Magical Theory

Ditzy and The Doctor cheered with the rest of the crowd as the Wonderbolts flew overhead. “They’re incredible fliers!” Ditzy remarked. The Doctor smiled, calling back to old memories of the Earth air-shows humans would put on in their planes. “They are!” The Doctor agreed over the roars of the crowd as another trick was performed. “It’s incredible how they can stay flying doing all those things!” Ditzy commented, ‘ooh’ing with the others as the Wonderbolts performed another daring feat, accompanied by a lightning cloud this time. “It’s remarkable to me they can fly at all! Or that any of you can!” The Doctor retorted. “Pegasi wingspans are far too small to give the lift they need to get you lot off the ground,” The Doctor whispered to Ditzy, leaning over to her so she could hear.

“Doctor, it’s magic! Same as Unicorns can levitate stuff, Pegasi can fly and walk on clouds,” Ditzy responded in a matter-of-fact tone, her usual bubbly tone coming through as well. The Doctor could tell you every star single system in the sky, but he still hadn’t figured out how to walk on three hooves. Ditzy liked that about him – she felt it was ironic in a way.

“Well then, my dear Derpy, would you care to tell me what I can do with my oh-so meager Earth Pony body?” The Doctor joked in a mock-up ‘posh’ accent, using Ditzy’s nickname. Ditzy giggled, and The Doctor smiled back. The Doctor always knew when it was right to joke.

“We’re… still trying to figure that one out,” Ditzy admitted, scratching slightly at the back of her neck and managing a meek smile. The Doctor saw the humor in the situation – the most common species still had no idea how they had gotten to be where they were. They reminded him of humans in that way – maybe that was why he liked them. He’d tried a few different forms with the chameleon circuit, but found he liked Earth ponies best (though Pegasi were a close second – flying was ace!).

Though, the question did bother The Doctor a little bit. How did Pegasi fly? Magic had never been a good enough explanation for him – he’d put some thought into it.

*    *    *

“I’VE GOT IT!” The Doctor screamed, running across the Ponyville gardens to meet Ditzy. “I’VE FIGURED IT OUT!” he cried, leaping over a bush to shorten his trip.

Ditzy gave an amused smile, and then shook her head. The Doctor hadn’t grasped the concept of subtlety, especially as he hadn’t gotten the concept of having a semi-permanent residence; well, to others, he appeared to be a permanent resident with a busy work schedule – but in reality he and Ditzy often spent weeks away on other worlds, or in other times. They just returned to around the time they had left. “But hey,” Ditzy thought. “At least he doesn’t materialize the TARDIS next to you anymore!”

The Doctor quite literally skidded to a halt next to Ditzy. “Derpy I’m a genius!” The Doctor announced, beaming. Ditzy giggled – he was always was his zaniest when he discovered something he didn’t know. Which was surprisingly often in Equestria. Ditzy smiled at The Doctor, whom was plastered with his own joy. "What have you found out Doctor?" Ditzy asked.

"I've figured out how Pegasi fly!" he declared, his grin widening. Ditzy moved onward, heading towards town with The Doctor in tow. "Go on then Doctor - how do we fly?" Ditzy indulged him.

"Well, back on Earth we have a creatures like songbirds and hummingbirds," The Doctor began. Ditzy was about to interrupt him, but The Doctor answered her question in his usual tangential manner before it was even asked. "Well, you guys have them here too but they're grossly disproportional; anyways," The Doctor shook his head to clear his thoughts and get back on topic. "But yeah, they exist on Earth and are about this -" The Doctor was about to show how large a hummingbird on Earth was by making a small hole with his fingers - then quickly realized he had no fingers. He sighed at the difficulties of adapting to an Equine body. "About the size of my eye" The Doctor concluded, remembering the larger size of a pony's eye in this universe. "And the hummingbird's wingspan is too small to get it off the ground; but," The Doctor grinned as he got to his realizations. "They do everything they can to conserve weight. So, I thought about what the hummingbird did and how it could apply to a pony. The Hummingbird, like most birds, has nearly hollow bones - they have a sort of honeycomb shape to keep them strong so their bones don't break at the drop of a hat," The Doctor rambled.

Ditzy simply nodded, and looked over to the pear stand. She could go for some pears.

"So, I looked into it at the Library - as it turns out, Pegasi may well have honeycombed bones or something similar - it means you break your bones easier, but considering you work with clouds for the most part, it's a good evolutionary step," The Doctor continued, following Ditzy wherever she went. "But, the main reason a hummingbird can fly is because of the figure of eight shape it makes with it's wings - that's what gives it the illusion of the 'wing blur' -" The Doctor said, now turning to keep up with Ditzy's walk around the market. "I hate pears," he noted, making a disgusted face then resuming his rambles.

"But, I know Pegasi don't have that - I've seen them fly often enough. So, I went a different route," The Doctor paused, attempting some suspense. "The air we breath. Oxygen, which is what things rely on back on Earth, is kind of heavy - well, as far as gases go. But, another gas that one could use to breath is Hydrogen - it's a bunch lighter than air, so it would make sense," The Doctor concluded. "Hydrogen is much less dense, but Equestria is a far smaller planet - hence why the entire planet consists of more or less one continent - so it's atmosphere is thinner; because of this, Hydrogen can - at a very simplified level - take the place of Oxygen."

Ditzy hummed an agreement. The Doctor was wonderful and fantastic and completely and utterly bucking crazy, and for that Ditzy enjoyed his company, but he got so excited at the most trivial things. Now, where did she leave her bit purse...

"It would also explain why Dragons can breathe fire - Hydrogen is combustible, so if they have some form of ignition - like, say, grinding flint against their teeth - would ignite the Hydrogen, causing them to breathe fire! Well, appear to breath fire. Well, appear to breath combusted Hydrogen. Well..." And so The Doctor continued with his own caveats.

Ditzy thanked the stall owner, and turned to face The Doctor.

"So Doctor..." Ditzy began, containing the smile that wanted to creep over her face. "Pegasi can fly through a combination of breathing Hydrogen and having bones like a hummingbird, right?" The Doctor nodded. "Yea, basically," The Doctor responded. Ditzy was unable to contain her smile. "Then, if hummingbirds are so 'grossly disproportionate' Equestria, how do they fly?" Ditzy asked.

The Doctor was dumbstruck as he watched Ditzy leave.

"I hadn't thought of that..."