Talk:Alcubierre drive/Archive 4

Archive 1

Archive 2

Archive 3

Archive 4

Mention

the drive is mentioned in the recent "escape to witch mountain" movie with dwayne johnson. maybe that's useless. —Preceding unsigned comment added by 71.51.8.117 (talk) 22:37, 31 August 2009 (UTC)

Accidental implicature regarding creation of warp bubble

"However, there are no known methods to create such a warp bubble in a region that does not already contain one" suggests that we know how to create new warp bubbles in the presence of an existing warp bubble; is this true? Otherwise, the misleading phrasing should be changed. Solarswordsman (talk) 02:18, 18 October 2010 (UTC)

Recent edits to science fiction section

The "citation needed" tags were recently removed from two items on the grounds that the book and game are their own references. I accept that they can be their own reference if they do indeed clearly state the thing claimed. However, the referencing is inadequate. For a book a page number is usual and/or a direct quote from the relevant passage. For the game, games usually come with a manual which could be quoted, or failing that, a quote from the dialogue of the game could be provided. Without this, there is a suspicion that the claim is a synthesis by the editor who inserted the claim. If it is indeed a synthesis, then references reviews making that synthesis should be provided. Either way citations are needed.

I also object to the removal of faster-than-light propulsion methods most of which have nothing to do with the Alcubierre drive or any other physical theory. This is indisputably true, a vast phalanx of science fiction writers, including Isaac Asimov, Robert Heinlein and Larry Niven, have required faster-than-light travel since at least the 1950s, long before Alcubierre's proposal in 1994. Alcubierre has been a boon to science fiction providing a science basis for a faster-than-light drive which is often, inappropriately, retrospectively applied to past works. Citations are certainly important here to make sure Wikipedia is not a party to spreading disinformation.

On a more general point, all science articles that have a "X in popular culture", or similar section, tend to degenerate into unhelpful listcruft. What this section should be doing, but does not, is documenting the spread of Alcubierre in the genre from the its first historic use, through all its innovative appearances, to the status it has today. In other words, there should be a mini-article there, not a list. Insisting on proper citations at least has the benefit of discouraging "drive-by" additions to a non-notable list, and really, we should be rejecting anything there that does not add to an understanding of how Alcubierre drive has developed in the genre, whether it is cited or not. Simply listing every occurence one comes across is as pointless as mentioning every occurence of "dress" found in Mills & Boon novels in a list in the dress article. SpinningSpark 13:11, 15 February 2009 (UTC)

I have to disagree with the above. The Warp Drive in Star Trek is clearly doing approximately the same thing as the Alcubierre drive. Alcubierre, in fact, was inspired by Star Trek!!!! "The theoretical physicist wrote in an e-mail to William Shatner that his conceptualization was directly inspired by Star Trek. “The very name ‘warp drive’ means it must distort space.” (Shatner, I’m Working on That) The idea started out as a “lark,” but soon became serious physics. The paper has been hailed by many as a landmark in the transition from warp drive being “merely fictional” to being a real scientific topic. Alcubierre’s scheme violates no known physical laws, and provides a valid mathematical description and metric, based on hyperbolic tangent functions, of the precise curvature of space that would permit round-trip travel between two locations separated by light-years in an arbitrarily short time." I get that quotation from http://www.alan-shapiro.com/the-physics-of-warp-drive/ so...I don't see where you guys are coming from when you claim that the alcubierre drive has nothing to do with warp in Star Trek. I suppose that if someone determines a way to pass into higher dimensions temporarily to cross vast distances in space, you guys will claim it has nothing to do with hyperspace jumps as seen in Star Wars. that's lame. ((eye roll)) No one is saying ST or SW is hard SF, but still, the alcubierre drive concept is an attempt to do warp drive as seen in Star Trek. 68.186.48.171 (talk) 18:34, 20 March 2011 (UTC)

I'm the same person who wrote the above paragraph...plus the paper itself says in the abstract "The resulting distortion is reminiscent of the “warp drive” of science fiction." Where is that phrase most commonly used? STAR TREK!!! So, I don't see how it can be claimed that it "has nothing to do with" Star Trek. to get the actual research paper see this link: http://arxiv.org/abs/grqc/0009013 from the wikipedia warp drive entry, "the warp drive does not permit instantaneous travel between two points; instead, warp drive technology creates an artificial "bubble" of normal space-time that surrounds the spacecraft" sounds like the alcubierre drive to me. 68.186.48.171 (talk) 18:49, 20 March 2011 (UTC)

Reactionless drive?

Would an Alcubierre drive be a Reactionless drive? Wardog (talk) 11:26, 12 May 2011 (UTC)

Avoiding the problems about energy requirement and Hawking radiation.

