Galileo's research marked a crucial stage in the process leading to the formulation of the modern concept of motion. The Pisan scientist was the first to establish the laws that, in natural motion, govern the ratios between distances traveled and time elapsed. Galileo asserted the direct proportionality between acceleration and time. He also formulated the laws of pendular movements; according to legend, the starting point was his casual observation of the oscillations of a lantern in the Cathedral of Pisa. In the Dialogue, he included highly perceptive comments on the relativity of motion. And, in the Discourses and demonstrations, he showed that projectiles travel on a parabolic path. Galileo ably combined mathematical reasoning with the evidence obtained from systematic observations of pendular movements and descents along inclined planes, as well as from ingenious experiments such as the probably apocryphal dropping of spheres of different materials from the Tower of Pisa.