The Catholic Church warned him not to do this. So, he wrote another book in which he criticized the Church for holding onto old views and made the pope look like a simpleton. A trial was finally held when he was older and he recanted all that he had written and said that he did not believe it, He died, an old man under house arrest. In 1992 the Catholic Church reopened the case and declared him not guilty. His greatest work however, had to do with the subject of mechanics.
Mechanics is the study of how objects move.
The Greeks reasoned that heavier objects fall with greater speed than lighter objects. In order to do this he had to learn how to measure distance and time very accurately. If an object changes speed or direction then it is accelerating. Slowing down is a form of acceleration. Because the longer it falls the faster it falls, a penny thrown off the Empire State building can go through a car and kill you.