I've been looking through the new Physics Overflow beta¹ and looking back at some of the discussion about the closure of the Theoretical Physics SE. From a purely personal perspective I would prefer research level questions to be asked here because though it's very unlikely I could answer any it's interesting to see other peoples answers. However I appreciate that active physicists don't want to wade through acres of basic questions from non-physicists.

At the same time there are lots of non-physicists interested in physics as shown by the proliferation of science programmes on TV, and I believe strongly that there should be a site for anyone interested in physics to get clear and authoritative answers to questions at this level. I think Stack Exchange is the best place for such a site because it's designed to reduce the junk and advocacy that swamps other less regulated fora.

The approach taken by the Theoretical Physics SE, and now the Physics Overflow, is to split off the most advanced questions, but history shows you end up with a site with very low traffic. I wonder if it would be better to split off the low level questions.

In my perfect world that would leave the Physics SE at a higher level and hopefully manage to both attract back the higher level users and keep the traffic high enough to keep the site vibrant. The Popular Physics SE would provide interested bystanders with their answers, and maybe it could take a more lenient attitude to homework.

My perfect world doesn't exist, of course, and there are obvious problems such as how to decide which site to post questions on. My suggestion would be to use Physics SE for undergraduate and above level questions and Popular Physics for everything below this. I note the blurb for the Physics SE still says Physics Stack Exchange is a question and answer site for active researchers, academics and students (my emphasis). Assuming we treat the sites as siblings, migration between them (mostly from Physics to Popular Physics I'd guess) would be less of a big deal than attempting migration to unrelated sites like the Math SE.

I think that's about it - I will be very interested to hear other views on the idea.

¹ Note that the Physics Overflow is not part of the Stack Exchange network

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    $\begingroup$ +1 because this topic does need to be discussed. I personally really don't like the idea of splitting Physics.SE, though. It's an interesting idea, just not something I like :P Also, I'm not entirely sure if an SE site where the answerers won't ever ask anything is good. It's best if there's a single community around it :) $\endgroup$ – Manishearth Apr 8 '14 at 10:36
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    $\begingroup$ Related area51.stackexchange.com/proposals/58070/popular-science $\endgroup$ – Dilaton Apr 8 '14 at 12:29
  • $\begingroup$ You want a split between harder and easier questions. You point out that there are now two physics sites and your conclusion is to make another one? ^^ $\endgroup$ – Nikolaj-K Apr 8 '14 at 14:02
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    $\begingroup$ @NiftyKitty95: there were two Physics SE sites, but the advanced one was closed due to low activity. The proposed new Physics Overflow site is unconnected to the SE and is still in beta. So as things stand there is one Physics site. I'm suggesting we have two sites, but both on the SE. $\endgroup$ – John Rennie Apr 8 '14 at 14:16
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    $\begingroup$ @JohnRennie: Okay, yeah. I also find a site removed from the SE collections rather unpractical regarding notifications etc. $\endgroup$ – Nikolaj-K Apr 8 '14 at 14:19
  • $\begingroup$ So are you proposing keeping this site a mid-to-high level questions site and making a low-level question site? As opposed to the high-level and mid-to-low level that TP and Phys.SE were before and failed? $\endgroup$ – tpg2114 Apr 8 '14 at 17:50
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    $\begingroup$ @tpg2114: yes, exactly. $\endgroup$ – John Rennie Apr 8 '14 at 17:52
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    $\begingroup$ Okay -- and is it based on the technical content of the answers or the perceived difficulty of the question? As an example: physics.stackexchange.com/q/107191 which I answered in an arguably "low level" way could also have been answered in an incredibly technical level with gas dynamics, equations, experimental data... So would that question be migrated away? Would it depend on the answers which site is a better fit? Just trying to wrap my head around your idea $\endgroup$ – tpg2114 Apr 8 '14 at 17:54
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    $\begingroup$ I think it would depend on what sort of answer the questioner is looking for. If the answer consists of working through a set of equations then it's obviously high level. If the answer is entirely hand waving and analogy it's probably low level. The example you give would fit either, because you didn't give any equations but you did introduce concepts that are quite advanced (I didn't realise the supersonic flow accelerates as the area increases!). $\endgroup$ – John Rennie Apr 8 '14 at 18:06
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    $\begingroup$ So Devil's Advocate here -- how would the migration process work? Do we migrate only once answers begin to appear and it looks like they are low level? Using that question as an example again, I wrote my answer in like 3 minutes just to get the ball rolling, hoping somebody else would come along and do a better job. But then I ended up rep-capping and it got a ridiculous number of votes for what I consider to be a pretty poor answer. Would we have to wait and see what OP selects as the right answer to determine his/her intent and the final location of the question? $\endgroup$ – tpg2114 Apr 8 '14 at 18:17
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    $\begingroup$ I would let the community decide. We already use the vote to close system to suggest migration to sites like the MathSE, so do the same with the new site. Five VTCs and the question gets migrated along with any answers it had accumulated. For the specific question you mentioned I would probably have voted to migrate. $\endgroup$ – John Rennie Apr 8 '14 at 18:20
  • $\begingroup$ OKay, but it would be a "wait and see what comes in" rather than judging it based solely on the content of the question? And I'm only talking about edge cases -- questions that say "I have no background and am a high school student" are pretty clear, as are questions that use math notation I'm pretty sure doesn't even really exist. Also -- I appreciate your willingness to discuss the idea with me, I just want to make sure I understand what you're proposing and how it might work. $\endgroup$ – tpg2114 Apr 8 '14 at 18:23
  • $\begingroup$ @JohnRennie So it seems that Popular Physics SE didn't happen after all. I would have loved the idea. $\endgroup$ – Tycho's Nose Aug 28 '17 at 14:35
  • $\begingroup$ @Tycho'sNose: the chat room has become an informal version of the Popular Physics SE. There are usually a few of us hanging around in there and we're willing to answer the sort of questions that aren't suitable for the main site. $\endgroup$ – John Rennie Aug 28 '17 at 14:51
  • $\begingroup$ @Thank you, sir. I'll keep that in mind. $\endgroup$ – Tycho's Nose Aug 28 '17 at 15:04

