Talk:Gravity well

3D? In the terms of Physics everything in our universe experiances time
3D? In the terms of Physics everything in our universe experiances time, and time being the fourth dimension means that everything in the universe is fourth dimensional. So, shouldn't the article say 4 dimensional? --Science Lord 13:40, 23 March 2006 (UTC)

Well, in Newtonian mechanics, and for most purposes where the concept of a gravity well is relevant, it's perfectly fine to ignore the relativistic effects, and then calling time a dimension or not is pure semantics. Adding a new section to the article on relativistic implications might be reasonable, but the intro should avoid the subject for clarity purposes. Evand 14:01, 23 March 2006 (UTC)

Poor style and content
This article is very poorly written with regards to scientific and mathematic exactness: "an extrusion of an otherwise 2-dimensional sheet", "time slows down to the point where it is not noticeably moving" are not phrases that belong in an encyclopedia without qualification (and even as an analogy these phrases are more misleading than helpful). The entire last paragraph sounds like it's lifted from a cheap SF novel.

I would urge a complete rewrite, or rather a deletion and redirection of the term to some existing article (e.g. Gravity). Thomas 19:51, 6 July 2007 (UTC)

external/internal gravitational potential
well, at the 3d-center of any spherical mass with radius R, gravity is zero, everyone knows.

and it sure stays differentiable around and at R.

so what does a gravity well cross-section really look like?

--Tobyvoss (talk) 17:23, 14 February 2008 (UTC)


 * I don't understand the question. The cross section shown in the article is differentiable everywhere, and the derivative (acceleration vector) at the center is zero. -- BenRG (talk) 00:28, 15 February 2008 (UTC)


 * ah thanks for the explanation with the acceleration vector, i wasn't thinking... --Tobyvoss (talk) 10:52, 15 February 2008 (UTC)

Interpreting diagram
Would I be correct in thinking that the diagram is a representation of gravity acting in two dimensions and would actually be more complicated if there were a 3rd dimension? Theshibboleth (talk) 11:47, 13 June 2008 (UTC)

Some questions
Pardon if I seem ignorant of some of the terms used here - it's been over twenty years since I was last in a Physics class.

I get that M in the function given is the mass of the object creating the gravitational well, and that x is the distance from that gravity source, but is G the Universal Gravitational Constant here, or merely indicative of the force of gravity acting at radius x?

{Geez. Some elementary algebra just solved part of this for me. If Φ is potential energy in Joules (kg*m2/s2, M is given in kilograms, and x is given in meters, solving for G yields units of m3/kg*s2, hence G is, indeed, the Universal Gravitational Constant. The product GM is explained well here:  }

I'm also making the presumption here that y = Φ(x), and that the upper "plane" of the well is an asymptotic approach to the x-axis? Is that correct?

My interest is somewhat specific: I would like to be able to plot gravitational wells for hypothetical stars of given masses. It would be convenient for my purposes for x to be expressed in AU, M in solar masses, and that leaves me in a quandary as to what units G would be in (so I get to do some more algebra, or unit analysis, to derive a conversion constant). A more complete identification of all the parameters in this equation, along with the usual units used, would go a great distance to making this a more understandable and useful article.

Note: I managed to accomplish some prelminary plots (first-order approximations which will be useful for my purposes). Horusfalcon (talk) 14:39, 7 January 2009 (UTC)

