User talk:JFB80

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Discussion on the Mileva Maric Talk page

Dear JFB80: Thank you for expression of concern in your 16 September 2013 response to my reply to your comments. I am feeling a little better today (Tuesday) and will endeavour to give at least a partial response to your several points. In fact it may help me to focus on this topic, though I have to be careful not to put myself under pressure, which tends to produce a reaction. So my reply may be in separate contributions.

With appreciation, Allen Esterson Esterson (talk) 11:29, 17 September 2013 (UTC)

Dear Dr Esterson: Thank you for your note. I hope you will soon be well enough to resume discussion. I see you have considerable knowledge about this subject which I do not pretend to have although I feel I may have a somewhat new point of view. Regards JFB

Thanks for your good wishes. I've been feeling much better for about nine days now – maybe the anti-depressant has kicked in. I appreciate the politeness with which you have conducted our exchanges, and the searching nature of your contributions. The process of responding (and occasionally checking back on sources) has, I think, helped me to consolidate my improved mental/emotional state. I appreciate that these kinds of exchanges can be time-consuming, and fully understand if you decide to discontinue your responses. However, if you have a specific point or question you want to raise I will be happy to respond to it.Esterson (talk) 07:43, 25 September 2013 (UTC)

Thanks for your note. I'm glad these exchanges have helped you. JFB80 (talk) 19:56, 26 September 2013 (UTC)

April 2014

Hello, I'm DVdm. I noticed that you made a change to an article, History of special relativity, but you didn't provide a source. I’ve removed it for now, but if you’d like to include a citation to a reliable source and re-add it, please do so! If you think I made a mistake, or if you have any questions, you can leave me a message on my talk page. Thanks. DVdm (talk) 21:12, 16 April 2014 (UTC)

Archival undo

Hi JFB80, FYI please see [1]. Cheers - DVdm (talk) 06:32, 19 October 2015 (UTC)

January 2016

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• as the [[Dirac delta function]].<ref>'''Electromagnetic Theory''',vol.II, para.271, eqns 54,55)</ref> He invented his [[Operational calculus|operator]] method for solving [[linear]] [[

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September 2016

Please do not add or change content, as you did at Minkowski space, without citing a reliable source. Please review the guidelines at Wikipedia:Citing sources and take this opportunity to add references to the article. Thank you. - DVdm (talk) 17:21, 1 September 2016 (UTC)

Spacetime metric sign convention

I was just reading the discussion on the talk page of Minkowski space. For what it's worth, I agree with you that $c^{2}d\tau ^{2}=c^{2}dt^{2}-(dx^{2}+dy^{2}+dz^{2})$ makes more sense than the other convention. Dividing by $c^{2}dt^{2}$ results in $(d\tau /dt)^{2}=1/\gamma ^{2}=1-v^{2}/c^{2},$ which is correct. Dividing $c^{2}d\tau ^{2}=dx^{2}+dy^{2}+dz^{2}-c^{2}dt^{2}$ by $c^{2}dt^{2}$ results in $(d\tau /dt)^{2}=1/\gamma ^{2}=-(1-v^{2}/c^{2}),$ which is incorrect. Jrheller1 (talk) 04:16, 2 October 2016 (UTC)

Actually, the metric for the +++- sign convention is written $ds^{2}=-c^{2}d\tau ^{2}=dx^{2}+dy^{2}+dz^{2}-c^{2}dt^{2},$ so it does yield the correct value of $\gamma .$ But I definitely don't like the negative value for $ds^{2}.$ Jrheller1 (talk) 06:03, 2 October 2016 (UTC)

I moved your comment from my user page to my talk page. If you wish to reply to me, you can do so here (I am watching your talk page). Jrheller1 (talk) 18:26, 2 October 2016 (UTC)

I hope you didn't mind me quoting your comment on the Minkowski talk page. I am so glad you make your latest comment because anything I say now, however obvious, is immediately rejected. I am finding this behaviour quite upsetting. Previously I said the same as you do now only to have it dismissed as 'off-topic'. Here is my comment (in reply to Chetvorno who said a choice of sign convention has no physical implication.

