Recently there was a significant discussion about whether a question on the main site should be on topic. I very strongly believe that it is not a good question for the site and should not be on topic here, but the community thought otherwise. That got me thinking about what defines our site's scope with respect to identification questions. I'm making this post to share my reasoning for why I think identification questions like that one should not be on topic here and see if I can convince the community to agree to make this policy.

To be clear, when I say "identification question", I'm talking about a type of question that simply asks "what is [thing]", where the "[thing]" might be an object or event seen in everyday life, or an object or optical feature in a photograph of everyday life (i.e. not a photo taken in a science experiment), or rarely, a video of something happening. There's often no indication of any prior research by the asker, and in particular, the asker doesn't share why they think the thing they're asking about has anything to do with physics or astronomy (as opposed to, say, chemistry or biology, or maybe they just thought "hey, scientists know all kinds of random things"). Also, the question doesn't ask to explain anything. E.g. if the thing being asked about is an event or optical feature in a photo, the asker doesn't ask why the thing happens, they just want a name. Or if they're asking about an object, they don't (seem to) care about what it could be used for.

I think these questions are bad for the site because

  • They're basically trivia questions which may or may not have anything to do with physics, so e.g. a random person is just as likely to know the answer as a random physicist or astronomer. That doesn't make the question bad, but I think it should mean that this site is not the place for it. I'd like to think that questions which are well-received here are those which are more useful to, and more answerable by the audience described in our help center (active researchers, academics and students of physics and astronomy) than to the average person.
  • Also, these questions don't prompt us to give an answer that shares any science knowledge. And if a question can be fully answered without sharing any science knowledge, it raises the question of what it's doing here, since neither the question nor its likely answers will be related to physics or astronomy. (Often one can post an answer that shares some physics/astronomy knowledge by going beyond what the question is asking for, but that's true of a wide variety of questions which I think we would all agree have no business here.)
  • A lot of these questions don't get much traction on the site, but the ones that do tend to be quite popular and often hit the HNQ, because visitors who aren't necessarily all that familiar with science can understand them. Tying into my previous point, that means a decent fraction of the questions that do the most work to represent our site are marginally or not at all related to physics or astronomy.

With all that in mind, what I'm proposing is that we make a policy that puts the burden on the asker of an identification question to show why their question belongs here, specifically. I'm proposing that identification questions, which ask "what is [thing]", must meet one of these criteria:

  • Explain why the question has something to do with physics or astronomy specifically (this would cover identification questions for devices used in physics experiments as well as astronomical objects)
  • Ask for some kind of physics-related explanation of the thing described, e.g. why it occurs (if it's a phenomenon) or possibly how it formed

Under this proposal, for example, all four of the following questions that Yly linked in the other meta post are fine because they ask for explanations:

There are a few questions where the answer would have to do with physics or astronomy but the asker doesn't know that or doesn't have any reason to believe that. Those would be rendered off-topic under this policy. I think that's reasonable because the asker can easily be guided to modify their question to make it clear that it does have to do with physics or astronomy.

