Originally Posted By: redewenur

"In 1985 further progress by H Pfister and K Braun showed that sufficient centrifugal forces would be induced at the centre of the hollow massive sphere to cause water to form a concave surface in a bucket which is not rotating with respect to the distant stars. Here at last was a form of the symmetry that Mach was seeking."


I find it all quite uninteresting. The frame dragging isn't really relevant. If you want a bucket that's not rotating relative to the stars, and yet the water has a concave surface, it's easy, just set up some sort of gravitational field which does that. It could be by frame dragging, or be classical gravity.

Although I suppose it shows that just looking at the shape of the water can't tell you if it's accelerating or in a gravitational field. That just comes back to the equivalence principle which is kind of fascinating but also kind of obvious.


Last edited by kallog; 08/29/10 01:32 AM.