“Knowledge may give weight, but accomplishments give luster, and many more people see than weigh.”

Philip Dormer Stanhope

Rainbow Dash skidded to a halt in front of the library, kicking up a trail of dust. She reared up and repeatedly slammed her front hooves on the door. The entrance held fast under the barrage of kicks.

“Twilight! What’s this I hear about you closing the library!?” She dropped down and executed a whirlwind kick, slamming both hind hooves against the door. The tree trembled slightly and a few leaves drifted down, but the door held. “This is a public institution funded by taxpayer bits! You have an obligation to the community!”

A nearby window opened up and Rarity poked her head out. “My word, Dash! It’s not even locked! Haven’t you ever used a door handle before?”

“But I heard the library was closed! What’s up with that?”

“It was closed for all of two hours. It’s open now.”

“Oh. Well... alright then.” Dash lifted the handle and shoved the door open, immediately zipping over to the hardcover section of the young adult shelf. She tugged out a book and settled into an overstuffed beanbag. “This place still closes at around eight, right?”

“Nine to eight-thirty weekdays,” said Twilight, “nine to five Saturdays, one-thirty to five Sundays. The only stat-holidays are Summer Sun Celebration, Nightmare Night, Winter Wrap-Up, and National Equine Polysaccharide Storage Myopathy Awareness Day.”

“National huh?” Dash lowered her book and looked at Twilight. Only then did she notice the gigantic mechanical pillar that ran through the center of the entire library. She stared at the smaller devices scattered about the hall, most of which were still being packed into crates.

Dash pointed up at the gleaming technological column. “What the hey is that?”

“It’s a genetic predisposition to improperly digest grains. It’s common among heavier horse breeds.” Twilight leaned on one hoof. “It’s a serious condition, but I don’t know why we get a day off for it.”

“It’s the spelly-welly thingy-wingy,” said Spike as he trudged past with an empty crate. “It takes five days to pack up. We used it for less than an hour.”

Dash stared up at the pillar of scientific instruments. “What does it even do?”

Twilight looked up from her scroll. “It’s an analytical engine for the development of thaumaturgical—

“Dash, please!” said Rarity as she came out of a side room. “Twilight is composing a very complicated spell. She needs to concentrate.”

Dash’s ears flipped up. “Are you kidding? She never messes up a spell.”

“Don’t be so insensitive,” Rarity said. “She’s trying her best!”

“Insensi... wha?” Dash glanced at Twilight. “You mean it’s a tough spell, even for her?”

“It’s not tough at all. It is a work of elegant simplicity that is—like all genius—obvious in retrospect.”

Dash pointed at Twilight’s scroll. “But I thought you said it was really complicated.”

“That spell, yes. But that’s not the spell we need to test.”

“There’s two spells?”

“Yes.”

“And one of these spells is super simple. And the other is super complicated.”

“Yes.”

“Is the simple spell supposed to... like... help you test the complicated spell?”

“The other way around, actually.”

Dash blinked at her. “So you’re using a complicated spell to help test a simple spell.”

Rarity nodded. “Indeed.”

“Well, Twilight can invent new spells, right? Why doesn’t she just invent a simpler kind ‘spell-testing’ spell?”

“Actually, she designed both of these spells herself. It has to be as complicated as possible.”

“So if you make the tester spell simple, it won’t work?”

“No, it would work perfectly. That’s the problem.” Rarity tilted her head. “Haven’t you heard a single word I’ve said?”

Dash stared off for a moment. “...Huh?”

“It’s done,” Twilight said and set the quill down.

“Excellent!” Rarity said. “I’ll go get the test chart.”

Rainbow Dash followed Rarity into a nearby side room. “You’re gonna tell me what’s going on. And you’re not gonna use any weird words that don’t make sense.”

“Sorry. We’ve been knee deep in advanced magical theory for hours now. After awhile, everything starts making sense.” She went to a large chalkboard on a wheeled stand, took a piece of chalk, and began drawing tiny circles all over the board. “Twilight needs to test a simple spell that’s designed to affect other spells. It took an enormous amount of effort to invent, but it’s very simple to cast. It was designed for ease of use.”

“Kay. So what’s the big deal?”

