Talk:Faster-than-light/Archive 3

Archive 1

Archive 2

Archive 3

Archive 4

Misunderstanding (again)

Discussion, continued on 216.239.77.231's talk page

I'm consolidating the IP editor's responses to 2009 and earlier threads here, rather than reviving months-dead threads. --Christopher Thomas (talk) 22:19, 5 November 2010 (UTC) Take them out of context, so they no longer make as much sense. Gee, don't ever expect fairness from the people at Wikipedia! And I've gotten a warning from a Wiki person who has just ignored that my whole point was to improve the article by removing the misunderstanding about what SR says. No doubt I'm also being banned again. 216.239.77.231 (talk) 04:18, 6 November 2010 (UTC) (Originally repeated in two other sections:) I note that over a number of months, no one has come up with any explanation that special relativity sets out ANY method or mechanism by which faster than light would be stopped, prevented, or prohibited. SR does not put out ANY kind of hand that stops acceleration. It may reach the point where, from a particular observer's frame, the object can't be seen any more. But that doesn't make the object stop or no longer exist. Isn't it time to correct the article? 216.239.77.231 (talk) 06:51, 5 November 2010 (UTC) (Similar comment from a third section:) An object can't be seen or measured to have that. But what stops an object from accelerating faster? Or causes it to stop existing? Again, this is confusion between what can be seen or measured, and what can actually be done and exist. Of course something can keep accelerating and even though neither of us can see it any more, it still exists. 216.239.77.231 (talk) 07:13, 5 November 2010 (UTC) (Originally in response to: No, there is no frame in which anything is travelling faster than c. The two objects are travelling at less than c but in opposite directions. Martin Hogbin (talk) 20:07, 3 February 2009 (UTC)) But that frame is no more valid than any other. Consider their speed relative to each other. That's a perfectly valid frame of reference. They can't see each other, but I can them both. And I logically conclude they are going at close to 2c. 216.239.77.231 (talk) 07:08, 5 November 2010 (UTC) (Originally inserted into a 2009 thread:) Ever heard of the concept of weasel words. That's what it sounds like when one says 'rules that apply to relative velocities ... do not apply ... in comoving coordinates ..." etc. We would normally say it is FTL. There seem to be weasel words to try to make it not FTL, when we would normally call it FTL. Again, maybe it is time to change the article? 216.239.77.231 (talk) 07:08, 5 November 2010 (UTC) Hi anon, please read our wp:talk page guidelines. We are not supposed to use this talk page to talk about the subject, but about the aritcle. If you like to add content, remove content or have objections to some of the content, please propose modifications, and provide reliable sources for them. If on the other hand you have questions about or objections against the subject, please consider using the reference desk. I have left a message on your talk page. DVdm (talk) 23:25, 5 November 2010 (UTC) I have TRIED to talk about the article. I have proposed modifications. People here reverted WITHOUT explanation and WITHOUT discussion. They didn't use the talk page. Indeed at one point I referred people here. That was ignored. But just ignore the facts. Say I have not talked about the article, when I have. Go ahead ban me. 216.239.77.231 (talk) 'Bold text To the anonymous editor: You keep saying "SR does not put out ANY kind of hand that stops acceleration.". What happens is that the effective mass of the spaceship increases indefinitely making it harder and harder to accelerate as the object approaches the speed of light. Also, other changes to the spaceship occur which make it seem to those on-board that they are still c slower than light speed. The effective (relativistic) mass of the spaceship is $M={\frac {m}{\sqrt {1-{{v^{2}} \over {c^{2}}}}}}=m+{\frac {K}{c^{2}}}\,$ where m is the rest mass of the spaceship; v is its speed; c is the speed of light in a vacuum; and K is the spaceship's relativistic kinetic energy. JRSpriggs (talk) 04:56, 6 November 2010 (UTC) Thank you for actually addressing the issue that should be addressed in the article. What if, to an observer from another point of view, the spaceship perhaps isn't even close to c. For that observer, the mass of the spaceship isn't nearly infinite. To that observer, the spaceship has no problem accelerating. Again, what SR is talking about is what you can see or measure from a particular viewpoint. And the viewpoint from which it is seen to be close to c, is no more valid than any other viewpoint. So it still remains SR can't actually stop the spaceship. 216.239.77.231, As DVdm says this is not the place to discus your personal opinion on relativity, you can use reference desk for that or your own talk page if you wish. Martin Hogbin (talk) 10:28, 6 November 2010 (UTC) I have no desire to discuss my personal opinion on relativity. Why accuse me of that? It should be clear that's NOT what I'm arguing. So, quite seriously, why accuse me of that? It's the article I've tried to discuss. I'm not even sure I have an opinion on relativity. It's been well-tested, verified, helps in research, etc., so what has anyone's opinion of it got to do with anything? What I am suggesting is that the article should refer to SR correctly, as set out by Einstein, as an explanation. Not as a mechanism. I continue to point out that my citation is what SR actually says. Can't find that? I'm sure many of you are perfectly capable of doing that. So that, in fact, continuing to demand OTHER citations from me is just a stubborn refusal to correct the article. Maybe because I rubbed people the wrong way. Maybe because a few people themselves hold the misunderstanding. Whatever. 216.239.77.231 (talk) 01:31, 7 November 2010 (UTC) To the anonymous editor: The above equation put forward by JRSpriggs is just one way of showing that SR does indeed put out hands that stop acceleration. Here is another one: look at Time dilation#Time dilation at constant acceleration. There is an object undergoing a constant proper acceleration g with initial coordinate speed v0 (and corresponding γ0. After a coordinate time t, the object's coordinate speed v(t) is given by $v(t)={\frac {gt+v_{0}\gamma _{0}}{\sqrt {1+{\frac {\left(gt+v_{0}\gamma _{0}\right)^{2}}{c^{2}}}}}}.$ With an inititial zero speed (v0=0, and thus γ0=1), this reduces to $v(t)={\frac {gt}{\sqrt {1+{\frac {\left(gt\right)^{2}}{c^{2}}}}}}.$ Now, as you can verify, for both expressions, we have that $\lim _{t\to \infty }v(t)=c,$ which says that the speed get closer and closer to the value c as time increases. "Only after an infinite time, the speed would become the speed of light", so to speak. This nicely puts out that hand to stop acceleration. This is derived and explained in just about every textbook that covers SR, so here in Wikipedia we must assume that it is beyond discussion, and there is not much we can do, even if we would not be able to accept or even understand this. If we don't like this, we must take it elsewhere. DVdm (talk) 10:37, 6 November 2010 (UTC) Again, Einstein stated that no one frame is absolute. Your and the other person are both assuming that framwork, where the speed appears to approach c, is the right or governing frame. There can be many others in which the speed is much less than c. SR talks about what you can see or measure. It is quite possible to logically calculate that from another observer's frame, the speed, mass, etc. are all quite different. So, again, no, there is no hand being put out. 216.239.77.231 (talk) 01:31, 7 November 2010 (UTC) Anon 216.239.77.231, I think that the problem here is that 'special relativity' is the currently supported view in physics circles and therefore all wikipedia articles need to reflect that fact. If it's any consolation to you, there are many people who disagree with the theory of relativity and I am one of them. As such, I am not going to attempt to try and answer any of your questions. I suggest to you that wikipedia is not the best place to discuss this topic. There are in existence many forums which discuss this subject and where people ask the very kinds of questions which you ask. I myself have just completed a full lap with a relativist in New York City and it didn't come to any conclusion. There comes a time when one needs to simply step off this particular merry-go-round. David Tombe (talk) 11:00, 6 November 2010 (UTC) Just as the wiki article misunderstands SR, so do many other texts and articles. Einstein was clear that there is no one right absolute framework that is more valid than any other. However we can't help seeing things from one framework, the one where we are, so it is very easy to talk as if what is seen from that framework is what 'actually' happens. We all too often talk as if what would be higher than c FROM OUR FRAMEWORK isn't possible. As if what is c in our framework is the limit. What it really is, is that you can't see or measure higher than c in ANY FRAMEWORK. Now I can logically CALCULATE that two objects in the universe would be moving apart at greater than c from my framework, but I can't see or measure such a thing. It doesn't mean that relativity stops them or slows them. They still keep moving apart faster and faster. But if, in any given framework, the calculated speed would be greater than c, that can't be seen or measured from that framework. In another frame, where that speed turned out to be less than c, they could be seen or measured. It is easy to forget that neither frame is more valid than the other. And to talk as if SR does something to stop the acceleration. That misstatement is indeed often found. You can find examples of it many places. But it remains neither frame is more valid than the other. The frame where the speed is less than c and more acceleration is still possible, is an equally valid frame. Einstein was clear on that. 216.239.77.231 (talk) 02:23, 7 November 2010 (UTC) I am not disagreeing with relativity at all. I'm not interested in discussing it either, really. Oh, I stepped away for many months. And noticed most of my points ABOUT THE MISUNDERSTANDING represented in the article, had gone unrefuted. 216.239.77.231 (talk) 01:31, 7 November 2010 (UTC) David Tombe, this remark is highly off-topic. In view of the fact that you just came back from a year long ban of editing physics related articles (specially related to the speed of light), I strongly encourage you to refrain from using this talk page as an anti-relativity forum. This is not a wp:SOAPBOX. DVdm (talk) 11:34, 6 November 2010 (UTC) Again, I'm not at all against relativity. It's been tested, verified, to a great extent. Read what I've actually said, rather than throw a false accusation against me. 216.239.77.231 (talk) 01:31, 7 November 2010 (UTC) A year long ban? Well, that's news to me. I was banned for a short time for having edit warred, even though it was the other people who edit warred. I used the discussion page. Other people kept reverting things 'Bold text'without explanation and without so much as a peep on the discussion page. Other people ignored any attempt to discuss. They did the warring, NOT me, so I appealed those bans. What, they banned me for a year for pointing out that I wasn't the offender? For daring to point out they had banned the wrong person? For pointing out that I hadn't in fact done what they said I did? Gee, if I am to believe you, the wiki people are even more unfair and unreasonable than I thought. Because I did walk away, hoping that with time people would gain some sense of perspective, I didn't know about that year ban. But I guess I shouldn't be surprised. 216.239.77.231 (talk) 01:40, 7 November 2010 (UTC) If you want to discus this subject further I suggest that you invite further discussion on your own talk pages. If you are not sure how to get to your talk page 216.239.77.231 just click the word 'talk' here. Martin Hogbin (talk) 11:18, 6 November 2010 (UTC) That seems pointless when no one here is actually interested in having the article corrected. I kept trying to discuss the ARTICLE. Nor should it be necessary since what I have tried to discuss is THE ARTICLE. There have been a few thoughtful people with a few good comments. Few, though. Most people would rather ignore whether the article needs fixing, and just bash me unfairly. 216.239.77.231 (talk) 01:31, 7 November 2010 (UTC) WP articles must be based on the current scientific consensus as described in reliable sources. Your opinion is not supported by any source, it your personal misunderstanding, which cannot be discussed here. Martin Hogbin (talk) 09:51, 7 November 2010 (UTC) If you click here it will take you to a discussion I have started on your talk page that goes over the problems with this article...--Novus Orator 01:50, 7 November 2010 (UTC) Please remove the material you have put on my talk page. My discussion was about correcting the article. People seem to instead want to edit war or discuss my apparent lack of etiquette etc. But the topic is the ARTICLE and so is on topic here. It is NOT on topic on my talk page, as it shouldn't be about me but about the article. Thank you. 216.239.77.231 (talk) 01:28, 9 November 2010 (UTC) The article as-written is correct. People have already explained to you why, many times over the course of many months. What you are doing now is called "disruptive editing", and will get you blocked and/or banned if it continues. Please stop immediately. --Christopher Thomas (talk) 01:45, 9 November 2010 (UTC) No, if you care about the actual facts, only a couple of people tried to explain how in their view the article was correct. 216.239.92.228 (talk) 12:45, 14 November 2010 (UTC) DIscussing the idea that special relativity cannot put a halt to continued acceleration and thus would allow for speeds beyond the speed of light, is discussing the validity of the theory, and therefore discusses the subject and the theory in which it is conceived. This is explained in the wp:talk page guidelines (please do have a look) . So we simply are not allowed to discuss this here, and we must do it elsewhere. User talk pages are ideal for this and we are allowed to discuss (almost) everything there. If you don't like something on your talk page, you are 100% free to remove it - that is also explained at wp:TPG. DVdm (talk) 07:40, 9 November 2010 (UTC) No, I am NOT discussing the validity of the theory. The theory says you can NOT see or measure anything greater than the speed of light. It has been tested and verified many times. I have been quite clear that I agree the theory is valid. You can of course ban me for something I have not done. It was done before. I won't be surprised if it is done again. 216.239.92.228 (talk) 12:45, 14 November 2010 (UTC) That, BTW, is why we can and do talk about the observable universe. As the theory says, you can't see a star or galaxy that would be retreating from us at greater than the speed of c. You might be able to LOGICALLY calculate that it still exists, and THEORETICALLY calculate its speed, and maybe even figure out where it is theoretically, but those will be merely guesses and nothing better. You simply can NOT see or measure it or detect its existence (not even once, never mind repeatedly) once it is beyond the limits of the observable universe. Because nothing can exceed c. 216.239.92.228 (talk) 13:00, 14 November 2010 (UTC) Please discuss these issues elsewhere. Martin Hogbin (talk) 13:34, 14 November 2010 (UTC)

