Pinkie Pie poked her head out of Sugarcube Corner. "Hi, Rainbow Dash!"

Rainbow landed on the ground. "Hey Pinkie. How did you know I was passing?"

"My left back hoof was tingling, and that means a friend is coming by feeling mildly annoyed!"

"Wait, I thought tingling left back hoof meant somepony in the town was dousing for water."

"No, silly, that's an itchy left back hoof!" She reached out, yanked Rainbow Dash inside, and handed her a cupcake. "So, what's bothering you today?"

"I was talking to Twilight and she mentioned something called 'entropy.' I didn't know what it meant, but it sounded really cool! But then the daily pile of fanmail arrived and she had to go respond to it, so she couldn't tell me what entropy was. Probably for the best anyway; she would've spent three hours lecturing me about it. Still, I was kind of interested, and now it's going to bug me for ages." She took a bite of the cupcake. "Wait, Pinkie, I thought you weren't supposed to give anypony free cupcakes anymore."

She shrugged. "The Cakes said it was okay as long as I only give them out to my really close friends, like you! And only one a day. And silly, you don't have to sit through three hours of lectures OR have existential dread and confusion hanging over your head! I can explain it to you!"

"This ought to be interesting," Rainbow mumbled into what little was left of her cupcake. "And it wouldn't have been existential dread, anyway."

"Eh, you say po-tah-to, I say to-may-to."

"Wait, those are two totally different words."

"Exactly! Because we're saying different things!"

"Huh?"

"Anyway! Entropy is like this. Imagine you've got a vase, okay? A pretty glass vase. But one day it falls off the shelf, hits the floor, and shatters into a million gazillion pieces! Oh no!"

"Pinkie Pie, my floor is made of clouds."

"Fine, then. Twilight has a vase and she drops it on her hard crystally floor. It breaks. Is it still a vase?"

"Huh?"

"If you look at it after she drops it, would you see a vase?"

"Well, of course not. It would just be a pile of shards on the ground."

"Exactly!"

"I don't follow."

Pinkie Pie stood up. "Maybe if I show you it would help. I'll go get a vase!"

"No! I, uh, I don't think that'll be necessary, Pinkie. Just explain what a pile of shards has to do with entropy."

"Oh!" She facehooved. "Silly me, I skipped a step again, didn't I? Well, the point is that you could glue the vase back together, but it'd never be exactly the same, and so-"

"But Rarity could use that spell of hers and magically fix the vase. Hay, Twilight could probably do that too."

"True, but either that or using glue would both take a lot of energy."

"And?"

"More specifically, repairing the vase would take more energy than breaking it would."

"...so?"

Pinkie sighed. "Look, the point is, it takes more energy to fix something than to break something. That's entropy."

"Oh! Why didn't you say that ten minutes ago?"

"You've only been in here for three minutes, Rainbow."

"Whatever." She pulled out a few bits. "Thanks for explaining that, I guess. Can I get one of those cupcakes to go?"

"Sure! I should get back to work. Feel free to stop by again some time if you have something that needs explaining!" Pinkie bounced behind the counter and pulled out a cupcake.

"You took three minutes to explain something that only needed a single sentence."

"Eh, potAYto tomAHto."

Rainbow Dash rolled her eyes as she took off.

Author's Note

Between this chapter and the last one, you should have a pretty good idea of what this fanfic will be like. Sometimes Pinkie will explain things in MLP, sometimes scientific concepts, sometimes things I'm learning about in school, because explaining things helps me understand them better too. Feel free to comment with suggestions for what Pinkie should explain next!