Phys.SE is currently 3.5 years old and has the second-most traffic of all the science sites at SE (with Math.SE being number one), so at least in that sense it is quite successful[1]. Also Phys.SE receives a lot of Google hits and is quite visible on the Internet. So Phys.SE has in many ways found a robust formula, which is spelled out on the help pages:

Physics Stack Exchange is for active researchers, academics and students of physics and astronomy. We welcome questions of all levels, but please stick to the following topics [...]

We should not let events outside Phys.SE (which might be just a flash in the pan, like the previous TP.SE) dictate what is and what is not the purpose of Phys.SE. We welcomed all levels before, and we should continue to welcome all levels. By splitting up Phys.SE in many parts, we may very well destroy the formula, which has worked in the past.

Besides the theoretical reasons to keep all levels at Phys.SE, there might also be practical reasons: It may be practically impossible to establish an unanimous definition of what constitutes high, medium, and low level, and so forth.

Concerning high-level questions: You can still ask high-level questions on Phys.SE! We are open 24/7 and it is business as usual. One thing that we learned from the TP.SE failure (with its unfortunate slow traffic) is that if you ask a high-level question, there might only be a few experts in the world that can answer on the spot. Many more experts would be able to answer after "doing the calculation themselves", however they often haven't the time. But if they are curious enough they might do it anyway! So long story short: One should expect that high-level quality answers take time. Phys.SE offers a visible platform on the Internet and has many active (and also some more dormant) experts in all corners of physics. If you have a high-level question in physics, then Phys.SE is definitely one of the best places to ask it, in terms of receiving a useful answer.

Concerning low-level questions: We should continue to enforce that questions should preferably be conceptional. E.g. low-level homework questions should follow certain rules. Moreover, some basic/minimal research of the topic (like googling before asking) is generally expected, cf. this meta post. As for a discussion of a Popular Physics site, that seems to belong to Area51 rather than on Phys.SE.


[1] In fact one interpretation of the large traffic volume is that we are drowning in success: The front page currently changes every 6 hours (or so), which means that it is easier to overlook a post nowadays, relatively speaking.

