Astrology comprises several systems of divination based on the premise that there is a relationship between astronomical phenomena and events in the human world. Many cultures have attached importance to astronomical events, and the Indians, Chinese, and Mayans developed elaborate systems for predicting terrestrial events from celestial observations. 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.
Astrology has been dated to at least the 2nd millennium BCE, with roots in calendrical systems used to predict seasonal shifts and to interpret celestial cycles as signs of divine communications. A form of astrology was practised in the first dynasty of Mesopotamia (1950–1651 BCE). Chinese astrology was elaborated in the Zhou dynasty (1046–256 BCE). Hellenistic astrology after 332 BCE mixed Babylonian astrology with Egyptian Decanic astrology in Alexandria, creating horoscopic astrology. Alexander the Great's conquest of Asia allowed astrology to spread to Ancient Greece and Rome. In Rome, astrology was associated with 'Chaldean wisdom'. After the collapse of Alexandria in the 7th century, astrology was taken up by Islamic scholars, and Hellenistic texts were translated into Arabic and Persian. In the 12th century, Arabic texts were imported to Europe and translated into Latin, helping to initiate the European Renaissance, when major astronomers including Tycho Brahe, Johannes Kepler and Galileo practised as court astrologers. Astrological references appear in literature in the works of poets such as Dante Alighieri and Geoffrey Chaucer, and of playwrights such as Christopher Marlowe and William Shakespeare.
A clock is an instrument 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 physical processes have been used over the millennia. The evolution of the technology of clocks continues 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.