u/Spatial_Rift_47)\ **Post date:** [September 23, 2011, 2:52pm UTC](https://boards.straightdope.com/t/can-neutrinos-travel-faster-than-light/597266/49 "2011-09-23T14:52:41Z")
> [@NineToTheSky](#): > > As others have mentioned, I don’t see how this affects causality. It’s not as if the neutrinos arrived before they had left. Could some kind person explain this for me? Let’s suppose for the sake of answering your question that the neutrinos in the OPERA experiment really did exceed _c_, the universal speed limit, by 7.5 km/s. In this case, covering a distance of 730 km, that would mean they arrived after they left the emitter at CERN. But, it also means they have the potential ability to arrive before they are emitted. Take a gander at this: [space-time diagram](http://en.wikipedia.org/wiki/File:Minkowski_diagram_-_photon.svg). This is the standard way to plot causality in a handy graph. In such a graph, the units of distance and the units of time are equal, like 1 light-year and 1 year, so that a light ray traveling at _c_ makes a perfectly 45 degree diagonal line. Anything going faster than _c_ has a shallower slope. So imagine that there’s another line on that graph, slightly shallower than the yellow light ray, connecting two points E (emitter) and D (detector). E and D have their own space-time trajectories, called world-lines. Since E and D themselves are “at rest” (they have no relative velocity) their world-lines are just vertical lines at two points in space (on the x-axis). Now here’s the twist. If I accelerate the detector D, then it experiences less time than does E. That shifts E’s spacetime coordinate forward compared to D. Suppose I accelerate D dramatically, to .99999_c_. Now it’s way “behind” E in relative time elapsed. And there’s still a shallow slope line connecting them, because the neutrinos still go from emitter to detector. Only now, the slope of the neutrino line is so shallow, its slope is negative. The neutrinos have arrived before they departed. Bottom line: Even if we have FTL neutrinos in the OPERA results, they did not travel backwards in time. But according to the mechanisms and methods of Special Relativity, FTL travel opens the doorway to, or is equivalent to, breaking causality. ---
**Author:** ![KneadToKnow](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kneadtoknow/32/3999_2.png) [@KneadToKnow](https://boards.straightdope.com/u/KneadToKnow)\ **Post date:** [September 23, 2011, 3:04pm UTC](https://boards.straightdope.com/t/can-neutrinos-travel-faster-than-light/597266/50 "2011-09-23T15:04:28Z")
> [@ZenBeam](#): > > There could be neutrinos obeying the speed limit, and others traveling faster. I hereby propose we refer to the ones traveling faster than _c_ as _Porsche neutrinos_. ---
**Author:** ![leahcim](https://avatars.discourse-cdn.com/v4/letter/l/b4bc9f/32.png) [@leahcim](https://boards.straightdope.com/u/leahcim)\ **Post date:** [September 23, 2011, 3:10pm UTC](https://boards.straightdope.com/t/can-neutrinos-travel-faster-than-light/597266/51 "2011-09-23T15:10:31Z")
> [@NineToTheSky](#): > > As others have mentioned, I don’t see how this affects causality. It’s not as if the neutrinos arrived before they had left. Could some kind person explain this for me? But they did arrive before they left — in some reference frame. It’s a principle of relativity that if you see anything travelling faster than light, there is another reference frame in which you would see it travelling backwards in time. ---
**Author:** ![leahcim](https://avatars.discourse-cdn.com/v4/letter/l/b4bc9f/32.png) [@leahcim](https://boards.straightdope.com/u/leahcim)\ **Post date:** [September 23, 2011, 3:13pm UTC](https://boards.straightdope.com/t/can-neutrinos-travel-faster-than-light/597266/52 "2011-09-23T15:13:25Z")
> [@sevenwood](#): > > i take it you’ve read today’s [XKCD](http://xkcd.com/955/). 😃 Yeah, I used the causality violation created by those neutrinos to read today’s XKCD yesterday. 🙂 ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [September 23, 2011, 3:38pm UTC](https://boards.straightdope.com/t/can-neutrinos-travel-faster-than-light/597266/53 "2011-09-23T15:38:17Z")
> [@KneadToKnow](#): > > I hereby propose we refer to the ones traveling faster than _c_ as _Porsche neutrinos_. Nah. Clearly the car to allude to would have to be a DeLorean. ---
**Author:** ![colonial](https://avatars.discourse-cdn.com/v4/letter/c/34f0e0/32.png) [@colonial](https://boards.straightdope.com/u/colonial)\ **Post date:** [September 23, 2011, 3:43pm UTC](https://boards.straightdope.com/t/can-neutrinos-travel-faster-than-light/597266/54 "2011-09-23T15:43:30Z")
> [@colonial](#): > > Here is the first media skeptic I have been able to find who invokes science: > > Neutrino Blog > > Apparently there is a big discrepancy with inferred speed of neutrinos emitted > by Supernova 1987a, as in approx. one year: \*\*I mistakenly cited the difference’s margin of error rather than \*\*\*\*the difference itself \*\* \*\*in the last sentence above. The actual number \*\*\*\*4.14 ± 0.97 years is pretty much exactly \*\* **calculated in post #30 by naita, who deserves to be repeated, admiringly, in full:** > [@naita](#): > > If I’ve done the maths right and have the right information the neutrino discrepancy was 60 ns over the distance given, a 0.000025 in 1 difference from the speed of light. Applying that to 1987a’s distance of 168000 light years we get a **difference of 4.2 years**. So either the supralumial neutrinos result is wrong, or supernovas don’t send out neutrinos but 4.2 year old supernova remnants do, or neutrinos only go faster through planetary crusts. **Another member may also be on to something:** > [@Dseid](#): > > (post #45) > …“Tachyons” have always been a theoretical possibility within the current framework. This could merely provide some evidence that they are creating both neutrinos and tachyon-neutrinos… \*\*Maybe one of our specialists can comment \*\*\*\*on the \*\*\*\*following paper: \*\* [Hypothesis of Tachyonic Neutrinos](http://www.actaphys.uj.edu.pl/vol29/pdf/v29p0113.pdf) \*\*I think naita addressed the following in his post #30, quoted above: \*\* > [@ZenBeam](#): > > Regarding the neutrinos from Supernova 1987a, they wouldn’t know if some neutrinos arrived 4 +/- 1 years early. They only know that some arrived when expected. There could be neutrinos obeying the speed limit, and others traveling faster. > > I’m not sure how you’d theoretically get two discrete speeds, but that would (IMHO) seem to be an easier problem than FTL neutrinos in the first place. ---