I have repeatedly tried to talk about the article, and THAT is what this page is for. It is a FALSE accusation that my discussion is off topic. But I've gone into that on what is supposed to be my talk page. No doubt you don't want people to know that, and will delete this comment so they don't know to look there. 216.239.84.16 (talk) 10:06, 15 November 2010 (UTC)

OK, as this page is about how to improve the article, how exactly would you improve it, i.e. what needs changing and how? Please don't just say it is wrong as (i) that is of no use in helping to improve it and (ii) it will be dismissed as your opinion compared to a well written and well sourced article. If it is unclear then say so, but again say which part or parts of the article need clarifying. --JohnBlackburne^words_deeds 11:06, 15 November 2010 (UTC)

Unfortunately I'm not allowed to re-post the suggestions I've made. They amount to removing or modifying any wording that sounds like SR is some kind of force that stops or prohibits things. SR explains that you CAN'T go faster than c in any particular frame. That you can't do it. Period. Not that you're stopped or prevented in some way. You simply can't do it. 216.239.78.230 (talk) 12:28, 15 November 2010 (UTC)

I can't see where in the article it states that or anything like it. Which section are you referring to?--JohnBlackburne^words_deeds 12:38, 15 November 2010 (UTC)

I think there has been a long standing misunderstanding (NPI). See this comment at 216.239.77.231's talk page. DVdm (talk) 13:03, 15 November 2010 (UTC)

The article (current version) says:

Justifications

'Despite the established conclusion that relativity precludes FTL travel, some have proposed ways to justify FTL behaviour:'

Which as I have repeatedly pointed out is wrong. Relativity does not preclude FTL travel. It does nothing to preclude that happening. Relativity is not a mechanism, but an explanation. It explains why FTL travel can neither be seen, detected, or observed from our framework. That is, from our point of view anything that would be faster than c has no scientific existence. We might be able to theorize that someone kept accelerating their spaceship past what would be c from our perspective, but that would be purely theoretical, because we could never see, detect, or observe their spaceship doing that.

216.239.82.96 (talk) 11:05, 7 March 2011 (UTC)

Quantum mechanics

The article says:

'The uncertainty principle implies that individual photons may travel for short distances at speeds somewhat faster (or slower) than c, ...'

I don't see how the uncertainty principle implies that at all. I think we need some citations for that.

216.239.82.96 (talk) 10:51, 7 March 2011 (UTC)

Light spots and shadows

I think the following must be incorrect, even though it is cited with a reference.

Light spots and shadows

If a laser is swept across a distant object, the spot of light can easily be made to move at a speed greater than c.[8] Similarly, a shadow projected onto a distant object can be made to move faster than c.[9] In neither case does any information travel faster than light.

Not so. Light beams are NOT straight when moving. Imagine them as being like a coherent stream from a hosepipe. Move the hose and the stream is bent.82.0.25.104 (talk) 22:34, 24 March 2011 (UTC)Lance T.

This seems to assume a spot or shadow could not carry information even though if it were in the shape of a letter or number it could carry information. It is not that spots or shadows can't carry information, but that the light that creates the spot, or the light surrounding the shadow, will still travel at less than c. Take the case of a laser or shadow aimed at the moon. The light takes time to go to the moon and get back. We know this because communications between earth and astronauts on the moon did take time. It is neither instant nor faster than c. The light itself is not moving across the surface of the moon from one side to the other, but between the moon and us, and at less than c.

216.239.82.96 (talk) 10:34, 7 March 2011 (UTC)

A shaped light spot would carry information from the light source to the spot (at the speed of light) but it would not carry information from a place where the spot had been to a place where it move to. In other words, a rapidly moving light spot cannot be used to send a message faster than light. Martin Hogbin (talk) 22:58, 7 March 2011 (UTC)

I think maybe' you are agreeing. The point I'm making is that the spot or shadow might seem to move from one side of the moon to the other, but in fact the light is moving between the light source on the earth and the surface of the moon, and back to the observer on the earth, all at speeds less than c. There is no faster than c travel at all. 216.239.82.96 (talk) 06:04, 8 March 2011 (UTC)

216.239.82.96 (talk) 06:04, 8 March 2011 (UTC)

The light comprising the spot moves at c. The spot itself, which is an abstraction rather than a physical object, does in fact move faster than c. This might seem like an unimportant quibble except that it's closely analogous to the fact that phase velocities can be greater than c, which has very concrete implications (for example, for the way that X-rays refract, which is generally in the opposite direction to the refraction of visible light).

