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This is nonsense. Mass bends spacetime. Object would still be subject to relativistic effects. (unsigned 210.55.240.194)
There does seem to be some problem in the exposition around the sentence "conventional relativistic effects such as time dilation do not apply in the way they would in the case of a ship moving at high velocity through flat spacetime".
If the author thought about it for a moment, I'm sure he would realize that "moving at high velocity through flat spacetime" is not assigned a meaning within special or general relativity. All velocities in flat spacetime are completely equivalent wrt the spacetime. The claim may be true in some effective sense, but needs rewording. —Preceding unsigned comment added by 199.67.138.153 ( talk) 15:35, 8 June 2008 (UTC)
I might be completely missing the point of the Alcubierre Drive, but what exactly does the second image represent ? There are no labels or information telling us anything. Does it represent the distance that the space is contracted behind and in front of the ship, or something else ? There should at least be a descriptive caption (or an explanation in the text referring to this image). I await elucidation. :) Mpatel
--- CH
OK, I just didn't know what you referring to before; now I do. The figure in question (not by me) is a graph of the expansion scalar of the canonical congruence in the ADM chart for the original Alcubierre spacetime. In an unpublished paper I argued at great length (too great, really!) why this spacetime is by no means a "solution" of the EFE.---
CH
(talk)
01:36, 22 August 2005 (UTC)
Hi all, I have just corrected a misconception and clarified the present status of 'Warp Drives' in the article on the Alcubierre metric. Unfortunately, at present this article suffers from the same problems I pointed out for the earlier version of the Alcubierre metric article. In addition, I think that the two articles on the same topic is redundant, so the two should be merged.
Possibly instead of explaining the original warp drive in great detail, a slighly simpler version should be used? (After all, the original paper is on-line.) Some years ago, inspired by Broeck's paper, I did some work on simple eigenthing objections, similar to some which have now appeared in print, and wrestled with the energy requirement problem. In fact, I wrote a long unpublished paper on the simpler versions I have in mind.
Someone should add something about the Notario variant, which is expansionless and therefore significantly different from the Alcubierre drive and minor variants such as the one I considered.
And, the merged articles should be retitled warp drive spacetimes, since this term is now fairly standard in the small but slowly growing literature on warp drives. --- Chris Hillman
And relatively easy. I was just about to do it when I noticed an edit conflict with another user, User:Roadrunner, which almost resulted in my losing my work while I was modifying the other article! Annoying that the new Wiki software seems to have a bug which requires users to try to manually resolve problems arising from edit conflicts.
It seems that User:Roadrunner and I disagree about whether or not the Alcubierre spacetimes count as "solutions". I am confident that I can support my contention that they are not (I asked him to read the article on exact solutions of Einstein's field equations, but suggested on the talk page of the article that we all lay off these articles and resolve this controversy on the talk page of the other article. Otherwise, I fear than even if everyone tries to behave nicely, if two of us happen to be modifying one of these pages at the same time, we could potentially lose everyone's work. Presumably no-one wants that!
I think the other article is fair regarding the status of warp drives, but if the two articles can be merged, presumably we don't want to discard the work of the person who made the funky figure. Fortunately, I can elaborate (at arbitrary length!) on the meaning of the expansion tensor, ADM observers, and so forth. Actually, in my unpublished paper I had many more figures which could perhaps be imported to the merged article, but I already fear that it is in danger of getting too long.--- CH (talk) 1 July 2005 06:02 (UTC)
... (myself and Mpatel, both of whom voted to merge), but this message has been up for quite a while, so I'll announce that I intend to carry out the merger as soon as I get a chance.--- CH (talk) 01:39, 22 August 2005 (UTC)
A further vote from a relativist to merge!
Wasn't such an idea used in Captain Future? I saw it in French and they were talking of vitesse|mode ondulatoire (undulating/waving speed|mode) — Reply to David Latapie 15:07, 16 October 2005 (UTC)
Alcubierre's idea is that the spacetime inside the bubble would not be bent (see diagram). Any objects in the bubble would experience no such effects, as spacetime is flat in the center of the bubble, and then gradually becomes more curved towards the edge of the bubble. There would be extreme tidal forces and relativistic time dilations towards the edges of the bubble, where spacetime is extremely bent. A good diagram is given here [1]. (This is a better diagram of the curvature than the one at present, should it be replaced?) Sloverlord 14:21, 10 December 2005 (UTC)
I don't know much about the Alcubierre drive. All i know is that the exotic energy puts it in the impossiblity list. I found a link that states the Alcubierre drive can function without exotic energy: The Positive Energy Spation Warp Drive
This sounds similar to the Soliton Wave technology described in episode 110, " New Ground", of Star Trek: Next Generation. -- tvleavitt 06:42, 13 May 2006 (UTC)
Fanboy mode on... Alcubierre may not be mentioned explicitly, but the Next Generation Technical Manual has an image of a warpfield which clearly shows a two-lobed structure, one ahead of the ship and one behind. (Note that this isn't a fan drawing, it's a color-inverted scan from the official book.) It looks an awful lot like the graph of the Alcubierre metric. The notion that relativistic effects do not affect warp travel was also mentioned, if memory serves. Obviously the two aren't exactly the same, but the shape of the drawing and the constant talk in the series about various types of "warp bubbles" seems to me a pretty clear reference. Worth a mention, at least?
