Talk:Faster-than-light/Archive 2

section looks like Original Research and non-NPOV

This section is very contentious and appears to be just the personal opinions of the poster:

====Option A.1: Discard special relativity as "primitive"====

In works of science fiction that take place in the future, it is possible to postulate that yet another major scientific revolution has occurred, on the same order as the replacement of Aristotle's theories of motion with Newton's laws of motion, or the acceptance of Darwin's Theory of Evolution. In this view, a new understanding of physics in the future allows superluminal travel to be achieved, and our present-day understanding of the physical universe will be seen as primitive, so that the supposed "impossibility" of FTL-travel is viewed as ignorant superstition on the same order as past beliefs about the "impossibility" of human-controlled fire, human-flight, or supersonic travel. This is sometimes expressed as satire commenting on the fact that at any given time, humans feel certain of many facts that in later centuries or millennia turn out to be utterly baseless, no matter how strong the evidence seemed at the time, such as the theories of alchemy, phrenology, and humors.

An example of a basically prescientific theory being replaced by what would now be considered a genuine scientific one, like Aristotelian "physics" (not based on anything resembling the scientific method) with Newtonian physics, hardly qualifies as evidence that current theories could be completely overturned this way (other examples such as alchemy, phrenology and humors cannot be said to have been based on the scientific method either--their supporters did not come up with rigorous experimental tests which could falsify them). I know of no examples in the history of modern physics where well-accepted theories have been shown to be completely wrong, instead successful theories are replaced when they turn out to be special cases of some broader theory, like the way Newtonian physics can be seen as a special case of special relativity in the limit where the relative speeds of the components of a system are very small compared to the speed of light. It makes sense that new theories would have to incorporate old ones in some way, since widely-accepted theories in physics are always based on large amounts of quantitative experimental evidence, so any new theory has to be able to replicate the old theory's correct predictions about these experiments. It's certainly true of SR that it's based on abundant quantitative evidence--see here for example--and it's hard to see how a new theory could make the same predictions about experiments involving things like energy increasing with velocity or time dilation without actually incorporating SR's formulas on these things (and these formulas say it would take an infinite amount of energy to accelerate something to the speed of light, that clock rates would slow to zero, etc.) None of this is comparable with Aristotelian physics/creationism/alchemy/phrenology/humors, which didn't have great amounts of quantitative predictions which had been verified by experiment.

Also, Wikipedia:No original research says 'The term also applies to any unpublished analysis or synthesis of published material that appears to advance a position', and the section Wikipedia:No original research#Synthesis of published material serving to advance a position elaborates that 'Editors often make the mistake of thinking that if A is published by a reliable source, and B is published by a reliable source, then A and B can be joined together in an article to advance position C. However, this would be an example of a new synthesis of published material serving to advance a position, and as such it would constitute original research.[2] "A and B, therefore C" is acceptable only if a reliable source has published this argument in relation to the topic of the article.' So even if the individual facts about things like Aristotelian physics and phrenology are correct, there needs to be a reliable mainstream source showing that experts agree it's plausible SR might go the way of these ideas in the future, otherwise this would be the editor's own synthesis of published material in order to advance a position.

Unless someone can find some reference to a mainstream scientific source which agrees that SR might plausibly be completely discarded as "ignorant superstition" in the future, I'll delete the section. Hypnosifl 04:47, 28 August 2007 (UTC)

I agree. --Michael C. Price ^talk 19:50, 28 August 2007 (UTC)

I agree whole-heartedly with your reasons for objecting to the inclusion of "Section 1.A", but disagree that these reasons are applicable to what Section 1.A is "trying" to say. Here I think we have an ages-old conflict between author's intent and reader's interpretation, and I would like to resolve said conflict as smoothly as possible. I don't see how Section 1.A makes an "A and B, therefore C" argument, or any argument at all. I don't see how it takes any position or has any POV. Just because a piece of science fiction might propose a future in which belief in the impossibility of FTL-travel has been discarded as "ignorant superstition" does not mean that I, living in the real-world (not a science fiction story), believe that the supposed impossibility of FTL-travel is "ignorant superstition", nor does it mean that this is the position taken by the article. It only means that that's the position taken by a work of science fiction. The film Star Trek V is a good example of this, when it compares and equates people saying that "warp speed could not be achieved" with people's belief that the sound-barrier could not be broken, and with belief in a flat-Earth. I wasn't advancing an argument in Section 1.A, only including a neglected example of how the "problem" of FTL can be circumvented, especially in a work of science fiction. I say "especially" because it isn't difficult to find people in the real world who think that FTL will someday be possible, noting the ever-changing nature of science and the tendency for what is impossible one day to be possible the next, and vice-versa, which is likely what makes this means of circumventing the FTL problem especially popular in science fictions with heavy undertones (or overtones) of social satire, as it observes mankind's constant assumption that the science of the day is always right, and the species' refusal to believe, contrary to what can be seen in our own history, that even the most well-supported scientific belief can and usually will be, given enough time, seen as ludicrous. As far as any other issues with Section 1.A are concerned (such as whether links to alchemy or phrenology should be included, and whether this constitutes POV or original research), I would be happy to discuss them, but I feel very strongly that this section does belong in the article. --Þórrstejn [ˡθoɝ.staɪʲn]: Hammer of Thor ^talk 22:31, 30 August 2007 (UTC)

But the fact that science fiction writers sometimes choose to simply discard SR is already covered in the opening sentence of "Option A: Ignore special relativity", which says "This option is particularly popular in science fiction." To include an elaborate discussion of the reasons someone might have for justifying this option seems too close to endorsing these reasons, especially since the paragraph does not indicate that all these arguments would likely be considered totally misleading by almost everyone with an education in physics. What's more, if you're just trying to give an account of how certain science fiction writers justify discarding SR, you need to actually cite some examples of science fiction writers who use examples like phrenology and alchemy to justify this, otherwise it again seems that you're constructing your own argument rather than giving a neutral description of an argument by published authors. Finally, you do seem to be endorsing the view that these arguments are at least somewhat credible when you say it isn't difficult to find people in the real world who think that FTL will someday be possible, noting the ever-changing nature of science and the tendency for what is impossible one day to be possible the next, and vice-versa, which is likely what makes this means of circumventing the FTL problem especially popular in science fictions with heavy undertones (or overtones) of social satire, as it observes mankind's constant assumption that the science of the day is always right, and the species' refusal to believe, contrary to what can be seen in our own history, that even the most well-supported scientific belief can and usually will be, given enough time, seen as ludicrous. I'd say that the only "people in the real world" who think relativity will be discarded completely (as opposed to those who think that FTL may be possible using loopholes that are consistent with relativity such as wormholes, or that relativity will come to be seen as a limit case of some other theory) are people outside the physics community. And when you say the species' refusal to believe, contrary to what can be seen in our own history, that even the most well-supported scientific belief can and usually will be, given enough time, seen as ludicrous, can you name a single example from "our own history" of a theory of physics that was supported by large amounts of quantitative evidence gathered using the scientific method (which basically means nothing pre-Newtonian) and yet was later discarded as "ludicrous" rather than being seen as a special case of some more accurate theory? Hypnosifl 00:13, 31 August 2007 (UTC)

I agree, Hypnosifl; since this is already covered in the opening sentence of option A, why is it necessary to belabour the point to such an extreme? And I agree that the general tone of A1 is so polemical as to violate WP:NPOV. Possibly the first sentence in option A could be expanded, but that is all that is required. --Michael C. Price ^talk 05:40, 31 August 2007 (UTC)

Are there any objections to completely deleting Option G, the "freezing light" theory? I can't see how it is remotely scientific or encyclopaedic. The idea, while imaginative, is based on flawed premises and a bad analogy...both lava and water are so far below c that any vehicle travelling on them is also way below c. It is possible to travel faster than lava or water without freezing them. Even if light could be frozen, any vehicle would still be incapable or surpassing c. The problem is not the state of the medium, as Krebs surmises, but the limit represented by c. I think the whole thing is silly and would like to remove it, but thought I'd float the idea first here in case anyone has objections.

Krebs Theory

Check out the work of Dr. Lene Hau. In 1999, she led a team from Harvard University who succeeded in slowing a beam of light to about 17 metres per second, and, in 2001, was able to momentarily stop a beam. She was able to achieve this by using a superfluid.

Her experiments fully support the Krebs Theory.—Preceding unsigned comment added by Peanutjake (talk • contribs)

Even if a beam of light could be frozen, you still wouldn't be able to travel on it faster than the speed of light. The state of this individual beam of light and the constant c are not related. If you had some sort of vehicle that could travel on a frozen beam of light, how would you accelerate this vehicle up to the speed of light? Doing so would still require infinite mass. The reason you can travel on frozen lava or water faster than the normal speed of lava or water is because the speeds of lava and water are not universal constants, nor are they relativistic maximums. The "Krebs Theory" is bollocks. —Preceding unsigned comment added by 141.152.22.102 (talk) 19:02, 9 October 2007 (UTC)

Peanutjake - Every time I visit this article, I see your contributions on "Krebs Theory". Each edit evidences your knack for finding casual connections amongst high-level descriptions of various physics theories and articles in Scientific American. Physics, particulary that which deals with the extremes in the universe, can capture the imagination. However, you must appreciate and respect the concept of a theory, even if you do not understand the mathematics behind it. Enjoyment and discussion about your interest in physics belongs here, on the talk page, or on your own personal website, but never in the article. Thank you.