In any case, enjoyable as this is, it's gotten off-topic here. You have not identified anything incorrect in the article, and improvements to the article are what we're supposed to be discussing rather than the subject matter itself. --Trovatore (talk) 09:29, 8 March 2011 (UTC)

Well put. 216.239.82.96, if this is still not clear to you you can ask on refdesk or on my talk page. Martin Hogbin (talk) 12:10, 8 March 2011 (UTC)

Stiff rod example

Do we have a page that explains why the "if I had a stiff rod that was light years long and moved one end, don't I get FTL communication?" example does not work? That question is asked monthly on WP:RD/S. It would be nice if we could just direct the questioner to a premade answer. -- kainaw™ 15:27, 8 March 2011 (UTC)

I think this might be better in another article. This one covers things that do go faster than light, unless maybe we add a section on 'common fallacies' or 'thought experiments' or 'failed attempts' or something like that. Martin Hogbin (talk)

Well, answer to this is quite easy. If the long stiff rod is made of matter, it would require infinite torque to the close end to move the distant end even at the speed of c. 89.210.127.81 (talk) 08:47, 30 April 2011 (UTC)

Actually this is a slightly different question, so I'll rephrase it if I can.

Take a stiff rod one light year long and nudge the near end one meter over in one second using an acceleration of around one fifth of the pull of gravity at Earth's surface. Now, doesn't the far end move at the same time, sending the information forwards one light year in one second?

The answer is of course not. Any rod you have is not infinitely stiff and so any change on one end can only be transmitted through the rod at the speed of sound in the rod (to the extent that it still is a solid object). Why can't you have a rod in which the speed of sound exceeds the speed of light? Well that's because the mechanism for the transmission of sound through an object is based on a series of electromagnetic interactions between the atoms of the object and so obviously these interactions can not travel faster than light. Hcobb (talk) 16:49, 30 April 2011 (UTC)

Closing speeds

Could someone please add an explanation of why the velocities can't simply be added normally? Otherwise this sounds like a special rule made up solely for the purpose of denying this is faster than c even though it is faster than c. 216.239.82.96 (talk) 10:38, 7 March 2011 (UTC)

Physics does not claim to explain why things happen in any fundamental sense. It explains what happens in a way that we can understand. All the experimental evidence shows that velocities behave in the way described by that formula. 2.102.214.232 (talk) 12:00, 7 March 2011 (UTC)

the thing is i don't see why the speeds can't be added normally either. but what does make sense is that the equations are from the veiw point of a non-moving spectator. and the article does mention the fact that reletive to each other the particles are moving at faster than the speed of light. Kenneth Edward smith (talk) 01:52, 22 May 2011 (UTC)

I think the article should make clear that, in the frame of the third party observer, the two particles are moving at a velocity greater than c relative to one another (this is essentially the meaning of 'closing speed'). However, as the article correctly states, in the frame of either particle, the other particle never moves at greater than c. Martin Hogbin (talk) 09:17, 22 May 2011 (UTC)

Regarding adding the velocities normally, you can, of course, do that. The problem is that the answer we get does not match the result that we get when we do the experiment. Martin Hogbin (talk) 09:20, 22 May 2011 (UTC)

However that does not make sense because if the two particles are moving towards each other how would they not appear to break the light-barrier? if you could help clear this up for me that would help Kenneth Edward smith (talk) 23:33, 28 May 2011 (UTC)

Universal expansion

Again, this section reads as if galaxies are or will be retreating at faster than c, but we're going to try to deny somehow that they really are. I wonder if this section can be improved.

In my personal view, the explanation is that they are only theoretically going faster than c because once they go past c, they can no longer be seen, observed, or detected in any way. From our point of view, they are only theoretical. Because we can get no information about them any more.

Another explanation I've seen is that it is not that galaxies are actually receeding from each other, but that the space between them is expanding. Does that make sense?

216.239.82.96 (talk) 10:44, 7 March 2011 (UTC)

No, they actually are receeding from each other faster than c. This is permitted in general relativity, because space-time itself (and thus space itself) can expand without a speed limit. Objects embedded in expanding space thus draw away from each other faster than light, but they can't communicate with each other, so the limit to faster-than-light communication remains unbroken. SBHarris 22:54, 7 March 2011 (UTC)

I would agree that the galaxies are not moving faster than the speed of light; however I mean that they are not moving faster than c relative to each other. But if it were to be relative to the point of which the BIG BANG originated from they would appear to have receded at faster than c. Kenneth Edward smith (talk) 23:38, 28 May 2011 (UTC)

Interesting thought if somthing were moving away from you at faster than c and you were unable to observe it, would that be considered dark matter? because you can tell it is there but you can't see it or otherwise observe it. Kenneth Edward smith (talk) 23:40, 28 May 2011 (UTC)

Apparent FTL propagation of static field effects

This section, interesting and important as it is, needs drastically reducing in size. Any suggestions? Martin Hogbin (talk) 09:50, 8 March 2011 (UTC)

There are physicists who really believe that static force fields violate special relativity when their effects "propagate" at speeds faster than light. Van Flandern has been saying for years that gravitational waves travel at c, but that static gravity travels at 2e10 x c. Which is (of course) ridiculous. [1]. But readers who dream of sending signals faster than c need someplace to go an ready WHY it's ridiculous to consider static gravitational fields (or static EM fields, for that matter) as "signals." If you think this section is too long, it may be time for a separate article for it, per WP:SS. SBHarris 03:30, 29 May 2011 (UTC)

I agree that the section should be there and I do not want to support Van Flandern in any way. My complaint is simply that the section is too long. Maybe a separate article is a good idea, with a link from this one. Are you going to start one?Martin Hogbin (talk) 20:00, 1 July 2011 (UTC)

I cut 2 kB out, since I find most of the info is in the {main} articles above. Feel free to cut any more that you don't think detracts from the understandability. If somebody slaps a "too technical" tag on this section, I'll refer them to you. SBHarris 21:03, 1 July 2011 (UTC)

Deleted section by Bopomofo on good conductors.

I have deleted the above section, which was wrongly marked as a minor edit. It is based on what seems to be a highly speculative paper which has not been published in a peer-reviewed journal. Martin Hogbin (talk) 08:55, 29 May 2011 (UTC)

Energy velocity above c

I took it out [2] because it made no sense to me. I think its a reasoning-by-analogy type thingy, if so it needs to be made much clearer, and lose the "Don't misunderstand to be drift velocity of the charge carrier which is much slower" bit WMC 21:18, 31 July 2011 (UTC)

Tagging to signal displeasure

Sorry, what is the point of adding a "by whom" tag to a statement that is fully referenced?[3] You can argue that the statement doesn't warrant inclusion under WP:UNDUE, but it is silly to ask "by whom?" right in front of a footnote that answers this "question".

I am no fan of this neutrino thing myself. It is a non-issue inflated by journalism. So, by all means propose cutting down coverage on it under WP:DUE, WP:RECENT. But don't play the tagging game.

As far as I am concerned, this can be treated in a brief paragraph, without the excursus into multi-dimension science fiction. --dab (𒁳) 08:24, 26 September 2011 (UTC) --dab (𒁳) 08:24, 26 September 2011 (UTC)

I agree. (I wasn't the editor who placed that particular tag, by the way, though I admit I've tagged things in this article, in particular the multiple issues tag at the top, as I explained immediately above.) More and more it is starting to look like this incident deserves only the briefest mention, until such time as something comes of it, if something comes of it. All the speculation about possible explanations is just chatter, and it's very un-encyclopedic. I think we should include references to previous experiments which may have offered contradictory evidence, however.--Grapplequip (talk) 17:44, 26 September 2011 (UTC)

Tachyons Section

There's a bit in the tachyons section that needs further explanation methinks-

In 1985 it was proposed that the neutrino could have a tachyonic nature. This proposal was strongly criticized by some researchers, but this criticism was subsequently shown to be incorrect.

Here are the sources:

A. Chodos, A. I. Hauser, and V.A. Kostelecky, The Neutrino As A Tachyon, Phys. Lett. B 150, 431 (1985)

A. Chodos and V.A. Kostelecky, Nuclear null tests for space-like neutrinos, Phys. Lett. B 336, 295 (1994).

R. J. Hughes and G. J. Stephenson Jr., Against tachyonic neutrinos, Phys. Lett. B 244, 95-100 (1990).

A. Chodos, V.A. Kostelecky, R. Potting, E. Gates, Null experiments for neutrino masses, Mod. Phys. Lett. A7, 467 (1992).

-I looked up the sources, and based on the very slim abstracts I could find, and a little investigation of who Alan Chodos is, (I don't have academic access at the moment, nor am I a physicist) it seems like these sources are probably acceptable. But the way the information is put forward in the article is very odd. I don't think we're in the business of just telling people things were "shown to be incorrect." I for one would like to hear an explanation of why! Is there someone here with the physics aptitude/access to the sources who could explain it and put text to that effect in the article? Otherwise the section above is running afoul of WP:EGG, methinks. (i.e., references are not easter eggs) Further, the sentence itself is weak.

