Talk:Faster-than-light
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[edit] Attention from expert
I started fixing sections from this article, but it's a real mess. This article needs serious attention from people who know GR, or even just general science. Some of the problems here are basic convolutions of grammar and clearly amateur science writing. I will work on it a bit more tomorrow. SamuelRiv 05:41, 5 November 2007 (UTC)
- Thanks, Samuel. I tried a while ago, but couldn't keep up. I'll try to pay closer attention to the work you're doing.Drernie 17:21, 5 November 2007 (UTC)
The section on Hartman is unreadable for grammar and, for the little bit of intelligibility it has, it seems unsubstantiated or perhaps a little crackpottish.
A refutation for non-constant c might include maxwell's equations. To see how this works, try to derive a wave solution when c is not constant.
Another historical refutation is that c defines the measure of time and space, there is no independent ruler or clock against which to measure its change. But this is similar to an argument offered in the article at present.
The seven quantities cited, are not all basic units; energy for example comprises mass, time and distance, and amount of material is just mass. Mcnelson 15:55, 7 November 2007 (UTC)
Objection
I am very glad to say that the matters are standing much more simple than you are talking. See:
http://www.petar-bosnic-petrus.com/science-articles/conical-and-paraboloidal-superluminal-particle-accelerators/ —Preceding unsigned comment added by 195.29.134.166 (talk) 09:15, 1 April 2008 (UTC)
[edit] Small correction needed
In the section named "Possibility of FTL", it is correctly stated that "Faster-Than-Light travel or communication is prohibited by Einstein's theory of relativity".
However in the section "Tachyon" it is stated: "In special relativity, while it is impossible to accelerate an object to the speed of light, or for a massive object to move at the speed of light, it is not impossible for an object to exist which always moves faster than light."
This second statement is incorrect. Special relativity does not allow any particle (even with zero mass) to move faster than c, the speed of light in the vacuum (there are valide discussions on which "vacuum" should be taken as "the vacuum").
The simplest way to realize that special relativity does not allow any particle moving faster than c is to remark that spoecial relativity works with four REAL numbered axis and a FTL would make Lorentz equation to produce complex numbers. So the vary basic mathematical meaning would be lost.
Of course, some one may claim that we can extend special relativity to deal with complex numbers. That is true. However, as this article correctly points out any change to special relativity has to be very careful since it is very well confirmed by experimental data, and changing the spce-time to have four complex numbered dimensions, may sound mathematically easy, but it is a rather bold and extreme change from Physics point of view. —Preceding unsigned comment added by 189.24.6.58 (talk) 14:22, 7 September 2007 (UTC)
- I have corrected the bland statement about FTL being impossible because of SR. It isn't -- see here and tachyon article. --Michael C. Price talk 10:36, 16 September 2007 (UTC)
- 189.24.6.58 said: The simplest way to realize that special relativity does not allow any particle moving faster than c is to remark that spoecial relativity works with four REAL numbered axis and a FTL would make Lorentz equation to produce complex numbers. So the vary basic mathematical meaning would be lost. Actually, all that this shows is that it doesn't make sense to use the Lorentz transformation to try to define the "frame" of an FTL particle--but that's no big deal, you can't define the frame of a photon either (try plugging v=c into the Lorentz transformation and see what happens). And as explained here, if you assign the tachyon an imaginary rest mass, all its measurable properties in our own sublight frames will be real-valued. Hypnosifl 06:31, 25 September 2007 (UTC)
- A thought about complex numbers that I have not found in science to date- in electronics complex numbers tend to arise in connection with phase shifted values like impedance and capacitance. If you think of spacetime as a 4-d system, then 90 degrees out of phase with 3-d space is just a 4-d location, but not in time. Most consider time as the 4th dimension, but in this case it would be a spacial location. According to the Lorenz transformations any object moving faster than light has a negative complex coordinate. Instead of seeing this as a reversal in time, consider it as a phase shift in 4-d space. If you think of the universal 3-d space as a flat sheet expanding into 4-d space, then an object at light speed has come to a dead stop in the 4 d direction while the sheet continues away from it, causing a gravity funnel, one which light cannot escape. when an object moves faster than light, the location will actually travel below the dead stop point and slightly curved, futher into 4 d-space but not backwards in time...in time, its forward momentum in 3-d space will continue to show slightly less than light speed as the only thing visible will be an event horizon that is moving at less than light speed.Jiohdi (talk) 21:11, 8 April 2008 (UTC)
[edit] 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)
- 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)
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.
[edit] 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)
[edit] 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)
[edit] 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)
[edit] 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)
[edit] 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)
[edit] 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)
[edit] 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)
[edit] 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)
[edit] 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)
