Hi, this is my first post on this forum. I was attracted by the present discussion on Foucault's pendulum, and I can't really understand if anybody here is actually speaking about something you ever tried or experienced first hand.

I am a physics major, I helped building a Foucault's pendulum already in high school, and I have a pretty good idea on how to explain its motion with sufficient accuracy independently on where you set its initial position. Of course, if you want the sharp figures one typically sees in the books, you have to be careful on initial conditions. Also, clearly, you may desire to build it in order to minimize friction (and air viscosity) as much as possible: typically the pendulum has to be long and massive, and with something like good rolling bearing at the top.

But in any case its motion is described with perfect accuracy by Newton's equations. More precisely, by the equations of a constrained mass (pendulum) which moves in a non inertial frame of reference in the presence of friction.

The fact that the frame of reference is non inertial is due to the rotation of the earth, or Coriolis effect.

Apparently, there is someone on this forum that does not agree with this. This is why I am writing.

I am writing here because I have a question.

Are you aware of any alternative theory that allows one to predict the trajectory followed by a pendulum built with a very small friction coefficient? With the expression "predict the trajectory" I mean the possibility of telling which position in space will be occupied by the pendulum at any observed times. With "time" I mean the usual notion provided by an ordinary clock. With "position in space" I mean 3 real numbers denoting coordinates in the three dimensional space where one is supposed to find the pendulum at the prescribed instant of time.