- 99.226.249.109 06:47, 20 October 2007 (UTC)

Is there any math to support your theory, because it truly does appear to be a poorly made false analogy. The freezing of light seems to have more to do with reducing it's diffusion rate not it's actual speed. You also may have more trouble riding a beam of unfrozen light than you will with the lava.—Preceding unsigned comment added by 66.71.29.98 (talk • contribs)

User:Peanutjake has been blocked for three days for disruptive editing. In the hopes that I can make this understandable for when he comes back: his 'theory' is a bunch of words, not a theory and bollocks besides. Now: when you 'slow down' light in a Bose-Einstein condensate, or more prosaically in any medium other than vacuum, that has nothing to do with going faster than c. All the tricks for slowing down light rely on treating it as a wave of a particular frequency and changing the speed of that wave by forcing it to interact with a distribution of free charge carriers structured on the same scale as the wavelength (I am crudely approximating the actual mathematics). So optical light is slowed down by a factor of 1.5 in water, and low-frequency radio waves are slowed down in the ionosphere by factors so high they almost completely reflect. The light-stopping experiments are simply a tour-de-force of exploiting interactions between particles and photons, but they merely stop a particular frequency of wave. Cosmic rays still slice through the material at c. c is the speed of light in vacuum and is not easily altered, to the point that all high-precision measurements rely on it being constant. If Peanutjake's ideas had any validity, he wouldn't be able to use his computer to edit Wikipedia. Michaelbusch 15:57, 20 October 2007 (UTC)

Possibility of FTL... ftl

The first three implications listed do not make any actual sense. They imply that infinity is some sort of number that could be reached, and that is not really what limits and infinity are all about. -Capefeather (talk) 21:00, 16 January 2008 (UTC)

The article says: "Although the theory of special relativity forbids objects to have a relative velocity greater than light speed, " Is that in fact correct? If no reference frame is more special than any other, why isn't another frame, where the velocity would be greater than the speed on light, perfectly valid?

Shouldn't a more correct interpretation be that FROM ONE'S OWN REFERENCE FRAME one can't SEE (or measure) anything having velocity greater than the speed of light?

"general relativity does allow the space between distant objects to expand in such a way that they have a 'recession velocity' which exceeds the speed of light, and it is thought that galaxies which are at a distance of more than about 14 billion light years from us today have a recession velocity which is faster than light.[13] "

Which would mean that in some sense from our frame we can't see or measure them doing that? Or is it worded right that they ARE considered to have a velocity faster than light?

What about galaxies receding from us in opposite directions at speeds, from our viewpoint, near the speed of light? From our reference frame, we can't see either one exceeding the speed of light. But our frame has no special validity. RELATIVE TO EACH OTHER, that is from the reference framework at one galaxy or the other, are they exceeding the speed of light? —Preceding unsigned comment added by DeniseMToronto (talk • contribs) 03:31, 17 August 2008 (UTC)

In other words, is the article worded badly? Correctly? DeniseMToronto (talk) 03:32, 17 August 2008 (UTC)

Not it is not badly written. Just not clear to someone not reading this stuff all the time. FTL travel has been shown to be possible. Gamma rays from pulsars have been detected to arrive before visible light does. The catch is, that from your reference frame you cannot exceed the speed of light. However from another's reference frame, you can been seen exceeding the speed of light. These events have been seen in the expansion of the universe. We may well be traveling near or at the speed of light ourselves, but we cannot tell because of a lack of reference to another that cannot be seen. How it can be done is with a massive dense object that drags the field along with it, creating more inertia. Gamma rays are massive enough for their size to do accomplish this. The problem with humans trying to do this is that they would be crushed from inertia. It seems the only way to get around this is to shield/hide your craft from the universe so you could then violate laws of physics. This is where the TV shows get invented things like "hyperspace" and "subspace." Objects in those areas would not have to comply the laws. Trentc (talk) 06:19, 6 March 2009 (UTC)

I think the part of the problem here is that many people are missing that no one frame of reference is absolutely more valid than any other. It truly is all relative. So no frame from which c would be exceeded is invalid, even though you can't see it. No frame can stop a speed greater than c being true in some other frame. You just can't see that other frame. 216.239.67.64 (talk) 17:22, 25 March 2010 (UTC)

A huge mass is what is seen from one reference point. Me, I don't see that huge mass. So I throw another log of wood into my spaceship's drive, and accelerate just that bit more. The size of my ship seems immense to that distant observer, and the energy from the log might seem insignificant, but that doesn't mean it doesn't accelerate me, so it still accelerates me just a little bit more. I suppose a question is what then happens? Do I seem so immense to that observer that I block out everything at that edge of the universe, maybe the whole universe? Or do I just wink out of view? 216.239.67.64 (talk) 17:22, 25 March 2010 (UTC)

It doesn't matter how many logs of wood you throw into your engine you will never be able to overtake a photon of light in any frame of reference. This has been predicted by GR (or SR, or one of those) and subsequently proven by numerous experiments all over the world. HumphreyW (talk) 22:56, 25 March 2010 (UTC)

So what? My goal isn't to overtake any photon of light. My goal is to go faster than c compared to where I started. Nothing is going to stop me from accelerating. 216.239.82.80 (talk) 02:21, 1 April 2010 (UTC)

Well if you are not overtaking photons of light then how can you say you are going faster then light? HumphreyW (talk) 04:51, 1 April 2010 (UTC)

Because I'm not measuring the speed between me and that photon. Indeed, SR explains that any measurement of the speed between me and that photon will never be found to be greater than c. I'm referring to my speed compared to my starting position. I kept accelerating relative to there, and SR did not and can not stop me from continuing to have accelerated until that velocity logically exceeds c. (And that remains true though I can no longer see my starting point.) That point of view is just as valid as any other because there is no one absolute point of view. It is relative. 216.239.82.80 (talk) 04:35, 2 April 2010 (UTC)

Justifications for FTL travel

I notice options C (give up causality) and D (give up (absolute) relativity) are two options of which at least one is required in order to have any form of FTL, but give no method of doing it, while the other four options are possible ways to go faster than what we consider the speed of light. I suggest putting options C and D in a separate section titled "Implications of FTL travel". — Daniel 00:48, 29 January 2008 (UTC)

Oh, and option A (ignore special relativity) which is a subset of D. — Daniel 00:57, 29 January 2008 (UTC)

To throw in question(ing) of 'Einstein's static theory' or a 'light speed barrier', large quantities of energy leave our sun 'every day of the week' at the 'default' speed of light speed aside from(tachyons). Put another way, this implies the speed of light is an observation that a certain amount of energy travels at or very near light speed. It might be a mis-misunderstanding to teach such concepts as a 'light speed barrier' or 'infinite mass' on the topic of 'faster' than light travel. —Preceding unsigned comment added by 172.131.225.209 (talk) 05:00, 10 November 2008 (UTC)

"Put another way, this implies the speed of light is an observation that a certain amount of energy travels at or very near light speed." The more accurate statement is that no energy has ever been observed to travel faster than light. It is therefore justified to believe that there is a light-speed barrier, especially since that is a crucial part of the theory, and the theory is consistent, and tremendously accurate, well-supported and well-tested. Rotiro (talk) 11:23, 17 November 2008 (UTC)

First looking at relativity it is obviously a colossally powerful theory, however Relativity itself predicts that objects with imaginary mass can or will travel faster than light. I have been interested in FTL physics for years and at higher speeds relativity is still pretty half finished. In General Relativity Einstein defined 'time' as moving at infinite velocity, and as soon as you try to define time or causality as moving at the speed of light Relativity no longer forbids FTL travel at all. In fact studying FTL geometries its rapidly clear that without some kind of hyperspace manifold the universe cannot even exist. Lucien86 (talk) 08:26, 12 August 2009 (UTC)

In fact many of those who claim you can't go faster than c, do indeed talk as if there was some kind of light speed barrier, so it shouldn't be suprising some people have gone on to that conclusion. Yet no one, not even Einsteen, has suggested HOW or WHAT is supposed to stop you from going faster than c. SR is actually about what can be SEEN or MEASURED. I can't SEE you go faster than c. But if you keep accelerating, you keep accelerating. SR has no mechanism, no barrier, to stop you. 216.239.68.212 (talk) —Preceding undated comment added 20:57, 24 March 2010 (UTC).

