Postscript

WHEN GALILEO set out to found a new science, he firmly denounced all forms of occultism. Physics was to become a mathematical science. Consequently, Galileo accepted only dimension and motion as primary qualities of a body; these he considered mathematical qualities. God is seen as the great geometer who has given measure to all things. Galileo did not presume to say that all aspects of the order of the universe could be explained and understood on this basis. The abundance and diversity of phenomena seemed to him beyond the capacity of human mathematical thought. But since there are mathematical laws underlying all phenomena, it seemed reasonable to select individual and isolated phenomena and to represent them mathematically, much the same way Archimedes did. Galileo believed that this would at least provide complete and definitive answers to specific questions. The basis of Galilean physics was the idea of “natural” motion. It is an Aristotelean concept, but Galileo gave it an important new meaning. His cosmology is founded on the Copernican world system which designates the circular orbits of the planets around the sun as “natural” motion requiring no further cause. Now the earth is also a celestial body. Therefore, if the earth was a perfect sphere with a perfectly smooth surface, then a body on it, once set in motion, would move with a constant velocity around it. This movement is circular and “natural” and corresponds to the “law of inertia” as Galileo understood it. He believed that by applying this law he had found a theory of tides of which he was very proud.