Galileo Galilei invented kinematics and disproved Aristotle's old theory of gravity. One of his students said he dropped two balls of iron (one weighing one pound, the other a hundred) off the leaning tower of Pisa. The objects fell at the same speed which brought about new methods of thinking in that time period. In 1542, Nicolaus Copernicus published his work "On the Revolutions of the Heavenly Spheres", in which he said that not the earth, but the sun was at the center of the universe. This theory is known as Heliocentrism today. In the same year, Andreas Vesalius pubilshed his work "On the Structure of the Human Body". This book is about the anatomy of the human body. 