The Real Reason

“Twilight,” Princess Celestia said.  “What did I just say?”

Twilight Sparkle blinked, and glanced at the books scattered about the reading desk between her and the princess, then at the odd collection of maps, instruments, and strange devices in the lobby of the royal library beyond, desperately seeking some cue.

“If you don’t know,” the princess said patiently, “then the correct answer is, ‘I don’t know.’”

“Well...  I...” Twilight hung her head.  “Don’t know,” she finished.

The princess smiled encouragingly.  “See? That wasn’t so hard.  Now let’s try a harder one: What’s on your mind?  It obviously isn't the theory of karmic conservation.”

That, Twilight remembered now, was what the princess had been talking about.  She blushed, and took an involuntary step back from the overly-perceptive princess.  Twilight felt sure that if she'd been having some typical schoolfilly daydream, Celestia would merely have brought her attention back to the present without pressing for details.  The princess had a knack for picking up on the things Twilight wanted to keep hidden.  Or perhaps she picked up on everything, and didn't bother mentioning the rest.

The possibility of lying never even occurred to the straightforward unicorn.  Dodging the question did, though it had never worked yet.  She lowered her head humbly and said, “It's really none of my business.”

“Oh,” Celestia said, “this should be good.” She cocked her head at Twilight and propped it up on one hoof, waiting.

When Celestia really listened to a pony, she put her whole body into it - leaning forward, tilting her ears towards them, stilling every other muscle in her body, and focusing on the speaker with an intense gaze that made them uncomfortably aware that the goddess who moved the sun was hanging on their every word.  That usually shut them up pretty quickly.  If, on the other hand, they were trying not to speak, there was little hope for them; it was impossible to out-wait Celestia, and would be a kind of sacrilege to look away first.  There were few ponies who could stand the strain of such listening, and Twilight Sparkle was not one of them.

“I was thinking about Luna,” she confessed.  She looked to Celestia for some reaction, but the princess merely nodded for her to continue.

Eventually, Twilight did.  “All those years on the moon...  Centuries.  There’s no sound there.  No color.  No smell.  Nothing but dust and rocks.  It would drive a pony insane.”

“Go on.”

“Well...  it’s just...” Twilight stopped, and this time seemed to have run out of words for good.

“How could I?”

Twilight looked away and nodded.

Celestia smiled.  “I thought you’d never ask.”