String theory (and all other theories involving hidden dimensions)

predict that gravity and electromagnetism unify in hidden 

dimensions and that the hidden dimensions are indetectible because of their small size. It does also predict that sufficiently short-waved photons, with wavelengths shorter than the size of the hidden dimensions, can enter them. Producing ultra-short photons can thus manipulate gravity, with revolutionizing space travel applications such as cheap anti-gravity launches. The problem that it would require high energy can be practically solved by concentrating several laser beams on a nanoparticle, heating it to locally extreme temperatures. An Alcubierre metric can be created by ejecting multiple nanoparticles from the craft and then beam perfectly timed laser beams on them (fire at the most distant first so that they are

hit simultaneously), so each nanoparticle contributes a slower than 

light effect but together add up to faster than light, creating no discrete event horizon and thus no Hawking radiation. — Preceding unsigned comment added by 109.58.249.18 (talk) 08:24, 29 July 2011 (UTC)‎

Gravitic Cloaking

The Alcubierre drive would need to be tweaked only slightly to make the ship disappear from the local gravity field, wouldn't it? 69.196.167.37 (talk) 06:19, 29 January 2012 (UTC)

Star Trek graphic

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)

Star Trek graphic location

I found the Star Trek diagram on a different website so it is somewhat legitimate, but it should still be referenced. Some of the material used in the main article looks as though it came from this website. The website is http://www.zamandayolculuk.com/cetinbal/HTMLdosya1/AlcubierreWarpDrive2.htm Tathar Lenwe Felagund (talk) 23:05, 15 December 2008 (UTC)

It is quite obvious that that webpage is copied from Wikipedia so has no bearing on this discussion. In any case it does not help with either the origin or notability of the diagram. I propose removing it from the article as unwanted cruft. SpinningSpark 18:42, 17 December 2008 (UTC)

Star Trek

Okay, so now we have no mention of Star Trek in the article AT ALL, even though this popular series was in my opinion the biggest contributor to popular knowledge of warp. I propose mentioning it at least, with some erudite commentary at better.--85.71.203.5 (talk) 02:46, 23 February 2012 (UTC)

I suggest you go find quality references which verify your opinion is notable before you do any such thing. SpinningSpark 07:33, 23 February 2012 (UTC)

Theories of Everything to model foundations of warping space/time

James Dunn 15:41, 7 June 2012 (UTC)

Is it appropriate to post theories about how the warping of space/time can be achieved?

http://en.wikipedia.org/wiki/User:Qesdunn/sandbox — Preceding James Dunn comment added by Qesdunn (talk • contribs) 15:39, 7 June 2012 (UTC)

No, unless such theories have been published in reliable sources. In any event, they would not be appropriate on the Alcubierre drive page unless they related directly to that subject. I will say some more on your talk page. SpinningSpark 18:14, 7 June 2012 (UTC)

Star Trek comparison in the first paragraph

It seems like an exercise of pointless intellectual masturbation to put a comparison to the Star Trek warp drive in the initial sentence. It should be moved to a popular culture section all the way down the article instead. It'd be like making the initial sentence to the article about general relativity saying that it is also applicable in the Star Trek universe, or pointing out in the article about penises that it resembles my penis. 81.71.164.202 (talk) 17:17, 29 May 2011 (UTC)

Alcubierre was inspired by Star Trek, so no. — Preceding unsigned comment added by 71.167.69.211 (talk) 01:11, 19 September 2012 (UTC)

Coaxial Warp Drive

Couldn't this theoretical drive be compared to the coaxial warp drive mentioned in Star Trek Voyager than folded space in front of the vessel? — Preceding unsigned comment added by 98.190.137.61 (talk) 18:32, 19 October 2012 (UTC)

Not in the article it can't. It would be like comparing a theoretical 1000MW plasma drive to the horses that pull Apollo's chariot.168.156.41.220 (talk) 21:40, 8 November 2012 (UTC)Nydoc

valid solution

I have tried to resolve the to-and-fro of the word "valid" in the lede by adding a more in-depth explanation of the situation. Here is what I have added,

The metric proposed by Alcubierre is mathematically valid in that it is consistent with the Einstein field equations. However, this does not necessarily mean that is it physically meaningful or that such a drive could be constructed. The proposed mechanism implies a negative energy density and thus requires exotic matter. The existence of such matter is still an open question in experimental physics although some theoretical models which go beyond the Standard Model require it to exist.

It is highly misleading to say that the solution is valid without some qualifying remarks. A valid solution of the field equations can be found for almost any situation one cares to imagine, even when the laws of physics are blatantly contradicted. BenRG explained this very well previously on this talk page. SpinningSpark 16:18, 30 December 2012 (UTC)

Causal disconnection does not require pre-built infrastructure.

The claim that the causal disconnection between the craft and the distortion should require a pre-built "warp highway" to accomplish Alcubierre drive ignores the possibility of deliberately making the Alcubierre metric unstable. Its lifespan can be tuned to make it predictably desintegrate at the intended destination. This is explained in greater detail on the page "Warp drive" on Pure science Wiki, a wiki devoted to the scientific method without interference from academic prestige-think. 79.138.219.245 (talk) 15:21, 6 January 2013 (UTC)Martin J Sallberg

On this wiki however, we require reliable sources. SpinningSpark 19:27, 6 January 2013 (UTC)

Voyager I

I am pretty sure that Harold White never intended the comparison to Voyager I to be taken as a three-figure accurate estimate. Also, using his exact analogy (Jupiter to Voyager I) is getting damn close to a copyvio and we really would be better off saying "less than a ton". Thankyou. SpinningSpark 00:42, 7 January 2013 (UTC)

Indeed, you're right that those are not significant figures. I don't see how using the analogy while citing the source could amount to copyvio, and in any case the comparison with Voyager 1 is also used in another source. --JorisvS (talk) 01:05, 7 January 2013 (UTC)

Recent addition and subsequent deletion in science fiction

In reference to the recent deletion by Spinningspark in the Science Fiction section, The direct quote from the Futurama episode A Clone Of My Own is as follows. Cubert: "I understand how the engines work now, the ship doesn't move at all. The ship stays where it is and the engines move space around it." Which, though very simplified, is a valid definition of an Alcubierre Drive. --XVILLAINX (talk) 04:04, 18 April 2013 (UTC)

Where do I start with that? Try WP:OR, WP:SYNTH, and WP:PRIMARY for starters. But more than that, we simply do not want a random list of works that have happened to mention Alcubierre drive, or even worse in this case, have mentioned something that sounds like it might be Alcubierre drive. The bus article does not include a list of works of fiction that mention bus, the dress article does not list every Mills and Boon book that mentions dress. List of works of fiction mentioning Alcubierre as a standalone article would probably not survive deletion very long. If you have a WP:RS that discusses Futurama's use of Alcubierre in an out-of-universe setting then there may be a case for including it, but until then, no. SpinningSpark 08:15, 18 April 2013 (UTC)

Appropriate to tag assertion of no evidence with "Citation Needed"?

