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.
Aries is an astrological sign that is associated with the constellation Aries. Under the tropical zodiac, Aries is occupied by the Sun from about March 21 to April 19 (depending on the exact year) and is associated with the Spring Equinox. Under the sidereal zodiac, it is currently from April 15 to May 15. The opposite sign to Aries is Libra.