I used to believe (and still do?) that the earth hadn't been molten and retaining a centre of moltem metal, but had merely caught fire on the outside and a thin layer of molten earth remained. This was borne out by Jules Verne, in his 'Journey to the Centre of the Earth' book, So maybe I'm right?
A childhood belief about landscape

others believed things like this
- I used to believe that there was only one lighthouse in the world and it was at the centre of the earth. Anon
- We were told that the bread crust is more healthy than the centre.— Arnon
- i used to think only children whose parents don't want them anymore goes to childcare centre.— Long long ago
- i used to believe that you could see 2 suns from somewhere on earth— bramblepicker
- I used to believe we lived IN the earth rather than ON it.— AC
- I used to believe that the earth was flat.— Rt.y