JFB80: Isn't c²dt² - (dx²+dy²+dz²)>0 (time-like) the condition for velocity to be less than that of light? (Einstein's 2nd postulate). Positive (+---), negative (-+++) If you don't think this suggests a sign convention then whatever would? (talk) 19:47, 6 September 2016 (UTC)

The article continues to say a choice of sign convention has no physical implication. JFB80 (talk) 19:32, 2 October 2016 (UTC)

I agree with the other editors at the Minkowski space talk page that the sign convention has no physical implication. It can't possibly have any physical implication because the two equations $c^{2}d\tau ^{2}=c^{2}dt^{2}-(dx^{2}+dy^{2}+dz^{2})$ and $-c^{2}d\tau ^{2}=dx^{2}+dy^{2}+dz^{2}-c^{2}dt^{2}$ are exactly the same mathematically. I just think that the +++- sign convention is clumsy notation: it makes $s=ic\tau$ rather than $s=c\tau$. Jrheller1 (talk) 20:07, 2 October 2016 (UTC)

I look at it this way: $c^{2}d\tau ^{2}=c^{2}dt^{2}-(dx^{2}+dy^{2}+dz^{2})$ and $c^{2}ds^{2}=dx^{2}+dy^{2}+dz^{2}-c^{2}dt^{2}$ are the two possibilities where we shall be looking for a positive square root for both dτ and ds. This will happen for dτ if the velocity v is less than c (time-like displacement) and for ds if v is greater than c (space-like displacement). In standard Special Relativity only the first is permitted when we are considering the motion of material particles. JFB80 (talk) 11:54, 4 October 2016 (UTC)

In the +--- metric, $s=c\tau$ and both $s$ and proper time $\tau$ are real unless the speed of the "moving" reference frame is greater than the speed of light, which is not physically realistic. In the +++- metric, proper time $\tau$ is still real but $s=ic\tau$ is imaginary for physically realistic scenarios. It seems clumsy to me to use imaginary numbers when they are not necessary. Jrheller1 (talk) 22:02, 4 October 2016 (UTC)

I think it makes no sense to use imaginary quantities with norms. All we have to do is to say there are two norms, namely ${\sqrt {(}}c^{2}dt^{2}-dx^{2}-dy^{2}-dz^{2})$ and ${\sqrt {(}}dx^{2}+dy^{2}+dz^{2}-c^{2}dt^{2})$ . The first applies to time-like displacements and the second to space-like displacements. In relativity only the first has physical significance because the velocity must be less than that of light. Then we deduce, as you did, that the first is c dτ JFB80 (talk) 09:57, 8 October 2016 (UTC)

More generally we can do the same with finite displacements Δx, Δy, Δz, Δt or with coordinates x, y, z, t which are displacements from (0, 0, 0, 0). JFB80 (talk) 16:23, 8 October 2016 (UTC)

Hyperboloid model

You may be interested in

• Homersham Cox (mathematician)#Work on non-Euclidean geometry or
• Gustav von Escherich#Work on hyperbolic geometry,

as well as in the recent additions to

• History of Lorentz transformations

with a bunch of many other authors having historical variants of Lorentz transformations via Weierstrass coordinates, or via Cayley absolute, or via Cayley-Hermite transformation, or via Quaternions etc. --D.H (talk) 21:40, 22 March 2018 (UTC)

Dear JFB80, I moved our discussion to Talk:History of Lorentz transformations#History of hyperbolic model, Lorentz transformation, which I think is the better place. If you disagree, please feel free to revert my edit. --D.H (talk) 09:04, 27 March 2018 (UTC)

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Your edit at Wikipedia:Wikipedians

I've undone your edit at Wikipedia:Wikipedians. Have you any idea how that happened - were any tools or scripts involved? Because someone else accidentally posted an article over the page three weeks back. -- John of Reading (talk) 09:03, 10 May 2020 (UTC)

i didn't know about this. But I think it is not important. Thanks for the message. JFB

May 2020

Please refrain from making unconstructive edits to Wikipedia, as you did at Wikipedia:Wikipedians‎‎. Your edits appear to be disruptive and have been or will be reverted.

