Astrology consists of belief systems which hold that there is a relationship between astronomical phenomena and events in the human world. In the West, astrology most often consists of a system of horoscopes that claim to explain aspects of a person's personality and predict future events in their life based on the positions of the sun, moon, and other planetary objects at the time of their birth. Many cultures have attached importance to astronomical events, and the Indians, Chinese, and Mayans developed elaborate systems for predicting terrestrial events from celestial observations.
Among Indo-European peoples, astrology has been dated to the 3rd millennium BCE, with roots in calendrical systems used to predict seasonal shifts and to interpret celestial cycles as signs of divine communications. Through most of its history, astrology was considered a scholarly tradition. It was accepted in political and academic contexts, and was connected with other studies, such as astronomy, alchemy, meteorology, and medicine. At the end of the 17th century, new scientific concepts in astronomy and physics (such as heliocentrism and Newtonian mechanics) called astrology into question, and subsequent controlled studies failed to confirm its predictive value. Astrology thus lost its academic and theoretical standing, and common belief in astrology has largely declined.
A clock is an instrument used to indicate, keep, and co-ordinate time. The word clock is derived ultimately (via Dutch, Northern French, and Medieval Latin) from the Celtic words clagan and clocca meaning "bell". A silent instrument missing such a mechanism has traditionally been known as a timepiece. In general usage today a "clock" refers to any device for measuring and displaying the time. Watches and other timepieces that can be carried on one's person are often distinguished from clocks.
The clock is one of the oldest human inventions, meeting the need to consistently measure intervals of time shorter than the natural units: the day; the lunar month; and the year. Devices operating on several different physical processes have been used over the millennia, culminating in the clocks of today.
The study of timekeeping is known as horology.
An astronomical clock is a clock with special mechanisms and dials to display astronomical information, such as the relative positions of the sun, moon, zodiacal constellations, and sometimes major planets.