Speed-of-light results under scrutiny at Cern

Opera detector Enormous underground detectors are needed to catch neutrinos, that are so elusive as to be dubbed "ghost particles"

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A meeting at Cern, the world's largest physics lab, has addressed results that suggest subatomic particles have gone faster than the speed of light.

The team has published its work so other scientists can determine if the approach contains any mistakes.

If it does not, one of the pillars of modern science may come tumbling down.

Antonio Ereditato added "words of caution" to his Cern presentation because of the "potentially great impact on physics" of the result.

The speed of light is widely held to be the Universe's ultimate speed limit, and much of modern physics - as laid out in part by Albert Einstein in his theory of special relativity - depends on the idea that nothing can exceed it.

Start Quote

We want to be helped by the community in understanding our crazy result - because it is crazy”

End Quote Antonio Ereditato Opera collaboration

Thousands of experiments have been undertaken to measure it ever more precisely, and no result has ever spotted a particle breaking the limit.

"We tried to find all possible explanations for this," the report's author Antonio Ereditato of the Opera collaboration told BBC News on Thursday evening.

"We wanted to find a mistake - trivial mistakes, more complicated mistakes, or nasty effects - and we didn't.

"When you don't find anything, then you say 'well, now I'm forced to go out and ask the community to scrutinise this'."

Friday's meeting was designed to begin this process, with hopes that other scientists will find inconsistencies in the measurements and, hopefully, repeat the experiment elsewhere.

"Despite the large [statistical] significance of this measurement that you have seen and the stability of the analysis, since it has a potentially great impact on physics, this motivates the continuation of our studies in order to find still-unknown systematic effects," Dr Ereditato told the meeting.

"We look forward to independent measurement from other experiments."

Graphic of the Opera experiment

Neutrinos come in a number of types, and have recently been seen to switch spontaneously from one type to another.

The Cern team prepares a beam of just one type, muon neutrinos, and sends them through the Earth to an underground laboratory at Gran Sasso in Italy to see how many show up as a different type, tau neutrinos.

In the course of doing the experiments, the researchers noticed that the particles showed up 60 billionths of a second earlier than they would have done if they had travelled at the speed of light.

This is a tiny fractional change - just 20 parts in a million - but one that occurs consistently.

The team measured the travel times of neutrino bunches some 16,000 times, and have reached a level of statistical significance that in scientific circles would count as a formal discovery.

But the group understands that what are known as "systematic errors" could easily make an erroneous result look like a breaking of the ultimate speed limit.

That has motivated them to publish their measurements.

"My dream would be that another, independent experiment finds the same thing - then I would be relieved," Dr Ereditato told BBC News.

But for now, he explained, "we are not claiming things, we want just to be helped by the community in understanding our crazy result - because it is crazy".


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  • rate this

    Comment number 185.

    Jason Palmer needs to get his facts right. Einstein said that a body starting from rest can never exceed the speed of light. It has been observed for decades that nuclear processes can produce particles moving at velocities greater than the speed of light. They then emit energy as blue Cerenkov radiation as they slow down to the speed of light.The speed of light is a LIMIT for either way.

  • rate this

    Comment number 184.

    Also, for the sake of not infuriating the David Griffiths of the worlds, for anyone who happens to read this and need some clearing up, "energy" is a property of particles. Think of it like "green", it cannot exist on its own, it is a property of something else. There is no "pure energy", and when annihilation happens, you get light, photons, particles with energy, just no mass. Like gluons.

  • rate this

    Comment number 183.

    A non scientific idea.

    To measure something travielling at the speed of light, the measuring eqipment must work exactly at or above that speed.

    Problem solved I think, the equipment isn't fast enough.

  • rate this

    Comment number 182.

    This is the problem with using Google maps for distances! Remember, neutrinos go as the crow flies.

  • rate this

    Comment number 181.

    When the speed of the neutrinos was compared to the speed of light, was it the MAX speed of light as in an empty space, or was it the dilated speed of light on earth under the effects of earth's gravity field...?

    Otherwise we are already familiar with this effect from nuclear reactor blue-light....

  • rate this

    Comment number 180.