The last sentence of the section "Albucierre Metric" alleges that there is no evidence of a solution to either of two remaining problems. It's tagged Citation Needed. But what it is alleging is that it is not possible to provide a citation supporting a solution. There's no way to satisfy the citation request.

Is it better to flag the unsubstantiated claim (perhaps a better search might yield an obscure paper?) or to remove the citation as impossible to satisfy? — Preceding unsigned comment added by 70.48.192.155 (talk) 02:38, 18 June 2013 (UTC)

It asks for a source that says that there is no known solution, not for a source that gives one. --JorisvS (talk) 09:38, 18 June 2013 (UTC)

I edited out the statement in question, "No known method can create a warp bubble in a region that does not already contain one or allow the ship to exit the warp bubble after reaching a destination", because I found some sources that explicitly contradict it, indicating that both of these should be theoretically possible in general relativity. The claim about not being able to create a bubble is contradicted by this paper which says in the abstract that they investigate "the more realistic case in which a superluminal warp drive is created out of an initially flat spacetime", with the mathematical details of this case given in the "Dynamic Superluminal Warp Drive" section that begins on p. 4. The part about the bubble being impossible to exit is contradicted by the "massive particles" section on p. 3 of this paper which talks about massive particle entering and exiting the bubble. Hypnosifl (talk) 21:24, 6 August 2013 (UTC)

On the first of those two papers, looking at it more closely it seems like their dynamical warp drive spacetime is not actually a fully analytic solution, as they refer on p. 12 to it involving a "computational trick" and say it "allows one to carry out an almost complete analytical treatment." It might be true that there are no analytic solutions for a warp bubble forming dynamically, although I don't think we should add that unless we find a source saying so explicitly. Hypnosifl (talk) 23:15, 6 August 2013 (UTC)

NASA Eagleworks

Interesting news coming out of NASA today... http://gizmodo.com/5942634/nasa-starts-development-of-real-life-star-trek-warp-drive

Apparently, the folks there are looking into measuring warp bubbles, and decreasing the energy requirement to create them. iac74205 (talk) 03:46, 18 September 2012 (UTC)

I can't find any firm sources for this statement, other then a few sensationalist blogposts. Furthermore, the section about this in the article ( currently titled "Recent Discovery Revealed Suggests That Significantly Less Energy Than Proposed By Alcubierre's Theorum Is Required To Achieve Warp Travel") is poorly named and a barely edited copy from the space.com article it references. I think this section should be edited, trimmed and renamed, and probably point to the fact that no firm data or academic work is currently published to support these claims. If noone disagrees, I will make the changes in a few days. wvdschel (talk) 07:34, 19 September 2012 (UTC)

Last year's 100YSS presentation is located at NASA site. (http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110015936_2011016932.pdf) contains explanation and presentation slides from Dr Harold White. This years presentation with new claims is yet to be made public. --Mqmpk (talk) 10:30, 19 September 2012 (UTC)

I just wanted to urge someone more familiar with the research to update this page with Dr. White's potential reassessment of the energy requirements. (talk) 17 December 2012 — Preceding unsigned comment added by 206.18.112.127 (talk) 22:05, 18 December 2012 (UTC)

Did you not read the paragraph that begins "In 2012, physicist Harold White..." SpinningSpark 00:14, 19 December 2012 (UTC)

I read White's "General Relativity and Gravitation" paper "A Discussion of Space-Time Metric Engineering" which he refers to in his current work (Gen. Rel. Grav. Vol. 35, No. 11, Nov. 2003, pp. 2025-2033). Much to my surprise this paper is 99% nonsense, basically all of its main claims are false (the claim of spaceship's x-direction lack of bias is false, the "canonical form" metric is incorrect, the "gravitational potential" is nonsensical, the terminology he uses is inappropriate, etc.) I have no idea how this paper passed the peer review. Also, as far as I can make it, his contribution mentioned in the main article about reducing the energy requirement is just a trivial observation regarding the influence of the sigma parameter regulating Alcubierre's "top hat" function. White is most likely an excellent engineer but he does not understand general relativity.JanBielawski (talk) 09:19, 1 January 2014 (UTC)

York time

There is no discussion of the York time equation for expansion/contracton of space nor can I find that anywhere on Wikipedia. York time was mentioned in Harold White's paper "The Alcubierre Warp Drive in Higher Dimensional Spacetime" here http://www.earthtech.org/publications/davis_STAIF_conference_2.pdf and apparently by Alcubierre as well. I'm not going to mess with the article to add it in, but I think it should be added. The equation is theta = Vs/c * (Xs/Rs) * df/dRs Netdragon (talk) 01:48, 7 January 2013 (UTC)

