Princess Luna looked up from a scroll of parchment and raised an eyebrow. "Well, that is most certainly a curious question."
"Seriously, though," I remarked. I hovered across from the Princess of the Night in the throneroom of Canterlot Palace's Midnight Wing. "It can't go on forever. I mean, the Sun has got to come up somewhere. So where's the edge of the world?"
"Though shouldst know the answer to that, Rainbow Dash."
"Oh. Uhm..." I blinked, my ruby eyes squinting in thought. "The world is—like—a big flat chunk of earth floating in stars and chaos and stuff, right?"
Princess Luna paused. She placed her royal documents down and looked over at me squarely. "At thy age, we imagine that thou hast attended quite a few classes on the subject in thy schooling."
"Erm... eheheh..." I blushed and scratched my brow with a blue hoof. "I... n-never was all that good at staying in school."
"So we see..."
"Learning is all good and stuff, but there was just so much flying I wanted to do!" I shrugged. "Even at flight camp, they wouldn't let me fly enough. Was I there to get better or not?"
"And how wouldst thou say that things hath turned out?"
"Well, I have no intention of being a scientist anytime soon." I said, then sighed. "Or for very much longer," I muttered.
"Verily..." Luna stood up, flexed her wings, and paced across the throneroom in the midday light. "The earth is a long, flat plane. The latitudinal length far exceeds the longitudinal width."
Luna sighed, then paused to look at me. "East and west hold greater distance than north and south."
"Oh, I see."
Luna resumed pacing. "The world floats in a piece of the cosmos dominated primarily by chaos energies. The Elements of Harmony have always served as a beacon of purpose through which life has thrived in spite of all the contradictory factors. As for the Sun and the Moon, they are bodies of luminous mana that the alicorns brought to this plane."
"So, wait..." I leaned my head to the side. "The Sun and Moon weren't always around?"
"Like so many things, Rainbow Dash, they were provided to this landscape when our own flesh and blood first arrived here. There are several ponies of alicorn descent spread throughout the world, but only our sister and we possess the powers of our forbears. With the magic at our hooves, we have kept the Sun and Moon in constant motion, illuminating the landscape from right here in the center of the bright half of the world, the kingdom of Equestria. For several thousands upon thousands of years, we have served as the sentries to this world, warding chaos and keeping dark energy at bay."
"That's... quite the commitment," I said.
"So, like, where does the world end?"
"There are several edges to it. The north and south borders are feasible to reach, even by mortal standards. The east and west extremities, however, are thousands upon thousands of miles from here in either direction."
"Have... Have you seen the end of the world?"
"Affirmative," Luna said, nodding slowly. "We hath been to both the east and west edges."
"How many times?"
"A total of five," Luna said calmly.
I had to beat my wings faster to keep from dropping upon hearing that. "Wait. So you mean to tell me that in all of the crazy years upon years that you have been alive, you've only visited the ends of the world no more than five times?"
Luna nodded. "We do not believe we have emphasized the fact enough: the world is quite a vast place. Alicorns such as our sister and we cannot afford to make long and arduous journeys without sacrificing the task of protecting Equestria. The physical realm is too vast for us to do more than illuminate with light and harmony." She took a deep breath. "Now, far more than ever, it is an even greater challenge. With our sister putting all efforts into safeguarding the rift, we doubt very much that we can so much as leave the immediate borders surrounding us."
"Then how do you look after the rest of the world?"
"There was once a time when we could," Luna said. "That was when there were far more of us than there are today. The alicorns have since dwindled, and now the world belongs to the huge population of mortals who spread their kingdoms far and wide. In anticipation of this eventuality, the first alicorns introduced harmony to this land. It began with the Elements, but then the Elements would embody themselves in living ponydom."
"The Element Bearers..." I exhaled. "Twilight and the rest of us. We were the first to possess the Elements in spirit, weren't we?"
"Nay, Rainbow Dash," Luna said with a shake of her head. "Thou six were the strongest, but hardly the first. In truth, the Elements of Harmony have been blending with the living population of this realm for eons. When thou, Twilight, and the rest of thy ill-fated companions acquired the six Elements, thou completed the final stage of Harmonic Acclimation."
"It was the grand purpose of the Harmonic Prism since it was brought to this world at the beginning of all life here," Luna said. "Through Acclimation, the same spirit that gave alicorns vigor, energy, and peace of mind would be passed onto the sentient mortals of this world. Someday, Rainbow Dash, Celestia and we shall no longer be around, and it will be up to ponydom itself to maintain peace and harmony in the center of this pocket of the universe."
