This is known as the Law of Inertia. It is also called Newton's First Law of Motion although he didn't really invent it. Galileo said it almost right, Descartes did get it right but Newton usually ...

Facing the Inquisition for his scientific beliefs, Galileo developed many important ideas about the science of motion, such as inertia. Isaac Newton built on many of Galileo's insights when ...

yet Galileo spent his life unravelling these mysteries. His many discoveries include the law of inertia later used by Isaac Newton as the first law of motion, the parabola as the path of a ...