Removing "Time Integrated With Space"

This seems as if it is trying to be kind of scientific (since it is supposedly "extrapolated from Einstein's theory"), but it appears to be "fringe" or pseudo science (it's self-published and incorporates religious beliefs and UFOs). Further it is not supported by any peer-reviewed citations. One might speculate that the author added it to this page himself, violating the Original Research policy. It reads kind of like an advertisement. Here is the reference I removed: http://4duniverse.blogspot.com/2008/01/new-cosmology-in-4-dimensions.html If on the other hand this is a work of fiction (intentionally or otherwise), well, I don't think this page should become a dumping ground for anybody who comes up with some sci-fi plot device for faster-than-light travel. Even *if* noteability were established, we already have several general categories that can broadly cover most science fiction ideas. Again I emphasize that this page can not and should not be a list of all the imaginative ideas in science fiction about how FTL could fictionally be achieved. Having said that, I feel fairly confident in deleting this section. Any comments ... ? Rotiro (talk) 21:00, 11 February 2008 (UTC)

For guidelines on dealing with pseudoscience, see Wikipedia:Fringe_theories , particularly "Unwarranted promotion of fringe theories" and "Sourcing and attribution". Rotiro (talk) 22:49, 11 February 2008 (UTC)

Space and Time Quantisation

I addressed something that I feel needs to be addressed: the fact that general relativity does not take into account that we have a finite 'smallest space' in this universe, and that could, in fact, be the key to FTL travel. I'm not attempting to rewrite the laws of physics, just to incorporate two very well accepted theories of our universe: Quantum Mechanics and General Relativity. —Preceding unsigned comment added by MaizeAndBlue86 (talk • contribs) 15:48, 23 February 2008 (UTC)

Another "Small correction needed"

From the paragraph: "Under special theory of relativity, a particle (that has mass) with subluminal velocity needs infinite energy to accelerate to the speed of light, although special relativity does not forbid the existence of particles that travel faster than light at all times. (see Tachyon),"

here are two recommendations:

- link to definition of the term "subluminal" should be added (or at least its definition stated)

- "...needs infinite energy to accelerate to [attain?] the speed of light"/ —Preceding unsigned comment added by Twipley (talk • contribs) 13:11, 14 March 2008 (UTC)

Hartmann Effect -- Copyedit Badly Needed

Writing is almost incoherent, needs copyedit by an English-speaking person. How did this article get to B-class? It should probably be reassessed downward. Rep07 (talk) 19:16, 29 March 2008 (UTC)

Citation tag

Some observers with sub-light relative motion will disagree about which occurs first of any two events that are separated by a space-like interval. In other words, any travel that is faster-than-light will be seen as traveling backwards in time in some other, equally valid, frames of reference. Therefore any theory which permits "true" FTL also has to cope with time travel and all its associated paradoxes.

This seems like it needs to be cited as it doesn't make much sense in relation to other parts of the article. Let's imagine that tachyons are real, and transceivers capable of handling them are created. According to this point, if I read it correctly, simply emitting a tachyon means having to answer the Grandfather paradox? The tachyon would seem to allow communication between Earth and its various space probes to be increased (for example decreasing a two hour lag to 1-1.5 hours depending on how much faster than c it actually travels.) How does that change the past? Anynobody 05:10, 19 April 2008 (UTC)

I was merely responding to your request for citation tags, not making an argument for FTL. The paragraph you tagged mentions neither tachyons nor the grandfather paradox so it is unreasonable to require the citation to answer those points. Also, you are doing an awful lot of imagining in that statement . . tachyons are real . . never been proved; . . transceivers capable of handling . . my understanding of tachyons is that even if they do exist it would be impossible to slow them down from FTL and hence observe them.SpinningSpark 10:11, 20 April 2008 (UTC)

Time Travel in Einsteins Universe:The Physical Possibilities of Travel Through Time Page 82 was added as a citation for Therefore any theory which permits "true" FTL also has to cope with time travel and all its associated paradoxes. The problem is the source doesn't say that. It talks about how faster than light travel is impossible but bending spacetime might be. (Which to me still sounds like FTL, if I can beat light going from point A to point B I've traveled faster than light, but I digress) It doesn't mention time travel paradoxes at all unless one considers watching oneself doing something in the past is considered a paradox (that's not meant to be a smart ass comment, I dunno if it is or isn't).

No, that's not right, the citation is verifying . . FTL . . is backwards in time . . which is the claimed fact in the article. The source states . . if you could reach the speed of light, your clocks would stop. And if you could go even faster than the speed of light, then in principle, you could go back in time . . .. This precisely confirms the fact. The second part is hardly a fact that needs citing, it is merely an obvious deduction - if time travel exists then obviously any paradoxes that arise from time travel have to be dealt with. The author is not making a factual claim there that could be disputed and need verifying. Nothing is said (in that section) about what the paradoxes actually are. SpinningSpark 10:11, 20 April 2008 (UTC)

I feel it's also important to note this book is about time travel more than it is going faster than c, an issue which affects the following citation:

Absolutely not. The title of the book makes it clear enough what it is about. The link between time travel and FTL is exactly what the article is discussing and likewise the source. I fail to see a problem. You seem to misunderstand the purpose of inline citations. They are there to confirm the specific fact stated at that point in the article. It is not necessary that the source is exactly the same subject as the article. Only that it is reliable and addresses the fact in question. SpinningSpark 10:11, 20 April 2008 (UTC)

Relativity: The Special and General Theory Page 25 was added as a citation for Some observers with sub-light relative motion will disagree about which occurs first of any two events that are separated by a space-like interval. This appears to be citing a portion of the work where Einstein was talking about time and perception of simultaneous events, which also seems more about time than going faster than c. Anynobody 03:57, 20 April 2008 (UTC)

Yes, but the article says . . sub-light relative motion . . so its reasonable to quote Einstein on this. Also . . which comes first . . is exactly about simultaneity, the reference is precisely appropriate. SpinningSpark 10:11, 20 April 2008 (UTC)

I could also add that this is a very well known (and accepted) consequence of the Lorentz transformation and hardly needed an inline cite in the first place. SpinningSpark 10:19, 20 April 2008 (UTC)

Imporbability

I added a section for improbability drives under justifications. If anyone can add to it, please do. Llama (talk) 14:48, 20 May 2008 (UTC)

Kip Thorne

I may be missing it but why is there no discussion on the main page referencing Kip Thorne? Traversable wormholes and wormholes are mentioned but not a single mention of Thorne. http://www.its.caltech.edu/~kip/scripts/publications.html --aajacksoniv (talk) 14:06, 1 September 2008 (UTC)

Black Hole Escape Velocity

Has any research been done to test weather the escape velocity of a black hole would be FTL? once light is past a black hole's event horizon even light cannot escape, this to me sounds like a black hole's escape velocity is faster than light. This would also conflict with Einstein's idea that light is faster than gravity. Just a thought I had and something I haven't seen discussed.71.112.221.71 (talk) 19:39, 29 September 2008 (UTC)

No research needs to be done: the v_esc for a black hole is indeed FTL. This is by definition; that's why a black hole is black. There's also no conflict, because gravity is now believed to travel at the speed of light, not slower than it -- Fnlfntsyfn (talk) 20:42, 6 June 2009 (UTC)

Of course the problem with black holes is that if gravity is restricted to c then it shouldn't be able to escape the event horizon either, making the black hole appear massless to external space. Of course FTL transfer would also wreak the concept of information not being able to escape black holes. Lucien86 (talk) 07:38, 12 August 2009 (UTC)

Here we actually do have a mechanism to prevent you from going faster than c, but it isn't SR, it's gravitational force. 216.239.68.212 (talk) —Preceding undated comment added 20:59, 24 March 2010 (UTC).

Question

What determines the speed of light? I know it's set to be 299E6 m/s but why is it not faster or slower? Why is it not infinite? 84.193.37.156 (talk) 23:03, 2 November 2008 (UTC)

This page is for discussing improvements to the article and is not the right place for asking questions. You should ask your question at Wikipedia:Reference desk/Science whose volunteers will try to answer any knowledge question. SpinningSpark 23:34, 2 November 2008 (UTC)

It was originally worked out as being c = 299792458 ms^-1, and has now been defined to be exactly that number. As a consequence, the modern definition of a metre is based on the speed of light instead of the other way round: one metre is the distance travelled by a photon in a time interval of 1/c of a second. As far as the number itself is concerned, for some physical problems, the maths becomes easier if you work in units of the speed of light, so you're treating the value of c to be 1 --Fnlfntsyfn (talk) 20:50, 6 June 2009 (UTC)

Copy edit?

The multiple parentheticals in the first paragraph alone make this article difficult to read. Could someone take a hack at rewriting at least the first paragraph to make the article more inviting? Dave (talk) 18:19, 13 November 2008 (UTC)

Nah, just needed reverting back a few days to something sensible. SpinningSpark 12:50, 15 November 2008 (UTC)

Addittional items

I am trying to reduce the 'Faster than light' section in the article 'Speed of light, but I have found some phenomena mentioned on that page not mentioned here so I propose to add them here, possibly with a little reorganising. Martin Hogbin (talk) 14:26, 14 December 2008 (UTC)

Irrelevant

"This is influenced by man-made metamaterials, which allow light to be bent backwards; the discovery of these shattered the now defunct Snell's Law, an old 'law of physics'."

Shattered? Hmm... I don't think that a law that has been experimentally and theoretically verified for hundreds of years on virtually all natural substances can be "shattered"... also I think this is a pretty worthless statement altogether. Delete? --Fusionshrimp (talk) 20:24, 21 January 2009 (UTC)

Yes, it should be deleted. Snell's Law is still taught in physics classes today, so I don't see how it is defunct and shattered. The law still applies in most cases. —Preceding unsigned comment added by 24.113.65.90 (talk) 20:53, 15 February 2009 (UTC)

As far as I know Snell's law is especially relevant for metamaterials. I have been doing research on negative refractive index lately, and snell's law appears to be highly relevant in demonstrating negatve index refraction. With metamaterials, the refracted beam winds up on the opposite of the normal compared to conventional materials. This is based in Snell's law. However, I think this is a good article. It is great how it gives the science of relativity and speed of light, and shows how FTL travel is dubious with our understanding of physics today. Of course I only did a cursory reading of the article.

