![]() | This is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
Archive 1 |
Two things:
-- Taral
Currently Euler-Lagrange equations is an indirect self link, but Euler-Lagrange equation redirects to Lagrangian b4hand 20:08, 20 Jul 2004 (UTC)
At some point, Euler-Langrange equations might end up its own page, but until then, both plural and singular can point to action (physics), which is the simpler of the pair. -- Taral 02:52, 21 Jul 2004 (UTC)
division by yields the result as stated in the article :-) -- Unknown editor
No, it doesn't. That gives , and only if r is nonzero. -- Taral 08:23, 18 May 2005 (UTC)
Here's how you get it:
so
or for nonzero r
as stated in the article. -- Laura Scudder | Talk 22:03, 18 May 2005 (UTC)
Phys 01:22, 31 Jul 2004 (UTC)
Feel free to fix it.
Taral 21:21, 16 Aug 2004 (UTC)
Is it worth making an attempt to give a physical concept of the action: for example, thus:
Does this make any sense? Would anyone else like to correct or improve this please? -- The Anome 00:54, 13 February 2006 (UTC)
Some physics and math texts distinguish the "Hamiltonian Principal Function"
from the "action", which is the Legendre transform of R, exchanging t time for energy E:
This article does not distinguish R and S. Here, E is the energy, p the canonical conjugate momentum:
Its the first one, R, that is used in classical mechanics, to derive the Euler-Lagrange eqns of motion. Its the second that is used in quantum mechanics, the so-called action-angle coordinates, which is quantized in Bohr-Sommerfeld quantization as
with h Planck's constant of course. (See canonical one-form for a mathematical defn of the action). I'm not sure how to go about clarifying this in this article. linas 17:09, 11 June 2006 (UTC)
Hi, thanks for your nice derivation. I think our confusion may involve the following six quantities, all called "action" in physics
The quantities you cite above, R and S, are not clear to me -- are they functions or functionals? I'm guessing they're meant to be functions corresponding to S and W but, if so, they're not defined quite correctly.
I still don't see how J=S, since S is either a function or a functional and J is either a scalar or at best a list of the various J variables, e.g., . WillowW 12:16, 14 June 2006 (UTC)
Seven meanings, right? Then why does the section titled "Disambiguation" state there are eight meanings, whilst enumerating only these seven? - Yoyo 124.191.50.199 08:50, 10 October 2007 (UTC)
The polar coordinate example is ok ... but can anyone demonstrate how to use this stuff to show that objects freely falling in a uniform gravitational field follow parabolic paths? —The preceding unsigned comment was added by Paul Murray ( talk • contribs).
Can any one simplify the intro for a dummy like me to understand? —The preceding unsigned comment was added by Tugjob ( talk • contribs) 23:50, 22 May 2007 (UTC).
someone really needs to fix this article. Not me, an experienced professor who knows what they're doing. Tacobake 15:05, 13 July 2007 (UTC)Tacobake
At the time of this comment, the intro is really very bad:
... and so on. I think the problem is that the intro has been (well-meaningly) simplified to the point of complete uselessness! It needs a complete rewrite. Ideally this should be by someone who:
I am (sadly) not such a person. However, I believe that I understand enough to improve the current version, so I will have a try! For future editors aiming to improve my version (please, please do!), do try not to "dumb it down" to the point of meaninglessness, or elaborate it to the point of incomprehensibility to anyone without an advanced physics degree. FredV ( talk) 14:42, 9 February 2009 (UTC)
I have just reverted a "correction" to the new intro. The principal reason for this prompt revert is that the "correction" applies only to the quantum mechanical interpretation of action. Since the rest of the article is devoted almost entirely to the action in classical mechanics, this was likely to be confusing, especially to the les well-informed reader (who should, after all, be the primary target audience for the article intro). It is notable that the term "wave function" that was introduced in the proposed "correction" is not mentioned anywhere else in the article - which would surely confuse the keen teenage would-be physicist at whom I have aimed this intro.
