1. The Cannonball Through the Earth Experiment
Imagine a perfectly straight hole through a perfectly round solid earth going from the north pole to the south pole. There is no spin, and there is no atmosphere in the hole, just space. Of course this is completely ridiculous, but imagine it anyway. The thought experiment is what would happen to a cannonball dropped into the center of this hole, say from the north pole?
Consider these possibilities:
- The ball starts falling down the hole towards the center of the earth gaining speed, will reach the center with a certain speed, and then continue moving, now up the hole towards the south pole losing speed. In a perfect experiment the cannonball will rise slower and slower until it reaches the surface of the hole at the south pole, come to a momentary halt, change direction and start falling back into the hole, maintaining this free fall pendulum in perpetuity.
- The ball starts “falling” down the hole towards the center of the earth at first gaining speed, reaches a maximum, and then starts to “fall” slower and slower until it finally comes to a stop at the center of the hole and will then stay there suspended in place for perpetuity.
2. The Cantilevered Pendulums Experiment
Question: Which will happen A or B?
This experiment may be viable:
1. Use photons to measure the gap between the strings top and bottom. A smaller gap (A) implies a pull, the same size gap (B) implies a push.
2. Use photons emitted from the cantilevered ball reflecting off a liquid mercury surface that follows the curvature of the earth. The angle of incidence and the angle of reflection would be suggestive.