Tell me this isn't happening... The Astronomy and Astrophysics site is in the commitment phase at 65%. That site is going to bring fragmentation and general loss of quality to the Physics site. Just have a look at some of the Top Example Questions:

  • What happens if two black holes collide? (this is the top one!)
  • Why do sunspots appear dark?
  • Does the cosmic microwave background radiation (CMBR) prove the Big Bang?
  • How are extrasolar planets detected?
  • Why can't light escape from a black hole?
  • What are the Lagrangian (libration) points?

When that site reaches 100% support and is created, what will happen with such questions? Will they be migrated there? Who will wrongly decide that the collision between two black holes is not for theoretical physicists but for astrophysicists? What is wrong with this site we have now, for such questions? Why that fragmentation? Hey, and I am myself an astrophysicist.

Please tell me what can be my contribution in order to help that separate site not to be created. I can see there only options to join the supporters, but I want to do the opposite...


Thanks to the suggestion of @Manishearth, I have made my contribution, by posting my opinion there in Area 51. Perhaps this helps convincing some potential supporters. You are encouraged to post your opinions there too.

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    $\begingroup$ It does seem like a great many of the Astronomy and Astrophysics questions belong here but I can imagine a wide variety of questions related to hobbyist activities that don't belong here. It seems to me the biggest issue with the proposal is their sample questions and not the idea overall. $\endgroup$ Commented Apr 23, 2013 at 21:53
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    $\begingroup$ @Brandon any examples of such hobbyist questions in mind? After all, astronomy and astrophysics is explicitly part of this site's scope. $\endgroup$
    – David Z
    Commented Apr 23, 2013 at 21:54
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    $\begingroup$ @DavidZaslavsky I'm not a hobbyist however I'm expecting questions about good telescopes, good viewing times, dealing with keeping mirrors cool, and all sorts of non-theoretical Astronomy hobby questions that we'd never accept here. $\endgroup$ Commented Apr 23, 2013 at 21:56
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    $\begingroup$ @DavidZaslavsky but as for Astrophysics, I think we'd probably be the best place for those. $\endgroup$ Commented Apr 23, 2013 at 21:56
  • $\begingroup$ Ah, yes... I think there's some discussion on this meta of what would be done with telescope questions etc. from the old Astro site. $\endgroup$
    – David Z
    Commented Apr 23, 2013 at 21:57
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    $\begingroup$ I think telescope questions are well here. Not all is theoretical physics here. During a normal physics degree you have lectures about optics and geometrical optics, and you learn about microscopes and telescopes as well. I think that questions about observing sites and such amateur astronomy questions could be here with no particular problem. I don't know what others think. $\endgroup$ Commented Apr 23, 2013 at 22:14
  • $\begingroup$ One thing is important, and that goes for you David and the other moderators: if that Astro-ruining-site is eventually created, will you be forced (as moderators) to migrate questions there, or will it be possible that, for instance, you respect my will that my questions stay here, no matter "how astrophysical" my questions seem? That is the least, although I alone won't be able by any means to reduce the loss... $\endgroup$ Commented Apr 23, 2013 at 22:17
  • $\begingroup$ @BrandonEnright, there may be some questions very specific about amateur astronomy (I can imagine "How can I clean my primary mirror without damaging its coating" or "Is it bad to drink coffee before observing for the ability of your eye to adapt darkness?") but it is less bad to accept them here than having that separate site... I see a lot of damage in the second option. $\endgroup$ Commented Apr 23, 2013 at 22:23
  • $\begingroup$ We won't be forced to migrate existing questions from this site to the other one. (To be frank: not because it's what you'd like, but because that is SE policy/tradition/whatever.) However, we as a community would probably be expected (if not exactly required) to adjust our site's scope so that we're not competing with the other site for future questions. $\endgroup$
    – David Z
    Commented Apr 23, 2013 at 23:45
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    $\begingroup$ FYI @Brandon my understanding is that Eduardo is correct, telescope questions and other observational astronomy questions are on topic here. They rarely seem to get asked though. $\endgroup$
    – David Z
    Commented Apr 23, 2013 at 23:48
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    $\begingroup$ @DavidZaslavsky Interesting. I wonder if that's because people assume that they're off topic when they aren't. If that's the case then I think the proposed Astronomy.SE is almost entirely redundant. $\endgroup$ Commented Apr 24, 2013 at 0:06
  • $\begingroup$ @Brandon that's my hypothesis. After all there's very little about this site that suggests astronomy questions are on topic, except that one line in the FAQ. (Which is why I proposed this, although SE is not willing to do that anyway) $\endgroup$
    – David Z
    Commented Apr 24, 2013 at 1:10
  • $\begingroup$ @BrandonEnright: No, they knew that it was on topic here. SE allows subset sites, though IIRC they deal with them much more strictly when it comes to closing. $\endgroup$ Commented Apr 24, 2013 at 6:14
  • $\begingroup$ @Manishearth (6 months later) I see you are active on that beta site and already with 1.4k reputation (???) Well, it is of course your personal choice (you may not agree with my point of view about the damage of fragmentation to the physics site), but I wish you had waited until the end of the beta stage. $\endgroup$ Commented Oct 7, 2013 at 16:18
  • $\begingroup$ @EduardoGuerrasValera I usually join private betas and try to make them succeed even if I was strongly opposed to their creation (I did the same with Arduino.SE -- it was a proper subset of EE and I was very vocal about that). I feel that they should still be given a fair chance if they've gotten so far. If the private beta succeeds, I don't plan to stick around much after that. Also, I have posted some concerns about the fragmentation and scope on the meta site, after watching the beta unfold. $\endgroup$ Commented Oct 7, 2013 at 16:27