“We need to see if the simple spell can correctly affect a very complicated spell... and I do mean complicated. We’ve spent the last six hours trying to invent the most difficult, convoluted, demanding, and utterly ornery spell we can think of. We’ve made it excessively abstruse on purpose, just to see if the simple spell will choke when it tries to affect it. Seriously, Dash... I’ve never even heard of a spell this arduous.”

Dash watched as Rarity set down the chalk and tossed the cloth over the chalkboard.

“Is there any chance of a disaster? Like an explosion or something?”

“Oh, no-no-no.” Rarity wheeled the chalkboard out of the room. “It’s convoluted, but it’s not powerful. All it does is solve a mathemagical problem. There’s no chance of a catastrophe.”

Dash followed her into the main room. “So how tough is this spell? Be honest.”

Rarity rolled her eyes. “It’s an utter horror, I assure you. It’s so tangled and messy... it’s almost magnificent, in a grotesque sort of way. I know how talented Twilight is, but I’m not sure she’ll be able to pull this off.”

Dash glanced at Twilight, sitting at the table in a meditative trance. “But this is Twilight Sparkle we’re talking about. Is there really a chance she’ll... you know... mess up this spell?”

Rarity finished moving the chalkboard and set a hoof on Dash’s shoulder.

“We can only hope so.”

One of Dash’s ears flipped up. “...Wha?”

Rarity went to the chalkboard and stood at attention. “You know the rules, Twi. You have one hour to cast the spell... not a second longer. Are you ready?”

Twilight opened her eyes. “As I’ll ever be.”

Rainbow Dash stood, hushed. She knew what it was like to test yourself... to push your limits and attempt the impossible. She’d done the impossible herself, in athletic terms. She’d never imagined that a scholastic test could seem so familiar.

Come on, Twi. Dash clenched her teeth. You can do this... I know you can!

Rarity yanked the cloth off of the board and clicked a gold pocket watch.

“Go!”

Twilight’s horn glimmered, and the surface of her scroll sparkled. There was hardly any light or noise, and yet her eyes rolled up in their sockets... her lips twitched, struggling to speak through paralyzing convulsions. A piece of chalk flew into the air and streaked across the board, connecting each of the little circles with a continuous series of sharp-angled lines. Within moments, the entire board was a giant mess of white zig-zags.

The chalk fell to the floor and snapped in half. Twilight collapsed on the table, gasping for breath. “That was... wow. That was much worse than I thought it’d be.”

Rarity stared at her watch. “Twelve... seconds?”

Dash stared at the chalkboard. “Did it work? Did it?”

“I’m checking it now,” Rarity said as her horn glowed. “It’ll take a minute or so.”

Dashe went to Rarity’s side and stared at the board. “What even is it? Seriously, what was she trying to do?”

“She was trying to solve something known as the ‘travelling sales-pony problem.’ It’s... well, it’s a...” Rarity held up a scroll. “It’s a non-deterministic polynomial-time problem.”

Rainbow Dash frowned at her. “Short words, Rarity. Or at least shorter.”

“Alright. See those random dots?” Rarity pointed at the chalkboard. “The problem requires you to connect every single dot, one after the other, using the shortest amount of line possible.”

“Like a kid’s game? Connect the dots?”

“Not even close. It’s an optimization algorithm, and the more dots you start with the harder it gets. Exponentially harder. A solution for just twenty dots is impossible to solve with just pen and paper. A hundred dots is nearly impossible, even with magic”

“How many dots are there?”

“Two hundred.” Rarity glanced at Twilight. “It should be impossible.”

Dash stare at the chalk lines. “If it’s impossible, then how can we tell if she’s correct or not?”

“Mathemagicians have been studying this problem for decades. A few years ago, somepony came up with a spell that only partly solves the problem. It examines a cloud of dots, and tells you the exact length of the shortest possible path. It doesn’t actually draw the path, but it allows us to compare—

Rarity froze, staring at the marks.

“Yeah? Did it work? Did it?”

Rarity stared at Twilight. “You’ve done it. You’ve solved the travelling sales-pony problem.”

Twilight shot up from her seat and galloped away, teary-eyed and distraught. “Arrgh! Why can’t I do anything wrong!?” She ran into the bathroom and slammed the door.

