Twilight sighed. Her schedule for the day consisted entirely of reading her book. It was the sort of book one set aside an entire day for. Well, Twilight did anyway. Most ponies would have taken one look and found something else to do. Anything.

Advanced Thaumatic Field Theory and the Morphic Resonance Principle in Mammals was not typical pleasure reading. She was not in truth, reading the entire book. Instead she was re-reading the five chapter piece dealing with Alicorn magic. Pausing, she checked the cover again, just to be sure Discord wasn't listed as a Co-author, even in the finest of prints. She turned back to her page and dug back in. Until there was a knock at the door. She looked up, and leveled her gaze at the door. Personally she hoped whoever it was would go away. The knock came again. Sighing, and marking her place, she stood and walked to the door. She opened it to find the Mayor outside.

“Hello Madame Mayor, something I can do for you?”

“As a matter of fact Twilight, there is.” Twilight stepped back and extended a wing to invite her in. The Mayor didn't seem at all bothered by her status as a princess, for which Twilight was infinitely grateful. “I was noticing that you and your friends seem to be spending an awful amount of time in the Everfree.”

“Yes, we're exploring the castle in which Princess Celestia and Luna grew up in.”

“Really? Very interesting. In that case, I feel all the more obliged to ask you to take care. I know you do not intend to cause trouble, and I appreciate that. However, I am concerned that some of the monsters and dangerous animals might follow you back.” The mayor paused, carefully not making any mention of the line item in the budget, known as the Monster Repair Budget. It had been fairly small before Twilight came, but it had been steadily growing, fortunately, after a comment from the Mayor, Princess Celestia had allocated some funds for the Budget.

“Oh, yes. I'm sorry, I meant to talk to you about that. We've been taking the proscribed precautions and Fluttershy has worked out a warning system with her animal friends. Most of them report creatures getting restless either to her or to Pinkie.” The Mayor quirked an eyebrow. “Don't think too hard about it Mayor. I don't either. I've also been studying several spells to help ward against the more dangerous creatures.”

“Well, thank you Twilight.” The mayor blinked. “Sorry, I'm just not used to any pony being able to see the potential consequences. It feels like that's half my job sometimes.”

“I know exactly what you mean. Then again, if they thought things through all the time, where would we be?” Twilight smiled and extended a hoof. The Mayor smiled back and shook it.

“Guess I'm glad you're in focus Twilight. I'll let you get back to your reading then.” Twilight showed the Mayor out and closed the door. She settled back to her book for only a moment, then looked around. Light flickered and a pad and quill appeared beside her. An inkwell joined them a moment later. She looked back to her book, the quill taking notes seemingly on it's own. Twilight managed to turn the page before she was interrupted again.

“Twilight!!!” Pinkie screamed, exploding through the door. “You'll never guess what I just heard?”

“Probably not.” Twilight said, knowing that she probably could but that the guessing game would take more time than letting Pinkie come to the point on her own.

“The Star-Swirl the Bearded traveling exhibit is coming to Ponyville!” Twilight perked up.

“Really? How'd you hear that?”

“Threw a party for a pony, who knew a pony, who knew a pony who...” Pinkie saw she was starting to lose Twilight. “Eventually a pony who knew the schedule.” She produced, from nowhere, a copy of said schedule, with the date outlined in pink highlighter.

“That's the day Cadance is going to visit. That's perfect.” Twilight smiled, and flashed her schedule down. She made a notation in it, and then sent it back. “We can spend the day looking at the exhibits. Thanks Pinkie.”

“My pleasure Twilight.” Pinkie glanced at the clock. “Oops, gotta go get the muffins out.” And she simply vanished. Twilight focused and the door swung shut. She turned back to her book, one ear cocked for further interruptions. A polite knock at the door very nearly missed her attention. She paused, but it did not repeat. For a moment she started to go back to her book, but as often happened, curiosity got the better of her, and she stood up. The knock hadn't repeated because the knocker was walking away. Robert and Rainbow Dash were in animated conversation when the door opened, and they looked back.

“Can I help either of you?” Twilight asked.

“I was going to see about a book, but Dash said it was your day off.”

