Talk:Sticky bead argument

Needs clarification

The article should include an explanation of the difference between spacetime and gravity. In the rod&bead experiment it is unclear why the gravitational waves would affect just the beads along the rod and not the space housing the atoms of the rod itself (and therefore the rod) as well. Gravitational waves are disturbances in spacetime, why affect and move just the beads and not the space housing the atoms of the rod (and the space anywhere the rod may be attached for that matter)? Logic says the entire system would warp evenly with no movement of the beads at all. 86.93.208.34 (talk) 00:51, 12 May 2020 (UTC)

Description, and Feynman's Argument

The description of the genesis of the "sticky bead" argument suggests that Bondi plagiarized or otherwise appropriated without attribution an argument by Feynman. The meeting's published proceedings show that the "sticky bead" argument was first proposed by Bondi during the question session during Pirani's presentation [1]. (A dashpot is nothing more than a resistive device: e.g., sticky beads on a stick.) This took place at the very beginning of the conference. The proceedings further show that Feynman's suggestion followed it at the very end of the meeting, as a side remark during the closing discussion of the session on the necessity of quantizing gravitation. (In this connection it is worth noting that the conference took place over six days.) I suggest that - absent suitable references showing that Bondi plagiarized or otherwise appropriated without attribution an argument by Feynman - this section be rewritten to more accurately represent the genesis of the argument and eliminate the remarks disparaging Bondi. — Preceding unsigned comment added by 2601:8C3:857E:61DD:0:0:0:A6 (talk) 18:49, 29 August 2023 (UTC)

In this connection it may also worth noting that Feynman apparently mischaracterized gravitational waves as being longitudinal: i.e., the transcript in the conference proceedings “[a] particle situated initially near a long light rod, oriented parallel to the propagation direction, could be made to scrape against the rod by transverse-transverse wave amplitudes.” FinnLS (talk) 23:31, 17 May 2024 (UTC)

Einstein's double reversal

My initial version was based upon the somewhat confusing account in Kennefick's first cited paper. Shortly thereafter, I became aware of the very recent Physics Today paper, which I have used to revise my (oversimplified) account. BTW, I am trying to obtain permission to upload the photograph by Lotte Jacobi of a beaming Albert Einstein sitting with Leon Infeld, apparently taken about 1937, possibly in Einstein's summer home in Long Island.---CH (talk) 23:04, 6 November 2005 (UTC)

I have had no reponse re the photograph. ---CH 04:58, 25 March 2006 (UTC)

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Interesting article, a good read. There is a reference to the ``hole argument" at the end. Shouldn't this be linked up with the Wiki article on that? 129.130.96.68 22:30, 1 April 2007 (UTC)anonymous user

Description of the argument

Why do we have to read through more than 2/3 of this article before getting to the description of the argument? "Feynman's argument" should be the first subsection. 198.49.180.40 00:38, 6 April 2007 (UTC)

Yes, this article seems to be be "an overview of the history of arguments for and against gravitational waves." Not quite as catchy a title, but probably more accurate.  :) --Starwed 13:05, 3 September 2007 (UTC)

I just fixed it, somewhat, by copying and pasting the paragraph describing the thought experiment up to the top. The article's structure is still rather poor, though, since most of the content isn't actually about the subject. Perhaps the bulk of it should be moved to somewhere more general, perhaps gravitational wave? Bryan Derksen (talk) 22:38, 9 January 2008 (UTC)

Is more detail of the argument available somewhere? For example, why does the wave cause the bead to move without also moving the support of the rod? (Is the bead positioned asymmetrically along the rod?)Cesiumfrog (talk) 04:34, 6 January 2009 (UTC)

Rod is ultimately attached to massive object, like the earth. Bead is unnattached and is in a kind of freefall. Rod is stationary. Bead is movable. But how do we know that gravitational radiation makes the bead move? It could be some other cause, like thermal or mechanical movement. It is more sensible to look for an observable cause than a cause that has never been detected anywhere. Lestrade (talk) 22:22, 5 February 2009 (UTC)Lestrade

Is the rod rigid? There's no such thing as a rigid body in General Relativity. Miguel (talk) 13:31, 17 October 2011 (UTC)

Also, if gravity warps spacetime, why doesn’t the space containing the rod, and therefore the rod itself, warp? This is a logical question. 86.93.208.34 (talk) 00:34, 12 May 2020 (UTC)

"Hole" argument?

I don't understand what is meant by "the hole argument" at the end. —Długosz

Agreed, either it is a typo for "the whole argument" or it refers to something otherwise unmentioned in the article. --Starwed 13:04, 3 September 2007 (UTC)

Someone must have deleted my mention of Hole argument but this term is well known in the field and that is what I was referring to. The version I linked to was this version, but I never did write the article I had in mind. (Note that I would describe the key ideas involved in resolving the hole argument somewhat differently from the current version of the WP article.) ---CH (talk) 19:48, 7 July 2008 (UTC)

einsteins double reversal stuff

I am only posting here about such a minor edit cause i reverted my own edit twice. anyhow the sentence as it stands now is

Quite uncharacteristically, Einstein took this criticism very badly, angrily replying I see no reason to address the—in any case erroneous—opinion expressed by your referee and vowing never again to submit a paper to the Physical Review (he never did).