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    $\begingroup$ -1 for calling Theoretical Physics SE a failure, it was a very nice high-level community, but the SE network is not meant to support such smaller rather specialized communities with slower traffic. The SE model favors mass visibility of content that is understandable and useful for a large number of people, as explained for example here, which makes topics with a smaller audience (such as for example research-level theoretical physics) incompatible with the goals of SE. BTW the beta state of PO just means that we still have things to do ... $\endgroup$ – Dilaton Apr 8 '14 at 22:51
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    $\begingroup$ ... by now means does it mean that it will eventually go away, get closed, or something. Just to clarify. $\endgroup$ – Dilaton Apr 8 '14 at 22:52
  • $\begingroup$ Whoops, I meant research-level theoretical physics is not compatible with the SE goals as the only topic of a site (such as TP.SE), not as a topic among other topics on a site which works of course ... $\endgroup$ – Dilaton Apr 8 '14 at 23:14
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    $\begingroup$ +1 This. I don't see why splitting a site is going to make any good. You're only going to be splitting communities and everything is going to be less efficient. I also like the other points you made. $\endgroup$ – Alenanno Apr 10 '14 at 9:33
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    $\begingroup$ I don't agree that there is no problem. The current problem is the low traffic of high-level/quality questions, which (many believe that) is caused by incorrect policies of the site. For example, One may claim that a site with many low-level, HW questions will not attract experts attentions. $\endgroup$ – Mostafa Apr 17 '14 at 16:48
  • $\begingroup$ So you mean the most traffic among all the science sites on SE--because math is not science! xD $\endgroup$ – Dvij D.C. Feb 22 '19 at 16:42
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    $\begingroup$ Well, in recent years, Phys.SE has the third-most traffic of all the science sites at SE (with Math.SE & Stat.SE being number one and two). $\endgroup$ – Qmechanic Feb 22 '19 at 19:56

I think that a popular physics site would be a bad idea within the format of voting and assuming that a highly voted questions will be correct.

a) Most of the people voting will be non physicists

b) few knowledgable physicists will be consistently checking every day

This will result in arbitrary votes and even wrong ones, not exactly cranks but half informed people pushing successfully their half informed opinions.

Truth in science is not arrived at by consensus of the hoi polloi.

The only way this might work would be if the people answering were high reputation people from physics.SE and the popularphysics.SE registered users would not be allowed to answer, only to comment maybe. Anyway this is outside the format of SE.

Edit: Let me add some thoughts here

Over the two+ years I have been following physics.SE the level of physics has fallen. I was first alerted to the existence of the site by Lubos and in the beginning there were a number of good answers to questions that stretched my little grey cells( well women are supposed to have white ones :) , so treat it as a saying ). A lot of people with a better knowledge of physics than I have left for various reasons the site, or are completely inactive. Very few questions appear in my area of expertise ( experimental particle physics) and the reason I persist is in order to exercise my teaching muscles over the repetitive naive questions of young students ( and keep those grey cells active in my retirement). Better than scrabble after all.

So I hope the physicsoverflow will be successful even if not jumping with activity, where I can follow something challenging and new.I am essentially saying that the format of voting, when the numbers become large and experts become a small percentage of the populace essentialy leads to a popularphysics ambiance. You cannot ask that everybody participating has a physics degree after all,because the SE objectives include students in highschool. physics overflow explicity puts the limit at graduate level upward questions so I hope it will succeed in keeping a high level.

