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Speed-of-light experiments yield baffling result at LHC

bbc.co.uk

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Re: Speed-of-light experiments yield baffling result at LHC

#61

Post by orangecat »

ajuc wrote: post #32
dholowiski wrote: post #15

Earlier quoted context omitted.

I'm not smart enough to explain it properly, but basically if information can be transmitted faster than the speed of light, it makes time travel possible. Read "Black Holes and Time Warps" By Kip S. Thorne for a 624 page explanation of why. More likely, it's experimental error. .0025% is meaningless compared to the scale of the earth, but over hundreds of light years it's huge.

http://en.wikipedia.org/wiki/Time_travel#Via_faster-than-lig... If we can send information even a little to the past, we can then send it a little more to the past, and by induction we can send information anywhere in time. So we have infinite power computers. Singularity starts here.

DO NOT MESS WITH TIME

(http://www.fanfiction.net/s/5782108/17/Harry_Potter_and_the_...)

Re: Speed-of-light experiments yield baffling result at LHC

#62

Post by bestes »

lutorm wrote: post #43
DanielBMarkham wrote: post #3

A news article where both the scientists and the reporter understate the claims, publish the data, and ask other teams to please prove them wrong. I like this. Most of the time the reporters overstate the research, the scientists keep the data secret, and the general public is left scratching their heads.

Most of the time ... the scientists keep the data secret Um, no. There are plenty of data being released, and in even more cases the scientists are happy to give you the data if you ask. It's very dependent on discipline, though. In astronomy, pretty much all data obtained with publicly funded facilities (e.g. including all large space instruments) are accessible by anyone after a proprietary period of 1 year.

Maybe not secret then, but to be released at a later date. Or released in one of those journals that most of cannot access.

Re: Speed-of-light experiments yield baffling result at LHC

#63

Post by nickolai »

foob wrote: post #50

If this result is valid then it would mean that neutrinos are capable of traveling .0025% faster than light. There was a supernova that we observed in 1987 (SN 1987) that occurred 168,000 light years away from us. A neutrino burst was observed in 3 different labs about 3 hours before the light was observed. If neutrinos are capable of traveling .0025% faster than the speed of light then why would we observe these neu…

Um... is there any trace of neutrino bursts before that? Im not sure anyone bothered checking, since such a correlation would have been very hard to justify. A neutrino burst 4 years before a supernova... so what?

Could a physicist clarify whether neutrinos could travel at different speeds in vacuum like any 'normal' particle, or are 'fixed speed' like photons. We could well have had several waves with the bulk arriving at c-epsilon and no one bothering to check outside the expected time frame.

Re: Speed-of-light experiments yield baffling result at LHC

#65

Post by Permit »

Confusion wrote: post #34
jxcole wrote: post #19

Earlier quoted context omitted.

That is such a well known result in physics that the likelihood of it occurring here is almost zero. I remember first reading about it and the scientists basically said "we broke the speed of light" without looking for further explanations. These guys seem like they generally don't believe that they have broken the light barrier, but they need help figuring out what they actually did do from the broader community. Du…

What DenisM is describing is not the result of a systemic error. It is not an error at all. 'Something' is travelling faster than light in that experiment. The problem is that the 'something' isn't a physical object. The common example is the beam of a lighthouse. Suppose a lighthouse revolves once per minute. At one lightyear distance from the lighthouse, the angular velocity of the beam is 2*Pi lightyears per minut…

Perhaps I misinterpreted, but I think DenisM was talking about something completely different. He mentioned that because of a lack of density in the leading photons, the first piece of equipment missed the measurements while the second one picked it up. That would a problem with the system they're measuring with, not at all to do with treating light as a single entity.

Re: Speed-of-light experiments yield baffling result at LHC

#66

Post by dholowiski »

felipemnoa wrote: post #29
dholowiski wrote: post #16

Earlier quoted context omitted.

