Talk:Cavendish experiment

message: This article is about the original Cavendish experiment not about modern experiments. Zeyn1 (talk) 18:34, 27 May 2022 (UTC)
thread_title:  Do not use any modern image on this page 

message: The period was given as "about 20 minutes". This was not correct. For the first 3 experiments the period was about 15 minutes. After the third experiment Cavendish put a stiffer wire and the period became about 7.5 minutes. I made the change accordingly. Zeyn1 (talk) 08:11, 2 June 2022 (UTC)
thread_title:  The period of the balance 

message: This experiment is always referred to as the 'Cavendish experiment' and never the 'torsion bar experiment'; see the external links in the article, and:
*Encyclopedia Brittanica online article 
*Harvard University Physics Dept. description
*S.F. State description
*U. of Saskatchewan undergrad lab experiment
I could only find one page where it was called something else: Michell-Cavendish Experiment. 
Also the current name is misleading; the apparatus used is called a 'torsion balance', whereas most people think of a 'torsion bar' as part of a car suspension.  How about renaming this well-written article 'Cavendish experiment'?  I've already added that name to the article. - Chetvorno 07:36, 1 April 2007 (UTC)
replies: text: Done. —Nightstallion (?) 20:16, 12 March 2006 (UTC)
thread_title:  Requested move: Torsion bar experiment → Cavendish experiment 

message: The do-it-yourself experiment at Fourmilab () can't possibly be correct. A calculation using F=MA and F=GmM/(r^2) shows that it would take hours for the torsion balance to rotate as far as the video shows. Furthermore, a version of the experiment  performed by Professor Norman Scheinberg (The City College of New York) uses much more massive weights (about 30 kg) and a much thinner wire (25 microns) made of tungsten - and the torsion balance only moved about 2.5 cm in twelve minutes. In the Fourmilab experiment, the movement due to gravity produced by the smaller weights and thicker, stiffer wire would be microscopic. (An earlier version of the article included a remark questioning Fourmilab's results, but it was removed.) If the video is not a hoax, the explanation for the rapid movement is almost certainly air currents created by the movement of his hands near the balance. The experiment by Professor Scheinberg is inside a box to prevent air currents from moving the balance, and Cavendish's original experiment was also protected from wind. - CronoDAS 03:46, 19 August 2006 (UTC)
replies: text: Although I haven't gone through the math, your criticisms of the 'Fourmilab' experiment sound valid.  So glad someone has the experience to catch errors like that.  I think I included the Fourmilab page as reference just because I was impressed that someone would try the Cavendish experiment in their basement with fishing line.  But I should have noticed he didn't calibrate the apparatus by calculating the period of oscillation.  I agree with removing the Fourmilab reference and replacing it with the Scheinberg experiment, a much better example of a homebrew Cavendish experiment.  - Chetvorno 08:20, 1 April 2007 (UTC)
thread_title: Fourmilab is bogus

message: Could an artist please add a picture to illustrate this experiment as it would be so much easier to understand then.82.25.173.16 18:39, 3 December 2006 (UTC)
replies: text: I added the original drawing from the experiment and removed the picture with dumbell type of torsion pendulum. That was confusing giving the impression that Cavendish used dumbells attached to the arm. In fact he had lead weights of 2 inches diameter suspended from each end of the arm. I will also add a detail showing the arm. Zeyn1 00:17, 20 August 2007 (UTC)
replies: text: Great addition. --Chetvorno 19:29, 22 August 2007 (UTC)
thread_title: Add a picture

message: What kind of image is the one of Cavendish performing the experiment, and where did it come from?  It looks for all the world like a manipulated photograph, but as far as I am aware photography didn't get started until the 1820s, 10 years after his death.  Is it just an extremely good rendering?  The image file itself doesn't seem to have any source information associated with it.
: I believe that image is an illustration and it is misleading. I added "artist's rendition" to the caption. Zeyn1 00:59, 2 July 2007 (UTC)
thread_title: Image of Cavendish