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    $\begingroup$ can you please comment on your negative vote? I am really interested in your answer. $\endgroup$ – anna v Apr 10 '14 at 9:56
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    $\begingroup$ Personally, I don't care for popular questions at all (i.e. questions such as "how to explain that the earth is round?"), and this is why I have downvoted you. My ideal forum would be one where questions of undergraduate level and above are allowed, and this included purely mathematics questions that are relevant for physicist. (Especially the latter part is the reason why I hope the new Physics Overflow will become a success, because we are (most of the time) not allowed to ask these questions.) $\endgroup$ – Hunter Apr 10 '14 at 11:52
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    $\begingroup$ @Hunter and why do you think I disagree with your statement? I am just saying that a popular physics forum by itself is not viable in the format of Stackexchange and still support good physics. It will probably end up with UFO questions etc answered by aficionados of the genre. $\endgroup$ – anna v Apr 10 '14 at 12:12
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    $\begingroup$ I don't know whether you agree or disagree with my statement. However, I do know that I disagree with your statement (because I would like to get rid of the popular physics questions one way or another), and that is why I downvoted you. $\endgroup$ – Hunter Apr 10 '14 at 12:19
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    $\begingroup$ @OK, thanks, I understand where you are coming from. Maybe you will understand where I am coming from if you read the edit I am preparing. $\endgroup$ – anna v Apr 10 '14 at 12:27
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    $\begingroup$ I do understand your point, and after reading your edit I think our opinions might be quite similar. Also, I agree with "You cannot ask that everybody participating has a physics degree" (I myself do not have all the degrees and will start a PhD next year), which is why I personally would allow for undergraduate questions. But these popular science questions do annoy me, because they seem to generate a lot of attention (for unknown reasons) and I don't think this should be encouraged. $\endgroup$ – Hunter Apr 10 '14 at 12:45
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    $\begingroup$ (Also, I want to say that I can live with the popular questions, as long as the don't appear too frequent. I have more difficulties with the maths questions not being allowed, but this might be a different discussion.) $\endgroup$ – Hunter Apr 10 '14 at 12:47
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    $\begingroup$ @Dilaton Yeah, I have already asked a maths question and got a really nice answer, which is why I'm really happy with your initiative :). At the moment I don't have any questions though (well I do, but I've already asked this on math SE, but maybe I will cross-post it to Physics Overflow). $\endgroup$ – Hunter Apr 10 '14 at 20:46
  • $\begingroup$ @Hunter (second comment) note that we already have a place where you can ask mathematical questions, namely Mathematics. That's why we don't allow them on this site, because they have a better home elsewhere. $\endgroup$ – David Z Apr 11 '14 at 18:19
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    $\begingroup$ +1 for using the term "hoi polloi", that was fun. -1 for mentioning something as an inherent difference between men and women (true or not, they're both equally capable so let's not distinguish if it isn't relevant). But +1 for being generally true and agreeable. $\endgroup$ – Jim Apr 11 '14 at 19:53
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    $\begingroup$ @DavidZ I'm very aware of that site, but clearly mathematicians and physicist use a different language. For instance, a physicist asking a question about complex analysis on Maths SE will most likely result in an answer that will be incomprehensible for the physicist. But this has already been discussed. $\endgroup$ – Hunter Apr 11 '14 at 19:54
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    $\begingroup$ @Hunter okay, I've posted this related meta question. $\endgroup$ – David Z Apr 12 '14 at 20:39

24 hours on, and whatever the rights and wrongs of my suggestion it's clear that the site members as a whole don't feel strongly about the issue. Only ten votes have been cast on my question, and at the time of writing the most active answer only has six votes (three up and three down).

Starting a new SE site, or even reviving Dilaton's Area 51 proposal would be a great deal of work, and there clearly isn't any enthusiasm for this. That makes the project a non-starter.

I'd guess most of the site members just don't think there's a problem, so agonising on how to address it is pointless. Unless anyone else wants to shout now, I'll leave it a day or so then accept this as the answer.

  • $\begingroup$ There's not much point in just downvoting. If you don't want me to give up on this idea then say so. I complain about lack of enthusiasm and you can't even be bothered to say why you downvoted. QED!!!! $\endgroup$ – John Rennie Apr 9 '14 at 16:36
  • $\begingroup$ Ok yes sorry John. To me it seems the above negative answer belittles or at least completely neglects the fact that there already are people on Area51, who try to do what you proposed in the question with a somewhat broader scope. The Popular Science proposal is meant among other things for people to get simplified but correct answers (Matt Strassler style) to questions about (natural) sciences, withoug getting bogged down in too much technical jargon or equations. $\endgroup$ – Dilaton Apr 9 '14 at 16:54
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    $\begingroup$ @Dilaton: I don't mean to belittle your Area 51 suggestion. Actually I think it's a good idea. It's just that I don't see lots of people queueing up to support it. $\endgroup$ – John Rennie Apr 9 '14 at 17:07

This is one aspect that is fundamentally different on the science sites on SE compared to many other sites on the network. Non-programmers generally don't ask questions on Stack Overflow, but a significant part of the questions on Physics, Chemistry and Biology are from a laymen perspective. This is inherent in the topics I suspect, programming just doesn't lend itself to this kind of questions from non-programmers, while many people are curious about basic facts and concepts from physics, chemistry or biology.