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    $\begingroup$ -1 for proposing to place even more burden on question askers than there already is. Physics SE may be too big and a better way to restrict questions might be to split it up rather than discourage questions. $\endgroup$
    – uhoh
    Aug 24, 2020 at 5:19
  • $\begingroup$ @uhoh So you think the site policies are perfect and all the questions we get (which aren't already closed under existing rules) are good? $\endgroup$
    – David Z
    Aug 24, 2020 at 5:20
  • $\begingroup$ I don't respond to "So you think x?" where x is not a reasonable interpretation of what I've said. I've simply down voted and extended the courtesy of explaining it. $\endgroup$
    – uhoh
    Aug 24, 2020 at 5:22
  • $\begingroup$ I'm guessing you mean to imply that my interpretation was not reasonable, but I attest that it is. You disapprove of putting more burden on question askers than there already is; it seems like a clear logical consequence that you do not want any more restrictions on what questions can be asked here. Given that, it seems quite reasonable to think you believe that all the questions we get which are not disallowed by an existing restriction are good for the site, otherwise you would favor a restriction against them. I'm asking you to explain where that argument diverges from your actual opinion. $\endgroup$
    – David Z
    Aug 24, 2020 at 5:29
  • $\begingroup$ No I feel that the specific burden described in your post is not a good idea "...what I'm proposing is that we make a policy that puts the burden on the asker..." I'm not yet ready to post a full answer, but I wanted to down vote and I usually try to indicate in a comment what the down vote is for. Thus my comment begins with -1 and then continues with a short explanation of it. Let's wait and see how the answer posts evolve before going further. $\endgroup$
    – uhoh
    Aug 24, 2020 at 5:33
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    $\begingroup$ Ah, I see. I think I misunderstood the nature of your objection to the proposal based on your first comment. $\endgroup$
    – David Z
    Aug 24, 2020 at 5:43
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    $\begingroup$ Thanks for making this post. I think there was some conflation in the previous meta post between the site policy and whether or not users thought that specific question should be open / closed. As for this proposed policy, it seems like there is not much difference between on topic and off topic. i.e. it seems like I could go to any off topic identification question (according to this post) and just tack on at the end "Why does this happen?" and then now it is on topic since it is asking for an explanation. $\endgroup$ Aug 24, 2020 at 13:19
  • $\begingroup$ I also find that a lot of questions like these are missing a lot of detail, and thus lead to a lot of speculative answers. You will often see the comments flooded with further ideas / "experiments" for the user to do and report back on, and the answers have different explanations of "If this is the case, then it could be this. Or it could also be this. Or..." Would this policy need to be updated to handle cases like this, or would this just fall under the usual "Needs more detail / clarity"? $\endgroup$ Aug 24, 2020 at 13:21
  • $\begingroup$ @BioPhysicist (2 comments up) Yeah, that's true, although I think it'll often be clear whether a "why does this happen" was just tacked on at the end to try to meet a policy or it was incorporated because the person actually wants to know what's going on. Only in the latter case will it actually blend into the original question. And if someone tacks on "why does this happen" but works it into their question well enough that it sounds natural, then problem solved. (1 comment up) Good question and I'm not sure, but applying the usual "needs more details" probably covers many of those cases. $\endgroup$
    – David Z
    Aug 24, 2020 at 22:08
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    $\begingroup$ Also, the question doesn't ask to explain anything...doesn't ask why the thing happens, they just want a name. Or if they're asking about an object, they don't (seem to) care about what it could be used for. Is your point that if OP had asked “what’s causing these rays” instead of “what are these rays” it would that be on topic? $\endgroup$ Aug 25, 2020 at 11:07
  • $\begingroup$ @SuperfastJellyfish Yes, if the question had asked "what's causing these rays" I would consider it squarely on-topic. (I mean, I suppose there's still room for a trivial answer like "the sun", but I figure it's quite unlikely that people would actually answer that way, or that such an answer would be well-received.) $\endgroup$
    – David Z
    Aug 28, 2020 at 23:40
  • $\begingroup$ Ah okay. Then it seems like an issue easily fixed by editing, in case the author’s intent was to know the underlying physics to begin with. $\endgroup$ Aug 29, 2020 at 10:47

1 Answer 1


I sympathize with the intent of this post but I think it would be detrimental to implement the proposed criteria in practice.

  1. People observing a phenomenon and then asking what it is don't know what it is. How are they supposed to know whether e.g. some optical phenomenon they see is an optical illusion more explained by biology and neuroscience (think e.g. about still images that look like they're moving) or a "real" thing that is explained by physics?

    Instead of requiring an explanation of why they think it's "physics", I think we should just stringently use the needs details or clarity reason to close questions where not enough information is given to determine uniquely the phenomenon happening. If enough details are given, it's either close-able because the answer is not based in physics or uniquely answerable (yes, this is a rare case where I do think closing a question based on its potential answers is justified). The stringently is important there - we should not be willing to play a guessing game about physics that might be involved.

