I don’t think we are seeing the same “foundation” here AJ. Cause the one I’m looking at, is as curved as a freshly picked apple~

@T72B  
Well, seeing how moving the sun is depicted; IE moving to a position and staying there, I think the heavenly bodies are in some semblance of a geostationary orbit, since they’re not really shown to move outside of being manually moved. The only momentum they are imparted with is the amount necessary to keep them moving in-line with ground, as otherwise they’d either have some sort of magic of their own to float, or they’d plummet into the planet and destroy it.

@Respectful Batpone  
i wonder if the princesses need to expend a little bit of magic and focus at all times to maintain solar movement or if they only need to give the sun moon a push at the start of the appropriate movement cycle. maybe thats why celestia is always so aloof, she needs to concentrate on moving the sun slowly across the sky
 
 
or if their world is flat, does celestia build a new sun everyday? like i big magical ball of burning pitch?

Love to see the debate on how a system that probably didn’t have a ton of thought put into it would actually work.  
And that’s not sarcasm. Theorycrafting is a lot of fun. To throw my own spin on it, I think the image @bersl2 put in is probably correct for Equestria; a round egocentric model. The day and night would simply be reversed on the other side.  
Makes me wonder how confused creatures on that side would be during moments like Princess Twilight, where the sun and moon would just… fuck off, outta nowhere. Or Return of Harmony where they have no idea what the fuck a “Discord” is.

@Hermit09  

@WyrmSpawN  
Fair enough, though I don’t remember seeing them (which is a shame since I’m a geography nerd).

@Hermit09  
I mean, they have globes.

To be fair, I don’t think we’ve ever seen Equestria from space in the show and, considering that Celestia and Luna literally raise the Sun and the Moon for the entire world, it may very well be flat.

…but fertile.

Yeah, it is indeed flat. Unlike other things.