Newton was the first one to suggest that gravity is universal and affects all objects in the universe. That’s why his law of gravity is called the law of universal gravitation . Universal gravitation means that the force that causes an apple to fall from a tree to the ground is the same force that causes the moon to keep moving around Earth. Universal gravitation also means that while Earth exerts a pull on you, you exert a pull on Earth. In fact, there is gravity between you and every mass around you — your desk, your book, your pen. Even tiny molecules of gas are attracted to one another by the force of gravity.
Joe was bored and really didn't want to do homework. He could not think of anything to write about gravity. Instead he kept leaning back on his chair and tossing his pencil in the air. He through the pencil up and every time it fell back towards him and he caught it.Once he leaned back to far and his chair went crashing to the floor. Startled he decided he should get to work.
Will the pencil always fall bsck to earth or only sometimes?