And just one more thing: While the above sources may simply explain how it's possible that one type of neutrino or another might be a tachyon, is that possibility part of the consensus view at all? This article has a lot of fringey stuff in it, and I'm just short of being able to tell whether this is an example. Can someone help?--Grapplequip (talk) 18:12, 26 September 2011 (UTC)

Particle Faster than Light

The experiment has done by the research center CERN is about the influence of air and other things on Neutrino's motion. But unfortunately, they have found that, the speed of the neutrino is faster than the speed of light which is violating the Einstein's special theory of relativity. If the experiment has done is perfect, then it can change the most important part of physics, the Quantum mechanics. In my opinion, it is not necessary to change the quantum physics for two reasons given below: (1) It is not sure that the speed of light has been measured by human is perfect. If the actual speed of light is greater than the speed of neutrino, then we can say that the special theory of relativity is true. Hence, now we should measure the speed of light again perfectly. (2) If the actual speed of light is lower than the speed of neutrino, than it is not necessary to change quantum physics. In that case we should develop a another physics for this type of particles which does not follow the special theory of relativity. Such as the development of quantum physics for the failure of classical mechanics to measure the position and velocity of an electron spontaneously. — Preceding unsigned comment added by Robi Kormokar (talk • contribs) 20:04, 28 September 2011 (UTC)

File:OPERA experiment.png Nominated for speedy Deletion

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Multiple issues tag: Explanation for it and discussion of solutions

Hi all,

This article contains large sections of un-sourced material, many of which include detailed discussions of and conjecture about scientific theory and the relevant mathematics. This, to my mind, qualifies it for synthesis, refimprove, and original research tags until such time as these sections are fully sourced. So I've gone ahead and added those tags. If something isn't done about the problem, I'd suggest that significant portions of the article should be deleted.--Grapplequip (talk) 22:01, 25 September 2011 (UTC)

And the problem keeps getting worse. Recent edits to the already messy section on the superluminal neutrino question are completely unsourced. I'm removing them.--Grapplequip (talk) 01:33, 26 September 2011 (UTC)

Hi Grapplequip, I'm an educated physicist (to Masters level) now working outside the field for many years and wanted to catch up on developments generally - nothing to do with neutrinos, actually inspired by a computer game about interstellar travel named 'Sword of the Stars'. On this page, apart from discussions of the superluminal neutrino 'claims' (I think it's putting it too high to call it a 'question') which definitely belong on their own page and not here apart from the briefest reference, all the rest of the current form of this article seemed to me to be excellent and exactly what I as a reader was looking for on the subject. It is useful in an encyclopaedia to have all these different concepts collated together on one page like this, even though the very editorial process of choosing what to include on the page involves some discrimination and therefore 'original research'. Which are the 'significant portions' you are proposing should be deleted? I would think you should be more specific about such a proposal. — Preceding unsigned comment added by 217.34.218.209 (talk) 11:39, 1 November 2011 (UTC)

Phase Velocities below c

I attempted to remove the entire section on phase velocities below c. The reason I attempted to remove it is that is highly misleading and the entire basis for its conclusion depends on tachyons, which are purely hypothetical and have never been observed. In attempting to follow the actual exposition presented in the section, I find it is poorly written and makes no sense to me. For example, it is stated that one equation is proportional to another, but as far as I can tell this is squarely not the case. Furthermore the section cites as a reference for this argument an arxiv article that has not been peer-reviewed. I do not think it is sound and, to the extent which it is sound, it should only be included in the section on tachyons, as it discusses a physical phenomenon which can only rightly be understood as a statement about tachyons. This removal attempt was flagged as a false positive and the edit was reverted. Please help by removing this section. --JRS, M.S. Physics — Preceding unsigned comment added by 209.147.138.150 (talk) 16:51, 1 October 2011 (UTC)

Guang-Jiong Ni measurements

This section uses very poor language. I can't even tell what it is saying at the end. It does read like it was written with English as a second language, and if that be the case, I thank the author for their contribution and hope they continue to post. The point being that the language should be improved now. I'm not going to edit it because Wikipedia is very political about what changes happen. This is why wikipedia is difficult to read. It's not because it is too smart. It's because it is poorly written and people can't make changes. For those who don't like user contribution it is incumbent on you to fix this problem. You don't have a right to be lazy while simultaneously telling the user he can't contribute.

The text seems to be copied from the French Wiki from this article, created by the same author, and extremely poorly google-translated (or something) . - DVdm (talk) 10:33, 17 October 2011 (UTC)

Also at some point the name reads "Guang-Jiong Ni" at some other it reads "Guang-Jiong Nor". Which one is correct ? -- 89.247.60.235 (talk) 21:25, 31 October 2011 (UTC)

I've had a go at improving the language, changing it to what I think the original author was trying to say, but I didn't check any of the references so I may have missunderstood parts of it. Will Bradshaw (talk) 11:30, 6 November 2011 (UTC)

Erroneous Information in "Light Spots and Shadows"

Off-topic on article talk page

There is a section titled "Light Spots and Shadows". The information states "If a laser is swept across a distant object, the spot of light can easily be made to move at a speed greater than c. Similarly, a shadow projected onto a distant object can be made to move faster than c." This information is incorrect. If the laser beam was swept across the sky with supposed faster-than-light speed, the beam of light would still have to wait for the speed of light to propagate the beam to the final "spot". An illustration of this is a jet of water coming from a hose. Though the hose's direction can be changed to a different direction, the water, which is being ejected (or emitted) at a fixed rate, still has to catch up to the new direction. A further illustration is what I will call the moon observer: light takes roughly 1.3 seconds to propagate from earth to the moon. If Mr. Laser Pointer were on the earth pointing his laser to the far right of the moon, then suddenly swept his laser to the far left of the moon, the moon observer would see the sweep pass his gaze 1.3 seconds "after" it actually happened. Neither the laser beam nor the "spot of light" suddenly became a rigid object that sweeps faster than the speed of light, but the beam is revealed to be what it is: a propagating stream of photons, which individually, still travel at the speed of light, and once they have left the laser emitter, they propagate in the immediate direction in which they were emitted, not being magically tied to the laser emitter. The photons are still travelling at the speed of light, and have to wait (as far as we are concerned) to reach whatever spots or distances we may "envision". It is the same with the shadows, since shadows are simply the absence or the blocking of the propagation of light, and can only be seen with reference to light propagation, or the blocking of. The photon still has a fixed period, and beams of light or the blocking of light emissions do not suddenly become rigid objects, millions of times longer than the distance of the moon to the earth. This erroneous information should be removed permanently. It has been on the site for several months. --Hypocritus (talk) 21:13, 1 November 2011 (UTC) I'm sorry, you're just wrong. --Trovatore (talk) 21:32, 1 November 2011 (UTC) @Trovatore... 1) The photon is the quanta of light, and light or photons travel at the speed of light (c). 2) untold numbers of them leave a laser pointer. 3) each photon travels at the speed of light, and is not chained to the photon behind it, in front of it, nor to the laser pointer, nor to the person's arm who redirected the laser pointer. 4) The "beam" that is moved will still propagate out like a wave (sweep of the coherent beam, not an EM wave) that, from our perspective, might look light it "beams to infinity, instantly". However it cannot do that. The beam that we actually "see" is at most a few dozen miles long, because of the air. If we were able to actually "see" the beam all the way to the moon, we would see that it actually hits the moon 1.3 seconds after being pointed at it, and that the waving of the pointer across the moon, doesn't actually propagate across the moon until 1.3 seconds after the action. 5) Light travels at the speed of light (c), whether it is a "point" of light, a "beam" of light, or a shadow which is the "absence" of light, created by the blocking or the cessation of light being emitted. Light travels at the speed of light through it's medium, whether air (close to c), water (about 3/4 c) or the vacuum of empty space (c). --Hypocritus (talk) 21:58, 1 November 2011 (UTC) You're still not getting it. The spot is not a physical object, nor even a collection of physical object. It is an abstraction, and abstractions are perfectly capable of traveling faster than light. ==Trovatore (talk) 22:50, 1 November 2011 (UTC) I've reworded the section in hopes of making it clearer. I've also moved the refs to the end, as the cited sources make the point that no FTL movement or transfer of information is involved here. @Trovatore I got it. The abstraction is flawed. Look at it. 1) Of course you can point your finger to one galaxy, then quickly point to another. But why would you even think to write such a thing as, "I just moved the spot I was pointing to faster than the speed of light!" ? 2) Also, the wording is counter productive. It is flat wrong. Let's look. "the spot of light can easily be made to move at a speed greater than c." No. The spot of light cannot easily be made to move at greater than c. If you seek to use the principle of an "abstract point", one should not use a "point of light" in seeking to convince others that "the point of light" is moving faster that the speed of light. 3) And worse, the "shadow" exists only because of the light. The shadow can only arrive because of the cessation of light. That means that the shadow can only arrive as fast as the last photon ceases to shine, which depends also upon the speed of that last photon. The shadow will arrive to the object, and to the observer, in the same fashion that the light did, at the speed of light, and no faster. By your own defense, the shadow "abstraction" is doubly flawed. The section is severely flawed, from the faster-than-light "spot of light" to the "moving shadow", moving faster than the speed of light. It should be removed, or severely reworked so as to not appear to create an "abstract" black hole which sucks all readers into it, faster than the speed of light. --Hypocritus (talk) 23:26, 1 November 2011 (UTC) You're just wrong. The argument is so terribly basic that I'm not going to argue it with you. --Trovatore (talk) 00:11, 2 November 2011 (UTC) Trovatore... are you the one who put in the erroneous information and terribly flawed arguements? I believe you are being a troll. I believe you should allow others to make a contribution to Wikipedia. Just because you don't grasp the concepts presented, does not make them wrong. I am confident that many readers can understand the flawed "abstraction". Language is a tool, and needs to be used skillfully for optimum benefit. The "spot of light" does not move faster than the speed of light. If you wish to defend such a notion, you should change your example to not include "Light" since light can't move faster than the speed of light. Remove the word "light" and you begin to have a "point". Also, place in the word "imaginary", because that is what your arguement is. The spot of light does not move faster than the speed of light. And the "shadows"..., I have spoken enough about that, but your defense of "abstraction" fails to even touch on the "shadows". This is a black hole of preposterousness. I believe that you are being a troll. The section should be scrapped. --Hypocritus (talk) 03:21, 2 November 2011 (UTC)

