Rock balancing is an activity in which rocks are balanced on top of one another. It is possible to do it if Earth is rotating because the speed is constant and the rocks are affected by a constant net acceleration from gravity and Earth’s rotation.
Flat-Earthers use rock balancing as “evidence” that Earth is stationary. In reality, it is possible to balance objects on a moving platform, as long as it is moving in a straight line with a constant speed, and there is no force —like wind, affecting it.
- Rock balancing – Wikipedia