"But like it has to be high up to go in orbit. I think."

"Orbit?"

"The Earth goes around the Sun. The Moon goes around the Earth. There are also artificial satellites in orbit around Earth. Orbiting is basically falling in such a way as to invariably miss. You have to be pretty high up to keep missing."

"...I'm missing something, that doesn't add up."

"Um... I don't know what it would be."

She considers it. 

...she looks out the window. 

"...is your world spherical?"

"Is yours not?"

"It's flat - huh - it is spherical, Nelyafinwë, look at it -"

"...it's curved, I'll grant you that -"

"It's spherical! We know it to be spherical!" Isabella assures them. "It has poles and an axis and it spins around! I have mentioned before that it spins around! Why is your planet flat! How does it do that!"

"Magic. The Valar made it flat and made the ground down."

"Okay that one I am really sure is dumb."

"I'm very willing to believe that but what are the advantages of spheres?"

"...you can't fall off the edge," says Alex definitively after a pause.

"Can't fall off our edge either, you just get - stuck to the side."

"That sounds inconvenient too!"

"True."

"Spherical planets do not require magic. Also they have volcanoes, which are not an unalloyed good but are pretty cool. Unless you have magic volcanoes."

"I think Melkor was a volcano at one point."

"...where did she even get the idea. Volcanoes require magma. Magma requires extreme heat and pressure of the kind you get in a spherical planet. Is your flat planet just really thick...?"

"I don't know, but at that point there was no life, just the Valar goofing around, so perhaps they stumbled on it somehow just checking what happens if you put lots of rock under pressure -"

"I suppose. But they never tried putting a lot of rock in zero gravity and noticing it coalesced into a spherical planet?"

"I have no idea. I'll ask Aulë when I get back."

"Well, it's a very nicely done artificial gravity, anyway."

"It's never bothered anyone, that I've heard of, but we haven't tried, ah, orbit."