Question

Is Astrology a science?

Answer 1

Astrology fails to satisfy the tests that any modern scientific fact is able to.

Explanation:

Astrology has two parts.

1. Calculations -casting of horoscope to depict position of various planets at the time of birth of a subject.
2. Predictions -predicting events or chain of events which happened or are likely to take place during the life time of the subject on the basis of horoscope drawn in 1. above.

So far as the first part is concerned, it is pure mathematics or arithmetic or if you may like to call it scientific. The rules of astronomy are well known for calculating the planetary positions. Same are applied to the casting of horoscopes. The positions of planets at a designated moment are calculated and stated in terms of pictorial representations.

For the second part let us at the beginning state what we understand of the word Science. When I googled it, the first hit was:

the intellectual and practical activity encompassing the systematic study of the structure and behaviour of the physical and natural world through observation and experiment.

Next we examine how do astrologers make their predictions on the basis of scientifically cast horoscopes.

There are set of axioms which associate a particular human trait or a happening to a specific planetary positional configuration. No where in any type of astrology, may be it is Indian, Western, Chinese Islamic or any other; the reason for such an association is explained.

Therefore, at the best it can be stated to be an empirical association in scientific terminology. It is also to be noted that these empirical associations are limited to a particular astrology. Indian astrology has its own associations and so do have others. Moreover, there is no unanimity among practicing astrologers of various regions about the axioms.
This is contrary to the laws of other branches of sciences.

In astrology, there is the longitudinal difference between the Tropical (Sāyana) and Sidereal (Nirayana) zodiacs. In some astrology practices, for example in Indian Astrology, the axioms are stated for initial time `t=t_0`, when vernal equinox point (ayanāmsa) was at zero. We know that it precesses westwards at a rate of about `50.29` seconds of angle per year (the rate has been found to be accelerating) with respect to the fixed stars. It is surprising that there is no unanimity among various schools of Indian astronomers about this `t_0` as well.

Some orthodox schools of Vedic astrology reject modern astronomy and still base their computations upon traditional texts and treatises, following the ancient Surya Siddhanta . They use oscillating vernal equinox within a rage from `0 " to "±27^@` in 1800 years; instead of cyclically moving as modern concept suggests.

Most of Indian Astrology schools have not included newly discovered planets like Neptune, Pluto, Uranus till date as there are no empirical associations about these in the original text. (Some scholars do refer to the existence of these three in traditional text, though.) Whereas other schools like Western Astrology included these outer planets on ad-hoc basis.

Further suggested reading materiel here.