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    • CommentAuthorquid
    • CommentTimeNov 1st 2012

    The question Hurricanes and Navier--Stokes equation was asked a while ago and was closed quickly. It is now about to being reopened.

    In my opinion in its current form it is completely unsuitable as an MO question; but some modifications seem more reasonable, so please those in particular OP that want this question, perhaps you could at least modify/clarify it a bit.

    First, I am not completely happy with the way of closing, but I can see why this happened like this (since with a link to a comic as its only reference, its timing, and its general form it does not come of as serious question even), since at least to me the closing reason misses the point a bit, or at least it can be understood that way.

    Second, my problem with the question is that it is extremely lazzy to the extent of being actively harmful to the success. To say something specific, what is the precise role "Navier--Stokes equation" plays in this question. Some scenarios:

    1. OP actually wants to know only about Navier--Stokes.

    2. OP would in fact also be interested in answers involving any PDE and Navier--Stokes was just an example that came to mind.

    3. OP would in fact also be interested in answers involving any type of (advanced) maths.

    Moreover, it is all but hard to find something on this on the web; a minimal amount of preparation and to at least make clear what the actual goal of this question is seems more than desireable.

    What is your problem with the way of closing? Predicting hurricanes is plainly not a mathematical problem. It would be fine to discuss issues inherent to some mathematical models in metereology or asking about the mathematics used in this field. But the quality of prediction is not a mathematica issue. So I think closing this as off-topic is exactly right.
    • CommentAuthorquid
    • CommentTimeNov 1st 2012

    @Michael Greinecker: I do not have a "problem" with the way of closing, but I consider it as suboptimal if for this type of question the only reason given is

    Nice try, but not really on-topic

    And then closed as off-topic. Because this creates responses like:

    Why off-topic ? I vote to reopen. Many mathematicians work on prediction of weather.

    In my opinion this is "not a real question". The point being that there is not even enough information to really decide what is actually asked, so it is not even off-topic. The issue this creates is that then people will start interpreting it as they like. And demonstrably (and preidictably!) not all come to your and the closers conclusion that this is off-topic.

    However, it is really not my intention to criticise those that voted to close for not giving more of an explantion, as the question itself is so lazy. And, for sure, these precise 'official' reasons are anyway often a bit random.

    In my opinion any person answering any question it is good to do like this: 1) correct question 2) answer it

    "Assume a good will" - that OP intentions are very good, but he did not find the right words to phrase the question. So expert should help him to propose a corrected version of question, rather then say "go away..."

    "On MathOverflow, though, it is possible to edit the original house so that it is no longer inflammatory, while still recording the work of the firefighter. – Terry Tao Sep 8 at 18:15" ( )
    • CommentAuthorquid
    • CommentTimeNov 1st 2012

    @Alexander Chervov: there is no fundamental disagreemnt here. Still, in my opinion it is more efficient and feasible to do this beforehand (before reopening). There could be different interpretations and it would be good to know what OP actually wanted. As I explained to me this is unclear. So, perhaps let us wait until OP says something clarifying and then somebody could help if needed. Until then however I think it is better the question stays closed. That somebody improves the question, this was basically what I asked for. Perhaps you can give it a try.

    @quid "Still, in my opinion it is more efficient and feasible to do this beforehand (before reopening)"

    I vote reopen but I am not experienced to enough to correct the question - I just want to give a chance to some expert to answer it.
    I do not see need to correct original question, it is soft and it is good - so different experts may shed light on different aspects - just starting there answer by giving the corrected version of question. May be different experts can give different corrections...

    And it seems to me that if question is closed - no one will pay attention to it. Do you think someone will correct it, then write to meta - "I corrected please give me chance to answer" ? I do not think some will do it.
    • CommentAuthorquid
    • CommentTimeNov 1st 2012

    @Alexander Chervov: if it is anyway not so important what precisely is asked, I wonder why one could not just instead read any number of things one finds searching on the web with obvious keywords.

    It seems like a complete waste of effort to me to have the "question" you envision.

    This seems to me to be a perfectly reasonable question in applied mathematics, which probably has a definite answer. My guess is that the right kind of expert would quickly be able to give a correct but minimal answer. Moreover, if they felt inclined could probably give a longer answer that would be informative and interesting. Unfortunately, I doubt that any of the relevant experts read mathoverflow, but I would be happy if they did.
    • CommentAuthorquid
    • CommentTimeNov 1st 2012

    In view of the last contribution, I stop particpipating in this debate, as it seems completely pointless.


    I am leery of questions which ask Can Famous Thing Do X and give the impression that the asker is less interested in Less Famous Things To Do With X. Still, I have some sympathy towards Neil Strickland's take, even if I have misgivings that this particular questioner is likely to ask "can ABC be applied to code-cracking"?