2 Answers 2


A bit about site overlaps

Firstly: Sites can have overlap regions. In such cases, posts only get migrated if:

  • The OP asks for migration
  • The question does not get (good) answers for some number of days

As a mod on both Physics and Chem, I come across this fairly regularly — there are posts which are on topic on two sites.

However, this isn't a matter of overlap of scope, it is a matter of being a complete subset.

Do such sites succeed?

Depends. Mathematica.SE succeeded even though it was a subset site because there were a staggeringly huge number of MMA users on SO who had no interest in the rest of SO. But TheoreticalPhysics (and, more recently, Arduino) didn't. There are a lot of situation-specific reasons for these failures, though. However, when there's an established place where you can ask stuff, there.

Note that the last Astro.SE was not a full subset of Physics.

Will Astro.SE succeed?

I don't know. Last time it failed due to low activity, and there's a high chance it will this time as well. Physics is a much larger site and tends to attract people better. I personally predict that it will be closed in private beta, but I could be grossly wrong.

Is it a threat?

No, not really. If it does succeed, it wouldn't really harm our site. Our scope would not change, so questions asked here would stay here. Maybe the number of questions we receive in the topic would be halved. Not much of an issue -- though the astronomy subcommunity (@ChrisWhite, you, etc) may be split. (When Mathematica.SE was launched in beta, the whole SO community moved over. This did not happen with Arduino or TheoreticalPhysics).

It's something that you, as an astrophysicist, may even want to look forward to. Currently it is not immediately clear that Astronomy is on topic for Physics.SE. Astrophysics — yes, but astronomy is not really a part of physics (in the minds of the general public).

If it fails, Physics.SE would be happy to accept their posts as we did the last time.

Can we do anything about it?

I posted this. Not that I want the site to fail, but if that was enough justification for the proposal to be closed (before it wasted a lot of time), so be it.

The banner you see on the top is because one of us pinged a community team member about the scope subset

enter image description here

This would help test if the site will be able to stand on it's own later -- if Physics.SE is a more lucrative option for those willing to commit, then this makes the site less likely to succeed. The community team is good at helping sites succeed, but they also are good at identifying ones which won't. They generally give such iffy cases a chance: they at least let them have a week of private beta.

There's not much more we can do: You can always post your own answer on that discussion thread.

