Scientists make startling discovery

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Re: Scientists make startling discovery

Postby theckhd » Fri Sep 23, 2011 1:35 pm

Treck wrote:
theckhd wrote:The neutrinos saw a fractional advancement of ~60 nanoseconds in a total traversal time of 2.4 milliseconds. Without more information, it's impossible to tell whether 60 ns is relevant.

Are you questioning their accuracy in measuring?
They see the same deviation reliably, so i doubt its not accurate.
But it doesnt mean its "right", they are trying to find every possible reason why this could be "wrong", but they havnt found one now, and are maybe considering the possibility that it might be correct.
theckhd wrote:There's nothing special about making a particle appear to travel faster than the speed of light. It happens all the time. The speed of light is only the cosmic speed limit for signal transit, so unless you can prove that those neutrinos carry information, it's meaningless.
If you can send a beam of neutrinos from one place to another, and reliably read them on the other place, how is that not sending information?


No, based on a quick skimming of their paper, I don't doubt their measuring accuracy. 60 nanoseconds is huge anyhow - I'm measuring things in my laboratory to accuracies of < 1 fs, or 10^-15 seconds, 6 orders of magnitude shorter. You could measure a 60-nanosecond delay quite easily with an off-the-shelf LED and an oscilloscope.

But let's put that in perspective. Let's say I have a particle that's 500 nanoseconds "long," with a peak right at the center of that 500-nanosecond window. If I advance the peak by 60 nanoseconds, I could make exactly the same observations they did in their experiment. That's easy to do in the laboratory. But it doesn't break causality, because the peak of a particle's wavefunction carries no information.

The information is carried by discontinuities. In other words, at some point I had to decide to "turn on" my particle. That's where all the information is, provided I do nothing else (i.e. no alternate encoding or modulation of the particle to signify higher bit density). If my particle is my information, then the moment I "turn on" the wavefunction, that information has been sent. It doesn't matter what the rest of the particle looks like - maybe the turn-on is very weak, the particle is 500 ns long, and the peak occurs right in the middle. The information is still in that very first part, where the decision was made.

So I may be able to advance the peak by 60 nanoseconds by some technique, but to "break" causality I'd have to force energy to reach the target before that discontinuous decision point does. And that has never, ever been demonstrated in an experiment, presumably because it can't happen (that would break causality).

In fact, I can link you to a very nice Science paper where they did such an experiment - they took a gaussian pulse profile and put a discontinuity on the peak, so that it either went up or down in intensity at that point. Then they sent the pulse through slow- and fast-light materials, and tried to discriminate the earliest time at which they could distinguish which pulse was sent. Unsurprisingly, even when the pulse as a whole was delayed or advanced heavily, the decision point - the information - always propagated at c.

The key conceit here is that we assume that the peak of the wavefunction is a causal object that carries information, just because it represents the maximum likelyhood of interaction/detection. But that's not the case, it's just a misconception based on a naive interpretation of particles as having a single point of existence.

Treck wrote:Also they do have different states (the reason they ran the experiement in the first place) if they discover what causes their different states, and maybe can control it, then thats another way of sending information aswell.


I think you're talking about neutrino "flavor" changing, which is a different thing altogether, and unrelated to the issue of advancement as far as we know. It's possible that the flavor changing process is related, maybe even it causes the observed advancement, but I'm just not familiar enough with the area to say anything definitive.


Treck wrote:
theckhd wrote:The confusing part, to me, is why the very first thing they thought of wasn't dispersive propagation effects. Maybe particle physicists don't see that very often?

Honestly, i have no clue what that is, but do you really think they havnt considered it?


After looking at the paper, they did mention that they energy-binned their neutrinos and didn't see an appreciable time delay difference for any subset. So they did, in a sense, look at dispersive propagation effects. I'd have to read the paper more carefully to see if they overlooked something, because the terminology they use is a lot different from what we use in Optics.