I know that there are people who believe that classical mechanics died with the discovery of quantum mechanics — believe me, it did not! For any macroscopic system under normal thermodynamic conditions (that is, wherever the Ehrenfest theorem applies), classical mechanics is the only practical tool for analysis. I would guess that for every physicist applying quantum analysis to a problem, there are at least a hundred engineers applying classical mechanics! ... and of course, that means that there are still loads of people being taught classical mechanics, who may seek help and inspiration from Wikipedia. Many of these may never study quantum mechanics. It is also the case that almost everyone who studies mechanics will encounter the classical action before they are introduced to its quantum interpretations, so the classical action should at least appear first in the article.
With regard to my proposed intro, there are some "deficiencies" of which I am well aware:
I hope future editors will think carefully about my intentions before "correcting" these "deficiencies". FredV ( talk) 10:45, 12 February 2009 (UTC)
The major section (presently numbered 3) entitled "Examples of systems and their 'action'" contains just the following:
I suspect that the first is just a pair of placeholder notes for examples some author intended to write, whilst the second should be an independent major section.
Whatever the cause, the effect is confusing. Would someone please:
Thanks! - Yoyo 124.191.50.199 09:03, 10 October 2007 (UTC)
i noticed that the Lagrangian in the action integral doesn't contain time, and this is an error, L = L(q,q',t). I don't know how to edit math formulas, so i'm just throwing it out there. —Preceding unsigned comment added by 99.154.6.85 ( talk) 22:58, 16 February 2008 (UTC)
The following sentence
seems to connect the concept to Newton's laws of motion:
If my reading is accurate, making that connection clearer and earlier might help the reader grasp the concept by providing a familiar foundation before delving into the phase of the wave function, the Lagrangian function, etc.
Might Newton's third law be interpreted as "conservation of action"? - Ac44ck ( talk) 17:17, 20 March 2009 (UTC)
Planck's constant is given by
h = E / v (energy / frequency) joules / hertz or joules per cycle per second
The 'reduced planck's constant' is
h / 2 pi (energy / angular frequency) joules per radian per second
Dimensional analysis gives them both the dimensions of energy x time i.e. ML2T-1
The units of both of the Planck's constants are conventionally often referred to as joule seconds, unfortunately omitting to mention cycles or radians because they are dimensionless. Surely this is technically WRONG? We do not refer to 100MHz as 100M s-1 !
Unfortunately this error was compounded by giving the units of Planck's constant(s) the nick-name 'action' in quantum-mechanics.
I submit that the concept of 'joules per Hz' is reasonably easily comprehended, 'joules per cycle per second' and 'joules per radian per second' would be even clearer, but calling both of these 'joule seconds' is incorrect (being incomplete) and naming them 'action' is confusing nonsense!
Any comments? GilesW ( talk) 13:45, 30 April 2009 (UTC)
I think it has to be either defined or deleted. Bakken ( talk) 00:32, 12 December 2009 (UTC)
Reduced action redirects here, but the term is never defined. -Craig Pemberton 08:30, 30 December 2009 (UTC)
I read the introductory paragraph several times but wasn't able to understand anything about the subject. Could someone re-write it? Whatever may have been the purpose of the author of the current text, I ask that the goal be instead to introduce the subject simply and clearly to the intererested reader. Thanks in advance! Mark.camp ( talk) 03:42, 7 January 2012 (UTC)
Greetings! What I , as a Physics Student, feel about the introduction is that- it is clear, concise and up to the mark. The introduction puts forth a clear idea of what "Action" is. Nevertheless, I agree with Mark's view that it may not be easy for a beginner to understand the introduction properly as there is required some maturity to grasp the concept fully. To address this issue of not-very-clear introduction, I suggest we create one more page titled "An introduction to Action in Physics", similar to what is been done for Angular Momentum. It also makes sense in doing this since Action is as important a concept in Physics as is Angular Momentum(in fact they have the same SI units , showing that they are derived from same "basic" physical quantities). When looking at the need to merge the page of "Action" with Hamilton's Principle, I feel that it won't be a good idea because the page Action basically talks about the concept of Action in Physics and Mathematics whereas the page Hamilton's Principle, as is clear from the title, is intended to present Hamilton's Principle, which has to do with action as a property of motion. With best regards! — Preceding unsigned comment added by Shivsagardharam ( talk • contribs) 10:17, 9 January 2012 (UTC)
It still needs re-writing, how the hell is anyone supposed to get anything from this??
