# 200 Proof: Relative Motion

24) If Earth and its atmosphere were constantly spinning eastwards over 1000mph then North/South facing cannons should establish a control while East-firing cannonballs should fall significantly farther than all others while West-firing cannonballs should fall significantly closer. In actual fact, however, regardless of which direction cannons are fired, the distance covered is always the same.

This is the same inertia argument from before not once but twice.

The author is missing two points. First, the cannonball sitting in the cannon is moving at 1000 mph and the target is moving at 1000 mph. Therefore the cannonball will have no greater or lesser impact based on its direction of fire.

The second problem with the author’s logic is he constantly changes the reference frame. When measuring the resting cannonball that is about to fire east, it is moving at 0 mph. When the cannonball is fired it is moving at some velocity plus the velocity of the surface of the Earth. The target is also moving at 0 mph.