In addition, I added an image, which I hope is relevant to the article. If it is deemed not relevant then go ahead and delete it. Quinn 01:01, 12 July 2009 (UTC)

Phase velocities above c

This is confusing with what is said in the article about phase velocity: "The phase velocity of electromagnetic radiation may, under certain circumstances, (for example anomalous dispersion) exceed the speed of light in a vacuum". In the current article however, it is said that the phase velocity exceeds that of light in a vacuum "routinely". So what must be cleared out is: Does this occur only under certain circumstances or is it something routinary? How common is it to have waves with large phase velocities? —Preceding unsigned comment added by Avalcarce (talk • contribs) 15:47, 3 August 2009 (UTC)

The two references are consistent (though I can only find the second one in the article). It occurs under special circumstances (x-ray propagation in certain materials, from the article), but these circumstances aren't terribly difficult to set up in a laboratory (and will probably occur in most x-ray tubes that have glass envelopes). --Christopher Thomas (talk) 03:53, 5 August 2009 (UTC)

Updated the entry on Heim. Wikipedia comments that his paper was written in 1977, not 2006. In 2006, another scientist stopped resisting his theory. Heim theory --BenWilson (talk) 00:48, 6 September 2009 (UTC)

A counter-example to GR ?

The article curently claims

"It [General relativity] maintains the principle that no object can accelerate to the speed of light in the reference frame of any coincident observer."

But as observed from Earth in the geostatic reference frame, a space-ship travelling from Earth to the stars would accelerate from subluminal speeds to the speed of light and then to superluminal speeds somewhere between Uranus and Neptune. So is this a counterexample to that General Relativity principle stated here ? --Logicus (talk) 14:16, 26 October 2009 (UTC)

On the apparent counter-example to GR raised by Logicus On a geostatic frame of reference which of course is not an inertial frame of reference, speeds greater than c are not disallowed by SR. Indeed the daily motion of heavenly objects has speeds greater than c. Also the case of comets shows that comets may have speeds which vary from sub to superluminal. GTR does not restrict itself to inertial frames but both SR and GTR disallow the possibility of any runner A overtaking another runner B running alongside A if B is moving at the speed of light c. This prohibition does not apply if A and B are far apart. Nothing can go faster than light locally. Any observer next to, coincident with, a moving photon can not overtake that photon. This is true in SR or GTR. On the other hand both theories have to allow that in a geostatic frame far away things such as the heavens may have a speed faster than c, that such objects eg comets may vary their speed from being less than c to be more than c. In any one neighbourhood, in any locality, nothing can outpace light going at speed c. It is easy to get from one place to another quicker than a photon of light which is made to go in a circuitous path but no where along the path followed by the photon will anything be able to overtake it.Nashpur (talk) 23:46, 26 October 2009 (UTC)

Logicus to Nashpur: Thanks ! But the issue here is whether the example given is a counter-example ‘’to the specific proposition stated’’, which is

“It [General relativity] maintains the principle that no object can accelerate to the speed of light in the reference frame of any coincident observer.”

Is it or isn’t it ?

Your discussion seems to maybe hinge on the meanings of the terms "coincident observer" and "locality" ? What are they ?

If "coincident observer" means one who coincides with the space-ship, then surely the space-ship will appear stationary ?

But if it means ‘in the same frame of reference’, then an Earthbound coincident oberver will see the ship accelerate from subluminal to superluminal speed ?

I propose to double flag the proposition in question, both to request citation of a source for this claim, and also for clarification of the term 'coincident observer'. --Logicus (talk) 18:42, 27 October 2009 (UTC)

Nashpur to Logicus on Faster than light

"Coincident" means having the same spatio=temporal co-ordinates. "To be in the same frame of reference" means being at rest with respect to each other. You and I can be in the same place at the same time and yet not be at rest with respect to each other. According to the theory of relativity,SR or GTR, an object can not have a speed greater than c with respect to a coincident observer.Nashpur (talk) 10:50, 30 October 2009 (UTC)

No serious argument

Lainagier has no serious argument to remove this :

However, the possibility that Lorentz symmetry be violated has been seriously considered in the last two decades, and can be partially tested by ultra-high energy cosmic-ray experiments [5]. If special relativity can cease to be a fundamental symmetry at Planck scale or at some other fundamental scale, it is conceivable that particles with a critical speed different from the speed of light be the ultimate constituents of matter. The superbradyon hypothesis considers the possibility that conventional particles be similar to phonons in a condensed medium (the physical vacuum of our Universe), with a critical speed much smaller than the actual fundamental critical speed.

In current models of Lorentz symmetry violation, the phenomenological parameters are expected to be energy-dependent. Therefore, as widely recognized [6], [7], existing low-energy bounds cannot be applied to high-energy phenomena. Lorentz symmetry violation is expected to become stronger as one gets closer to the fundamental scale.

In what follows, only possibilities of faster-than-light motion basically compatible with standard relativity or with a deformed version of conventional Lorentz symmetry are considered.

([6] is the CERN Courier and [7] a scientific chronicle from The New York Times) —Preceding unsigned comment added by 83.204.164.211 (talk) 03:04, 26 February 2010 (UTC)

I have a serious argument to remove it, and made it in my edit summary. The material in question does not belong in the article's lede. It is an extended, technical discussion of one issue related to the main subject. The lede is there to provide an introduction to the subject as a whole and a basis for more involved discussion like the material in question.

I have no issue with the material itself or its inclusion in the article. It should go lower in the article, alongside material to which it is logically and thematically connected. Putting it in the lede is a poor editorial choice: it disrupts and diminishes the entire article. It also gives the impression of promoting one theoretical viewpoint at the expense of others, which must of course be avoided.

I would urge the author to re-add the material at an appropriate point, with regard for the structure of the article as a whole and the preservation of a neutral point of view. • Lainagier • talk • 03:54, 26 February 2010 (UTC)

I agree with Lainagier. Yesterday I moved the argument under Justifications, but the author undid my edit. I moved it again today. The author can move it to another section if one is deemed more suitable, but I think the mentions about sci-fi which were removed, should stay. -Nistra^Talk 09:46, 26 February 2010 (UTC)

You write :

"Outside of mainstream physics, others have speculated on mechanisms that might allow FTL travel to be achieved, often relying on new conjectures of physics of their own invention, but their ideas have not gained significant acceptance in the physics research community. Fictional depictions of superluminal travel and the mechanisms of achieving it are also a staple of the science fiction genre."

As some other assertions of the article, this is obvioulsy not impartial. It is as ideological as creationism. Einstein himself did not share such a point of wiew, and considered that relativity might be wrong for "submolecular spaces". It is in itself very remarkable that relativity still holds far behind that scale. Modern physics is able to test relativity, at least partially, at energies close to Planck scale. This is an essential point about HIGH-ENERGY PHYSICS, that you systematically ignore.

If relativity does not apply above some fundamental energy scale, but there is physics behind that scale, this physics will most likely be something completely new, including possibly superluminal preons such as superbradyons that would have nothing to do with the kind of "faster that light" you consider. The remarkable point, that you do not like, is that Planck-scale physics can be tested at lower energies. But this is a fact. Even Lee Smolin writes in The Trouble with Physics :

"Remarkably, it took until the mid 1990 for us to realize that we could indeed probe the Planck scale. As sometimes happens, a few people recognized it but were in effect shouted out when they tried to publish their ideas. One was the Spanish physicist Luis Gonzalez-Mestres, of the Centre National de la Recherche Scientifique in Paris..."

The debate on the assertion by Smolin about Gonzalez-Mestres is a subject for other articles, but the Planck physics to be tested explicitly includes relativity. This is widely admitted, and also emphasized by Smolin, just as it was by the Cern Courier or the New York Times a few years before.

(83.199.21.103 (talk) 15:12, 26 February 2010 (UTC))

The lead argument is impartial because it merely states the existence of speculations that aren't widely accepted, and of the sci-fi genre. It does not say that either of these are correct or incorrect. Sci-fi is, after all, not even directly related to actual physics. I am not arguing that what you write is wrong, only that it should be mentioned in a separate section which allows for more detail, and that the article as a whole should be able to present various meanings of the FTL term. You can rewrite parts if you find a way to improve them, but I believe the info about sci-fi is relevant and should not be fully removed, at least. -Nistra^Talk 16:59, 26 February 2010 (UTC)

Steinberg's tunneling analogy

There is a section that states that "Expert Steinberg's tunneling analogy is not correct..." but I don't agree, I think he is correct. I think this section needs to be taken out and vetted before we allow it on here.--Ldussan (talk) 04:14, 21 April 2010 (UTC)

Talk:Alfvén wave-faster than speed of light?

So, alfvén wave is a type of movement that runs faster than speed of light? Newone (talk) 08:00, 12 May 2010 (UTC)

No. 95.178.131.158 (talk) 10:55, 12 May 2010 (UTC)

Indeed. Newone, I believe that Alfven waves travel below the speed of light but there are waves which are superluminal. Martin Hogbin (talk) 14:01, 12 May 2010 (UTC)

Proper Velocity Should Agree With Linked Page

Relative velocity v measured by a remote stationary observer is related to proper velocity v' measured in the moving frame by the well known Lorentz transformation.

v' = v /( 1-v²/c²)

When relative velocity approaches light speed, proper velocity approached infinity.

