I've just voted to close this post, which I will slightly paraphrase because I'm sure it will soon be deleted:

I would like to know in simple words why time slows down and lengths change when I am in my private rocket traveling near the speed of light.

Although I think that almost everyone will agree this should be closed, it's not so clear which of the close reasons to choose. (In fact, I ended up choosing one pretty much arbitrarily and no longer remember what it was.)

Yes, this question is a duplicate many times over, but I can't choose that reason without pointing to a specific prior question, which I'd rather not do, partly because I don't want to spend time hunting up that question and more importantly because I don't want to send a message that posters who can't be bothered doing their own searches can post questions like this and expect others to do their searching for them.

It's not really unclear what's being asked. "Too broad" and "primarily opinion based" don't seem to fit. That leaves:

This question does not appear to be about physics within the scope defined in the help center.

Well, that's pretty good, but unfortunately I can't choose it without choosing a sub-reason. And none of those sub-reasons seems to fit. This is not a homework-like question, it's not about engineering, and it doesn't (to my knowledge) belong on another site on the Stack Exchange network.

Is it non-mainstream physics? Well, sort of, in the sense that it seems to confuse a "change in (proper?) length" with a change in the assignment of coordinates, but I think there is a difference between being non-mainstream and being a little confused. Besides, there are many other questions at about this level which are even more mainstream than this one, but still equally in need of closing.

That leaves me with the option of formulating a custom close reason, which requires a little extra effort on my part --- all the more so because that custom close reason automatically becomes publicly visible as a comment, so that although all I want to do is cast a close vote and move on, I feel like I need to spend an extra minute or so making sure my comment is fit for public consumption.

For this and other such questions, I would be much happier if it were possible to close with the reason "This question does not appear to be about physics as defined in the help center", where it is stated upfront that this site is for active researchers, academics and students of physics and astronomy.

Let me close by saying that we get a lot of questions at this level, some of which show more thought than this one does (e.g. the questions that arise periodically where someone has actually given some thought to what it would be like to ride on a light wave, has discovered an apparent paradox, and wants to know how to resolve it). I think it's important to discourage such posts without discouraging the spirit of inquiry that lies behind them. Telling people that they are engaged in "non-mainstream physics" is, I think, likely to be perceived as disparaging --- which is doubly unfortunate because thought-experiments like this are mainstream physics. (Yes, these thought-experiments have already been done and other people know the results, but naively repeating someone else's experiment---thought or otherwise---is still mainstream physics.) So I don't want to choose that option, but I do want to dispose of these posts quickly and effectively, and "not within the scope of the site" seems like a far better option than "non-mainstream".


Question 1: Can we please be given the option of closing as "Not within the scope...as defined in the help center", without having to choose or formulate a sub-reason?

Question 2: Does someone have a better suggestion?

Edited to add: Some have responded that "Too Broad" fits this question perfectly. Whether or not that is the case, it does not dispose of the general issue. What about questions of the form "I imagined myself riding on a lightbeam, and I don't see how I can square the obvious consequences with the fact that the speed of light is supposed to be invariant"? This is (I think) far too specfic to be "Too Broad", far too honest an effort to think things through from first principles to be "Non-Mainstream", and a bad fit for all the others too.

Edited to add further: I've just noticed that moderators already have access to the exact close reason I'm asking for, for example here. Apparently someone thought it was a good idea for moderators to have this option, and apparently at least one moderator thinks it's a good idea to use it.

  • 2
    $\begingroup$ This one is a textbook "too broad" for me. Questions that ask "I would like someone to clarify this detail" we can handle; questions that ask "I would like someone to write a tutorial on this topic for me" stretch our model past breaking point. This one is in the second class. (Plus, also, zero prior research either off- or on-site, and not a lot of respect for potential answerers shining through, either.) $\endgroup$ Jul 31, 2016 at 22:30
  • $\begingroup$ @EmilioPisanty: I'm not sure it really is too broad. I think an equally broad question about a more esoteric topic --- one where quite a few readers of the site would learn something from the answer --- would be quite well received. (I am pretty sure there are good examples on things like how classical EM emerges as a limit of QED.) The difference is that such a question would be interesting to students and/or active researchers in physics, while this one is not. $\endgroup$
    – WillO
    Jul 31, 2016 at 22:33
  • $\begingroup$ Sure, the scope is obviously context-dependent. And this one is still on the Too Broad bin for me. $\endgroup$ Jul 31, 2016 at 22:36
  • 1
    $\begingroup$ I didn't include this in my answer because it's beside the point, but surely you see the irony in simultaneously complaining about lazy askers and complaining that coming up with a one-line custom close reason is too much effort on your part? ;) $\endgroup$
    – ACuriousMind Mod
    Jul 31, 2016 at 22:59
  • $\begingroup$ @ACuriousMind: On the contrary---the poster is requesting help; the responders are doing good deeds (either on behalf of the poster or on behalf of the site). I think it is a good thing to expect more effort from those who are asking for help, and to require less effort from those who are helping others. So I reject your false irony! :) $\endgroup$
    – WillO
    Jul 31, 2016 at 23:01
  • $\begingroup$ @EmilioPisanty: I've added a paragraph at the end of the original post that I think addresses your "Too Broad" comments. $\endgroup$
    – WillO
    Jul 31, 2016 at 23:36
  • $\begingroup$ I would suggest that this is nowhere close to non-mainstream physics. Confusing a change in proper length with a change in coordinates is a conceptual misunderstanding of exactly the type that this site is meant to help clear up (if the OP had done a better job of writing the question). It's worth keeping in mind that not everything that's wrong is non-mainstream. That close reason is generally meant for the real crackpot stuff. $\endgroup$
    – David Z
    Aug 1, 2016 at 16:26
  • $\begingroup$ Oh, and regarding your latest edit: that's what shows up when we choose "Other (add a comment explaining what is wrong)". I think this should be doable for regular members too. $\endgroup$
    – David Z
    Aug 2, 2016 at 16:52
  • $\begingroup$ @DavidZ : Ah, right. Thanks for pointing this out. $\endgroup$
    – WillO
    Aug 2, 2016 at 18:26

3 Answers 3


I would have closed it as a duplicate of What is time dilation really?

