3 ms·
> He floated a hollow copper sphere in a tank of water and placed it near the edge of a cliff. In 1987 Thieberger reported that the sphere consistently moved in
by ithkuil 10y ago
> He floated a hollow copper sphere in a tank of water and placed it near the edge of a cliff. In 1987 Thieberger reported that the sphere consistently moved in the direction of the edge, where the gravitational attraction by the surrounding rock was smaller—just what you’d expect if there was indeed some repulsive force that counteracted gravity.
Hmm. Wouldn't the water in the tank be attracted towards where there is more rock and thus introduce a slight slope which makes the floating sphere move towards the cliff?
Like when you have a helium filled balloon in a car and accelerate: the balloon moves to the front (because the air gets pushed to the back because of its inertia).
- Udik 10y agoHmmm no. The balloon (and the sphere) are pushed in the direction opposite to the sum of the forces applied to the surrounding fluid. Since the surface of the fluid is always orthogonal to those forces, there is no reason for a floating object to move in any direction but up with respect to the surface of the fluid. In other words, the fluid is not sloping, it's your head that's tilted :)