Newton's First Law
Newton's First Law of Motion is the easiest to understand. Unless something exerts a force onto an object, the object will stay at rest. So unless you have telekinetic powers, you can not make an object move. There is a second part to the law; an object will move at a constant speed unless a force in applied onto it. While we take this law for granted, it took scientists a long time to grasp this concept. Aristotle, a famous Greek scientist (384 BC - 322 BC), incorrectly believed that continuous force was required to move an object at a constant velocity. He further stated that natural state of an object was to be at rest (still). This idea seemed logical at the time and even now. When you push an object across a table, it stops sometime or later. But people back then did not know about friction. Galileo, a scientist some 2000 years later thought differently from Aristotle. While Galileo is widely known because of his astronomical work, his idea on force contributed to Newton's ideas. He believed that the natural state for an object was to be at rest or to be moving at a constant velocity. Galileo was one of the first people to recognize a world without friction. Newton's First Law is very close to Galileo's conclusion and Newton acknowledged Galileo's work in his book Principia.
