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 Carlson and 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 organizers 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 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 in the way astrologers say they do that does not contradict well understood, basic aspects of biology and physics