That said, it's also possible they screwed that analysis up; it doesn't take a significant amount of dispersion to cause weird group delay effects, and the amounts would be small enough that with too fine energy-binning, they wouldn't be detectable. I'll give them the benefit of a doubt though and assume they did it correctly. In which case, my next guess is that we're looking at a tunneling-like phenomenon that's well-understood already; we just don't know exactly what the particles were tunneling through. But 60 nanoseconds is about 60 feet of material, which isn't a lot given the multi-kilometer travel distance of the particles.
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Re: Scientists make startling discovery

Postby Shoju » Fri Sep 23, 2011 1:44 pm

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Re: Scientists make startling discovery

Postby Mukat » Fri Sep 23, 2011 2:00 pm

What I want to know is what is the cosmic meaning or use of a faster-than-light particle. Also does that mean the particle has negative mass, since to move at the speed of light, doesn't the mass of an object increase to infinity under normal circumstances?
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Re: Scientists make startling discovery

Postby theckhd » Fri Sep 23, 2011 2:19 pm

Mukat wrote:What I want to know is what is the cosmic meaning or use of a faster-than-light particle. Also does that mean the particle has negative mass, since to move at the speed of light, doesn't the mass of an object increase to infinity under normal circumstances?


Well, that's just the thing, we don't know. It would require an infinite amount of energy (not mass) to accelerate any massive particle to the speed of light.

I don't think we're ready to give up the idea of causality yet though, so provided a faster-than-light particle was discovered, the first thought would be that c isn't the ultimate speed limit that causality is based on. That said, it would still break a lot of well-established physics.

On the other hand, neutrinos are very weakly-interacting. A completely non-interacting particle could conceivably travel at any speed without breaking physics, because it couldn't interact with things and thus couldn't be used to send signals or break causality. Neutrinos are near that limit, but not quite - obviously, since we can detect them.

More to the point, the paper's authors mention that many other neutrino studies report measuring time delays consistent with c, including neutrino bursts from Supernovae. The fact that most neutrinos seem to travel at c, except in this one experiment, suggests that the result is erroneous in some way - either a mistake, or something specific to the experimental conditions (free space compared to miles of rock, water, or whatever).
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Re: Scientists make startling discovery

Postby Mukat » Fri Sep 23, 2011 3:03 pm

When I said negative mass, I was referring to the principle that as an object approaches light speed, its mass increases exponentially, meaning the energy required to accelerate it more increases exponentially. Could a measurable particle attain a negative mass, or even a zero mass, to accelerate past light speed? Or could having a negative mass simply mean that it can't move slower than light speed? This is assuming all our physics get thrown out the window and a particle having negative mass and existing is possible.

Here's what I'm referring to.
These concepts seem deceptively simple, but they have some mind-bending implications. One of the biggest is represented by Einstein's famous equation, E = mc², where E is energy, m is mass and c is the speed of light. According to this equation, mass and energy are the same physical entity and can be changed into each other. Because of this equivalence, the energy an object has due to its motion will increase its mass. In other words, the faster an object moves, the greater its mass. This only becomes noticeable when an object moves really quickly. If it moves at 10 percent the speed of light, for example, its mass will only be 0.5 percent more than normal. But if it moves at 90 percent the speed of light, its mass will double.
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Re: Scientists make startling discovery

Postby Treck » Fri Sep 23, 2011 3:04 pm

theckhd wrote:The fact that most neutrinos seem to travel at c, except in this one experiment, suggests that the result is erroneous in some way - either a mistake, or something specific to the experimental conditions (free space compared to miles of rock, water, or whatever).

Its obviously not proven to be correct, yet.
But they also wouldnt publish it if there was some "simple" explanation for the error.

No offence to you Theck, but i dont think theres anything you could come up with that they havnt tried for explaining what happened.
None is obviously taking this as facts just yet, and while it could be a possibility, its far far from rewriting our physic books.

It might very well just be some programming error with the software, some faulty equipment or whatever that could give weird results aswell, altho they do keep it all in very very good shape to get as accurate information as possible.

The implications of what this could mean is hard to speculate as we have no idea why it would to appear if its the case.
I find it interesting that a lot of people start asking if this will make us able to travel between stars cuz of this discovery, when FTL travel (faster than light) IS theoreticly possible without breaking the laws of relatively. So while this could bring us one step closer, FTL travel within the laws of relatively is still very interesting.
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Re: Scientists make startling discovery

Postby Sabindeus » Fri Sep 23, 2011 3:31 pm

Treck wrote:No offence to you Theck, but i dont think theres anything you could come up with that they havnt tried for explaining what happened.