“Now you've done it.” Rainbow stood on her hind legs and put a hoof over her heart. “Now she'll be talking about them all day.” she pretended to faint backwards, wings flapping gently to catch her. Her tail hung down, and Robert couldn't help himself. He reached out and batted at it, sending her spinning through the air sideways. “Whoa!” she righted herself after a minute. “That was... pretty funny. Of course you know this means war. Prank war that is.”

“Bring it on. I learned from some of the best.” Robert said, and stretched out a paw. Dash grinned and reached out with a hoof. Twilight opened her mouth to warn him, but he grabbed Dash's hoof. The joy buzzer turned him into perhaps the fluffiest ball of fur Twilight had ever seen. Of course, as Dash laughed, his tail reached out and brushed against her.

“Not bad, not bad. We'll just see what else you can concoct.” Robert said.

“Oh you will.” Dash said and turned. As she did, Twilight had to hold a straight face. Affixed to the cyan Pegasus was a sign, reading: 'Bolt me.' She disappeared in a rainbow flash.

“You know you've opened a can of worms, right?” Twilight asked, as she motioned Robert inside.

“I am aware. I had a talk with Fluttershy the other day.”

“Fluttershy? Really, where?”

“In the Everfree.” Twilight blinked. “I was gathering ingredients for potion making and she was there checking up on the animals. We talked while she helped me find some of the flowers I needed and I helped her with some of the less docile animals.”

“I always forget that she lives near the Everfree for a reason. She's just so...”

“Careful?” Robert asked.

“Why careful?”

“She's mighty strong.” Twilight's eyes widened. "You didn't know?”

“No.”

“Oh, yes.” Robert nodded. "We ran into a bear with a sore tooth. She had me hold it's paw while she dug out the piece of fishbone in it's mouth. It accidentally bit her, and she hit me reflexively. When I came to, the bear was holding my paw. I've been hit by Waterbuffalo, and she hit me harder than most of them. Of course, it took ten minutes to get her to stop apologizing.”

“Yeah, that's Fluttershy.” Twilight said. "I wonder if she's always been that strong?”

“Haven't known her that long, but I did know someone like her who was very strong and tended to... overcompensate was the word my mentor used. He accidentally hurt someone when he was little and spent years trying very hard to avoid it, so he eventually seemed to be weak. Of course, since his name was Bends-steel, it wasn't exactly a secret.”

“Right, anyway, Rainbow Dash?”

“Oh, right. Fluttershy spent most of her time talking about you guys, and she said the best way to win Rainbow Dash over was to fly or play pranks. And despite my Svelte frame, I'm not going to be flying anytime soon. So pranks it had to be.” he shrugged.

“Why can't you fly?” Twilight asked, pushing the door closed behind her.

“Do you want the scientific, or the magical explanation?”

“Both.”

“Naturally.” Robert nodded, and then looked to the blackboard. His eyes glowed faintly as several pieces of chalk sprang into motion, drawing several figures and expanded blow ups of several parts. At the end the chalk scrawled along the top: 'Comparison: Tiger and Pegasus Musculature.'

“Very nice. Faithful rendition of Hoofnardo's Vitruvian Mare.”

“Thank you. Never could understand what he did with the shoulder there. It always looked wrong to me.”

“Neither could I.” Twilight confessed. "Nor could my teachers. Eventually I had to ask Princess. Celestia about it. As it turns out, he did this.” she snagged a piece of chalk and drew in the lower corner. She was no professional artist, but she surpassed Rainbow Dash. "The muscles look wrong there, because the leg is drawn rotated ninety degrees. Most ponies can't turn that much so the muscle doesn't look right.”

“How did she know?” Robert asked curiously.

“It would seem she was the model. From her blushing, I suspect that's not all she modeled for.” Twilight winked.

“Ah, well. Anyway, If you look here, at the musculature connecting the wing to the rib cage, you'll notice a vast number of structural ligaments, enhancing the ability of the muscle to flex and apply power without ripping off the bones. Or tearing the muscle, especially with this ligature bundle here.” The bundle he indicated ran down the middle of the muscle.

