//------------------------------//
// The e-Quine 
// Story: Layers 
// by Trick Question 
//------------------------------//

The double doors to the castle library opened, and in trotted a tired-looking princess. Closing the doors behind her, Twilight Sparkle walked up to her marefriend and kissed her on the cheek.

"Hay, Twi. Thanks for coming so quickly," said Starlight Glimmer. The unicorn fussed with a light projector, focusing it so its rays covered the entire projection screen.

"I was afraid this was going to be about Sunburst again," mumbled Twilight. "Sorry."

"No, it's fine," said Starlight, frowning. "He's still visiting this weekend. Are you sure you're okay with this?"

Twilight shrugged. "He's your friend, and I'm the Princess of Friendship. What choice do I have?" Before Starlight could reply, she continued, "We'll talk about it later. What in Equestria has you up this late?"

Starlight cleared her throat and levitated a scroll over to Twilight. "It's a spell."

"Ah, of course," said Twilight, taking the scroll. "What does it do?"

"I don't know exactly, but it's recursive."

"How can a spell be recursive?" asked Twilight, eyes wide. "I mean, it can't cast itself..."

"That's exactly what it does!" said Starlight, suddenly grinning like mad. "It's a spell that continues casting indefinitely, as long as the electronic mana crystal it's cast upon remains intact. I call it an e-Quine."

"An e-Quine? Oh, an electronic self-replicating command," said Twilight. Her brow furrowed as she studied the spell. "This should be impossible, but it's so—"

"Amazing? Astounding?" Starlight clopped her forehooves together.

"I was going to say simple. It doesn't seem to do anything but self-perpetuate. This can't possibly work," said Twilight, but her voice quavered. "Starlight, this is your hornwriting. How on earth did you come up with the idea?"

"Star Swirl the Bearded was working on something similar but he decided against ever testing it. I guess he didn't see the point."

Twilight scratched her temple with a hoof. "I'm not sure I see it either. What could this possibly do? I mean, it should just sit there and do nothing, but then what would the mana be used for?"

"It's a self-casting spell intimately connected to our reality," said Starlight. "It requires a direct connection to the quantum field. That's where you come in."

"Ah, I see. It needs alicorn magic to activate," said Twilight, rolling her eyes. "Maybe that's why Star Swirl abandoned it. He thought better than to ask Princess Celestia to waste her time on a dangerous unknown."

Starlight's face fell. "Is that what you think of me? Always wasting your time with something dangerous?" She gritted her teeth. "I went to the trouble of preparing the electronic matrix of this mana crystal so that the spell can't possibly affect the outside world. Do you think I wouldn't take precautions when your wellbeing could be at stake?"

"What? No, Star! Look, I'm... I'm tired, honey," said Twilight, rubbing one foreleg with the other. "I have a lot on my mind, and the words came out wrong."

Starlight Glimmer breathed a sigh of relief. "Okay, I'm sorry. I'm overreacting too. I think this thing with Sunburst..."

"Yes, yes, we need to discuss it in the morning," said Twilight, a hoof over her face. "Look, I'll cast the spell, we'll do a little preliminary analysis, and then we can both go to bed."

"Together?" said Starlight, the end of the word rising in pitch.

"I'm sorry Star. I still have a migraine," said Twilight. "I want to, though. You know I do."

"I understand. Maybe tomorrow night."

Twilight Sparkle nodded and gave a weak smile. "I'd like that," she said, then her face hardened. "Okay, so you've prepared that crystal that's connected to the projector?"

Starlight nodded. "Yep." She stepped aside. "We'll be able to analyze the physical process through what the projector shows us, without contaminating the real world with the spell's effects."

Twilight stared at the scroll and her horn began to glow. Green flames began to lick at the edges of her eyes, and a flash—





Twilight Sparkle and Starlight Glimmer stood facing each other, right behind the projector. "What just happened?" asked Twilight.

"I don't remember. You were casting the spell, and there was a flash of light," said Starlight. "The spell didn't finish."

"Yes it did," said Twilight, pointing down at the crystal. "Look."

The mana crystal was glowing with Twilight's magenta aura and humming loudly.

"Dear Celestia. It's like perpetual motion," said Starlight. "I wonder if we could turn this into free energy?"

"I don't know what this is," said Twilight. "And I'm more than a little concerned about blacking out just now, even if it was only for a few seconds."

"Twi, look at the screen!" Starlight pointed to what appeared to be a sphere of stars encircling a tiny bluish dot.

Twilight Sparkle gasped. "Is that... the Celestial Sphere?" she said.

"Touch the mana crystal with your tee-kay, Twi. See if you can zoom in."

A few moments later, the stars swept past the screen and the dot grew to be larger. It was clearly the Earthen Sphere. The Moon was hovering overhead, and the Sun hung beneath on the opposite side.

"It's a map of the universe," said Twilight. "Holy Tartarus."

"Keep going!" urged Starlight.

Twilight slowly zoomed into the dark side of the Earthen Sphere, carefully aiming for Canterlot Mountain.

"I can see the silhouette of the Castle of Friendship," said Starlight, pointing.

