I note What is the ultimate purpose of physics.stackexchange?, but it seems to me that the accepted answer doesn't answer the question. I have no special wish to get excessively philosophical, but I think being clear what we're trying to achieve will help clarify vexed issues like homework.

Leaving aside what SE are trying to achieve (profit presumably), it seems to me that good reasons for the effort we put into this site include:

  1. Fun
  2. Encouraging interest in physics
  3. Education
  4. Research

Experience suggests that research will only ever be a tiny part of site activity because there are too few research physicists interested in participating. Let's also leave aside Fun because it's a given - few people will do things that aren't fun unless they're paid or forced to. If you're with me so far that means we basically have two aims, to encourage interest and to educate. Arguably encouraging interest is also educating, but at a popular science level, in which case our sole purpose in life is education.

Since this is supposed to be a question rather than just a diatribe, I guess my question is whether you agree with my analysis and if not, why not?

  • $\begingroup$ FWIW Physics.SE doesn't provide direct income to SE at all, nor will it in the forseeable future. So I don't really agree with dmckee's answer there. I do know the purpose(s), and will answer when I get the time. $\endgroup$ Commented Nov 11, 2013 at 12:48
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    $\begingroup$ I am a bit confused as to What is the ultimate purpose of this post?, with no offense, nor sarcasm intended. $\endgroup$ Commented Nov 11, 2013 at 14:35
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    $\begingroup$ @DIMension10: if the purpose of the site is to educate that changes our approach to homework questions, because homework is an important and effective part of education. It was while thinking about how we should best address the current flood of homework that I realised I didn't know what the point of this site was (apart from giving us retired scientists something to do :-). $\endgroup$ Commented Nov 11, 2013 at 16:21
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    $\begingroup$ @JohnRennie: "Homework" (by which I mean low-level homework, of course) is NOT the same as "Education". $\endgroup$ Commented Nov 11, 2013 at 16:35
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    $\begingroup$ @DIMension10: If someone copies and pastes a problem from their homework then just answering their question helps neither the student nor this site - I'm sure we both agree on this. However if a student can't solve a homework problem because they don't understand a concept, haven't spotted the appropriate mathematical method, etc, etc, then explaining how to do the homework is education. $\endgroup$ Commented Nov 11, 2013 at 17:21
  • $\begingroup$ @JohnRennie: Ok, I'll accept that, but you seem to be saying that all of "Education" would be to be about homework, right? That isn't necessarily true, or rather, it's false most of the time. You can have a non-hw conceptual question. $\endgroup$ Commented Nov 12, 2013 at 3:07
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    $\begingroup$ @Manishearth I stand by the earlier answer as to the purpose of Stack Exchange. Certainly Physics.SE is not a notable source of revenue for them and may not be for the foreseeable future, but we help to build the brand. The purpose of each person in participating here is quite another thing. Or many other things. $\endgroup$ Commented Nov 12, 2013 at 8:07
  • $\begingroup$ @dmckee In the future, maybe, but a very distant future. SE is (used to be) VC funded, so the actual monetization is sketched up as something to be done later. So there isn't much point thinking about that right now IMO. $\endgroup$ Commented Nov 12, 2013 at 8:19

6 Answers 6


Well, John, it's actually pretty simple from my perspective. The purpose of this site is to promote the creation and trading of value for value for those interested in thinking about and doing physics.

This, in my opinion, is the only valid reason for this site's existence. I've learned a good bit here from other's answers as well as through composing my own answers; a process which forces me to think very clearly about the particular topic and, in so doing, sharpens my own thinking and deepens my understanding.

I assume that I'm not special in any way and thus that others desire to create and trade value here in the same way.

I certainly feel no obligation to participate here for some "larger cause". My participation is for a purely selfish reason: I profit from it (in the larger, proper sense of the word).

I hope that is the reason others volunteer here to answer and moderate; that they too find value and profit for themselves in doing so.

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    $\begingroup$ Given that you have answered quite a number of questions, I don't agree that your presence here is "Selfish". $\endgroup$ Commented Nov 13, 2013 at 13:24
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    $\begingroup$ @DIMension10, it is probably the case that we disagree on the meaning of "selfish" which I take to mean rational self-interest. $\endgroup$ Commented Nov 13, 2013 at 22:09
  • $\begingroup$ The system is rigged on purpose so the value that it is created is a public value. An answer of yours might be valuable to the OP, but also to the 100 people that have the same question and arrive via Google later. :-) $\endgroup$
    – Sklivvz
    Commented Nov 17, 2013 at 0:29

The primary purpose is to "Make The Internet a Better Place™". What this means is that the Q&As should be of the form that are useful to others. People searching for a conceptual explanation or the resolution of an apparent paradox should find this site and be helped here.

