This is a proposal that has been discussed to some extent in the h bar chat (especially with @ACuriousMind and @alemi), and a meta post to gauge the response of the rest of the community is long overdue, so here we go:

All long-time SE users are aware that there are always a number of questions that come up again and again. Physics.SE is no different in this respect: Who hasn’t sighed at the sight of yet another variation of the twin paradox from SRT? This is a proposal to try to deal with this phenomenon in a thorough way.

Proposal: We, as a community, create a set of ‘canonical questions’, well written and comprehensive questions which cover the essential points of questions that come up frequently. These canonical questions must have a set of good answers. The answers to the canonical questions should address the questions at different level, with answers ideally ranging from high school to graduate school (and up!) level, where possible.

There are two main ways that these canonical questions can be created. Firstly, we can edit existing popular questions (many candidate canonical questions can be found in the ‘frequent’ tab of questions) to make them more comprehensive, and add more/improve existing answers so they become even more useful. Secondly, we can make a couple of new questions with the express purpose of canonizing them. This would be similar to what John Rennie did here, except with more answers, and perhaps a more thorough formulation of the question.

Anybody interested should probably scan these relevant blog posts: (thanks, alemi, for the excellent research):

http://blog.stackoverflow.com/2011/08/the-future-of-community-wiki/ http://blog.stackoverflow.com/2011/01/the-wikipedia-of-long-tail-programming-questions/ http://blog.stackoverflow.com/2010/11/dr-strangedupe-or-how-i-learned-to-stop-worrying-and-love-duplication/

...and most recently, one that seems very encouraging:


I guess I am mainly looking for answers that address the following questions: Do you think we need this, and is it worth the effort?

The reception in chat was quite positive, but maybe some of you have reasons to believe that this might be a bad idea, or perhaps just too much effort…

Side note: We initially considered using the ‘faq’ tag - but DavidZ has made it clear that this tag should not be used, because it really should be burninated.

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    $\begingroup$ I might give a longer answer later, but for now: O support this. Regarding the faq tag, it's one of the few meta tags that's used on many SE sites, and is IMO an okay tag to have -- it's for a very specific and rare type of question and should be removed from anything else. $\endgroup$ Aug 14, 2014 at 21:59
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    $\begingroup$ Oh, I didn't mean to be so authoritative when talking about the faq tag - my opinion is that it's a meta tag and we shouldn't use it, but I suppose the community could decide differently. $\endgroup$
    – David Z
    Aug 15, 2014 at 1:55
  • $\begingroup$ I sort of tried to do that in this one: physics.stackexchange.com/q/100864 $\endgroup$ Aug 15, 2014 at 11:40
  • $\begingroup$ @EmilioPisanty ...as with the question about units you posed a while back, right? I know that people have done these things before, but didn't find it very useful to compile a big list until we are sure that this plan will go through. $\endgroup$
    – Danu
    Aug 15, 2014 at 11:47
  • $\begingroup$ This one was slightly different - there weren't any duplicates, and still aren't any similar ones as far as I'm aware. But I did want to make something fairly definitive that people could refer to. Also - not hugely vote-successful but it does have a good bit of views. $\endgroup$ Aug 15, 2014 at 11:50
  • $\begingroup$ I like this in principle - it is a worthwhile goal. The problem I see: either they are community wiki (in which case there is "no reward" for editing them) or not (in which case people may be less inclined to make other answers better). As John Rennie pointed out, you need some people "on a mission" to make this work. But there are some excellent and generous physicists on this site… so it just might work. $\endgroup$
    – Floris
    Aug 15, 2014 at 12:08
  • $\begingroup$ @Floris I wouldn't call myself 'excellent', nor 'generous', nor 'physicist', but I think am definitely up for this challenge :) $\endgroup$
    – Danu
    Aug 15, 2014 at 12:41
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    $\begingroup$ @Danu - just for saying you are up to the challenge, you meet the second adjective. Most of the problems that fall into this category can probably be answered by someone with an undergraduate degree in physics - so I think you qualify on the third count. As for the first… let's see you tackle some answers and the community will let you know. I don't consider myself qualified to pass judgment… :-) $\endgroup$
    – Floris
    Aug 15, 2014 at 12:51
  • $\begingroup$ See also The Original Usenet Physics FAQ math.ucr.edu/home/baez/physics $\endgroup$
    – b_jonas
    Oct 3, 2014 at 6:41
  • $\begingroup$ Re the Physics FAQs, see this. What happens when the "canonical" answer is flatly contradicted by it? Do we end up with certain posters deleting anything that challenges what they decree to be the one true truth? There's way too many close votes on PSE already. All too often when you follow up the alleged duplicate it isn't a duplicate, and/or the answers are either non-answers or poor, or wrong, and it's always the same old names. Which is why this proposal is a can of worms. $\endgroup$ Nov 10, 2015 at 14:34

3 Answers 3


I have no objection to the proposal so I'm not going to vote it down, however I'm not sure how well this is going to work in practice.