This is just my suggestion. If no one else does I'll try soon, busy right now...
-- F=q( E+v×B) ⇄ ∑ici 02:34, 10 March 2012 (UTC)
I see lots of comments arguing about whether the content of this page is confusing. Well I just wanted to say that I understand this shit and I did not understand it before. It's def one of the best-written articles I've ever read: give yourselves a break. -Keith (Hypergeek14) Talk 10:31, 27 June 2012 (UTC)
The following edit is being made by an anonymous IP without any explanation: [1]
It has been reverted at least three time, twice by me and once by Hroðulf. I'm not following why these edits are being made, but if the IP wants to add information to the article, then perhaps that is a good way to proceed. Isambard Kingdom ( talk) 17:08, 1 March 2015 (UTC)
I agree with this reinstatement by JRSpriggs, and do not agree with
M ∧Ŝ c2ħε Иτlk 17:17, 24 March 2016 (UTC)
Inclusion has many more requirements than just "useful information".
Removals of dubious uncited passages are subject to
WP:burden before replacement.
Hello again Maschen and Hello Spriggs,
There are many more requirements for inclusion than just "it's useful". The material was removed for being largely incorrect and uncited. In addition,
Torque#Units warns (with a citation!) against giving Torque as Joules (and by extension giving Angular Momentum as Joule-secs).
Like I said in the my last edit summary, if it's rewritten so it no longer implies that old fallacy, and *cited*, it can certainly be added back. But, this is not a vote.
WP:burden is clear. If you want to replace material removed as dubious and uncited, you must find a reliable ref for it first. So, go do that. Please. Really. It could be interesting! :-) If the material is so compelling and so useful, and if it's notable-enough and written so it's correct, then you should be able to easily find a reliable(!) ref for it. But, you're obliged to find the reliable ref first.
96.230.106.141 (
talk) 08:29, 26 March 2016 (UTC)
If you take another look at
WP:burden and other written policies, you'll find that dubious uncited content is absolutely removable. Often, to be nice and to maintain stability, uncited content that isn't dubious is sometimes left for a while with a "citation needed" tag with the idea that someday someone would get around to adding one. But, it's not at all traditional to just tag dubious content and leave it at that, especially for content as dubious as our present subject.
Regarding your "anyone who's stupid enough" commentary. What can I say about that? If you see the world and Wikipedia in those kinds of crass terms, maybe you shouldn't be doing this. Writing for lay-readers is what's being done here. Suggesting they're stupid because they don't understand a piece of writing is the wrong approach. It's our duty to write so it's understood, not the readers duty to understand what we write.
Regarding your "insinuating us of screwing up" paragraph. Well, again, I don't really know how to approach that. You must be very inexperienced in Wikipedia if you think one editor's removal of dubious content carries with it an implication that someone "screwed up". Telling people what can and cannot be in the articles is just the normal back-and-forth between good faith editors going about the business of editing WP. It seems you're very easily "annoyed" by that kind of normal good-faith exchange and numerous other things that are par for the course. I wish I could help give you peace in that regard, but you'll have to work on that personal issue yourself. :-)
Regarding "Random IP" comment. I understand your feelings believe it or not, lots of edits made at once (by anyone) are difficult to review and often a reversion is the right answer for a particular situation. But, you should review your attitude about "owning", you should know (by now) that IPs are full members with every status of logged in users and that no editor and no class of editors owns a WP page. Be careful to avoid automatically stereotyping. Give a little bit of review of the IP's (actually anyone's) editing history before jumping to conclusions about them. As they say, assume good faith. Read edit summaries carefully, judge edits by their content, not by the "color of the editor's skin".
96.230.106.141 (
talk) 10:00, 26 March 2016 (UTC)
Torque#Units cites BIPM at this link:
http://www.bipm.org/en/publications/si-brochure/section2-2-2.html
That page says:
The main point for us is to "facilitate the distinction between different quantities having the same dimension". We "facilitate the distinction" by not saying or implying that action is related to angular momentum. For this reason, I would even say that Angular Momentum is off-topic for the article -- unless it's to carefully say how it's not related to Action by mere virtue of their only-coincidental base units.
