# Is my question about three-body orbits and conservation laws on-topic here and is this a good place to ask it?

I've asked Can there be an energetically unbounded three-body orbit where escape is impossible due to conservation of angular momentum? and I'm pretty sure that it

• is a mathematical problem
• if anyone has solved it, it will have been a mathematician

I was surprised to see that after two days there are no answers nor even comments. Is there any chance that my question while not off-topic is not really the kind of question that gets answered here, or that the answer is so trivial that people are being polite by not answering? Or is it so difficult that the answer simply isn't known?

Sometimes its difficult for me to judge these things so I thought I'd ask here.

note: I'm looking for a definitive answer and guessing that it would be in the form of a reference to a mathematical proof from a long time ago. In another SE site I might get an answer "probably not" which gets highly up voted and then I'm left with a question that people feel has been answered yet I'm left not knowing for sure.

It is this quest for certainty that lead me to choose Math SE to post.

• My first reaction would be that people at Physics.SE would be better placed to answer that question. May 6, 2020 at 5:27
• @JyrkiLahtonen thanks, I'm curious why mathematicians might therefore be worse placed, do you think this kind of dynamical systems problem is too niche perhaps?
– uhoh
May 6, 2020 at 6:06
• @uhoh I don't think that the problem is that it is niche. I see two problems with the question: (1) it really is about physics, not mathematics. It is phrased as a physics problem, and relies on a moderately extensive understanding of the jargon and ideas from physics. It appears to me that a great deal of work would need to be done in order to refocus the question s a mathematics question. (2) Too much of the question is buried behind links. The question is not really very self-contained (though this is likely due to the heavy reliance on ideas that physicists "just know"; see point (1)).
– Xander Henderson Mod
May 6, 2020 at 15:08
• @XanderHenderson Thanks for your comment. I have a hard time believing that more than a tiny fraction of Math SE users here would stumble when faced with conservation of angular momentum or think of it as "jargon"; it's something most people see in high school. "Closed and periodic" is something that anyone whose touched on dynamical systems would instantly recognize, no?
– uhoh
May 6, 2020 at 15:35
• @XanderHenderson The question that guides us when we chose which site to ask a question (beyond "Where is this not off-topic?") is What kind of answer do I want? I think the answer to this needs to be in the form of a mathematical derivation or proof, (hopefully this has been done a long time ago and we just need to find a citation), not an explanation of physical insight. As I discuss at the end of the question, I'm looking for certainty in an answer, and that points me right back to Math SE.
– uhoh
May 6, 2020 at 15:43
• @uhoh The point is not that the question cannot be solved by a mathematician. The point is that the question is phrased as a physics question. You have not reduced the problem to a mathematical one, which might be something of the form "Define energy [this] way, and suppose that a body moves according to [that] process. Is it possible for the body's position to remain bounded while energy goes to infinity?" where [this] and [that] are described in notation (or some approximation thereof).
– Xander Henderson Mod
May 6, 2020 at 22:50
• As your question is currently written, one must take off their mathematician hat and put on their physician hat to read it. Like I said, I think that the question can be phrased in such a way that it is a mathematical question, but in its current state it reads like a physics question. In any event, you should also consider that the people who are intimately familiar with these kinds of dynamics are likely to be physicians. Their the ones who are likely to have an answer top-of-mind. I think that you are more likely to get an answer on Physics.
– Xander Henderson Mod
May 6, 2020 at 22:51
• @XanderHenderson meta questions occasionally lead to policy changes; should all questions on this site that "read like a physics questions" be closed until they are reduced to purely mathematical questions, or can the site continue to answer them? Consider that the physics tag currently has 4,486 questions! Also please note I've made it clear that it's the kind of answer that I might receive that steered me to Math SE, not simply the likelihood of receiving an answer.
– uhoh
May 7, 2020 at 0:22
– Xander Henderson Mod
May 7, 2020 at 5:22
• @XanderHenderson I'm looking for a definitive answer, not just a site where answers are posted quickly. Sometimes SE questions are answered months or years later; three days is not a long time at all. (double check the note in this question)
– uhoh
May 7, 2020 at 6:09
• Look, you asked if your question was on-topic here. I told you that it really isn't---you haven't highlighted the mathematical crux of the problem and have phrased the question as a physics problem. I, and several other people, have told you that you are unlikely to get a good answer here. I don't know what else to tell you---if you were not prepared for a negative answer to this meta question, then why ask it?
– Xander Henderson Mod
May 7, 2020 at 14:47

Your question is well-received (4 net upvotes so far) on the main site. I would certainly consider it on-topic. It may be less accessible to users who don't have a physics background though.

That said, if I were you, I would focus more on how to get a satisfactory answer to the question, instead of worrying too much about reasons why it has not received any answers. There are lots of interesting unanswered questions among the site.

One thing worth of knowing is that some big fish never (or no longer) participate in meta. Users who can answer your question may not know your question at all.

There are several things you can try.

• There is a chat room called Pearl Dive, where there are high rep users who are willing to set bounties, as large as 500, to draw attention to posts that they consider excellent. Your answer has been viewed only 100 times so far. Adding a bounty may help. You can also do it on your own.
• You can definitely try Physics or MathOverflow, explaining your situation and where you have posted your question. Asking a question that may not be appropriate for certain sites is not committing a crime. You don't need anyone's "blessing" (as you commented) to ask as long as you have made your own effort to be on-topic. At worst, your post may be closed and or deleted. But there are chances that people leave valuable information for you.
• You can also try to rephrase your problem. Questions in dynamical systems can be phrased in a completely mathematical way that no physics is explicitly seen. Experts in differential equations (who may know less physics than physicists) may get more interested in your question.
• Thank you for your very thoughtful and helpful answer; I'll look into all of these options.
– uhoh
May 7, 2020 at 14:50
• +1 especially for 'There are lots of interesting unanswered questions'. May 7, 2020 at 16:46