“But the spell worked,” Dash said, “didn’t it?”

“Yes... perfectly.” Rarity cast her eyes down, forlorn. “And I was so sure, this time.”

Dash stared at her, slack jawed. “What! Is! Going! On!”

A few minutes later, all three of them were sitting together on a circle of floor cushions. Rarity poured a cup of tea for each of them, and Twilight passed Rainbow Dash her latest letter from Celestia.

“Here. It should explain everything.”

Dash unfurled the scroll and cleared her throat dramatically. “From the desk of Princess Celestia. Dear Twilight Sparkle, my most faithful student: I am pleased to hear of your safe return to Ponyville, and wish you—

“Dash? You don’t have to read it out loud. We’ve already read it ourselves.”

“Oh... right.”

Twilight and Rarity waited patiently as Dash read the troubling letter. Her eyes slid back and forth quickly, half-lidded. They each finished a cup of tea, and Rarity went into the kitchen to fetch some biscuits. A faint chorus of birdsong drifted in through an open window.

When Dash set the scroll aside, her eyes were hard as iron. Rarity waited for her to speak, while Twilight stared into her teacup.

“So you need to stress test a spell, do you?”

Twilight nodded.

“But no matter how complicated the spell is, you can’t mess it up... not even on purpose.”

Twilight nodded again, still despondent.

“Then your problem isn’t the spell. Your problem is you.” Dash stretched a pair of flight goggles around her head and let them snap tight against her eyes. “When the student is ready... the master shall appear.”

Twilight’s posture straightened. “...What?”

“I think I can help you.” Dash steepled her front hooves in front of her face. “In fact, there’s a couple ways we could go about this.”

“Like what? At this point, I’d be willing to try anything!”

“Hm...” Rainbow Dash leaned her head back and gazed idly upward. “Have you tried...?”

The next day, twilight peered down from the basket of the hot air balloon. They were flying much higher up than she was used to: Ponyville looked remarkably like a model city. The streets were crowded with coloured specks, all milling about like ants.

“Dash? I’m not so sure about this.”

“You’ve got the spell ready, right?”

“Yes, but I’ve already used it for a test. We know it works, so it’s not—”

“Your problem isn’t the spell, Twilight. Your problem is you.” Rainbow Dash tossed her a pair of knee-high boots that were fused together at the heels and reinforced with steel bars. “Put those on your hind legs and snap all the buckles. Listen, Twi... the problem is that you’re just too dang smart for your own good. You can’t mess up a spell no matter how complicated it is. Getting a tougher spell won’t help at all... so instead, we’ll force you to cast a spell in a stressful situation.”

Twilight finished putting on the boots. “Are you sure these are the right size? They’re a little tight.”

Dash grinned. “Would you rather have’em too loose?”

Twilight peered over the edge of the basket and swallowed a lump in her throat. “Are you absolutely sure this is safe?”

Dash hefted a thick coil of rope and attached one end to her boots. “Perfectly. These cords are good for two hundred jumps.”

Twilight glanced over at Pinkie Pie. “Do you know how many times these particular cords have been—”

“A hundred ’n ninety eight so far,” Pinkie Pie said. “And the last guy was really fat.”

“What!?”

Dash patted Twilight on the back. “Don’t worry about it. They say that to everypony.”

“I don’t think this is going to work, Dash. I really don’t. I know what you’re trying to do here, but I’m not easily distracted. The princess taught me all sorts of meditation techniques.”

Dash tugged the cord one last time and stood up. “Have you ever done this before?”

“I can honestly say I haven’t.”

“Trust me. There’s a difference between meditation and keeping your cool.” She nodded to her. “You got your spell ready?”

“Oh, yes!” Twilight said. She held up a scroll with a math problem written on it. “It’s a spell used in differential geometry to calculate the surface area of a hyperbolic paraboloid that intersects with a—”

“That’s great lemme know how it goes.” Dash kicked Twilight in the flank and sent her tumbling head-over-hooves out of the gondola.

“Whoa... whoooaaAAAAA!!” Twilight’s voice became louder and shriller even as it grew more distant. “Sweet-Celestia-tap-dancing-on-a-tea-table, I’m dyin’! I’m gonna die!! Nooooo! I’m too young and intelligent to go! I wanna liiive!”