This is why relative velocity cannot exceed light speed. Proper velocity cannot exceed infinity.

Relative mass approaches infinity for the same reasons, as does the kinetic energy.

Reference: http://www.scientificblogging.com/rational_mystic_amateur_astronomer/blog/star_travelers_guide_stress_testing_light_speed

By stationary observer it is meant an observer who measures the background microwave radiation the same effective temperature in every direction. The traveling frame measures a higher temperature in the forward direction than in the backward direction.

There are theories of Worm Holes, Tachyons, Group Velocities, Phase Velocities, and Quantum Entanglement claiming some concept of faster than light travel. All of them are defective in some way related to the proper velocity approaching infinity.

The only velocity that can exceed light speed is the proper velocity measured in the moving frame. Proper velocity routinely does exceed light speed in particle accelerators of high energy physics. This is a very well known concept of special relativity that is often misunderstood in written explanations. --Astrojed (talk) 23:18, 23 May 2010 (UTC)

Proper Velocity Corrections

The paragraph about proper speed apparently makes an untrue statement and is not in agreement with the link page on Proper Velocity.

"Proper speeds If a spaceship travels to a planet one light year (as measured in the Earth's rest frame) away from Earth at high speed, the time taken to reach that planet could be less than one year as measured by the traveler's clock (although it will always be more than one year as measured by a clock on Earth). The value obtained by dividing the distance traveled, as determined in the Earth's frame, by the time taken, measured by the traveller's clock, is known as a proper speed or a proper velocity. There is no limit on the value of a proper speed as a proper speed does not represent a speed measured in a single inertial frame." A light signal that left the Earth at the same time as the traveler would always get to the destination before the traveler."

All proper measurements are made in the reference frame of the traveler. The preferred way to measure proper speed is the doppler shift in front and behind the traveler measured spectrographically with high precision.

"A light signal that left the Earth at the same time as the traveler would always get to the destination before the traveler."

Special relativity might support this type of claim, but general relativity does not. Curvature of space results from acceleration of the traveler just as curvature results from other acceleration like gravity. Curvature means that space and time are altered in the vicinity of the traveler. So the writer has to specify the path length, and acceleration to decide whether or not the light signal arrives. Dilation shortens the distance as measured by the traveler, so special relativity may also have objections to the claim, if the traveler is going by a route that is effectively shortened by dilation. --Astrojed (talk) 23:18, 23 May 2010 (UTC)

Rethink Astronomy And The Universe

Essay archived per WP:NOR and WP:SOAPBOX.
The following discussion has been closed. Please do not modify it.
even without Quantum Unique Ergodicity, but with plain commonsense Galactic clusters formed by dispersion, not by conglomeration. The proof of this is their behaviour as Newtonian bodies (including acceleration). These bodies formed at the start of inflation, when all energy was still in mass format, and the inflation was the start of reconverting the mass into energy. Rethink - A Basic Physics Tenet - The Universe In Which We Live A. Neutrino quick-change artist caught in the act A transformation from one ‘flavor’ to another confirms the elusive elementary particles have mass and suggests a need for new physics. http://www.sciencenews.org/view/generic/id/59825/title/Neutrino_quick-change_artist_caught_in_the_act B. Adopt - Each and every particle has mass. - Dark energy and matter YOK. - Higgs field/particle YOK. - Do not be afraid of embarrassingly obvious answers. Adopt space-distance in lieu of space-time. C. And Rethink The Universe By the presently available data our universe is a dual-cycle array. One cycle, the present, started from singularity, with all cosmic energy in mass format, and it has been proceeding to reconvert all the mass resolved at the big bang back to energy, by expanding the cosmos, by accelerating away the galaxy clusters. The other cycle, the cycle that led to singularity, will re-start when the expanding cosmos consumes most or all mass that fuels the expansion. Gravity will then initiate reconversion of all the energy back to mass, to singularity, again. Dov Henis (Comments From The 22nd Century) Cosmic Evolution Simplified http://www.the-scientist.com/community/posts/list/240/122.page#4427 Gravity Is The Monotheism Of The Cosmos http://www.the-scientist.com/community/posts/list/260/122.page#4887 EOTOE.Embarrassingly obvious expanding horizons beyond Darwin And Einstein. http://www.molecularfossils.com/2010/05/formal-test-of-theory-of-universal.html Dov Henis (talk) 18:51, 23 August 2010 (UTC)

What are you trying to say here? Is appears to be a definite case of COI, I hope you don't intent to place it in the article. HumphreyW (talk) 19:02, 23 August 2010 (UTC)

Casimir Effect

There's a brief description of the Casimir effect in the article, with no references, no explanation, and apparently no reference to FTL. Either this needs explaining or removing?188.222.111.180 (talk) 22:33, 11 June 2010 (UTC)

Superficial FTL

I've removed the word "superficial" as it appears meaningless. In what sense are any of the phenomena superficial?

The recession of galaxies from each other, for example, would seem to be a rather major, perhaps important thing.

LASER SPOTS AND SHADOWS ---- As for laser spots and shadows, no justification is given for saying that no matter or information can be transmitted. I have left it in, for now, but that saying seems questionable. —Preceding unsigned comment added by DeniseMToronto (talk • contribs) 06:21, 18 December 2008 (UTC)

The cited reference seem fairly clear on the matter to me. Martin Hogbin (talk) 22:22, 18 December 2008 (UTC)

Martin, I've read the cited article. I agree with you about shadows, for I think the shadow doesn't exist until the light arrives at the distant location. I didn't see an explanation of how laser spots can supposedly go FTL. DeniseMToronto (talk) 08:58, 30 January 2009 (UTC) While I THINK the assertion is actually correct, what if it isn't just a spot or shadow, but the image of a word or two such as "Oh, yeah?" Or even with a spot, it could convey different information depending which clouds it is upon? 216.239.67.64 (talk) 17:09, 25 March 2010 (UTC)

They both can go FTL because each is the absence of the other. 86.133.179.19 (talk) 22:20, 30 January 2009 (UTC)

The supposed belief in ability to make laser spots go FTL at a distance is in fact erroneous. Laser beams only look straight over a short length. If we were to sweep a beam across space, and could see the whole beam, we would see it bend, in a similar way to the jet from a hose if one spins around while holding it.82.6.1.85 (talk) 22:11, 18 February 2010 (UTC)Lance Tyrell

CLOSING SPEEDS But the framework of the hypothetical observer moving along with the particle is NO MORE VALID than that of the observer at rest. If FTL isn't possible, the observer at rest isn't supposed to be able to detect that the two particles are moving so fast relative to each other. That's not supposed to be possible. This would indeed seem to be a case of FTL. DeniseMToronto (talk) 08:53, 30 January 2009 (UTC)

I do not understand what you mean. 86.133.179.19 (talk) 22:20, 30 January 2009 (UTC)

Well, as I understand the article, it is saying that even though the two particles appear to be travelling at greater than the speed of light relative to each other, they aren't doing that because there is a framework from which they don't appear to be doing that. This however would require some greater validity to THAT framework. And it is part of our assertions that no framework is any more valid than any other. So the framework where the two particles are seen to be going greater than the speed of light relative to each other, is equally valid. DeniseMToronto (talk) 06:46, 31 January 2009 (UTC)

Special relativity says that no information or matter can travel faster than c as measured in an inertial frame. This does not prevent two objects from travelling at close to c (as measured in some particular inertial frame) in opposite directions. This means that they would be getting further apart or closer together at nearly 2c, as measured in that same frame, even though each object is travelling at less than c. When you transform to the frame of one of the objects you need to use the special relativity velocity-addition formula, which show that the other object will still be moving at less than c as measured in the new frame. Martin Hogbin (talk) 14:14, 31 January 2009 (UTC)

But even you see there's a frame where they are going at nearly 2c. That frame is just as valid as any other, and in it you just agreed they are going at faster than c. I don't have to transform to any other frame, I'll use that frame. DeniseMToronto (talk) 09:29, 3 February 2009 (UTC)

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)

UNIVERSAL EXPANSION The article says "The expansion of the universe causes distant galaxies to recede from us faster than the speed of light, if comoving distance and cosmological time are usVelocity-addition formulaed to calculate the speeds of these galaxies." In other words, they ARE moving FTL.

"However, in general relativity, velocity is a local notion, so velocity calculated using comoving coordinates does not have any simple relation to velocity calculated locally.[22]" But that local framework has no special validity over any other. This seems like a rather bright attempt to try to say well yes, FTL IS possible but they aren't really FTL.

"Rules that apply to relative velocities in special relativity, such as the rule that relative velocities cannot increase past the speed of light, do not apply to relative velocities in comoving coordinates, which are often described in terms of the `expansion of space' between galaxies." In other words, well, yes, it IS FTL and not prohibited.

I think, though cleverly worded to try to sound otherwise, this amounts to an admission that FTL does exist and is possible. DeniseMToronto (talk) 09:08, 30 January 2009 (UTC)

Maybe we should say more about what FTL means. 86.133.179.19 (talk) 22:20, 30 January 2009 (UTC)

The laser spot is a classic - yes it can move faster than light though its very difficult to achieve it. It doesn't actually mean anything because there is no transfer of information faster than light. The information making up the spot comes from a ray and its final position is only dependent on the vector direction of the beam at its start which allows any level of multiplication.