I merged in what I could from Spacewarp. Its going to need further refinement. Cwolfsheep 02:40, 24 July 2006 (UTC)
I'm not proud of this merge, but I disbursed the content as evenly as possible. Someone's going to need to check the math sections: they appear to be the same thing, but they're different formulas. I also tried moving the talk page from the metric article, but not sure if I did it right. Cwolfsheep 03:01, 24 July 2006 (UTC)
In the movie the spice, Melange, has the property of bending space-time in a similar manner to the Alcubierre drive. Dessydes 14:49, 21 August 2006 (UTC)
The one thing I think that is both missing from, and of interest to those viewing this article is the (theoretical) values for various energy requirements, travel times and/or relative speeds. Not being a theoretical physicist, I am yet very interested in the field, particularly new developments. Hence, I would be interested to see any statistics relating to the energy requirements (both from the original Alcubierre metric AND from Loup, Waite and Halerewicz' Reduced total energy requirements for a modified Alcubierre warp drive spacetime mathematics.
If possible, maybe an addition could be made to the original article outlining these three statistics for easily recognised distances, for example: From Sol to Earth, Jupiter, Pluto, the Alpha Centauri system, Rigel, Betelgeuse, and the Milky Way's centre, as well as including other recognisable distances, such as: crossing Milky Way's diameter and from the Milky Way to Andromeda (M31).
Where the variation of energy usage may increase/decrease the values for effective travel time and effective speed, this additional data could be included, also.
This data (I feel) would be of great interest to those of us unable to sift through the mathematics and the background physics necessary to fully comprehend the complexity of the Alcubierre metric. Twphillips 12:15, 13 January 2007 (UTC)
I see this article is tagged "may be confusing or unclear for some readers". There are at least 2 classes of potential reader: those with no mathematical understanding of general relativity (including me) and those with at least some. So I suggest the article should have 4 major sections (including table of contents):
Of course a competent physicist would have to check the "popular" section to ensure that it contained no gross blunders or misrepresentations beyond those inherent in trying to describe a very mathematical subject in ordinary language.
It might even be a good idea to split the article into a popular and a technical article, with the popular article titled "Alcubierre drive" and linking to an article titled "Alcubierre drive (technical analysis)". This would give Wikipedia the option to freeze the popular article after sign-off by a competent physicist and leave the technical article open for editing to take account of new technical publications.
Such a division might also help to get rid of the "requires authentication or verification by an expert" and "missing citations and/or footnotes" tags. Philcha 23:00, 16 February 2007 (UTC)
I would delete that section, because 1) it seems to be more appropriate in Warp drive. 2) The passages like "they allow the transport of physical objects or the transmission of information faster than the speed of light, which is currently understood to be impossible under most circumstances in the real universe", or "While there are natural phenomena that might be likened to warp fields, such as the area of distorted spacetime thought to exist around a black hole, no feasible method of artificially generating one has yet been proposed" look terribly strange amid the discussion of the Alcubierre bubble, which is exactly a means of transportation of physical objects or the transmission of information faster than the speed of light and which is an area of distorted spacetime (though not around a black hole). -- Seador 01:30, 21 February 2007 (UTC)
Dear Edward, Aren't you a bit more positive than consistent? If the light speed barrier is important, than apparently so is one of very few proposed ways to overcome it. Whether this way is obscure is disputable (I, for one, find it quite transparent). But in any case obscurity can be a demerit of an article, not of a metric. So, just tell me what exactly you regard especially obscure in the article and I'll try to clarify that point (with perhaps somebody's help). -- Seador 14:43, 25 February 2007 (UTC)
Well, tastes (and assessments of importance) differ. However I'd like to dispute your arguments.
It is by no means a minor topic in relativity (and even in physics as a whole). For about a century people thought there is a fundamental limit on how soon a signal can get from one point to another. Now, owing to Alcubierre's paper (and the works inspired by it) we know that there is no such limit. I think this a very significant step. The fact that his bubble cannot be built in the foreseen future is immaterial, just because the paper is importance to (theoretical) physics, not to interstellar travel. And that is why the status of this article will not change at all, if someone produce a working Alcubierre drive (which is not impossible, recall that in 1944 many physicists, including Heisenberg, considered the A-bomb to be unphysical by exactly the same reason – an unrealistic quantity of exotic (fissionable) matter was thought to be necessary). That would be a revolution in engineering, applied physics – whatever but theoretical physics, in which its possibility is already understood. I also don't think that most physicists consider "negative energy" to be unphysical. That the WEC breaks down sometimes is an experimentally confirmed fact, see Casimir effect.-- Seador 19:51, 26 February 2007 (UTC)
Yes, I do like the metric and you obviously don't. But apart from that there are some rational considerations. And yours confuse me:
First of all, this metric does not at all remove the light speed barrier
It is 26 lyr from the Sun to Vega and the metric is flat between them. For a century people inferred from this that it cannot take less that 26 yr to reach Vega. Now we know that this is not necessarily the case. To me it looks removing the light speed barrier.
Secondly, the Casimir effect is not all that relevant, as the type and amount of "negative energy" are quite beyond that. In fact, not only is the WEC violated by the Alcubierre, but the strong and dominant energy conditions are also.
The Casimir effect produces the "negative energy" of exactly the required type (the WEC violation always implies the SEC and DEC violations). As for the "amount" the estimates range from 10^67 g to 10^{-5} g and are based on the "quantum inequality" which has never been proved in the 4-dimensional case. Isn't this a too feeble basis for proclaiming something "unphysical"?
I repeat that this metric is not taken seriously by most physicists
I cannot even imagine how you know what most physicists think. Well, you wouldn't include the Alcubierre drive in your imaginary overview course on physics. But I would. So, I don't think this is a good criterion.-- Seador 21:34, 28 February 2007 (UTC)
I agree that being a subject of numerous research papers or being a part of every lawn-mower is a sufficient condition for being acknowledged important. The question is whether this is a necessary condition as well. You probably wouldn't deny the importance (for physics) of the string theory or of the concept of causality. But how many papers a year are published on causality? Have you ever seen a string-power lawn-mower?
