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Faster than the speed of light?

At just over 186,000m/s, the speed of light (the 'C' in Einstein's E=MC plays a fundamental role in nearly every aspect of physics. It's also been a useful device for many a B movie and sci fi novel. Since HG Wells published The Time Machine in 1895, the idea of exceeding the speed of light and entering the realms of time travel, has been one that has consistently captured the public imagination.

Revered astrophysicists Carl Sagan and Stephen Hawking further piqued the public's fascination with talk of worm holes. And while Sagan remained reserved on the possibility of time travel, significantly he added that he believed it was still worth exploring.

Astrophysicists concede that until the speed of light can be exceeded, time travel will remain an impossibility. But in September 2011 researchers working on the Opera experiment at CERN, Geneva, made an announcement that has the potential to turn the very foundation of physics on its head.

For a period of months, teams at CERN and the underground Gran Sasso Laboratory of the Italian National Institute of Nuclear Physics had been observing more than 15,000 sub atomic particles called neutrinos. Neutrinos are produced by the decay of other particles such as neutrons in a radioactive nucleus.

The main aim of the research was to observe neutrino oscillations - whereby the particles change 'flavour' as they travel. By measuring the oscillations, the masses of the neutrinos could then be determined. The researchers believed that an accurate measurement would give new insight into fundamental particle physics questions about how the mass of neutrinos and other particles arises.

When the readings came back, the researchers discovered something astonishing. Results repeatedly indicated that the neutrinos had travelled at a velocity 20 parts per million faster than the speed of light. If these unexpected findings were proved to be correct, the implications could affect all aspects of cosmology, astrophysics and particle physics.

The results were made public and the worldwide media immediately hypothesised potential applications for particles that could travel faster than light. Meanwhile, physicists across the globe demanded proof. Indeed, the Opera project leaders actively encouraged scrutiny from the broader particle physics community in a bid to fully assess the nature of the observation. The authors of the OPERA paper said: "We are not claiming things, we want just to be helped by the community in understanding our crazy result - because it is crazy." Within two weeks nearly 30 physicists had already published papers claiming faults with the findings.

One such sceptic is Stephen Fairhurst, Royal Society University Research Fellow School of Physics & Astronomy Cardiff. "There is every chance that there is a less spectacular explanation of the results, and several papers offering alternatives have already been written," he said. "For example, one paper discusses the technical challenges of synchronising clocks to the required accuracy to make these measurements. Nevertheless, the discovery of faster than light travel would be truly remarkable."

Neutrinos, invisible particles that rarely interact with matter, are the hardest of the sub atomic particles to study. Dario Auterio, Researcher at the Institut de Physique Nucleaire de Lyon, notes that such properties make tracking and detection extremely difficult.
"Neutrinos do not have an electric charge and they interact very weakly with matter – so called 'weak interactions'. They are capable of passing the entire earth without interacting."

And, while there are plenty of neutrinos available to research – approximately 400,000billion from the sun pass through the earth every second – until recently, it was not even known whether the particles have a very small mass, or no mass at all. If neutrinos do have a mass then they have the potential to make up part of 'dark matter' and, in theory, the universe could have sufficient gravity to stop expanding and start contracting.

"Neutrinos have many interesting features in particle physics," continued Auterio. "At the beginning, we talked of neutrinos not having a mass. But, with the infiltration of the flux of neutrinos coming from the sun, people have been starting to think that they could have a mass and could change their nature during their travel path. They can transform themselves into three different types of neutrinos: electron neutrinos, muon neutrinos and tau neutrinos. The neutrinos are also linked to many aspects of cosmology, to the birth of the universe, they may be related to the symmetry between matter and anti matter and they're also the most common particles in the universe."

To effectively track and detect the particles, the Opera Project researchers adopted a unique approach.

High energy beam pointed towards Italy
The Opera experiment was established in 2006 to analyse neutrino oscillations and to detect the appearance of tau neutrinos from the oscillation of muon neutrinos. A high energy beam of muon neutrinos was pointed from the Geneva based CERN accelerator complex (CNGS) towards Gran Sasso, 730km away. A beam of this kind is generated from collisions of accelerated protons with a graphite target, after focusing the particles produced in the desired direction. As products of the same 'parent' particle, muons and neutrinos continue to travel in the same direction. And because neutrinos rarely interact with matter, the particles were able to pass undisturbed, taking just 3ms to reach their destination.

Auterio observed: "The interesting aspect of this measurement was the combination of techniques used in energy physics for neutrino detection. The high energy beam, which is sent to Gran Sasso, has a unique property to provide a very high rate of neutrino interactions that we can detect in our Opera detector. This is related to the fact that it is a high energy neutrino beam.

"The other very interesting aspect was combining this with metrology techniques related to the measurement of space and time. These are commonly used in other fields but have never before been used in particle physics with this level of accuracy."

The resulting interactions (tau leptons) were observed in 'bricks' of photographic emulsion films interleaved with lead plates – each one, effectively working as a photographic camera. Construction for the Opera experiment began in 2003 and it took five years to complete the apparatus which contains 150,000 of the bricks arranged into parallel walls, interspersed with plastic scintillator counters. A series of electronic detectors such as trackers and spectrometers were used to monitor the path of the neutrinos.

To monitor the momentum and charge identification of penetrating particles, a magnetic spectrometer was used to track each target. As data was being taken, it was possible to tag neutrino interactions in real time and provide information on the exact location of the neutrinos on the bricks. Once these had been extracted from the wall, developed and scanned for evidence of tau decays, the researchers could detect all details of the neutrino events by measuring the elementary particles produced in the interaction of the neutrino with the brick.