This has a long history. If you've ever googled for help with something and come across a forum, you might have been frustrated by the signal-to-noise ratio on that forum. I recall coming across tons of tangential discussion, and sometimes pages and pages of discourse which reaches no resolution. Besides that, many of these are cluttered with duplicates and one-time problems that are really too specific for anyone else to benefit. Forums are useful to the people asking questions and the handful of community members participating in the discussion. But the wider audience from the Internet has a hard time with forums.

Stack Exchange tries to do away with that, by keeping posts focused and only allowing posts that will help many people. This was the essence behind the "Too Localized" close reason that many of you may remember, — the point was that while the answers may help the OP, there's a very little chance of it helping anyone else.

This is also one of the main reasons why we close homework. Besides the no-effort-please-do-my-work-for-me, homework questions don't help any other visitors. While the answers may be conceptual, it is pretty hard for someone with the conceptual question to find the homework problem via Google or otherwise, as the question focuses on the problem, not the concept 1. As for people who want help with the same homework problem, well, that's pretty rare.

So the main purpose is to also help people other than the OP, people who will come to the Q&A after searching related terms.

But that's just the primary purpose. As you mentioned, fun is another factor2, as is encouraging interest and conceptual education. The "fun" bit extends itself; I personally don't participate just because it's "fun". I write answers because my own understanding is strengthened by doing so3, not just to help the OP and the other readers.

I'm not intending to say that we aren't here to help each other. We are. The community feeling is a great thing, and helping each other learn physics is a good goal. But one should try to have a look a the larger picture, helping a couple of people on site is dwarfed by the countless other non-members we help.

Research is a different beast. Our non mainstream policy, in its attempts to be as objective as possible to avoid unnecessary arguments, stops us from developing new physics4. I guess this is OK, because frankly speaking, the people here have better channels to develop new physics; by discussing with colleagues and collaborators. The ones who choose to try to develop the theory here are usually the type that are proposing some non mainstream ideas. Besides all this, the limitation of discussion on the main site is a damper here, though that is easily remedied with chat.

Note that this is in no way saying that research level questions are discouraged, just that using the site as a platform to develop new theories collaboratively is discouraged.

1. Which is why we encourage making HW question conceptual; people will actually find the question then

2. Don't let this blog post tell you otherwise ;-)

3. The act of codifying nebulous thoughts on a topic into clear English is something that seems to immediately highlight one's own conceptual misunderstandings and inadequacies.

4. Neither does MathOverflow, they have a policy against open questions and the like, and they still maintain a good level of research-level questions. MathOverflow disallows well known open problems, but they don't seem to have any research being done on site, even if the posts may inspire research.

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    $\begingroup$ From where do you get these ideas? Is this your own proposals? $\endgroup$ Commented Nov 11, 2013 at 22:39
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    $\begingroup$ @user1708 It comes direct from Jeff and Joel. It is why they started Stack Overflow and why they extended the model to become Stack Exchange. You can find it in one of the first few podcasts and mentioned from time to time since then. $\endgroup$ Commented Nov 11, 2013 at 23:25
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    $\begingroup$ You're wrong about Maths Overflow. I've seen many comments (no don't ask me for a proof, as I can't find it) stating that certain questions have inspired actual research papers. Their "open problem" policy is against well-known open problems, I guess that's because those are just probjems posted by random people wanting to test MathsOverflow-people. Why wouldn't they have? Even Maths.SE (which is Not an exclusively research-level site) has actually had questions that inspired research papers. Search for "History of Math.SE" on Mathematics Meta. $\endgroup$ Commented Nov 12, 2013 at 3:16
  • $\begingroup$ @DIMension10 Hm, you're right about that. Still, I don't see the community doing new research on their own, though they may discuss new problems and may inspire papers. $\endgroup$ Commented Nov 12, 2013 at 5:13
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    $\begingroup$ @DIMension10: You might be thinking of this Mathoverflow meta post. $\endgroup$
    – Qmechanic Mod
    Commented Nov 12, 2013 at 12:53
  • $\begingroup$ @Qmechanic: Yup, you're right, that's the one. $\endgroup$ Commented Nov 12, 2013 at 13:07
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    $\begingroup$ I came to this forum as the result of googling a topic I was interestedin. I take it that this is an example of what Manishearth is asserting. Many of the posts on this forum show up on page one of a google search. $\endgroup$ Commented Nov 22, 2013 at 2:59

In addition to "Encouraging interest in physics" and "Education", an important part of most SE sites is also to get real feedback on both questions and answers. This is what allows some of us to learn provide clearer answers and ask more focused questions.