The same thing with the fulcrum on the receiving end allows us to see FTL coherence across stellar objects light years across or whole galaxies or even between distant galaxies. In fact there is even coherence observed within the general interstellar background at the edge of the universe which would require speeds on the order of ???(how big was the universe then?) .. Ultimately we can guess that large scale coherence probably extends to simultaneity, but again no information anywhere is actually being transmitted faster than light. The universe is full of observable FTL coherence but it can all be explained by STL physics over eons of time. It does suggest that empty space is a pretty stable coherent place maybe implying that something like a hyperspace or 'aether' is needed somewhere... but then the extreme constancy of c in vacuum probably takes care of that to. Hope that helps. Lucien86 (talk) 10:08, 26 April 2010 (UTC)

If I shine the laser spot, I'm telling you it is night where I am. If I don't shine the laser spot, it is daytime. I know we keep saying no information is transmitted, but that's because we're assuming it is a meaningless spot. There is no reason to assume that. We don't at all know that no information is being transmitted. 216.239.77.231 (talk) 07:08, 5 November 2010 (UTC)

MISUNDERSTANDING

Several people keep referring to SR as if it was a mechanism, action, or some other thing that prevents, precludes, prohibits, or otherwise does something to stop acceleration to greater than c.

It simply does not.

SR is an explanation of how the universe is, and of what can be seen or detected.

It doesn't STOP anything. It explains why you can't SEE some things.

99.233.164.50 (talk) 19:08, 1 April 2010 (UTC)

Please provide references that support this. PDCook (talk) 19:18, 1 April 2010 (UTC)

VANDALS KEEP REVERTING THE ARTICLE to SR being some kind of mechanism or process like a big hand stopping a spaceship. SR is a theory and explanation that has been experimentally tested and verified many times. It is not some THING that precludes or prohibts anything other than what can be SEEN or DETECTED. People who have that misunderstanding keep vandalising the article, often without even bothering to attempt to explain themselves. 216.239.82.80 (talk) —Preceding undated comment added 04:39, 2 April 2010 (UTC).

Reference that it does NOT do some thing? Please give references that show that SR has some mechanism of action! That it puts a hand out and stops acceleration that gets near to exceeding c. Or that it has some process that slows acceleration down. Actually, my references are right here. People who THINK SR stops, precludes, or prohibits something are right there in the article. SR is an EXPLANATION, one that has been experimentally tested and verified for its validity many times. The article itself is a reference for what I'm saying, for it gives examples of people accepting a speed greater than c, but saying well that's only "proper speed", or admitting there's a perspective where the speed of c is exceeded, but saying only the perspective of the co-moving particle counts. Ironically one aspect of relativity is precisely relativity. No one perspective is absolute. That's part of what relativity is about. 216.239.82.80 (talk) 04:15, 2 April 2010 (UTC)

Well now that you've seemed to figure out how to use talk pages and not edit war in the main article, perhaps a discussion on this issue can take place. PDCook (talk) 04:48, 2 April 2010 (UTC)

Thanks. I'm trying. And I appreciate your thoughtfulness. Though I admit to some frustration that quite a number of other people didn't use the discussion pages at all. At least I started with the discussion page. ... The term "observable universe", by the way, is precisely based on the fact that we can't see parts of the universe where light would have to travel faster than c for us to see it. That there is an "observable universe" and a universe we can't see, is EXPLAINED by Special Relativity. It's an explanation. No one really assumes the universe we can't see doesn't have any existence or that it is destroyed. We can logically infer that those stars are there and are real, and that from another place in the universe they are observable, because from that other place they could be seen without light having to travel faster than c. 216.239.82.80 (talk) 05:04, 2 April 2010 (UTC)

Thanks for your efforts to improve the article. Wikipedia doesn't allow original research, including original synthesis of published material. What in the article are you actually proposing be changed, and what would you change it to? Please point to a published scientific journal, or other reliable source(s) to back up your changes as well. —Joshua Scott (LiberalFascist) talk 14:00, 2 April 2010 (UTC)

Thank you Joshua, but I have done no original research. There was a guy who figured out Special Relativity, a kinda bright guy, and you might have heard of him: Einstein.

I'm sure you can find his theories somewhere. If such references are so important to you, then find a few. As for the misunderstanding, examples of the misunderstanding are in the article itself. And are embodies in the people who keep reverting the material to reflect the misunderstanding, talking as if SR was some kind of force that slams things to a stop or holds them back. I think you mean well, but really! And, BTW, you can easily find that SR has been experimentally verified many times. Missing a reference? Add one yourself if you disagree with SR. 216.239.82.80 (talk) 16:09, 2 April 2010 (UTC)

I have added to the article an explanation of how Special Relativity is often misunderstood. If you have problem with that, discuss it here. Maybe it can be improved from my writing! Indeed, add references if references are important to you. Don't just revert the article back because you've often heard it said the SR "prohibits, precludes, does not allow" etc. etc. If you think SR prohibits, for example, receeding galaxies from ending up faster than c relative to us, explain why. Explain what SR does to those galaxies to stop them. And so on. Make a constructive contribution. Or go back and read what Special Relativity really is. And add a reference if you want. And not merely to one that says faster than c isn't possible, but one that explains why it isn't actually that you can't see faster than c. 216.239.82.80 (talk) 16:31, 2 April 2010 (UTC)

Sarcasm won't help discussion of potential changes to the article. Per WP:BURDEN, the burden of proof lies with the editor who wishes to add material to the article. Please stop adding your commentary into the article. If you want to make a change, discuss it here, or provide a reliable source. Thanks. —Joshua Scott (LiberalFascist) talk 16:37, 2 April 2010 (UTC)

I don't particularly like sarcasm, but it can be a tool to help make something clear. The fact is that I made constructive contributions to the article, and OTHERS EDIT WARRED by reverting things back, without any explanation or discussion. THEY did the warring even if I wasn't the best with my etiquette. 216.239.77.231 (talk) 07:45, 5 November 2010 (UTC)

OK, I am by no means a physicist, so bear with me. I think the issue here is not SR, but the interpretation of it, and putting it into layman terms suitable for a WP article. If SR does not set a cosmic speed limit, then surely there are books or scientific literature out there that use language similar to yours. Those who are opposing 216.239.82.80 can point to their sources to refute the changes. I will say this, 216.239.82.80, you should really try to learn Wikipedia customs and etiquette before making major changes to this article and edit warring. These actions can get you blocked. PDCook (talk) 16:42, 2 April 2010 (UTC)

THEY DID THE WARRING. I gave reasons and explanations. They did not. For that matter, though they could easily have found citations giving the same misunderstanding as the article has, they didn't even do that. (Though no one seems to care that they didn't do that. That standard was only thrown at me.) 216.239.77.231 (talk) 07:45, 5 November 2010 (UTC)

I should echo Joshua's point that the normal process for making major changes to an article is not shouting at people and using sarcasm. Instead, we typically bring to the attention of our fellow editors reliable sources that demonstrate the point we are trying to make. Then the point is discussed and if consensus is that a change should be made, the change is made. PDCook (talk) 16:48, 2 April 2010 (UTC)

That is not what I started with. And I guess no change will be made, since the points I made are simply being ignored rather than being considered. Don't consider it, then you'll never have a consensus. 216.239.77.231 (talk) 07:45, 5 November 2010 (UTC)

Ok, I understand where you're coming from, but most people are NOT discussing and did NOT discuss the points here. And I would clearly welcome discussion of that. I've said that more than once. What is happening is just reversion. That has NOT been constructive. That's the exactly the edit warring, being done to me, that we all agree is wrong. And if I'm shouting, sorry, but it is still true. Heck, I even at one point directed people to the discussion page so they could see others disagree with me and could contribute whether agreeing or disagreeing with me. That's probably technically against the rules too, but at least I was trying to be constructive. So, yes, out of frustration, some of my writing here sounds sarcastic. Though it is meant more to be a challenge. Post references which say SR is not an explanation of what we can observe, but shows SR is a real mechanism, a real force that stops acceleration before it exceeds c. Don't just post a repeat of the misunderstanding --- which is indeed easy to find. Though no one is even doing that. OK, it is too much. Now I'm in effect blocking myself. I wanted to improve the article. I cared. I gave REASONS for what I posted that have to do with the points involved. THAT was pretty much ignored. Apparently I'm "sad and pathetic". Ok, that's the point of view of the people here. You're all entitled to think what you want. 216.239.82.80 (talk) 17:07, 2 April 2010 (UTC)

216.239.82.80 - To be clear, I have absolutely no problem with changing this article to provide more accurate information. Since I'm not a physicist, and neither are the vast majority of editors or readers, there need to be sources that say the same thing you are saying, or we have no way of knowing if it is accurate. Please read this policy - The threshold for inclusion in Wikipedia is verifiability, not truth. I would like to work with you on this, but you are violating WP:3RR. You may be blocked for these reverts, per policy, but I hope that you will discuss and provide sources for your changes, and we can improve the article (which is by no means perfect).

