From the time of Aristotle to that of Galileo, physics had remained pure theory unmixed with knowledge gained from experience. Mechanics as a mixed science being regarded as subordinate and inferior to physics, the concept of a domain for the practice of physics did not exist until the seventeenth century. The practice of astronomy existed separately from the science of cosmology, and a certain tension between them held ever since Hipparchus and Geminus. A similar tension had held since antiquity between music theorists and practitioners of music. The same is true of architecture and hydraulics. But physics, by Aristotle's definitions, had no practical component.