Faster than light.

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  • #51
Danger
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Do I smell a troll...?
What I do or not believe is not for you to judge.
 
  • #52
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So, Danger, care to explain in detail why the (peer reviewed) paper is nonsense?
 
  • #53
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Do I smell a troll...?
What I do or not believe is not for you to judge.
You are behaving as a troll, not me, by stating that the paper is flawed and then not discussing the paper, just repeating that it is wrong.
 
  • #54
Danger
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I didn't say nonsense... I said 'bull****'; there's a difference. And I am going to turn this over to those more educated and articulate than me. No matter what I say, it won't make an impression upon anyone, including you, because I'm a high-school drop-out. I defer to the experts here, of which I'm not one. If they agree with me, great. If they disagree, even greater... because I will be further educated by their disagreement..
 
  • #55
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I didn't say nonsense... I said 'bull****'; there's a difference. And I am going to turn this over to those more educated and articulate than me. No matter what I say, it won't make an impression upon anyone, including you, because I'm a high-school drop-out. I defer to the experts here, of which I'm not one. If they agree with me, great. If they disagree, even greater... because I will be further educated by their disagreement..
Well, it is simply wrong to say that "No matter what I say, it won't make an impression upon anyone, including you, because I'm a high-school drop-out".

In science, "arguments by authority" simply don't count. If you had written that paper then it would have been published too, only the validity of the arguments matter. Also, if you are interested in physics, you should simply take your time and read the paper.

You won't be educated at all if you simply accept what someone else says as Gospel.
 
  • #56
Danger
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I never accept somthing that anyone says as 'gospel', particularly since I'm an Atheist and therefore that term is meaningless. I do, however, tend to accept (with a grain of salt) the opinions of those who have more experience and education in whatever topic is in question. Neither Astronuc nor Brewnog are my childhood heroes, but there's no bloody way in the world that I would argue against them in matters of Engineering (or common sense, for that matter).
Seriously, man... I'm out of this discussion. I don't know whether I'm right or wrong; I just know that I don't want to get into a confrontation.
Cheers, mate.
 
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  • #57
Faster than c signals do not necessarily violate special relativity or causality at all. Indeed, a well known example of faster than c signals are photons in the Casimir vacuum, http://arxiv.org/abs/gr-qc/0107091" [Broken]
I'd be interested to hear what some of the nerds, err, experts :smile: here think about the validity of this paper myself. Arxiv isn't working for me right now ("Server not found" error, strange). If this paper's been published in a peer-revied journal then it would add some weight to it, so has it been been published? Again, I can't check arxiv for any links since arxiv isn't loading right now (for me?).
 
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  • #58
Danger
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I suspect that Iblis is out for the Count, pardon the expression.
 
  • #59
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The paper was published in Annals of Physics:

Annals Phys. 298 (2002) 167-185
 
  • #60
ZapperZ
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Did someone forget to mention that, unlike the NEC paper, etc., this is a theoretical paper that has yet to have any experimental verification?

Now someone can ask "Yeah, so?" Well, this isn't really unique, nor the first time there is a theoretical prediction of something like this, is it? Predictions of violation of Lorentz invariance, and predictions from "quantum foam" effects all have parts that would violate one or more aspects of SR, be it the speed of photons, etc.

So my personal opinion is that there really is nothing to be worked up on, unless we intend adopt string theory-like operations and ignore the necessity of experimental measurement first. This is simply one more in a line of theoretical development that is waiting for such verification.

Zz.
 
  • #61
Now someone can ask "Yeah, so?" Well, this isn't really unique, nor the first time there is a theoretical prediction of something like this, is it? Predictions of violation of Lorentz invariance, and predictions from "quantum foam" effects all have parts that would violate one or more aspects of SR, be it the speed of photons, etc.
OK. And yet, Count Ibilis stated earlier:
Faster than c signals do not necessarily violate special relativity or causality at all. Indeed, a well known example of faster than c signals are photons in the Casimir vacuum, see here for a detailed discussion"
So, unless I got struck with the dumb stick, the part of your statement that I highlighted in bold seems to be in a little bit of a contradiction with what Ibilis is saying (that there's a peer-reviewed paper out there showing in-paper FTL signals WITHOUT violating SR). So... my question is... who's right? Is it really possible (albeit only mathematically at the moment) to show FTL signals that is consistent with SR?

