What Causes an Object to Move?

The laws of motion were discovered by Isaac Newton in 1687. He discovered that force is required to move an object and that once that object was moving, nothing could stop it or make it move faster or slower, except for another external force. An object that is not moving won't start moving until some force is placed upon it. This law is called the law of inertia. This and Newton's other laws are hard to observe on Earth, where gravity and friction play a part on moving objects.