"So... then..." My brow furrowed in thought. "This world is kind of like a garden?"
"And a most exceptional one at that, full of both beauty and terror, and yet ultimately favoring life, which hath been our goal from the start." Luna took a proud breath. "We stand upon the edge of a new beginning for this world. It is a shame, however, that the final stage in its foundation would prove to be such a dark chapter. If Twilight and thy other friends had lived, we may have witnessed something even better than Harmonic Acclimation."
"And what would that have been?"
"Unification," Luna said. "Thou six were more than just mere mortals. The Elements were meant for thee; together, thou could very well have spread peace and harmony across the land in greater intensity than my sister and we are capable. The kingdoms beyond Equestria would have been united under more than just light. Ponydom would become whole, and would form a utopia that would banish chaos forever."
I stared down at my pendant, feeling the cold, golden surface with a trembling hoof. "I guess fate didn't wanna work with us much, huh?"
"This world is a good garden, Rainbow Dash," Luna said. "One way or another, unification will happen. We simply suspect that it will take a great deal longer than we had desired."
I looked beyond the balcony, towards the misty mountains lingering beyond Canterlot in the platinum sunlight. "I wanna see it," I murmured.
Luna glanced my way. "Hmmm?"
"I wanna see it all," I added, wings flapping harder as I stuck my muzzle into the windy currents. "I wanna fly those thousands of miles, see the kingdoms that are there to be seen, find mountains I've never imagined flying over before."
Luna breathily remarked, "It's quite a daring thought, Rainbow Dash, but hardly something thou art capable of, wouldst thou think?"
"Take a look at yourself, your sister, and all the powerful alicorns who came before you..." I turned towards her and stared hard. "And tell me... who doesn't die?"
Luna said nothing.
"I'm sick of waiting around, sick of being mopey, and sick of being alone," I muttered, staring out into the horizon yet again. "If I got a few months left—or even less than that—what's it matter? I want to see this garden that you've grown, Luna. I wanna see if it's truly that beautiful..."
"I wanna see if it was worth my friends dying for it," I said.
Luna trotted over towards me. "No single mortal has ever scaled the far ends of the world and lived to tell about it."
"So what?" I turned and looked up at her. "I'll be the first one."
Her eyes narrowed. "Harmony is a great power in this world, but it is still contested. Until Acclimation or Unifications takes hold, the landscape thou so desireth to see will remain wrought with peril. Thou wouldst need an entire batallion of Equestria's finest pegasi guards to protect thee—"
"And what?" I frowned at her. "Spread Equestria's defenses even thinner? Face it, Princess, you're down one Alicorn. You and everything that serves you is needed here." I pointed at myself. "What good would I be to you?"
"Thy soul is precious, one of a kind—"
"Then do something special for something as rare as me," I said, my eyes imploring. "Let me go, your Highness."
Luna said nothing.
"Let me go, Luna. I am nothing here." I sighed and gazed off into the brightness. "I am nothing anywhere but moving."
The throneroom was silent. A cool, misty wind blew through, then returned the marble floor and walls to a muted hush.
"We cannot and shall not stop thee, if this is thy wish, Rainbow Dash," Luna said. "But we do ask that thou taketh time to think this over—"
"Your Majesty, the time I could spend pacing in circles and rethinking my life, I'll soon discover that I'll no longer have a life." I pivoted about in my hover with my forelimbs folded. "So let me go live it, huh?"
"If there was any pony who couldst make it to the world's end, we would suspect it'd be you."
"Now that's more like it," I said with a smirk, glancing wearily aside. "And, who knows. If I don't make it, I'm bound to see some pretty nifty sights along the way."
Luna looked distracted. The Princess fidgeted, her nostrils flaring. Eventually, she said, "But if thou didst make it, and went even further, then perhaps thou wouldst have even more sights to see... for thou wouldst have gained an even longer lease on life."
I blinked at that. With my heart beating faster, I turned and looked at her. "Excuse me?"
She looked blankly at me. "The Midnight Armory..."
"The Midnight Whatsit?"
"Hast thou ever heard of it?"
I made a face, slowly shaking my head.
She nodded, then motioned me to follow her as she trotted down a long hallway. "Come, Rainbow Dash. Walk with me..."