Also, as you attach such significance to realizability, let me be pedantic here: a) It takes only a few milligrams (and not several stellar masses!) of exotic matter to support an advanced version of the Alcubierre drive and even that is true only if we believe in "quantum inequalities" , b) The Casimir effect does violate all three Energy conditions (as follows from the fact that it violates even the Null energy condition).-- Seador 17:16, 1 March 2007 (UTC)
Hmm… I, for one, find it much easier to avoid
Brown dwarfs. This obviously depends on the field of interest and expertise. You probably keep from using the concept of FTL travel just because yours are sufficiently far from relativity (I judge from your response: the null (and hence weak, strong, dominant...) energy conditions actually are violated by the Casimir effect in the case of two parallel plates; conservation of energy, on the contrary, does hold in quantum (as well as in classical, relativistic,…) mechanics; finally, in general relativity there is no such thing as potential energy). If it were for me I would perhaps rate the topic as "Top", but as a compromise I propose "High" ("Subject contributes a depth of knowledge", doesn't it?). Or shall we seek a mediator?--
Seador
13:53, 3 March 2007 (UTC)
Though I am not expert enough on the topic to judge whether this model is physically possible or not, it appears to be an interesting 'loophole' through the light speed barrier. On the other hand, an the article like for example Einstein field equations is rated mid importance, though it clearly has a broader impact on the field of physics than this one. Let me propose a compromise. It seems like you are arguing between 'low' and 'high' importance, why not settle for 'mid'? Then focus your energy on making this article meet GA standards.-- V. 21:38, 3 March 2007 (UTC)
Also coming from 3O, it would really help if someone would quickly sum up the problem, i.e., "we disagree on whether the text '...' should be in the article; I think yes because ..., while User:Foo thinks no because ...". Otherwise, people may have trouble helping out here. Sandstein 21:57, 8 March 2007 (UTC)
Like it is stated in the request the disagreement is not about a text, but about the rating of the topic.
EMS lowered it to "Low" because it is 1) not mainstream and 2) at the moment cannot be implemented in any working device. And I think that it should be "High", because it is the (first) proof of the very important (in my view) fact: in contrast to once common belief, general relativity doesn't put any fundamental restriction on how soon a signal from one point can get to another. --
Seador
23:27, 8 March 2007 (UTC)
My advice to the wisest of you would be to let the matter rest, and rest assured that the reader will judge this article on its worth and not its rating. Importance is after all a personal affair, even in physics, and only nature can prove us wrong in the end. An article that is well written will win the most attention and such an article, being coherent and comprehensible, requires no rating to commend it. -- V. 18:18, 9 March 2007 (UTC)
"Sergei Krasnikov is a theoretical physicist at the Central Astronomical Observatory at Pulkovo in St. Petersburg, Russia. He identified what he saw as a critical flaw in Miguel Alcubierre's space warp proposal for space travel: if the space warp moves faster than the velocity of light, it cannot be controlled from inside. Krasnikov's analysis shows that at superluminal speeds the interior of the bubble is causally isolated from its surface and exterior. Photons cannot pass from the inside to the outside. Therefore, there would be no way of controlling the space warp—of stopping, starting or steering."
If you were to set up a track, of sorts, a series of devices strategically placed throughout space that could sustain and move the warp bubble onward through space, which would allow an object to be steered through space at superluminal speeds to an intentional destination. This would mean we would first need to have reached the destination using conventional methods to deploy such devices, but at least it would make the trip much faster for future travelers. -- Steakpirate 04:52, 27 April 2007 (UTC)
Just out of curiosity, is there a plan to re-do the criticisms section? Most of the text is really confusing and doesn't really seem to do much, nor does it have any sort of reference section for these criticisms, indicating that they're likely just somebody's opinion. Thanks. —Preceding unsigned comment added by 199.31.3.195 ( talk) 16:08, 12 October 2007 (UTC)
I have removed the last item because 1) Coule just retold Krasnikov's result and 2) it is, in fact, what is already said in the first item. Kidburla, if you feel that the idea should also be expressed in terms of tachyonic matter, maybe you'd better expand that item? -- Seador 12:40, 2 May 2007 (UTC)
I would like to question the purpose of this part of the entry.
"Because nothing can travel faster than the speed of light, it has been stated that bending spacetime itself would cause an object to travel faster than light; this idea has been utilized in the Warp Drive concept in science fiction, but also is the Alcubierre drive theory. The following formula, based on general relativity, permits the travel of an object faster than light provided that spacetime is curved[1]:
If spacetime is warped in this way, then technically the object(s) are not moving faster than light, instead, the space around them shifts so that that object(s) arrives at its destination faster than light would in normal space. Space would be collapsing at one end of the "bubble" and expanding at the other end."
This seems to me to be a case of someone blindly quoting something they do not understand and have no idea what it means. My main problem is,
this does not mean anything. One can only assume that he means the Einstein Field Equations which are,
I am really not sure about what this person is getting at. First off the Field Equations always assume that space is curved, otherwise we can use simple old Newtonian Physics(or SR if we are traveling sufficiently fast) to describe the interactions. Also if my memory serves me right(and since I am currently a few hundred miles away from my copy of Misner Thorne and Wheeler's Gravitation it will be a few days before I can look it up), you can travel faster than the speed of light in an inertial reference frame, ie that matter can only travel less than or equal to the speed of light is constraint of SR that gets broken under GR. So this seems of little importance to the topic. Since the rest of this section simply says that normally we take the Strss-Energy Tensor and try to find the Curvature Tensor, but with this instance there was a proposed Metric and the Curvature Tensor was Created, I suggest that the portion that was quoted be deleted. Jetherrie 04:40, 12 May 2007 (UTC)
I may not be an expert in quantum/time physics but.. there is theoretical proof that an electron (or quantum) can appear at random from "nothing" at any given time or place. However, the act of observing this event determines the outcome of the event. Therefore, if the event is unobserved it must take place. To enable travel at FTL two things must occur: Unobservence and creation of randomness on a molecular (subatomic) scale. The mechanics of acheiving this state would be reliant on Einstein's e=Mc2, where there is enough energy imposed to translate the mass of each individual atomic and sub-atomic particle to the speed of light, and a "directional" component to control the randomness.The entire event to be unobserved may be reliant on the uncertainty principal. Just a thought....
