I've found multiple times the closing of questions about the topic of general relativity/solutions of the einstein field equations. Examples are here and here. These judgement was: "not mainstream".

High reputated physicists on the list seem to agree with my opinion (see for example John Rennie's comment here 2 hours ago, or Flint22's comment here)). Their opinions were:

"I don't think this is off-topic. If you draw the Penrose diagram for e.g. a Reissner-Nordstrom black hole there are null geodesics that allow light from other universes to be seen."

"While I agree that to answer this question would be pure speculation, I absolutely disagree that the Kerr Metric is non-mainstream. It is a well studied solution to the Einstein equations which is to be found in any graduate lecture course on Black Hole Mechanics."

My current suggestion were to change this de-facto policy, and repair its damages on the site by

  • the removal of the lock from the questions,
  • and to do a scan in the currently held/deleted questions, and do the same if there is the same case. Partially I could help in this, although I can't see the already deleted questions.
  • $\begingroup$ Note that the close reason picked is not the one picked by all users, it takes a majority (with some precedence). I say this because both those questions have multiple problems, and seeming speculative is a minor one compared to the vagueness and lack of prior research by the OP. So it seems possible that different people picked different reasons to address the multiple issues, and non-mainstream came up on top due to the tie-breaker algorithm. $\endgroup$ – Manishearth Jun 17 '14 at 13:15

Despite my comment I didn't vote to reopen the question you mention. This is because after an initial burst of enthusiasm I took a closer look at the question and decided it didn't make sense. I suspect there is a language difficulty and result is that as it stands the question can't be answered.

I did consider editing the question to make it clearer, but it was at that point I realised I could be sure what the OP was actually asking. So I decided to leave it closed on the grounds it's unclear.

So although I think the close reason non-mainstream was wrong, I still think the question should be closed. I obviously don't know the thought processes of those who voted to close, but given how confusing the question is I'm reluctant to censure them.

I do agree the question Where is the way on a rotating black hole to another Universe? has probably been closed unfairly, but again it's a poorly written question and I feel no great urge to attempt an answer.

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    $\begingroup$ Independent from the question, there is also another problem as well. And this is about that the topological extensions of the GR (i.e. hypotheses/models about multiple Minkowski-universes) are considered mainstream, or not. If you won't a physics SE where this topic is handled as if it were some like "pseudoscience", maybe you should use your reputation to change this seemingly bad community behavior. $\endgroup$ – peterh - Reinstate Monica Jun 18 '14 at 10:13
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    $\begingroup$ @PeterHorvath: If you can reference a paper published in a refereed journal then it's probably mainstream. If you can't then it probably isn't. On balance I agree with the community - actually I suspect I'm a bit more inclined to VTC than most - but that doesn't mean I think the community is always right. $\endgroup$ – John Rennie Jun 18 '14 at 10:18
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    $\begingroup$ I can reference, if I dig a little bit about this. I am sure (I've heard about this from an university professor specialized on GR). But I am not physicist, for me were a little bit harder to dig out old and well-referenced arxiv articles, but I will do if there is no alternative. But why is it needed? You know that it is mainstream. Every physicist know this. If it weren't so, I should dig on arxiv to convince you. Why don't you speak with them? $\endgroup$ – peterh - Reinstate Monica Jun 18 '14 at 10:27
  • $\begingroup$ @PeterHorvath: looking back at the rotating black hole question I see I closed it as a duplicate. $\endgroup$ – John Rennie Jun 18 '14 at 17:38

I want to point out one aspect of the question closure procedure which is relevant here but is not apparent to <3k users (and even then takes a while to realize). When voting to close a question, one gets to choose between the multiple options, but after you have five close votes the question gets closed regardless of what the mix of options is. (That is, three non-mainstream votes and two unclear votes will cause a question to be closed.) Further, only the reason with the most votes gets reported, and the other ones are not visible, either publicly or to 3k+ or 10k+ users.* It is therefore possible that those questions have, say, two non-mainstream votes, two unclear votes, and one too-broad vote.

The bottom line is that question closure mostly reflects that the community thinks a question is closable, but the reason stated is slightly more of an indicative thing and does not necessarily reflect a consensus among the close-voters.

* At some point, I think after this answer was written, it became possible to see which close-voting users actually used the reported reason, as shown here. Unless such a tagline is shown, then it is not appropriate to attribute closure reasons to any individual close voter in the absence of further evidence.


Only one of the two linked questions in the OP was closed as "not mainstream".

The "light in another universe" question was voted "not mainsteam" by Alfred Centauri, Brandon Enright and Qmechanic and two others voted to close for other reasons.

The "rotating black hole" question had at least one customized reason that mentioned not being mainstream, but I don't seen any evidence that anyone (else) voted "not mainstream". I voted to close because I didn't think it was clear what was being asked.


Personally, I think both questions are definite cases of "unclear what you're asking". I don't know what either of them really wants to know, to the extent that it's questionable whether they're really asking about the Kerr metric at all. So I think it's right that they're closed.