Hypocritus, this discussion is off-topic here. The section in the article is properly sourced. If you have a problem with it, this is not the proper place for you to come — see talk page guidelines. We have a reference desk for that. Please take your question and remarks to our wp:reference desk/science. Good luck. DVdm (talk) 08:59, 2 November 2011 (UTC)

Singular "they"? Looking for consensus -- please respond

Please have a look at this diff: http://en.wiki.x.io/w/index.php?title=Faster-than-light&action=historysubmit&diff=461903375&oldid=461863804

To me, the use of "they" as a singular form is so distracting as to damage readability. Do you think the singular "they" should be retained in this article? Thanks -- Jo3sampl (talk) 19:44, 22 November 2011 (UTC)

Well, I undid your edit because to me the "he or she" and "his or her" is far more damaging, and there seems to be no Wikiwide consensus for or against the usage of the "singular they" (see WP:Gender-neutral language), although it is used abundantly in the literature — and here. But if it hurts that much... perhaps we can replace "traveler" with "travelers" and put the section in "plural they". What do you (and others) think? DVdm (talk) 20:37, 22 November 2011 (UTC)

That's probably a little better, yes. Although many sources use singular they, there are enough readers who find it sufficiently grating that I think it should generally be avoided if we can. --Trovatore (talk) 20:51, 22 November 2011 (UTC)

If this would be a(nother) section about the twin paradox, we could do what some books do, make the stay at home twin male, and give him a female twin sister to make the trip. We can't do that here however. - DVdm (talk) 20:57, 22 November 2011 (UTC)

Using the conditional in place of the subjunctive is grating, too :-) --Trovatore (talk) 21:00, 22 November 2011 (UTC)

_{I was in dubio about adding a ;-) there, but decided not to :-) - DVdm (talk) 22:13, 22 November 2011 (UTC)}

The singular 'they' is more natural than 'he or she'. Either that or stick to the traditional 'he'. Both annoy some people Martin Hogbin (talk) 22:55, 22 November 2011 (UTC)

Here's how the reference desk responded:

The relevant point from Wikipedia:Manual of Style#Gender-neutral language is "As with all optional styles, articles should not be changed from one style to another unless there is a substantial reason to do so." Further to that, your change put "he or she" or "his or her" 5 times in one paragraph and was therefore particularly stilted, so I think the reversion was justified.

Yikes -- still think "singular they" is awful, but okay. -- Jo3sampl (talk) 00:18, 23 November 2011 (UTC)

I wonder whether that passage really reflects a broad consensus. There is a relatively small group of MOS regulars who have disproportionate influence, and one of them in particular has what I judge to be a politically motivated position on this point. --Trovatore (talk) 00:31, 23 November 2011 (UTC)

I think that Martin's point is that, sure, there might indeed be no broad consensus about the singular they (although it's really widely used) but there surely is such a consensus about wp:RETAIN, hence my edit summary. Note, I have restored the title of this talk page section to its original version — as soon as people have replied, I think it's best to keep the section title. - DVdm (talk) 07:51, 23 November 2011 (UTC)

Jo3sampl, have a read of Singular they. It is an excellent article. Martin Hogbin (talk) 09:49, 23 November 2011 (UTC)

Nonsensical sentence?

"Don't misunderstand to be drift velocity of the charge carrier which is too slow."

This sentence makes little sense as stated. A word may be missing between "misunderstand" and "to". David Spector (talk) 20:48, 29 November 2011 (UTC)

Neutrino - 50-60ms faster than speed of light

I lack the technical skill to add this but CERN or the research groups thereabouts measured neutrinos going 50-60ms faster than speed of light. 10ms margin for error. This is the second group to notice this, although the first time it was measured the experiment had a margin of error too high to make it conclusive.

They are calling for other groups to retry the experiment, which gives us 3 for three, and a possible confirmed discovery.

The implications of this are massive, rendering pretty much anything in the travel or communications area of science-fiction potentially into science fact. (ftl, subspace, possibly crazy stuff like hyperdrive/jump gates too since it could be used to sync both ends of the trip etc) Although likely prohibitively expensive.

It is also significant as a solid measurable particle (old faithful) can now do it, prior to this the only way the effect could be achieved is the less reliable spooky areas of quantum physics entanglement, states and the like.

At the very least in the short term, we now have a technology arc for lower latency communication research. Interesting times indeed.

NB - another article states its billionths of a second not millions(ms) (that's why its on the talk page!) still fascinating nonetheless.

ms would actually be milliseconds, which means thousandths of a second. In any case neither ms, nor "millionths of a second," nor "billionths of a second" are measurements of Velocity, or of velocity differences, at all. Billionths of a second over what distance? Jeh (talk) 02:01, 23 September 2011 (UTC)

If these results are confirmed, there will be plenty of time to update, not just this article, but pretty much the entire corpus of Wikipedia physics articles. For now there is nothing that needs to be done about it. Get as excited as you like, but don't change articles until there's more to go on. --Trovatore (talk) 02:07, 23 September 2011 (UTC)

It's actually 50-70 nanoseconds (60 nanoseconds with a margin of error of 10 nanoseconds). There are a bunch of online articles that could be used as sources. Right now, if you just google "faster than speed of light" and look at the news results, there are many possible references. Alphius (talk) 02:12, 23 September 2011 (UTC)

Also, the distance this occured over was approximately 454 miles. Alphius (talk) 02:13, 23 September 2011 (UTC)

"Possible references" is not really the point. Even the guys who reported the results don't really believe them. The overwhelmingly most likely outcome of this is nothing at all; other groups will try to reproduce it, will fail, and the whole thing will be put down to some piece of equipment that was miscalibrated somewhere.

This is an encyclopedia, not a blog. We don't bend with every little breeze. I think there's an essay on WP:RECENTISM.

Now, it would be really really exciting if things come out any other way than the scenario I've outlined. Then at least we could reasonably predict that, even if not ultimately confirmed, the result won't be just forgotten (for example, cold fusion has been mostly debunked, but will not be forgotten), and it would be reasonable for us to cover it. Right now it's not. --Trovatore (talk) 02:23, 23 September 2011 (UTC)

According to Scientific American (http://www.scientificamerican.com/article.cfm?id=particles-found-to-travel), this event has actually occured over 16,000 times already.... Alphius (talk) 02:55, 23 September 2011 (UTC)

Actually, the page on the Scientific American website was technically reprinted from Nature. Alphius (talk) 02:59, 23 September 2011 (UTC)

Original paper: http://arxiv.org/abs/1109.4897 cyclosarin (talk) 03:17, 23 September 2011 (UTC)

The implications are indeed huge, but nothing involving FTL communication, travel or FTL anything. If its a real effect, which is still very much up in the air, its not an invalidation of Lorentz symmetry. See Tachyon page for details.Isocliff (talk) 08:30, 23 September 2011 (UTC)

I think the current balance is about right. We should have a brief mention of what is essentially a news item because it is so directly relevant to the subject of the article and originates from a very reputable laboratory. I think it is right to have it in what is already a section that contains a degree of unverified speculation.