I just reverted two changes by Harold f, and wanted to explain why. First, he changed
to
But the intent of the original sentence was that the space inside the bubble is flat. I think it's clear from context that the space outside is flat and that the warp bubble effectively moves faster than light. Secondly, he changed the sentence
by adding "provided that the warp bubble itself is not considered an object". But this condition is unnecessary, since what's being referred to here is the prohibition on local superluminal travel (i.e. with respect to the local metric), and the warp bubble doesn't violate this in point of fact. -- BenRG 11:05, 19 August 2007 (UTC)
I object to the removal of the page. There are a number of references at the bottom of the page, and though the page needs work, it is an important article in discussing the attempts of science to explain the theorhetical world of faster than light travel. This article should not be removed, rather improved over time. - Eisenmond —Preceding unsigned comment added by 192.91.171.36 ( talk) 21:22, 13 November 2007 (UTC)
I'll add a few necessary references within a couple of days. But could you help me by explaining what do I do to get the references in the usual style (when I can refer a few times to the same source), like
"It was shown in [1] and [2], while that was proven in [1] and [3]...
[1] Smith, PRD...
[2] Brown, PRL...
[3] Green, CQG...
-- Seador 22:53, 13 November 2007 (UTC)
Blah, blah, statement of fact.<ref>insert citation here</ref>
and then, at the end of the page, add the following section
==References== <references/>
which will cause the footnotes to be listed there. Hope this helps. Pastordavid 15:43, 14 November 2007 (UTC)
I don't know if you still want this information as this thread was quite stale when I came across it, but this is how you do multiple cites to the same reference:
The first time you put in an inline reference like so;
<ref name="anything">Insert citation here</ref>
Then on subsequent uses you just insert;
<ref name="anything"/>
I prefer to use a template for the references section like so
==References==
{{reflist}}
And it will end up looking like this in the article;
Peter Piper picked a peck . . .
[1]
Ring a ring a roses . . .
[1]
Hope this helps.
SpinningSpark
21:24, 4 January 2008 (UTC)
I've come across this article a few days ago, and reading the talk page I get the idea that the article has been proposed for removal. I sincerely object to the proposal for removal, as it did indeed seem a very good article by now - citing a lot of references, while explaining clearly the idea behind it. Also, I did not find any part of the article ambiguous or unclear, in my opinion the authors have done a really wonderful job of making the concept understandable in layman's terms. I really found this article useful. I hope this post helps in preserving this article for the future. Thanks, Hirak 99 ( talk) 16:46, 10 January 2008 (UTC)
Could the author explain:
What exactly does this mean? Did he propose to consider time machines? Together with the bubbles? Instead of them? How can consideration of time machines allow for multiply-connected spaces?
What is meant by "closing the geodesic incompleteness"? What are the "quantum instability requirements" and why would one wish to satisfy them? -- Seador ( talk) 01:07, 14 January 2008 (UTC)
What would happen if a spaceship travelling with an Alcubierre drive ran into some object? Would it shatter to pieces like you'd expect a really-really-fast impact to or would something more exotic happen? What if instead of a physical object, the spaceship collided with another warp bubble? -- Milo —Preceding unsigned comment added by 81.171.2.42 ( talk) 19:52, 26 February 2008 (UTC)
I'm sorry but the following quote (and section of the article) makes very little sense to me, even when I try to put it into context in terms of this article.
"The pilot inside the bubble is causally disconnected with its walls. Therefore the bubble cannot be used for the first faster-than-light trip to a distant star. In other words, to travel to Vega (which is 26 light-years from the Earth) one first has to arrange everything so that the bubble moving toward Vega with a superluminal velocity would appear and these arrangements will always take more than 26 years (Krasnikov, 1998)."
Am I just, for some reason, incapable of understanding this and it's written correctly or am I right and there's something wrong with it. I've reread it several times and it still makes very little sense to me. Rajrajmarley ( talk) 03:50, 3 March 2008 (UTC)
At first glance everything seems clear. What exactly is the problem?
Seador (
talk)
16:43, 4 March 2008 (UTC)
This article seems to have a slight anti bias to it. Does anyone else think so? Zazaban ( talk) 23:29, 8 April 2008 (UTC)
Currently, this article states, "The Alcubierre Drive vessel is not able to go dashing around the galaxy at will. It is only able to travel routes which, like a railroad, have first been equipped with the necessary infrastructure." This is very definite statement about a theory that is far from definite. Do all versions of this theory require a road? If not, qualifiers are needed, such as "in some versions of this theory, an Alcubierre Drive vessel must travel routes . . . ." Either way, more citations are needed. 98.209.154.40 ( talk) 06:36, 11 June 2008 (UTC)
Sounds good Spinningspark. Thank you. 98.209.154.40 ( talk) 18:21, 11 June 2008 (UTC)
The Star Trek diagram in this article has been bothering me for some time and I wanted to test what others think of it. The image licence claims that it was created by the uploader and appears to have been made by plonking a starship image on an Albubierre field diagram. If it is self-created and not based on anything in the Star Trek fictional universe then it is WP:OR and should be removed. The text of this section also seems to indicate that the scriptwriters have not strongly aligned themselves with Alcubierre. Retaining this diagram gives the false impression of the opposite. On the other hand, if it is based on something in the Star Trek technical manuals then a reference should be provided to indicate its in-universe provenance. SpinningSpark 18:39, 29 November 2008 (UTC)
![]() | This is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
Archive 1 | Archive 2 | Archive 3 | Archive 4 |
![]() | This is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
Archive 1 | Archive 2 | Archive 3 | Archive 4 |
This is nonsense. Mass bends spacetime. Object would still be subject to relativistic effects. (unsigned 210.55.240.194)
There does seem to be some problem in the exposition around the sentence "conventional relativistic effects such as time dilation do not apply in the way they would in the case of a ship moving at high velocity through flat spacetime".
