Isaac Newton was a physicist who studied motion and forces in the 1600’s and 1700’s. He is well known for his famous laws of motion but also for his universal law of gravitation. Newton’s universal law of gravitation states that all masses in the universe have a gravitational force and are attracted to all other masses in the universe. For example, there is a gravitational force between the earth and the moon and the earth and the sun. The strength of the gravitational force depends on the size of the objects as well as the distance between the objects. The larger the objects are and the closer they are together the greater the gravitational force.