No offense to you Treck, but I'm curious why you think that?
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Re: Scientists make startling discovery

Postby Jeremoot » Fri Sep 23, 2011 3:38 pm

While I agree that it's very unlikely to be a miscalculation or oversight on their side, it's also equally as unrealistic that a subatomic particle really did exceed the speed of light. We shouldn't dismiss any possible error they could have made.

Part of me wants it to be true though. I really hope it traveled faster than the speed of light and is a repeatable observable phenomenon. That opens up so many mysterious doors into the unknown.
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Re: Scientists make startling discovery

Postby Treck » Fri Sep 23, 2011 3:58 pm

Sabindeus wrote:No offense to you Treck, but I'm curious why you think that?

They would not publish this if they knew what went wrong.
And while i dont know exactly what Thecks physic's education entails, i still think (and hope) the scientists working with this on Cern would have a better idea on what they are suppose to be doing.

Jeremoot wrote:While I agree that it's very unlikely to be a miscalculation or oversight on their side, it's also equally as unrealistic that a subatomic particle really did exceed the speed of light. We shouldn't dismiss any possible error they could have made.

Both parts seem very unlikely, but can both be wrong?
I Honestly do NOT beleave their data is correct.
And im saying that for 2 reasons, the first is that ive grown up with this find beeing a complete impossibility so reshaping that idea is hard to just accept like that.
Secondly i really would love for it to be true, as that would mean we are one step closer to understanding how everything works, so if i beleave its not correct data, atleast i cant get disapointed.

Jeremoot wrote:I really hope it traveled faster than the speed of light and is a repeatable observable phenomenon. That opens up so many mysterious doors into the unknown.

Warp theory has been a physical possibility the last 30years or smth, a particle moving faster than light has not, why would this suddenly get everyone attention to travel between stars?
Not to mention a) your not build of neutrinos so even if they move faster it might not mean you can, and b) the neutrinos they observed moved like what? 0.00025% faster than the speed of light? so you would be at the closest star about 5sec earlier than by traveling at c
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Re: Scientists make startling discovery

Postby theckhd » Fri Sep 23, 2011 4:01 pm

Treck wrote:Its obviously not proven to be correct, yet.
But they also wouldnt publish it if there was some "simple" explanation for the error.


1) It's not published yet, it's on the arXiv, which is not peer-reviewed.
2) It's true, if they had found a "simple" explanation for the error, then they wouldn't have put this issue out there. However, tunneling delay times are hardly a simple issue, which is why they're still not well-understood today. And you can definitely observe apparently faster-than-light transmission in those structures. Trust me on that one, I wrote a whole thesis on it.

Treck wrote:No offence to you Theck, but i dont think theres anything you could come up with that they havnt tried for explaining what happened.


....

Right, because I'm just a math guy on a forum somewhere.

Pay no attention to the fact that I'm defending a Ph.D. thesis next week centered on measuring and explaining faster-than-light quantum particle tunneling. That's obviously not relevant to the topic at hand. Or something.

The implications of what this could mean is hard to speculate as we have no idea why it would to appear if its the case.
I find it interesting that a lot of people start asking if this will make us able to travel between stars cuz of this discovery, when FTL travel (faster than light) IS theoreticly possible without breaking the laws of relatively. So while this could bring us one step closer, FTL travel within the laws of relatively is still very interesting.


I'll tell you what, speculate all you want, I'll give you $1000 USD if this ends up leading to a true causality violation, and isn't just a simple particle wavefunction reshaping effect. Because I guarantee that nothing they observed is going to violate causality, and in all likelihood it's not even at odds with our current understanding of physics. Just like every other "ooh we've got faster-than-light propagation" news articles over the past 20 years that turned out to be something mundane. Plus, I can always mail myself from the future if I lose the bet!

Also, FTL travel isn't theoretically possible without breaking the laws of relativity, at least as far as we know. If you're basing that on what I said, you're again confusing "travel" with "particle detection," which are two very different things. Think of it this way - sending a massive object faster than the speed of light is the same as sending information, so if information can't travel faster than c, neither can a massive particle, at least in any sense that has meaning.
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Re: Scientists make startling discovery

Postby Sabindeus » Fri Sep 23, 2011 4:07 pm

Treck wrote:And while i dont know exactly what Thecks physic's education entails, i still think (and hope) the scientists working with this on Cern would have a better idea on what they are suppose to be doing.