The equation for theta in Alcubierre's preprint has a typo (repeated by Harold White who IMHO does not understand the subject), it should read (in the units of G = c = 1): theta = Vs * (X - Xs)/Rs * df/dRs JanBielawski (talk) 09:23, 1 January 2014 (UTC)

Sigma

Sigma (σ) is not explained in the set of equations... 24.37.29.254 (talk) 17:32, 18 June 2014 (UTC)

Yes it is. It's just an arbitrary parameter. SpinningSpark 08:26, 19 June 2014 (UTC)

Definition of Mathematical Variables

The first equation under the heading "Mathematics of the Alcubierre drive" replicates Alcubierre's Eq. (1) in his 1994 paper [34]. The following text repeats his definition of "beta sup i" ( βⁱ ), but does not define "beta sub i" ( β_i )

A possible clarification is found in Eq. (4.40) in this 2007 paper:

http://arxiv.org/pdf/gr-qc/0703035v1.pdf

β_i = γ_ij β^j . (4.40)

Alcubierre's 1994 paper [34] doesn't seem to supply this definition either.

Banchang (talk) 22:56, 23 October 2014 (UTC)

Conformal Gravity and the Alcubierre Warp Drive Metric

http://www.hindawi.com/journals/isrn/2013/482734/

All studies of the Alcubierre Metric using standard GR and could not avoid the violation of the WEC, meaning that some exotic matter would always be required. Solving the Alcubierre Metric using Conformal Gravity doesn't violate WEC & doesn't require exotic matter.

I find this very interesting and wish to add this paper to See also Oops just noticed, See also only references wikipedia pages.

Someone with better understanding of the math should read this and add a section on it to the page. imho NHa879 (talk) 23:39, 7 November 2014 (UTC)

It can simply go in the External links section. I've added it. --JorisvS (talk) 23:56, 7 November 2014 (UTC)

Scale

The article states: "According to Pfenning and Allen Everett of Tufts, a warp bubble traveling at 10 times light-speed must have a wall thickness of no more than 10⁻³² meters. This is only slightly longer than the Planck length, 10⁻³⁵." Although both are very tiny compared to human experience, a 10⁻³²-meter wall is one thousand times thicker than a 10⁻³⁵-meter wall. What the article says is no different from saying that a kilometer is "only slightly longer" than a meter. — Preceding unsigned comment added by 174.24.229.199 (talk) 12:39, 3 July 2011 (UTC)

Sure, the values differ by 3 orders of magnitude, but I feel like it still makes sense, 10⁻³²metres is incredibly small, the most powerful microscope we have right now has a resolution of merely 1.5 × 10^-11metres, half the size of a hydrogen atom, differing by 21 orders of magnitude, another way to look at it is using the visualisation trick found in the Planck length article:

"If a particle or dot about 0.1mm in size (which is at or near the smallest the unaided human eye can see) were magnified in size to be as large as the observable universe, then inside that universe-sized "dot", the Planck length would be roughly the size of an actual 0.1mm dot."

The warp bubble's wall thickness in that universe-sized "dot" would be about 10cm long, considering the scenario, that does seem pretty close to the 0.1mm dot I think.

Your 1m-1km comparison can also be put in a different perspective when you write down the lengths as double exponentials, 1 metre could be written as 10^10-∞ metre, 1 kilometre is around 10^100.477m, 10^-32m ≈ 10^-101.505m, and 10^-35m ≈ 10^-101.544m. I think there's a substantial difference between 0.477 and minus infinity, and that there's only a slight difference between 1.505 and 1.544.

I also like the "...is no different from..." part in your last sentence, the difference between 1 metre and 1 kilometre is 999 metres, a big difference, the difference between 10⁻³²m and the Planck length is about a millionth of a septillionth of a centimetre, a very tiny difference.

Anyway, I noticed someone changed it to "close to" rather than "slightly longer", which is perhaps slightly less subjective.— Ultrasu (talk) 08:54, 28 November 2014 (UTC)

Personal opinion of proponents are not reliable sources, and certainly not encyclopedic

"recently White calculated what would happen if the shape of the ring encircling the spacecraft was adjusted into more of a rounded donut, as opposed to a flat ring. He found in that case, the warp drive could be powered by a mass about the size of a spacecraft like the Voyager 1 probe NASA launched in 1977."[1]

Has this calculation been peer-reviewed, or published in a specialist secondary source with a reputation for fact-checking and accuracy by domain experts? If not, the claim should not be written as a fact in Wikipedia's voice. 63.228.180.122 (talk) 03:04, 30 December 2014 (UTC)

I'm not giving an opinion, at least for the moment, on whether this should stay, but it is hardly in Wikipedia's voice. It is clearly attributed to White. SpinningSpark 10:33, 30 December 2014 (UTC)

I mean in this Wikipedia article, not the quote from the source cited. 63.228.180.122 (talk) 06:22, 1 January 2015 (UTC)

The article attributes it all to White as well. This research is at NASA's Johnson Space Center for crying out loud. The fact that NASA are funding this, by itself, makes this notable and worthy of including in the article in my book. If this was unpublished work by some independent I would probably dismiss it as WP:FRINGE and non-notable, but NASA's involvement, and the degree of coverage that has got, puts an entirely different light on it. SpinningSpark 12:20, 1 January 2015 (UTC)

A correction to the introduction

The phrase “Rather than exceeding the speed of light within its local frame of reference…” doesn't make sense. The speed of anything in its own local reference frame is zero, by definition. I've changed it to “Rather than exceeding the speed of light in a local inertial frame…” Ericlord (talk) 07:49, 13 January 2015 (UTC)

History Section - Non-violation of Relativity

"Thus, the mathematical formulation of the Alcubierre metric does not contradict the conventional claim that the laws of relativity do not allow a slower-than-light object to attain speeds greater than that of light."