“Got it. I've seen a lot of this... in a personal project.” Twilight thought about Scootaloo. "So where's the problem?”

“Over here.” He pointed to the tiger. "You'll notice here that the same musculature connection ligaments are already connected to the muscles here and here, used for...” he paused, framing his words.

“Rending and tearing while attacking. Giving an enhanced range of motion to the attacks you can deliver.” Twilight filled in.

“Yes.”

“I'm not squeamish, nor am I bothered the way Applejack is.” Twilight shook her head. She indicated with a hoof for him to continue.

“Anyway, when I change myself to grow wings, I don't have the option to attach to the wing muscles too, so even though I can glide, actually flying is out of the question.”

Twilight nodded, then did some math in her head. “According to this, technically a Pegasus shouldn't be able to fly either.”

“Indeed. And that's where the second part comes in.” the board started to flip. Twilight put a hoof out to stop it. He blinked just once and then nodded. He erased the board, and began writing. This time it was not a drawing, but an enormously complex magical equation. It ended in several magical runes. Twilight worked her way through it. Halfway through, she muttered something.

“Star-swirls incomplete theorem?” she said it to herself. As she reached the end, she looked at him. "You solved it?”

“No. However, I substituted Night-shadows morphic resonance corollary for Star-swirls. It doesn't completely solve it however. You'll notice here, that the alignment isn't quite right. The two theories don't match up. At least not exactly. There are attempts that have been made to bridge the two. None successful to my knowledge. However, it serves to illustrate the point sufficiently. Pegasus magical talents allow them to utilize the scattered background magic to overcome the difficulties in the square-cube law upscaling effect making it impossible for a pony to fly using that small of a wing span.” He pointed to a section. "This is the relevant section.”

“Very interesting. So what does it mean?”

“I no can has fly.” she blinked at him. "Even with an understanding of the mechanics of flight and the magical equations required to necessitate flight, I lack the inherent ability to express the magical power while also maintaining the transformative effect used to grant wings. And finally the ability to attach muscles strong enough to maintain flight, even should I be able to utilize the flight magic.”

“So no flying.”

“Right.”

“Something's off about this equation.” Twilight looked at the board, and tilted her head. "Did you add those runes?”

“No. They always appear when the equation is expressed.”

“Then...” she picked up a piece of chalk and an eraser and changed a number. The runes shifted. It still didn't look right. She changed another number. Robert watched for a moment, then changed a number himself. The runes shifted again.

“That's not...” he muttered. More chalk and erasers. More muttering from the pair. When Spike came back, an hour or so later for lunch, he saw the two of them sitting and staring at the board. Several pieces of chalk and erasers were hanging in the air, suspended by orange or purple magic. Every few moments, purple glowing beads would flick back and forth across an abacus. Then a number would disappear and be replaced. And each time the runes would shift. Spike opened his mouth to ask if they were hungry, when light flashed as the runes changed one more time and flared into a single rune. The chalkboard floated up into the air. Twilight nodded.

“So, it turns out that Star-swirl had the right idea, but he didn't have the proper implementation.” Twilight mused. "When does Night-shadow date from?”

“About two hundred years after Star-swirl's death. Plus or minus about two decades. There was still a lot of oral tradition, and calendars weren't terribly common.” he rubbed his chin. "I'm a little surprised he knew about Star-swirl's theorem. Everyone knew about Star-swirl, but things like this weren't usually published outside of their points of origin.”

“True, although records indicate that after leaving his post as Court Wizard to Princess Platinum, he traveled extensively, which might have led him into the lands of the Tigers.” Twilight thought for a moment. “And as potent as he was, I doubt he'd have problems avoiding becoming lunch.”

“Indeed. Perhaps we should write the new equation down.” Robert suggested.

“Yes, I'll get, oh, hello Spike.”

“Hello Twilight. Ummm... why is that floating?” he asked, slightly concerned.

“Oh, we were working on Star-swirls unfinished theorem, the one about Pegasus flight.” Spike nodded.

“The one you did the twelve page research paper on? Yeah, I remember that one.” Twilight blushed. While they talked, Robert had grabbed hold of the floating chalkboard and was convinced it was getting closer. It was, but because he was now several feet in the air.

