This is about the question Which is more feasible: Wormholes or an Alcubierre Drive?, which was closed by community vote as "primarily opinion-based".

I honestly fail to see what's primarily opinion-based about it. To my mind, it's definitely not any more opinion-based than many other questions on the site, and one can make a quite reasonable argument that it is less so than many, even recent ones, which remain open.

Both hypotheses being asked about, while to my knowledge neither has been proven, have a somewhat solid foundation in the sciences. Both are studied and considered by some pretty smart people, so there should be citable material available, possibly even to the level of (which this question is not). The fact that neither is currently practical doesn't mean that no work has been done to establish how they might function. Science often works by determining the theoretical model long before practical experiments are made or even possible; it also often works by trying to figure out how newly observed data can fit with existing observations in a new model. There is no inherent contradiction in doing one before the other.

The OP specifically specifies "with our current knowledge" and also allows for answers saying that the comparison isn't meaningful by also adding at the end "Is it possible to make this type of comparison? If not, why?".

We have already established that "that's not possible" can be an acceptable answer, and even more with reality-check questions (the tag wiki excerpt there even says "Answers should say yes or no, with supporting info.").

"Primarily opinion-based" is about not being able to objectively evaluate answers. I'm not a subject matter expert, but I feel that answers to this question can be judged objectively on how well they answer the question and their factual correctness.

It's not like the OP is asking us to do their work for them. They've come up with two ideas based on relevant scientific study and are basically asking which is the least scientifically implausible, so the problem with "do my work for me" types of questions doesn't really seem to apply. Take Secespitus' answer to another Meta question from back in July:

We will always be a bit opinion-based, but questions should still be written in a way that you can use somewhat objective methods to determine which answer is the "best" answer in the proposed scenario.

Answers can discuss the difficulties of each proposed mechanic, and compare the implications of them; or argue, citing supporting reasoning, that the comparison isn't meaningful.

Or consider SRM's answer to another question from back in January, which seems to me to provide a reasonable, certainly a "rule of thumb", guideline for when primarily opinion-based applies:

I think I have a litmus test for what constitutes a "primarily opinion-based" question.

Ask yourself: "What would a wrong answer to this question be?"

A wrong answer to the OP's question could for example be "Alcubierre drive requires blue cheese, so it's useless after you pass Earth's moon". (Made up example, but you get the idea.) A correct answer could be "both require X which we have absolutely no idea how to do, so neither is more plausible than the other", or "option A requires X, and option B requires Y, and we don't know how to do X but we have a theoretical model for how to do Y, so B is more plausible".

I don't think the question linked at the top of this meta question meets the criteria for primarily opinion-based, but I'm also not inclined to reopen unilaterally by mod hammer. Why was it put on hold as primarily opinion-based?

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    $\begingroup$ I suspect it comes down to "I don't know how to answer this question, so it must be primarily opinion-based." @Frostfyre has given a number of reminders about this and rightly so. $\endgroup$
    – a4android
    Dec 17, 2017 at 4:21

4 Answers 4


The problem isn't with wormholes or Albucierre drives, its with asking either-or.

If you are going to ask how to implement one or the other technology, obviously no one knows, but that is what this forum is for. However, if you are asking us to choose between them, when no one knows any technical pros or cons about them, how is the answer based on anything other than opinion?

In other words, if a technology works because of handwavium (and both techs are definitely in this category), what are the criteria you can use to determine if one handwavium is better than another?

I didn't vote to close, but I won't vote to open either. Any answer will be opinion based, since there is no hard data available on the matter.


Quite simply: coming up with an answer to the question is impossible with current knowledge of physics, according to which, both wormholes and Alcubierre drives require the same sort of negative energy and neither have been made or observed.

In other words, no-one knows whether either is feasible. To make it really clear, the possibilities are:

  • Alcubierre drives are more feasible than wormholes. According to current knowledge of general relativity (GR), wormholes can't just simply form. However, some physicists will disagree with this and say that
  • Wormholes are more feasible than Alcubierre drives, as it's at least potentially possible that wormholes exist according to certain theories of GR, while there's no reasonable way we could get the frankly absurd amount of negative energy required to run a warp drive. Of course, we don't know whether or not the torsion tensor really vanishes or not, although there aren't any hints that it doesn't so far, so
  • Neither is feasible, as both require insane amounts of negative energy. As in, you'd need a Type II civilisation (to current knowledge) to have access to that kind of scale of positive energy, never mind negative energy... Although... Things like the Casimir effect do show the existence of negative energy, so
  • Both are equally as feasible in the long-term, as if a type I civilisation can access trace amounts of negative energy, why can't a type (say) III civilisation access enough to create either a wormhole or Alcubierre drive.

Ultimately, which of the above you believe is down to opinion, hence the question is opinion based.

Having said that, asking which would require less negative energy (according to current knowledge of physics) is something that could actually be answered without requiring (anywhere near as much) opinion. As such, I believe the question should be edited to instead ask this and have commented on the original question saying so. This is a different question to "which is the most feasible?" but at least related and is roughly equivalent to asking "which is the most feasible to have first given the assumption that both are equally feasible in the long term?"

