Let me apologize for not being active for awhile. It is not because I came to terms with a flat Earth. Instead, I have been too busy with my life. Even so I have been studying gravity, playing chess, and traveling. Back to proofs.
20) If Earth were truly constantly spinning Eastwards at over 1000mph, vertically-fired cannonballs and other projectiles should fall significantly due west. In actual fact, however, whenever this has been tested, vertically-fired cannonballs shoot upwards an average of 14 seconds ascending, 14 seconds descending, and fall back to the ground no more than 2 feet away from the cannon, often directly back into the muzzle.
Much like how Newton’s Three Laws are really Two Laws of Motion; this is one of the arguments that is often repeated. To refresh: 1) an object in motion will stay in motion unless it is acted on by a force; 2) acceleration is equal to force divided by an object’s mass; and 3) for every action there is an equal and opposite reaction.
This test can also be performed on a train. If a person throws a ball directly vertically it will fall to the ground directly below where it fell from the reference frame of a train passenger. However, if the same ball was viewed from a person watching the train pass by, the ball would move forward with the drain and appear to have a motion described by a parabola.
While it would look like the person threw the ball vertically up and down. If you change your reference frame to a “stationary” person next to the train tracks, the person would appear to have thrown the ball forward at the velocity of the train.
Crazier still is to imagine the reference frame of a person falling off a cliff watching someone throw a ball vertically. It would appear to continue to move upward with constant velocity relative to that falling person. This idea is what separates general relativity from Newtonian relativity.