The passage says "...recall the process by which the quantity is defined..." which is apt here. Torque and Energy are defined by entirely different processes. Torque's process is a cross product of a force with a perpendicular length, while Energy's process is an integration of a force over a parallel length. To say that Torque is in Joules (or that Angular Momentum is in Joule-seconds) fails to "facilitate the distinction" between different processes.
Note that "Joule per radian" is correct for Torque, while "Joule" (in addition to being misleading regarding it somehow being energy) is off by a factor of Pi (maybe). "Joule-second" for angular momentum (in addition to it still being misleading which is the heart of our debate) might also be off by a factor of Pi, but I'd have to do some thinking on that. Hmmm...
96.230.106.141 ( talk) 10:55, 26 March 2016 (UTC)
The present article doesn't provide sufficient clear context to make out the following concepts: classical action, quantum action, bare action. Would like to see article make these clear. 75.139.254.117 ( talk) 01:24, 14 December 2016 (UTC)
Action is represented in SI units of Joule-seconds (kg m2 / s). Is there a specific separate name for this unit? — Loadmaster ( talk) 14:56, 11 May 2018 (UTC)
So is a path function and is the point where the path has arrived at time . Then the action is dependent on the path and not on the point , which of course requires on the left side. On the right hand side, uses a integration variable, so the result is independent of (wehereas the on the left suggests dependency). Please use a bit more precision in all of this... -- 217.95.166.1 ( talk · contribs · 217.95.166.1 WHOIS) 16:32, 27 October 2018 (UTC)
An editor has asked for a discussion to address the redirect Orders of magnitude (action). Please participate in the redirect discussion if you wish to do so. Utopes ( talk / cont) 20:32, 8 April 2020 (UTC)
I am a bit baffled by this:
Action is only of interest when the total energy of the system is conserved.
What is this supposed to mean? – Tea2min ( talk) 12:28, 18 May 2020 (UTC)
I have a visual demonstration.
I would like to add this demonstration to the article. I'm posting it first here to ask for opinion.
This explanation does not contain new information, it is purely explanatory.
That said: this demonstration is not a reimplementation of an existing demonstration. The approach is novel.
So it could be that some people will judge this demonstration to be original research.
Please let me know what you think.
The picture is an animated GIF, 7 different frames, 3 seconds per frame.
The demonstration starts with a variational approach. The true trajectory is identified among the trial trajectories by applying the work-energy theorem. At the very last step the demonstration proceeds to the Action.
The black curve represents a range of trial trajectories.
In the upper-right quadrant and lower-left quadrant:
Red curve: kinetic energy
Green curve: minus potential energy
There is continuous exchange of kinetic and potential energy; the true trajectory has the property that during the entire time the rate-of-change of kinetic energy and the rate-of-change of potential energy match each other.
When the trial trajectory hits the true trajectory the red graph and the green graph are parallel everywhere.
About the integrals in the lower-right quadrant: The value of the integral of a curve is proportional to the slope of that curve. The visual demonstration shows that the integrals allow a comparison of how the slopes of the energy graphs are responding to variation of the trial trajectory.
In this particular case (uniform acceleration) the response of the green graph to the variation is linear. The response of the red graph to variation is quadratic (since kinetic energy is proportional to velocity squared).
The visual demonstration shows: at the point in variation space where the energy graphs are parallel the two integrals have the same slope - with opposite sign. Hence: when the energy graphs are parallel the sum of the two integrals is at an extremum.
General remarks:
This demonstration is a two-stage process.
As I said earlier, the purpose of this entry on the Talk page is a request for opinion: would you be against or in favor of adding this demonstration to the article?
