A common misbelief shared by many of the same culture or region.
Penny: Um, me, okay, I'm Sagittarius, which probably tells you way more than you need to know.
Sheldon: Yes, it tells us that you participate in the mass cultural delusion that the Sun's apparent position relative to arbitrarily defined constellations and the time of your birth somehow effects your personality.
Penny: Participate in the what?
--Big Bang Theory