# What is the simplest way to perform a Cavendish experiment?

The Cavendish experiment is cool, but seems complicated to experimentally perform. What is a simple way to recreate the experiment?

• – Qmechanic Sep 17 '14 at 16:49
• well, because the Earth is so much more massive than the equipment or objects of your experiment, it's not surprizing that it will be difficult to measure the gravitational attraction of the adjacent object (which is much, much less massive than the Earth) when such is added to the gravitational attraction of the planet your experiment is on. i wonder if they did some kind of measure of $G$ in the shuttle or ISS? or if the rooskies did something like that? – robert bristow-johnson Sep 17 '14 at 17:38
• hey, it's not big $G$ on the cheap, but if you want to see how physicists perform the Cavendish experiment today, check out the U Washington apparatus, including this time-lapse video of it in operation. – robert bristow-johnson Sep 17 '14 at 17:47
• say, i found a short physics course .pdf doc that makes an interesting reference to C. L. Stong, "How to repeat Cavendish's experiment for determining the constant of gravity", The Amateur Scientist column in Scientific American, September 1963, p267. good luck finding a copy. – robert bristow-johnson Sep 17 '14 at 18:00
• A Cavendish experiment is rather easy to perform these days, since you can measure tiny movements with capacitive sensors or a simple optical interferometer with very high accuracy. This leaves you with the usual problems of working on a very solid table anchored to a large foundation (concrete mix is dirt cheap!), getting a bunch of lead balls and finding a torsion fiber that does not suffer from non-linearities and memory effects, but other people have done the hard work for you, see e.g. physics.uci.edu/gravity/papers/icifuasPaper.pdf. Good luck! – CuriousOne Sep 17 '14 at 20:21

## 1 Answer

The way Cavendish did it would seem to be simplest - it can be done with 18th Century technology.

In practice its very difficult to do in a lab, alternately it is a very good way to demonstrate the resonant properties of concrete lab buildings.

If you wanted to try it for yourself then a garden shed, with an insulated inner room/box built of plywood and styrofoam and a vibration proof table made from stacks of inner tubes and paving slabs, and a telescope+webcam so you can keep it completely sealed. Seems plausible.

• What is C18 technology? – WetSavannaAnimal Dec 30 '14 at 11:45
• @WetSavannaAnimalakaRodVance, sorry 18th Century, it's standard history shorthand at least in British English. The experiment was done in 1799 – Martin Beckett Dec 30 '14 at 15:51