This is a continuation from Why astrology is not scientific, while astronomy is.
Using scientific theories to discover unknown planets, reinforced Newton’s theory of universal gravitation and proved its usability. But there is nothing sacred about Newton or his theories. Had astronomers not found the planets as expected, Newton's Theory of Gravitation would have been falsified, and would have to be replaced by a theory that could better explain the discrepency in the orbit of Uranus.
Meanwhile, astrologers were enthusiastic about these discoveries, which increased the range of heavenly influences they could explain. They were quick to assign power and influence to the three planets, and associate the discovery of each of the planets with events characteristic of these powers. The discovery of Uranus, associated with human rights, rebellion and progress, was related to the American and the French revolutions of 1778 and 1789 respectively. The discovery of Neptune, the planet linked to both cults and the occult, was closely followed by the emergence of a Chinese clerk, Hung Hsiu-Ch'üan, who decided that he was the son of God, and in 1847 attempted to conquer China and establish his own dynasty. It is believed that more then 20 Million people were killed during his Taiping Rebellion. The discovery of Pluto, which rules atomic energy, is associated with Cockcroft and Walton splitting the atom in 1932.
Astrologers forecast; yet there are no known records of astrologers foretelling the discovery of the new planets. No mismatches between astrological observation and earthly events had ever been attributed to unknown heavenly bodies, nor is there any evidence whether adjusting the charts for the new planets has improved the accuracy of astrological predictions. Whatever the reason for the planets’ orbital mismatch might have proved to be, astrology would have remained unchallenged, irrefutable, and therefore, by definition, unscientific.