208 replies to this topic

[toastywombel]

This just came out so there is not a lot of clarity on it:

"GENEVA (AP) -- Scientists at the world's largest physics lab say they have clocked subatomic particles traveling faster than light, a feat that - if true - would break a fundamental pillar of science."



http://hosted.ap.org...EMPLATE=DEFAULT

[swansont]

The scientists aren't claiming to have toppled relativity and are calling for independent confirmation. Just as one would expect of responsible physicists.

[Schrödinger's hat]

Is there actually anything in relativity that says no tachyons? I mean you cannot cross the speed of light, and it would probably break a lot of other physics, not to mention causality. But I've never seen anything within relativity, other than common sense (and to be honest, when has that been useful in physics recently?) that says things can't follow space-like geodesics.

[swansont]

Is there actually anything in relativity that says no tachyons? I mean you cannot cross the speed of light, and it would probably break a lot of other physics, not to mention causality. But I've never seen anything within relativity, other than common sense (and to be honest, when has that been useful in physics recently?) that says things can't follow space-like geodesics.

No. But tachyons would need an imaginary mass to follow relativity, and the question becomes what does it mean to have an imaginary mass?

[toastywombel]

Is there actually anything in relativity that says no tachyons? I mean you cannot cross the speed of light, and it would probably break a lot of other physics, not to mention causality. But I've never seen anything within relativity, other than common sense (and to be honest, when has that been useful in physics recently?) that says things can't follow space-like geodesics.

This is not a tachyon, this is a neutrino. For years scientists have tested and assumed that neutrinos travel at the speed of light.

In the early 1980s, first measurements of neutrino speed were done using pulsed pion beams (produced by pulsed proton beams hitting a target). The pions decayed producing neutrinos, and the neutrino interactions observed within a time window in a detector at a distance were consistent with the speed of light. This measurement has been repeated using the MINOS detectors, which found the speed of 3 GeV neutrinos to be 1.000051(29) c. While the central value is higher than the speed of light, the uncertainty is great enough that it is very likely that the true velocity is not greater than the speed of light. This measurement set an upper bound on the mass of the muon neutrino of 50 MeV at 99% confidence.[27]

http://en.wikipedia..../Neutrino#Speed

This time when the same experiment essentially was done
The experiments are actually quite different

CERN says a neutrino beam fired from a particle accelerator near Geneva to a lab 454 miles (730 kilometres) away in Italy travelled 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.

Edited by toastywombel, 22 September 2011 - 08:22 PM.

[Schrödinger's hat]

@toastywombel Tachyon is just a name for something travelling faster than light. So these (if it's not a mistake) would be netrinos that are also tachyons, or objects identical to neutrinos other than that they are tachyons.

No. But tachyons would need an imaginary mass to follow relativity, and the question becomes what does it mean to have an imaginary mass?

Hmm, good point. The only thing I can think of is that it would mean the object would have a different time-like dimension, but then again that's a bit like saying, "At least 90% of tautologies are tautilogical."

[toastywombel]

@toastywombel Tachyon is just a name for something travelling faster than light. So these (if it's not a mistake) would be netrinos that are also tachyons, or objects identical to neutrinos other than that they are tachyons.

You are talking about this....

A tachyon is a hypothetical subatomic particle that moves faster than light. In the language of special relativity, a tachyon would be a particle with space-like four-momentum and imaginary proper time. A tachyon would be constrained to the space-like portion of the energy-momentum graph. Therefore, it cannot slow down to subluminal speeds.

http://en.wikipedia.org/wiki/Tachyon

The stated discovery is more about this. . .

Neutrinos are similar to the more familiar electron, with one crucial difference: neutrinos do not carry electric charge. Because neutrinos are electrically neutral, they are not affected by the electromagnetic forces which act on electrons. Neutrinos are affected only by the weak sub-atomic force of much shorter range than electromagnetism, and are therefore able to pass through great distances within matter without being affected by it. Neutrinos also interact gravitationally with other particles.

There is a difference, two being that neutrinos can gravitationally interact and have a nonzero mass. I think the below segment might sum up what we are seeing from CERN.

Even though supernova observations indicate that neutrinos propagate at the speed of light, it is not clear whether this result holds at higher energies. In particular, in the context of the Standard-Model Extension,[28][29][30] a realistic effective theory that includes Lorentz invariance violations, neutrinos experience Lorentz-violating oscillations and can travel faster than light at high energies.

http://en.wikipedia..../Neutrino#Speed

http://www.wired.com...ter-than-light/

This is another good article on the subject. . .

Jung, who is spokesperson for a similar experiment in Japan called T2K, says the tricky part is accurately measuring the time between when the neutrinos are born by slamming a burst of protons into a solid target and when they actually reach the detector. That timing relies on the global positioning system, and the GPS measurements can have uncertainties of tens of nanoseconds. “I would be very interested in how they got a 10-nanosecond uncertainty, because from the systematics of GPS and the electronics, I think that’s a very hard number to get.”

