I'm more than 99% sure the wrong answer was accepted here: Rotation angle of a giant lily when a child crawls on its rim

(Of course, I'm subject to significant bias saying this, since I submitted a different answer.)

Edit: In the particular question I linked, the wrong answer's been changed, so I'm happy about that.

Ordinarily, if a wrong answer is accepted and a better answer exists, the better answer will still get a lot of up votes so that a user browsing the site can see the community's opinion. In this case, I think the scenario is different.

The incorrect answer was originally a correct answer to a simplified version of the problem. That correct answer got a lot of upvotes. Then the author generalized the answer incorrectly, resulting in an incorrect answer with a lot of upvotes.

So now, the incorrect answer has a lot of upvotes, and is marked accepted, even though I believe strongly that the community as a whole would not support it as the correct answer. Is there some course of action I can take to call the community's general attention to this situation?

Edit: I'm not completely sure whether this is an "honest" meta question, or whether I'm actually just fishing for people to support my answer. If this question gets a couple of downvotes, I'll take the hint and delete it. On the other hand, behind my emotional desire to be validated, I really do want the correct answer to be accepted in general and think there is some actual validity to this meta question.

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    $\begingroup$ You could just make a note of this in your answer to that question and move on. Over time anybody who really cares about the solution will surely see your warning and take that into consideration. There are bound to be many differences of opinion on such a site and its unlikely there is any systemic solution that would satisfy everyone. $\endgroup$ – Deepak Vaid Jan 13 '11 at 19:26
  • $\begingroup$ @space Very reasonable note, thanks. $\endgroup$ – Mark Eichenlaub Jan 13 '11 at 19:49

If it is edited into an (not necessarily) incorrect answer, but a conflicting with the earlier, or critically stiuation changing details are added after the answer beeing accepted, a moderator should revert it to the earlier version and the user should be told to post instead a new answer, since these changes constitute the definition of a NEW answer.

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    $\begingroup$ Is that an official position or your opinion? $\endgroup$ – Mark Eichenlaub Jan 21 '11 at 7:41
  • $\begingroup$ @Mark I know its my opinion, but it could and should be both, I ahve not checked FAQ $\endgroup$ – TROLLHUNTER Jan 21 '11 at 7:51
  • $\begingroup$ Okay. I'm unsure whether I agree or not, but just wanted to be clear about what you were saying because I don't have experience with StackExchange outside of the physics site. $\endgroup$ – Mark Eichenlaub Jan 21 '11 at 7:53

I would say:

  1. Comment -- with good argument, this should make answerer correct the answer
  2. Downvote to enforce reading the comment
  3. If answerer is not responding (for instance lost interest in SE), edit the answer

About the mutating question problem, this should be resolved by adding new question, not new answers. In SE philosophy, a question/accepted answer pair should later serve as instant-information page -- one Googles the question, reads the answer and has his problem solved; a clutter of answers to different stages of question evolution effectively masks any useful information. So, if you see this happening, ask the OP to make a new question.


Good question. In my opinion, this shows the fundamental weakness of the StackExchange based approach. Everything is static and any change (either in question or answer) is not reflected at all and leads to inconsistencies. So assuming SE people won't change the engine underlying voting, one can only suggest that things not be changed unless absolutely necessary. It's fine to make the question/answer more precise but to change them completely is just bad.

Actually, this is an issue just for questions because changing them makes all the given answers invalid. But if someone wants to change the answer I suggest they just post a new one. This also suggest a solution to your problem: revert the accepted answer to the old, correct one (albeit simplified) and let ftiaronsem post a new answer with his new solution.


The usual method in teaching is that the teacher asks the students questions. The students provide answers (guesses), and the teacher grades them. This works because the teacher is assumed to have more knowledge about the subject than the students.

Stack Exchange tries to turn this on its head. The "student" asks a question. The "teacher" provides an answer. Then the other students (i.e. readers) grade them. This kind of teaching method is suitable for subjects far simpler than physics. Physics is about learning how to make calculations. Stack Exchange is mostly about the transmission of data.

It shouldn't be too surprising that the result is kind of rough sometimes. You're letting the inmates run the asylum. I think it was Winston Churchill who said that something to the effect that democracy was a horrible system of government but seemed to work better than the alternatives.

But really, why should it be such a horrible thing that a wrong answer, or even a complete crank answer, gets voted up and accepted by the questioner? It's not like someone is going to be executed as a result of the decisions made here. A student who relies on the internet for answers to their homework shouldn't be shocked when (a) they occasionally get wrong answers and (b) they usually don't learn anything.

If you want to learn physics, reading answers is not going to help you. The people who are learning physics here are the ones answering the more difficult (for them!) questions, not the people reading other people's answers.

I think things will work better if we all understand that the primary purpose of this site, just like the evening news, is entertainment, not truth. That said, I've had some good use out of this system and will likely continue to use it. I don't expect it to converge to the "truth" and won't lose any sleep over its failure to do so.