    (More to atmospheric modelling than Clay Millionses, from my limited understanding)


    The 'nice try...' comment was mine, and my reason for closing was along the lines of Scott Carnahan's comment, namely that anyone with a modicum of experience in applied mathematics would know that the Navier-Stokes equations would only form a tiny part of any realistic model of a complex weather system. Also the famous problem with Navier-Stokes, which I hazard a guess the OP had in mind, is of course asymptotic solutions, which is somewhat irrelevant to finite-time predictions.

    That the answer to the question as asked is 'Uh ... no', for the trivial reasons in the previous paragraph, hints to me that the question is not a good question. I also agree with Yemon's comment about 'Can Famous Thing Do X?' questions.

    If the questioner had asked about what sort of PDEs or analysis or techniques lie behind the modelling of complex weather systems, such as hurricanes, then I would have thought the question quite on topic. But that was not the question asked.

    PS I can't remember which reason for closing I chose, but I agree now with quid that 'Not a real question' seems better than 'Off-topic'.

    • CommentAuthorWillieWong
    • CommentTimeNov 2nd 2012 edited

    For me, it is rather hard to decide.

    Reasons for it to be closed:

    1. The question (see quid's first post in this thread) itself can use some clarification, especially in regards to which kinds of answer the questioner expects and what kinds of background the questioner already has.
    2. The one sentence question with minimum research effort shown really smells like a "tell me about X" question that we explicitly discourage in our "How to Ask" page.

    Reason for it to be open:

    1. I am a bit of a softie when it comes to applications of PDE questions.
    2. A proper answer to this question (something expanded and along the lines of what DavidRoberts wrote in this thread or what Scott Carnahan wrote in his comment) would help dispel the misconception that the answer to one of the Clay problems will have direct applications to weather prediction. To a large extent this misconception can be blamed on the researchers in the field (PDE in general and fluids in particular): when writing grant applications or talking to reporters it is hard to resist bringing in the "bigger picture" when talking about applications of the mathematics. (It is not just mathematics, we see this in all basic research: there are times when it is appropriate to lie a little in an elevator pitch to sell one's research.) So it would be somewhat appropriate for the field to clean up the mess that it made in the first place. (Of course, MO is not necessarily the best platform for this.)

    Which is why I didn't vote one way or another.

    That said: @DavidRoberts: I wish you had included your justification in your first comment. Clearly the OP does not have "a modicum of experience in applied mathematics" and I feel that it is always better to explain than to be dismissive.

    • CommentAuthorgilkalai
    • CommentTimeNov 2nd 2012
    Hi guys, I tried to improve a little the question. (I noticed also we dont have a tag of "applied mathematics" but maybe I missed something...)
    I don't understand. Why doesn't the OP revise the question? Why does the OP have to wait for others to do it? As I am writing this, the OP was last seen "27 mins ago."

    With such questions where some think "There's a good question here if only we could dig it out" I would far rather that someone who can see the good question write an entirely new question than try to edit the old one. If the original questioner can edit their original one then that's fine, but I think that if someone else is going to do it then it is better to shed the baggage of the bad question and ask a completely fresh one.

    I agree with Andrew Stacey's comment above.

    I would like to no whether recent advances in algebraic geomtry kan help us to predick when the universe will end.

    Will someone help me to flesh out this question for posting on MO?

    • CommentAuthorfedja
    • CommentTimeNov 2nd 2012
    The short answer to the original question is "Yes, better understanding of the mathematical issues involved will improve our predicting powers and No, there is a principal limit in predicting the weather phenomena because the corresponding system of equations is exponentially unstable". After that, all we can really do is to send the person who asked to study some math. by himself.

    @Bill. Yeah, I can help with it if you are really interested :).
    • CommentAuthorquid
    • CommentTimeNov 2nd 2012

    After Gil Kalai's edit, I voted to reopen. (Mainly out of general respect for his efforts related to such matters, but also as the current form seems like a reasonable question; still not one I think is really suitable for MO, but as there seems to be some interest by a couple of people beyond OP, why not.)


    I've also voted to reopen, as now there is the possibility of interesting answers.


    At the time of my first comment, I thought the OP had put similarly little effort and was just cherry-picking. More explanation on my part would have been better, I agree...