[pantheory]

This is the most interesting science proposal that I've seen in quite a while. Here's another link to the same story. http://www.wired.com...ster-than-light

Hypothetical particles called tachyons go faster than light. According to the hypothesis tachyons can do so because they are created at light speed and do not have to accelerate past the speed of light -- not that I believe in such things.

I have an idea how GR fans might get out of this one if the observations and interpretations are valid. Einstein's equations don't say that nothing can go faster than the speed of light, what they say is that matter cannot go faster than the speed of light, although some say that if neutrinos are mass-less, that according to Einstein's equations, they must go exactly at the speed of light.

All matter in Einstein's time was known to have mass. Neutrinos were theorized in the 30's but were not observed until 1955, the year of Einstein's death. It was then proposed that neutrinos had no mass. More recently the consensus is the neutrinos might have a little mass. If neutrinos are mass-less particles then seemingly they might be able to go faster than light while remaining consistent with GR, or NOT

Edited by pantheory, 22 September 2011 - 10:20 PM.

[Pincho Paxton]

They measured the speed. Tick tock. Think about the clock.

Edited by Pincho Paxton, 22 September 2011 - 09:25 PM.

[TonyMcC]

"Things" moving at the speed of light are quite common. However these "things" are not really things at all. The ones I am familiar with are moving patterns that carry no energy. The main one I am familiar with is known as the phase velocity in a wave guide. I am wondering if these tachyons have zero mass and cannot convey information or energy from one place to another - in other words they are nothing more than patterns. I am well out of my comfort zone so this is just a thought that passed through my mind. The attachment is copied from the link:- http://www.microwave...veguidemath.cfm

Attached Thumbnails

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Edited by TonyMcC, 22 September 2011 - 09:57 PM.

[Cap'n Refsmmat]

"Things" moving at the speed of light are quite common. However these "things" are not really things at all. The ones I am familiar with are moving patterns that carry no energy. The main one I am familiar with is known as the phase velocity in a wave guide. I am wondering if these tachyons have zero mass and cannot convey information or energy from one place to another - in other words they are nothing more than patterns. I am well out of my comfort zone so this is just a thought that passed through my mind. The attachment is copied from the link:- http://www.microwave...veguidemath.cfm

If you can detect them sooner than a light pulse, then they're transmitting the information faster than light. You could use Morse code, for example, and the pulses would reach the detector faster than light would.

[JohnB]

If confirmed this would be an amazing discovery.

Aside from general "It would upset relativity" may I request one of our physics expert put together a piece outlining the possible implications?

I'm sure those of us without the relevent knowledge would be intensely interested.

[Hendrix]

Anyone know if there was a detection of change in mass?

[dragonstar57]

isn't this old news? i was about to post this same article in a thread called "a fail so epic..."

[Enthalpy]

The general press reports this story, but I've found no science paper about it.
I went to the website of the experiment, there is absolutely NOTHING there about said overspeed.
Sorry folks, this is a hoax, relayed by newspapers which don't even make quick checks before publishing.

[Schrödinger's hat]

The general press reports this story, but I've found no science paper about it.
I went to the website of the experiment, there is absolutely NOTHING there about said overspeed.
Sorry folks, this is a hoax, relayed by newspapers which don't even make quick checks before publishing.

There's this on arxiv http://arxiv.org/abs/1109.4897
I don't expect they published anything, as the vibe I've gotten from the news stories is "we've made a mistake, help us find it".

[alpha2cen]

Theoretically I have thought about this before.
How about seeing this site?

#11 http://www.sciencefo...ed-is-constant/

[pantheory]

There's this on arxiv http://arxiv.org/abs/1109.4897
I don't expect they published anything, as the vibe I've gotten from the news stories is "we've made a mistake, help us find it".

This archive article was just put on today the 22nd. If I were them I'd publish their findings giving all the details of the experiment so that they won't be inundated by inquiries concerning as much of the details of the experiment as possible.

[Schrödinger's hat]

This archive article was just put on today the 22nd. If I were them I'd publish their findings giving all the details of the experiment so that they won't be inundated by inquiries concerning as much of the details of the experiment as possible.

Anyone who would be able to do anything useful with that information will know to look on arxiv, or ask someone who would know where to look for the article.

[Adam Penny]

This archive article was just put on today the 22nd. If I were them I'd publish their findings giving all the details of the experiment so that they won't be inundated by inquiries concerning as much of the details of the experiment as possible.

I'd imagine Michelson-Morley were giving out the same vibe way back when.

lamda is only infinite at the speed of light. If v>c you're into complex numbers. Somebody mentioned complex masses, but maybe complex velocities are plausible as far as the maths is concerned.

One thing to consider here is that they believe they are observing particles getting from one place to another in a time that requires a velocity greater than the speed of light - they're not observing a particle actually travelling at a speed greater than the speed of light. This could be a phenomenon similar to electrons tunneling through a potential energy barrier: We know they can do it, but it's impossible to observe them in the process.