For those on the outside of this bubble - in an inertial frame which contains the start (A) and end (B) of the bubble's trip let's say - is not a signal being sent FTL? Does this not lead to the usual time-travel causality problems? — Preceding unsigned comment added by MistySpock (talk • contribs) 03:28, 29 December 2012 (UTC)

Time-travel paradoxes only occur when actually travelling through time or locally FTL, neither of which occur. General relativity does allow FTL, just not locally. An example is that the observable universe is far larger than 13.75 Gly, without violating general relativity (i.e. no FTL locally) and without time-travel paradoxes. --JorisvS (talk) 10:04, 29 December 2012 (UTC)

It sounds like this FTL device definitely has "local" FTL implications. Given spacelike events A & B, any intentional FTL signal (such as via a human-made Alcubierre device) between them implies the possibility of sending a signal backward in time. Generally, model demonstrations that FTL signaling implies time-travel paradoxes involve multiple intertial frames. MistySpock (talk) 15:00, 30 December 2012 (UTC)

How? --JorisvS (talk) 15:11, 30 December 2012 (UTC)

As the very quickly moving train comes through my station, I push a button on the back of the train as it passes me. On the train, an FTL (train frame) signal is sent from the back to the front of the train. A sensor at the front of the train receives the FTL (train frame) signal from the back and sends out a spark a miniscule distance to a sensor further up the platform where I'm standing. This triggers an FTL (platform frame) signal from that point on my platform to a bomb where I am standing. If you do the SR math, you find out that the combination of FTL in these two different intertial frames leads the bomb detonating right under me before I push the button initially. Voila. Causality paradox. Recall that simultaneity is relative, and that the evident contraction of a moving object can be described as a situation where the clocks at the front and end of it being "out of synch" from my perspective, much like a parade where the floats in the back are "ahead of schedule" thus "bunching up" the train of floats. The speed of light is nature's way of keeping everything from happening at once. Long story short, you can see all the arguments that occurred to me being made consistently and insistently by an MIT grad student here - he is nessus42 in this conversation: http://news.ycombinator.com/item?id=4535149 -- MistySpock (talk) 15:39, 30 December 2012 (UTC)

The paradox you describe is not possible with an Alcubierre drive since the inside of the bubble is causaly disconnected from the outside. A sensor within the bubble cannot be triggered by any external event. Consequently the remainder of your scenario cannot happen. Inertial frames only have any meaning when all possible inertial frames are linearly related, at least approximately (see Inertial frame of reference). This is most certainly not the case when comparing frames across the bubble boundary. SpinningSpark 15:50, 30 December 2012 (UTC)

You are definitely connecting the inside with the outside when you put a person or a message inside it and send it on it's way. You are also doing so when the message or person is extracted from the bubble at the end. The real issue related to causality violations has nothing to do with the *process* - with what happens *during* the travel. All educated physicists understand that FTL implies the possibility of causality violations. Note that the SR violations of the expanding universe do not allow a person to send a signal FTL between two locations. Please read the learned comments of MIT Grad Student nessus42 referenced above. --MistySpock (talk) 15:58, 30 December 2012 (UTC)

Putting a person or message inside the bubble is, of course, one of the "practical" difficulties of the scheme, it can't be done. From the point of view of the platform, you cannot observe anything happening in the train because of the causal disconnect. You cannot press any button that is connected to the inside and there can be no local FTL inside the bubble in any case. SpinningSpark 16:28, 30 December 2012 (UTC)

Putting this in another way, general relativity is an excellent padlock to such a violation.--Pra1998 (talk) 19:17, 30 December 2012 (UTC)

The idea of a "drive" using a warp bubble is that you can and do in fact create the bubble and put a person or message inside of it before sending it along its way. As for the SR model with the train and platform, we are not interrupting a warp bubble to place a signal inside it en route. Rather, on board the train, an FTL method such as this drive is used to send the FTL message to the other end of the train (no need to interrupt it en route). A 2nd message is being sent FTL (such as by the drive) from one end to the other of the platform (again, no need to interrupt it en route). Please read the above exchanges at the link specified. -MistySpock (talk) 19:00, 31 December 2012 (UTC)

Lucky this article isn't about an SR train then isn't it. You continue to apply SR to a domain in which it is no longer valid. SpinningSpark 20:39, 31 December 2012 (UTC)

SR applies everywhere we can go to or come back from. Really if you check into it, you'll find out that educated physicists admit that wormholes or warp drives actually do get us into causality-violation territory. Please don't take my word for it. As an exercise, you might try looking for somebody with a physics degree and get a quote stating otherwise. You won't be able to. SR causality issues apply to situations/events *outside* a wormhole, *outside* a region where such a drive is in operation. Quantum correlations appear to violate FTL but they cannot be used to send *intentional information* FTL - thus no causality paradoxes. GR cannot be used to intentionally send signals FTL so no causality paradox. I have nothing special to contribute. "General relativity also agrees that any technique for faster-than-light travel could also be used for time travel." - http://en.wikipedia.org/wiki/Faster-than-light#Give_up_causality . Anyhow - happy reading. Have you read this? What do you think? http://www.physicsguy.com/ftl/html/FTL_part4.html --MistySpock (talk) 20:10, 5 January 2013 (UTC)