Dash leaned over the edge of the basket, chewing on a piece of raspberry bubblegum.

Pinkie Pie came up beside her. “How’s she doing?”

“Can’t really miss with a bungee cord.” She blew a bubble and sucked it back in. “Hey, were you serious about the fat guy?”

“Of course not, silly-filly! We say that to everypony the first time.” She held up a receipt. “Her cable was brand new.”

“Cool. Whoop... there’s the first bounce.” Dash frowned and leaned further out. “Whoa... is she still hanging onto that scroll?”

“I guess so. Should we leave her like that for a couple minutes? Let her enjoy the view?”

“Nah. We can’t give her too much time to solve that math problem of hers. Besides...” Dash reached for the goggles on her forehead and tugged them down over her eyes. “You know I’d never leave a friend hangin’.”

Rainbow Dash leaped out of the balloon and dove down in a spiral. She hovered in midair near the end of the cord. Twilight had stopped bouncing, but was still swinging back and forth. She had also stopped screaming, but was still wild-eyed and gasping for breath.

Dash hovered side to side as she swung back and forth. “Are you glad you went to the little filly’s room first?”

Twilight twisted her neck around, trying to make eye contact. “I have a newfound appreciation for newtonian physics.”

“So how’d it go?”

“Not good. I was trying to calculate my parabolic trajectory to see if I could predict how my gravitational acceleration would interact with the deceleration of the elastic cord.” Twilight sighed. “I was in freefall for more than five seconds, and I totally forgot about air resistance. My calculations were way off.“

“Yes!” Dash did a mid air backflip and thrust a hoof skyward. “One spell totally spoiled!”

“What? No, the spell worked great.” Twilight held up the scroll, now covered with messy writing. “I was just doing the physics afterwards, to pass the time. You know, to distract myself from the absolute numbing terror.”

Dash crossed her forelegs and glowered at her.

“Can I get down now? I can’t feel my hind legs.”

Pinkie Pie strolled through the forest just south of Ponyville and came to the winding bank of the Red Roan river. She glanced to each side of the rushing rapids and saw a tall wooden scaffolding on the bank. The lattice was holding up a steep ramp that ended in a huge loop-de-loop. There was a small crowd of ponies nearby, curious and bemused.

Pinkie Pie sighed and went to the scaffolding. She climbed up the precarious step ladder and reached the uppermost platform. Twilight was standing on a skateboard, clamped onto it with a set of boots. She was also wearing a saddlebag secured to her back with a durable shoulder harness.

“Twilight?” she said.

“Aah!” Twilight wobbled back and forth and looked over the edge of the precarious tower. “Don’t sneak up on me like that!”

“Is there something you want to tell me? Cause, y’know... I’m always here for ya, if you just want to talk. About stuff. That you want to talk about.”

“No, it’s... I’m fine. Dash is helping me with something. That’s all.”

“First the bungee jump, and now this?” Pinkie Pie stepped forward and set a hoof on her back to keep her from rolling away. “Twilight, Rainbow Dash’s idea of fun isn’t appropriate for most ponies. I know you’re trying your best, but we can find something else for you to do. You need to find out what you’d enjoy.”

“This isn’t for fun, Pinkie Pie! It’s important.”

“Whatever it is, there must be another way!”

There was a rush of air as Rainbow Dash landed next to them. “Here we go. I’ve put a different math problem in each of these envelopes. You’re not allowed to open them until you—”

“You!” Pinkie Pie pointed down at the ramp. “You can’t expect her to have this much fun! It takes years of discipline and training to enjoy yourself this much!”

“Nah, nah. She’ll be fine.” Dash passed three envelopes to Twilight. “I gave her a book about what to do.”

“A book!? That won’t help her pilot a skateboard! She can’t even ice skate! Don’t you remember the last winter wrap-up?”

Twilight shuffled her envelopes. “You know, Dash, I think Pinkie Pie might be right about this whole—”

“That’s great lemme know how it goes.” Dash kicked Twilight in the flank and sent her rolling.

“Whoa...aaa! Ahhh! AHHH!!”

