As a lecturer at the University of Pisa in 1589, Galileo Viviana gave a demonstration of his theory of acceleration atop the Leaning Tower of Pisa before his colleagues, students, and philosophers. He dropped both a wooden ball and an iron ball simultaneously from the tower. Both landed at the same time. Galileo then revealed that both balls were made of the same material but of different weights. Note that this was not an experiment but a demonstration that signified his flair for the dramatic. Galileo had studied this concept intensively before the incident. His words on the debate of weight verses acceleration were "Ignorance of motion is ignorance of nature." There were many myths about the demonstration and the theory itself. One was he first noticed the movement of pendulums by watching them swing from the lamps of a cathedral at which his father was doing musical research. The truth was that these lamps were not even installed at the time. However, he only noticed the motion of pendulums fourteen years later. His first comment on this motion was "what moves moves, as it were, by force and by the extruding action of the medium." This refers to the theory that an object's motion remains constant depending on its internal and external pressure. .
Hard as he tried, Galileo could not get objects of different materials to fall alike. So he investigated this matter. Galileo's first approach to testing this theory was to observe how specific weight effects the fall of different bodies. According to him, the density of an element is determined by the nearness of the center of that element. Therefore, he tested the sink and float of iron verses wood in a tub of water. He submerged a piece of wood weighing four (4) units in a tub of water weighing six (6) units. The wood rose at a speed of two (2). Done again with the same piece of wood and water that is ten (10) units the rising speed would be six (6) units.