  2. The idea that they should ask for a physical explanation instead of just "what it is" is at first glance reasonable to me, but what's stopping us from simply assuming that someone who posts "What is this?" on a physics site is interested in a physics explanation of the "this" in question? Why do we need to close the question and force the asker to essentially always just replace "What is this?" by "What is the physical explanation for this?"? This strikes me as policing the formulation of the question more than policing its content. I think it's safe to assume that the overwhelming majority of people asking such questions on physics.SE will be interested in the physical explanation, and even if they're not - do we have to care?

    If the fear here is that if we don't do this then we get answers that just say "This is called X" without any explanation at all then I would like to believe that we'd just not upvote such answers (or even - gasp! - downvote them). If this belief isn't enough I'd prefer just making it a policy that such answers are considered non-answers (and hence deletable via low quality review) rather than requiring askers to jump through this specific hoop in how they're phrasing their question.

  • $\begingroup$ I was about to post the equivalent of point 2, but it is said here so perfectly that I'll just upvote instead $\endgroup$
    – WillO
    Aug 24, 2020 at 18:40
  • $\begingroup$ "If enough details are given, it's...close-able because the answer is not...uniquely answerable (yes, this is a rare case where I do think closing a question based on its potential answers is justified)." I feel like if unique answers are not possible then it is an issue with the question, not the answers. The close reason would be "the question does not allow for unique answers". So I still think we can say here that questions are not being closed based on their answers necessarily. This is opposed to, say, keeping a homework question open because of an amazing answer. $\endgroup$ Aug 24, 2020 at 20:46
  • $\begingroup$ @BioPhysicist You omitted the wrong parts of the sentence ;) I meant the parenthesis to apply to the other arm of the alternative there, i.e. the case where the answer is not based in physics. $\endgroup$
    – ACuriousMind Mod
    Aug 24, 2020 at 20:56
  • $\begingroup$ I knew I shouldn't have applied my virtual scissors liberally ;) $\endgroup$ Aug 24, 2020 at 21:05
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    $\begingroup$ Thanks for answering ACM. On point 1, I guess what I'm hoping is that, when people don't know what a thing is, they do a small amount of research elsewhere just to have some reason to think that something related to physics is involved. Otherwise, I worry that we'll get overly trivial identification questions like, say, Q: "What's the dark shape in this picture?" A: "It's the shadow of your head." That'd be a very clear, uniquely determined phenomenon, but I hope we can agree it's not a good question for this site. $\endgroup$
    – David Z
    Aug 24, 2020 at 22:17
  • $\begingroup$ On point 2... I guess, in that same example, if the question asked "Why do shadows form?" that would be fine (rather low-level, but on topic), but I just find it very unnatural to read "What's this dark shape?" and interpret it as "Why do shadows form?" I think it's very plausible that the asker in that scenario really just wants to know what that weird thing in their picture is and doesn't care why it's there, in the physical sense. Therefore, if they do want to know why it exists, I prefer to put the impetus on them to say so. $\endgroup$
    – David Z
    Aug 24, 2020 at 22:20
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    $\begingroup$ @DavidZ My argument in 2 is more that we don't have to care what the asker thought when asking the question. When the literal reading of the question is trivial like in your example, this certainly leads to answers which don't really answer what the asker intended to ask, but I think - not based on any hard data, I admit - that this is the minority case. I'd rather alienate a few askers by interpreting their question as a question about physics when it's not than alienate the larger fraction of askers by insisting they must phrase their question in a very specific way for us to answer it. $\endgroup$
    – ACuriousMind Mod
    Aug 24, 2020 at 22:25
  • $\begingroup$ @ACuriousMind Ah well I suppose we disagree on that. I prefer to see the written form of a question match the asker's intent as clearly as possible; I want to reduce the possibility that people interpret the question in a way it wasn't intended. I don't see that as having to alienate anyone. $\endgroup$
    – David Z
    Aug 29, 2020 at 22:23

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