Don't forget... c is the speed of light 'in a vacuum'. Light travels slower through gas, water or glass. Light has even been slowed down to walking speed in a laboratory. The speed of light is not constant. The speed of light in a vacuum is. We assume.

>>The speed of light is not constant I think this is wrong. Regardless of the medium the speed of light is always constant. It seems to slow down because the photons are getting absorbed and re-transmited by atoms. But the speed of light is always the same regardless.

After much research... the concept is correct, although 'absorbed' and 'retransmitted' are not the right words to use. http://en.wikipedia.org/wiki/Slow_light

"Light traveling within a medium is no longer a disturbance solely of the electromagnetic field, but rather a disturbance of the field and the positions and velocities of the charged particles (electrons) within the material. The motion of the electrons is determined by the field (due to the Lorentz force) but the field is determined by the positions and velocities of the electrons (due to Gauss' law and Ampere's law). The behavior of a disturbance of this combined electromagnetic-charge density field (i.e. light) is still determined by Maxwell's equations, but the solutions are complicated due to the intimate link between the medium and the field. Understanding the behavior of light in a material is simplified by limiting the types of disturbances studied to sinusoidal functions of time. For these types of disturbances Maxwell's equations transform into algebraic equations and are easily solved. These special disturbances propagate through a material at a speed slower than c called the phase velocity."

As another commented pointed out, you're splitting hairs. The "speed" of light and how fast it is "moving" depends on how you define those terms. The second paragraph of the wikipedia speed of light article has it right "The speed at which light propagates through transparent materials" - which does change.

Re: Speed-of-light experiments yield baffling result at LHC

#67

Post by baddox »

DenisM wrote: post #12

There was an experiment where an impulse of light came out the other end of a material faster than light could have traveled through vacuum in the same space. The eventual explanation was as follows - imagine that your outgoing bunch of photons looks like this: :::... The first three photons are "invisible" because there is so few of them that they are below the equipment sensitivity. The second group of six particle…

I'm not familiar with that experiment, but it doesn't sound to me like information traveled faster than the speed of light, which is really the important part of the speed of "light."

Re: Speed-of-light experiments yield baffling result at LHC

#68

Post by sp332 »

sliverstorm wrote: post #59
sp332 wrote: post #36

Earlier quoted context omitted.

How do you think gigabit ethernet works?

I don't have the specs, but 100Mbit operates at 31MHz. Remember, quad-twisted pair. So it is likely 1Gbit operates at ~300MHz. Now, 10Gbit probably does operate with a period less than 1ns. (1 billionth of a second)

Over Cat5e, it uses all 4 pairs and 2 bits per symbol, so it's only 125M symbols per second (per pair). I was thinking of fiber, which I think also uses 2 bits per symbol so it would need 500M symbols per second.

Re: Speed-of-light experiments yield baffling result at LHC

#69

Post by lutorm »

bestes wrote: post #62
lutorm wrote: post #43

Earlier quoted context omitted.

Most of the time ... the scientists keep the data secret Um, no. There are plenty of data being released, and in even more cases the scientists are happy to give you the data if you ask. It's very dependent on discipline, though. In astronomy, pretty much all data obtained with publicly funded facilities (e.g. including all large space instruments) are accessible by anyone after a proprietary period of 1 year.

Maybe not secret then, but to be released at a later date. Or released in one of those journals that most of cannot access.

No one releases data in journals, at least not in astronomy. There are dedicated sites for this, e.g. http://archive.stsci.edu/

About the later date: I think it's reasonable that those that put together the proposal and thought up the project have a chance at getting their results out first. Otherwise, why would you go through the effort of planning and executing observations if you could just poach someone else's data as it comes down the pipe? Think of it as a 1-year patent on the research project.

Re: Speed-of-light experiments yield baffling result at LHC

#70

Post by nickolai »

Similar results seem to have already been obtained in the past

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

QUOTE

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.

/QUOTE

The value looks awfully like what we have in front of us today, but the uncertainty was too big to investigate further

EDIT : actual paper :http://arxiv.org/abs/0706.0437

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