After nearly a month of effort, Twilight and the team of scientists finally have a plan, and she's standing with Rainbow Dash on the statue at the center of the park. It seems a fitting place to start the long flight that will, if all goes well, give her human friends a second chance at responsible atmospheric management.
In the end, she found their solution pleasingly elegant, and not so dissimilar to her joking suggestion about banishing the greenhouse gasses to the moon. Where Earth suffers from an overabundance of them, her closest neighbor, Mars, suffers from a distinct lack - at least from the perspective of liquid water and therefore life. Twilight's spell aims to transport the extra gases there. The scientists aren't sure if it'll be enough to restore blues and greens to the red planet, but they're sure it couldn't hurt, which seems, overall, an improvement on the status quo.
"Are you sure I can't come?" Twilight hears Mary ask Rainbow Dash.
"It isn't safe," Twilight answers first, "we have to fly near the edge of the atmosphere to make sure enough of the pollution is below us. Pegasus magic keeps us safe from the cold and lack of atmosphere, but we won't have the energy to spare to share it with you. You'd suffocate and freeze, probably in that order."
"It's okay." Rainbow gives her a peck on the lips, "thanks for offering. Don't worry, I'll let you ride me for hours later." She winks, and Twilight turns away, blushing, though not as furiously as Mary.
"Good luck, Princess," Polaris says, strapping the last of the equipment on her. A little of it is designed to measure levels of various gasses, making sure the spell is working, but most of it is to let the scientists watch and film their progress for posterity. Rather than making a spell to remove some percentage of the pollutants, they decided it was easier to simply remove all of them from an appropriate percentage of the sky. As such, Rainbow and Twilight plan to make several circuits of the planet over some of the more densely inhabited or heavily polluted areas, letting the atmosphere itself take care of balancing the situation out.
With a nod to Rainbow, then another and a smile to the assembled crowd, Twilight takes to the air. The pegasus follows shortly, then surges ahead. As they clear the tallest buildings, Twilight speaks into her headset, clearing them with Logan airport. After getting the all-clear, Rainbow pours on the speed, and her characteristic prismatic wake trails out behind her.
Twilight can't fly as fast as Rainbow Dash on her own, of course, but she can tether herself to her friend's magic, riding her wake like a cyclist following a truck. It's only part of the spell, of course, but it lets her ride along without too badly straining herself, and lets her concentrate on the real bulk of the magic. They clear the target height, and she can feel the magic flowing through her into Rainbow, and into her magic's wake, seeping down into the atmosphere below, working as intended. She hears the excited chatter of the scientists watching the cameras and instruments, but tunes it out - she can tell from the tone everything looks good from their end, and she wants to focus on keeping up the complicated magic for the several hours it will take to circumnavigate the earth on three separate routes, even at Rainbow's impressive speeds.
For once, it goes off without a hitch. Throughout much of the world, people stop and stare at the sky, thrilled by the solid band of rainbow running clear across the sky. Those that watched the news know what it is, while others can only wonder, but it's certainly like no rainbow they've seen: they can watch it pass across the sky, like the work of an invisible paintbrush.
Even riding Dash's magical wake, Twilight's wings are sore by the end of the trip, and her legs are tingly and asleep. As they intersect their own wake above the park in Cambridge, Rainbow sighs, and heads for the ground. Twilight feels elated, though, despite her fatigue, and, laughing, she soars a little higher, relishing the feeling of the sun on her wings, bright in the thin air above the clouds.
Then, with a start, she feels herself breaking through...something, some barrier that feels like the surface tension of water, but leaves her dry, and she's in another world entirely, flying above a crystal sea, filled with coral and fishes. Above her is a perfect clear sky, lit by a silver sun. In her bones and horn she feels home keenly, though she has no idea where she is.
In shock, worried about unintentionally abandoning her friends, she falters, and falls to the surface of the water. Instead of the expected splash, though, she passes again through that strange barrier, and finds herself recovering back in Earth's yellow-lit sky. She takes a few deep breaths, then follows Dash down.
"Girls," she says, finding them all clustered around the pegasus, "I think I figured out--"
She's interrupted by a burst of laughter from Pinkie and Applejack. Rarity and Fluttershy just look confused.
"Check it out, Twi," Dash says proudly, brandishing her tablet. It shows her newest Facebook post, a photo of herself coming down, wake trailing, apparently taken by someone in the park. It bears a caption: Good news! We just made your planet 20% cooler!
"Rainbow! Did you really use that awful catchphrase?" Rarity asks. Rainbow nods, grinning.
"That's terrible," Twilight frowns at her. "Besides, we didn't make it 20% cooler, that would be a disaster, they'd have an ice age! You'll scare them! Anyway, I have way more important news!"
Everyone looks up at her, eyes wide.
"I think I found our way home."
I'm back from BronyCon! I had tons of fun playing the CCG and our team placed 3 people in the top 4 of the big tournament, including both the finalists. Glad to be back to writing, at least for a few days - I'm running events at a local con this weekend, so it's likely to be another break for that, sadly. Still, getting close to the end now. Thanks for reading as always.
...ooooh. A permanent two-way gate, I'm guessing?
Perhaps now they'll find out why they went to Earth in the first place, as well...
Honestly the best way to terraform Mars is with cockroaches, moss, and a lot of time. Magic, psh. Read Terra Formars if you don't believe me. Everything goes so well with that plan.
4808424 They aren't necessarily planning to do that, they just figured they had to put the stuff somewhere, might as well try to get some value out of it.
I considered things like having her try to turn it into various kinds of manufactured goods, but since greenhouse gasses aren't just carbon, and the actual material responsible is widely dispersed, it was going to be complicated and boring to figure out just what the vaguely believable possibilities were. So I decided instead that the scope of the magic meant reshaping it wasn't realistic, just moving it, at which point you're clearly going to dump it somewhere extraterrestrial. Mars is a pretty good choice; it seems like people aren't entirely sure how much you'd need to make liquid water a possibility, since atmospheric science is so complicated, but it clearly isn't going to do any harm from that perspective, so might as well (assuming the distance and targeting isn't a major issue, but Twilight strikes me as the kind of nerd that would be totally happy doing those kinds of calculations).