Pinkie Pie and Rainbow Dash watched as Twilight plunged down the sheer drop, leaving the three envelopes to drift in the air behind her. A split second later, the envelopes flashed with magical light and zoomed after her.

Pinkie turned to Dash.

“Don’t give me that look,” Dash said. “There’s a rail on the ramp. She can’t miss.”

A cheer from the small crowd below caught their attention. They watched as Twilight spun through the loop-de-loop and rocketed into the air above the river.

“She should be having fun!” said Pinkie Pie. “Haven’t you done enough to her?”

“Miss Pie, we ain’t even started yet. If you’ll excuse me, I have to buddy up for the most extreme differential equation Ponyville has ever seen. And this time...” Dash snapped her flight goggles into place. “...She’ll have to show all her work.”

Dash leaped from the scaffolding and shot through the air, catching up with Twilight just as she hit the river. She’d been screaming since she’d gone down the ramp. The wheels on her skateboard snapped up, transforming the apparatus into a smooth, sleek wakeboard. Twilight skipped across the surface of the water once, then skimmed along smoothly.

Dash took out a loudspeaker as she caught up with her. “We’re not done yet, Twi! Pull the red cord!”

She couldn’t quite see what Twilight was doing, but a moment later her saddlebags burst apart. A sharp, triangular kite shot into the air: a narrow, pointed chevron of purple and blue cloth. It was connected to Twilight’s harness via a pair of kite strings. Dash dove down low and zoomed overhead, leaving a long, cylindrical hurricane in her wake. The kite passed through the powerful wind tunnel and shot ahead like an arrow. Both strings pulled tight and dragged Twilight across the surface of the river

“Level out, Twi! Are you trying to hit the riverbank?”

“Ahhh! This is absolutely nothing like a real kite!” The triangular arrow spun through the air in a series of rapid barrel rolls, tugging her side to side. “Can I please have a real kite!?”

“It’s a stunt kite! It’s the only real kite!” Dash swept low, skimming one hoof along the water. “You haven’t even opened an envelope yet? You were supposed to have one finished before you left the ramp!”

“Okay, okay! There’s... wait a second! You want me to solve a complex differential equation!? You heartless monster!”

“Are you a unicorn, or a uni-can’t?”

Dash streaked ahead with a series of corkscrew barrel rolls, and the hurricane trailed behind her. Twilight’s took control of the stunt kite and struggled to keep it within the artificial wind-tunnel. The river began winding left and right, and Twilight pulled the left and right strings: the kite swept to each side, and she leaned into each turn. Her horn left a trail of purple light over the water as her mathemagical spell took form.

“How’re you holding up there, Twi?”

“Almost done! I just need a little more—”

“Barrel jumps!” Dash zoomed ahead and slipped over a small barge with a ramp. “Miss even a single one, and you’re out!”

“Ramps? You never said anything about ramps!” Twilight gasped and swung the stunt kite to one side, low enough that its wingtip skimmed the water. Her surfboard kicked up a large splash as she leaned into a hard turn. Twilight’s board straightened out as she hit the front of the ramp. She sailed into the air, momentarily level with her kite. The scroll flared with the brilliant light of a completed spell just as she reached the apex of her jump.

“Sweet combo!” Dash shouted. “But you’re still one envelope behind!”

Twilight swept the kite left and right, skimming along the river at a breakneck speed. She streaked through four more ramps in total, each with more barrels than the last. Her posture was wobbly, but not once did she bail.

“Second envelope!” Twilight called out. “But there’s only one more ramp! I don’t think I have enough time to finish the last math problem!”

“Shows what you know!” Dash called from above. “I set up some cloud-rings! Just follow the flags and you’ll see where to go!”

Twilight hit the last ramp and gasped in horror. It didn’t lead onto the water: She was sailing straight over Ponyville’s waterfront residential district. She stared down at the rooftops and streets, and the crowd of unaware ponies... and the hard ground below.

Twilight slammed down against the angled roof top of a house. The surfboard scraped against the densely thatched roof, and the kite pulled her up and over the architectural ramp. Twilight looked at the rooftop ahead and saw a pair of rainbow-colored flags.