Cleonis |
Talk 20:02, 16 August 2020 (UTC)
I like the idea, and no, this is not original research. What kind of system are you describing, though? And would this simulation be better suited for the article on Lagrangian mechanics? StrokeOfMidnight ( talk) 18:33, 20 April 2021 (UTC)
![]() | This is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
Archive 1 |
Two things:
-- Taral
Currently Euler-Lagrange equations is an indirect self link, but Euler-Lagrange equation redirects to Lagrangian b4hand 20:08, 20 Jul 2004 (UTC)
At some point, Euler-Langrange equations might end up its own page, but until then, both plural and singular can point to action (physics), which is the simpler of the pair. -- Taral 02:52, 21 Jul 2004 (UTC)
division by yields the result as stated in the article :-) -- Unknown editor
No, it doesn't. That gives , and only if r is nonzero. -- Taral 08:23, 18 May 2005 (UTC)
Here's how you get it:
so
or for nonzero r
as stated in the article. -- Laura Scudder | Talk 22:03, 18 May 2005 (UTC)
Phys 01:22, 31 Jul 2004 (UTC)
Feel free to fix it.
Taral 21:21, 16 Aug 2004 (UTC)
Is it worth making an attempt to give a physical concept of the action: for example, thus:
Does this make any sense? Would anyone else like to correct or improve this please? -- The Anome 00:54, 13 February 2006 (UTC)
Some physics and math texts distinguish the "Hamiltonian Principal Function"
from the "action", which is the Legendre transform of R, exchanging t time for energy E:
This article does not distinguish R and S. Here, E is the energy, p the canonical conjugate momentum:
Its the first one, R, that is used in classical mechanics, to derive the Euler-Lagrange eqns of motion. Its the second that is used in quantum mechanics, the so-called action-angle coordinates, which is quantized in Bohr-Sommerfeld quantization as
with h Planck's constant of course. (See canonical one-form for a mathematical defn of the action). I'm not sure how to go about clarifying this in this article. linas 17:09, 11 June 2006 (UTC)
Hi, thanks for your nice derivation. I think our confusion may involve the following six quantities, all called "action" in physics
The quantities you cite above, R and S, are not clear to me -- are they functions or functionals? I'm guessing they're meant to be functions corresponding to S and W but, if so, they're not defined quite correctly.
I still don't see how J=S, since S is either a function or a functional and J is either a scalar or at best a list of the various J variables, e.g., . WillowW 12:16, 14 June 2006 (UTC)
Seven meanings, right? Then why does the section titled "Disambiguation" state there are eight meanings, whilst enumerating only these seven? - Yoyo 124.191.50.199 08:50, 10 October 2007 (UTC)
The polar coordinate example is ok ... but can anyone demonstrate how to use this stuff to show that objects freely falling in a uniform gravitational field follow parabolic paths? —The preceding unsigned comment was added by Paul Murray ( talk • contribs).
Can any one simplify the intro for a dummy like me to understand? —The preceding unsigned comment was added by Tugjob ( talk • contribs) 23:50, 22 May 2007 (UTC).
someone really needs to fix this article. Not me, an experienced professor who knows what they're doing. Tacobake 15:05, 13 July 2007 (UTC)Tacobake
At the time of this comment, the intro is really very bad:
... and so on. I think the problem is that the intro has been (well-meaningly) simplified to the point of complete uselessness! It needs a complete rewrite. Ideally this should be by someone who:
I am (sadly) not such a person. However, I believe that I understand enough to improve the current version, so I will have a try! For future editors aiming to improve my version (please, please do!), do try not to "dumb it down" to the point of meaninglessness, or elaborate it to the point of incomprehensibility to anyone without an advanced physics degree. FredV ( talk) 14:42, 9 February 2009 (UTC)
I have just reverted a "correction" to the new intro. The principal reason for this prompt revert is that the "correction" applies only to the quantum mechanical interpretation of action. Since the rest of the article is devoted almost entirely to the action in classical mechanics, this was likely to be confusing, especially to the les well-informed reader (who should, after all, be the primary target audience for the article intro). It is notable that the term "wave function" that was introduced in the proposed "correction" is not mentioned anywhere else in the article - which would surely confuse the keen teenage would-be physicist at whom I have aimed this intro.