I do not think we should add any more details until the results are verified, neither do I think we should comment on the implications of the results, until they are confirmed. For the moment, it should be clear from the rest of the article that the result would represent a very significant discovery in physics. Martin Hogbin (talk) 08:59, 23 September 2011 (UTC)

I'm not sure about this. Yes Wikipedia is a encyclopedia, but it is not specifically a scientific one. If speculation has been published, Wikipedia should refer to it. 195.194.187.132 (talk) 10:58, 23 September 2011 (UTC)

The problem is not that it's speculation. The problem is that it's too recent. We are not a news source. We should wait until it is clear that this episode will be at least memorable. --Trovatore (talk) 17:46, 23 September 2011 (UTC)

Firstly the paper has not been published, it is just what is known as a preprint, a document open for comment if you will on the arxiv. As for WP:NOTNEWS even if incorrect this announcement and the fact that LNGS/CERN are seeking input on their findings has made the top news on almost every media outlet in the last 36 hours, means it meets criteria for notability for inclusion. To include any statement on this, we must include that the authors of the paper draw no conclusion what so ever on the results, hence the reason they are seeking 3rd opinion so to speak. Regards ^Khukri 20:38, 23 September 2011 (UTC)

36 hours, seriously? Come on. We want to include content that will still be notable in, minimum, ten years. It's reasonable to include breaking events if it's clear that that will be true. For this one it's not. --Trovatore (talk) 20:41, 23 September 2011 (UTC)

Notability isn't temporary WP:NTEMP, to arbitrarily say 10 years is your perception. Hell Pons & Fleischmann is still notable to this day for something not too disimilar, and whether it proves a dud or not is irrelevant, it is not our place to say what may or may not be notable in 10 years. Cheers ^Khukri 20:46, 23 September 2011 (UTC)

We should not cover flashes in the pan; it makes us look non-serious. If this lasts long enough to be comparable with cold fusion, then absolutely we should cover it. The threshold would be considerably less than cold fusion, but substantially more than we've seen so far.

I don't propose ten years as any firm rule, just a way of keeping in mind that we're not a news source. At this point it's reasonably possible that the whole thing will just go away. Until we're reasonably confident that won't happen, we shouldn't cover it. --Trovatore (talk) 20:55, 23 September 2011 (UTC)

I fully agree about flash in the pan, hence I added the qualifier to my first statement, that everyone has gone at extreme lengths to avoid people drawing conclusion on these results. A better way of imagining it is in two parts, one is the media notability, the second is the science itself. We are commenting on the media furore so to speak at the moment, which certainly is worth considering as per notability guidelines, the science itself as you rightly say is along way from being notable in its own right. The two are distinctly different and any inclusion into the article should be written on the fact that is has garnered significant media attention not on the basis that X has happened or conclusions of Y. Cheers ^Khukri 21:02, 23 September 2011 (UTC)

I just think "significant media attention" in the short term is not a metric of encyclopedic notability. What matters is if the attention lasts. --Trovatore (talk) 22:17, 23 September 2011 (UTC)

How about if the attention doesn't last, we just remove the mention from the article? It's certainly something notable that people are coming to wikipedia looking for at the moment, so it should be there--at least for now. — Preceding unsigned comment added by 96.245.204.148 (talk) 19:06, 27 September 2011 (UTC)

Responding a bit belatedly to this comment: It is now clear that the episode is notable and will continue to be. Nevertheless your reasons are wrong. We should absolutely not cover things "at least for now". That's the meaning of WP:NOTNEWS as I interpret it — WE ARE NOT A NEWS SOURCE!!!1!!111!!!. Flashes in the pan should not be covered, even if people are coming to WP to look for them. That's not what we do. --Trovatore (talk) 23:00, 22 November 2011 (UTC)

Those who understand physics may want to check this blog. Proxima Centauri (talk) 18:14, 24 September 2011 (UTC) Disbunked in Feb 2012 as a result of a cable length calculation error. C is still C. Even if originally correct, it is not a significant change.--173.69.135.105 (talk) 01:58, 27 February 2012 (UTC)

OPERA neutrino anomaly: an issue about the discription

"On September 22, 2011, a paper from the OPERA Collaboration indicated detection of 17-GeV and 28-GeV muon neutrinos, sent 730 kilometers (454 miles) from CERN near Geneva, Switzerland to the Gran Sasso National Laboratory in Italy, traveling faster than light by a factor of 2.48×10⁻⁵" Now, there's a problem with the "730 kilometers" part. There is a difference between a place in Switzerland and a place in Italy beeing 730 kilometers in the standard sense and there actually being 730 kilometers between these two points. The problem, any instance of someone saying "this point here is x kilometers away from this point" is incorrectly assuming the Earth is flat", as to say even if someone got a tape measure and measured the distance to the nearist nanometer they would be fundermentally wrong, and would be too high. This is because the Earth is of course round, and moving along the surface of a sphere to get to a point obviously would take more time the cuting straight throught the sphere, like if you have a ball of playdo, draw on it two dots and then measured using a tape measure and then with a straght ruler pushed into the ball of course the ruler would measure the shorter distances.

Obviously neutrinos don't have to dive themselve along the surface to get to their destination, so if CERN near Geneva, Switzerland is 730 kilometers from Gran Sasso National Laboratory in Italy then the neutrinos certainly did NOT travel 730 kilometers.

Also, as the earth is constantly spining and rotating around the run which in turn is spriling around a super black hole in the center of our galaxy, if the Earth happens to be moving and rotating in a way where Italy is moving towards the neutrinos would also have a much shorter distance to travel. Robo37 (talk) 20:03, 22 February 2012 (UTC)

Has been considered on day one after the announcement—and probably even on day minus-fourty. Anyway, see some news about some hardware. - DVdm (talk) 20:14, 22 February 2012 (UTC)

"Daily sky motion"?

Why is the Daily Sky Motion section even in the article? It served no purpose other than to make me wonder if I was missing something in the article, because it is such an absurdly basic concept, and it uses language that is more complicated than the subject matter. It basically says "The earth spins. The universe does not spin around the Earth." (If i were to use the complicated terminology of the article, then the phrase "persistent radial motion" would be used instead of the simple word "spins"). If this truly needs to be explained to the reader, then the article should start with the disclaimer: "This article is written in english, and it discusses the universe as we know it. This article does not explain physics in any parallel or distant universes that may operate under different physical laws." — Preceding unsigned comment added by 72.49.126.191 (talk) 04:08, 2 April 2012 (UTC)

I agree with you that the explanation is unnecessarily complex in this section but it does contain a very important concept of physics that is relevant to the speed of light, and that is the concept of an inertial frame. The rotating frame of the Earth is not inertial and therefore rules about maximum speeds do not apply when measured in that frame.

If you think the section needs simplification why not be bold and have a go at improving it yourself. Martin Hogbin (talk) 08:30, 2 April 2012 (UTC)

Format: Breaking up the article

I suggest separating this page into three pages: one page that discusses FTL travel for objects of mass, one page that discusses FTL information transmission, and one for discusses theoretical natural occurrences of FTL such as the inflation of the Universe, apparent FTL motion of objects from a rotating reference frame, etc. The first two may deal with the proposed methods of created FTL artificially, while the last would deal with natural phenomena and a general description of the physics that would be expanded upon in the first two. The first article may have each of the various proposed methods of FTL as sub sections. I.E. a section on wormholes giving a basic description of what a wormhole is followed by a clear simple treatment of the physics associated with wormholes. This may be followed by a section describing the Alcubierre metric. Perhaps a brief description linking back to the main page for each of these topics? I am not sure how to make such a massive change and would prefer a consensus before trying to do so. — Preceding unsigned comment added by Nfcopier (talk • contribs) 09:46, 23 August 2012 (UTC)

Format: Breaking up the article

I suggest separating this page into three pages: one page that discusses FTL travel for objects of mass, one page that discusses FTL information transmission, and one for discusses theoretical natural occurrences of FTL such as the inflation of the Universe, apparent FTL motion of objects from a rotating reference frame, etc. The first two may deal with the proposed methods of created FTL artificially, while the last would deal with natural phenomena and a general description of the physics that would be expanded upon in the first two. The first article may have each of the various proposed methods of FTL as sub sections. I.E. a section on wormholes giving a basic description of what a wormhole is followed by a clear simple treatment of the physics associated with wormholes. This may be followed by a section describing the Alcubierre metric. Perhaps a brief description linking back to the main page for each of these topics? I am not sure how to make such a massive change and would prefer a consensus before trying to do so. — Preceding unsigned comment added by Nfcopier (talk • contribs) 09:46, 23 August 2012 (UTC)

The article is long and complex. If someone hasn't linked this somewhere, here

http://www.tgdaily.com/space-features/66234-ftl-drive-is-feasible-says-nasa-scientist Someone found out how to make it work mathematically. Are you ready for IPv6? (talk) 10:38, 18 September 2012 (UTC)

I agree - there needs to at least be a discussion of the White-Juday Warp Field Interferometer experiments. 69.85.114.249 (talk) 13:30, 18 September 2012 (UTC)

"Daily sky motion"?