It isn't possible for there to be a single ultimate purpose, since the existence of Physics Stack Exchange depends upon a diverse range of purposes:

  • those within the community contributing to the site,
  • the unpaid moderators
  • the company financing the project
  • the motive of the founders
  • other people and group motives I'm not aware of

Maybe a better question would be to ask: What's the purpose behind you being here?

For me, the fundamental reason is given in Alfred Centauri's answer. I liked the idea of contributing to the site, putting it down on my CV as one of my interests, and the interviewer could take a look at some of my answers and hire me. Now that I'm more aware of my incompetence, I use the site more passively to learn from others, in the hope I might actually get round to asking good questions more regularly.


Sticky content that allows SE to get lots of hits. That allows the investors and owners to make money.

  • $\begingroup$ Nope. Physics doesn't generate revenue via hits (hits don't just equate to money). There's probably a very small bit of revenue generated by the site; that's if people get introduced to other network sites through this. The only revenue generating sites are Stack Overflow, Super User, Server Fault (through ads), and careers.SO through the paid employer plan. $\endgroup$ Commented Nov 12, 2013 at 5:17
  • $\begingroup$ @Manishearth: Is there anyone on Physics.SE who doesn't know about Stack Overflow?. $\endgroup$ Commented Nov 12, 2013 at 6:52
  • $\begingroup$ Not my downvote, but this doesn't answer the question, unfortunately. The OP mentions "other than what SE are trying to achieve (profit prosumably)", so this could go as a comment instead. $\endgroup$ Commented Nov 12, 2013 at 6:53
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    $\begingroup$ @DIMension10: I suspect most physicists have to code as part of their research, so most physicists are also programmers. There reverse is not true - maybe the world would be a better place if it was :-) $\endgroup$ Commented Nov 12, 2013 at 8:12
  • $\begingroup$ @DIMension10 Maybe because they already were aware of it? Even if they weren't, very few would participate (and physicists aren't the target audience of careers.SE so the main revenue source goes out the window). The number of people who come to Physics.SE and learn about SO afterwards is low. The number of people who will actually use SO after that is even lower -- those who program as part of their jobs already know of SO. Such a small percentage of visitors can hardly make them much money. $\endgroup$ Commented Nov 12, 2013 at 8:24
  • $\begingroup$ @Manishearth: Not necessarily. I didn;t' know about SO, before. (Well, I had posted a (now deleted) question on SO, about 3 years back, before I knew about PhysSE, but I didn't even know that it was called "Stack Overflow", and I hadn't even come back to the question page (I couldn't remember the url, and didn't even bookmark it, nor was it still in my browser history), so I don't even consider that as "knowing") $\endgroup$ Commented Nov 12, 2013 at 15:07
  • $\begingroup$ @DIMension10 Yes, but do you use it now? How much? I'm talking about the people who become Stack Overflow regulars. Or those who at least visit it frequently. They are few, because SO is more famous than Physics.SE amongst those interested in both topics. Because SO is one of the most well known sites on the Internet. $\endgroup$ Commented Nov 12, 2013 at 17:05
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    $\begingroup$ while it is correct that we monetize the really big sites this way, it is not the case for physics. Believe it or not it doesn't really generate a large amount of traffic, so at the moment there are no plans to monetize this particular site. We can't. $\endgroup$
    – Sklivvz
    Commented Nov 17, 2013 at 0:26
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    $\begingroup$ Dim10 There simply is not other purpose here than to make money. $\endgroup$
    – user12811
    Commented Nov 21, 2013 at 5:00
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    $\begingroup$ This is obviously the correct answer, so naturally it is downvoted. $\endgroup$
    – Fattie
    Commented Oct 29, 2015 at 13:54
  • $\begingroup$ There have been some comments along the lines "this particular site is not a profit center". Obviously, in any business (not to mention dotcom startups) many particular items are not profit centers. This is just a dotcom startup like any other. How can anyone be confused by this? Everything done in the business is just part of the overall straightforward, well-trodden, plan: build the site up and sell it, as a or to a public company. How can anyone find this confusing? $\endgroup$
    – Fattie
    Commented Oct 29, 2015 at 14:01

The purpose of physics stack exchange is simply to allow students from across the world to ask their homework questions, and for students and experts to gain personal fulfillment from answering other's people's homework questions, improving assignment grades around the world.

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    $\begingroup$ Is this sarcastic? $\endgroup$ Commented Nov 14, 2013 at 5:18
  • $\begingroup$ As if it is broe $\endgroup$
    – Kenshin
    Commented Nov 14, 2013 at 5:19

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