If the author thought about it for a moment, I'm sure he would realize that "moving at high velocity through flat spacetime" is not assigned a meaning within special or general relativity. All velocities in flat spacetime are completely equivalent wrt the spacetime. The claim may be true in some effective sense, but needs rewording. —Preceding unsigned comment added by 199.67.138.153 ( talk) 15:35, 8 June 2008 (UTC)
I might be completely missing the point of the Alcubierre Drive, but what exactly does the second image represent ? There are no labels or information telling us anything. Does it represent the distance that the space is contracted behind and in front of the ship, or something else ? There should at least be a descriptive caption (or an explanation in the text referring to this image). I await elucidation. :) Mpatel
--- CH
OK, I just didn't know what you referring to before; now I do. The figure in question (not by me) is a graph of the expansion scalar of the canonical congruence in the ADM chart for the original Alcubierre spacetime. In an unpublished paper I argued at great length (too great, really!) why this spacetime is by no means a "solution" of the EFE.---
CH
(talk)
01:36, 22 August 2005 (UTC)
Hi all, I have just corrected a misconception and clarified the present status of 'Warp Drives' in the article on the Alcubierre metric. Unfortunately, at present this article suffers from the same problems I pointed out for the earlier version of the Alcubierre metric article. In addition, I think that the two articles on the same topic is redundant, so the two should be merged.
Possibly instead of explaining the original warp drive in great detail, a slighly simpler version should be used? (After all, the original paper is on-line.) Some years ago, inspired by Broeck's paper, I did some work on simple eigenthing objections, similar to some which have now appeared in print, and wrestled with the energy requirement problem. In fact, I wrote a long unpublished paper on the simpler versions I have in mind.
Someone should add something about the Notario variant, which is expansionless and therefore significantly different from the Alcubierre drive and minor variants such as the one I considered.
And, the merged articles should be retitled warp drive spacetimes, since this term is now fairly standard in the small but slowly growing literature on warp drives. --- Chris Hillman
And relatively easy. I was just about to do it when I noticed an edit conflict with another user, User:Roadrunner, which almost resulted in my losing my work while I was modifying the other article! Annoying that the new Wiki software seems to have a bug which requires users to try to manually resolve problems arising from edit conflicts.
It seems that User:Roadrunner and I disagree about whether or not the Alcubierre spacetimes count as "solutions". I am confident that I can support my contention that they are not (I asked him to read the article on exact solutions of Einstein's field equations, but suggested on the talk page of the article that we all lay off these articles and resolve this controversy on the talk page of the other article. Otherwise, I fear than even if everyone tries to behave nicely, if two of us happen to be modifying one of these pages at the same time, we could potentially lose everyone's work. Presumably no-one wants that!
I think the other article is fair regarding the status of warp drives, but if the two articles can be merged, presumably we don't want to discard the work of the person who made the funky figure. Fortunately, I can elaborate (at arbitrary length!) on the meaning of the expansion tensor, ADM observers, and so forth. Actually, in my unpublished paper I had many more figures which could perhaps be imported to the merged article, but I already fear that it is in danger of getting too long.--- CH (talk) 1 July 2005 06:02 (UTC)
... (myself and Mpatel, both of whom voted to merge), but this message has been up for quite a while, so I'll announce that I intend to carry out the merger as soon as I get a chance.--- CH (talk) 01:39, 22 August 2005 (UTC)
A further vote from a relativist to merge!
Wasn't such an idea used in Captain Future? I saw it in French and they were talking of vitesse|mode ondulatoire (undulating/waving speed|mode) — Reply to David Latapie 15:07, 16 October 2005 (UTC)
Alcubierre's idea is that the spacetime inside the bubble would not be bent (see diagram). Any objects in the bubble would experience no such effects, as spacetime is flat in the center of the bubble, and then gradually becomes more curved towards the edge of the bubble. There would be extreme tidal forces and relativistic time dilations towards the edges of the bubble, where spacetime is extremely bent. A good diagram is given here [1]. (This is a better diagram of the curvature than the one at present, should it be replaced?) Sloverlord 14:21, 10 December 2005 (UTC)
I don't know much about the Alcubierre drive. All i know is that the exotic energy puts it in the impossiblity list. I found a link that states the Alcubierre drive can function without exotic energy: The Positive Energy Spation Warp Drive
This sounds similar to the Soliton Wave technology described in episode 110, " New Ground", of Star Trek: Next Generation. -- tvleavitt 06:42, 13 May 2006 (UTC)
Fanboy mode on... Alcubierre may not be mentioned explicitly, but the Next Generation Technical Manual has an image of a warpfield which clearly shows a two-lobed structure, one ahead of the ship and one behind. (Note that this isn't a fan drawing, it's a color-inverted scan from the official book.) It looks an awful lot like the graph of the Alcubierre metric. The notion that relativistic effects do not affect warp travel was also mentioned, if memory serves. Obviously the two aren't exactly the same, but the shape of the drawing and the constant talk in the series about various types of "warp bubbles" seems to me a pretty clear reference. Worth a mention, at least?