“Spike can you get some paper and write this down?” Twilight indicated the board, then turned to Robert and looked around. "I thought you couldn't fly?”

“Huh?” The revelation was followed by a sharp thud. "Ow.”

“Twilight, get ready to catch.” Spike said. He picked up an eraser and took careful aim. Twilight opened her mouth, but the eraser was in flight already. It hit the equation, and broke one of the runic marks, breaking the spell. The board fell a half a foot before Twilight caught it.

“Nice work Spike.” Twilight smiled. Spike set to work copying down the equation, careful to annotate the error he'd created and mis-align the correct symbol. "You okay?” she asked Robert.

“Nothing injured but my pride.”

“You could probably fly you know, now that we've completed the theorem.” Twilight offered.

“Probably, but I'd rather not. I'll leave the wings for those meant to have them. Besides I've got enough to learn without adding flying to the list.” he stood and stretched. "Besides, it might only work as an inscription, instead of a spell, which might be helpful for lifting inanimate objects, but not something I want laid into my hide just to fly.”

“Good point.” Twilight paused. "Didn't you originally come to borrow a book?”

“I might have, but I'm not sure what it was. I'm certain I'll remember it eventually. However, since I have the whole day off, I'm thinking I might get lunch.” His stomach rumbled and Twilight's did as well.

“Sounds like an excellent plan. How about you Spike, you hungry?” the small purple dragon's stomach rumbled. "Guess I don't need a translation huh?”

“Nope.” Spike grinned. "I have an idea.”

---

Not long after, the three of them were sitting outside in one of the many cafe's in Ponyville. It wasn't a normal burger shack. In fact it was one of the few restaurants in town that catered to non-pony tastes. Spike was munching on a bowl of quartz, while reading a Power Ponies comic. Twilight had a big stack of hayfries, and a salad. Robert was eating fish. Spike was trying hard not to mention how good it smelled. Twilight was trying hard not to smell it at all.

“So, Power Ponies eh?” Robert asked.

“Yeah, they're awesome.” Spike said.

“What issue are you on?”

“Seven.”

“Power Ponies versus the Indomitable Iron Griffon.” Robert grinned. "Very interesting issue. Keep an eye on the backgrounds. Trust me.” Spike raised an eyebrow, then nodded.

“Comics, really?” Twilight asked. “Aren't those books without imagination?”

“Bah. Says a literature nerd.” Robert laughed. "Reading is reading isn't it?”

“I guess. It just seems....” Twilight shrugged.

“Silly.” Robert chuckled. "Don't worry, I've heard it before. Some get it in their heads that just because it's got pictures it's not as good as one of the classics. But really, they take just as long to get through an arc of story as the classics. True, you might not work as hard to imagine the entire thing, but there's still a lot to be imagined.”

“I don't have anything against comics, I really don't.” Twilight said.

“Sorry about that. I'm used to having to defend them to everyone.” Robert sighed. "Just something that bothers me. Probably the same thing you get when people rag on the classics.”

“Oh. Yeah, I see what you mean. I...” Spike's sudden bark of laughter cut her short. He pushed the book over for her to look at. She scanned the page for a moment, then blinked. In the background of the scene of the Power Ponies and Humdrum taking on the Iron Griffon, was a familiar alicorn shape. Dark blue. And being chased by what appeared to be angry white rabbits. Mistress Mare-velous head was obscuring her cutie mark, but Twilight was certain it was intended to be Luna.

“I wonder if she knows?” Twilight asked, smiling.

“It usually says inside the back cover when they have a guest star, or cameo.” Time Turner said, walking by. Twilight levitated the book and opened the back cover.

“Special appearance by Princess Luna, 10% of all sales proceeds going to benefit ponies displaced by the Plundervines.” Twilight read. "Guess she does know.”

“Guess your lesson about it being fun to be scared stuck.” Spike said, taking the book back.

“I wonder if I'll ever end up in one?” Twilight asked.

“You never know.” Time Turner wandered back the other way.

“Who is that guy?” Twilight asked.