"Fascinating. Let's see how detailed it gets." Moments later, the viewport was fixed on the Castle at night, and it looked as real as the real thing. "Starlight, why would this spell make a map of the Universe? There's nothing in it that does anything but cast itself. It has access to everything that exists through the quantum field, but it should be blocked from contacting the outside world."

"Who cares why it works! We can use this to examine the Heavens and Earth without leaving home!" said Starlight. "Think of the scientific knowledge!"

"I am, but..." The zoom entered the Castle of Friendship and stopped. In front of the library entrance was a black spherical cap. It looked as though the library were covered by a giant, opaque black sphere.

Starlight leaned back. "Huh. Now that's weird."

"This is so bizarre... Wait. I have an idea. SPIKE!" called Twilight.

Both mares watched as the projection showed a little Spike running up the stairs. "I'm coming Twilight!" came the sound from outside the library. Spike disappeared into the black sphere, then the library door opened.

"Are you okay?" asked Spike. "It sounded urgent."

"It was, but... you just confirmed my hypothesis, so that's all I needed," said Twilight. "Why are you up so late, anyway?"

Spike blushed. "Heh, lost track of time in a good comic book," he said. "I was already headed to bed."

"Twilight, this is more than a map," said Starlight, waiting until Spike closed the door to continue. "This is a spying device. Granted, it doesn't have audio, but still. Do you realize what this means?"

"It means it's too dangerous to use." On the projector, Spike headed down the hallway.

"It could save the world, Twilight. It'd be irresponsible not to use it," said Starlight. "But the technology needs to remain in our hooves."

"It's perfectly accurate except here in the library. How is it so accurate? There's no scrying magic or anything, it's just a spell that casts itself. It can't possibly be showing us what it's showing us. The projector should be showing us what's inside the spell, because the electronic matrix is blocking the outside world completely," said Twilight, shaking her head. "We have to figure this out before we go any further."

"Agreed. Wait! I want to try something. May I?"

"Be my guest."

Starlight Glimmer connected her aura to the crystal, which changed from Twilight's magenta to Starlight's turquoise. Spike appeared on the projector, walking backwards through the hallway. As he did, the spherical cap retreated into the library.

"Twilight, I can go backwards through time with this."

"That darkness is missing now. Let's see into the library," said Twilight.

Starlight moved the viewport into the library, and there stood both ponies behind a projector, while Spike stood just inside the doorway. The projector was showing a freeze-frame of what both ponies were looking at a minute previous. Inside the projection was another projection screen, fixed on the hallway. "Twi, this is impossible. Even if the crystal weren't blocking out the outside world, and even with the time difference, a scrying magic can't examine itself. The spell should be breaking from recursive feedback right now."

"Move it forward through time, double time," ordered Twilight. A black sphere appeared over the crystal and swelled in size, eventually turning the entire screen black. "It's a four-dimensional event horizon. The image won't let us see anything too close to the present moment near the mana crystal. What on earth..."

Starlight Glimmer gasped and staggered backwards. "Twilight."

"Yes? What is it?"

"Holy horse apples. It isn't possible, but it has to be."

"What isn't? Don't leave me in suspense! What in the world is it?"

"It can't be scrying magic, so that can't be our library..."

"I don't follow."

"Oxcam's razor, Twilight! It's not our library. It's something entirely inside the spell."

Twilight paused for a few moments as the wheels turned. "You don't... You can't be serious," she said, sitting down on the floor.

"Twilight, this spell is a simulation of the universe."

Twilight stood back up on shaky legs. Neither pony spoke for at least a minute. Then Starlight pulled the camera back in time and set it into normal-time motion once the library was visible, showing a delayed feed of the library. The projector image inside the projection was black, but after a few moments the Starlight Glimmer in the projection manipulated the simulation projector and it showed a view of the library on the projection screen within the projection screen—one with its own black projection. A few moments later, that projection lit up with a view of the library showing a black projection. Every few moments another screen lit up, showing a deeper layer of the simulation.

Twilight began breathing rapidly. "Dear Celestia, you're right. The e-Quine has to be a simulator. That explains how it can run with no parameters—it's using the boundary conditions of the universe to simulate the universe itself!"

"This... this is beyond crazy," said Starlight, with a laugh that matched. "And the universe we're simulating is simulating its own universe, ad infinitum. We have to turn this off now."

"Wait! We can't," said Twilight. "What if the ponies in all those simulations are real?"

Starlight's face paled. "But... no. They're identical to us. If there's no difference, they won't die. They'll just continue being us instead. You know how metaconsciousness works, Twi. You wrote the book on it. Literally."

"That's assuming there's no difference," said Twilight. "If we crush the mana crystal, countless universes would stop existing, wouldn't they?"

"It's identical in every way, or any differences would have been magnified to the nth degree by this point," Starlight pointed out. "As long as there's no difference between the universes, those ponies will continue existing in our universe."

Twilight shook her head. "I agree with your logic, but we can't afford to take any chances. We don't know enough about how this works yet."

Starlight sighed. "Then we have to leave it running. And I need to get some sleep... which is probably going to be impossible now."

"I'll be taking medicine to drag me under. Do you want some?" asked Twilight.

"Only if I can sleep beside you, since we'll both be passed out anyway. What do you say?" Starlight offered a sheepish smile.

Twilight bit at her lip, then nodded. "Deal."

"I'd best lock up the library."