I used to think that when you squint your eyes and go a little crosseyed, and you see the little spots and bubbles floating around that I could see air molecules (this was shortly after learning about solids, liquids, and gases, and how gas molecules are loosely scattered). I told my dad this and he tried to explain the truth to me, but I believed the molecule theory for a long time.
A childhood belief about physics

others believed things like this
- I used to believe all liquids were water-based with things added to it to make different kinds of liquids.Anon
- I used to believe that eyes where just like bubbles and if you where to touch them they would pop.— Adam
- i used to believe that if you watched TV for a long time, your eyes would turn into squares.Anon
- when i was young i thought god was a cloud, big white fluffy cloud floating around with 2 eyes and a smile. — kerrie
- I used to believe that if i watched TV for too long, my eyes would turn square. As told to me by my mother.— Alex
- I used to believed that the clouds in the sky were floating piles of mash potatoes .— Funny Guy