Actually, what you are calling "the theory of gravity" is true, and it was proven true by a New England farmer nearly 250 years ago.
You see, Isaac Newton imagined a cannon ball shot horizontally to the Earth. You see if you shoot it, it will fall to the ground as it is going forward. The faster you shoot it, the farther it will go before it hits the ground. However, since the Earth is a ball, if you shoot it fast enough, the Earth will bend away from the cannon ball... and it will keep being pulled toward the center of the Earth so that if with enough speed, the ball will travel all the way around the Earth to the cannon.
However Newton never tried this with an actual cannon. This was first tried by a farmer in Concord Massachusetts who had more cows than cannonballs, so he rigged up a cow cannon to shoot his cattle at a very fast rate. Sure enough, he was able to launch his cows fast enough to the East that after some time had passed they would come back from the West to land at his feet.
Does anyone know what this amazing feat is called.... ?