Why is the Daily Sky Motion section even in the article? It served no purpose other than to make me wonder if I was missing something in the article, because it is such an absurdly basic concept, and it uses language that is more complicated than the subject matter. It basically says "The earth spins. The universe does not spin around the Earth." (If i were to use the complicated terminology of the article, then the phrase "persistent radial motion" would be used instead of the simple word "spins"). If this truly needs to be explained to the reader, then the article should start with the disclaimer: "This article is written in english, and it discusses the universe as we know it. This article does not explain physics in any parallel or distant universes that may operate under different physical laws." — Preceding unsigned comment added by 72.49.126.191 (talk) 04:08, 2 April 2012 (UTC)

I agree with you that the explanation is unnecessarily complex in this section but it does contain a very important concept of physics that is relevant to the speed of light, and that is the concept of an inertial frame. The rotating frame of the Earth is not inertial and therefore rules about maximum speeds do not apply when measured in that frame.

If you think the section needs simplification why not be bold and have a go at improving it yourself. Martin Hogbin (talk) 08:30, 2 April 2012 (UTC)

The "Daily motion of the sky" section of the article serves to remind us that the Special relativistic speed restriction is meant to apply only in certain frames of reference, the inertial frames. But there is more to it than that. Consider the converse: if in some frame the speed of an object is greater than c, then that frame cannot be inertial. So we can offer here an argument in favour of Copernicus: the earth cannot be at absolute rest for in that case, the far away stars would have be moving at a speed greater than c. So we would have a relativistic proof that the earth spin is absolute. I suspect Einstein would not be pleased with such a result.

When it comes to General Relativity, there is no demand that only SR inertial frames are legitimate. The speed restriction is also changed. It is no longer required that the speed never be greater than a certain number of meters per second. The restriction now is that no material particle can catch up with a photon and overtake it when both are in a vacuum. No such restriction is violated by the daily motion of the sky and there is no general relativistic argument to the effect that it is absolutely the earth which rotates. Einstein, I believe, would be pleased.

I propose to update the article to include some of these these points and also to make it clear that it is the distance from the rotation axis of the earth that is important in calculating the speed of a star.--- Shanker Pur (talk) 13:19, 10 December 2012 (UTC)

Is the article, as it is today, a bit of a mess?

It is not clear to me which purported examples of FTL motion are meant to be merely apparent and which genuine. According to article's own notion of FTL, FTL is supposed to violate special relativity and create problems with causality. (I quote, "Neither of these phenomena violates special relativity or creates problems with causality, and thus neither qualifies as FTL as described here"). Is there one best genuine example of FTL in the article which violates relativity and causality? — Preceding unsigned comment added by Shanker Pur (talk • contribs) 16:34, 10 December 2012 (UTC)

FTL travel of non-information

I propose that the paragraph be modified to make it clear that genuine FTL involves overtaking a photon. The distinction between having a speed greater than c and a genuine FTL notion needs to be highlighted. The following replacement is a possibility.

Overtaking a photon In an inertial frame, the speed of light in a vacuum is c = 299,792,458 meters per second. But in a non-inertial frames of reference, a rotating frame for instance of reference, a photon can travel at speeds greater than c. Even in an inertial frame, some processes propagate faster than 299,792,458 meters per second but cannot carry information. (See examples below). To have a speed greater than c, however is not the same thing as having a real faster than light, FTL, motion. To be faster than light means to be able to catch up with a photon and overtake it. Overtaking here is to be understood in a local, not a global, sense. A photon may be sent from A to B around a complicated path using mirrors and take longer than a tortoise to complete the whole journey but that is not FTL proper but if at no point does the tortoise catch up with a photon and overtake it, no FTL motion has taken place. One example of proper FTL motion is associated with the phenomenon of Cherenkov radiation when in an inertial frame, light travels at speed c/n through a medium with refractive index, n, but other particles, electrons for instance, travel faster than c/n, {but still slower than a photon in a vacuum in an inertial frame). There is here no violation of Special Relativity or of General Relativity. Nor is there a problem with causality.

In the following examples, certain motions may appear to be faster than light, but they do not convey energy or information faster than light, so they do not violate relativity.Shanker Pur (talk) 10:24, 10 December 2012 (UTC)

As worded, I do not think this is helpful. I don't believe it's very usual to say that a photon can have a "speed greater than c" in a non-inertial frame. (Certainly, the magnitude of the time derivative of its position in some coordinate system can be greater than c, but that's kind of obvious and not very interesting.) The test about "overtaking a photon" does not seem to me to be the main point, as some of the example cases can overtake a photon — for example, a spot of light cast by a distant pointer being moved by its holder can overtake a photon. --Trovatore (talk) 10:31, 10 December 2012 (UTC)

Thank you, Trovatore, for the thought provoking comments above.

1. For an earthbound observer - and most scientists are earthbound - a photon which leaves one distant star to hit another, may have arbitrarily high speeds. Of course, the distant star itself may have an arbitrarily high speed. (In my experience, people - students, teachers, professional astronomers - normally find this an interesting observation!).

2. A laser spot can indeed overtake a photon. This is FTL by my proposed definition but why is that a problem? Certainly, there is no problem for relativity even if this FTL can take place in an inertial frame. No material particle, for any observer, inertial or not, should catch up with and then overtake a photon in a vacuum.---

Shanker Pur (talk) 11:48, 10 December 2012 (UTC)

It's not, of course, a problem for relativity that the spot can overtake the photon. It's a problem for using "overtake a photon" as the demarcation for "real" FTL. I am not sure what you are talking about, in detail, in point 1 — maybe you could say more about that. --Trovatore (talk) 23:23, 10 December 2012 (UTC)

Hello. 1. The stars go around the earth once a day in circles around the sky and those far away from the North-South axis have a rim speed greater than 299792458 m/s. (Note: If we use the symbol "L" to designate 299792458, then the speed 299792458 m/s = 1 Lm/s). Photons, the stars emit in the tangent direction, also have a 'coordinate' speed greater than 1 Lm/s. The point is made in the "Daily motion of the sky" section of the article. When I have pointed out the fact of these great speeds to students, physicists, astronomers, the reaction is of course variable but typically people are intrigued rather than bored. Try it yourself. Of course, the post-Copernican answer, "the earth spins, stupid" can be given but it remains the fact that the naked dictum "Nothing can go faster than the speed of light" (unqualified by any inerial frame clauses) is refuted by the motion of the stars. I expect Copernicus would be chuffed that it has become stupid to adopt a geostationary frame of reference but I think Einstein would not be happy that physics should rule out some frames of reference as illegitimate. One more thing, the speed of the stars is greater than 299792458 m/s but no star ever catches up with a photon and overtake it. The photons are going even faster.

2. The terms "Apparent FTL", "Real FTL" are, I am afraid, beginning to become ambiguous, even multibigous. I have proposed a distinction between "FTc" = having a speed greater than c, which is actualised rather easily, possibly trivially but still interestingly, and "FTL" = being able to overtake a photon. Further definitions are possible. Thus we could have "FTLP" = a particle with non-zero rest mass which can overtake a photon. "FTLS" = a signal which overtakes a photon. The wiki article FTL -- let us label it "FTLwiki"-- demands that motion should violate relativity and causality but does not give a clear instance of such a motion. ----Shanker Pur (talk) 10:25, 11 December 2012 (UTC)

Lights and shadows?

The light spots and shadows example does not make sense to me. Imagine that you have a nossle thou which water can be sprayed. If you turn it on and turn it around at the same time the water will not hit things faster than it moves out of the nossle. To the contrary, the water will hit things slower than that. I think a laser fired to hit targets on an interplanetary or interstellar scale would work in a comparable way.

2014-01-01 Lena Synnerholm, Märsta, Sweden. — Preceding unsigned comment added by 213.114.157.228 (talk) 18:43, 1 January 2014 (UTC)

This is where we discuss the article, not the subject—see wp:talk page guidelines. Please try our wp:reference desk/science. Good luck over there!. - DVdm (talk) 22:58, 1 January 2014 (UTC)

Why wasn't this talked about

Black Holes pull in matter and light energy faster than light implying matter(energy) can be made to move faster than light. "The brightest known quasars devour 1000 solar masses of material every year. The largest known is estimated to consume matter equivalent to 600 Earths per minute." Why hasn't this been talked about in matter or energy being made to move faster than light. — Preceding unsigned comment added by 75.36.244.1 (talk) 04:44, 29 December 2013 (UTC)

Please put new messages at the bottom and sign them with four tildes (~~~~). Thanks.

