If you come to where I live you can see the earth is not flat!
It's got bumps all over it. Not a flat bit in sight. Down this way we call them 'hills'. A bit further south from here there are some much bigger hills, an the people there call then 'mountains'.
They also have some flat bits here and there, but they are surrounded by bumpy bits.
so the earth is - Bumpy!
I think I'll start up my own Bumpy Earth Society. :-)