  • $\begingroup$ Well laid out points you have there. But your last paragraph sort of bites you in the neck. If arguing which needs less negative energy would make it on-topic again; then wouldn't it be more prudent to tell the OP that they need to add some sort of quantification to the question / edit the question to add this quantification with a comment that you're a physicist? $\endgroup$
    – dot_Sp0T
    Dec 16, 2017 at 9:39
  • $\begingroup$ @dot_Sp0T There's still a minor issue of 'all this is theory and we don't really know if these models are any good', but that's about as good as we can get :P So, yes, I do think the OP should edit their question to asking which would require less negative energy (and I would have put this in a comment if it didn't get sent to meta before I saw the question). The above is just the reasoning as to why it's currently opinion based $\endgroup$ Dec 16, 2017 at 9:48
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    $\begingroup$ People forget there are two classes of opinion. The first kind is where your opinion is as good as mine, where is no easy criteria for distinguishing between the. The second kind is the professional opinion which is based on the knowledge and experience of the professional giving the advice. The first kind constitutes VTC reasons on this site. Your discussion is concerned with opinions of the second kind. These are outside of the criteria for POB, therefore answers based on them should be acceptable here since they rely on expertise, knowledge & experience. [to be continued] $\endgroup$
    – a4android
    Dec 17, 2017 at 3:57
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    $\begingroup$ In the real-world professional opinions can & do disagree with one another, therefore, if one takes the sensible approach they should be acceptable here. The OP can decide which is right for their answer by accepting an answer with their preferred opinion. Multiple models will result in multiple answers, but that's reality. I do agree there are problems in deciding feasibility between the two FTL concepts. This is speculative territory. Certain degrees of speculation can be allowed to indicate which might be more feasible. Absolute reality not required. $\endgroup$
    – a4android
    Dec 17, 2017 at 4:05
  • $\begingroup$ This is a good discussion of the possible options. It does come down to the different kinds of opinion. Prefer to choose expert opinion instead of blindly accepting opinion as something baseless. I cavil at the concept of feasibility in the long run, because it's outside of current knowledge. Feasibility based on negative energy requirements is little different from the original question, only a slightly refined version of it. Not liking it in one form, but accepting it in another. That's a criterion that could be used to answer the original question unchanged. $\endgroup$
    – a4android
    Dec 17, 2017 at 4:15
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    $\begingroup$ In response to particularly your first paragraph, but also the greater gist of this whole answer, it seems like one could use pretty much the argumentation you use here to make a plausible argument for that the comparison is meaningless, which the OP specifically allows for as an answer. In that regard, the question in question doesn't exactly jump out to me as being any more opinion-based than most of the other [faster-than-light] questions we have on the site. I'm the first one to point out that other open questions don't necessarily make another on topic, but it's a strong hint. $\endgroup$
    – user
    Dec 17, 2017 at 11:03

I'm going to answer the your questions one a time -- this post will deal with what I consider as legitimate answers. Some of these are rehashes of Michael Kjörling 's answers, dot_Sp0T, and a4android in a different light.

kingledion Given that the Casimir effect is valid (everything I have now read suggests that the effect is repeatable and grounded in at least one recognized theoretical framework). How much negative energy is needed to move 1 kg of hydrogen 1 light year given the two drives?

Before I hear, "We look at the operation of the worldbuilding forum here. Not the forum itself." Consider this: The second you answer the above question you have made a scientifically verified conclusion. You therefore cannot call handwavium. I cannot make the meta argument without making the forum argument.

Mithrandir24601 I appreciate the effort you went to in developing this 2 x 2 (or I vs II vs III vs IV) argument and mentioning the torsion tensor issue. However it would be more valuable if you view this in another format: Rank and count the arguments that fall into each quadrant. This assumes: a) you can rank the arguments, which you can. Not all arguments are created equal. Hubble's universal function (we'll call it a function) was superior to Einstein's constant. Which assumption is backed by observable phenomenon? Which is assumption is backed by consistent theoretical frameworks? Which is an untested but attractive option? Arguments can be given equal rank to account for unknowns.

The next post will be why Michael Kjörling should use his mod hammer.

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    $\begingroup$ The analytic framework you present in your fourth paragraph (the one addressed to Mithrandir24601) would be easily sufficient to make this question not opinion based. Why not edit that into the question? That will automatically nominate it for re-opening, and I, for one, would vote to re-open. $\endgroup$
    – kingledion
    Jan 3, 2018 at 18:13

Why Michael Kjörling should use his mod hammer.

I have answered the objections to my question with a request for hard data. Where I have not provided valid scientific arguments I have proposed a valid quantitative format. I will accept a link that points me in the right direction (even to a academic physics paper). I have even taken the steps to ensure that I do not profit by way of vote, with the possibility of undue scrutiny by way of making this a community wiki.

I have provided you (general) with the one of four things you (singular) need for a better forum. This being valid arguments, those being hardware, technical personnel, moderators. Despite the hard evidence and the timeliness of this argument (two FTL drives in ~15 years, Who knew?) I was provided ignorance.

Here I'll give you (general) another one: Much of this sounds like the now classical hard sci fi versus soft sci fi argument. Hard sci fiers believe that science fiction must adhere to as many laws of science as possible. The ill destination of this argument is that any 80's sitcom would be considered more sci fi than the Europa Report, Gravity, Interstellar, etc. If I spell this out for you the answer to what is sci fi is not simply lack of hand wavium, but the unwillingness to speculate.

You want someone to stand by you if you use Modhammer. This is better than someone with 11 standing.

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    $\begingroup$ You don't get reputation for posts on meta. It seems like you don't have enough reputation to comment on other people's posts yet. That is a privilege you get at 50 rep. You should attempt to reply to other people's posts by using comments instead of posting separate answers since it makes it harder for other people to trace the flow of the conversation. $\endgroup$
    – sphennings
    Dec 28, 2017 at 1:49

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