Linking to xkcd #681
Instead of reverting and undoing reverts and arguing in the edit comments, I suggest we talk about linking to the comic here on the talk page. Talk:Centrifugal_force_(rotating_reference_frame) More idiocy. It can't be stopped because there is such a cross-over between Wikipedia editors and xkcd fandom. —Preceding unsigned comment added by 90.220.88.147 (talk) 05:41, 15 January 2010 (UTC)
 * I personally don't think the page should be linked to, and if it should be, then it definitely doesn't belong in the introduction. There are much better graphical examples of gravity wells than some guy's drawing, and those should be linked to for reference (probably in their own section) before some comic. Gamer 2k4 (talk) 16:35, 30 December 2009 (UTC)
 * Personally I don't think the comic is worthy of a mention on the page, but I'd be happy enough with it relegated to the See Also section - lots of other pages on Wikipedia have links of somewhat questionable value in extra sections at the bottom. It certainly doesn't belong in the introduction - the comic is not an important feature of gravity wells! Nition1 (talk) 19:02, 30 December 2009 (UTC)
 * xkcd has already become something of a nemesis for Wikipedia, since ANYTHING referenced by that webcomic will justify, in the heads of the hopeless fanboys, a mention of xkcd on its respective Wikipedia article. This has been reason for arguments hundreds of times already, and there are even guidelines for people to decide whether a mention of xkcd is adequate or not. But something THIS egregious, I have never seen: mention xkcd on the INTRODUCTION of a science article? This is beyond preposterous. I think that reference should be removed immediately; and if the fanboys get so offended, a mention on the "See Also" is already more than sufficient, and bad enough.SirMustapha (talk) 19:38, 30 December 2009 (UTC)
 * You mean I can't link one of his stick figures at the top of the article on humans? But seriously yeah, glad it's gone now. 203.184.58.43 (talk) 00:16, 31 December 2009 (UTC)
 * If the XKCD fanboys need to have everything linked from Wikipedia then they should create an "XKCD References" article, throw all the links there, and hope it survives any eventual AfD processes. Polluting every single article referenced with a link to XKCD is definitely not the way to go. 83.41.148.148 (talk) 12:52, 3 January 2010 (UTC)
 * It seems like most of the objection is to inclusion of a reference to XKCD in the introduction (which seems a reasonable enough objection to me). I am left unsure of the right section to place a reference in. It doesn't seem like a "See Also" since it isn't a Wikipedia page. It doesn't seem like a "Reference" since we aren't referencing it. Perhaps it would fit in an "In Popular Culture" section. If in fact "There are much better graphical examples of gravity wells" then by all means let's include those as well. Jake (talk) 14:02, 18 October 2016 (UTC)

"Size" of an object's gravity well?
Is it possible to refer to the "size" of an object's gravity well, or some related terminology? By size I mean the radius from the center of the (primary) object such that a small (secondary) object will or will not fall to the primary object depending on whether the distance of the secondary from the primary is less than or greater than that critical radius. (Obviously this would be relative to surrounding environment, such as the proximity and mass of the primary's star.) Duoduoduo (talk) 16:05, 30 December 2012 (UTC)

It is not possible to refer to the "size" of the well in that sense. The "depth" of the well is 1/r where r is the distance from the center, so becomes ever smaller as r increases but never goes to zero. There is no distance such that an object initially at rest relative to the central object will not eventually fall into the secondary object if we're willing to wait long enough and nothing else interferes. — Preceding unsigned comment added by 216.240.30.23 (talk) 17:03, 14 March 2013 (UTC)

pun or ambiguity
"this does not depict the Sun's gravity well": Is this a pun or ambiguous? Is gravity an adjective and well a noun, i.e. it is referring to a gravity well, or is gravity a noun and well an adverb, i.e. the analogy does not depict well what it is supposed to depict? — Preceding unsigned comment added by 193.29.76.37 (talk) 18:52, 11 September 2015 (UTC)

Merge proposal
And by merge, I mean make this a redirect to General relativity. The point about space being curved is there in the lead paragraph. Everything else seems to be unsourced original research. UpdateNerd (talk) 06:35, 30 October 2019 (UTC) Support I think this is straightforward. –LaundryPizza03 ( d c̄ ) 00:59, 25 March 2020 (UTC)
 * Oppose Gravity wells and general relativity are two different topics. Gravity wells are a concept in Newtonian mechanics as well, where they are associated with gravitational potential wells, not curved spacetime. -- 02:43, 25 March 2020 (UTC)

An unexplained variable
In the first formula there is the absolute value of "x". What is x? 2607:FEA8:1320:531:6553:DF90:D49E:5DAC (talk) 13:18, 20 November 2019 (UTC)


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