So CERN has stunned us with a result and this one doesn’t even come from the LHC. The premier European high energy research institute has detected neutrinos that seem to move at a speed greater than that of light, violating one of the most sacred pillars of physics Einstein’s Special Relativity. You must have read about it we posted it here. So what about these faster-than-light neutrinos? Why are so many people all excited about them?
Faster Than Light Neutrinos, Claims CERN: http://techie-buzz.com/science/faster-than-light-cern.html
In this article, I will try and explain that, touching upon four crucial points. First we need to understand why people are not ready to believe the result in the first place. Next, we’ll understand whether this is believable or not. Is CERN just tricking us or have they put real hard work behind this before publishing it? Next, we shall talk about the implications of this result, if it is proved right. Lastly, we discuss how there can still be flaws and where some glitches might be found in the coming days.
Unlike the popular media, scientists are treading softly on this result. They are not yet ready to say that Einstein was wrong, although that is what it would imply. They are merely reporting facts at this moment, stating the results as got in the experiment. The result is very possibly wrong, but let’s take a closer look.
What on earth are Neutrinos?
The real heroes of this story, Neutrinos are the slipperiest of all known particles. They carry no charge, almost no mass and interact extremely feebly with other matter and that too via the weak interaction. They’re nearly impossible to detect. They leave no tracks in bubble chambers (no charge), don’t interact with each other to form clumps (no strong interactions, like those of protons and neutrons) or speak with normal matter particles. Scientists were forced to assume its existence to solve a puzzle (the beta decay problem), and, even though neutrinos have been detected after that by several detectors, their properties remain largely mysterious. They are giving a headache once more.
Why are people not ready to believe it?
Simply put, it’s Einstein. People are not expecting anything new and now they find this! This is just too unexpected. Why take a result so flagrantly conflicting with all known physical results at face value? Wellâ€¦
Is this result Believable?
As an answer the first of our questions, I would go with a Yes‘. The result is totally believable in the sense that the experiment and analysis seem water-tight at this moment. Scientists of the OPERA collaboration have been looking at the data for three years! They have done everything scientifically possible to discredit their own finding, but have only managed to strengthen it.
Remember, we told you in the particle physics articles, what confidence level means? A confidence level, quoted as some n-sigma, n’ being an integer, refers to the amount of confidence the experimenter has on his/her own results. A 3-sigma result is one which is significant enough to be considered a potential for detection’. This means that the doubts are less than 0.3%. We’re just getting warmed up! For a discovery’ we need a minimum of 5-sigma, which is a confidence level of 99.9999%.
The current results are a 6-sigma, at 99.999999% confidence level, high and above the threshold required to get a discovered’ tag!! This still doesn’t mean that it is true. It just means that the possibility that this is merely a statistical fluctuation is extremely small. They two are very close, but not the same.
The real motivation for believing in what CERN has found is the methodology they’ve applied in finding out the results. They had found this result 3 years back, but never jumped the gun in publishing it. They checked and re-checked everything, found crucial error bars and found that this result survives. They added more parameters contributing smaller errors, hoping that they’ll somehow add up and then give the necessary’ error bars. They didn’t.
We’ll just talk about the use of GPS and cesium atomic clocks to measure time and how accurately the distance was measured. Since velocity is simply distance divided by time, we need both parameters accurately.
For keeping time, CERN uses a timing system based on synchronization by four nearest GPS satellites. CERN has something called a common view’ GPS, which synchronizes the clocks at CERN and at OPERA. Furthermore, CERN uses atomic clocks to provide a time-stamp. Since OPERA is sitting at a higher altitude than Gran Sasso (the lab to where the neutrino was beamed), you’ll have to correct for gravitational effects. Clocks run slower in a weak gravitational field than in a stronger one, according to General Relativity (GR). As the gravitational field strengths differ, the clocks lose synchronization. These clocks are regularly re-synchronized using GPS to take into account General Relativity effects.
Accuracy of measurement
They’ve measured a distance of 732 km with an accuracy of 20 cm! They’ve measured time to within 5 ns accuracy. The whole of the apparatus might contribute an error of 7.4 ns to the time of flight, well below the 60 ns discrepancy.
Why am I really going into all these gory details? It’s just to convey the impression that this is not really another crackpot claim you keep hearing about. This is really a well-done experiment. They’ve sincerely worked out all details and tried to plug in as many loopholes as possible. The effect still stays.