The Opera team discovered several particles that had left tracks in the brick at the point of interaction. According to the researchers, this indicated a tau neutrino interaction with a probability of about 98%.
CERN's high energy accelerators and detectors were constructed specifically to analyse the foundations of the structure of matter.

"We were very surprised because we conducted the analysis in a blind way," Auterio explained. "We were expecting negative results so were surprised to detect this anticipation of neutrinos with respect to what could be computed, assuming the light on the same travel path. The factor at which we measure it is equivalent to 60ns over a time of flight of 2.4ms – or if you want to express it in terms of distance, an anticipation of 20m over 730km."

If the findings turn out to be correct, the research will have a spectacular impact on Einstein's theory of general relativity. "If particles can travel faster than the speed of light, this would force a major re-write of modern physics," said Fairhurst. "Einstein's special relativity does not permit faster than light travel. So, if it is observed, this would require a reformulation of relativity and every theory that is built upon it. At present, there is probably no theory that is capable of allowing faster than light travel and explaining everything else we have observed in the universe, from quantum physics on the smallest scales to astrophysics and cosmology on the largest."

Time travel in the offing?
So are we on the verge of witnessing the beginnings of time travel? If the Opera project data is proved to be correct, then it raises the question of whether materials can also be manipulated to exceed the speed of light. Fairhurst remains cautious. "One thing to point out is that it is very difficult to accelerate things close to the speed of light - it requires large experiments like CERN," he said. "In Einstein's relativity, to accelerate a particle to close to the speed of light requires a huge amount of energy. And the amount of energy required increases as you get closer to the speed of light so that it would actually require an infinite amount of energy to get to light speed."

It may be a matter of weeks before it is established whether neutrinos can travel faster than light, but for now manipulation of time itself must remain the stuff of fiction.

Chris Shaw

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What you think about this article:

It was never clear to me conceptually how time travel could be achieved by FTL speed. I am hoping they find a problem with their experiement, but my feeling is the odds are, they have really found something amazing, and there have been other clues pointing to this as well (e.g. SN1987A supernova).

Posted by: beagle, 30/10/2011
As well as adjusting timing into pulses, can they play with beam density / intensity; or at least ensure it is the same. Who knows whatever they may find?

Maybe space only allows so much fast stuff at a time. A sort of NO-ETHER.

Universe borrowed from somewhere (else?). In this way, the Big Bang is more like a big tap. Except the limited stuff queued up is virtually banged / projected, and will sort itself out when there is enough space to precipitate out.

When my local motorway is clear, I bomb along at 70mph(+/-10% reading error).
When it is busy, maybe 50mph. Busier 20mph. Jam 0 mph. Police cars on the hard shoulder (other dimensions, get their own fast lane). Somehow ambulances make it through the mass in the middle. What is in my way affects my speed.

If I was a little (wave/) particle towards the speed of light, it might be busy, and there's not much space for me. Maybe spaces appear, and quantumly I fill them or miss them. My speed becomes blurred. Maybe my space gets squashed. Maybe the speed of holes is not limited like "light". I am forced forward (faster than light) or backwards (slower than light) to a free one. Inbetween I might only exist virtually, and with no mass I can leap faster than light.

Posted by: Neil Humphrey, 28/10/2011
Time travel wouldnt be possible unless something travelled at <0m/s right? so even if it is faster than the speed of light, it would still be in positive figures. I could be totally wrong, I'm not a physicist...

Posted by: Amsterdam, 26/10/2011
Hi Chris,

I am a social scientist and not a physicist - this fact is prevented my voice from getting heard on this topic. Will you listen?

The following statement appeared in Scientific American after the story about Faster Than Light Neutrinos:

Theoretical physicist Lawrence Krauss of Arizona State University-

"It is an embarrassment as far as I am concerned. It was not unreasonable for the experimentalists to submit a paper with an unexplained result. But a press conference on a result, which is extremely unlikely to be correct, before the paper has been refereed, is very unfortunate—for CERN and for science. Once it is shown to be wrong, everyone loses credibility. Neutrino experiments are hard, and systematic errors at the limit of resolution can be significant. Moreover, because the experiment appears to violate Lorentz invariance, which is at the heart of so much known physics, one should be skeptical. One should be additionally skeptical because observations of SN 1987A showed, as I wrote in 1998, that neutrinos and photons travel at the same speed to one part in a billion, several orders of magnitude below the claimed effect. *Now, the only way out of that is to have some energy-dependent effect, but all the ones that make sense don't wash here.*"

I know of one energy-dependent effect that DOES WASH. I have developed a hypothesis which accounts for that unknown 'energy-dependent effect'
during the CERN/OPERA experiment. Unfortunately, I my knowledge is being blocked out because I am not a physicist. Sometimes it is the non-expert who has the ability to see the big picture because the non-expert has a wider view of the topic. I was involved in unrelated research when this story came out and it just happened to connect directly to this event.

Bobby wondering ...

Posted by: Bobby, 26/10/2011
Einsteins theory is E=MC² not E=MC2, or equivalent to E=2(MC). If you are trying to notate this by not using superscripted numbers (ALT+0178 on your keyboard) then it is to be represented as E=MC^2, where the ^ denotes 'raised to the power of'. Just an little FYI for your consideration as you blog into the future.

Posted by: Kent, 25/10/2011
I don’t believe any particle made of matter can travel faster than the speed of light. The reason light travels so fast is that its mass approaches zero. Now if something was made of anti matter then it is a clear possibility that such anti matter particle could travel faster than light. The problem is finding such anti matter particles.


Posted by: km, 25/10/2011

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