More Evidence Against Those Supposed “Faster-Than-Light” Neutrinos

In the ongoing story of the supposedly “faster-than-light” neutrinos discovered last year, there is another big mark against this claim being the real thing: the failure to replicate the phenomenon in an independent experiment.  As I stated then, most especially when dealing with an extraordinary claim such as this, one cannot begin to draw any conclusions until there have been separate, independent attempts to verify and replicate the results.  Until then, we should suspend judgment and remain skeptical of extraordinary claims.

Well, more of that judgment is now in… in a recent BBC News article, it is reported that a team (called Icarus) independent from the original research team (called Opera) from the same facility, Gran Sasso, in Italy failed to find the apparent “faster-than-light” signal which caused such an uproar last September:

Neutrinos clocked at light-speed in new Icarus test

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.

The results in September, from the Opera group at the Gran Sasso underground laboratory in Italy, shocked the world, threatening to upend a century of physics as well as relativity – which holds the speed of light to be the Universe’s absolute speed limit.

Now the Icarus group, based at the same laboratory, has weighed in again, having already cast some doubt on the original Opera claim. …

This is an excellent example of how real science, especially cutting-edge science, progresses.  Claims are not taken at face value; they are always open to criticism and are not necessarily accepted (especially if they go against well-established theories such as Einstein’s relativity) without good, strong, repeatable evidence.

In short, as Carl Sagan stated: “Extraordinary claims require extraordinary evidence.”

And the evidence in support of the claims of “faster-than-light” neutrinos seems to be getting less extraordinary every day.

“Faster Than Light” Neutrinos Likely the Result of a Bad Cable Connection

**Update (2-25-12):  It seems the situation is a bit more complicated than previously thought, and there is another potential source of error that has been discovered.  More details at this CERN link:  http://press.web.cern.ch/press/PressReleases/Releases2011/PR19.11E.html

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Last September you may recall quite a bit of buzz going around about the supposed discovery of faster-than-light neutrinos.  While the media was going nuts about it, and while various cranks were crowing about “the physics establishment being overturned”, a number of scientists and science bloggers (including me) expressed great interest in this experimental result while also providing a cautious dose of skepticism about the entire affair.  That’s because a theory that is so well-tested as Einstein’s relativity could be overturned or radically adjusted by such a result only if we were absolutely sure of the outcome; and, at the time, not even the scientists who announced the FTL result were very sure of it…

This tended to be the general view among physicists about the apparent “faster-than-light” neutrinos 🙂

Well, it seems our skepticism was well-founded.  From a recent post on the Science Insider blog, it looks as if the “faster-than-light” neutrino signal (which amounted to a discrepancy of 60 nanoseconds or 0.000 000 060 seconds) was probably the result of a bad cable connection…

BREAKING NEWS: Error Undoes Faster-Than-Light Neutrino Results

It appears that the faster-than-light neutrino results, announced last September by the OPERA collaboration in Italy, was due to a mistake after all. A bad connection between a GPS unit and a computer may be to blame.

Physicists had detected neutrinos travelling from the CERN laboratory in Geneva to the Gran Sasso laboratory near L’Aquila that appeared to make the trip in about 60 nanoseconds less than light speed. Many other physicists suspected that the result was due to some kind of error, given that it seems at odds with Einstein’s special theory of relativity, which says nothing can travel faster than the speed of light. That theory has been vindicated by many experiments over the decades.

According to sources familiar with the experiment, the 60 nanoseconds discrepancy appears to come from a bad connection between a fiber optic cable that connects to the GPS receiver used to correct the timing of the neutrinos’ flight and an electronic card in a computer. After tightening the connection and then measuring the time it takes data to travel the length of the fiber, researchers found that the data arrive 60 nanoseconds earlier than assumed. Since this time is subtracted from the overall time of flight, it appears to explain the early arrival of the neutrinos. New data, however, will be needed to confirm this hypothesis. [emphasis added]

If true (and my money is on it being true), it wouldn’t surprise me at all. When I was an undergraduate doing research work in a mass spectrometry lab, it took me and my lab mate a couple of days to figure out why the damn thing wasn’t working properly. After almost two days of checking everything (every setting, every seal on the chamber, every line of code), what was the error?

Answer: a bad BNC cable *facepalm*

And I was just working on a lousy table-top sized mass spectrometer.  I can barely imagine the level of complexity in dealing with an experiment of the scale of the CERN-OPERA operation; the fact that they could have missed a lone, loose fiber optic cable doesn’t surprise me at all.

While I’m pretty certain that this error (or similar ones) will explain the situation, I still think it is worthy for some outside research group to attempt a replication of the original, apparent FTL neutrino result.  I say that because it could be worth really nailing down exactly what went wrong in this whole experiment so that other researchers don’t make similar mistakes in the future.  Of course, there is the outside chance (however infinitely remote that may be) that perhaps there is something legitimate to the FTL result.

Either way, science marches on and we learn something about the universe.  Neat, eh? 🙂

FTL Neutrinos, Skepticism, and Humor

Regarding my previous blog post on the supposed discovery of faster-than-light neutrinos at CERN, I just wanted to share this humorous bit from the web-comic XKCD which sums it all up quite nicely.  Enjoy! 😀

Let’s Go Slow on CERN Faster-Than-Light Claims

[**Update: If you are looking for the actual research paper on the CERN-OPERA experiment and related “FTL” result, click here.]