I merged in what I could from Spacewarp. Its going to need further refinement. Cwolfsheep 02:40, 24 July 2006 (UTC)
I'm not proud of this merge, but I disbursed the content as evenly as possible. Someone's going to need to check the math sections: they appear to be the same thing, but they're different formulas. I also tried moving the talk page from the metric article, but not sure if I did it right. Cwolfsheep 03:01, 24 July 2006 (UTC)
In the movie the spice, Melange, has the property of bending space-time in a similar manner to the Alcubierre drive. Dessydes 14:49, 21 August 2006 (UTC)
The one thing I think that is both missing from, and of interest to those viewing this article is the (theoretical) values for various energy requirements, travel times and/or relative speeds. Not being a theoretical physicist, I am yet very interested in the field, particularly new developments. Hence, I would be interested to see any statistics relating to the energy requirements (both from the original Alcubierre metric AND from Loup, Waite and Halerewicz' Reduced total energy requirements for a modified Alcubierre warp drive spacetime mathematics.
If possible, maybe an addition could be made to the original article outlining these three statistics for easily recognised distances, for example: From Sol to Earth, Jupiter, Pluto, the Alpha Centauri system, Rigel, Betelgeuse, and the Milky Way's centre, as well as including other recognisable distances, such as: crossing Milky Way's diameter and from the Milky Way to Andromeda (M31).
Where the variation of energy usage may increase/decrease the values for effective travel time and effective speed, this additional data could be included, also.
This data (I feel) would be of great interest to those of us unable to sift through the mathematics and the background physics necessary to fully comprehend the complexity of the Alcubierre metric. Twphillips 12:15, 13 January 2007 (UTC)
I see this article is tagged "may be confusing or unclear for some readers". There are at least 2 classes of potential reader: those with no mathematical understanding of general relativity (including me) and those with at least some. So I suggest the article should have 4 major sections (including table of contents):
Of course a competent physicist would have to check the "popular" section to ensure that it contained no gross blunders or misrepresentations beyond those inherent in trying to describe a very mathematical subject in ordinary language.
It might even be a good idea to split the article into a popular and a technical article, with the popular article titled "Alcubierre drive" and linking to an article titled "Alcubierre drive (technical analysis)". This would give Wikipedia the option to freeze the popular article after sign-off by a competent physicist and leave the technical article open for editing to take account of new technical publications.
Such a division might also help to get rid of the "requires authentication or verification by an expert" and "missing citations and/or footnotes" tags. Philcha 23:00, 16 February 2007 (UTC)
I would delete that section, because 1) it seems to be more appropriate in Warp drive. 2) The passages like "they allow the transport of physical objects or the transmission of information faster than the speed of light, which is currently understood to be impossible under most circumstances in the real universe", or "While there are natural phenomena that might be likened to warp fields, such as the area of distorted spacetime thought to exist around a black hole, no feasible method of artificially generating one has yet been proposed" look terribly strange amid the discussion of the Alcubierre bubble, which is exactly a means of transportation of physical objects or the transmission of information faster than the speed of light and which is an area of distorted spacetime (though not around a black hole). -- Seador 01:30, 21 February 2007 (UTC)
Dear Edward, Aren't you a bit more positive than consistent? If the light speed barrier is important, than apparently so is one of very few proposed ways to overcome it. Whether this way is obscure is disputable (I, for one, find it quite transparent). But in any case obscurity can be a demerit of an article, not of a metric. So, just tell me what exactly you regard especially obscure in the article and I'll try to clarify that point (with perhaps somebody's help). -- Seador 14:43, 25 February 2007 (UTC)
Well, tastes (and assessments of importance) differ. However I'd like to dispute your arguments.
It is by no means a minor topic in relativity (and even in physics as a whole). For about a century people thought there is a fundamental limit on how soon a signal can get from one point to another. Now, owing to Alcubierre's paper (and the works inspired by it) we know that there is no such limit. I think this a very significant step. The fact that his bubble cannot be built in the foreseen future is immaterial, just because the paper is importance to (theoretical) physics, not to interstellar travel. And that is why the status of this article will not change at all, if someone produce a working Alcubierre drive (which is not impossible, recall that in 1944 many physicists, including Heisenberg, considered the A-bomb to be unphysical by exactly the same reason – an unrealistic quantity of exotic (fissionable) matter was thought to be necessary). That would be a revolution in engineering, applied physics – whatever but theoretical physics, in which its possibility is already understood. I also don't think that most physicists consider "negative energy" to be unphysical. That the WEC breaks down sometimes is an experimentally confirmed fact, see Casimir effect.-- Seador 19:51, 26 February 2007 (UTC)
Yes, I do like the metric and you obviously don't. But apart from that there are some rational considerations. And yours confuse me:
First of all, this metric does not at all remove the light speed barrier
It is 26 lyr from the Sun to Vega and the metric is flat between them. For a century people inferred from this that it cannot take less that 26 yr to reach Vega. Now we know that this is not necessarily the case. To me it looks removing the light speed barrier.
Secondly, the Casimir effect is not all that relevant, as the type and amount of "negative energy" are quite beyond that. In fact, not only is the WEC violated by the Alcubierre, but the strong and dominant energy conditions are also.
The Casimir effect produces the "negative energy" of exactly the required type (the WEC violation always implies the SEC and DEC violations). As for the "amount" the estimates range from 10^67 g to 10^{-5} g and are based on the "quantum inequality" which has never been proved in the 4-dimensional case. Isn't this a too feeble basis for proclaiming something "unphysical"?
I repeat that this metric is not taken seriously by most physicists
I cannot even imagine how you know what most physicists think. Well, you wouldn't include the Alcubierre drive in your imaginary overview course on physics. But I would. So, I don't think this is a good criterion.-- Seador 21:34, 28 February 2007 (UTC)
I agree that being a subject of numerous research papers or being a part of every lawn-mower is a sufficient condition for being acknowledged important. The question is whether this is a necessary condition as well. You probably wouldn't deny the importance (for physics) of the string theory or of the concept of causality. But how many papers a year are published on causality? Have you ever seen a string-power lawn-mower?
