The Psalmist and the Sun Rise

The Psalmist assumed that the sky was a metallic, a firm structure. That's what firmament means. The Hebrew word refers to like a hammered surface, like a bowl. So they assumed a flat earth with a bowl that God put on top of it because that's what it looks like. And they're assuming that, but that doesn't mean scripture is asserting that we must believe that that's the truth. We, scripture is asserting other things, and it's describing the environment we see in terms of a human perspective.