[**Update (9-24-11): Here is an interesting critique of the statistical analysis used by the CERN-OPERA team which seems to cast considerable doubt on their FTL claims.]

[**Update (9-25-11): It seems the criticism above was flawed, and the author has retracted his criticism.  See the same link for the retraction.]

Okay, so there is a huge amount of buzz on the Interwebs concerning a potentially paradigm-shifting discovery at the CERN physics laboratory in Europe: faster-than-light (FTL) travel.  However, before we start to engage the warp drive engines and get too terribly excited, let’s – pardon the pun – slow things down a bit and look a bit more deeply at the claims.  The specific claims are outlined at this NPR report:

Scientists at the world’s largest physics lab said Thursday they have clocked neutrinos traveling faster than light. That’s something that according to Einstein’s 1905 special theory of relativity — the famous E (equals) mc2 equation — just doesn’t happen.

The particles in question are called neutrinos.  These particles are most often generated in the cores of stars as part of the process of nuclear fusion, though they can be generated in other particle interactions.  Some of the most interesting things about neutrinos is that they are extremely low mass, and they have no charge.  As a result, they don’t really interact with matter and are thus very difficult to detect (though we have methods for doing just that).  The other really interesting thing about neutrinos is that they undergo what is called oscillation – which means that as they travel through space they are able to morph from one kind of neutrino to another.  These three varieties of neutrino are called tau, electron, and muon neutrinos.

This is important to understand given the context of the experiment which has supposedly yielded the FTL result.  Here are the details about the experiment and its results (from the aforementioned NPR article):

CERN says a neutrino beam fired from a particle accelerator near Geneva to a lab [called OPERA] 454 miles (730 kilometers) away in Italy traveled 60 nanoseconds faster than the speed of light. Scientists calculated the margin of error at just 10 nanoseconds, making the difference statistically significant. But given the enormous implications of the find, they still spent months checking and rechecking their results to make sure there was no flaws in the experiment.

Now the physics community is understandably skeptical of these results, as it should be.  Einstein’s theory of relativity is a very solid theory, and – as far as I know – there hasn’t every been an experimental result shown which has violated this theory.  And here we have an experimental result which claims that one of relativity’s fundamental postulates – that the speed of light is invariant (i.e. always the same in all frames of reference) – is potentially wrong.  From this point, I see that there are two possibilities:

1. There is some kind of flaw in the design and/or implementation of the CERN-OPERA experiment which the researchers have overlooked.  It is also possible they have some kind of error in their calculations which accounts for the apparent FTL result.

2. There is no experimental/calculation error on the part of the research team, and this result is found to be repeatable by other research groups.

Personally, I am more inclined to #1 at this point, for multiple reasons.  First, as I mentioned above, Einstein’s relativity theory is such a fundamental basis for modern physics, and it has stood up to such rigorous scrutiny over the 20th century and beyond, that it would take much more than this one anomalous experimental result to cause me to seriously question it.  In addition, there are some real, solid reasons to be skeptical of these results, as they do not appear to be consistent with other observations.  Specifically, these results do not seem to be in line with observations we have made of supernova explosions.

Recall that I mentioned above that most neutrinos are generated within stars during nuclear fusion.  Well, when a particularly massive star “dies”, it basically blows up in an explosion we call a supernova.  These explosions are very powerful, and they give off a huge amount of energy in the form of light; but they also give off a huge amount of neutrinos as well.  And, as far as we know, these neutrinos are supposed to travel at the speed of light.  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.  These observations of Supernova 1987A are completely at odds with the apparent results of the CERN-OPERA experiments, and until there is a really solid reconciliation of these two sets of data, I am inclined to call the FTL result a fluke.

Supernova 1987A: Image courtesy of the Chandra X-Ray Observatory

**Note: For a more detailed analysis of this issue of the Supernova 1987A data, I highly suggest reading this entry at A User’s Guide to the Universe as well as the latest article over at the Bad Astronomy blog.

Now don’t get me wrong… I am not willing to completely shut the door on the CERN-OPERA results just yet.  This could (note the emphasis on “could”) end up being a truly revolutionary moment in the history of physics, but in order to establish that the FTL result is real we need to do a lot of confirmation.  This means checking and rechecking every possible aspect of the experiment and calculations done by the research group, and then attempts to replicate the results of the experiment at other institutions.  I am happy to say that there are already lots of physics research groups (some just down the road from me at FermiLab) who are lining up to try reproducing these FTL results.  It has been stated by some physicists that perhaps there is some previously unknown physical process involved with neutrino oscillation which could explain these anomalous results, so this is also an area which researchers want to look.

And there’s where things could get really interesting, and where I might start to jump up and down as giddy as a school-girl.  If it ends up that these FTL results are the real deal, then I for one would be extremely excited!  Just imagine what that could mean for the future of science… wow.

So, while I am (like much of the physics community) very skeptical of the faster-than-light claims and think that option #1 is most likely, I would be happy to be proven wrong and go with option #2.  But before that happens, we have to go through the really hard, pain-staking, and arduous process called science.  While we might want FTL to be a reality, it still remains to be seen whether or not it is the real thing.  Remember, wanting something doesn’t make it true.

So, for now let’s just stay tuned and see what happens…