I know that there are people who believe that classical mechanics died with the discovery of quantum mechanics — believe me, it did not! For any macroscopic system under normal thermodynamic conditions (that is, wherever the Ehrenfest theorem applies), classical mechanics is the only practical tool for analysis. I would guess that for every physicist applying quantum analysis to a problem, there are at least a hundred engineers applying classical mechanics! ... and of course, that means that there are still loads of people being taught classical mechanics, who may seek help and inspiration from Wikipedia. Many of these may never study quantum mechanics. It is also the case that almost everyone who studies mechanics will encounter the classical action before they are introduced to its quantum interpretations, so the classical action should at least appear first in the article.
With regard to my proposed intro, there are some "deficiencies" of which I am well aware:
I hope future editors will think carefully about my intentions before "correcting" these "deficiencies". FredV ( talk) 10:45, 12 February 2009 (UTC)
The major section (presently numbered 3) entitled "Examples of systems and their 'action'" contains just the following:
I suspect that the first is just a pair of placeholder notes for examples some author intended to write, whilst the second should be an independent major section.
Whatever the cause, the effect is confusing. Would someone please:
Thanks! - Yoyo 124.191.50.199 09:03, 10 October 2007 (UTC)
i noticed that the Lagrangian in the action integral doesn't contain time, and this is an error, L = L(q,q',t). I don't know how to edit math formulas, so i'm just throwing it out there. —Preceding unsigned comment added by 99.154.6.85 ( talk) 22:58, 16 February 2008 (UTC)
The following sentence
seems to connect the concept to Newton's laws of motion:
If my reading is accurate, making that connection clearer and earlier might help the reader grasp the concept by providing a familiar foundation before delving into the phase of the wave function, the Lagrangian function, etc.
Might Newton's third law be interpreted as "conservation of action"? - Ac44ck ( talk) 17:17, 20 March 2009 (UTC)
Planck's constant is given by
h = E / v (energy / frequency) joules / hertz or joules per cycle per second
The 'reduced planck's constant' is
h / 2 pi (energy / angular frequency) joules per radian per second
Dimensional analysis gives them both the dimensions of energy x time i.e. ML2T-1
The units of both of the Planck's constants are conventionally often referred to as joule seconds, unfortunately omitting to mention cycles or radians because they are dimensionless. Surely this is technically WRONG? We do not refer to 100MHz as 100M s-1 !
Unfortunately this error was compounded by giving the units of Planck's constant(s) the nick-name 'action' in quantum-mechanics.
I submit that the concept of 'joules per Hz' is reasonably easily comprehended, 'joules per cycle per second' and 'joules per radian per second' would be even clearer, but calling both of these 'joule seconds' is incorrect (being incomplete) and naming them 'action' is confusing nonsense!
Any comments? GilesW ( talk) 13:45, 30 April 2009 (UTC)
I think it has to be either defined or deleted. Bakken ( talk) 00:32, 12 December 2009 (UTC)
Reduced action redirects here, but the term is never defined. -Craig Pemberton 08:30, 30 December 2009 (UTC)
I read the introductory paragraph several times but wasn't able to understand anything about the subject. Could someone re-write it? Whatever may have been the purpose of the author of the current text, I ask that the goal be instead to introduce the subject simply and clearly to the intererested reader. Thanks in advance! Mark.camp ( talk) 03:42, 7 January 2012 (UTC)
Greetings! What I , as a Physics Student, feel about the introduction is that- it is clear, concise and up to the mark. The introduction puts forth a clear idea of what "Action" is. Nevertheless, I agree with Mark's view that it may not be easy for a beginner to understand the introduction properly as there is required some maturity to grasp the concept fully. To address this issue of not-very-clear introduction, I suggest we create one more page titled "An introduction to Action in Physics", similar to what is been done for Angular Momentum. It also makes sense in doing this since Action is as important a concept in Physics as is Angular Momentum(in fact they have the same SI units , showing that they are derived from same "basic" physical quantities). When looking at the need to merge the page of "Action" with Hamilton's Principle, I feel that it won't be a good idea because the page Action basically talks about the concept of Action in Physics and Mathematics whereas the page Hamilton's Principle, as is clear from the title, is intended to present Hamilton's Principle, which has to do with action as a property of motion. With best regards! — Preceding unsigned comment added by Shivsagardharam ( talk • contribs) 10:17, 9 January 2012 (UTC)
It still needs re-writing, how the hell is anyone supposed to get anything from this??
