I used to think thunder was caused by clouds banging into each other. (I'm still not absolutely sure this isn't true!) I also believed that the wind was caused by the trees waving their branches around--and am amazed to see how many other people believed the same thing!
A childhood belief about thunder and lightning

others believed things like this
- I used to think that the wind was caused by all the trees waving about.— dismal dunc
- I believed that wind was caused because the trees moved. I was completely sure my conclusion was correct.— Glenr
- I used to believe that the wind was caused by trees so you could stop the wind by getting rid of trees.— Nira
- I used to believe that the trees moving caused the wind to blow.— naomi
- When I was a kid I thought that the wind was caused by the trees fanning their leaves...— GDP
- I use to believe that the trees caused the wind to blow by swaying back and forth, like a chinese fan. — Jason Blanchette