Also, as you attach such significance to realizability, let me be pedantic here: a) It takes only a few milligrams (and not several stellar masses!) of exotic matter to support an advanced version of the Alcubierre drive and even that is true only if we believe in "quantum inequalities" , b) The Casimir effect does violate all three Energy conditions (as follows from the fact that it violates even the Null energy condition).-- Seador 17:16, 1 March 2007 (UTC)
Hmm… I, for one, find it much easier to avoid
Brown dwarfs. This obviously depends on the field of interest and expertise. You probably keep from using the concept of FTL travel just because yours are sufficiently far from relativity (I judge from your response: the null (and hence weak, strong, dominant...) energy conditions actually are violated by the Casimir effect in the case of two parallel plates; conservation of energy, on the contrary, does hold in quantum (as well as in classical, relativistic,…) mechanics; finally, in general relativity there is no such thing as potential energy). If it were for me I would perhaps rate the topic as "Top", but as a compromise I propose "High" ("Subject contributes a depth of knowledge", doesn't it?). Or shall we seek a mediator?--
Seador
13:53, 3 March 2007 (UTC)
Though I am not expert enough on the topic to judge whether this model is physically possible or not, it appears to be an interesting 'loophole' through the light speed barrier. On the other hand, an the article like for example Einstein field equations is rated mid importance, though it clearly has a broader impact on the field of physics than this one. Let me propose a compromise. It seems like you are arguing between 'low' and 'high' importance, why not settle for 'mid'? Then focus your energy on making this article meet GA standards.-- V. 21:38, 3 March 2007 (UTC)
Also coming from 3O, it would really help if someone would quickly sum up the problem, i.e., "we disagree on whether the text '...' should be in the article; I think yes because ..., while User:Foo thinks no because ...". Otherwise, people may have trouble helping out here. Sandstein 21:57, 8 March 2007 (UTC)
Like it is stated in the request the disagreement is not about a text, but about the rating of the topic.
EMS lowered it to "Low" because it is 1) not mainstream and 2) at the moment cannot be implemented in any working device. And I think that it should be "High", because it is the (first) proof of the very important (in my view) fact: in contrast to once common belief, general relativity doesn't put any fundamental restriction on how soon a signal from one point can get to another. --
Seador
23:27, 8 March 2007 (UTC)
My advice to the wisest of you would be to let the matter rest, and rest assured that the reader will judge this article on its worth and not its rating. Importance is after all a personal affair, even in physics, and only nature can prove us wrong in the end. An article that is well written will win the most attention and such an article, being coherent and comprehensible, requires no rating to commend it. -- V. 18:18, 9 March 2007 (UTC)
"Sergei Krasnikov is a theoretical physicist at the Central Astronomical Observatory at Pulkovo in St. Petersburg, Russia. He identified what he saw as a critical flaw in Miguel Alcubierre's space warp proposal for space travel: if the space warp moves faster than the velocity of light, it cannot be controlled from inside. Krasnikov's analysis shows that at superluminal speeds the interior of the bubble is causally isolated from its surface and exterior. Photons cannot pass from the inside to the outside. Therefore, there would be no way of controlling the space warp—of stopping, starting or steering."
If you were to set up a track, of sorts, a series of devices strategically placed throughout space that could sustain and move the warp bubble onward through space, which would allow an object to be steered through space at superluminal speeds to an intentional destination. This would mean we would first need to have reached the destination using conventional methods to deploy such devices, but at least it would make the trip much faster for future travelers. -- Steakpirate 04:52, 27 April 2007 (UTC)
Just out of curiosity, is there a plan to re-do the criticisms section? Most of the text is really confusing and doesn't really seem to do much, nor does it have any sort of reference section for these criticisms, indicating that they're likely just somebody's opinion. Thanks. —Preceding unsigned comment added by 199.31.3.195 ( talk) 16:08, 12 October 2007 (UTC)
I have removed the last item because 1) Coule just retold Krasnikov's result and 2) it is, in fact, what is already said in the first item. Kidburla, if you feel that the idea should also be expressed in terms of tachyonic matter, maybe you'd better expand that item? -- Seador 12:40, 2 May 2007 (UTC)
I would like to question the purpose of this part of the entry.
"Because nothing can travel faster than the speed of light, it has been stated that bending spacetime itself would cause an object to travel faster than light; this idea has been utilized in the Warp Drive concept in science fiction, but also is the Alcubierre drive theory. The following formula, based on general relativity, permits the travel of an object faster than light provided that spacetime is curved[1]:
If spacetime is warped in this way, then technically the object(s) are not moving faster than light, instead, the space around them shifts so that that object(s) arrives at its destination faster than light would in normal space. Space would be collapsing at one end of the "bubble" and expanding at the other end."
This seems to me to be a case of someone blindly quoting something they do not understand and have no idea what it means. My main problem is,
this does not mean anything. One can only assume that he means the Einstein Field Equations which are,
I am really not sure about what this person is getting at. First off the Field Equations always assume that space is curved, otherwise we can use simple old Newtonian Physics(or SR if we are traveling sufficiently fast) to describe the interactions. Also if my memory serves me right(and since I am currently a few hundred miles away from my copy of Misner Thorne and Wheeler's Gravitation it will be a few days before I can look it up), you can travel faster than the speed of light in an inertial reference frame, ie that matter can only travel less than or equal to the speed of light is constraint of SR that gets broken under GR. So this seems of little importance to the topic. Since the rest of this section simply says that normally we take the Strss-Energy Tensor and try to find the Curvature Tensor, but with this instance there was a proposed Metric and the Curvature Tensor was Created, I suggest that the portion that was quoted be deleted. Jetherrie 04:40, 12 May 2007 (UTC)
I may not be an expert in quantum/time physics but.. there is theoretical proof that an electron (or quantum) can appear at random from "nothing" at any given time or place. However, the act of observing this event determines the outcome of the event. Therefore, if the event is unobserved it must take place. To enable travel at FTL two things must occur: Unobservence and creation of randomness on a molecular (subatomic) scale. The mechanics of acheiving this state would be reliant on Einstein's e=Mc2, where there is enough energy imposed to translate the mass of each individual atomic and sub-atomic particle to the speed of light, and a "directional" component to control the randomness.The entire event to be unobserved may be reliant on the uncertainty principal. Just a thought....