    Also without science we would still think the earth was flat and the earth was the centre of the universe. So to those who think science is a con of some sort then please continue to live in ignorant bliss about your surroundings and continue to ignore science.

  • rate this

    Comment number 179.

    "Speed in relation to what? Is the speed of light supposed to be absolute or relative to its immediate surroundings?"

    It's absolute. That's the whole point. No matter how you are moving, you will always measure light as travelling at the same speed (just under 300,000 kilometres per second). And it's also an absolute upper limit, as far as we know.

  • rate this

    Comment number 178.

    thanks Oli, thats just the kind of positive stuff we need, why not put up a link where us mere mortals can discuss this very interesting bit of news
    137. Oliver9523 7 Minutes ago

    Would people please stop commenting if you do not have a degree in physics. You have no idea what you are talking about.

  • rate this

    Comment number 177.

    I saw one this morning; whizzed by my water bill as I read that by the window light. Thing is, it didn't help find the money I need.

  • rate this

    Comment number 176.

    Two things. Lamda = 1/root(1-v^2/c^2). That's only at infinity when v=c. If v>c then you're into complex numbers, not infinity.

    The other thing is, they're observing a particle getting from one place to another that would require it to be going at a velocity faster than the speed of light, they're not observing it travelling faster than the speed of light. Possibly similar to quantum tunneling.

  • rate this

    Comment number 175.

    I read somewhere that when Einstein considered his theory, he calculated that exceeding light speed was possible, but that in order not to be labelled a crackpot he changed it to suit current thinking.
    If true, then the price of free thinking has cost us a century of progress, and Spock will have to wait a little longer..

  • rate this

    Comment number 174.

    I'm more inclined to think that this is an example of light being delayed than particles exceeding the speed of light (in a vacuum).

    As has been established previously many things influence the actual speed of light, not least temperature, gravity etc. The margin here is so slight that it is most likely a statistical error rather than a 'discovery'.

  • rate this

    Comment number 173.

    It's vital to maintain healthy amounts of skepticism when looking at results which would overturn modern physics. Don't forget about the "anomaly" which appeared in Tevatron results at Fermilab that eventually turned out to be nothing at all. It's much more likely the experiment has a flaw, and the physics community will find it, than relativity has been overturned.

  • rate this

    Comment number 172.

    Perhaps there is a simple explanation for this. On my back-of-the-envelope calculations, "a few billions of a second" is equivalent to a distance of about 10 centimeters at he speed of light.

    The experiment distance is 720km. If the distance is 10cm too short, the particles apparently arrive a few billions early - Simples

  • rate this

    Comment number 171.

    DDes Currie, yes, you're missing quite a bit. The speed of light is only thought constant because of "Maxwell's Equations". Originally we believed they only described light moving though a medium, called the ether, but this didn't fit with observation, like Michelson-Morley's. E=mc^2 just came about when Einstein said "ok, if the eather isn't what would our physics look like?"

  • rate this

    Comment number 170.

    Maybe the calculation of the speed of light is incorrect and it slightly higher than are current measurement techniques suggest. Therefore neutrinos are travelling at the true speed of light.

  • rate this

    Comment number 169.

    It's clear (reading some comments here) that the average scientist must be of a lower order of human, being that they are so unsure of their findings and have to ask for reviews

    That being opposed by the intuitively correct, self assured and superior intellect ot the average HYS poster who doesn't need any degree of understanding, of any subject, in order to make a comment

    Ignorance is bliss

  • rate this

    Comment number 168.

    Light is energy. Thought is energy. Neutrinos respond to thought. Perhaps the speed of thought......

  • rate this

    Comment number 167.

    To the people who are giving ideas as to where the scientists might have gone wrong with there calculations. The concepts you are describing are pretty simple and I think anyone who didn't think of such things when calculating the neutrinos speed could not call themselves a scientist, feel assured that they have included these factors into their calculations.

  • rate this

    Comment number 166.

    Neutrinos come in several types - muon, tau, etc etc ............. and the type - Clegg. The Clegg neutrino is the hardest one to understand and account for. Easy to predict but very hard to hold to its stated properties.


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