Because they don't pull in matter and light energy faster than light—see Black hole#Accretion of matter and Accretion disc. You might ask how and why at the wp:Reference desk/Science. Cheers and good luck. - DVdm (talk) 10:56, 29 December 2013 (UTC)

I'm no physicist, but I noticed two things:

1. The source you link above (as modified in this edit) does not mention black holes.
2. The headline of that source says that a light speed "record" has been "smashed", but the "record" referred to is the speed of light in a vacuum and the article itself explains pretty carefully that the observations described rely on propagation through a medium which is not a vacuum. Note that this WP article says, "Light travels at speed c/n when not in a vacuum", n being the refractive index of the medium. Apparently, the caesium vapor used in the experiment apparently has a index of refraction less than 1.0 for some radiation wavelengths. See also Refractive index#Refractive index below 1.

Never trust a headline writer. Wtmitchell (talk) (earlier Boracay Bill) 03:02, 28 January 2014 (UTC)

Why wasn't this article talked about from physicsworld. Light was made to move 300 times the speed of light. This would cause a significant change to the faster than light page. Initial thoughts? http://physicsworld.com/cws/article/news/2000/jul/19/laser-smashes-light-speed-record 06:44, 27 January 2014 (UTC) — Preceding unsigned comment added by 75.36.241.195 (talk • contribs) 12:06, February 6, 2014‎

Please read that Physicsworld article -- not just the headline introducing the article. After you have done that, read my comments above about the article. Never trust a headline writer.

The headline writer for that article seems to be making a comparison involving (metaphorically speaking) Apples (the speed of light in a vacuum) and Watermelons (the speed of light in a gas of caesium atoms in an excited state, wherein refractive index changes rapidly with wavelength). The paper which sparked the Physicsworld article to which you point is titled Gain-assisted superluminal light propagation. The abstract of that paper says, in part, "Einstein's theory of special relativity and the principle of causality imply that the speed of any moving object cannot exceed that of light in a vacuum (c). [...] The observed superluminal light pulse propagation is not at odds with causality, being a direct consequence of classical interference between its different frequency components in an anomalous dispersion region." See [4]. Wtmitchell (talk) (earlier Boracay Bill) 00:26, 7 February 2014 (UTC)

Merge Superluminal communication into FTL page

Because superluminal communication is a subtopic of faster than light, the FTL page seems to encompass almost all the information in the Superluminal communication article in a more comprehensible way. If anything, I think superluminal communication should be a sub-topic within the FTL page. If there's no objection I'll merge after a few months. Kdmeaney (talk) 18:24, 7 April 2014 (UTC)

Moffat, Magueijo et al.

I reverted this edit for the following reasons:

• The work of Albrecht and Magueijo is already summarized and referenced in that section. I'm not against adding further details, but the present addtion is problematic:
• Moffat was not the first to propose a varying speed of light, see the linked article Variable speed of light.
• Albrecht and Magueijo explicitly refer to their work as a phenomenological approach and not as a theory.
• They state that the speed of light in the early universe cold have been more than a factor of 10³⁰ higher than now under certain conditions. They don't treat this as a central result of the paper though, as they mention it neither in the abstract nor in the conclusions.

Regarding the edit summary not vandalism, you should start reading the paper by magueijo instead of thinking it is wrong. i think wikipedia user are quite biased: I doubt that you can convince ClueBot NG to read a paper. I'm not sure what you mean by wikipedia user are quite biased: which user, Cluebot? Or all users, that is including yourself? Or the people who worked on the article so far? If they are biased against inclusion of the work of Albrecht and Magueijo, then how come their paper has been included in the article for the last eight years? — HHHIPPO 19:58, 5 May 2014 (UTC)

Anon ip who made the first edit seems to have changed to another ip to make the same edit. Same location of IPs: 151.230.92.188 and 149.254.181.24. We might need to ask semi-protection of the page. - DVdm (talk) 08:30, 6 May 2014 (UTC)

The first IP made some questionable contributions before, including a 3RR violation within 11 minutes. I would of course prefer if they would join the discussion here rather than edit-warring. Otherwise, RPP it is. — HHHIPPO

with quantum theory we will find that there are speeds faster than light.

that is all. We must now wait for someone to do the experiment that will show this is true and the math for it. once this is done we will find a new math that will work in all areas.The Raven Said: — Preceding unsigned comment added by 73.52.140.224 (talk) 22:39, 13 August 2014 (UTC)

Hi 73.52.140.224 . I confess I don't entirely understand your question. However this is not the place to ask it. Per WP:TALK, this page is for discussing what should appear in the faster-than-light article, not general discussion of speeds faster than light.

Please feel free to ask your question at WP:RD/Science. If possible, you might try to reword it so that it's a little clearer just what you mean. --Trovatore (talk) 22:44, 13 August 2014 (UTC)

It is not a Question it is an answer. There are speeds faster than light. Science knows this but has not proved it yet.

Science never "proves" anything (outside of mathematics) so your statement doesn't make much sense. Jeh (talk) 01:33, 14 August 2014 (UTC)

OK, look, everyone, this is not the place to discuss it. I tried to make that point gently and point to the alternative venue, but it can't happen here. --Trovatore (talk) 02:09, 14 August 2014 (UTC)

Major error in "Faster light (Casimir vacuum and quantum tunnelling)"

Earlier in the page it says, "tunnelling time tends to a constant for large barriers...For large gaps between the prisms the tunnelling time approaches a constant and thus the photons appear to have crossed with a superluminal speed." That is correct. But in the section, "Faster light (Casimir vacuum and quantum tunnelling)" it makes a false statement, "Raymond Y. Chiao was first to measure the quantum tunnelling time, which was found to be between 1.5 to 1.7 times the speed of light." That is completely misunderstood. Furthermore, "time" is a different unit than "speed." The amount of time to cross the barrier approaches a constant, and therefore the net speed increases with barrier distance. So at a certain distance the *effective* speed (if we may call it speed) doubles if you increase the distance by a factor of two. 72.25.65.65 (talk) 14:22, 13 September 2014 (UTC)

Travel vs Communication

Am I the only one who feels that these subjects may better be served with separate articles? They really have a different set of problems and possible solutions. Kortoso (talk) 02:48, 12 December 2014 (UTC)

But they share the same causality paradoxes and logical impossibilities, if special relativity is correct.SBHarris 02:54, 12 December 2014 (UTC)

Variable speed of light section

In this edit, I've removed what looked to me like an unsupported editorial comment added in this 2006 edit to what is now the Variable speed of light section. The removed bit seemed somewhat disparaging.

I'm not a physicist, mathematician, or cosmologist, but it strikes me that this might be related to Inflation (cosmology). Digging around a bit, I found [5] and [6], which might be relevant. I can't claim to really understand this stuff so I'm not going to fiddle with this further. It does strike me, though, that there's a WP:SS disconnect between the content of this section and the Variable speed of light article which it links as {{main}}. Wtmitchell (talk) (earlier Boracay Bill) 05:56, 25 March 2015 (UTC)

Throughout the article it is not always clear which theories are generally accepted and verified and what are speculative, even if they are published in reliable sources. This is an important distinction that should be made in the article. Martin Hogbin (talk) 08:31, 25 March 2015 (UTC)

Variable Speed of Light is not a Theory...

Even the page states that is a HYPOTHESIS! Any kind of change to that section is creationist vandalism, as creationist are the only ones interested in trying to show that statement as "scientific theory" without scientific proof.--FaustoLG (talk) 03:43, 25 March 2015 (UTC)

The article does not say that variable speed of light is a theory. It says that variable speed of light is a postulate in some theories. Theories can be wrong. There is no need to call them hypotheses. Besides, hypotheses don't postulate. Theories do. I have reverted your edit. - DVdm (talk) 12:19, 25 March 2015 (UTC)

Note - I have reverted your personal attack here below. If you find a way to express yourself in a civil manner, feel free to do so. - DVdm (talk) 16:37, 26 March 2015 (UTC)

Phase Velocities above c section

This seems to be pervasive (accidental?)vandalism. The only reference given is to a book and is certainly a personal misinterpretation on the part of the author of this section. This section also refers to the "Phase Velocity" article on wikipedia which in turn cites the "material dispersion in optics" subsection of the Dispersion(optics) article as proof that phase velocity exceeds C in anomalous dispersion, however, the anomalous dispersion article clearly states that anomalous dispersion is a group velocity (multiple frequency) effect.

Any detection of phase velocities above c would be of earth-shattering significance in relativistic physics and the explanation given for how it does not violate relativity is nonsensical. If any phase velocity above c could be produced, modulation of its amplitude would be trivial and therefore information could be transmitted at speeds greater than C.

I believe this section should be deleted and the "phase velocity" article also needs to be repaired. I will institute these repairs in the near future if I receive no valid reason against this action. Nemesis75 (talk) 00:07, 1 April 2015 (UTC)

Hypothesis

How much of this is only in a hypothetical state, and how much has actually been demonstrated in a lab? I don't think this article makes that clear. Kortoso (talk) 20:23, 8 June 2015 (UTC)