One other thing, don't sign your contributions in articles with ~~~~. Only on talk pages. Thanks, —Joshua Scott (LiberalFascist) talk 17:15, 2 April 2010 (UTC)

I was getting complaints before about my not using the four tildes! Aargh! I'm putting them here anyway, as otherwise I'm sure I'll be accused of trying to hide who posted this! 216.239.82.80 (talk) 18:43, 2 April 2010 (UTC)

Tildes in talk pages; no tildes in articles. PDCook (talk) 18:57, 2 April 2010 (UTC)

BTW, just for interest, see the Wikipedia article on the Heisenberg Uncertainy Principle. Right in the article it covers the issue of what the uncertainty principle means and possible misunderstanding/confusion of the uncertainty principle with an observer effect. One could quibble here and there, but I think they did that fairly well. That is an example, at least, if not a precedent, for a main article discussing the way something is misunderstood. 216.239.82.80 (talk) 19:15, 2 April 2010 (UTC)

There is still the necessity to show, from reliable sources, that such misunderstandings have happened. Remember that you can't simply just make stuff up, you have to properly cite your sources to have a better chance of having any major changes to the article accepted. HumphreyW (talk) 19:23, 2 April 2010 (UTC)

I didn't make stuff up. I referred to points in the article and showed the problem with them. The problem with them, which is not the same as a problem with SR. SR has been well verified. 216.239.77.231 (talk) 07:45, 5 November 2010 (UTC)

The view being put forward by 216.239.82.80 (or the original IP poster) is the view of mainstream physics. Physics, and indeed all science, is descriptive not prescriptive. Physicists do not purport to know how or by what mechanism the word works, they simply try to produce increasingly accurate and useful descriptions of nature. Martin Hogbin (talk) 11:04, 3 April 2010 (UTC)

I think we would be supportive of changing the wording, if references are shown and it is discussed here. The reason the IP user's contributions were reverted is because s/he added what looked like commentary to the article with these edits. This was a newbie mistake, but the user didn't follow the advice of other editors and preceded to edit war, which essentially turned a potential useful addition into vandalism. Nonetheless, this discussion needs to be based on references. PDCook (talk) 13:50, 3 April 2010 (UTC)

No, the contributions were reverted without explanation, without discussion, without talk, even (oh my!) without citations. They did the edit warring. They did the vandalism. Yet I was blamed. 216.239.77.231 (talk) 07:45, 5 November 2010 (UTC)

Yes, I was on of those who reverted the changes to the article and suggested discussion here. I completely agree that the article is not the place for discussion of these issues, however, it should reflect the mainstream view on such matters.

Perhaps 216.239.82.80 could explain in what way the current article is wrong or badly worded and how they propose to improve it. Martin Hogbin (talk) 14:36, 3 April 2010 (UTC)

The IP editor has been banned for 48 hours for violating WP:3RR, so unfortunately he can't articulate the changes he wants to make here. I agree with PDCook, though, I would absolutely have no problem with improving this article. I do have a problem with adding unreferenced commentary to an article that's already tagged with {{refimprove}}. I believe User:216.239.82.80 wanted to add something to the article stating that most people do not understand SR, which, if true, should be easy to provide a source for. —Joshua Scott (LiberalFascist) talk 00:02, 4 April 2010 (UTC)

I did articulate. I did explain. I gave reasons. It was the other people who simply reverted things without discussion, without explanation, even without citations, and ignoring my REQUEST for discussion. They warred, yet I was banned. The article itself, as I have pointed out AND EXPLAINED is itself an example of some of the misunderstandings. "SR prohibits"? Nope, SR explains. 216.239.77.231 (talk) 08:05, 5 November 2010 (UTC)

Let us wait and see what 216.239.82.80 says. Martin Hogbin (talk)

I'm on a different IP but waiting on wikipedia to do the right thing. 216.239.88.76 (talk) 06:51, 6 April 2010 (UTC) also known as 216.239.82.80

It is not a good idea to try to evade a block by using a different IP. As I suggest on my talk page, why not register and then wait for the block to be lifted (I believe it was for 48 hours). Martin Hogbin (talk) 09:14, 6 April 2010 (UTC)

All I'm doing is waiting for wikipedia to do the right thing. 216.239.88.76 (talk) 10:18, 6 April 2010 (UTC)

I am trying to help you. There is no real downside to registering, you do not have to use your real name and you have no commitment. In any case WP should lift your block in 48 hours. Martin Hogbin (talk) 11:09, 6 April 2010 (UTC)

Nothing from wikipedia. Guess I just have to give up. 216.239.79.180 (talk) 08:39, 12 April 2010 (UTC) aka 216.239.82.80

Your ban was for 48 hours so I would presume that it has been lifted by now. I would still urge you to register, but in any case I would suggest that you start discussing the problems you see with this article here. Martin Hogbin (talk) 10:48, 12 April 2010 (UTC)

It seems complicated. I appealed the ban given that I did use the discussion page while others didn't, and because it was the others who weren't constructive. Wikipedia hasn't contested the truth of that. But the ban was kept. I've appealed two more times. 216.239.79.180 (talk) 09:32, 13 April 2010 (UTC) aka 216.239.82.80

I NOTE THAT THOUGH I TRIED TO BE CONSTRUCTIVE, GAVE EXPLANATIONS, ETC., WIKIPEDIA SIMPLY BANNED ME. OTHERS DID THE REVERSIONS, WITHOUT EXPLANATION, AND OTHERS DID THE WARRING, YET THE WIKIPEDIA AUTHORITIES UNFAIRLY BANNED ME. I HAVE NOTED THAT A NUMBER OF POINTS I'VE MADE HAVE SIMPLY NOT BEEN REFUTED. THIS ARTICLE ITSELF SHOWS THAT SR IS OFTEN MISINTERPRETED AS A THING THAT PROHIBITS OR DOES SOMETHING, INSTEAD OF BEING A VERY GOOD EXPLANATION OF WHAT CAN BE SEEN OR MEASURED. Don't like sarcasm? Don't like yelling? Neither do I. But I've tried very hard to make it clear that I'm not saying anything new or original. Want a citation? Go back to Einstein himself. What SR really says. It does not say there is a big stop sign in the sky. I've given explanations. Reasons. That people have NOT countered. Am I frustrated by unthinking responses? By being unfairly banned because people can't actually justify what they've said? Yes. Am I being impolite? Not following the rules? OK, but my citation is still SR itself. Not the misunderstanding of it that is all too common and is presented in the article. Don't like that? You can continue to ignore... you've been doing it quite well so far ... Ban me again, just as unfairly. I TRIED BEING REASONABLE AND CONSTRUCTIVE AND GOT NOWHERE WITH THAT APPROACH. 216.239.77.231 (talk) 07:26, 5 November 2010 (UTC)

I assume I'm banned again. They did it unfairly before, so I'm sure they'll do it unfairly again. 216.239.77.231 (talk) 07:49, 5 November 2010 (UTC)

request for an example

Hi, in the article it is mentioned several times that, "Faster-than-light communication is, by Einstein's theory of relativity, equivalent to time travel. " or similar claims. Could an example appear somewhere in the text, it might help readers understand what is meant by this. 0¹⁸ (talk) 18:55, 14 September 2010 (UTC)

The basic idea is that something that looks like time travel in one inertial frame (i.e., to an observer moving in one direction) can look like FTL travel to an observer in a different frame (moving in another direction), and vice versa. I made an animated .gif illustrating one situation like this a while back; it's here. --Christopher Thomas (talk) 03:11, 15 September 2010 (UTC)

Hmm, is there a text writeup of what is going on in the figure? I see the one in the bottom, but something like, "a motorcycle moving at 2 c then..." I was also suggesting that something be placed in the article, not here. 0¹⁸ (talk) 04:02, 15 September 2010 (UTC)

The animation has text at the bottom explaining what's happening in each step. It was just a proof-of-concept animation, so that's all there is for it. I suggest reading through special relativity and some of its linked pages for examples of the sort of thing the figure shows, and an explanation of the Lorentz transformation in general (the relation between what an observer in one frame calls "space" and "time" and what an observer in a different frame calls "space" and "time"). --Christopher Thomas (talk) 05:48, 15 September 2010 (UTC)

Again, I'm not actually looking for the information, I'm saying that the article as it is written would benefit greatly from an example. I think the article reads great if you already understand all this stuff, but if you don't it reads like there are several places where it says, "you know what I mean." Which is one of the hallmarks of poor writing. If the reader doesn't know... then they still don't know. If they did know, then why write it down in the first place. The article looks useful for refreshing someone's memory, but not for making the concepts clear. I'm suggesting a way to improve it. I would edit it myself, but I don't think I understand the concepts well enough. 0¹⁸ (talk) 14:37, 15 September 2010 (UTC)

I unfortunately don't have the time to make a proper editing pass myself, but I'll drop a note at WT:PHYS in case someone else does. --Christopher Thomas (talk) 17:35, 15 September 2010 (UTC)

It's important to remember that using FLT to send information back in time is necessarily a two-step process. Sure, in one step you can send information back in time according to the coordinate system of some frame, but so what? It's at an event point with spacelike separation from the origin; you can't get it back to the original location using slower-than-light travel.

So you have to do the trick in two different frames.

