I've read the meta questions on duplicates. This question may well be a duplicate, but there are some unlearned lessons in those answers.

Two questions prompted me to raise this issue in meta.

  1. If the universe is expanding, what is it expanding into?
    Apparently this question is used so often as a link target for other questions that a rather large bounty was given to provide better answers. Why?

  2. Special Relativity, 2nd Postulate — Why?
    This question was closed as a duplicate of Special Relativity Second Postulate. Why?

The first question is a poorly formed question. It asks four distinct questions at once, and the answers are subpar as a result. A google search on "what is the universe expanding into" will yield a number of well-written answers. Our site should be on that list! Each of the four questions raised in that one question should be a question of its own. In fact, some of those questions have been asked individually, and those individually asked questions have received better answers. But yet they are marked as duplicates of the cited poorly written question.

With regard to the second question, the only thing the two questions have in common are that they both ask about Einstein's second postulate of special relativity. The older question asks whether that postulate truly does mean that nothing can go faster than the speed of light. The newer one asks what motivated Einstein to choose that axiom. These are not duplicates. The older question did not ask the latter question, and none of the answers to that older question broach the subject raised in the newer question.

Before marking a question as a duplicate of another one should ask

  • Is this new question really a duplicate of the target question? Do the answers to the target question answer the question posed in the new question?
    If the answer is no, this question is not a duplicate. Don't mark it as such.

  • Is the target question well posed? Are the answers to the target question well written?
    If the answer is no, and particularly if the new question is much better posed than the target, don't mark the new question as a duplicate. Close the old question as trash instead of giving a massive bounty.

  • $\begingroup$ I'd also like to point out that there are some occasions where questions are marked as duplicates of questions that are already marked as duplicated of other questions. That just seems silly to me $\endgroup$
    – Jim
    Sep 10, 2014 at 13:05
  • $\begingroup$ Also, re(1): I think this is a good point. We seem to be in the habit of rewarding questions on a first-com-first-serve basis. Which means a question need not be well-posed, just be first-posed. Instead, if a duplicate question is asked, we should leave the better posed question open and mark the other as a duplicate, regardless of which came first. Then all the good answers can be merged into the open question. This is like natural selection for questions. The best survive meaning our frequent questions only get better with time. $\endgroup$
    – Jim
    Sep 10, 2014 at 13:12
  • $\begingroup$ @Jim: I have to confess that I've occasionally flagged a question as a duplicate of a question that is itself flagged as a duplicate. I've done this when I think the answers to the question closed as a duplicate are better than the answers to the original question. I don't think we should be too worried about eliminating every last duplicate as different questions sometimes ask similar things but with different slants, and the answers are slightly different as a result. As long as the duplicate links exist the OP can look at all the related questions just by following the links. $\endgroup$ Sep 10, 2014 at 15:55
  • $\begingroup$ @Jim I agree but I doubt it would always be clear which question is better. To person A formulating something one way is clearer than formulating it another way while person B might have the opposite experience. $\endgroup$
    – Wouter
    Sep 11, 2014 at 10:19
  • 1
    $\begingroup$ @Wouter I suppose that's why 5 people would have to vote on closing a question as a duplicate $\endgroup$
    – Jim
    Sep 11, 2014 at 12:24

1 Answer 1


Re (1): Danu suggested a while back that we should have a set of canonical questions that could be used as targets for duplicates. I'd guess Chris' bounty is an attempt to get such a canonical answer. Maybe the effort would be better spent on writing a new and clearer question/answer. If so Chris could ask the mods to refund the bounty and then write a new question - I guess that's up to Chris. Whatever the case, if a really good answer to the current question emerges that has to be a useful step.

Re (2): when questions are a little ill posed I often try to provide a broader answer than the one actually requested. Of course I'll answer the question, but I'll usually also try to put it in context and expand around it. So although you're correct that the two questions are different I think they basically have the same answer(s) and can usefully be regarded as duplicates. We seem to differ about what the key features of that answer is, but that's physics I guess :-)

  • $\begingroup$ I too have occasionally reinterpreted an ill-posed question and answer the question the user should have asked. That said, the question "What motivated Einstein to posit that the speed of light is the same to all observers" was well-posed in my opinion. Ignorant, yes, but that's a different issue. I still see zero duplication between the two questions, even with a liberal reinterpretation. Moreover, I don't see your answer in the linked question as answering the question posed in the supposed duplicate question. $\endgroup$ Sep 10, 2014 at 16:23
  • $\begingroup$ I don't really care about the rep. And I think we'll get at least one good answer out of it. I placed the bounty because a user asked one of those questions, and in searching for an answer that I knew had to be here already I found (1) every question pointed back to that one, (2) every question was equally poorly written (and really, how could someone ask that question well without knowing the answer), and (3) there wasn't a good answer out there. Spending rep is easier than writing a question, both lead to a good answer, and tbh Danu's proposal had slipped my mind when I did this. $\endgroup$
    – user10851
    Sep 13, 2014 at 0:25

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