I remember doing this experiment as a physics undergrad. We had to set up the torsion balance and leave it for 24 hours to let any vibrations damp out. The prob

I remember doing this experiment as a physics undergrad. We had to set up the torsion balance and leave it for 24 hours to let any vibrations damp out. The problem was that anytime someone would close a door in the lab more vibrations would start up. I don't remember how close our numbers came to Newton's constant, unfortunately. It is a nice application of lasers to measure measure fundamental forces. Sort of the poor man's LIGO (minus the gravitaional waves): http://en.wikipedia.org/wiki/LIGO http://en.wikipedia.org/wiki/LIGO