# General Astronomy/The First Physics

Anaximander (611-547 BC) postulated that there were five elements: earth, air, fire, water...and quintessence, which heavenly bodies were made of.

Astrology is based on Ptolemy's Tetrabiblos, written in 140 AD. The horoscope is divided up into 12 "houses", 12 constellations along the ecliptic. Ptolemy believed that an "8th Sphere" held up the stars in the sky.

Kinetic energy is the energy of motion. The formula for this is ${\displaystyle {\frac {1}{2}}MV^{2}}$ (${\displaystyle M}$ is mass, and ${\displaystyle V}$ is velocity).