Differently from the case of time machines, initially proposed by Kip Thorne&Coll., for Alcubierre drive there is no causality violation implied and this is well-known to all respectable people that worked on it in the course of the years after its proposal. Of course, if you believe that all this people is in error you are free to do the same they did: Rather than bother Wikipedia's editors, write down a paper and send it to a reputable journal. Scientific community will surely recognize your merit if what you are claiming is sound. This will also permit to NASA to save a few bucks they are investing on all this business.--Pra1998 (talk) 21:17, 5 January 2013 (UTC)

The paper was written shortly after the original Alcubierre paper: http://exvacuo.free.fr/div/Sciences/Dossiers/Time/A%20E%20Everett%20-%20Warp%20drive%20and%20causality%20-%20prd950914.pdf and it was published in a reputable journal. The method proposed there does use two different bubbles but it does not make any assumptions other than those in the original paper in order to violate causality and create paradoxes. Fgl007 (talk) 10:25, 26 March 2013 (UTC)

SR applies everywhere we can go to or come back from. Not so, SR applies only to inertial frames and the Alcubierre bubble is decidedly not an inertial frame. SpinningSpark 21:03, 6 January 2013 (UTC)

MistySpock is right. The Alcubierre drive does violate causality. Place a message at a point A in a flat spacetime. Create an Alcubierre bubble around it. Let it travel to a point B. Then switch off the Alcubierre drive. The spacetime is the flat spacetime of special relativity everywhere except in a region enclosing the worldline of the bubble. We can apply special relativity to the spacetime surrounding that region. The net result is a violation of causality because in any inertial frame the event B occurs before event A; the message has been sent back in time. Ericlord (talk) 07:32, 13 January 2015 (UTC)

The most important flaw in MistySpock's argument is that it tackles motion from a "classical" point of view. With an Alcubierre drive nothing is moving: the momentum of the object remains zero or very low. I'm not sure I get your argument, though. If the spaceship goes back to A, it can only arrive there later than it left, from both the local A point of view as from that of the spaceship. From what inertial frame does it look like a causality violation and how? --JorisvS (talk) 19:33, 13 January 2015 (UTC)

Solution of the field equations

The article, in its current state, makes two contradictory statements.

The first sentence is: "The Alcubierre drive or Alcubierre metric is a speculative idea based on a solution of Einstein's field equations in general relativity"

The second paragraph in Physics contains the sentence: "This may explain the widespread misconception that this spacetime is a solution of the field equation of general relativity."

It would be nice if this could be resolved. As I understand it, the first statement is correct and the second statement is incomplete. — Preceding unsigned comment added by 78.55.209.203 (talk) 18:34, 30 May 2015 (UTC)

Not physically meaningful

@RoyGoldsmith:. Your attempts to reword this sentence seem to show a complete misunderstanding of what it is supposed to say. In this edit you wrote "... that metric may indicate that the resultant drive could not be constructed or even that the metric is not physically meaningful." This is twice wrong. The metric does not (and cannot) indicate that itself is not physically meaningful, that is a matter for experiment to determine. Nor does it indicate that the drive cannot be constructed. The mere existence of the metric indicates that a drive might be possible, it tells us nothing about whether that actually is possible. Please explain what problem you are trying to fix in your edit because it is passing me by at the moment. SpinningSpark 06:54, 17 June 2015 (UTC)

@Spinningspark: Sorry, I've been away most of today and this is my first chance to answer your post.

My edit was almost entirely grammatical. Originally, the article said:

Although the metric proposed by Alcubierre is mathematically valid in that it is consistent with the Einstein field equations, it may not be physically meaningful or indicate that such a drive could be constructed. [underlines mine]

This sentence may be split up into a condition (everything before the comma) and a compound action or belief (after "it may"). The meaning of the compound action; that is, "it may not be physically meaningful or indicate that such a drive could be constructed" is unclear. Should the conjunction or (the exclusive or; only one or the other sub-actions is true) by changed to and/or (inclusive) or and? And should the not be replicated in the second sub-action as well? The problem is that the single not may include both sub-actions or it may only apply to the first. The original text doesn't say which.

To break it down, does the original sentence above mean:

Although the metric proposed by Alcubierre is mathematically valid in that it is consistent with the Einstein field equations, it may not be physically meaningful. -AND-

Although the metric proposed by Alcubierre is mathematically valid in that it is consistent with the Einstein field equations, it may indicate that such a drive could be constructed. [Both must be true.]

Or does the original mean:

Although the metric proposed by Alcubierre is mathematically valid in that it is consistent with the Einstein field equations, it may not be physically meaningful. -OR-

Although the metric proposed by Alcubierre is mathematically valid in that it is consistent with the Einstein field equations, it may indicate that such a drive could be constructed. [Only one is true. This is the straight Boolean interpretation of the original sentence.]

Or this:

Although the metric proposed by Alcubierre is mathematically valid in that it is consistent with the Einstein field equations, it may not be physically meaningful. -AND/OR-

Although the metric proposed by Alcubierre is mathematically valid in that it is consistent with the Einstein field equations, it may indicate that such a drive could be constructed. [At least one is true.]

On the other hand, the grammatical problem might be the not phrase:

Although the metric proposed by Alcubierre is mathematically valid in that it is consistent with the Einstein field equations, it may not be physically meaningful. -AND, OR or AND/OR (see above)-

Although the metric proposed by Alcubierre is mathematically valid in that it is consistent with the Einstein field equations, it may not indicate that such a drive could be constructed.

