I was taught in elementary school (I never figured out if the teacher was lazy or just did not understand it herself) that the reason the moon has phases is that half of it is smooth and half of it is pock-marked (That half got hit with asteroids). As the moon turns, only the shiny side reflects light. So when the shiny side is facing you all the way, you get a full moon and so on. I'm ashamed how long I believed that without questioning it.
A childhood belief about outer space

others believed things like this
- i used to think that the moon would follow you in the car, also that it looked like a half moon.— natalie k
- I used to believe that a half moon was gods finger nail, and his finger was pointing downwards.— clo
- I used to believe that Moon is the kid of Sun, because it has less light and Moon smiles with kids. — Syed Arbab Ahmed
- I used to believe that your belly button was what held your top half to your bottom half...— Debelouwho
- I always saw a crocodile on the moon, none of this man-in-the-moon nonsenseAnon
- The moon is full of wotsits.Anon