Circle of Animals/Zodiac Heads Circle of Animals/Zodiac Heads Circle of Animals/Zodiac Heads is an artwork by Chinese contemporary artist and political commentator, Ai Weiwei. The work comes in a small (gold) and large (bronze) version. Created in 2010, the zodiac heads (a Rat, Ox, Tiger, Rabbit, Dragon, Snake, Horse, Goat, Monkey, Rooster, Dog, and Pig) are inspired by those which once comprised a water clock-fountain at the Old Summer Palace, which is a complex of palaces and gardens in Beijing that were constructed by the Qianlong Emperor of the Qing dynasty. The Old Summer Palace was eventually destroyed by French and British troops in
Ancient Greek astronomy Perga (c. 262 BC–c. 190 BC) responded by introducing two new mechanisms that allowed a planet to vary its distance and speed: the eccentric deferent and the deferent and epicycle. The deferent is a circle carrying the planet around the Earth. (The word "deferent" comes from the Greek fero φέρω "to carry"and Latin "ferro, ferre", meaning "to carry.") An eccentric deferent is slightly off-center from Earth. In a deferent and epicycle model, the deferent carries a small circle, the epicycle, which carries the planet. The deferent-and-epicycle model can mimic the eccentric model, as shown by Apollonius' theorem. It can also