Can Anything Travel Faster Than Light - Explained Simply

[DaveC426913]

The dot is not even a non-physical object; it is simply an illusion created by our minds linking what are actually unconnected events. When we think we are seeing "a" superluminal object, we are mistaken when we label it "a" (as in "one") object at all.

 

[Kaleb]

We could do the "Mirror at lightspeed" experiment which proves that c is constant depending on the reference frame.

 

[Danger]

We could do the "Mirror at lightspeed" experiment which proves that c is constant depending on the reference frame.

Actually, the entire point of Relativity is that the speed of light is constant regardless of the reference frame.

 

[dst]

The dot is not even a non-physical object; it is simply an illusion created by our minds linking what are actually unconnected events. When we think we are seeing "a" superluminal object, we are mistaken when we label it "a" (as in "one") object at all.

But technically it is "a" object, mathematically. Take an example someone posted here for instance, a (very very long) train moving from A=>B at a speed nearing c. Now to make part of the train exceed c or equal c, we just keep removing the cars at the back. That shifts "the tail of the train" forwards with respect to the original reference point since coordinates of the tail will obviously change at a rate faster than c (and if you want to be pedantic, each train car is a Planck length long).

Same thing with the superluminal light dot, you could think of it as a "train" of photons and so.The point being, as said in this quote:

Then it becomes instantly clear that wave functions are not "things" but are like the reference point of the breaking wave, conceptual entities we use to describe actual physical phenomena. No mystery and no paradox.

 

[Kaleb]

Actually, the entire point of Relativity is that the speed of light is constant regardless of the reference frame.

That was what I was trying to imply. Sorry if it came out that I was questioning the constant frame of c dependent on the reference frame.

 

[Count Iblis]

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"

 

[Danger]

That was what I was trying to imply. Sorry if it came out that I was questioning the constant frame of c dependent on the reference frame.

No worries, mate.
This is a damned difficult field to get handle on. I apologize for misinterpreting your previous post. Apparently, we work together well.

 

[Danger]

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"

Sounds like bull**** to me, but I'll wait for one more educated than me to weigh in.

 

[Loren Booda]

Virtual particles, not directly measurable, may be considered as FTL if c<v<h/mx; that is, as long as the particle velocity is less than Planck's constant divided by the particle mass and its characteristic displacement.

 

[Count Iblis]

Sounds like bull**** to me, but I'll wait for one more educated than me to weigh in.

Just read the article (written by physics professors and published in a reputable peer reviewed journal). The problem is really that textbooks oversimply things when discussing this topic, leading to many people to misunderstand this topic.

 

[Danger]

I'm not denying that there's a peer-reviewed journal out there; it's just that the one in the link appears to be total bull****. Show me a valid link, and I'll retract my statement on the spot.

 

[Count Iblis]

I'm not denying that there's a peer-reviewed journal out there; it's just that the one in the link appears to be total bull****. Show me a valid link, and I'll retract my statement on the spot.

Sorry, but there is nothing wrong with the preprint version of the paper I linked to.

 

[Danger]

Mayb not to you, but there is to me. For one thing, I can understand everything that they say. That alone is enough to negate their relevance.

 

[Count Iblis]

Mayb not to you, but there is to me. For one thing, I can understand everything that they say. That alone is enough to negate their relevance.

You did not understand it at all, perhaps because you don't know much about special relativity and physics in general.

 

[Count Iblis]

http://arxiv.org/abs/gr-qc/0107091"

Stefano Liberati (U Maryland), Sebastiano Sonego (U Udine, Italy), Matt Visser (Washington University in Saint Louis)
(Submitted on 27 Jul 2001 (v1), last revised 14 Feb 2002 (this version, v2))
Abstract: Motivated by the recent attention on superluminal phenomena, we investigate the compatibility between faster-than-c propagation and the fundamental principles of relativity and causality. We first argue that special relativity can easily accommodate -- indeed, does not exclude -- faster-than-c signalling at the kinematical level. As far as causality is concerned, it is impossible to make statements of general validity, without specifying at least some features of the tachyonic propagation. We thus focus on the Scharnhorst effect (faster-than-c photon propagation in the Casimir vacuum), which is perhaps the most plausible candidate for a physically sound realization of these phenomena. We demonstrate that in this case the faster-than-c aspects are ``benign'' and constrained in such a manner as to not automatically lead to causality violations.
Comments: Plain LaTeX2E; 25 pages; 4 embedded figures (LaTeX pictures). V2: Some discussion clarified, minor rearrangements, references updated, no change in physics conclusions. To appear in Annals of Physics
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
Journal reference: Annals Phys. 298 (2002) 167-185

 

[Danger]

Do I smell a troll...?
What I do or not believe is not for you to judge.

 

[Count Iblis]

So, Danger, care to explain in detail why the (peer reviewed) paper is nonsense?

 

[Count Iblis]

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.

 

[Danger]

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..

 

[Count Iblis]

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.

 

[Danger]

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.

 

[RetardedBastard]

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"

I'd be interested to hear what some of the nerds, err, experts 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?).

 

[Danger]

I suspect that Iblis is out for the Count, pardon the expression.

 

[Count Iblis]

The paper was published in Annals of Physics:

Annals Phys. 298 (2002) 167-185

 

[ZapperZ]

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.

 

[RetardedBastard]

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 :)

 

[Doc Al]

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"

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" )

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. )

 

[ZapperZ]

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.

 

[yuiop]

In 1935 Einstein, Podolsky, and Rosen, introduced the thought experiment largely referred 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.

 

[Count Iblis]

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.

 

[RetardedBastard]

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!