My guess is that it's the fourth one with an AND; that is, both beliefs are and must be true. However, any of the four meanings above is acceptable to me. (I assume you will rephrase to eliminate the redundancy. Remember that, if you use am overriding not phrase -- that is, applying to both sub-beliefs: not A and not B converts to not A or B -- the logical AND will invert to a grammatical OR, per DeMorgan's law.) Or, to rephrase the fourth meaning:

Although the metric proposed by Alcubierre is mathematically valid in that it is consistent with the Einstein field equations, it may not be physically meaningful and also it may not indicate that such a drive could be constructed.

If neither of the four meanings work, please state whatever does work, splitting up the separate clauses as I have done ("not be physically meaningful" vs. "indicate that such a drive could be constructed"), paying particular attention to the inversions (whether the not should appear and where).

Thanks for all your help. I really don't understand anything above freshman physics. --RoyGoldsmith (talk) 02:08, 18 June 2015 (UTC)

That's an incredibly long post on a simple point so I haven't read it all but it mostly seems to be explaining basic logic (grandmother, eggs). The metric may not be physically meaningful, in which case a drive will not be possible. Even if it is physically meaningful, its mere existence does not necessarily mean that a drive can be constructed (see the objections of Krasnikov etc). Does that make it clear? SpinningSpark 06:50, 18 June 2015 (UTC)

Sorry. I had to think it through on paper. Do you think we can substitute your two sentences for the original. It would read like this:

"Although the metric proposed by Alcubierre is mathematically valid in that it is consistent with the Einstein field equations, it may not be physically meaningful, in which case a drive will not be possible. Even if it is physically meaningful, its mere existence does not necessarily mean that a drive can be constructed."

Optionally, you can add: "(See the objections of Krasnikov etc.)." Please note that Krasnikov contains a WP:Piped link. --RoyGoldsmith (talk) 13:33, 18 June 2015 (UTC)

Looks good to me (as I wrote it, it would, wouldn't it?). I don't think it's necessary to explicitly mention Krasnikov. There are others who think some of his objections can be overcome and there are others who have raised further problems. This is gone into in detail in the article body and is best left out of the lead except in very general terms. SpinningSpark 14:00, 18 June 2015 (UTC)

Done. It's been very nice working with you. --RoyGoldsmith (talk) 20:13, 18 June 2015 (UTC)

Time travel

In the introduction

"... some physicists have presented arguments to suggest that a theory of quantum gravity (which would incorporate both theories) would eliminate those solutions in general relativity that allow for backwards time travel (see the chronology protection conjecture) and thus make the Alcubierre drive invalid"

it is suggested that the Alcubierre solution allowes closed timelike curves, i.e. "backward time travel".

Is this true?

In a later section the article specifies the Alcubierre metric; it is said that

"using the ADM formalism of general relativity, the spacetime is described by a foliation of space-like hypersurfaces of constant coordinate time t, with the metric taking the following general form ..."

But a complete foliation of the Alcubierre spacetime means that it is globally hyperbolic which rules out any closed timelike curve. So based on global hyperbolicity the sentence in the introduction is misleading: if "backward time travel" is ruled out, this does not imply that the Alcubierre solution is ruled out (b/c the Alcubierre solution itself rules out "backward time travel").

I suggest to delete the sentence from the introduction. — Preceding unsigned comment added by 87.163.253.71 (talk) 13:28, 20 August 2015 (UTC)

Newton or Lorence dialog

One of them said "If the light speed eq.300000 km/sec so the Gravity of the Moon to Earth (or ever gravity in Space) transmitted with 50 000 000 000 km/sec az a minimum! Soo, the bubble is the ordinary Space-time "jump" to "assamble" position when HERE makes multysepareted, with new local light wind))! Is the Bubble (and it metric) mean our spaceship nowhere "have" moving?! If 50bln km/s - is very very slowly speed in Preinflation Time? If we may have exoenergy for making a bubble when teleported all human on a board?? Like's (entangled) quantum heat?? 188.187.28.10 (talk) 22:07, 17 September 2016 (UTC)Smir^

References to Khamehchi et al.'s "negative mass" paper

The recent edits to the paper "Negative-Mass Hydrodynamics in a Spin-Orbit–Coupled Bose-Einstein Condensate" by MA Khamehchi et al. (Phys Rev Lett 118, 155301 (2017)) represent an egregious misunderstanding of the concept of negative *effective* mass as described in that paper, which is entirely inapplicable to the Alcubierre drive. I'm reverting all the edits by Tex.Bold from 17 April 2017.

Episanty (talk) 19:37, 18 April 2017 (UTC)

Unreliable sources

I just found one completely misrepresented source, and suspect there are others. This article needs a good, thorough checking to remove fringe theories and other nonsense. Please leave the maintenance template in place until that's done. Jehochman ^Talk 03:40, 3 May 2017 (UTC)

@Jehochman: A banner template is a bit over the top here. I have previously looked carefully at the sources in the "Difficulties" section while reworking it and am pretty sure that the sources there are solid. I also cleaned out a lot of popular culture stuff. In short, the majority of this article is not problematic. If you have specific concerns, they can be looked at, but otherwise I think the banner should go. SpinningSpark 17:48, 3 May 2017 (UTC)

Please check the entire article and if you remove any remaining junkfeel free to remove the banner. I found one grossly misrepresented source. There could be others. Jehochman ^Talk 07:17, 4 May 2017 (UTC)

As I said, I am alredy familiar with much of the material. The IP that generated the hoax has not made any other edits. There is really no justification for a banner warning. I believe it is all good. SpinningSpark 16:31, 4 May 2017 (UTC)

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Should this be called a drive when it's not?

