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. 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.
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.
Astrology has been rejected by the scientific community as having no explanatory power for describing the universe (see pseudoscience). Scientific testing of astrology has been conducted, and no evidence has been found to support any of the premises or purported effects outlined in astrological traditions. Where astrology has made falsifiable predictions, it has been falsified. There is no proposed mechanism of action by which the positions and motions of stars and planets could affect people and events on Earth that does not contradict well understood, basic aspects of biology and physics.