It's actually more complicated than just about anything else too! After years of studying this subject, I think that astrology does not "measure" compatibility, but it does make valid assessments of attraction and tolerance for another. In the past 40 years over 50 books have been written on "astrological compatibility" -- espousing at least as many different ideas on how to measure this elusive item. So? What works? Let's look at the seven visible planets in and between two charts and see what those can tell us. Then too, don't forget those chart angles!