It doesn't fit the vehicle categories, but I think this one's pretty good:
When we were kids a friend of mine thought a ten centimeter long propeller driven ship I had in my bathtub was exactly as fast as the ferrys from Norway to Denmark, because it was a copy of one of them. I disagreed even though I was two years younger. We got into a really long and tiresome argument about it, and I don't think we ever managed to agree. It's been years since I saw him, but if I run into him maybe I should ask if he still thinks it could be the case. He's 34 now.
A childhood belief about physics
others believed things like this
- I thought that 1983 went on for 3 years - had to ask my sister who decided how long a year lasted.— Sally
- When I was 7 years old I used to believe that the Pirates with their ship they really existed — Enrico
- when i was like 6 i thought only little kids my age could have long hair. dumb....lol— candy
- I'm an American, and for a good long while I thought that Boxing Day involved the sport of boxing.— miss Taken
- I used to think those propeller hats could actually make you fly. — Meghan
- I used to believe anyone who disagreed with me was an idiot.— Catte