I rather dislike the idea of splitting a site according to some more or less arbitrary question level or difficulty. The practical problems of defining the boundary between sites alone are a huge headache. I think Math Overflow showed that this concept can work well at the very top of the question level, but I am not convinced that it would work as well if you add such separations at lower levels.

I'd also be very, very careful in examining what we want to achieve when we discuss splitting off a part of the site at the lower level. This can easily end up as a site that just gets all the trash from the higher-level site dumped onto it. A site that is created simply to get rid of certain questions we don't want here is doomed to fail.

I'm not saying that a Popular Physics site couldn't work, I actually do think that something like a Popular Science site could work if approached correctly. But such a site must have a positive definition of what it should be, it can't start as a category of questions we don't want here. I'd also include all natural sciences, I think just physics would be too narrow.

The definition of popular science is not really about difficulty level or effort in the question. The big difference is that such questions are asked by people without substantial education in the subject. This not only changes the question, but it also changes how answers should be written. This is also one aspect that would benefit the most from a separate site, as there it would be clear that answers need to be understandable by the general public.

But homework questions are not popular science questions. They are an entirely different category and I think making a popular science site into a homework dumping ground would doom it from the beginning.

I'm a moderator on Skeptics, and Skeptics is to some extent already a popular science site. We're more restrictive, but we often explain current scientific research in laymen terms. So I certainly think that such an effort is worthwhile, I don't regard popular science questions as somehow lower quality, but they need a different approach than questions from a scientist or student.

I'd be very careful about migration, it is often misused as a softer alternative to closing, and that would result in this site just dumping all the crap on the popular physics site. If such a site is created, it would have to prove that it works without any migration path.

  • $\begingroup$ I loved this answer; it said exactly what I was thinking and read exactly like what I lacked the motivation to write. That is, right up until the last bit where it became hard to tell if you are pro or con cutting off the lower-level questions from this site. But for the most part, this was the only time I wished I could up-vote twice $\endgroup$ – Jim Apr 11 '14 at 19:57

I somehow don't like the idea of a split; I think the site is stronger together, and sometimes basic, naive questions actually have advanced answers, that might not be intelligible to the original poster, but are interesting for other people.

Could it be made easier to filter/hide popular physics questions? A clear button near the top of the page, "Hide basic questions" that removes all traces of basic physics for the user would suffice? To me, that is much more palatable than a physics overflow style breakaway.

Practically, it would be much simpler than your suggestion, though it would require every new question to be assigned basic or advanced status.

  • $\begingroup$ There is a popular-science tag, but it has fallen into disuse. I suspect that the more enthusiastic members of the site are all experienced physicists and less interested in popular science questions. The result was that the most active taggers ignored the questions that most needed the tag. See this search of the Physics meta for some of the associated discussions. $\endgroup$ – John Rennie Apr 8 '14 at 14:12
  • $\begingroup$ I think (but I'm not sure) that the main reason we don't use level tags (popular-science and research-level) is that it's simply too much work to keep up with them. If we attempt to categorize all questions in this way, new posters won't know that they should do so unless the technology forces it on them, and it's impractical to expect editors to catch every question with one tag or the other. $\endgroup$ – David Z Apr 9 '14 at 19:41
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    $\begingroup$ @david "unless the technology forces it on them" - would that be tricky to implement? $\endgroup$ – innisfree Apr 11 '14 at 9:40
  • $\begingroup$ @innisfree I'm not sure if it would be technically tricky, but what would be tricky is convincing the SE developers that it is a necessary or useful feature. $\endgroup$ – David Z Apr 11 '14 at 16:23

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