So my personal opinion is that there really is nothing to be worked up on, unless we intend adopt string theory-like operations and ignore the necessity of experimental measurement first. This is simply one more in a line of theoretical development that is waiting for such verification.

Zz.
C'mmon, that's going to take forEVER! And you know it :)
 
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  • #62
Doc Al
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Faster than c signals do not necessarily violate special relativity or causality at all. Indeed, a well known example of faster than c signals are photons in the Casimir vacuum, http://arxiv.org/abs/gr-qc/0107091" [Broken]
This paper deals with the Scharnhorst effect.

Here's another published paper on the topic by Heidi Fearn (Laser Physics vol. 17 No. 5 pp1-5 2007): Can Light Signals Travel Faster than c in Nontrivial Vacuua in Flat space-time? Relativistic Causality II (http://arxiv.org/abs/0706.0553" [Broken])

From the abstract:
In this paper we show that the Scharnhorst effect (Vacuum with boundaries or a Casimir type vacuum) cannot be used to generate signals showing measurable faster-than-c speeds. Furthermore, we aim to show that the Scharnhorst effect would violate special relativity, by allowing for a variable speed of light in vacuum, unless one can specify a small invariant length scale. This invariant length scale would be agreed upon by all inertial observers. We hypothesize the approximate scale of the invariant length.​

So the issue of whether you can actually generate such "faster than c" signals or that such signals would not violate relativity is controversial. Getting a paper published in a peer-reviewed journal is just the first step. (Especially a theoretical paper. :wink:)
 
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  • #63
ZapperZ
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OK. And yet, Count Ibilis stated earlier:


So, unless I got struck with the dumb stick, the part of your statement that I highlighted in bold seems to be in a little bit of a contradiction with what Ibilis is saying (that there's a peer-reviewed paper out there showing in-paper FTL signals WITHOUT violating SR). So... my question is... who's right? Is it really possible (albeit only mathematically at the moment) to show FTL signals that is consistent with SR?
Any violation of Lorentz invariance would be a strong indicator that some part of SR isn't quite right. Various flavors of String Theory have some aspects of such violation.

C'mmon, that's going to take forEVER! And you know it :)
Who ever said that physics is easy?

Of course, if you don't have an issue with accepting something without experimental evidence, then that's your problem, isn't it?

Zz.
 
  • #64
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In 1935 Einstein, Podolsky, and Rosen, introduced the thought experiment largely refered to as the EPR paradox. In it Einstein argues that Quantum Mechanics is an incomplete theory because because QM has effects that are non-realistic and non-local. The non-local part refers to the fact that QM implies FTL interactions. Einstein suggested that since signals can not travel faster than light then QM is a flawed theory. The arguments of EPR were largely rejected at the time and countless real experiments have shown that Bell's inequalities are violated. Einstein's objection to QM on the grounds that it violates SR in some circumstances turned out not to be a valid objection as QM has been experimentally confirmed to a higher degree of accuracy than SR has. It turns out that SR and QM are incompatible. In other words Einstein lost that argument, and nature seems to be able to use FTL interactions at a sub level. However the FTL QM interactions can not be used to send meaningful premeditated FTL signals from one sentient observer to another.
 
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  • #65
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I just looked at Heidi Fearn 's paper. There is a lot of rhetoric but little physics in the paper. Thing is that the Sharnhorst effect is a consequence of QED, so it cannot possibly violate SR unless the derivation of the Sharnhorst effect is erroneous. The paper suggests that it could be erroneous, but doesn't prove that it is.

And Sharnhorst effect or no Sharnhorst effect, faster than light signals do not automatically lead to causality violations. In each case you need to explicitely show how to create a causal paradox, e.g. create (on paper) a device that will send a signal into its own past such that it won't send the signal later if it had received the signal earlier.

In case of the Sharnhorst effect, it turns out that you cannot use it to make such a device. In case of tachyons that move faster than light and can be received and transmitted without any restrictions, you can create such a paradoxical device.
 
  • #66
Who ever said that physics is easy?
Well, since you HAD to ask... according to google, there are 97,400 results for "physics is easy" :) And, that's just ONLY english results!

Of course, if you don't have an issue with accepting something without experimental evidence, then that's your problem, isn't it?
Hey, you can't use that line on me, I'll all FOR experimental evidence!
 

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