This is just my suggestion. If no one else does I'll try soon, busy right now...
-- F=q( E+v×B) ⇄ ∑ici 02:34, 10 March 2012 (UTC)
I see lots of comments arguing about whether the content of this page is confusing. Well I just wanted to say that I understand this shit and I did not understand it before. It's def one of the best-written articles I've ever read: give yourselves a break. -Keith (Hypergeek14) Talk 10:31, 27 June 2012 (UTC)
The following edit is being made by an anonymous IP without any explanation: [1]
It has been reverted at least three time, twice by me and once by Hroðulf. I'm not following why these edits are being made, but if the IP wants to add information to the article, then perhaps that is a good way to proceed. Isambard Kingdom ( talk) 17:08, 1 March 2015 (UTC)
I agree with this reinstatement by JRSpriggs, and do not agree with
M ∧Ŝ c2ħε Иτlk 17:17, 24 March 2016 (UTC)
Inclusion has many more requirements than just "useful information".
Removals of dubious uncited passages are subject to
WP:burden before replacement.
Hello again Maschen and Hello Spriggs,
There are many more requirements for inclusion than just "it's useful". The material was removed for being largely incorrect and uncited. In addition,
Torque#Units warns (with a citation!) against giving Torque as Joules (and by extension giving Angular Momentum as Joule-secs).
Like I said in the my last edit summary, if it's rewritten so it no longer implies that old fallacy, and *cited*, it can certainly be added back. But, this is not a vote.
WP:burden is clear. If you want to replace material removed as dubious and uncited, you must find a reliable ref for it first. So, go do that. Please. Really. It could be interesting! :-) If the material is so compelling and so useful, and if it's notable-enough and written so it's correct, then you should be able to easily find a reliable(!) ref for it. But, you're obliged to find the reliable ref first.
96.230.106.141 (
talk) 08:29, 26 March 2016 (UTC)
If you take another look at
WP:burden and other written policies, you'll find that dubious uncited content is absolutely removable. Often, to be nice and to maintain stability, uncited content that isn't dubious is sometimes left for a while with a "citation needed" tag with the idea that someday someone would get around to adding one. But, it's not at all traditional to just tag dubious content and leave it at that, especially for content as dubious as our present subject.
Regarding your "anyone who's stupid enough" commentary. What can I say about that? If you see the world and Wikipedia in those kinds of crass terms, maybe you shouldn't be doing this. Writing for lay-readers is what's being done here. Suggesting they're stupid because they don't understand a piece of writing is the wrong approach. It's our duty to write so it's understood, not the readers duty to understand what we write.
Regarding your "insinuating us of screwing up" paragraph. Well, again, I don't really know how to approach that. You must be very inexperienced in Wikipedia if you think one editor's removal of dubious content carries with it an implication that someone "screwed up". Telling people what can and cannot be in the articles is just the normal back-and-forth between good faith editors going about the business of editing WP. It seems you're very easily "annoyed" by that kind of normal good-faith exchange and numerous other things that are par for the course. I wish I could help give you peace in that regard, but you'll have to work on that personal issue yourself. :-)
Regarding "Random IP" comment. I understand your feelings believe it or not, lots of edits made at once (by anyone) are difficult to review and often a reversion is the right answer for a particular situation. But, you should review your attitude about "owning", you should know (by now) that IPs are full members with every status of logged in users and that no editor and no class of editors owns a WP page. Be careful to avoid automatically stereotyping. Give a little bit of review of the IP's (actually anyone's) editing history before jumping to conclusions about them. As they say, assume good faith. Read edit summaries carefully, judge edits by their content, not by the "color of the editor's skin".
96.230.106.141 (
talk) 10:00, 26 March 2016 (UTC)
Torque#Units cites BIPM at this link:
http://www.bipm.org/en/publications/si-brochure/section2-2-2.html
That page says:
The main point for us is to "facilitate the distinction between different quantities having the same dimension". We "facilitate the distinction" by not saying or implying that action is related to angular momentum. For this reason, I would even say that Angular Momentum is off-topic for the article -- unless it's to carefully say how it's not related to Action by mere virtue of their only-coincidental base units.
