Gravitational Pull; Gravity

                                                                           Gravity
     Gravity is the natural, invisible force that pulls things in. Without gravity, all of the planets, stars, Earthlings, Earthlings' properties, and etc. can go flying all around the universe. Earthlings can die if there weren't any gravity pulling them in. Gravitational pull from the sun is what keeps the planets in their orbits. It is the force that acts upon everything. 

Sir Isaac Newton found the theory of Universal Law of Gravitation
 after an apple fell on his head.

     The modern idea of gravity came from Galileo Galilei. He and his assistant were standing on the Tower of Pisa, holding up two balls. The balls were different sizes: one small and one big. When the balls were released, they hit the Earth ground at the same time. Galileo did this experiment again rolling down the ball using inclines. The balls hit the Earth ground at the same time again.Galileo showed that gravity makes things fall at the same rate. Sir Isaac Newton, an English mathematician, developed the Universal Law of Gravitation which helped scientists with their discoveries of planets and other theories.