And when it's own creator has state it's not a drive, it's not a ship, it's nothing but a concept in an interview (YT JafY92PhgKU?t=912 ) 121.210.33.50 (talk) 15:34, 10 June 2019 (UTC)

WP:COMMONNAME? What do you suggest as a title? SpinningSpark 17:54, 10 June 2019 (UTC)

Why works of Fernando Loup weren't even mentioned?

In 2014-2015 he made some calculations with modified warp metrics proposed by Jose Natario and the calculations resulted in solution of three main huge problems of warp engine: 1) Blue shift - interaction of warp bubble with interstellar media resulting in Hawking radiation;

2) Density of negative energy - Loup's metric leads to diminishing of required energy density by 55 orders of magnitude in comparison with Natario metric;

3) Horizon problem - the very warp engine is inaccessible from inside the warp bubble because all the particles have their geodesic nullified on horizon so that it looks infinitely distant from inside. The solution is to enclose the 'control' particles say electrons inside microscopic warp bubbles so that their geodesic becomes 'protected' from nullification. — Preceding unsigned comment added by 79.120.76.21 (talk) 17:51, 28 September 2019 (UTC)

As of sig date to this, some of Loup's work on the Natario drive is now included in this article. Please help expand. Johncdraper (talk) 07:50, 14 May 2020 (UTC)

Dark energy/matter

@Scienceblackbelt and Bmf 051: Does Farnes (or anybody) relate dark energy/matter to a possible Alcubierre drive? The Farnes paper doesn't touch on it at all, or through any pseudonym or related concept. The only other sentence that mentions Alcubierre drive in the passage is cited to a paper that is a critique of Farnes. It seems unlikely that this paper will be discussing Alcubierre drive either; there is certainly no hint of it in the abstract.

You are right that this should not have been removed as speculative, but you were wrong to reinstate it nonetheless. It has no (verifiable and citable) connection with the subject of this article. That makes the association with Alcubierre drive WP:SYNTH. This has a place somewhere on Wikipedia, but it should be removed from this article. SpinningSpark 20:23, 28 August 2020 (UTC)

I've just taken a read through the article. For starters, it's negative mass dark energy and dark matter that enables luminal-speed travel. That is very clearly the Alcubierre drive. The paper by Farnes seems pretty clear on it being related to acceleration to the speed of light:

"One of the more bizarre properties of negative mass is that which occurs in positive–negative mass particle pairs. If both masses have equal magnitude, then the particles undergo a process of runaway motion. The net mass of the particle pair is equal to zero. Consequently, the pair can eventually accelerate to a speed equal to the speed of light, c. Although counterintuitive and “preposterous” (Bonnor 1989), all of these behaviours violate no known physical laws. Negative masses are consistent with both conservation of momentum and conservation of energy (Forward 1990)."

On top of that, the paper by Navarro that is a critique of Farnes paper directly relates the dark energy/matter theory to that of Alcubierre, so in contrast to your suggestion, it does have a directly verifiable and citable connection with the subject of this article, and so should clearly remain:

"If negative masses exist then it would be possible to build an Alcubierre drive (Alcubierre 1994). Such a device would enable faster-than-light travel and, in consequence, closed time-like-loops, that is, the possibility to travel back in time (see, e.g. Everett & Roman 2012)."

86.11.126.81 (talk) 13:36, 20 September 2020 (UTC)

Please update with: "Breaking the warp barrier: hyper-fast solitons in Einstein–Maxwell-plasma theory"

Could you please integrate some information on this study into the article? It's currently featured in 2021 in science like so:

A physicist describes a way warp drives sourced from known and familiar purely positive energy could exist – warp bubbles based on superluminal self-reinforcing "soliton" waves. It may allow for up to faster-than-light speed travel, transfers and communication with the large energy requirements possibly being reducible.

I also added some short info on it to Warp drive#Real-world theories and science which you could edit.

--Prototyperspective (talk) 11:19, 1 May 2021 (UTC)

References

Again Harold White and his claims

Again Harold who previously claimed to violate Newton's laws is now claiming to have made a warp bubble. So let's see if his researches and claim really deserve to be in the lead. Even guy who first proposed this stuff doubt Harold "results". https://bigthink.com/starts-with-a-bang/no-warp-bubble/ https://twitter.com/malcubierre/status/1469139340756455433?s=20 — Preceding unsigned comment added by 93.86.200.213 (talk) 15:20, 10 December 2021 (UTC)

No, they don't deserve to be in the lede. Or in the article. WP:PRIMARY, WP:FRINGE, WP:UNDUE, WP:WE-DON'T-CARE-HOW-MANY-TIMES-YOU-SAY-DARPA. XOR'easter (talk) 16:39, 10 December 2021 (UTC)

I agree, seems article needs further check and to be kept on eye. This is an encyclopedia not a list of claims, and things that are not accepted in the wide academic community. 93.86.200.213 (talk) 16:44, 10 December 2021 (UTC)

Relevant here?

The following content by User:Mark McWire was removed from space travel in science fiction, but could be of use here, perhaps: [2]. Or perhaps it belongs at warp drive? _{Piotr Konieczny aka Prokonsul Piotrus| reply here} 10:40, 14 December 2021 (UTC)

I don't know what you think can be used here. The Alcubierre drive is not fictional, it is an unproven theoretical possibility. There is nothing in that edit not already said in the article and the source cited is already present. SpinningSpark 09:36, 15 December 2021 (UTC)