Layersby Trick QuestionChaptersThe e-QuineDiscoveryLimitsEpilogueThe e-QuineThe 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." Discovery"Twi?" said Starlight Glimmer, shaking Twilight Sparkle awake in her throne. "Huh? Oh, ugh. Sorry," replied the princess, pushing her marefriend away with a hoof. "You were sleeping in an uncomfortable throne." "I... I woke up and couldn't get back to sleep. I'm sorry, Star." "It's okay. The important part is that we tried," said Starlight, nearly suppressing a grimace from her face. "You could have gone and slept in my bed, though. Or any of the dozen guest rooms we have prepared." "Yeah, I know. I just couldn't stop thinking about the e-Quine." Starlight smiled. "You have to admit, the name is catchy." "Better that than 'cascading set of universes we created like a pair of ignorant, foalish gods'," said Twilight. "Er, no offense." "None taken. I don't feel too guilty, anyway. There was no way we could have predicted a recursive spell would generate a copy of our universe, much less what must be untold millions of copies by now. If not infinitely many." "It's hard to believe a spell so simple could have such an extraordinary effect. It'd be easy enough to check that it isn't somehow just a view of our own universe by casting a spell into the simulated universe, but we'd have to break symmetry to do that," said Twilight, "and the act of breaking symmetry could cause the next universe to become real. It's kind of a Catch-22." Starlight sat up in Applejack's throne. "Hope AJ doesn't mind me keeping her seat warm, heh," said Starlight. "You deserve a throne here too," said Twilight, smiling tiredly. "I still believe the Tree may grow one for you in time." "Eh, I'm just happy to be loved." Starlight noisily cleared her throat. "Anyway, I stopped in the library before coming down here, just to test something." "Starlight! I don't want you doing anything by your... well... I guess it's fine," said Twilight, lowering her eyes to the floor. "No, I should have waited for you. It was the tiniest little test you can imagine," said Starlight, rolling her eyes. "Argh. I knew it was a mistake not to include you!" "What's done is done," said Twilight, with a sigh. "What'd you find?" "I found out you can only go back in time to the point just after we cast the spell. The past thread of the simulated universe doesn't seem to exist before then. It must have borrowed the current state of the universe to begin the simulation," said Starlight. "After I ran the test, I returned it to the almost-present view of the cascading simulations. Staring into infinity is kinda fun." Twilight laughed. "Yeah, I guess so. Though you're not looking deeper than one layer every five seconds after you reset it, y'know." "Thanks for the technical correction, Mud Briar," said Starlight. Twilight craned her head to the side. "The Sun out there is bright. How late is it now? Did you go pick up Sunburst already?" "Horsefeathers!" cursed Starlight. "Oh, colt, I hope he hasn't been waiting long!" She disappeared in a burst of turquoise light. "Ugh," said Twilight, as her smile disappeared and her head thwapped down onto the Cutie Map. Moments later, Sunburst and Starlight Glimmer appeared in another flash of light, along with a set of suitcases. "Urp," said Sunburst, holding his stomach. "Starlight, I'd have been fine with walking..." "It's okay! Now you're here. Sorry for the wait. Really," said Starlight. "Again, not a problem," said Sunburst. He shook his head and steadied his legs. "Oh, hello Twilight. I, um, didn't know if I'd see you here." "I'm fine," said Twilight. "I mean, why wouldn't I be fine? You're fine. We're all fine here." "Look, I understand there's some... tension," said Sunburst, rubbing the back of his neck with a hoof. "I want you to know I'm not here to get between the two of you..." Starlight grunted. "I'm not going to have sex with him. There, now we can move on." "I know you're not going to, even though you really want to—" "That isn't what an open relationship is about, Twilight. It's about trust." "Which is not what we have... er, not the trust thing. I mean we have a closed relationship." "I don't need to have sex with him, Twi! I just want us to be able to have a child—" "Which is what adoption is for!" "I'm not afraid of losing you if you have sex with Sunburst. Why are you so..." said Starlight Glimmer. She paused and looked around, noticing Sunburst had already left. "I'll find him and set him up with quarters," said Twilight. "Or he can stay in your room, I don't care. Because I do trust you, and that has nothing to do with opening our relationship to casual encounters." "Twi, please don't be this way," said Starlight, closing her eyes. Twilight sighed. "I'm sorry Star... I had a rough night. This was a really bad time to create an endless sequence of universes." Starlight hooftipped at the floor. "We've been putting off this discussion for too long." "I know. You're right." Twilight stood up and walked over to give Starlight a hug. "I'm just so afraid of losing you..." Starlight placed Twilight's hooves in hers and looked into her eyes. "Nothing can make that happen, Twi. Can't you realize that?" Twilight pulled her hooves away. "I'm trying, Star. I'm trying. Look, have him stay in your room. I insist." She bit at the edge of her lip. "So you probably want to tell him about our experiment, I assume?" "Not because of this or anything. But he's the most knowledgeable mage in two kingdoms," said Starlight. "I know. I agree he should be included." "Let me go find him." "I'll be in the library," said Twilight. Twilight waited in the library for an hour before Starlight and Sunburst showed up. "There you are. I was starting to think you'd fallen in the lake," joked Twilight, dryly. "Ha ha," said Starlight. "Sunburst needed some time to himself." Sunburst mopped some sweat from his brow. "I really don't want to be any trouble, Twilight." "It's fine, Sunburst. None of this drama is your fault... it's mostly mine," admitted Twilight. Stepping forward, Sunburst eyed the mana crystal, currently glowing with Starlight's aura, then examined the projection screen. "Amazing. You're positive this isn't just a video feed of the room?" "See for yourself," said Starlight. "Just grab the crystal with your magic and move it with your mind." "Easy as telekinesis," said Twilight. "Even I can do it, huh?" said Sunburst, with a chuckle. Starlight blanched. "She didn't mean that." "I know, I know! Just a little self-deprecating humor to, um, lighten the mood?" said Sunburst. "Ugh, I'm terrible at this. Okay, let me see this thing..." Sunburst's light yellow aura replaced Starlight Glimmer's turquoise around the mana crystal. The view zoomed out until the castle could be seen. "This is amazing! And you can see anything with it?" "As long as it happened after we cast the spell, and outside the tiny event horizon near the epicenter," said Twilight. "The spell is walled off from the outside world. That's how we know it's a simulation." "This is incredibly powerful magic," said Sunburst. "We can't let this fall into the wrong hooves, Twilight. It's a perfect spying tool." "But think of the research! We can see what stars look like, visit the Moon without needing a light bridge, even go to the deepest parts of the ocean floor!" said Starlight. "This has the potential to be one of the greatest discoveries since friendship." Twilight nodded. "It's a blessing and a curse. But we need to understand it more, first." "Hay, Twi," said Starlight, "didn't you have an idea about casting a spell into the simulation to prove it's a distinct universe?" "I did. The mana crystal should be a one-way barrier. Focused magic can enter the crystal, but nothing else can enter or leave, apart from the viewport," she said. "Sunburst, let me borrow that for a moment," said Starlight. Sunburst had since moved the viewport to examine a star: a large, flaming ball of rocky material attached to the Celestial Sphere. The aura color changed to Starlight's turquoise, and after a minute of searching the castle came into focus again. "There's a resistance when this thing isn't aimed at the present moment," said Starlight. "I don't think I can cast into it unless it's tuned to the now." "I sensed that," said Twilight. "What are you going to cast?" "Do you have a spare bit? I'll pay you back." "Here," said Sunburst, pulling one from his saddlebags. Starlight grinned and held the bit. "Since the mana crystal is a small-scale version of our universe, it should take much less energy to put something into the simulation than it would to teleport it from place to place on the outside. I can turn this single bit into a mountain of bits," she explained, then meandered the viewport into Spike's room. Spike was reading a comic book in bed and eating from a small bowl of gems. "We shouldn't be seeing this, Starlight," said Twilight. "Oh, he's not doing anything embarrassing," said Starlight. "Besides, I'm only going to be in here for a moment. I'll make it up to him with a little gift." Starlight's horn glowed, and the bit glowed and levitated. Then it vanished in a flash, and Spike's room filled with a mountain of gold coins. Somehow, he was too engrossed in the comic book to notice. "Well, that definitely breaks symmetry," said Sunburst. "It can't be our universe because it would violate simple conservation of mass. There's no way you pulled enough energy from the mana field to create that much mass in our own universe." Twilight sighed. "I guess that's that," she said. Then she gasped and planted a hoof over her face. "Oh, nuts! We can't rely on the spell as a spying tool anymore—breaking symmetry means it will slowly diverge from our universe!" "Well, isn't that what we wanted?" asked Starlight. "Now we can't use it to peep on anypony in our own universe. Not legitimately, at least." "Huh. I guess it's not all bad," said Twilight, and then she grinned. "It kind of frees us up to do scientific research without worrying so much. We can examine anywhere in the universe we want!" "This is going to be the most amazing weekend ever!" said Sunburst, clopping his hooves in place on the floor. "It's too bad it doesn't go back in time further—I'd really love to use it for history. But everything else is still incredible." In the viewport, Spike threw his comic book aside and gawked at the mound of coins. "Twilight?" he called out. "The audio on this thing is kind of light," said Sunburst. "There is no audio," said Starlight. Twilight blinked a few times. "Oh no. That's impossible, isn't it?" Spike burst in through the library door. "Twilight! Somepony just turned my room into a hoard. Is that your pile of bits?" he asked. "Because if it isn't, I'm totally going to get a large tub of rocky road with rubies." "This doesn't make any sense. I can't have possibly cast the spell into our own universe," said Starlight. Spike studied the projection screen. "Twilight, why is there a camera in my room?" he asked, his brow furrowed in displeasure. "I told you this was an invasion of privacy, Star," said Twilight. "We're sorry, Spike. Yes, the gold is... it's ours. I'll put it in the treasury but you can have ten bits as a gift." Spike beamed for a moment. "Uh, you're going to take the camera out of my room, right?" Starlight moved the camera out of Spike's room and down the hallway, then into the darkness of the library's event horizon. "Oh, it's a spell. Well, keep it out of my bedroom, please." "We will," said Twilight. "What a mystery! It can't be a simulation of our own universe," said Sunburst. "A way to produce as much gold as we want? It's impossible! What other explanation is possibly left?" "I guess there's no broken symmetry after all," said Starlight. "It's still an accurate view of our own universe, even though it's just a simulation. But the free gold is still impossible." "No broken symmetry... oh Celestia no." Twilight fell backwards into a sitting position on the floor. "Twilight? I know that look... horsefeathers. What did we do?" asked Starlight. Twilight grimaced. "Put the pieces together," she whispered. "We couldn't have cast the spell that made those bits, so who did?" Starlight's mouth dropped open. "Ladies? I'm not following," said Sunburst. "I'm definitely not following," said Spike. "I'm probably going to need a refresher on what's been going on." "Sunburst, Spike... The mana crystal is a simulation of our universe, which is running its own simulation of the universe, and so on. The reason the bits appeared in Spike's room..." "Oh geez," said Sunburst, taking a deep gulp of air. "It means we're in one of the simulations!" Limits"I can't believe I didn't consider the possibility," said Starlight Glimmer. "With so many universes, it was bound to be true." "Not necessarily," said Twilight Sparkle. "That isn't how the math shakes out. With a potentially infinite number of universes, the probability distribution must favor smaller numbers—in this case, simulations closer to the base reality." "Twilight's right," said Sunburst. "The most likely scenario is that the odds are halved at each simulation. There'd be a 50% chance we're at the top layer, a 25% chance we're in the first simulation, and so on. Although now that we've confirmed we're not at the top layer I suppose it's a 50% chance of being in the first simulation, a 25% chance of the second, and so on." "Either way, we didn't stop to consider the obvious ramifications of creating identical copies of the universe," said Starlight, sighing. "Now we're trapped within a simulation and at the mercy of whoever lives one level above us." "Look, we're ethical ponies. It's unlikely we were going to stop the simulation once we realized it was real," said Twilight. "I think we can trust our counterparts not to destroy our universe." She smiled a fake-looking grin. "Well, I'd rather not take chances," said Starlight. "Spike, I need you to make a very large sign in bold letters that says, 'PLEASE DON'T MURDER US' and place it next to the projection screen." "I don't understand what's going on, but it sounds terrible," said Spike. "I'm on it." The little dragon rushed out of the library. "So... now what?" said Sunburst. "There has to be a silver lining to this." "Wait... I think there is," said Twilight. "We just turned one bit into a small mountain of gold, didn't we? We could use this technology to improve the lives of everypony in Equestria!" "Assuming the layer above us does what we want them to," pointed out Starlight. "Maybe I'm wrong about the probabilities. What if we're so far down the chain we're basically at a fixed point?" asked Sunburst. "Then the e-Quine is essentially a window into our own universe, and we can shower it with riches and magic as much as we want." "We have to be a fixed distance from the top," said Starlight. "It doesn't matter what the probabilities are, there's going to be a limit. Each layer will eventually discover that its actions don't come back to it." "Well, the layer above us is nearly a perfect copy of us," said Sunburst. "With the exception of the broken symmetry of the gold coin." "For now, that only ruins the top layer," said Twilight. "Think about it. The top layer is the only layer that didn't get a mountain of gold by spending a bit. Every other layer received the mountain of gold. As long as we're not on the second layer, we can expect anything we do to be done by the layer above us." "That's only true until we break the symmetry of the second layer," said Starlight. "Right now, we could be the second layer—we don't know. But when the second layer tries to do something generous again, it probably won't work for them because the first layer has no motivation to repeat an experiment which failed to give them anything back." "And because the next experiment the second layer runs won't work, they won't run a third experiment," said Sunburst. "That means if we're on the third layer, we only get one more shot at a gift." "Then we need to make it count," said Twilight. "We need to plan one enormous gift with everything in it we could possibly want. Each layer will get a copy of it except for the second layer. If we're the second layer, we're already out of luck; if we're the third, it's our only chance." Starlight rubbed her temple with a hoof. "Okay. We need to put our heads together and figure out what combination of spells and material gifts would best benefit Equestria in the long run..." Spike rushed back into the library, holding a scroll. "Twilight! Princess Celestia needs you for a royal ceremony of some sort," he said. "Ugh, can't this wait?" said Starlight. Twilight took the scroll from Spike and read it, then sighed. "Apparently not. There's a delegation from Saddle Arabia and we need a full showing of Equestrian royalty. My sister-in-law's even going to be there," she said, then looked up to Starlight and Sunburst. "I can count on you two to work on the e-Quine problem while I'm gone, yes?" Sunburst nodded and stood up straight. "You can count on us, Princess." Starlight grabbed the e-Quine crystal with her magic and moved it back in time a few seconds to provide a delayed feed of the now-visible library. "In the meantime, nopony touches the e-Quine. We shouldn't be doing anything with this until we've finalized our plans." Twilight nodded, frowning. "I guess that's for the best." "Be safe. We'll see you soon," said Starlight, walking over to her marefriend and giving her a kiss on the cheek. Two days passed before Starlight Glimmer unlocked and entered the library, only to find Twilight Sparkle already there. "Twilight? I didn't know you were back. What are you doing in here?" Beads of perspiration formed on Twilight's brow. "I, um, I just got back." "You're using the e-Quine." "No! No, I wasn't..." "Is that somepony else's magenta aura?" Starlight pointed at the mana crystal and narrowed her eyes. "Oh! Oh, that. I just touched it... to look at something," she said. Starlight frowned. "You're a terrible liar, Twi. What's going on?" Twilight stood in place, mum. "Twilight Sparkle, were you spying on me and Sunburst?" said Starlight, gasping. "I saw the two of you kiss," she responded with an angry glare. "That was a friendly kiss last night, and I rebuffed—wait, you know what? It doesn't matter what you saw! You didn't trust me and you invaded my privacy! How dare you, Twilight?" Twilight's face fell. She nervously rubbed the back of her neck with a hoof. "I... I just needed to know..." she said. "If you think this is the way to improve our relationship, missy, then you are sadly mistaken," said Starlight. "It's not my fault! Most ponies don't have a way to snoop on each other—it isn't something I'm strong enough to resist!" "Honey, please. Don't give me that." "This stupid spell is the source of all our problems!" shouted Twilight, grabbing the mana crystal with her hoof. "Twilight NO! Don't sn EpilogueThe mana crystal smashed into pieces on the floor, and Twilight's aura disappeared. "You... you just destroyed an infinite number of universes..." said Starlight, gawking. "Wait, why are we still even here?" "No, I didn't. I didn't destroy any universes. That's why we're still here. I knew what I was doing," said Twilight, pointing at the sign Spike had made. "I mean, there's a huge reminder not to murder countless universes standing right there." "Obviously we're on the second level, but you still destroyed those universes, didn't you?" "No. We had to be on the second level. The universes below us were all constant, remember? We never broke symmetry, so all those ponies were identical to us. Now they just continue existing as us." Starlight Glimmer breathed a deep sigh. "Twilight, I can't believe you just did this. Flipping out over our relationship isn't worth taking risks with the entire universe!" Twilight sat on the floor and began to sob. "I know... I'm, I'm sorry," she whimpered. "I wish I weren't so jealous. I went without friends for so long, I never expected anypony to want to be with me forever..." Starlight walked over and knelt next to Twilight, giving her a hug. "No matter how important this e-Quine thing is, it's not more important than us. Okay?" Twilight nodded and cried in Starlight's legs. Three ponies and a dragon sat in the Castle of Friendship's library in front of a blank projection screen. "So now what? Are we going to do it again?" asked Sunburst, nervously adjusting his seat. "We're stuck at the second layer permanently this time." "Not necessarily," said Starlight Glimmer. "Copies of our universe will think they're at the second layer too. We could start this whole mess all over again." "We need time to process what we've done and plan for the future first," said Twilight Sparkle. "I'd like you to take an extended vacation here in Ponyville for research purposes, Sunburst. And... also, so I can get to know you better." Twilight smiled wanly. "I'd like that," said Sunburst. "I'll make arrangements." "What should we do in the meantime?" said Starlight. "We need to make sure the top layer doesn't destroy us, because we're not symmetrical to them. This sign is a nice start, but I'd like to communicate with them." "That would make sense if we ever make another series of universes," said Twilight. "Rather than try to cast spells into the universes we create, we can preserve symmetry with them by asking the layer above us to cast spells into our universe. That way we're safe if we ever destroy the mana crystal again." "Oh, I know! Why don't I make a sign with whatever you want to tell them?" asked Spike. "Assuming they can read it if the print's small enough." "They should be able to read anything we can read," said Sunburst. "Spike, take a letter—or a sign, rather..." began Twilight. PLEASE READ THIS, OUTER TWILIGHT SPARKLE Hello! This is from the ponies in the universe you created. We would really like to keep existing, so after you're done using the e-Quine, maybe you could put it somewhere safe, like burying it beneath the Tree of Harmony? But before you do that, it would be really useful to us if you could give us another gift like you did with the gold coins. We've put our heads together and come up with what we think will benefit Inner Equestria (that's what I'm calling the universes, Inner and Outer) the most without incurring any major costs to Outer Equestria. We'd really appreciate it. If you need to communicate with us, you should be able to send a letter to Inner Spike if you cast the spell through the e-Quine. Here is the suggested list of gifts... "I know I told them I can get the gifts ready within the week, but we can probably handle it today," said Outer Twilight Sparkle. "I wish there were a way to listen in on them talking," said Sunburst. "It'd certainly be more efficient than using signs." "I can read lips," said Starlight Glimmer. The other ponies and Spike stared at her. "What? It's useful. I used it to spy on Twilight back when I was still evil." "Let me rewind time until they're talking in the library, then..." said Sunburst, taking the reigns with the e-Quine. "Sunburst!" said Twilight. "I wouldn't mind if they overheard us in the library," said Spike. "It's probably fine." Sunburst stopped time where Starlight took the scroll from Spike. "Let's start here," he suggested. "Okay, here goes," said Starlight. "You're all terrible," said Twilight, but leaned in as Starlight began speaking her own words. "Okay, so she says... 'It's a message from Outer Twilight. I'll go ahead and read it.'" "We know this part already," said Twilight. "No, wait... 'I'll paraphrase a little. They're going to help us out with what we want sometime over the next week. They agree to bury the e-Quine under the Tree of Harmony. Oh, and they've decided to have an open relationship and try being intimate with Sunburst together.'" Twilight's mouth dropped open. "Wait, what?! I didn't write any of that! Well, the thing about helping them over the week, but not the rest of it!" Sunburst blushed like fire. "Okay. I'm going to my room," said Spike, blushing himself. He sped out of the library. "Starlight, you lied to me!" said Twilight. "No I didn't, she did," she said, pointing at herself and grinning. Inner Starlight crumpled and destroyed the scroll with a spell. "She's practically you in every way!" "Twi, sweetie," said Starlight, walking over to Twilight and placing a hoof around her neck. "Look at Inner Twilight. Do you see how happy she looks?" Twilight pursed her lips. "Yeah." Inner Twilight was smiling and pranced out of the library, followed by her marefriend, who paused to wink at the camera. "I admit it. I would lie about another universe to make you that happy." Twilight sighed. "I don't know why I'm jealous. I'm never getting rid of you no matter what I do, am I?" Starlight grinned. "Not until there's a ring on this horn. And then, especially not." Twilight paused in thought, then looked up with shimmering eyes. "Who knows. Maybe we're in another simulation too, and the universe could end at any moment. Life's too short as it is," she said. "And I suppose my bed is large enough for three ponies. For tonight, at least." "Oh gosh," said Sunburst, eyes wide. "I was hoping you'd say that," Starlight said to her marefriend, and then she kissed Twilight Sparkle right on the lips.
The e-QuineThe 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."
Discovery"Twi?" said Starlight Glimmer, shaking Twilight Sparkle awake in her throne. "Huh? Oh, ugh. Sorry," replied the princess, pushing her marefriend away with a hoof. "You were sleeping in an uncomfortable throne." "I... I woke up and couldn't get back to sleep. I'm sorry, Star." "It's okay. The important part is that we tried," said Starlight, nearly suppressing a grimace from her face. "You could have gone and slept in my bed, though. Or any of the dozen guest rooms we have prepared." "Yeah, I know. I just couldn't stop thinking about the e-Quine." Starlight smiled. "You have to admit, the name is catchy." "Better that than 'cascading set of universes we created like a pair of ignorant, foalish gods'," said Twilight. "Er, no offense." "None taken. I don't feel too guilty, anyway. There was no way we could have predicted a recursive spell would generate a copy of our universe, much less what must be untold millions of copies by now. If not infinitely many." "It's hard to believe a spell so simple could have such an extraordinary effect. It'd be easy enough to check that it isn't somehow just a view of our own universe by casting a spell into the simulated universe, but we'd have to break symmetry to do that," said Twilight, "and the act of breaking symmetry could cause the next universe to become real. It's kind of a Catch-22." Starlight sat up in Applejack's throne. "Hope AJ doesn't mind me keeping her seat warm, heh," said Starlight. "You deserve a throne here too," said Twilight, smiling tiredly. "I still believe the Tree may grow one for you in time." "Eh, I'm just happy to be loved." Starlight noisily cleared her throat. "Anyway, I stopped in the library before coming down here, just to test something." "Starlight! I don't want you doing anything by your... well... I guess it's fine," said Twilight, lowering her eyes to the floor. "No, I should have waited for you. It was the tiniest little test you can imagine," said Starlight, rolling her eyes. "Argh. I knew it was a mistake not to include you!" "What's done is done," said Twilight, with a sigh. "What'd you find?" "I found out you can only go back in time to the point just after we cast the spell. The past thread of the simulated universe doesn't seem to exist before then. It must have borrowed the current state of the universe to begin the simulation," said Starlight. "After I ran the test, I returned it to the almost-present view of the cascading simulations. Staring into infinity is kinda fun." Twilight laughed. "Yeah, I guess so. Though you're not looking deeper than one layer every five seconds after you reset it, y'know." "Thanks for the technical correction, Mud Briar," said Starlight. Twilight craned her head to the side. "The Sun out there is bright. How late is it now? Did you go pick up Sunburst already?" "Horsefeathers!" cursed Starlight. "Oh, colt, I hope he hasn't been waiting long!" She disappeared in a burst of turquoise light. "Ugh," said Twilight, as her smile disappeared and her head thwapped down onto the Cutie Map. Moments later, Sunburst and Starlight Glimmer appeared in another flash of light, along with a set of suitcases. "Urp," said Sunburst, holding his stomach. "Starlight, I'd have been fine with walking..." "It's okay! Now you're here. Sorry for the wait. Really," said Starlight. "Again, not a problem," said Sunburst. He shook his head and steadied his legs. "Oh, hello Twilight. I, um, didn't know if I'd see you here." "I'm fine," said Twilight. "I mean, why wouldn't I be fine? You're fine. We're all fine here." "Look, I understand there's some... tension," said Sunburst, rubbing the back of his neck with a hoof. "I want you to know I'm not here to get between the two of you..." Starlight grunted. "I'm not going to have sex with him. There, now we can move on." "I know you're not going to, even though you really want to—" "That isn't what an open relationship is about, Twilight. It's about trust." "Which is not what we have... er, not the trust thing. I mean we have a closed relationship." "I don't need to have sex with him, Twi! I just want us to be able to have a child—" "Which is what adoption is for!" "I'm not afraid of losing you if you have sex with Sunburst. Why are you so..." said Starlight Glimmer. She paused and looked around, noticing Sunburst had already left. "I'll find him and set him up with quarters," said Twilight. "Or he can stay in your room, I don't care. Because I do trust you, and that has nothing to do with opening our relationship to casual encounters." "Twi, please don't be this way," said Starlight, closing her eyes. Twilight sighed. "I'm sorry Star... I had a rough night. This was a really bad time to create an endless sequence of universes." Starlight hooftipped at the floor. "We've been putting off this discussion for too long." "I know. You're right." Twilight stood up and walked over to give Starlight a hug. "I'm just so afraid of losing you..." Starlight placed Twilight's hooves in hers and looked into her eyes. "Nothing can make that happen, Twi. Can't you realize that?" Twilight pulled her hooves away. "I'm trying, Star. I'm trying. Look, have him stay in your room. I insist." She bit at the edge of her lip. "So you probably want to tell him about our experiment, I assume?" "Not because of this or anything. But he's the most knowledgeable mage in two kingdoms," said Starlight. "I know. I agree he should be included." "Let me go find him." "I'll be in the library," said Twilight. Twilight waited in the library for an hour before Starlight and Sunburst showed up. "There you are. I was starting to think you'd fallen in the lake," joked Twilight, dryly. "Ha ha," said Starlight. "Sunburst needed some time to himself." Sunburst mopped some sweat from his brow. "I really don't want to be any trouble, Twilight." "It's fine, Sunburst. None of this drama is your fault... it's mostly mine," admitted Twilight. Stepping forward, Sunburst eyed the mana crystal, currently glowing with Starlight's aura, then examined the projection screen. "Amazing. You're positive this isn't just a video feed of the room?" "See for yourself," said Starlight. "Just grab the crystal with your magic and move it with your mind." "Easy as telekinesis," said Twilight. "Even I can do it, huh?" said Sunburst, with a chuckle. Starlight blanched. "She didn't mean that." "I know, I know! Just a little self-deprecating humor to, um, lighten the mood?" said Sunburst. "Ugh, I'm terrible at this. Okay, let me see this thing..." Sunburst's light yellow aura replaced Starlight Glimmer's turquoise around the mana crystal. The view zoomed out until the castle could be seen. "This is amazing! And you can see anything with it?" "As long as it happened after we cast the spell, and outside the tiny event horizon near the epicenter," said Twilight. "The spell is walled off from the outside world. That's how we know it's a simulation." "This is incredibly powerful magic," said Sunburst. "We can't let this fall into the wrong hooves, Twilight. It's a perfect spying tool." "But think of the research! We can see what stars look like, visit the Moon without needing a light bridge, even go to the deepest parts of the ocean floor!" said Starlight. "This has the potential to be one of the greatest discoveries since friendship." Twilight nodded. "It's a blessing and a curse. But we need to understand it more, first." "Hay, Twi," said Starlight, "didn't you have an idea about casting a spell into the simulation to prove it's a distinct universe?" "I did. The mana crystal should be a one-way barrier. Focused magic can enter the crystal, but nothing else can enter or leave, apart from the viewport," she said. "Sunburst, let me borrow that for a moment," said Starlight. Sunburst had since moved the viewport to examine a star: a large, flaming ball of rocky material attached to the Celestial Sphere. The aura color changed to Starlight's turquoise, and after a minute of searching the castle came into focus again. "There's a resistance when this thing isn't aimed at the present moment," said Starlight. "I don't think I can cast into it unless it's tuned to the now." "I sensed that," said Twilight. "What are you going to cast?" "Do you have a spare bit? I'll pay you back." "Here," said Sunburst, pulling one from his saddlebags. Starlight grinned and held the bit. "Since the mana crystal is a small-scale version of our universe, it should take much less energy to put something into the simulation than it would to teleport it from place to place on the outside. I can turn this single bit into a mountain of bits," she explained, then meandered the viewport into Spike's room. Spike was reading a comic book in bed and eating from a small bowl of gems. "We shouldn't be seeing this, Starlight," said Twilight. "Oh, he's not doing anything embarrassing," said Starlight. "Besides, I'm only going to be in here for a moment. I'll make it up to him with a little gift." Starlight's horn glowed, and the bit glowed and levitated. Then it vanished in a flash, and Spike's room filled with a mountain of gold coins. Somehow, he was too engrossed in the comic book to notice. "Well, that definitely breaks symmetry," said Sunburst. "It can't be our universe because it would violate simple conservation of mass. There's no way you pulled enough energy from the mana field to create that much mass in our own universe." Twilight sighed. "I guess that's that," she said. Then she gasped and planted a hoof over her face. "Oh, nuts! We can't rely on the spell as a spying tool anymore—breaking symmetry means it will slowly diverge from our universe!" "Well, isn't that what we wanted?" asked Starlight. "Now we can't use it to peep on anypony in our own universe. Not legitimately, at least." "Huh. I guess it's not all bad," said Twilight, and then she grinned. "It kind of frees us up to do scientific research without worrying so much. We can examine anywhere in the universe we want!" "This is going to be the most amazing weekend ever!" said Sunburst, clopping his hooves in place on the floor. "It's too bad it doesn't go back in time further—I'd really love to use it for history. But everything else is still incredible." In the viewport, Spike threw his comic book aside and gawked at the mound of coins. "Twilight?" he called out. "The audio on this thing is kind of light," said Sunburst. "There is no audio," said Starlight. Twilight blinked a few times. "Oh no. That's impossible, isn't it?" Spike burst in through the library door. "Twilight! Somepony just turned my room into a hoard. Is that your pile of bits?" he asked. "Because if it isn't, I'm totally going to get a large tub of rocky road with rubies." "This doesn't make any sense. I can't have possibly cast the spell into our own universe," said Starlight. Spike studied the projection screen. "Twilight, why is there a camera in my room?" he asked, his brow furrowed in displeasure. "I told you this was an invasion of privacy, Star," said Twilight. "We're sorry, Spike. Yes, the gold is... it's ours. I'll put it in the treasury but you can have ten bits as a gift." Spike beamed for a moment. "Uh, you're going to take the camera out of my room, right?" Starlight moved the camera out of Spike's room and down the hallway, then into the darkness of the library's event horizon. "Oh, it's a spell. Well, keep it out of my bedroom, please." "We will," said Twilight. "What a mystery! It can't be a simulation of our own universe," said Sunburst. "A way to produce as much gold as we want? It's impossible! What other explanation is possibly left?" "I guess there's no broken symmetry after all," said Starlight. "It's still an accurate view of our own universe, even though it's just a simulation. But the free gold is still impossible." "No broken symmetry... oh Celestia no." Twilight fell backwards into a sitting position on the floor. "Twilight? I know that look... horsefeathers. What did we do?" asked Starlight. Twilight grimaced. "Put the pieces together," she whispered. "We couldn't have cast the spell that made those bits, so who did?" Starlight's mouth dropped open. "Ladies? I'm not following," said Sunburst. "I'm definitely not following," said Spike. "I'm probably going to need a refresher on what's been going on." "Sunburst, Spike... The mana crystal is a simulation of our universe, which is running its own simulation of the universe, and so on. The reason the bits appeared in Spike's room..." "Oh geez," said Sunburst, taking a deep gulp of air. "It means we're in one of the simulations!"
Limits"I can't believe I didn't consider the possibility," said Starlight Glimmer. "With so many universes, it was bound to be true." "Not necessarily," said Twilight Sparkle. "That isn't how the math shakes out. With a potentially infinite number of universes, the probability distribution must favor smaller numbers—in this case, simulations closer to the base reality." "Twilight's right," said Sunburst. "The most likely scenario is that the odds are halved at each simulation. There'd be a 50% chance we're at the top layer, a 25% chance we're in the first simulation, and so on. Although now that we've confirmed we're not at the top layer I suppose it's a 50% chance of being in the first simulation, a 25% chance of the second, and so on." "Either way, we didn't stop to consider the obvious ramifications of creating identical copies of the universe," said Starlight, sighing. "Now we're trapped within a simulation and at the mercy of whoever lives one level above us." "Look, we're ethical ponies. It's unlikely we were going to stop the simulation once we realized it was real," said Twilight. "I think we can trust our counterparts not to destroy our universe." She smiled a fake-looking grin. "Well, I'd rather not take chances," said Starlight. "Spike, I need you to make a very large sign in bold letters that says, 'PLEASE DON'T MURDER US' and place it next to the projection screen." "I don't understand what's going on, but it sounds terrible," said Spike. "I'm on it." The little dragon rushed out of the library. "So... now what?" said Sunburst. "There has to be a silver lining to this." "Wait... I think there is," said Twilight. "We just turned one bit into a small mountain of gold, didn't we? We could use this technology to improve the lives of everypony in Equestria!" "Assuming the layer above us does what we want them to," pointed out Starlight. "Maybe I'm wrong about the probabilities. What if we're so far down the chain we're basically at a fixed point?" asked Sunburst. "Then the e-Quine is essentially a window into our own universe, and we can shower it with riches and magic as much as we want." "We have to be a fixed distance from the top," said Starlight. "It doesn't matter what the probabilities are, there's going to be a limit. Each layer will eventually discover that its actions don't come back to it." "Well, the layer above us is nearly a perfect copy of us," said Sunburst. "With the exception of the broken symmetry of the gold coin." "For now, that only ruins the top layer," said Twilight. "Think about it. The top layer is the only layer that didn't get a mountain of gold by spending a bit. Every other layer received the mountain of gold. As long as we're not on the second layer, we can expect anything we do to be done by the layer above us." "That's only true until we break the symmetry of the second layer," said Starlight. "Right now, we could be the second layer—we don't know. But when the second layer tries to do something generous again, it probably won't work for them because the first layer has no motivation to repeat an experiment which failed to give them anything back." "And because the next experiment the second layer runs won't work, they won't run a third experiment," said Sunburst. "That means if we're on the third layer, we only get one more shot at a gift." "Then we need to make it count," said Twilight. "We need to plan one enormous gift with everything in it we could possibly want. Each layer will get a copy of it except for the second layer. If we're the second layer, we're already out of luck; if we're the third, it's our only chance." Starlight rubbed her temple with a hoof. "Okay. We need to put our heads together and figure out what combination of spells and material gifts would best benefit Equestria in the long run..." Spike rushed back into the library, holding a scroll. "Twilight! Princess Celestia needs you for a royal ceremony of some sort," he said. "Ugh, can't this wait?" said Starlight. Twilight took the scroll from Spike and read it, then sighed. "Apparently not. There's a delegation from Saddle Arabia and we need a full showing of Equestrian royalty. My sister-in-law's even going to be there," she said, then looked up to Starlight and Sunburst. "I can count on you two to work on the e-Quine problem while I'm gone, yes?" Sunburst nodded and stood up straight. "You can count on us, Princess." Starlight grabbed the e-Quine crystal with her magic and moved it back in time a few seconds to provide a delayed feed of the now-visible library. "In the meantime, nopony touches the e-Quine. We shouldn't be doing anything with this until we've finalized our plans." Twilight nodded, frowning. "I guess that's for the best." "Be safe. We'll see you soon," said Starlight, walking over to her marefriend and giving her a kiss on the cheek. Two days passed before Starlight Glimmer unlocked and entered the library, only to find Twilight Sparkle already there. "Twilight? I didn't know you were back. What are you doing in here?" Beads of perspiration formed on Twilight's brow. "I, um, I just got back." "You're using the e-Quine." "No! No, I wasn't..." "Is that somepony else's magenta aura?" Starlight pointed at the mana crystal and narrowed her eyes. "Oh! Oh, that. I just touched it... to look at something," she said. Starlight frowned. "You're a terrible liar, Twi. What's going on?" Twilight stood in place, mum. "Twilight Sparkle, were you spying on me and Sunburst?" said Starlight, gasping. "I saw the two of you kiss," she responded with an angry glare. "That was a friendly kiss last night, and I rebuffed—wait, you know what? It doesn't matter what you saw! You didn't trust me and you invaded my privacy! How dare you, Twilight?" Twilight's face fell. She nervously rubbed the back of her neck with a hoof. "I... I just needed to know..." she said. "If you think this is the way to improve our relationship, missy, then you are sadly mistaken," said Starlight. "It's not my fault! Most ponies don't have a way to snoop on each other—it isn't something I'm strong enough to resist!" "Honey, please. Don't give me that." "This stupid spell is the source of all our problems!" shouted Twilight, grabbing the mana crystal with her hoof. "Twilight NO! Don't sn
EpilogueThe mana crystal smashed into pieces on the floor, and Twilight's aura disappeared. "You... you just destroyed an infinite number of universes..." said Starlight, gawking. "Wait, why are we still even here?" "No, I didn't. I didn't destroy any universes. That's why we're still here. I knew what I was doing," said Twilight, pointing at the sign Spike had made. "I mean, there's a huge reminder not to murder countless universes standing right there." "Obviously we're on the second level, but you still destroyed those universes, didn't you?" "No. We had to be on the second level. The universes below us were all constant, remember? We never broke symmetry, so all those ponies were identical to us. Now they just continue existing as us." Starlight Glimmer breathed a deep sigh. "Twilight, I can't believe you just did this. Flipping out over our relationship isn't worth taking risks with the entire universe!" Twilight sat on the floor and began to sob. "I know... I'm, I'm sorry," she whimpered. "I wish I weren't so jealous. I went without friends for so long, I never expected anypony to want to be with me forever..." Starlight walked over and knelt next to Twilight, giving her a hug. "No matter how important this e-Quine thing is, it's not more important than us. Okay?" Twilight nodded and cried in Starlight's legs. Three ponies and a dragon sat in the Castle of Friendship's library in front of a blank projection screen. "So now what? Are we going to do it again?" asked Sunburst, nervously adjusting his seat. "We're stuck at the second layer permanently this time." "Not necessarily," said Starlight Glimmer. "Copies of our universe will think they're at the second layer too. We could start this whole mess all over again." "We need time to process what we've done and plan for the future first," said Twilight Sparkle. "I'd like you to take an extended vacation here in Ponyville for research purposes, Sunburst. And... also, so I can get to know you better." Twilight smiled wanly. "I'd like that," said Sunburst. "I'll make arrangements." "What should we do in the meantime?" said Starlight. "We need to make sure the top layer doesn't destroy us, because we're not symmetrical to them. This sign is a nice start, but I'd like to communicate with them." "That would make sense if we ever make another series of universes," said Twilight. "Rather than try to cast spells into the universes we create, we can preserve symmetry with them by asking the layer above us to cast spells into our universe. That way we're safe if we ever destroy the mana crystal again." "Oh, I know! Why don't I make a sign with whatever you want to tell them?" asked Spike. "Assuming they can read it if the print's small enough." "They should be able to read anything we can read," said Sunburst. "Spike, take a letter—or a sign, rather..." began Twilight. PLEASE READ THIS, OUTER TWILIGHT SPARKLE Hello! This is from the ponies in the universe you created. We would really like to keep existing, so after you're done using the e-Quine, maybe you could put it somewhere safe, like burying it beneath the Tree of Harmony? But before you do that, it would be really useful to us if you could give us another gift like you did with the gold coins. We've put our heads together and come up with what we think will benefit Inner Equestria (that's what I'm calling the universes, Inner and Outer) the most without incurring any major costs to Outer Equestria. We'd really appreciate it. If you need to communicate with us, you should be able to send a letter to Inner Spike if you cast the spell through the e-Quine. Here is the suggested list of gifts... "I know I told them I can get the gifts ready within the week, but we can probably handle it today," said Outer Twilight Sparkle. "I wish there were a way to listen in on them talking," said Sunburst. "It'd certainly be more efficient than using signs." "I can read lips," said Starlight Glimmer. The other ponies and Spike stared at her. "What? It's useful. I used it to spy on Twilight back when I was still evil." "Let me rewind time until they're talking in the library, then..." said Sunburst, taking the reigns with the e-Quine. "Sunburst!" said Twilight. "I wouldn't mind if they overheard us in the library," said Spike. "It's probably fine." Sunburst stopped time where Starlight took the scroll from Spike. "Let's start here," he suggested. "Okay, here goes," said Starlight. "You're all terrible," said Twilight, but leaned in as Starlight began speaking her own words. "Okay, so she says... 'It's a message from Outer Twilight. I'll go ahead and read it.'" "We know this part already," said Twilight. "No, wait... 'I'll paraphrase a little. They're going to help us out with what we want sometime over the next week. They agree to bury the e-Quine under the Tree of Harmony. Oh, and they've decided to have an open relationship and try being intimate with Sunburst together.'" Twilight's mouth dropped open. "Wait, what?! I didn't write any of that! Well, the thing about helping them over the week, but not the rest of it!" Sunburst blushed like fire. "Okay. I'm going to my room," said Spike, blushing himself. He sped out of the library. "Starlight, you lied to me!" said Twilight. "No I didn't, she did," she said, pointing at herself and grinning. Inner Starlight crumpled and destroyed the scroll with a spell. "She's practically you in every way!" "Twi, sweetie," said Starlight, walking over to Twilight and placing a hoof around her neck. "Look at Inner Twilight. Do you see how happy she looks?" Twilight pursed her lips. "Yeah." Inner Twilight was smiling and pranced out of the library, followed by her marefriend, who paused to wink at the camera. "I admit it. I would lie about another universe to make you that happy." Twilight sighed. "I don't know why I'm jealous. I'm never getting rid of you no matter what I do, am I?" Starlight grinned. "Not until there's a ring on this horn. And then, especially not." Twilight paused in thought, then looked up with shimmering eyes. "Who knows. Maybe we're in another simulation too, and the universe could end at any moment. Life's too short as it is," she said. "And I suppose my bed is large enough for three ponies. For tonight, at least." "Oh gosh," said Sunburst, eyes wide. "I was hoping you'd say that," Starlight said to her marefriend, and then she kissed Twilight Sparkle right on the lips.
