I bring before the assembly Exhibit A, A cure for the 'Kessler Syndrome'?, tagged as of revision 1.

That question was closed as a duplicate of Dealing with space debris and Kessler Syndrome, tagged as of today.

The user who closed A cure for the 'Kessler Syndrome'? (gold tag badge holder) also referenced How to efficiently deorbit space junk, tagged and itself closed as a duplicate of Dealing with space debris and Kessler Syndrome.

Generally speaking, question X is a duplicate of question Y if, and only if, any valid answer to question Y is an equally valid answer to question X. Typically, question Y should also exist on the site before question X is posted, but exceptions sometimes exist.

Compare Does [hard-science] imply [science-based] imply [reality-check]? as well as Should our default position be that answers should be science-/logic-based, rather than magic-based? and A hard-science ultimatum, along with the hard science notice:

This question asks for hard science. All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See the tag description for more information.

Ignoring for a second that A cure for the 'Kessler Syndrome'? probably should be retagged with and possibly other tags to aid discovery via categorization by tags, my question is simply:

Given that hard-science questions place specific requirements on answers that neither science-based nor reality-check questions do, can a question tagged hard-science ever validly be a duplicate of a non-hard-science question?

  • $\begingroup$ I flagged the post as needing intervention because of the conflicting sci-fi, hard-science, and science-based tags, if you would like to take a look at it. $\endgroup$
    – John Locke
    Aug 26, 2018 at 15:11
  • $\begingroup$ I'm sorry, I'm sorry, geez. By the way, first I closed as a dupe, then I re-opened and stripped the science-based tag; thereby preventing it from being a dupe. Then a4Android dropped hard-science back to science-based, and then it got closed again. What a question! I feel like pretty much every step of that process was wrong. $\endgroup$
    – kingledion
    Aug 27, 2018 at 17:39
  • 1
    $\begingroup$ @kingledion Everyone makes mistakes. I've most likely made plenty. This meta question isn't so much about that one example (though it is what prompted me to ask the question), but rather about general policy: how should we treat these situations in general? $\endgroup$
    – user
    Aug 27, 2018 at 19:33

5 Answers 5


No, a hard-science question cannot validly be a duplicate of a non-hard-science question.

The existence of the tag on a question places specific requirements on answers. Answers that do not satisfy the criteria of that tag do not give original poster the information they seek, in much the same way that answers invoking magic are not valid answers to questions that do not allow for magic.

Since a non-hard-science question does not place such restrictions on answers as the OP has indicated that they want (by adding the hard-science tag to their question), answers that are valid to the non-hard-science question are not necessarily valid as answers to the hard-science question.

Therefore, the extra requirements placed on answers means that a hard-science question cannot be a duplicate of a non-hard-science question, even if the subject matter is similar.

However, the other question can, and might be, related and possibly useful to the OP, so it is perfectly appropriate to link to it in a comment and point out that it covers very similar ground.

If OP added the hard-science tag to their question without fully realizing what it means, including if the question appears to itself not meet the necessary bar for a question that seeks hard-science answers, then this can itself be pointed out in a comment and a suggestion be made for the OP to remove the hard-science tag. However, the ultimate decision as to whether to require answers to be hard-science or not should be up to the user asking the question; therefore, the tag should not be edited out without a clear indication from the user asking the question that such is their desire (and for clarity, it is probably best if they make such an edit themselves).

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    $\begingroup$ Hm. This seems to assume that all the answers to non-hard-science questions are not going to be acceptable to hard-science, but I often find myself writing hard-science answers to science-based or reality-check questions, simply because that’s what I enjoy doing. Your answer seems to imply that I’d just repost my hard-science answer from the non-hard-science question onto the new hard-science question. Are we okay with that? $\endgroup$
    – Dubukay
    Aug 26, 2018 at 17:56
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    $\begingroup$ @Dubukay It's certainly possible to answer a non-hard-science question with an answer meeting the criteria for "hard science". IMO, that's great if you do; I think that the site needs more of those. However, the issue of whether a question is a duplicate of another is an issue of which answers are acceptable as answers to each, not one of which answers have been posted. $\endgroup$
    – user
    Aug 26, 2018 at 18:26
  • $\begingroup$ Consider a fictious example that might be seen on Super User; one user asks how to accomplish something or another in LibreOffice Calc, and another user asks how to accomplish the same thing in Microsoft Excel. The two questions are not duplicates, because while the end goal might be similar or even the same, the premise that is being asked about (the software to use) is different. To me, hard-science vs not-necessarily-hard-science is similar. Hence the suggestion to comment with a link as related, possibly useful (but not duplicate), as already mentioned in my answer here. $\endgroup$
    – user
    Aug 26, 2018 at 18:26
  • $\begingroup$ Ah, I see. As long as we're fine with the same answer on two different questions I'm happy with it! Now that I look back on it, it was actually one of your comments on a different question that caused the concern about reposted answers. Obviously, that one had other problems and should've been tagged in the polite way that you did it, but over time I'd interpreted that as "please don't repost answers". Thanks for clarifying! $\endgroup$
    – Dubukay
    Aug 26, 2018 at 19:00
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    $\begingroup$ @Dubukay Note that the comment on the particular answer you're linking to specifically says "tailor the answer to the specific question, even if you are referencing the same source material". I strongly suspect that there are very few questions on the site where, between two questions, literally the only difference is the existence or non-existence of the hard-science tag. $\endgroup$
    – user
    Aug 26, 2018 at 19:08
  • $\begingroup$ This implies the opposite is true as well, right? That a non-hard science question can't be a duplicate of a hard-science question because additional answers not permitted on the hard-science question would be allowed on the non-hard science one? $\endgroup$
    – Troyen
    Sep 7, 2018 at 0:42
  • $\begingroup$ @Troyen Good point. Since the existence or non-existence of the hard science requirement changes the question, it makes sense that the same reasoning would apply both ways. That said, if the exact same question were to theoretically be posted twice, once with the requirement for hard science in answers and once without, it stands to reason that a valid answer to the hard science variant would be an acceptable answer to the one that doesn't require hard science. I might have to give this a bit of thought... $\endgroup$
    – user
    Sep 7, 2018 at 7:09

