Not that it matters. Flerfers have had decades coming up with increasingly elaborate and absurd cosmologies. They don't understand them, but that's what science looks like to them as well, so they figure it's your word against theirs. And since their word is the Bible, they win.
If they were genuinely curious, there are a million ways to show the roundness of the earth. But there are zero ways to demonstrate it to a person who is fundamentally incurious and doesn't want to know.
https://physics.stackexchange.com/questions/26427/what-is-th...
The firmament is the sky, not the ground.