• If you are engaged in an article content dispute with another editor, please discuss the matter with the editor at their talk page, or the article's talk page, and seek consensus with them. Alternatively, you can read Wikipedia's dispute resolution page, and ask for independent help at one of the relevant noticeboards.
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Please ensure you are familiar with Wikipedia's policies and guidelines, and please do not continue to make edits that appear disruptive. Continued disruptive editing may result in loss of editing privileges. Thank you. SuperMarioMan (Talk) 22:32, 10 May 2020 (UTC)

@SuperMarioMan: I'm beginning to suspect that a software problem is involved. JFB80 overwrote the page twice, yes, but since 5 November, four other editors have made the same mistake. -- John of Reading (talk) 06:22, 11 May 2020 (UTC)

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Revert

Regarding this revert, see consensus in the discussion that I linked to in my edit summary. Marcocapelle (talk) 17:49, 10 December 2021 (UTC)

Galilean *invariance*

Hello JFB80, this is about your undoing of my 1072860212 revision to Inertia. Two points: a)I modified the page text by adding a link to the existing page Galilean invariance; b) in describing my edit I erroneously used the term "equivalence" instead of "invariance". Now, I would like to make sure that your undoing is related to point b) and to my use of the wrong term "equivalence"; in this case I could reply the page edit, using the correct term in comments. Should your message be related to point a) instead, could you please be more specific on your issue. Thank you Vbrm (talk) 19:30, 21 February 2022 (UTC)

Hello Vbrm, I have never seen the term Galilean invariance or equivalence used in the literature and think it is just a Wikipedia invention. In any case it needs a correct reference to the original source which does not seem to be there. The observation was apparently made before the appearance of Galileo's book but I don't know myself exactly when.JFB80 (talk) 11:03, 22 February 2022 (UTC)

Well three points:

1) Wikipedia has two full pages on this, Galilean invariance and Galilean equivalence, which redirects to Equivalence principle#Weak. They are quite detailed and have corresponding pages in some 40 languages. They seem well documented to me with their proper references (mainly Equivalence principle#Weak). Have you given a look at them ? If a page exists in Wikipedia shouldn't be possible to simply refer to it in another page, without the need to justify its existence ?

2) Nobody is claiming that Galileo himself wrote somewhere the definition of these term, but just that a phenomenon exists and that there is an agreement to refer to it with a term containing a reference to Galileo; same relation we have among Pythagoras and Pythagorean theorem. Do we agree on this ?

3) A Google search for these terms gives back many results, I'm listing here some of them which may be more meaningful: Scientific article, Lumenlearning.org, Britannica University College London , University of Virginia . Would you see them as correct references ?

Thank you Vbrm (talk) 13:01, 22 February 2022 (UTC)

Ok I agree the term is generally used. But there is still my other point that no-one has bothered to find out exactly where it occurred with Galileo. And may I mention a more important point that it was first accurately described by Newton who is normally only credited with absolute space but who gave the first clear statement of mechanical relativity. JFB80 (talk) 15:36, 22 February 2022 (UTC)

Thank you. On your other points: The Galilean invariance page refers to the ship thought experiment described in Galileo's Dialogue Concerning the Two Chief World Systems (day two), which is the first explicit statement of relativity of motion among inertial systems. As a reference seems quite accurate to me. As to the question on whether the name, Newton itself was clear of his debt against Galileo (and Huygens; see for example Stillman Drake, Galilei: Pioneer scientist, Univ of Toronto 1990, ch 15 - I read the italian translation); and Einstein in his "Relativity - popular exposition" speaks of "Galilei - Newton mechanics". So I do not think there can be in any way a Galileo - Newton opposition on this matter. Vbrm (talk) 20:59, 22 February 2022 (UTC)

Yes I know of the statement by Galileo you mention. There he talks of the behaviour of insects and fishes below deck. I thought though that somewhere earlier he had made a more dynamic statement saying that a cannon ball dropped from the top of the mast would fall to the foot (which must have been known to generations of sailors). As to Newton's knowledge of Galileo you only have to actually read Principia (few people do). Newton does something that Galileo did not and states the principle of relativity as it applies to uniform motion in mechanical systems (contrary to usual belief).JFB80 (talk) 07:39, 23 February 2022 (UTC)

Newton's version of the principle of relativity is his Corollary V to his Laws of Motion. It includes the remark "A clear proof of which we have from the experiment of a ship; where all motions happen after the same manner, whether the ship is at rest, or is carried uniformly forwards in a right line." (https://gravitee.tripod.com/axioms.htm).JFB80 (talk) 05:35, 24 February 2022 (UTC)

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