Talk:Cavendish experiment
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[edit] Requested move: Torsion bar experiment → Cavendish experiment
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.
[edit] Fourmilab is bogus
The do-it-yourself experiment at Fourmilab ([1]) 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)
Correction: Upon closer examination of the video, the torsion bar is actually touching the platform that one of the weights is placed upon. When he moves the weight, the foam shakes, knocking the styrofoam bar away. Furthermore, styrofoam is notorious for accumulating a large static electricity charge. All John Walker found was static electricity, not gravity. - CronoDAS 04:39, 20 August 2006 (UTC)
[edit] Add a picture
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)