Some details at tachyonic antitelephone. --Trovatore (talk) 18:54, 15 September 2010 (UTC)

This article really containes a lot of information, it is really hard to read. Also the point on time travel is somewhat miss-leading since it always implies traveling BACKWARD in time (since we all anyway are travelling forward in time). But to construct an example, that is not wrong or inconsistent in one or the other point is quite hard. I will try to make a very simple example, but as I'm not an expert in GR/SR things I'm not sure, if sth. like this could be right or if I'm leaving out important points:

Two persons are standing side by side. One is waving its hand from the left to the right. when its at some point on the right, the second person is instantanously accelerating to speed of light, thus flying with the signal "hand on the right", thus not seeing the hand moving, thus "not traveling in time" (neither forward nor backward), if this person accelerates again to FTL and looks back to his friend, he will see waving the hand from the right to the left, since he "see's" the signal in reverse order. If he stops again a does not move relative to his friend he will see him waving his hand again from left to right. Thus he traveled (backwards) in time

is this a possibility or is this over-simplifying?? RolteVolte (talk) 19:17, 15 September 2010 (UTC)

I think you're confusing visual appearance with what happens in a frame's coordinate system (which, as I explain above, is still one step removed from time travel).

This is a mistake that lots of people have made; you can find plenty of literature claiming that fast-moving (but slower than light) objects will "appear" to be shortened in the direction of motion. That isn't exactly true. They actually "appear" (visually) to be rotated, more or less. It has to do with photons from the far side of the object encountering/not-encountering different parts of the object on their way to you, because of the movement of the object in the mean time.

If I've understood it, your "waving" example is along those lines. That's not what is meant here. --Trovatore (talk) 19:24, 15 September 2010 (UTC)

Yes, that's true. I only thought about the measuring of a signal that is sent out at some time.. SR is a hard task.. ;)RolteVolte (talk) 19:35, 15 September 2010 (UTC)

I think it goes something like this. I am on a rocket going 0.9c on a vector pointing away from earth. When I reach distance d, I turn around and receive a signal from a person standing on Earth of either "1", or "2". It happens to be a "1". This means that I'm supposed to flip lever 1. When I do this it makes me move faster than the speed of light (in my reference frame in which I am stationary) to another point on the opposite side of Earth... I am now traveling back towards earth at a speed of 0.9c. This wasn't what I hoped for. I apply thrust on the ship until it is not moving relative to Earth. Now, I share a reference frame with Earth and am in the past, relative to the Earth reference frame that sent me the signal, however any signal that I send from here would arrive at Earth after the signal of "1" was sent. Miffed about ending up at the same distance from earth despite having traveled quite a ways I now reprogram the machine that moves me faster than the speed of light to send me back to Earth. When I arrive, I tell the person standing on earth giving the signal to hold up a "2", which is now the signal that I will receive before I hit lever "1" or "2" and started this whole silly story...

What I don't get is why space and time axes do not remain orthogonal in the Earth reference frame when I am moving away from Earth at 0.9 c. 0¹⁸ (talk) 20:27, 15 September 2010 (UTC)

That is due to the Lorentz transformation. It's just the way that coordinates in Minkowski space work. As with the animated .gif I linked above, if you're moving with respect to an observer, the observer sees your "space" and "time" axes tilted towards one of the light-cone edges (a light-like path in your direction of travel). From your point of view, your own axes are orthogonal but the observer's are tilted towards the light-like path in their direction of travel relative to you.

The interpretation of tilting the "time" axis is straightforward: what you interpret as standing in one spot and moving forward in time, the observer will interpret as you moving forward in both space and time. The bit that most people don't expect is for the "space" axis to change as well: what you would interpret as teleporting forward or backward along your direction of travel (moving through space in zero time), the observer would interpret as you moving in both space and time (forward or backward, respectively). --Christopher Thomas (talk) 21:41, 15 September 2010 (UTC)

Christopher Thomas, is there a direction one can move in that is still orthogonal to time? i.e. if I move in the plane orthogonal to the vector pointing from me to you and stay at the same distance from you, is this still true? Also, can you describe what a game of "catch" at near c speeds might look like in the observer frame when the players of catch are moving relative to them? 0¹⁸ (talk) 22:42, 15 September 2010 (UTC)

The problem is that observers moving relative to each other will disagree on what direction the "time" axis is pointing (though they'll both agree that it points somewhere inside the forward light-cone). If only two people are involved, they'll agree on directions that are perpendicular both to the direction of motion and to a line connecting the observers. This will look purely "space-like" to both of them. It's possible that any direction perpendicular to the direction of motion alone would look like this (as all such directions should be perpendicular to both observers' "time" axes), but I'd have to dust off the math to check.

Regarding playing catch, this is one of the standard examples used to derive the Lorentz transformation (usually by considering light bouncing between two mirrors on a moving train). As long as the object being passed is moving slower than light, the observer always sees it moving forward in time no matter what direction it's being thrown in space. The rate at which it moves forward in time will be slightly different from the rate at which the people passing it are moving forward in time, with the exact rate depending on the direction and speed it's being thrown in. From the moving players' point of view, the clock skew that results is just due to the (relatively small) time dilation of the ball moving relative to them as they toss it back and forth. If you draw a spacetime diagram of the game, tracking the world-lines of the ball and of the players, and labelling all "events" (points at one specific time and place) on the graph that you're interested in (e.g. when the ball is caught/thrown by a given player), you can give each of the points consistent timestamps using either the observer's frame or the players' frame, and convert between them using the velocity-addition formula (with the converted answers agreeing with the answers you got from plotting coordinates on the graph). I'm afraid I don't have time at the moment to draw a labelled diagram of this for you (it'd take an hour or two to make an electronic version that was a) pretty, b) readable, and c) correct).

This might be a useful diagram to have for the special relativity article, so I might revisit it at some point when work quiets down. Not soon, unfortunately (and it's more likely that I'd draw a rough version and someone with better tools than I have would adapt a better version from it). --Christopher Thomas (talk) 23:32, 15 September 2010 (UTC)

Addendum: There are quite a lot of very good diagrams at Minkowski diagram showing how the coordinates for different observers change. --Christopher Thomas (talk) 23:58, 15 September 2010 (UTC)

Outrunning a photon

This article neglects superluminal faster than c travel which is allowed under special relativity. Let me begin by quoting Misner, Thorne, and Wheeler, from the classic Gravitation:
"He can out run a photon, if he has a head start on it". The basic idea is simple, due to time dilation, a person can traverse the known universe in a human lifetime. The only limitation is the astronaut's ability to tolerate extreme acceleration. Kip Thorne describes this phenomena throughout his book Black Holes and Time Warps. NOrbeck (talk) 10:04, 27 January 2011 (UTC)

Yeah, and I can outrun Usain Bolt if I have a head start also. But that still doesn't mean I am faster than Usain, just that I started earlier. Getting a head start does not make your speed superluminal. The photon will eventually overtake you no matter what you do. HumphreyW (talk) 10:26, 27 January 2011 (UTC)

Do you feel that the sources are unreliable, or that I have misrepresented/misunderstood them? NOrbeck (talk) 10:52, 27 January 2011 (UTC)

You have misunderstood. Time dilation is what allows you to traverse the universe in a human lifetime. But that doesn't mean you will outrun a photon, just that your perception of time has been altered. Also read about length contraction, that is another thing would appear to make your journey across the universe very short. HumphreyW (talk) 11:09, 27 January 2011 (UTC)

NOrbeck does appear to have misunderstood the source, but nevertheless the photon will never overtake you. You are never travelling faster than light in the laboratory frame, but you approach the speed of light asymptotically, and the photon never catches up. This point does not however appear to have any bearing on the article at this point, given that no faster-than-light travel is involved, so anyone who wants to discuss it further should probably ask a question on the refdesk. --Trovatore (talk) 19:03, 27 January 2011 (UTC)

Correct, this page explains why the photon will never overtake the observer. And you are right, there is in fact no "superluminal" travel here, only faster than c travel. Thorne describes travelling 2 billion light-years in 42 years by maintaining an acceleration of 1 g. That is an average speed of 48 million c. Although the instantaneous velocity (δx/δt) must be less than c, the average velocity (Δx/Δt) has no such limitation. Even though "faster than c" isn't "faster than light", isn't this worth mentioning here? NOrbeck (talk) 01:29, 29 January 2011 (UTC)

This makes no sense. Your delta T is using the wrong reference frame. An observer will always see the photon overtake your hypothetical spaceship because the photon is always travelling faster then the your spaceship. The problem is that you switched reference frames and got some silly result. You can't keep using the observer frame for the distance and then use your local frame for the time since that is comparing apples to oranges. Read up about length shrinking to see why that is wrong. Anyhow the upshot here is that this does not belong in the article because it is wrong. Also in a vacuum, "faster than C" and "faster than light" are the same thing. HumphreyW (talk) 02:38, 29 January 2011 (UTC)

I agree that it doesn't make sense to say you're travelling "faster than c". But no, an external observer will not see the photon overtake the spaceship. That's just not true. As I say, this talk page is not really the right place to discuss it, but you ought to get this straight to avoid undermining the rest of your argument. Maybe bring it up on the Science refdesk and someone can put it better than I can. --Trovatore (talk) 03:52, 29 January 2011 (UTC)

Okay, sure no one can ever watch a photon since that wouldn't make sense, but it still stands that a photon will always be going faster than the spaceship, you can't outrun it, you can't overtake it. HumphreyW (talk) 04:09, 29 January 2011 (UTC)

You can't overtake it but you can avoid being overtaken by it. I've explained in more detail on your talk page. --Trovatore (talk) 04:20, 29 January 2011 (UTC)