If you take the Q/A of mine that you link, I wrote this mainly for personal reasons. I had finally got around to working though the analysis of acceleration in Chapter 6 of Gravitation and was feeling really proud that I'd successfully worked through all the derivations that the authors assume are obvious. It was on this wave of smugness that I decided I just had to share my new found understanding. While I'd like to say it was to create a valuable resource for the site, this was a fringe benefit rather than a prime motivator. I have several times linked the question as a duplicate, but only several times, not hundreds of times, so I'm not sure it's made that much difference to the day to day working of the site.

My point is that I think we'll only get really good Q/A blogettes if someone decides they're on a mission to write them. I'm not sure that trying to draw up a list of potential subjects will work. Certainly, my response to being handed some random subject to write a Q/A on would be lukewarm at best. Particularly if it was going to be a Community article and I wouldn't even get any rep points for my efforts (the Q/A I wrote took me the better part of a whole day if you include all the tinkering with trial calculations in spreadsheets).

So while it would be great to see more of this type of Q/A I think we should leave it to people to decide that they just can't live without writing about their current obsession. By all means provide encouragement, but I just don't think writing by committee will produce great articles.

Having said this, a Q/A about time dilation and the twin paradox has been simmering away in a corner of my mind for some time now ...

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    $\begingroup$ Aha, so that's where that came from! I had expected a response along these lines from you, and I agree that perhaps the biggest potential problem is whether people would be willing to put in the effort necessary to make this happen. I think it should be possible. $\endgroup$
    – Danu
    Aug 15, 2014 at 10:14
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    $\begingroup$ my 0.5 cents in this little discussion, well the answer is obvious, duplicates (and probably lots of them), batch them up in a list (ordered by popularity maybe) and server them ready for any new duplicates, much like youtube automatically creates playlists, only this can be semi-automatic. Then no need is to write new 'cacnonical posts' to 'canonical questions', they are already there written and voted. Just make them into a list (per related topic) and serve them to anyone interested $\endgroup$
    – Nikos M.
    Aug 16, 2014 at 17:02
  • $\begingroup$ Plus i would add, people may use a title seemingly related to duplicate/canonical question, yet many times they just need another perspective (or variation if you like) on the same theme $\endgroup$
    – Nikos M.
    Aug 16, 2014 at 17:05
  • $\begingroup$ It's funny how, in the end, you're the one person actually writing these canonical posts! $\endgroup$
    – Danu
    Mar 6, 2016 at 19:13

We've already got one of these:

How long would it take me to travel to a distant star?

John Rennie posted that because there wasn't a good covers everything answer (if I recall correctly, if this is wrong, please correct me) about the question.

I would be okay with these types of questions & answers, but I think that they should be made a community wiki.

  • $\begingroup$ I am aware of that question. There is a similar one about unit conventions by Emilio. I have also thought abput the community wiki issue, but wanted to leave it up to others to voice their views on this matter (and perhaps this debate should be postponed until it is clear whether this plan is going through or not, along with a view other points). $\endgroup$
    – Danu
    Aug 15, 2014 at 0:50

It’s physics. There are not so much repeated (actually) questions, but there are several topics prone to misconceptions, such as:
• Time and mass in Special Relativity.
• Electric charge vs electric potential.
• Field potential vs field strength (mainly E-M and gravity).
• Charge carriers in conductors and semiconductors – a bunch of misconceptions.
• Mass number of a nucleus vs its mass vs the atom’s mass.
• Temperature vs energy.
• Singularity of the spacetime vs event horizon.
• Field superposition vs quantum superposition.
• Coherent quantum superposition vs mixed states (statistical superposition).
• State vector reduction a.k.a. wave function collapse – a bunch of misconceptions.
• Transition between quantum states.
• Continuous operator spectrum and eigenvectors/eigenfunctions/eigenstates.
• Composite particles and the size of a particle – a bunch of misconceptions.
Although such misconceptions are known to develop with a high probability, we can’t predict in which exactly form such a misconception will be submitted as a question. Why don’t have an index of misconceptions with brief explanations and links to relevant educational resources?

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    $\begingroup$ " there are not so much repeated (actually) questions " I think perhaps the view of the duplicate list of this famous question could change your mind. $\endgroup$
    – Danu
    Aug 16, 2014 at 9:40

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