Astrology consists of a number of belief systems that hold that there is a relationship between astronomical phenomena and events or descriptions of personality in the human world. Astrology has been rejected by the scientific community as having no explanatory power for describing the universe. Scientific testing of astrology has been conducted, and no evidence has been found to support the premises or purported effects outlined in astrological traditions
Where astrology has made falsifiable predictions, it has been falsified. The most famous test was headed by Shawn Carlsonand included a committee of scientists and a committee of astrologers. It led to the conclusion that natal astrology performed no better than chance. Astrologer and psychologist Michel Gauquelin claimed to have found statistical support for “the Mars effect” in the birth dates of athletes, but it could not be replicated in further studies. The organisers of later studies claimed that Gauquelin had tried to influence their inclusion criteria for the study by suggesting specific individuals be removed. It has also been suggested, by Geoffrey Dean, that the reporting of birth times by parents (before the 1950s) may have caused the apparent effect.
Astrology has not demonstrated its effectiveness in controlled studies and has no known scientific validity, and as such, is regarded as pseudoscience. 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.
The foundations of the theoretical structure used in astrology originate with the Babylonians, although widespread usage did not occur till the start of the Hellenistic period after Alexander the great swept through Greece. It was not known to the Babylonians that the constellations are not on a celestial sphere and are very far apart. The appearance of them being close is illusory. The exact demarcation of what a constellation is, is cultural, and varied between civilisations. Ptolemy’s work on astronomy was driven to some extent by the desire, like all astrologers of the time, to easily calculate the planetary movements. Early western astrology operated under the ancient Greek concepts of the Macrocosm and microcosm; and thus medical astrology related what happened to the planets and other objects in the sky to medical operations. This provided a further motivator for the study of astronomy. While still defending the practice of astrology, Ptolemy acknowledged that the predictive power of astronomy for the motion of the planets and other celestial bodies ranked above astrological predictions.
During the Islamic Golden Age, astronomy was funded so that the astronomical parameters, such as theeccentricity of the sun’s orbit, required for the Ptolemaic model could be calculated to a sufficient accuracy and precision. Those in positions of power, like the Fatimid Caliphate vizier in 1120, funded the construction of observatories so that astrological predictions, fuelled by precise planetary information, could be made. Since the observatories were built to help in making astrological predictions, few of these observatories lasted long due to the prohibition against astrology within Islam, and most were torn down during or just after construction
The clear rejection of astrology in works of astronomy started in 1679, with the yearly publication La Connoissance des temps. Unlike the west, in Iran, the rejection of heliocentrism continued up towards the start of the 20th century, in part motivated by a fear that this would undermine the widespread belief in astrology and Islamic cosmology in Iran. The first work, Falak al-sa’ada by Ictizad al-Saltana, aimed at undermining this belief in astrology and “old astronomy” in Iran was published in 1861. On astrology, it cited the inability of different astrologers to make the same prediction about what occurs following a conjunction, and described the attributes astrologers gave to the planets as implausible.