    Technical question, may be stupid:

    I thought that NS equation for INcompressible fluid,
    but the atmospheric air is compressible.
    So it is probably not NS equation used for weather forecasting, or I am wrong ?
    • CommentAuthorquid
    • CommentTimeNov 3rd 2012

    @Alexander Chervov: yes, in priciple it is for incompressible, however roughly speaking if no compression is happening one can still use it. As Willie Wong hinted at Navier-Stokes (and/or variations thereof) indeed is used as part of (certain) models for the phenomenon in question. (Breaking my annouced absence of the debate: This is also why I found the original form of the question basically impossible; semi-naively it is not so natural to ask about Navier-Stokes in this conext, so either we are a facing a completely naive question or a specialized one [which of course would be fine but this seemed very unlikely and for this much too few details were given]; in any case not a reasonable general interest one.)

    @quid so you mean that it is reasonable (to some extent) assumption that air is incompressible ?
    • CommentAuthorquid
    • CommentTimeNov 3rd 2012

    @Alexander Chervov: yes, I believe in certain contexts (in particular if the speeds are not too high). But I am unfortunately not firm on all this. Yet an additional issue is what one even means precisely by 'the Navier-Stokes equation'. After all various equations sort-of go under Navier-Stokes equation, eg there is also a 'compressible Navier-Stokes equation'. (The Millenium Problem one is a "clean" one but there are more general ones with additional stress terms and so on.) In brief, if somebody just asks about PDEs generally in this context then this is a reasonable general question to me, if somebody insists on Navier-Stokes then I start scratching my head what is meant, and why Navier-Stokes is singled out.

    And I am against guessing intention too much; there is also a value in MO questions generally being taken as written; as opposed to math.SE, sometimes at least, where just recently I observed somebody asking on a conjecture on difference between primes (also) there, and instantly somebody commented "did you mean sum?" because like Goldbach is more well-known or so I guess. And, even on MO it can happen and cause problems that people interpret questions too freely. Just yesterday I think somebody asks for a reference, and gets a proof as a reply. This can be just as good or even better. But in this case OP was unhappy about this because they actually wanted just a classical quotable reference.

    Mathematical aspects of meteorology. In Russian. Course notes for undergrads of Moscow Mexmat.
    • CommentAuthorgilkalai
    • CommentTimeNov 4th 2012
    Was the question deleted? this looks a little extreme...
    Agree with Gil Kalai.
    • CommentAuthorquid
    • CommentTimeNov 5th 2012 edited

    To already delete this question seems more than a bit extreme to me. (If I did not miss anything happening there, and if it was not done by moderators, I consider this basically as an abuse of deleting-powers. After all it still had some not so bad chance of getting reopened.)

    Perhaps the OP deleted it?

    Joel: no, it was deleted by three users with a sufficient number of reputation points.

    I don't see the point of deleting it.

    I've just cast the second vote to undelete.

    @quid. Why don't you reveal who you are? IMO it is completely inappropriate for an anonymous poster to accuse three 10K members of abusing their powers. And no, I was not one of those who voted for deleting, even if I do consider the question to be poor and worthy of deletion.

    • CommentAuthorquid
    • CommentTimeNov 5th 2012

    @Bill Johnson:

    Why don't you reveal who you are?

    We discussed this already n+1 times. The short answer is because I consider it most of the time, and in particular in such case, as irrelevant who I or anyone else here "is." MO is MO, and beyond contribution to the site I would consider it as better if people would not think so much who somebody "is" or more particularly who they themselves "are"; in particular, when it is about general procedural questions.

    IMO it is completely inappropriate for an anonymous poster to accuse three 10K members of abusing their powers.

    First, it could (when I wrote it) also have been the OP. And I would consider this too as an abuse of their deletion powers, though slightly less so.

    Second, I did not "accuse" anybody of anything. I said: "I consider this basically as an abuse of deleting-powers." That is I stated my opinion on this matter, and with the "basically" the possibility that it was an oversight was acknowledged. And, if it was not an oversight then in my opinion it is an abuse of deletion-powers to delete a question that could not so unlikely have been reopened. This is, I think by general agreement, not how the site is supposed to work (and something like a year ago there was a discussion on this). And I assume a 10k user will know this. So if they knowingly did this, then they used their powers in a way that is not in line with the community standards. So IMO this is an abuse of the powers given to them by the community in the first place.

    Third, it is slightly ironic to bring up anonymity specifically related to deletion as in almost all case it happens in such a way that there is no visibility/accounatability of which user did what beyond a small group.

    • CommentAuthorRyan Budney
    • CommentTimeNov 5th 2012 edited

    It seemed pretty uncontroversial to me to delete that thread. I was one of the deleters, BTW. There are very few community members that participate in this aspect of the forum. All 10k users can get the delete log on the tools menu.

    My reasoning: By a significant modification the question had been in effect turned into Gil Kalai's question rather than the OP's so it's not clear to me that anyone is really invested in the thread. I don't see a point in keeping such generalized questions about, where nobody actually cares about an answer. I mean, the question seemed to be persisting on some kind of abstract idea of the possible utility of it, rather than any actual interest or merits of the question. Rather than talking about whether or not it should be deleted, somebody who cares should craft a good question instead, and start a thread of their own.