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    $\begingroup$ @Carl: You can't have a good use of this system if wrong answers are consistently upvoted. By the way, I agree that reading answers doesn't help to learn more physics but this system helps the asker and helps the answerer. $\endgroup$ – Robert Smith Jan 21 '11 at 5:56
  • $\begingroup$ My questions with Dr.Motl about Berry-Pancharatnam phase have had a total of zero specious answers and so they have zero bad voting. This is an example of the system working just fine as it is. The reason it works is because non specialists aren't interested in such arcana and can't speak the language, much less form an opinion. Lily pads and railroad tanks they (think they) understand. $\endgroup$ – Carl Brannen Jan 21 '11 at 6:05
  • $\begingroup$ I have no idea why anyone would down-vote this answer. It would at least be minimally decent to give some sort of a feedback. Its not as if this answer is in martian. $\endgroup$ – Deepak Vaid Jan 21 '11 at 6:11
  • $\begingroup$ @space_cadet: I downvoted this answer and I posted a comment. Downvotes don't mean the same in meta than in the parent site. $\endgroup$ – Robert Smith Jan 21 '11 at 6:41
  • $\begingroup$ By the way, in case it is important (although I don't know to whom), I disagree with the third, fourth and sixth paragraph, and I agree with the first and second paragraph. $\endgroup$ – Robert Smith Jan 21 '11 at 6:45
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    $\begingroup$ I downvoted because of this "the primary purpose of this site, just like the evening news, is entertainment, not truth." I would give it -10 if I could. If you want to be entertained I suggest other websites. The purpose for me is the exchange of (useful) information, meaning staements that are true within the framework of physics. $\endgroup$ – TROLLHUNTER Jan 21 '11 at 7:28
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    $\begingroup$ For me, the purpose of physics in general is entertainment! (+1) $\endgroup$ – Mark Eichenlaub Jan 21 '11 at 7:42
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    $\begingroup$ @Mark That is a really ugly statement, what you mean is that you do physics for entertainment, but that is not the general purpose of physics, and should not be the purpose of this site. $\endgroup$ – TROLLHUNTER Jan 21 '11 at 7:49
  • $\begingroup$ @kakemonsteret "in general" was stipulated with "for me". There has been a communication failure here that hopefully will cause no further strife! $\endgroup$ – Mark Eichenlaub Jan 21 '11 at 7:52
  • $\begingroup$ @kakemosteret - physicists stress their brains more than the average and so they need a corresponding amount of release. You know what happens to an overheated engine, right? BOOM! $\endgroup$ – Deepak Vaid Jan 21 '11 at 8:59
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    $\begingroup$ Let me detail what I mean by "entertainment". Stack Exchange is owned by <a href="stackoverflow.com/about/management">a private corporation</a> that was funded by venture capital. Like the evening news, the purpose of this site is to make money. See joelonsoftware.com/items/2010/02/14.html to understand the money reason why this site exists. What it needs is eyeballs not truth, and to get eyeballs the recipe is entertainment. (By the way, I also find physics very entertaining. And I don't fool myself by believing that I'm in possession of the truth.) $\endgroup$ – Carl Brannen Jan 21 '11 at 9:19
  • $\begingroup$ @Carl: while what you say about money makes sense, it is we (the community of physicists) who decides how this site is to be run (of course, ultimately it is run on SE servers but judging from other sites they don't interfere at all). And while occasional entertainment definitely doesn't hurt I can't understand why any honest physicist would like to promote bad answers instead of the correct ones just because they are more popular. I am not saying that it is easy to dispose of those bad answers but it is definitely something we should be striving for. $\endgroup$ – Marek Jan 21 '11 at 13:15
  • $\begingroup$ @Marek; (1) The stack exchange moderation system is run by people who have high reputation, they may or may not be physicists. Something like 1/3 of the high reputation users are identifiable: physics.stackexchange.com/users Some of these may be identifiable as physicists. Some may be using others' names. The other 2/3s are anonymous. The statistics probably go for the rest of the users. $\endgroup$ – Carl Brannen Jan 21 '11 at 23:10
  • $\begingroup$ @Marek; (2) A real question is what promotes people to press up or down buttons. I have to suspect that, as with everything else humans do, there is an entertainment factor. $\endgroup$ – Carl Brannen Jan 21 '11 at 23:11
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    $\begingroup$ @Carl: there is not a big difference which is why I don't understand your sentiment at all. Look at MathOverflow: it is a place for gathering of professional mathematicians and students and it works wonderful. There is no garbage on that site. So the SE system can work but it needs its users to be genuinely interested in the main goal (which is good science here) and not entertainment (not that the two must be exclusive; like for Mark, good science is also for me a good source of pleasure). $\endgroup$ – Marek Jan 23 '11 at 8:16

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