I recently asked a question Backyard experiments to falsify the Flat Earth theory which has become much more popular than I originally anticipated, and has since been closed as a duplicate of What is the simplest way to prove the Earth is round?. Ordinarily I wouldn't mind too much that it was marked as a dupe since both questions are useful in their own right and the titles at least are clearly similar.

Today someone emailed me with a piece of info that should have been posted as an answer, but he said he didn't have the reputation to post since the question is protected. I resolved to post it on his behalf, but then I realized that it is not possible to add answers to duplicate questions. I suppose the idea is that the new answers should be added to the other question, but it doesn't seem to fit as well there, which makes me think that perhaps it shouldn't be a duplicate after all (although it is certainly a useful related reading).

As one commenter points out, there is a difference of wording - "show the Earth is round" vs. "show the Earth is not flat". My question is geared specifically to collecting practical experiments or observations that disprove the falsifiable physical component of the Flat Earth Theory espoused by the FES, not to showing the earth is round in the abstract. (There is also a social component, that is, showing that NASA is not involved in a coverup, but that's not as on-topic here.) The other question appears to have a more theoretical focus (probably "simplest" in the title was interpreted as "conceptually simplest"), and contains experiments like Eratosthenes that only work if you have already accepted the round-earth model to some degree (one of the answers on my question uses three-point Eratosthenes to circumvent this issue).

It doesn't appear that the question has quite finished its active period, and I would request that it be reopened. Would it be alright if I add a notice at the top pointing to the other question, but with less forceful wording than "this question is a duplicate"?

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    $\begingroup$ I would strongly suggest you to add to your question the reason for it not being the dupe of the linked one. That would lead it to the review of the community who would decide whether it is to be re-opened or not. $\endgroup$
    – user36790
    Commented Jan 30, 2016 at 7:56

1 Answer 1


To echo what user36790 said in a comment, when you think a question (B) which has been closed as a duplicate of another question (A) is not really a duplicate, you should edit it to make it clear that it's not a duplicate. After editing, the duplicate question (B) should

  • ask something that the original (A) does not, and
  • explain clearly and explicitly why the thing that B is asking is not covered by A (see also below), and
  • link to the original question A

A side effect of editing is that the question gets placed into a queue to be reviewed for reopening.

The link and reference to the original question doesn't need to be at the top, the way the automatic duplicate notice is. In fact, I think it's better if it's not at the top. The first paragraph or two of a question should probably give the main point of what you want to ask, and while showing your prior research is important, it's not the main question. Here's one example of how I would do it. (Maybe not the best example, but I think it's good enough to serve as a guideline.)

When question B is asking something not covered by question A, that means that any potential valid answer to B would not answer question A. Or in other words, a post that does answer question B, if it were posted to question A, would clearly be going above and beyond what is required to actually address question A. The fact that one could interpret B to include something that A does not is not itself enough to prevent B from being considered a duplicate. And the fact that the existing answers to A don't address B is definitely not enough. (Duplicate status is determined based on the question itself, not the answers.)

In your particular case, editing the question to ask "How can I show the Earth is not flat without assuming that it's round?" might be a good way to start (of course that would be just the title; what really matters is how you edit the body of the question). Though it's hard to say for sure without knowing what you have in mind.

  • $\begingroup$ I will do this. I find that users often seem to choose their duplicate votes based on the titles, since it is common to see duplicate protests for questions which have similar titles but a different body, so choosing the title well is important (although I didn't know about the other question when I first posted). As for answers not determining the tenor of the question, this is particularly difficult for questions that get a lot of answers, since they choose their own reading and I can at best guide the conversation. But I can certainly revise the question to reflect the answers better. $\endgroup$ Commented Jan 30, 2016 at 9:58
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    $\begingroup$ To be fair, @MarioCarneiro, I initiated the vote to close your question because it's basically an exact duplicate (any answer posted in A would be acceptable for B and vice versa) and not because of the similarity of the title. You might phrase the question differently, but it's still asking the same exact thing. $\endgroup$
    – Kyle Kanos
    Commented Jan 30, 2016 at 22:04
  • $\begingroup$ @KyleKanos I'm not sure how else to put this, and of course you are free to vote as you like, but I disagree. The problem may be the same, but the focus and intended audience are different, and the existing answers reflect this difference (and I did my best to have the question also reflect the difference). It is possible to ask a math question in fifth grade and repeat the same words in a college class and receive a completely different answer because the audience and context are different. $\endgroup$ Commented Jan 30, 2016 at 22:23
  • $\begingroup$ @KyleKanos The answer that was emailed to me was basically one person's specific experiment (they went up on a mountain and took some measurements). This answer would not be appropriate on the other question because it doesn't address the "how", but it is appropriate for my version, which calls for experiments and observations (although it could be improved by also explaining how to generalize the experiment to other mountains etc.). $\endgroup$ Commented Jan 30, 2016 at 22:29
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    $\begingroup$ @Mario: one could easily port the experiment into a 'how plus proof' answer that would be acceptable for the original question. $\endgroup$
    – Kyle Kanos
    Commented Jan 31, 2016 at 15:53

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