what makes pseudo-science pseudo?

In this blog, explain what the differences are between pseudo-sciences and hard sciences by analyzing a few. You can explore the differences between astronomy and astrology, crystology and geology, feng shui and...(whatever).

The main difference between science and pseudo-science is that scientific hypotheses are testable, whereas pseudo-scientific ones are not. There are 2 reasons for which pseudo-scientific hypothesis can't be tested:

1- vagueness: if a statement is vague enough it'simpossible to be proven right or wrong. A scientific statement is instead more precise, it uses words which meanings are defined and it usually gives a reference to a certain period of time.

2 - Ad hoc exceptions: it is an exception made especially for the case you want to prove. A good scientifc hypothesis is one that is general in nature and does not keep making exceptions, but it tries to improve and learn from the mistakes.

If you take astronomy and astrology you can see that astronomy is a rational and careful study of the stars and their movements; you have to deal with mathematics, with the law of physics, and struggle with your perception and you'll never be 100% sure, however if you design an experiment, other people will be able to understand your studies and eventually disprove your theory and predictions. ON THE OTHER HAND, astrology is just a bunch of people giving random meanings to the planets and their movements and pretending to apply these meanings to your personal life; in order to do so, they are extremely vague and so there is no way to prove them right or wrong because their predictions are evaluated on a very personal level and therefore not really scientific because there are no laws that says, for example, that lions are bossy.