**Author:** ![Grey](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Grey](https://boards.straightdope.com/u/Grey)\ **Post date:** [September 23, 2011, 3:46pm UTC](https://boards.straightdope.com/t/can-neutrinos-travel-faster-than-light/597266/55 "2011-09-23T15:46:46Z")
If I understand this correctly neutrinos moving faster than _c_ implies a breaking of Lorentz covariance. So if true the physics 1 observer sees would not be equivalent to another in a different frame of reference and there would be no way to transform the reference frames to make them line up. So, if this is true, does that means there would have to be some sort of fixed background field (like Newton’s old Tinkertoy clock framework) that these particles would have to exist within? ---
**Author:** ![John\_DiFool](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_difool/32/19543_2.png) [@John\_DiFool](https://boards.straightdope.com/u/John_DiFool)\ **Post date:** [September 23, 2011, 3:49pm UTC](https://boards.straightdope.com/t/can-neutrinos-travel-faster-than-light/597266/56 "2011-09-23T15:49:00Z")
> [@KneadToKnow](#): > > I hereby propose we refer to the ones traveling faster than _c_ as _Porsche neutrinos_. [Ludicrous Speed!](http://www.youtube.com/watch?v=mk7VWcuVOf0&feature=related) ---
**Author:** ![KneadToKnow](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kneadtoknow/32/3999_2.png) [@KneadToKnow](https://boards.straightdope.com/u/KneadToKnow)\ **Post date:** [September 23, 2011, 4:01pm UTC](https://boards.straightdope.com/t/can-neutrinos-travel-faster-than-light/597266/57 "2011-09-23T16:01:32Z")
> [@DSeid](#): > > Nah. Clearly the car to allude to would have to be a DeLorean. :smack: I sit corrected. ---
**Author:** ![Half\_Man\_Half\_Wit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/half_man_half_wit/32/21766_2.png) [@Half\_Man\_Half\_Wit](https://boards.straightdope.com/u/Half_Man_Half_Wit)\ **Post date:** [September 23, 2011, 4:16pm UTC](https://boards.straightdope.com/t/can-neutrinos-travel-faster-than-light/597266/58 "2011-09-23T16:16:26Z")
> [@colonial](#): > > [Hypothesis of Tachyonic Neutrinos](http://www.actaphys.uj.edu.pl/vol29/pdf/v29p0113.pdf) The problem with tachyonic neutrinos is that they should travel _faster_ the less energy they have, meaning that the 1987A neutrinos should have appeared here even more earlier – this seems to me to rule out the idea that neutrinos may travel faster then ‘c’, where I here mean ‘the speed of a massless particle’, or ‘the speed limit of special relativity’. As for two speeds of neutrino propagation, I’m also not certain how that could be made to work – neutrinos oscillate into one another, meaning that one kind of neutrino becomes another kind, so even if different neutrinos move at different speeds, these effects should even out. So then there’s the idea left that neutrinos travel faster than light, because light travels slower than c, i.e. because the photon is massive; but if that were the case, then light at different energies should travel at different speeds, and there are really good bounds on that happening… The bottom line for me then is, if this is a real effect, I can’t see any way to fit it into established physics. ---
**Author:** ![Don\_Roberto](https://avatars.discourse-cdn.com/v4/letter/d/e47774/32.png) [@Don\_Roberto](https://boards.straightdope.com/u/Don_Roberto)\ **Post date:** [September 23, 2011, 4:20pm UTC](https://boards.straightdope.com/t/can-neutrinos-travel-faster-than-light/597266/59 "2011-09-23T16:20:21Z")
I just watched the CERN seminar presenting the results. They are very serious about the result, and have done a very careful job accounting for the systematics, including multiple independent checks of their experimental timing chain by different metrology companies. The geodesy measurement was performed twice (apparently by the same team, it wasn’t made clear). That doesn’t mean they didn’t make a mistake somewhere, but if they did, it’s a subtle one. I for one am very much looking forward to future experiments to either confirm or not the result. ---
**Author:** ![zwede](https://avatars.discourse-cdn.com/v4/letter/z/ac91a4/32.png) [@zwede](https://boards.straightdope.com/u/zwede)\ **Post date:** [September 23, 2011, 4:25pm UTC](https://boards.straightdope.com/t/can-neutrinos-travel-faster-than-light/597266/60 "2011-09-23T16:25:21Z")
> [@Chronos](#): > > The neutrinos from 1987a arrived at darned near the same time as the light Maybe a silly question, but was anyone looking for neutrinos from 1987a 4 years **before** the light arrived on earth? We didn’t have any idea there would be a super nova until the light arrived. Could 1987a have created different types of neutrinos, some types which exceeded light speed? [Previous page](https://boards.straightdope.com/t/can-neutrinos-travel-faster-than-light/597266.md?page=2) [Next page](https://boards.straightdope.com/t/can-neutrinos-travel-faster-than-light/597266.md?page=4)