However, I really wish that both community members and (on other questions) moderators would avoid selecting "off topic" as the close reason in such cases.

To me, closing something as "off topic" sends a message that says "we don't want any questions on this topic, even if they are otherwise excellent questions and have no other issues." If you close a question as off topic then you're saying that the topic is the primary issue, and this implicitly restricts what can be discussed on the site in future. So please, please, please, if a question has multiple issues, close it as something other than "off topic" unless it really is the case that no question on a similar subject could possibly ever be tolerated.

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    $\begingroup$ Generally speaking, a problem with this is that the custom close reasons we're given are all grouped under "off topic," even if they have nothing to do with the topic of the question. So we don't have a choice. Arguably this is something that the SE developers could fix (and I bet there's a feature request for it on Meta Stack Exchange), but as things stand, just avoid reading any meaning into the words "off topic." $\endgroup$ – David Z Jun 29 '14 at 20:12
  • $\begingroup$ @DavidZ I agree that there are cases where it's unavoidable with the current system, and this is unfortunate. I'm just users in general to prefer "unclear", "too broad" or "opinion-based" rather than "off topic" in cases more than one are applicable; in these particular cases "unclear what you're asking" would have done nicely. I know that "off topic" doesn't always mean "off topic", but we can't expect every visitor to know this, and it's wise to do things that give the right impression when we can. $\endgroup$ – Nathaniel Jul 6 '14 at 6:49

Regarding Where is the way on a rotating black hole to another Universe?

I disagree that its non mainstream, but I find it too unclear and closeable.

Besides, even if the Kerr Metric is mainstream (which it is, afaict), Flint's comment does classify the question as not:

> While I agree that to answer this question would be pure speculation, I absolutely disagree that the Kerr Metric is non-mainstream.

Speculative questions fall afoul of our mainstream physics policy since the answers won't be accepted physics. (Which is what Brandon meant when he said "partially non maisntream")

Regarding https://physics.stackexchange.com/questions/119562/light-in-another-universe

Again, it is unclear, but not to the extent that it is closeable. It has a speculative tone about it, but it seems mainstream to me.

The general issue

I haven't seen many questions mis-closed as non mainstream. The community usually manages to pick these up well, however if the question is unclear it's really the OP's fault. The best way to get these opened is to get the OP to edit them. I left a comment on the Penrose Diagram one to that effect.

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    $\begingroup$ 1) the questions are clear for me, even as not being native english speaker. 2) they were closed as "non-mainstream", and not as "unclear". 3) There wasn't any real explanation, neither a way to ask somehow one. 4) My current hyphothesis that these questions were closed somehow because a blind misunderstood. Your answer tries to balance between different opinions, and does nothing. Maybe it is useful in some political sense, but... IMHO, the goal of a moderator shouldn't be the least possible conflict, the goal of a moderator should be to help to make the system the best possible. $\endgroup$ – peterh - Reinstate Monica Jun 17 '14 at 17:19
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    $\begingroup$ "Light in another universe" doesn't even parse into anything remotely well defined or answerable. It is the very definition of "unclear." $\endgroup$ – user10851 Jun 17 '14 at 19:47
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    $\begingroup$ @ChrisWhite I parsed it as "Can we tweak fundamental constants to come up with a universe in which light does not exist". But yeah, that's one way of looking at it. I get what you mean. $\endgroup$ – Manishearth Jun 18 '14 at 0:49
  • $\begingroup$ @PeterHorvath Chris' comment makes sense here. While there is one way of interpreting it that seems mainstream, "light in another universe" isn't really a physical concept unless you qualify it with some further explanation of what you mean. By "unclear" I'm including the fact that it has many interpretations, which is evident from how the community is interpreting it in many ways. I don't understand what you mean by your 3rd point. $\endgroup$ – Manishearth Jun 18 '14 at 1:11
  • $\begingroup$ I'm not balancing, that's not the goal of the moderator. The first part gives a clear verdict. I'm unsure about the second part, which is why I've left it that way. Moderators usually don't take unilateral decisions to reverse stuff unless it's clearly against policy. I'm unsure of what to do for the "light in another universe" case and would prefer to see a discussion between community members leading to a verdict rather than unilaterally reopening it (or whatever). Besides, it was recently posted, and it has a chance of being fixed (which is why I left a comment there). $\endgroup$ – Manishearth Jun 18 '14 at 1:14
  • $\begingroup$ Regarding the fact that they were closed as "non mainstream" and not "unclear", refer to my comment on the question above. It's possible that one or two people voted as nonmainstream, and the rest voted for other reasons, the system just chose the non mainstream one. Besides, when a post is unclear it is possible to interpret it as non mainstream, especially when it talks of seemingly non-physically established concepts. $\endgroup$ – Manishearth Jun 18 '14 at 1:17
  • $\begingroup$ Re that last point, see my answer. $\endgroup$ – Emilio Pisanty Jun 19 '14 at 5:13

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