The other day I was reading a simple experiment to determine (yes, very roughly) the constant of gravitation, all using simple tools in your basement. http://www.fourmilab.ch/gravitation/foobar/" [Broken] What struck me about this experiment is another that I remember from childhood cartoon shows - using a free-swinging pendulum which will 'rotate' due to earth's rotation over the course of a day. I suddenly got the notion in my head that this gravitation experiment, where the two masses are hung by a string, might be affected by natural rotation! Someone please either confirm this potential error, or help me get this doubt out of my head. PS: I'm assuming the damping 'stuff' is the solution to my question, if anyone can fill in the blanks it would be greatly appreciated.