Rivers were used to turn watermills and the Romans even used geothermal water for heating. Until the middle of the 18th century renewable sources of energy were the only forms of energy available, but then, with the advent of the Industrial Revolution, fossil fuels began to be exploited.
The Sidereal Zodiac is the position of the sun referenced against the star background, as a measure of the flow of time. The framework for the star background is the constellations the sun passes in front of. This is the one astronomers use.
The Sidereal zodiac, like the more familiar Tropical zodiac (currently used by most Western astrologers), is divided into 12 equal segments of 30Â° each. These divisions bear the familiar names Aries, Taurus, etc. The basic difference is that the start of the Tropical zodiac zero degrees Aries (0Â°^) is permanently identified with the vernal equinox, while the Sidereal zodiac is measured in a way that fixes it against the starry celestial backdrop.