message: I have now reviewed this article under the six Good article criteria, and have commented in detail on each criterion below:
1 Well written FAIL
1.1 Prose
The article generally explains its scientific concepts well, and gives a good outline of the actual experiment. However, in places the prose could do with copyediting for grammar, flow and clarity. I have given some examples below, but the list is not exhaustive:
*"The Cavendish experiment, done in 1797 – 1798 by Henry Cavendish..."
:Suggestion: "The Cavendish experiment is the name given to a series of experiments performed by British scientist Henry Cavendish from 1797-1798..." (note date ranges are separated by an unspaced en dash)
*"However, these were derived by others from Cavendish's result, which was a value for the Earth's density."
:Suggestion: "Cavendish's goal was to calculate the density of the Earth; his results were later used by others to derive values for G and the Earth's mass."
*"The gravitational constant doesn't appear anywhere in Cavendish's paper..."
:Suggestion: change "doesn't" to "does not" (avoid contractions unless they appear inside a direct quotation)
*"A further complication is that up through the mid-nineteenth century..."
:Suggestion: "up through..." could be expressed less idiomatically; for example "until" (the article is about a British subject, so should really avoid exclusively US phraseology and spelling)
*"Equating the two formulas for torque..."
:Suggestion: the plural of "formula" is "formulae"
1.2 Manual of Style
Whilst the article is well wikilinked and encyclopedic, it has a number of compliance issues with the MoS:
*Lead: this should summarise (not introduce) the article, and be able to stand as a mini-article in its own right (per WP:LEAD).
*Headings: these should follow the guidelines on WP:HEAD. Specifically, "The experiment" should be just "Experiment", and headings should not pose questions ("Did Cavendish determine G?").
*Citations: although not really a GA requirement, it is recommended that the templates on WP:CITET are used for references. They provide a consistent means of quoting refs, and can be processed by bots for things like tracking down dead webpages or converting ISBNs.
*Style: I think quoting measurements in their original imperial units for the actual apparatus is correct in this case, but they should also have an SI equivalent (see WP:UNITS for more details, but also note the optional exception to this general rule for scientific articles).
2 Factual accuracy PASS
The article is well-referenced, and makes good use of its sources. 
3 Coverage FAIL
The subject of the article is comprehensively covered. A couple of points here though:
*"Derivation of G and the Earth's mass": Although I can see why this section has been included, it is not directly relevant to the article and detracts from its focus. As the title states, the subject of the article is the Cavendish experiment itself, so the article coverage should stick to this.
*Repetition: there are a few repetitive mentions of the fact that Cavendish did not determine G, this really only needs to be mentioned in two places (the lead and the section that deals with it).
4 Neutrality PASS
The article is neutral in its tone and contains no evidence of bias.
5 Stability PASS
The article history shows no evidence of recent edit-warring or major changes.
6 Images PASS
All images used are appropriately captioned (although "Artist's impression..." might be better than "Artist's conception" for the first image) and bear suitable copyright licenses.
Outcome
Although it is a promising and well-researched article, because there are quite a few issues to address - some of them fairly major - I do not believe Cavendish experiment can attain GA status in the short term; I have consequently failed it as a GA candidate. Once the comments above have been dealt with, please feel free to renominate the article on the candidates page for a further GA review.
If you have any concerns about the conduct of this review, you can list the article on the Good article review page for discussion by other GA reviewers. You can also leave questions or feedback on my talk page.
All the best, EyeSereneTALK 12:16, 12 September 2007 (UTC)
thread_title: GA fail

message: In Newton idea, there is no physical connection between point masses while in Cavendish experiment all masses (balls, spheres, wires, wooden rod, frame of torsion balance etc) are physically connected to each other one way or the other. Thus as a corollary the whole torsion balance is a raggle-taggle mass (balls, spheres, wires, wooden rod, frame etc). Therefore due to ramification of physical linkages, Sir Cavendish botched to represent the nitty-gritty authenticity of Newton’s gist.  
By my reckoning, the gamut of the test can only be valid if done in space where there is no other local gravitational attraction including observer.  96.52.178.55 (talk) 20:56, 2 July 2009 (UTC)
thread_title:  No physical connection in Newton's idea 

