I always thought that the channels were set on your car radio and you couldn't change them. I'm ashamed to admit that I believed that until I was 24 years old and my husband explained it to me! Good thing this is an anonymous post because I'm a published novelist and not too proud of this!
A childhood belief about radio

others believed things like this
- I believed the sun and the moon were the same thing, just rotated to change from day to night.— Daniel
- I could never work out how they used to change the bands over so quickly when i listened to the radio— graham
- When i was a kid, i thought that the tv changed channels by dark magic.— Anna
- Up until I was 10 or 11, I thought the word anonymous was 'annoymous'.Anon
- I believed for years that the sun and moon were the same thing - it just glowed more in the day :)— Deb
- my husband believed, until recently, that the word "several" meant seven of something. — sheryl