I am very disappointed by my experiment on this site. Four days ago, I posted this question: Numerical simulation of the double-slit experiment including watching the electrons . After less that 24 hours, it was put [on hold] by 5 persons as being unclear. So I edited my question a first time in the hope the [on hold] would be removed so that people can answer it, unfortunately it remained in the [on hold] state. I read from the rules that "Questions that are not reopened within five days will change from [on hold] to [closed]", so I went deeper in reading the rules from page https://physics.stackexchange.com/help/reopen-questions where it is suggested to re-edit the question and "Flag the question for moderator attention. Again, explain why it should be reopened. There is more than one moderator, and moderators do reconsider their decisions". So I followed these steps, re-edited the question a second time and flagged the question, explaining the moderator why in my opinion the question should be reopened. I was then surprised to get the following answer from a moderator: "declined - flags should only be used to make moderators aware of content that requires their intervention". Hence either he or me does not comply to the stackexchange policy... being novice here I guess that it is my fault, but could someone explain me what I did wrong?

All in all, I am very disappointed: I have now spent many hours having to justify myself for asking a question which, unless I am completely stupid, has clearly some interest, and lost hope of getting an answer. I write it here again for information:

The double-slit "thought experiment" described by Feynman in Lectures on Physics Volume 3 section I-6 Watching the electrons consists in firing electrons through a double-slit to observe the interference of electron waves, and watching them after passing the slits with a light source placed behind the double-slit, at equal distance of each slit. As electric charges scatter light, one can "detect" which slit the electron went through if the photon wavelength is small enough.

Question: has this "thought experiment" been simulated by solving numerically the underlying Schrödinger equation? I am aware about numerical experiments of the double-slit, but did not find any including the interaction between the electrons and the photons just after the double-slit.

The numerical simulation can address other types of particles, the crucial point being the simulation of the observation (here the photons being scattered by the electrons) and its effect on the wavefunction. Its interest could be in particular to better understand in which precise way the observation progressively becomes inoperative when the photon wavelength increases.

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    $\begingroup$ Your disappointment is perfectly understable, I have the same feelings. Don't worry, you are right. If you would remain here, later, after collecting some reputation you could help our close/delete voters into a more clear and fair direction, with your votes. Until that, you can explain to them, that maybe a little bit more effort to answer the question combined with a more predictable and lenient review mechanism would be highly useful for everybody. $\endgroup$
    – peterh
    Commented Sep 22, 2016 at 13:29
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    $\begingroup$ @peterh: thank you for the kind words, very much appreciated. $\endgroup$
    – user130529
    Commented Sep 22, 2016 at 14:04
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    $\begingroup$ Your question is now (as of this writing) reopened. $\endgroup$
    – Rococo
    Commented Sep 23, 2016 at 6:01
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    $\begingroup$ @Rococo Thank you, you made my day. $\endgroup$
    – user130529
    Commented Sep 23, 2016 at 6:47

1 Answer 1


Questions which are edited are put into a queue to be reviewed for reopening. This is the primary mechanism by which questions get reopened after being put on hold. Flagging for moderator attention is a backup option, to be used when the review process isn't working - either because the question is too old to be reviewed, or, if you really believe that the outcome of the review process was wrong and have a good argument for it, you can make that case in a flag.

However, in your case, the review hasn't been completed. It's not time to invoke the backup option yet. So your main mistake was flagging immediately after you edited. That being said, a declined flag isn't a big deal. When a flag is declined, it means the mods are just advising you to avoid flagging things like that in the future. In this case specifically, avoid flagging questions for reopening without waiting for the review. (Though to be fair, this review has been sitting around incomplete for quite a while.)

There are a couple other things which I would advise you to do differently. First of all, you didn't actually explain a reason for reopening the question in your flag reason. If you want a moderator to reopen a question, your best bet is to briefly mention in the flag reason itself why the question should be reopened. This can be very simple; for example, "I've edited the question to clarify the issues brought up in the comments."

Secondly, the way you worded your flag message is rather rude. Flag messages are considered private, so our normal "be nice" policy doesn't apply to them as strictly as it would apply to public posts, but bear in mind that when you cast a flag to ask someone for help, they will be more willing to help if you do phrase the message politely, and they will be less willing to help if you are impolite.

Here is one example of how you could write a perfectly reasonable flag message for when you want a question reopened:

Edited to address the issues brought up in comments; the question should be clear now, but I have been waiting a long time since the edits. Could you review this for reopening?

  • $\begingroup$ Thank you David Z for your answer. I hadn't realize being rude, sorry for that (I wanted to check again my flag but it now disappeared). I will put a new flag following your suggestion. $\endgroup$
    – user130529
    Commented Sep 22, 2016 at 12:35
  • $\begingroup$ Well, it seems I can't flag the question again, it seems I better give up. $\endgroup$
    – user130529
    Commented Sep 22, 2016 at 12:45
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    $\begingroup$ The review is still ongoing, and this meta question is going to bring a good bit of attention to your post, so I'd say just leave it for another day or so. $\endgroup$
    – David Z
    Commented Sep 22, 2016 at 12:58
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    $\begingroup$ @claudechuber Or you can keep waiting for the review queue to finish with it. Although I will say, I don't know that the question is a good fit still. I mean, it can be answered with a "Yes, it has been simulated, here's the reference" or "Nope, sorry, it hasn't been simulated" and that's not really the kinds of questions that are received well here. But, that's just my opinion. Others may disagree. I did not cast a vote in the queue one way or the other. $\endgroup$
    – tpg2114
    Commented Sep 22, 2016 at 12:59
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    $\begingroup$ @tpg2114 I dunno, I think those sorts of questions are fine, in general, as long as they don't come across as lazy. But let's not get into a discussion about the merits of that general type of questions here; it'd be a matter for a separate meta post, if anyone cares to bring it up. $\endgroup$
    – David Z
    Commented Sep 22, 2016 at 13:05
  • $\begingroup$ @David Z: thank you for the recommendation. $\endgroup$
    – user130529
    Commented Sep 22, 2016 at 14:24
  • $\begingroup$ @tpg2114: I understand your point, it does look like a reference request and people may think "let him do the job like all of us and search in journals". However I am not asking this for personal academic purpose but for pure curiosity: this double slit experiment is such a key experiment in quantum mechanics, and such a challenge for the common intuition, that I think the existence of a numerical simulation of the observation could interest many people and shed light on what's happening once the wavefunction has passed the two slits and has been "observed". $\endgroup$
    – user130529
    Commented Sep 22, 2016 at 14:27
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    $\begingroup$ @claudechuber - if you think it's interesting for the site, nothing would prevent you from answering your own question... and I see it's now not only re-opened, but has attracted a significant bounty. $\endgroup$
    – Floris
    Commented Sep 26, 2016 at 18:04
  • $\begingroup$ @Floris Thank you for the suggestion, but unfortunately I don't know the answer (I wish I would). Nevertheless, following this question, I had a very interesting chat with Norbert Schuch. Yes, I saw the bounty, nice! $\endgroup$
    – user130529
    Commented Sep 26, 2016 at 20:15

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