message: I, Kurosuke have fully translated this article into Japanese as :ja:キャヴェンディッシュの実験 in Japanese Wikipedia.  I would like to appreciate all the contributors for this article. --Kurosuke88 (talk) 03:42, 2 September 2009 (UTC)
replies: text: The Japanese version has been selected for From Wikipedia's newest articles: (新着記事) on 4 September 2009 at the main page :ja:Main_Page.--Kurosuke88 (talk) 14:50, 3 September 2009 (UTC)
thread_title:  Thanks 

message: Citing from the article: 
"Cavendish placed the entire apparatus in a wooden box about 2 feet (0.61 m) thick, 10 feet (3.0 m) tall, and 10 feet (3.0 m) wide, all in a closed shed on his estate."
I this correct? From the drawing "Vertical section drawing.." one may calculate the dimensions of the outer room assuming that the drawing is approximately at scale. If the balance is 1.8m then the box (or room) shown is 3*3m. Then this is what the article state as "a wooden box" and should thus be 0.61cm thick?? Could not be. It would be impossible to turn the greater leadballs from one side to the other within .61cm.  
This link page 337 indicate that the whole (pendulum system?) was enclosed in a NARROW wooden case. The article also indicate that the experiment took place in a wing of the Cavendish House, not in some shed.
The model in Sience Museum here shows the experiment housed in a brick build cabinet. 
My guess is: 
- The model in Sience Museum is correct, but does only partly show "the wooden box" as there is no indication of its thickness. 
- The brick cabinet was app. 3*3*3m placed inside Cavendish House 
- The "wooden box" is somewhat smaller, surrounding only the torsion wire and the pendulum with the small lead balls. Dimensions beeing ca 190cm wide, 61cm thick? and as high as from the floor to the upper suspension of the torsion wire = ca 250cm. 
Please correct me if I'm mistaken, or edit the text in the article. Hilsen KjellG (talk) 23:35, 26 December 2009 (UTC)
replies: text: With regard to .75", as shown in the drawing the box was hollow.  It was 14 cm thick, but the walls were made of three-quarter inch boards. --ChetvornoTALK 17:06, 29 August 2022 (UTC)
thread_title:  Dimensions of "the wooden box" housing the experiment. 

message: As the small value of G is very susceptible therefore just wondering  that the falling of the small balls towards gravitating balls is radial instead of linear. Further, the densities of small and large apended balls [Which were used for calculating the density of earth] varies unless adulterated. 
Thus would aforementiond wonky falling  and difference in densities of LEAD balls [espacially gravitating balls] have any effect on the very sensative value of historical G? 
Also, how long did it take to get the desired angle?68.147.41.231 (talk) 02:44, 9 September 2011 (UTC)
replies: text: The balls did not "fall".  See the diagram in the Derivation section.  the small balls were suspended on an arm so they swung horizontally toward the large balls.  On the subject of density, the reason Cavendish used round balls is that due to symmetry the attraction of a spherical ball toward another is the same as if all the mass was concentrated at a point at the center of the ball.  Thus the density of lead didn't matter, just the total mass of the ball. --ChetvornoTALK 01:56, 5 October 2015 (UTC)
thread_title:  Radial Falling and Density of Lead  

message: Note 14 says:
Then calculate the gravity this sand grain has:
13mg=13*10^{-6}kg
G=Mg=13*10^{-6}*9.8=1.274*10^{-4}N
According to the passage, the force involved in twisting the torsion balance was 1.74*10^{-7} N which is roughly the weight of a large grain of sand.
Is this a conflict?--Tiger (talk) 03:15, 23 June 2016 (UTC)
replies: text: Confirmed, it was incorrect. I have edited the article.--Tiger (talk) 00:54, 28 June 2016 (UTC)
thread_title:  I'm not quite sure about this data 

message: According to the article ... " The motion of the rod was only about 0.16 inches (4.1 mm).[14] Cavendish was able to measure this small deflection to an accuracy of better than 0.01 inches (0.25 mm) using vernier scales on the ends of the rod.["
OK, so the accuracy of the measurement was 0.01/.16 ~= 7%, so 1, maybe 2, significant figures. So how could he then deduce any derived quantities to a precision of 4 significant figures?  — Preceding unsigned comment added by 2001:8003:E414:3A01:962:75E8:DDE7:D4C1 (talk) 03:59, 11 October 2020 (UTC)
thread_title:  Accuracty of measurement.