When I was really little, probably about 4 or 5 years old, I knew what gravity did (keeps you planted to the ground), but I used to think that the source of gravity was someone named Mr. Gravity, who lived under my parents' bed! I had a mental image of what he looked like and everything... I would also look underneath my parents' bed, trying to search for "Mr. Gravity". My parents never corrected me, probably because they thought it was "cute" or something.
I even thought that under this same bed was a planet of its own... I was a very, umm, imaginitive child!
A childhood belief about physics

others believed things like this
- I thought if someone hadn't passed the Law of Gravity, we would all be floating around in space.— Trudee
- I used to believe that until gravity was invented, people used to just float around!— Meg
- Ironically my parents were born on the same day; so growing up, I thought all parents had the same birthdays. Anon
- when i was 5 i used to think that people only live for 10 years and i thought that my parents were 7.Anon
- I used to think that if you met your parents' boss, your parents would be fired!! AAAAAHHHHHHH!!!— Spoot
- that as I grew up, my parents would "grown down," then I would be the Mom and Mom would be my child.Anon