No but I think you missed my point. You don't know Theck's education background, nor do you know that of the scientists reporting this find, so how can you come to the conclusion that his education differs/is somehow worse/better than the CERN scientists?
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Re: Scientists make startling discovery

Postby theckhd » Fri Sep 23, 2011 4:11 pm

Treck wrote:And while i dont know exactly what Thecks physic's education entails, i still think (and hope) the scientists working with this on Cern would have a better idea on what they are suppose to be doing.


Also, let's go back to this point for a second. Don't get lulled into an "appeal to authority" argument. The scientists at CERN are scientists, not gods. They can and do make mistakes, just like all of us do. Let's look at exactly what they're reporting:

1) They observed particles appearing to travel faster than c. This isn't news; we've known how to do this with electrons and photons for years now under the right circumstances.

2) They claim to have looked at and ruled out most of the obvious circumstances that would explain the phenomenon based on (1). Whether they did or not needs more scrutiny, but the easiest explanation for the effect is that they simply overlooked one such circumstance.

3) They do not claim to have an explanation for the effect. That's important, because it means they don't trust the result yet. They're basically asking for other people to find their mistake. That's not shameful - sometimes it just takes another set of eyes, or a set of eyes from a discipline where the effect you're seeing is more common and better understood.

That's why I hesitate to comment on the neutrino-ness of the experiment. I'm not a nuclear physicist, it's not my area. I only have a rudimentary understanding of that area, and I wouldn't expect a neutrino particle physicist to have a deep understanding of my small sub-field of nonlinear optics.

4) They have not demonstrated faster-than-light information transfer, which is the key component to making any claims about causality violation. They're very careful to avoid making statements like that for good reason - I suspect that even they don't believe it's possible, so they don't want to be mis-quoted as such (even though they will anyway - the media is terrible about this sort of thing).
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Re: Scientists make startling discovery

Postby Jeremoot » Fri Sep 23, 2011 4:13 pm

Theck is a Laser Physicist by trade, he doesn't just do it for fun. He has a better understanding of this than I or most people on this forum ever will. :lol:

Obviously I can't say that he would be better at determining an explanation for the study at hand, but I'm sure he has a pretty damn good handle on it.
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Re: Scientists make startling discovery

Postby Treck » Fri Sep 23, 2011 4:25 pm

theckhd wrote:....

Right, because I'm just a math guy on a forum somewhere.

Pay no attention to the fact that I'm defending a Ph.D. thesis next week centered on measuring and explaining faster-than-light quantum particle tunneling. That's obviously not relevant to the topic at hand. Or something.

I never said that.
And you are obviously more than well versed in the topic, even so i still think the team at Cern handling this issue might be more qualified, i could be wrong.

theckhd wrote:I'll tell you what, speculate all you want, I'll give you $1000 USD if this ends up leading to a true causality violation, and isn't just a simple particle wavefunction reshaping effect. Because I guarantee that nothing they observed is going to violate causality, and in all likelihood it's not even at odds with our current understanding of physics. Just like every other "ooh we've got faster-than-light propagation" news articles over the past 20 years that turned out to be something mundane.

I never did any speculating.
And i DONT think their data is correct, but since i dont work at Cern and only studied a bit of physics on university level i cant even begin to speculate how they got the results they got.

theckhd wrote:Also, FTL travel isn't theoretically possible without breaking the laws of relativity, at least as far as we know.

FTL travel without moving faster than light, through manipulation of spacetime, is theoreticly possible within the laws of relativity.
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Re: Scientists make startling discovery

Postby theckhd » Fri Sep 23, 2011 4:33 pm

Treck wrote:
theckhd wrote:Also, FTL travel isn't theoretically possible without breaking the laws of relativity, at least as far as we know.

FTL travel without moving faster than light, through manipulation of spacetime, is theoreticly possible within the laws of relativity.


Are you sure about that? Is manipulating spacetime even possible, outside of a black hole or some other singularity? I'm asking honestly here, because I don't know - I have very little experience with General Relativity, which is where warping spacetime would come into play. But I was under the impression that even in GR with highly-warped space time, Einstein causality was preserved.
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