Where's the Curvature, Twilight?

Fluttershy pushed in the door to Twilight’s tree home, instantly assaulted by the smell of old books. There was a gentle lighting in the main room of Golden Oaks, as the window perfectly caught the beautiful oranges and purples of the sunset.

Inside the library were two ponies and a dragon. The alicorn, Twilight Sparkle was reshelving her books for probably the third time that week. The other pony, the pegasus Rainbow Dash, was relaxing on a small army’s worth of pillows, reading a Daring Do book. The dragon was Spike. He was doing nothing interesting, per usual.

“Hey Flutters.” Rainbow Dash called from her little zone, peering over the top of her book for just a moment to recognize the new pony in the room.

This caught the attention of Twilight, who had been completely engrossed in her task. She turned around and smiled. “Hi Fluttershy. How are you?”

Fluttershy smiled back. “I’m great Twilight! I just came by to see if you have the new Compendium of Exotic Flora book I was looking for earlier.”

Twilight’s eyes lit up. “Oh I had it put somewhere around here.” After a brief moment of looking around, Twilight found it and levitated it over to Fluttershy, who happily grabbed it and slipped it into her saddlebags.

“It’s great!” Twilight gasped. “It has all these interesting plants from all around the world. Why, I didn’t even know about half of them.”

Fluttershy tittered. “I can’t wait! But it can’t be from around the world Twilight, the Earth is flat.”

For a few moments there was a very pregnant silence and Twilight struggled to accept what she heard was really true.

Twilight's eye twitched. "Fluttershy, what did you say?"

"Well everypony knows it, Twilight. The Earth is flat." Fluttershy replied.

"I'm sorry what?" Twilight replied icily, a bit more forceful than intended. Fluttershy shrunk back instinctively. "Fluttershy, the Earth is not flat. Ponethagoras discovered that almost 2,500 years ago."

"Well u-um... that was a long time ago, and a lot of thoughts from that time have turned out to be w-wrong..."

Twilight sighed and facehooved. "Okay Fluttershy, tell me why in Equestria you would get the crazy idea that the Earth is flat."

"U-um, okay. Well, there's the fact that we don't have any pictures from space... and Celestia controls the sun, which is probably a couple thousand feet from the atmosphere, and can just move in circles around the world. It'd probably be a lot easier than the theory that Princess Celestia is constantly moving the sun around an entire giant floating sphere, and that it's hundreds of thousands of miles out there. It's like... a spotlight."

"A spotlight." Twilight huffed. "You think the sun is like... a spotlight?"

Fluttershy looked around rapidly, meeting Rainbow’s gaze, who much to her chagrin, didn’t jump in to help her. Fluttershy looked back at Twilight meekly.

"Well I mean... Maybe that's not the best metaphor but..."

"Simile." Twilight corrected. "And Fluttershy, that's absurd! If the sun was that close to Earth it would scorch this planet dry!"