She clenched her teeth and swung the kite around. She stamped a front hoof onto a switch and popped the wheels back down. When she landed on the next roof, she shot between the two flags with enough power to jump over an entire street. Time slowed as she sailed through the air. She stared down at the surprised ponies below, and barely noticed the ring-shaped cloud ahead.

It’s... it’s working! I’m still alive!

The three envelopes swirled around her like electrons orbiting a nucleus. She unsealed the final envelope and scanned the text: The sum of five real numbers is seven, and the sum of their squares is ten. Find the minimum and maximum possible values of any one of the numbers.

Twilight finished another leap and landed on the second-tier balcony of the circular town hall. She twisted her kite around and did a grind along its circular edge, leaning away from the building. The pull of the kite kept her from falling over, and a shower of purple sparks sprayed off her wheels.

Oh, silly Dash...I could solve this without any magic at all! All I have to do is find an inequality that involves only one of the five real numbers. Twilight allowed herself a nervous, tentative smirk as her magic seized the quill. I solve this sort of thing on paper, so I don’t actually have a spell for it. I’ll just have to invent a solution-spell myself in the next twenty seconds...

Rainbow Dash soared over Ponyville, watching as confused ponies made their way down main street. Most of them were talking amongst each other and pointing at the ring-shaped clouds in the sky, or at the sets of colored flags that somepony had attached to certain rooftops. The area around the library was crowded in all three dimensions: Dash had to shove her way through a flock of pegasus to reach the building.

Twilight Sparkle was lying in a huge elastic safety net strung between several of the treehouse’s larger branches. Her mane was a complete mess and her eyes wobbled in different directions. Spike had climbed up next to her and was busy disconnecting her boots from the board.

“Twilight!” Dash hovered over. “You did it! You did the whole thing, perfectly!”

Twilight spoke, her voice weary. “Not yet... I... haven’t...” Her horn glowed, and a set of three scrolls hovered nearby. They were ripped along the edges and stained with water droplets.

Dash snatched them up and turned to the crowd of curious onlookers.

“Everypony, please! Is there a mathematician in the crowd?”

A hoof lifted up from the crowd. “Yes, actually! I was a university professor!”

“Me too! I teach college level calculus!”

Dash watched as several other ponies raised their hooves above the crowd. There were at least a dozen volunteers.

“Wow... really? Oughta start a club or something.” She cleared her throat and shouted over the crowd. “Everyone meet up by the crash net and form into groups. We’ve got a complex differential equation on the left, trigonometric functions on the right, and vector calculus in the middle...”

One of the professors waved as he approached the netting. “Does that include partial differentiation and multiple integration?”

“Well, uh...” Dash squinted at the scroll. “No wait, not vector calc. I meant... multi-variable calc. Is that right? I think that’s right.”

The three groups of academics gathered to discuss the contents of the scrolls. Dash went to the safety net and helped Twilight climb down. The crowd murmured and whispered, but gave Twilight and her judges plenty of breathing space.

The crowd fell silent as Cheerilee stepped forward and addressed the crowd. “Citizens of Ponyville! We have finished analyzing all three of these scrolls, and I have assessed the judge’s results. It is my opinion as both a grade school teacher and a theoretical particle physicist—that all three of these solutions are completely correct. Including all shown work.”

Dash stared at her in shock. “Seriously!?”

Cheerilee scraped a hoof against the ground, shyly. “Well, it was only to pay the bills for a few years. You know... until I could become a teacher.”

“Wooo!!”  Twilight reared up on her hind legs. “I did it! It totally worked!”

The crowd burst into applause.

Spike crossed his arms and cleared his throat. “How was any of that supposed to help?”

“She did it...” A smile crept over Dash’s face. “She really did it!”

“Isn’t that the problem?” said Spike. “She needs one of her spells to fail.”

“Not the spell! I mean the... the whole...” Dash took to the air. “Nevermind all that. Just make sure she gets plenty of sleep tonight! I’ll be back first thing in the morning!”

“Back?” Spike glanced at Twilight just as the crowd hoisted her into the air and carried her along. He looked at Dash. “Back from what?”

Dash called back as she left, her voice fading out. “I need to find somepony who can build a kayak that can turn into a hang glider!”

Next Chapter: %i%: Twilight solves for X... TREME!! Estimated time remaining: 9 Hours, 11 Minutes