That question seems as close to an exact duplicate as one could ask, the only caveat being the request in the original question for in simple words. But then there is a limit to how simple an explanation can be made before it becomes meaningless.

You say:

I can't choose that reason without pointing to a specific prior question, which I'd rather not do, partly because I don't want to spend time hunting up that question and more importantly because I don't want to send a message that posters who can't be bothered doing their own searches can post questions like this and expect others to do their searching for them.

but taking the time and effort to do this is an important part of managing the site. The SE policy is that duplicates are valuable signposts that point visitors to the (hopefully) definitive answer. That is, the duplicates increase the likelyhood of a search finding a relevant question. So if you want to help make the site a better place then I'm afraid the search for duplicates is an essential part of the process.


For the abstract questions you pose:

No, if you close something as being out of scope, you have to explain why it is out of scope. The pre-existing reasons cover the most common reasons, for the others, you'll have to write a comment explaining yourself. The close reason is there to give the asker feedback what exactly they did wrong, and just telling them it's "out of scope" doesn't really tell them what went wrong.

Aside from providing valuable feedback to the asker (that is sadly all too often ignored, or taken as a personal insult, but that's another issue), a specific close reason is also valuable for other voters - especially reviewers - to agree or disagree with. But if you just choose "out of scope", then that doesn't give your peers something to argue with: Either they already agree it's out of scope or they don't, but "out of scope" is so vague as to make it impossible to constructively disagree.

Finally, I don't have a better suggestion because we don't need a better suggestion. If you think a post is non-mainstream then you should close it as non-mainstream. Votes are judgements of questions and answers, not of users. The feedback they provide is valuable only if given honestly - I see no value in not voting as you want to vote because of the psychological consequences you fear it may have on the user.

For the specific question you're talking about:

In my opinion, the least controversial way to close this is as too broad. It's a question that basically asks "Explain special relativity to me", without any research effort shown and without any specific question. It's not clear to me how one could determine a "correct" answer specifically to this question, i.e. how one would decide when it is actually answered.

It also had two close votes as homework-like, now hidden by the majority close reason too broad. I don't really understand those, it's not a question that falls under our homework policy by any stretch of the imagination.

I don't understand the suggestion to close it as "non-mainstream", either - it's not non-mainstream, it's a question about basic special relativity, no personal theory in sight, just confusion (and little effort on part of the asker).

Because there are so many introductory resources to special relativity both on and off this site, I think closing because of insufficient effort (as a custom close reason) would also have been defensible if you think we should be closing questions for that. See meta discussions here, here and at further links in those.

The duplicate close reason is different. You vote to close as duplicate because you have already found the question it's a duplicate of. Duplicate questions are neither off-topic nor unclear nor too broad nor any other of these reasons. Closing a question as duplicate just says that we already have a sufficiently similar question here. If you're thinking the question should be closed anyway, go ahead and close it for another reason, but never forcefully try to make another reason fit just because you can't be bothered to search for the duplicate. (I'm not accusing you specifically of this, but I think it's worth explicitly stating in general.) I personally think that there's no value in closing a question that should be closed for another reason as duplicate, unless one then proceeds to close the duplicate for that reason.

  • $\begingroup$ Just one brief correction: I never had any inclination to close this as non-mainstream. I was responding to the fact that I know that similar questions have been closed for this reason, in my view quite inappropriately. $\endgroup$
    – WillO
    Jul 31, 2016 at 22:59
  • $\begingroup$ @WillO: Okay, phrased that part without reference to you $\endgroup$
    – ACuriousMind Mod
    Jul 31, 2016 at 23:01

I started to type this as a comment, and then it became an answer.

I apologize if I'm mistaken, but I've heard that the homework close policy may be reformulated soon to be more along the lines of not enough effort. It seems like this is really what you want, because as you said in your question, it is more about being a little confused.

Honestly, though, I think it should be closed as one of the following two.

  1. Duplicate - It definitely is a duplicate, as you said. I think this is the best thing to close it as, because then the guy gets an answer (or a partial answer) to his question, along with the one already there. I can sympathize with your point about it making posters lazier, but I don't know if that's really the case. And, honestly, question quality is a whole other problem that other meta discussions have gone over.
  2. Too Broad - As Emilio Pisanty said, this is another great close reason. While opinions on this might vary from person to person, the question is basically "Explain special relativity to me." We're not Wikipedia. Sure, we can provide a summary, and I personally think it being a duplicate is a better close reason because of that, but this is still a valid close reason.

This is definitely not a "not mainstream physics" question. Special relativity is mainstream, and being confused about special relativity is also mainstream. Besides, even if most people understood special relativity, being a little confused is the whole point of a question and I think that we need to respect that. Perhaps this guy should've done more research. (The user certainly needed to search for duplicates.) But it is a valid question on the physics.SE forum in terms of topic.

Finally, ACuriousMind says exactly my point of view on the new close reason you suggest. It is so vague that it doesn't help the asker or reviewers.

That's just my two cents; I hope this helps.


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