    I wrote:

    I don't see the point of deleting it.

    Ryan wrote:

    I don't see a point in keeping such generalized questions about.

    So apparently the difference between our opinions, Ryan, is that for me the default position is not to delete. Thus, in my view, one needs a positive reason for deleting rather than closing. I regard deletion as reserved for spam, obvious homework, and a few other special cases.

    (For what it's worth, I did think the question deserved to be closed.)


    Tom: to me that's just a rhetorical flourish. :) To put my rationality into a "positive" framework, I voted to delete because I thought it was a classic derailed thread. Sure it wasn't spam, but there appeared to be an in-principle reason for nobody to be invested in the evolution of the thread. The OP vanished and the remaining people who were interested in the thread seemed to be for rather secondary reasons, moreover it wasn't clear if their interest was close to the OP's.

    • CommentAuthorgilkalai
    • CommentTimeNov 5th 2012
    I agree with Tom that deleting a question should be reserved for spam, obvious homework, and few other special cases. Some of the reasons listed by Ryan may be reasonable for closing but seem unreasonable for deleting.
    I dont see, Ryan, how changing the question in effect to my question means that nobody is really interested in this. Isn't it reasonable to assume that I am interested?
    (I also dont see the big difference between editing an existing question aiming to improve it or asking a new question.)

    I hadn't previously voted to undelete, because I wanted to think about this a bit more. But I have just done so, which means it's no longer deleted.

    For me, the decisive reason not to delete is that some high-reputation users want it open. There are currently three votes to reopen, which may or may not include Gil. Personally, I don't want it open, at least in its current form. But I think it's wrong to delete it, as a matter of respect for other people's opinions — even if I don't happen to share them.

    • CommentAuthorRyan Budney
    • CommentTimeNov 5th 2012 edited

    I've never really liked this motivation -- we keep weak questions open if it pleases the nobility. I won't touch that question again, no worries.

    Gil: I think it's somewhat disrespectful to the OP to modify their question without their feedback. We all have different boundaries though, so I won't look at this question or thread again.

    • CommentAuthorgilkalai
    • CommentTimeNov 5th 2012
    Hi Ryan, I was not sure myself if the new version is suitable enough,and what was missing for me in the discussion is some remark from a user in this area, regarding the mathematics of hurricanes, and even more so some hint that a capable user may supply an answer. I feel that the question to start with was not as unreasonable as Bill's hypothetical question regarding algebraic geometry and the end of the world. Is the term nobility refers to me? I takeit as a compliment but I still wonder what you have in mind.
    • CommentAuthorquid
    • CommentTimeNov 6th 2012

    Since some might not follow this question itself anymore, I copy over a comment (made 10h ago, but after, perhaps because of Ryan Budney's last comments) by OP:

    This was an attempt to have a topical question. Thankyou to Gil Kalai for editing it to be more suitable for MO. Thankyou to the commenters here and on meta - if the question is reopened then perhaps those comments could be collated into an answer.

    I am far from in this field, but I did some searches due to this discussion, and In principle one can definitely say something on modelling hurricanes from a math point of view; there are recent papers on modelling hurricane movement in math journals.


    Gosh, Gil, I was hoping you would make it into a question that was acceptable for MO.

    • CommentAuthorgilkalai
    • CommentTimeNov 7th 2012
    Dear Bill,
    ok, let me try

    I would like to know whether recent advances in algebraic geomtry can help us to predict when the universe will end.

    More generally, what is the mathematics (algebraic geometry? mathematical actuary?) relevant to dating the earth, our solar system, and the entire universe and predicting their life expectancy? What are the obstacles, for making these estimates in terms of mathematical modeling, chaotic behavior of such models, the ability to collect data, and the ability to solve and simulate the models, for better predictions? Are there bounds, in principle, for our ability to date the universe and to know when it is going to end?

    Practically speaking, regarding dating the universe, where would you take the universe for first date? Who is suppose to pick the bill?

    Thanks, GiI. I am impressed by your formulation.

    Perhaps I should explain my motivation for the question. Some people worry about dying; I worry about the universe dying. It would be comforting to know with overwhelming probability that this event is a long way off.

    • CommentAuthorfedja
    • CommentTimeNov 10th 2012
    Freeman Dyson argued that endless expansion and cooling down won't be a problem and the civilization of complexity comparable to the current one will be possible to maintain indefinitely in such scenario (not in the form of thinking blobs of flesh, of course, but those are minor technicalities). The big crunch is the thing to really fear. So, we should concentrate on figuring out which way it is going to be to start with.