One might ask the following questions: what about effects external to the whole apparatus, like tides (which slow down the Earth’s rotation, albeit by a tiny amount) or atmospheric fluctuations (which would change the GPS signal speed through air, introducing an error in the time)? It is in answering these questions that one gets to know how far the CERN scientists went before publishing these results. The experimental analysis was done for 3 whole years, using as many as 16111 events! By the law of statistics, this will reduce the error of any quantity by more than 126! (The error in a quantity is suppressed by the square root of the number of statistical points. Square root of 16111 is just above 126!) Furthermore, tidal effects are periodic and would cancel out over three year periods. The same goes for atmospheric fluctuations.
The scientists even took into account tectonic shifts (graph above). They factored in the effect of the 2009 giant earthquake and tsunami, taking into account the fact that the tectonic plates had shifted by 3 cm! No wonder, Nobel Laureate Sam Ting called the experiment beautifully done’.
What are the implications if this is right?
Scientists are not the jumpy guys, but no one can deny that the implications will be huge! The existence of a speed greater than the speed of light in vacuum immediately contradicts one of the two postulates of Special Relativity (SR). The very structure of SR is based on the constancy of the speed of light to all observers. It doesn’t matter at what speed you’re moving, you’ll always see light move away from you at the velocity of light. (Contrast this with, say, a velocity of a bus!) Furthermore, this is the highest speed achievable. Information, in whatever form, cannot travel faster than this speed. The neutrino result strikes at the very foundations of SR.
So what, you may say? All that we have to bend our mind across is simply the fact that Einstein got it wrong. No, this is much bigger than that! Scientists would’ve had NO problem if they could get away by just saying that Einstein was wrong, but it’s much deeper.
SR teaches us how to do mechanics, how to measure quantities like energy, momentum and even mass. It teaches us what space is and what time is, instructing us never to use those terms separately, but to say space-time’. It tells us how one quantity in one frame might look to another guy moving with some velocity relative to the first frame. It tells us how electric and magnetic fields might look to observers at different speeds and integrates the laws of mechanics with those of electromagnetism.
When SR is integrated with quantum mechanics, it gives a huge body of knowledge called Quantum Field Theory (QFT). QFT is a pinnacle of success of human thought, giving us theories like Quantum Electrodynamics, which are unbelievably accurate. To change SR would be to really shake up the extremely successful construction of physical theories, a process that took place over the last 80 years and more. This involved countless experiments, tremendous toil and, in cases, amazing display of genius! Further, all of it fits together. It will be extremely difficult, if not impossible, to re-create a different edifice explaining all of the phenomena explained just as satisfactorily.
No, this result just cannot be right. They’re making a mistake somewhere, says an inner voice in me. Scientists all around the world might be saying just this.
But how can such a result be wrong?
The best answer to this is that SR is too strong and backed up by too much evidence accumulated over the past century to be proved wrong by one experiment. There needs to be good experiments to back up these results and that will only come in the coming years. A 6-sigma effect is hard to ignore, but scientists have been there, done that and found some error or the other in incidents like this in the past.
The loophole has to lie within the measurement procedure. There is still room for uncertainty in the measurement of the departure times (i.e. measuring when the neutrinos are launched) and in the very working of the GPS systems. Maybe, instead of neutrinos, the fault lies in what we understand about GPS systems and how they work. Yes, this is a mundane explanation compared to the exotic ones flying around, like quantum gravity and shortcut through extra-dimensions, but one which works perfectly. We just need to figure out the flaw! Furthermore, we will need other experiments (like the Super Kamiokande, pic above) to independently find such an effect.
Dear reader, I hope that you’ve not lost the crux of the plot in all the details. Even if you’re not in the least bit associated with physics, feel the beauty of it all. Yes, people are worried that it might turn 100 years of physics on its head, but then scientists are working to resolve it. The OPERA group has declined any interpretation of the results, whether theoretical or phenomenological. Scientists are working to prove their own results wrong. How honest and beautiful that is!
I’m hedging my bets on Einstein at this moment. The Grand Old Man of Physics has had too much of an impact to be dismissed just like that. I’m hoping that this result simply goes away. I can imagine him sitting in heaven, watching over us and nodding his head in slight disapproval with a smug smile on his lips, saying, Check your measurements again, lads. My calculations are fine.Or he might be worried sick. Surely, he’s proud of the work of these scientists, who are a few generations his successor.
Couple of excellent articles on this: