Twilight Sparkle stood upon the balcony of New Canterlot Castle, floating several kilometers above the ruins of the once grand castle whose long hallways she once would gallop around excitedly as a filly. Massive, towering skyscrapers of magically-reinforced concrete and steel dotted the landscape around her, glittering with thousands of bright, shimmering dots and lines just barely visible in the faint, red glow of the low-hanging sun, showing the flow of magic to and fro teleportation nodes throughout the city, like little living highways of light itself. Connecting many of these buildings were sleek and elegant bridges of white stone so wide and grand, one would need a good five minutes just to gallop from one side to the other.
A complex network of flying, metallic craft flowed through the gaps between the buildings, like many trails of ants between food. Each one had its own pattern of glowing spots and lines across their surface. The bottoms were lined with consecutive rings of pure, exposed magic, maintaining the crafts' defiance of gravity through continuously powered enchantments. In the far distance, several specks of yellow light arc rapidly upwards into the atmosphere from the distant interplanetary facility, before disappearing behind some low-laying clouds. A bit off to the right, specks of light blue light arc downwards from the sky into a facility of mirror image to the first.
She closed her eyes and, as she had done now for almost half a millennium, reached deep within her, past the gentler streams of energy circulating her very core and dipped delicately into the raging, churning pool of magic that lay buried far under the surface. Her horn lit with a brilliant, magenta aura, and she reached far into the heavens to caress the celestial bodies that had been hers to hold and guide for the last few centuries. The sun slowly made its final descent below the horizon. Even with the shadow of night cast upon the world, much of the city remained lit thanks due to the thousands of specks and streams of magic that permeated every bit of architecture.
Moments later, the stars flickered into view, and the moon emerged from below the earth, rising high into the sky and bathing the cityscape in its faint, silvery light. Due to the sheer number and height of the many high rises in the city, as well as continuous glow from the artificial lighting spread throughout every structure, she doubted many ponies even noticed the return of the once dominant source of light during the ancient night to its rightful place.
She let out a tired sigh as she gazed across the transformed landscape, marveling in the unique beauty it presented. Hundreds of years of hard work, centuries of tireless nights and research, centuries of failed experiment after experiment, but no matter what came her way, she pushed through. Now there was just one more problem to tackle, one more hurdle to carry her ponies over.
Her ears flicked as a soft beep caught her attention behind her. She turned around, her ethereal mane flowing gently behind her, and eyed the amethyst gemstone sitting atop the nearby crystalline table pulsing with a dim purple glow deep within. She trotted up to it and brushed a hoof against it, triggering a much stronger and steady glow from inside. The light brightened and focused to the side before coalescing into the translucent, shimmering, three-dimensional form of an gray, armored stallion standing on the other side of the table. She gave a short nod. "Good evening, Captain Stalwart. Has something come up?"
He gave a quick salute with a hoof. "Your Highness! You have two guests requesting a private audience with you."
Twilight groaned inwardly. "Is the matter urgent? It's gotten rather late, and I was hoping to get some rest tonight after that considerably long announcement I made earlier today."
"Uhm, well..." He glanced briefly behind himself and fidgeted a bit awkwardly, a behavior that piqued Twilight's interest as she'd almost never seen his stoic composure broken. "They didn't exactly say it's urgent, but they still insisted on speaking with you tonight."
"Oh?" Twilight raised an eyebrow. "I specifically told you, unless it's an urgent matter, to turn back anyone requesting to meet with me tonight. It's been a tiring day, and like I said, I was hoping to-"
"Sorry, your Highness, I, uh, am not sure I can just turn these two away like normal."
Never in his long tutelage to Princess Twilight had she seen Stalwart fail to hold his ground on anything if she herself wasn't challenging him on it. "Who are they again?"
"They said they were old friends of yours, and refused to elaborate further when I questioned."
Twilight's eyes widened. It had been four centuries since the last time she laid to rest an old friend. Of the very few old friends she had left, she had a strong inkling which two they were. "You may send them up, Captain."
"I-, understood, Princess Twilight."
The glow from the crystal flickered and disappeared, as did the glowing projection of her captain from the air in front of her. She gently floated her crown from atop her head and held it in front of her, its sleek, golden surface reflecting the distant light from the few hovercrafts that would break away from the highways and travel higher into the sky towards the docking station on the ceiling of the castle.
She put her hoof against the six-sided, purple star that donned the middle of the tiara and felt the ambient threads of magic interweaved across the metal. It had been so many, many years, and yet the two magic signatures that flowed within remained just as familiar to her as the day it was given to her. Her own eyes stared tiredly back at her numerous times through the reflections of the gemstone.
She rested the tiara on the table beside her, right next to the crystal, and turned towards the automatic double doors of her room just as they slid open with a hiss. Two forms walked in, their forms shrouded in ragged, black cloaks that masked their face. One stood to the same height as her, while the other was just short of it. "Celestia. Luna." She smiled warmly and bent down in a low bow. "It has been quite a while."
The taller form reached a pristine, white hoof to up her chest and detached a small, black, diamond-shaped device from her fur. The cloak around her disintegrated into a grid of thin, blue lines of light that were subsequently rapidly absorbed into the device, revealing the form of an all-too familiar white alicorn with her flowing pink, green, and blue mane, minus a crown and regalia. Behind her, Luna did the same.
Celestia and Luna glanced at each other and chuckled, returning the bow in kind. Celestia smiled as Twilight stood back up. "Twilight, your eyes meets my own at the same level now and have for a long time. You need not to bow to me anymore, though after telling you for several centuries, I doubt this one will be the one to do it."
Luna pouted slightly. "I still can't believe you surpassed my height. I have known you to be taller than me now more than ten times how long I had known you to be shorter."
"Is that so? I don't count the years anymore." Twilight let out a weak chuckle. "It really is good to see you two again. Did you really walk all the way here? I had a personal teleportation node installed at your place a couple hundred years ago, so you can avoid the long journey or even needing to teleport yourselves."
Celestia rolled her eyes with a laugh. "Well, I guess we're just old fashioned that way, then."
Twilight smiled, then tilted her head curiously. "However, I feel I should ask. You've never ventured all the way back here before for a visit. In fact, I think this is the first time since my coronation that I've seen you two back in the capitol. Is there something you wish to tell me?"
Celestia's smile falters. "Actually, yes, there is."
"We watched your public announcement earlier today on one of those real-time crystal screens back at Silver Shoals." Luna stepped in. "The one about your new project?"
Twilight nodded. "Yes, the Dyson Sphere project."
"Don't you think it might be... a little much?"
Twilight raised an eyebrow. "What ever do you mean, Luna? I admit, it's quite the undertaking. Something large enough to encompass a star itself is nothing short of science fiction. In fact, I think Rainbow Dash actually used to tell me about similar stuff like that from those science fiction books she started reading when she was retired." Twilight laughed dryly and turned around, admiring her wall. In the far corner, obscured in shadow, was the tattered remains of a Wonderbolts poster back from before flight enhancements were even a thought. "She told me if we ever got to that point, how much she'd love to fly out there in space and help build it with her own two hooves. I think she'd be happy to see where we are now."
"That's... not my point, Twilight."
Twilight turned back around. "Then what is?"
Luna shuffled on her hooves. "Twilight, I'm no stranger to science fiction either, any books the late Rainbow Dash had read on the matter, I likely had either read as well, or even helped edit myself. As aware as I am of the concept of a Dyson Sphere, did the substitute of a Dyson Swarm ever come to mi-"
"Of course it came to mind, Luna." Twilight interrupted, eliciting a faint frown from Luna. "It would have indeed been effective at considerably raising our level of energy extraction, and likely would have been perfect for sustaining our home planet fine enough. However, by my calculations, the rate at which our last four interplanetary colonies have been growing and advancing, in addition to the several hundred already approaching our stage of development, implies that a swarm would only be enough for another millennium or so. And that's only at our current rate of energy consumption.
Twilight took a breath. "In other words, shifting to a sphere from a swarm would be inevitable, so it would be more efficient to just jump to that now while we are able to, in order to support the anticipated advancements in energy consumption rather than just our current level. "
"But the materials needed for a project of such scale is unfathomable! Even with the resources from the colonies, you wouldn't even come close to-"
"From the colonies alone, yes." Twilight held her hoof up. She trotted back over to the window and leaned against the railing on her forelegs, turning her eyes to the sky. "However, using unfinished pieces of a grand-scale teleportation enhancement spell Starlight had been developing as one of her final passion projects, we actually have access to several thousand nearby uninhabited solar systems from which we can extract further matter from for the construction of this project." Twilight smiled as she practically felt Luna's eyes bulge out of their sockets. "We only inform the public of breakthroughs that are within the parameters of our current levels of growth. There's been no need to bring up such a development to the populace long before we even start to use it."
She turned back around to face the two sisters. "But you already knew about this, didn't you, Celestia?"
With a shocked expression, Luna whipped her head to face her sister, who had remained awfully quiet during the initial exchange. Celestia smiled coyly. "Oh? And how could I when you've never told me?"
Twilight chuckled. "You've balanced the sun and moon for a thousand years, many centuries longer than me and far before I was even born. Just a few decades ago, I learned how to stretch that awareness further out from the celestial bodies and into the surrounding pockets of space itself, as part of my research into a potential asteroid deflection system. That's when it hit me, that we've never actually had a documented case of an asteroid making it past our atmosphere." She pointed a hoof at Celestia. "What I just recently discovered, you've already mastered, haven't you? Even after my ascension, you've been subtly smacking asteroids away from the planet for centuries. So you had to have felt our test trials in warping crafts into nearby systems."
Luna stared at Celestia in awe, before shrinking into yet another pout. "I've been trying to do that too, you could have told me, Tia."
Celestia smiled. "Oh, Twilight, I've missed hearing your deductions." She trotted towards the balcony and gazed upwards. "Yes, I feel almost every little object that comes and goes. I admit, it was annoying at first trying to tell the difference between an Equestrian craft and an asteroid once we began exploring other worlds, but I've gotten better." Her smile faded. "I know what you're going to ask me."
Twilight nodded. "Why didn't you say anything?"
"Because I thought you'd figure something else out. Or... hoped you would. We both knew we were reaching the limit of how much energy we could extract through our own fusion. You were the one who came to us to begin with, begging us to help you with a project to improve how much magic energy could be converted from the captured power of the atom, but we were unable to make any strides. Sooner or later, you were gonna turn to the stars themselves, the true masters of the atoms."
Twilight looked away, staring back at her tiara as it sat beside her communications crystal. "Have you found an alternative on your own?"
"No." Celestia lowered her head.
"Then what are you here for? To congratulate me?" Twilight stepped up besides Celestia as they stared into the sky. "You sound like you wished I took a different route from the one you knew was inevitable from the start." She turned to face Luna. "Even you, as surprised as you sound."
Celestia faced Twilight and looked her in the eyes. "Twilight, the sun is... a part of me, in a way. Just as much as the moon is a part of Luna. The construction of a Dyson sphere around it would-"
"Are you worried about how Equestria would fare without the light of the sun?" Twilight laughed dismissively. "Don't worry about it, I've worked out the schematics for a smaller pseudo-sun that would orbit much closer to the planet, using only a fraction of the captured power of the sphere while bathing the planet in an identical level of-"
"That's not it, Twilight." Luna cut in.
Twilight tilted her head. "Then what?"
Celestia let out a sigh and gestured with a hoof to the cityscape. "Do you see any green out there?"
Twilight knew where this was going, but still abided, failing to spot a speck of natural green. "We have gardens, you know. You may not see it from here, but the trees and plants aren't dead, we still manage thousands of massive greenhouses across the country, and in the terraformed colonies, there's already large swathes of forests spreading across the-"
"No, Twilight, I mean- Yes. There are still trees and ferns and bushes and farms, but they're all... artificial. Or at least, artificially grown."
Twilight blinked. "They're still the same species of plants from your reign. I know we had a brief period delving into genetic optimization, but we quickly did away with that once more natural and magic means of enhancement were discovered."
"What I'm trying to say is, everything now is so perfectly managed and controlled to a tee." Celestia breathed out slowly. "Many natural processes have been replaced over the last few centuries with enchantments to speed things up or make things more steady. I know what you're probably going to say, and yes, everything is better now."
Twilight froze. "That... was what I was going to say. So, what did you come all the way to tell me then, if you think everything is indeed going the right way."
Celestia fell to her haunches. Twilight reflexively reached out a wing to catch her, but stopped when she noticed her tired expression. "A Dyson sphere would completely surround the sun, grasping every bit of light and heat it puts out for use as energy and magic. The sun would no longer shine, and the moon would likewise no longer reflect its glow."
"I-..." Twilight paused. "But... I have a plan for that, for both of those. I could fine-tune it to make it seamless too, so it wouldn't look any different."
"But we would know." Luna walked up behind Twilight. "I would know what rises in the night sky is no longer my moon, as Celestia would know what shines down during the day is no longer her sun, but a mere shadow of itself."
"But that-" Twilight sputtered in confusion. "That wouldn't impact anything, right?"
"It would not." Luna smiled weakly. "But in the end, the sun and moon are the last remaining... 'natural', untouched elements of the natural world. The ocean, rivers, wind, earth, even the sunlight itself, have all been integrated in some way in the extraction of energy and this advancing world you've built. They're like... the last remaining relics of us."
Twilight looked between the two of them. "I don't get it. If you know this is the best remaining route for us, and aren't even against it, why tell me all this anyways? Is there something you wish for me to-"
"I ask nothing of you with regards to this, Twilight. And I certainly don't wish you to adjust your grand plans just cause two stubborn old mares wish to cling to a treasured past so much." Celestia smiled. "I guess we're just old-fashioned that way. Maybe we will just... miss them." She leaned against Twilight, who unfurled a wing and wrapped it around her. "Maybe it's like how I miss doing this to you, Twilight, being able to wrap my wings around you when you were so small and young. Even though I know how much better it will be in the end to let you grow and fly."
Twilight held her tighter, feeling Luna sidle up to her other side. She wrapped her other wing around her too. "But... I'll still be here? The sun and moon won't go anywhere even if you can't see it anymore. You can still feel it, right? Why tell me all this?"
Celestia sighed and closed her eyes. "I can... and I know I always will. That doesn't mean I won't miss seeing it. I guess..."
"...we just wanted you to know, lest our thoughts stay hidden in silence."