I just reverted two changes by Harold f, and wanted to explain why. First, he changed
to
But the intent of the original sentence was that the space inside the bubble is flat. I think it's clear from context that the space outside is flat and that the warp bubble effectively moves faster than light. Secondly, he changed the sentence
by adding "provided that the warp bubble itself is not considered an object". But this condition is unnecessary, since what's being referred to here is the prohibition on local superluminal travel (i.e. with respect to the local metric), and the warp bubble doesn't violate this in point of fact. -- BenRG 11:05, 19 August 2007 (UTC)
I object to the removal of the page. There are a number of references at the bottom of the page, and though the page needs work, it is an important article in discussing the attempts of science to explain the theorhetical world of faster than light travel. This article should not be removed, rather improved over time. - Eisenmond —Preceding unsigned comment added by 192.91.171.36 ( talk) 21:22, 13 November 2007 (UTC)
I'll add a few necessary references within a couple of days. But could you help me by explaining what do I do to get the references in the usual style (when I can refer a few times to the same source), like
"It was shown in [1] and [2], while that was proven in [1] and [3]...
[1] Smith, PRD...
[2] Brown, PRL...
[3] Green, CQG...
-- Seador 22:53, 13 November 2007 (UTC)
Blah, blah, statement of fact.<ref>insert citation here</ref>
and then, at the end of the page, add the following section
==References== <references/>
which will cause the footnotes to be listed there. Hope this helps. Pastordavid 15:43, 14 November 2007 (UTC)
I don't know if you still want this information as this thread was quite stale when I came across it, but this is how you do multiple cites to the same reference:
The first time you put in an inline reference like so;
<ref name="anything">Insert citation here</ref>
Then on subsequent uses you just insert;
<ref name="anything"/>
I prefer to use a template for the references section like so
==References==
{{reflist}}
And it will end up looking like this in the article;
Peter Piper picked a peck . . .
[1]
Ring a ring a roses . . .
[1]
Hope this helps.
SpinningSpark
21:24, 4 January 2008 (UTC)
I've come across this article a few days ago, and reading the talk page I get the idea that the article has been proposed for removal. I sincerely object to the proposal for removal, as it did indeed seem a very good article by now - citing a lot of references, while explaining clearly the idea behind it. Also, I did not find any part of the article ambiguous or unclear, in my opinion the authors have done a really wonderful job of making the concept understandable in layman's terms. I really found this article useful. I hope this post helps in preserving this article for the future. Thanks, Hirak 99 ( talk) 16:46, 10 January 2008 (UTC)
Could the author explain:
What exactly does this mean? Did he propose to consider time machines? Together with the bubbles? Instead of them? How can consideration of time machines allow for multiply-connected spaces?
What is meant by "closing the geodesic incompleteness"? What are the "quantum instability requirements" and why would one wish to satisfy them? -- Seador ( talk) 01:07, 14 January 2008 (UTC)
What would happen if a spaceship travelling with an Alcubierre drive ran into some object? Would it shatter to pieces like you'd expect a really-really-fast impact to or would something more exotic happen? What if instead of a physical object, the spaceship collided with another warp bubble? -- Milo —Preceding unsigned comment added by 81.171.2.42 ( talk) 19:52, 26 February 2008 (UTC)
I'm sorry but the following quote (and section of the article) makes very little sense to me, even when I try to put it into context in terms of this article.
"The pilot inside the bubble is causally disconnected with its walls. Therefore the bubble cannot be used for the first faster-than-light trip to a distant star. In other words, to travel to Vega (which is 26 light-years from the Earth) one first has to arrange everything so that the bubble moving toward Vega with a superluminal velocity would appear and these arrangements will always take more than 26 years (Krasnikov, 1998)."
Am I just, for some reason, incapable of understanding this and it's written correctly or am I right and there's something wrong with it. I've reread it several times and it still makes very little sense to me. Rajrajmarley ( talk) 03:50, 3 March 2008 (UTC)
At first glance everything seems clear. What exactly is the problem?
Seador (
talk)
16:43, 4 March 2008 (UTC)
This article seems to have a slight anti bias to it. Does anyone else think so? Zazaban ( talk) 23:29, 8 April 2008 (UTC)
Currently, this article states, "The Alcubierre Drive vessel is not able to go dashing around the galaxy at will. It is only able to travel routes which, like a railroad, have first been equipped with the necessary infrastructure." This is very definite statement about a theory that is far from definite. Do all versions of this theory require a road? If not, qualifiers are needed, such as "in some versions of this theory, an Alcubierre Drive vessel must travel routes . . . ." Either way, more citations are needed. 98.209.154.40 ( talk) 06:36, 11 June 2008 (UTC)
Sounds good Spinningspark. Thank you. 98.209.154.40 ( talk) 18:21, 11 June 2008 (UTC)
The Star Trek diagram in this article has been bothering me for some time and I wanted to test what others think of it. The image licence claims that it was created by the uploader and appears to have been made by plonking a starship image on an Albubierre field diagram. If it is self-created and not based on anything in the Star Trek fictional universe then it is WP:OR and should be removed. The text of this section also seems to indicate that the scriptwriters have not strongly aligned themselves with Alcubierre. Retaining this diagram gives the false impression of the opposite. On the other hand, if it is based on something in the Star Trek technical manuals then a reference should be provided to indicate its in-universe provenance. SpinningSpark 18:39, 29 November 2008 (UTC)
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