I agree with Michael's answer that a question has stricter requirements and thus shouldn't be marked as a duplicate (if it's really a hard-science question and not a tagging error). However, it's easy to see how this happens, so we should also clarify the distinction in the question itself.

Tags are easy to miss, especially on mobile or in the close-votes review queue. Further, not every reviewer will be immediately aware of the significance of this distinction; most tags are just for categorization, after all, so this one is unusual. Therefore, when a hard-science question is very similar to a non-hard-science question, it's best to edit the question to say something like "(link) is very similar, but this question asks for hard science".

This is a good approach when any credible duplicate has been suggested. If somebody suggests, or you discover on your own, a question that looks very similar to yours, anticipate and deflect the close votes. Link to the other question and say why yours is different.


I see the tags as a matter distinct from the question(s) asked in the title & body of the Query.

The cited questions share two tags in common: Kessler Syndrome & science-based; don't share other tags: near future, orbital mechanics & satellites.

Given the random nature of tag utilisation I don't see that as a viable sieve for determining whether one question is a duplicate of another. I think it might be dangerous to set this precedent as a determining factor. What if the question being considered for closure is subtantively superior? (Better grammar, more detail, wittier presentation.)

So YES: two queries that ask the same exact question in title & body twice with the same assumptions and the same pathway, but have different tags, they are duplicates of each other. (Which one should be considered be the duplicate is a question for a different debate.)

But the cited questions are not good examples. When I look at the actual questions, I see two basic issues:

  1. Reading only the titles, Charles Noon's basic query is "how to deal with space debris vis a vis the Kessler Syndrome" and case's basic query is "how to deal with space debris vis a vis the Kessler Syndrome". I concur: regardless of the tags involved, at the surface, the essential question is the same and the underlying background is the same.
  2. However, when we get into the body of each query, we see that the essential questions are radically different. Charles Noon asks "How can private industry deal with the problem of orbital debris over a longish but unspecified period of time" while case asks "How can government deal with an immediate & life threatening crisis of orbital debris menacing orbital operations".

Even without throwing the hard science tag into the mix, these are not duplicate questions: they share the same goal, but they are seeking answers along different pathways.

  • $\begingroup$ Quite right. The problem may be the same, but the questions are asking about different kinds of institutions tackling it, and how they would go about it. $\endgroup$
    – a4android
    Feb 1, 2019 at 1:27

Given the actual closure behaviour I've seen

"question X is a duplicate of question Y if, and only if, any valid answer to question Y is an equally valid answer to question X."

doesn't seem to be the practice. The practice appears to be more like "question X is a duplicate of question Y if the existing valid answers to question Y are equally valid answers to question X." In fact duplicate question closures have been defended on that basis more than once.

So in practice a question may in fact be considered a duplicate, (as in people may cast close votes on that basis) this may not be how the tag and the duplicate question status are intended to interact but it does happen, especially when the answers to a question are answers.



The second, hard-science question is not asking for anything new in terms of worldbuilding. At best, it's only asking for additional information to substantiate the previous question's answers.

It is theoretically true that a new, hard-science question can lead to a refutation of the previous question's answers in that forcing all the extra substantiation reveals an error of judgement on the part of the previous respondents. But this suggests that you're inviting a frame-challenge to the previous question. You're still not asking a new question.

This is, perhaps, an intrinsic flaw in Worldbuilding. Unlike most other stacks which deal in very objective information, we have the potential (and frequently do) to "relax the standards," which can lead to an erroneous answer that appears to be the best answer at the time. However, if we think this flaw is experienced so frequently that it makes sense to allow duplicate questions to be considered non-duplicate simply because a more rigorous review of the facts is demanded, then there is a systemic issue that we need to address — because having two questions considered unique only because one has been more thoroughly reviewed than the other is outside of SE's basic design and intent.

A potential solution

A potential solution is to permit non-duplication via the hard-science tag by expressly requiring the OP to explain why the original question's answers are unsatisfactory. In other words, require the current OP to explain the frame-challenge. If that challenge cannot be adequately explained (e.g., if the only excuse is, "I just want someone to provide better substantiation...") then the question would be closed as a duplicate — as it should be.

Because the ideal solution isn't available

Of course, the ideal question is to edit the previous question, impose the hard-science tag, and invite new answers. But this is impractical and is usually seen as treading on the original question's OP's "copyright," so to speak. Editing someone else's question in this kind of way is usually taboo.


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