  • $\begingroup$ Thanks!, That post is a place where at least I can post my reasons about the question! $\endgroup$ Commented Apr 23, 2013 at 22:30
  • $\begingroup$ Well, but what happens if the OP explicitely asks NOT to be migrated? $\endgroup$ Commented Apr 23, 2013 at 22:31
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    $\begingroup$ Astronomy is on topic here. It's in our FAQ. $\endgroup$
    – David Z
    Commented Apr 23, 2013 at 23:46
  • $\begingroup$ @EduardoGuerrasValera: We don't migrate by default unless it is off topic on a site. $\endgroup$ Commented Apr 24, 2013 at 6:03
  • $\begingroup$ Perhaps there is a little more we can do about it. I just posted this feature request for a technical solution: meta.stackexchange.com/questions/177783/… $\endgroup$ Commented Apr 24, 2013 at 16:45
  • $\begingroup$ @WanderingLogic: I was just reading that :) $\endgroup$ Commented Apr 24, 2013 at 16:47
  • $\begingroup$ @Manishearth I like the idea of minisites a lot, in particular for astrophysics and TP who did not succeed as full distinct sites. Is there any news concerning this idea? $\endgroup$
    – Dilaton
    Commented May 10, 2013 at 22:03
  • $\begingroup$ @Dilaton: I don't think so. The minisite experiment was for facebook.so (which was a sponsored business), and it failed. If it's the only thing that will make a community stay I'd be OK with it, but I'd rather prefer that all the subcommunities got along under the banner of Physics.SE. There never was any need for TP.SE :/ $\endgroup$ Commented May 11, 2013 at 2:49
  • $\begingroup$ @Manishearth well, most of the TP community has evaporated after the merge, the research-level for higher level questions was probably not enough to make them stay here. We heve the questions but the people are gone. With a TP minisite they maybe would come back. The same goes for the Astrophysicists who would rather try sterting a new site than post here. $\endgroup$
    – Dilaton
    Commented May 11, 2013 at 7:09

[What follows is support for the OP's concerns. If it is answers you seek, I have none to give, but if you seek to know more about this issue from an astrophysicist's perspective, read on.]

I think what is irking Eduardo, and certainly what irks me, about this proposal is how it splits off astrophysics from physics. Sure, there can be a site about amateur observing, naming constellations, etc., assuming it succeeds. But if you want answers about the science, then that is a subset of physics.

Sure there are plenty of hobbyists who are interested in the underlying physics of all the pretty pictures. But professional astrophysics and astronomy1 should be handled in a professional forum if one exists. And one already does. You don't need to be an amateur hobbyist to tell people what a black hole is or explain the CMB. In fact, most people who understand these concepts don't know how to work a personal telescope.

The problem was there used to be a site that focused on amateur issues, with the occasional hard science question asked there that should have been asked here instead. It failed due to low popularity. Instead of accepting that the Stackexchange platform just wasn't right for that group,2 they decided to steal subject matter from this site to expand their scope. How is this anything other than direct, adversarial competition?

By what logic is this proceeding anyway? Do the powers-that-be really think better answers will come from a non-general-physics site? Perhaps we should split off string theory while we're at it - after all, string theorists are less likely than astrophysicists to reside in their university's physics department. Wouldn't want any cross-contamination or exchange of ideas from other branches of physics, now would we?

I can only think of two possible justifications. Either (1) there is a belief that astronomy and astrophysics are somehow at the fringes of physics proper, not really belonging, which as an astrophysicist I can tell you is absurd, or (2) there is a belief that astro questions would get better answers on their own site. Yet if anything this new site would lean toward the pop-sci level of explanations, which we here at physics are constantly having to refute. If you want a place for really popular questions that attract hoards of people who prefer entertaining answers to factually grounded ones, well there is a site already dedicated to that.

Admittedly, this isn't an answer to the question of "how do I oppose this?" I myself am seeking that answer. But indeed I don't think the outrage has been voiced quite enough. I hope at the very least I've shown why this new site is something that should be opposed.

1 Yes, both. Astronomy is to astrophysics as particle experiment is to particle theory, as condensed matter experiment is to condensed matter theory.

2 My guess is this is probably due to the fact that there are already a large number of very enthusiastic amateur groups on and off the internet, so there is a crowding-out effect in the market.

  • $\begingroup$ Firstly, the fact that there is not much support for this from the Physics.SE Astro community does help predict how well it will go for that site. If you guys were interested on straggling both sites, then that would really help it. $\endgroup$ Commented Apr 24, 2013 at 6:20
  • $\begingroup$ Thing is, if people want a site that is a subset, SE will at lease give them a private beta. If there is overwhelming activity in the private beta, then they let it through. Many of these subset sites get proposed due to a difference of communities--that was the reason for Arduino and TP.SE. They seem to fail, and that's likely to be the case here. You're right, the only difference between the new Astro.SE and [astronomy]/[astrophysics] on Physics.SE is that the apparent target audience will be different. Which will not lead to a good site. $\endgroup$ Commented Apr 24, 2013 at 6:24
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    $\begingroup$ @Chris (+1) I agree with you. They merely want to extend the scope of their site and reach a critical mass by stealing from here. That can only put things worse for both sites. There are not so many physicists here as it may seem. Fragmentation is a real risk for this site, not to be ignored. $\endgroup$ Commented Apr 24, 2013 at 8:52

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