It originally had a comma right before "and vowing". This is a somewhat confusing comma insertion in the original form so it was rather tough to figure out what to do. I decided the most readable form of the two options is to reinsert the comma and change vowing to vowed. The problem is that i don't think that this conveys the intended meaning as well as the above form. In the above, IMO harder to understand sentence, "angrily replying" and "vowing" are how he reacted badly. Whereas in the more readable version with the comma, "angrily replying" is how he reacted badly and "vowing never again to submit a paper to the Physical Review" was a separate semantic action. Seems like being a stickler over grammar but it seems like an unwieldy sentence in either case. Anyway the sentence is syntactically correct in its current form but i was thinking maybe someone could come up with some other refactoring that might be better.--66.153.117.118 (talk) 21:59, 22 March 2008 (UTC)

As a writer, possible reactions include (i) writing a thoughtful essay on the role of the comma (ii) invoking Isaac Babel's joke that in the best writing, the story is carried by the punctuation (slay them with a semicolon!, he advised writers).

As a sometime Wikipedia critic (formerly from the inside, now from the outside), I'd be tempted to point out that this discussion illustrates a phenomenon noted by many observers: Wikipedians seem to wind up arguing on talk pages over minutae rather than writing new material (this has much to do with why I eventually quit volunteering my knowledge and writing skills ;-/ at WP). CH (talk) 20:01, 7 July 2008 (UTC)

BTW, regarding the citation tags, the user who added those evidently didn't bother to read the papers I cited by Kennefick, who cites papers held in various archives, e.g. the personal papers of H. P. Robertson. The story about Feynman registering anonymously is very well known, in part because RPF enjoyed telling it himself; IIRC he mentions this episode in several of his books. IIRC, Kennefick also mentions that Feynman really did insist on registering under a pseudonym to make a point, and the bemused organizers let him have his way.CH (talk) 20:05, 7 July 2008 (UTC)

Axis orthogonal to "the" symmetry axis of a bar ???

The article gives as an example of a system with a time-varying quadrupole moment a bar "rotating about an axis orthogonal to the symmetry axis of the bar".

To me a bar is a rectangular solid with three different edge-lengths. Such a shape has not one but three axes of symmetry -- each orthogonal to the other two. (The edge-lengths of a bar tend to be in roughly certain proportions, but this is not relevant here.)

So the phrase "the symmetry axis of the bar" is unclear, since "the" implies there is only one. I cannot fix this, since I don't know what is meant. But perhaps a knowledgeable person can express this clearly.Daqu (talk) 04:28, 1 March 2009 (UTC)

Einstein Rosen collapse

Einstein's position regarding gravitational waves is more subtle than people give him credit for. He still believed the waves would impart energy and momentum, he just believed that the nonlinearities would make this energy be carried in little points, like gravitons, and that the gravitons would add up to the total energy in the wave.

This is true to some extent, because gravitational waves can collapse to black holes. These black holes can then carry energy and momentum. But the gravitational waves themselves are locally stable, contrary to the Einstein Rosen paper. This was a bit of wishful thinking on Einstein's part.Likebox (talk) 15:42, 1 July 2009 (UTC)

Also, in point of fact, the first person to claim that gravitational waves were "ripples in coordinates" and carried no energy and momentum is Eddington. Einstein did not agree then, and never agreed later, with the point of view that quadropole waves would carry no energy. He just wanted the nonlinearities to explain quantum behavior, as I said before.Likebox (talk) 15:44, 1 July 2009 (UTC)

Possible "plagiarism"

The main page has a header "This article includes a list of references, but its sources remain unclear ..". In searching for a related term, I came across this book by Fredrick Kennard via Google: Thought Experiments. The majority of the article seems to have been copied verbatim from the book but I don't see any attribution, however, perhaps the book copied from Wikipedia. George Dishman (talk) 09:44, 10 May 2016 (UTC)

Feynman's "Mr Smith" Pseudonym

The text says: "The thought experiment was first described by Feynman (under the pseudonym "Mr. Smith") in 1957, at a conference at Chapel Hill, North Carolina,[3]"

I've read the source, there's no mention of that pseudonym anywhere. In fact there is a transcript in source [3] (pages 252-260ish) where Feynman mentions the experiment in conversation with others and there is a section at the end of the report giving the argument in detail. It's a fanciful story and it might be true but the source is not [3]. Mef51 (talk) 20:06, 27 October 2017 (UTC)

@Mef51: thanks for raising the argument, it's been a while that it has been in doubt, I just took the opportunity to remove it.--ReyHahn (talk) 19:57, 29 August 2023 (UTC)

I found a quote in this book [2].--ReyHahn (talk) 12:07, 16 December 2024 (UTC)