The passage says "...recall the process by which the quantity is defined..." which is apt here. Torque and Energy are defined by entirely different processes. Torque's process is a cross product of a force with a perpendicular length, while Energy's process is an integration of a force over a parallel length. To say that Torque is in Joules (or that Angular Momentum is in Joule-seconds) fails to "facilitate the distinction" between different processes.
Note that "Joule per radian" is correct for Torque, while "Joule" (in addition to being misleading regarding it somehow being energy) is off by a factor of Pi (maybe). "Joule-second" for angular momentum (in addition to it still being misleading which is the heart of our debate) might also be off by a factor of Pi, but I'd have to do some thinking on that. Hmmm...
96.230.106.141 ( talk) 10:55, 26 March 2016 (UTC)
The present article doesn't provide sufficient clear context to make out the following concepts: classical action, quantum action, bare action. Would like to see article make these clear. 75.139.254.117 ( talk) 01:24, 14 December 2016 (UTC)
Action is represented in SI units of Joule-seconds (kg m2 / s). Is there a specific separate name for this unit? — Loadmaster ( talk) 14:56, 11 May 2018 (UTC)
So is a path function and is the point where the path has arrived at time . Then the action is dependent on the path and not on the point , which of course requires on the left side. On the right hand side, uses a integration variable, so the result is independent of (wehereas the on the left suggests dependency). Please use a bit more precision in all of this... -- 217.95.166.1 ( talk · contribs · 217.95.166.1 WHOIS) 16:32, 27 October 2018 (UTC)
An editor has asked for a discussion to address the redirect Orders of magnitude (action). Please participate in the redirect discussion if you wish to do so. Utopes ( talk / cont) 20:32, 8 April 2020 (UTC)
I am a bit baffled by this:
Action is only of interest when the total energy of the system is conserved.
What is this supposed to mean? – Tea2min ( talk) 12:28, 18 May 2020 (UTC)
I have a visual demonstration.
I would like to add this demonstration to the article. I'm posting it first here to ask for opinion.
This explanation does not contain new information, it is purely explanatory.
That said: this demonstration is not a reimplementation of an existing demonstration. The approach is novel.
So it could be that some people will judge this demonstration to be original research.
Please let me know what you think.
The picture is an animated GIF, 7 different frames, 3 seconds per frame.
The demonstration starts with a variational approach. The true trajectory is identified among the trial trajectories by applying the work-energy theorem. At the very last step the demonstration proceeds to the Action.
The black curve represents a range of trial trajectories.
In the upper-right quadrant and lower-left quadrant:
Red curve: kinetic energy
Green curve: minus potential energy
There is continuous exchange of kinetic and potential energy; the true trajectory has the property that during the entire time the rate-of-change of kinetic energy and the rate-of-change of potential energy match each other.
When the trial trajectory hits the true trajectory the red graph and the green graph are parallel everywhere.
About the integrals in the lower-right quadrant: The value of the integral of a curve is proportional to the slope of that curve. The visual demonstration shows that the integrals allow a comparison of how the slopes of the energy graphs are responding to variation of the trial trajectory.
In this particular case (uniform acceleration) the response of the green graph to the variation is linear. The response of the red graph to variation is quadratic (since kinetic energy is proportional to velocity squared).
The visual demonstration shows: at the point in variation space where the energy graphs are parallel the two integrals have the same slope - with opposite sign. Hence: when the energy graphs are parallel the sum of the two integrals is at an extremum.
General remarks:
This demonstration is a two-stage process.
As I said earlier, the purpose of this entry on the Talk page is a request for opinion: would you be against or in favor of adding this demonstration to the article?
Cleonis |
Talk 20:02, 16 August 2020 (UTC)
I like the idea, and no, this is not original research. What kind of system are you describing, though? And would this simulation be better suited for the article on Lagrangian mechanics? StrokeOfMidnight ( talk) 18:33, 20 April 2021 (UTC)