Twilight Sparkle had finally figured it out.  It was so obvious, she couldn’t believe she hadn’t seen it before.  Time travel was so SIMPLE.

She thought about the gnarled mass she had made out of the timeline...  Okay, so simple was the wrong word.  But still, Twilight couldn’t help but feel like a foal for not realizing the obvious truth so much earlier.  The Sonic Rainboom generated almost exactly half of the energy needed.  Why had she never thought to use two?  Twilight Sparkle would cast the spell on Rainbow Dash, and Twilight Sparkle would cast the spell on Rainbow Dash.  Then Rainbow Dash would perform a Sonic Rainboom, and Rainbow Dash would perform a Sonic Rainboom.  The spells would gather the energy from both sides, and what was essentially a portal through time would open.

The Dashes would trade places.  The numbers worked.  Everything made sense.  It explained why a pony wouldn’t necessarily appear in the same place they had left from.  They would appear wherever the other side was.  But something tugged at the back of the purple mare’s mind.  She was overlooking something.  There was no way it was really that simple.  There had to be a catch of some sort.  If the only tricky part was gathering the energy, then all it would take would be a large group of gifted unicorns.  Time travel would have been mastered long ago, and anypony could pop into or out of any era they pleased.

That thought only stopped Twilight for a few moments, before the feeling returned.  No, there was something else wrong.  A much deeper flaw was hiding in her theory… but what?

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The little orange pegasus had an unusual smile on her face.  This was not the wide, beaming smile of a child basking in the attention of her idol.  “Hi Rainbow Dash!  Do you have time for a race?”

Rainbow Dash looked around the streets of Ponyville, searching for herself.  She was pretty sure she was nowhere near here right now, and she had nowhere else to be at the moment.  “Sure, Scoots.”

“Awesome!  OnyourmarkgetsetGO!”

Dash had to admit, the speed  the orange blur disappeared with was pretty impressive.  But she was the fastest flier in Equestria, and she wasn’t about to let somepony else win a race.

She stopped cold when she saw Scootaloo standing off in the distance, letting off an exaggerated yawn.  Slowly, she turned around and looked behind her.  There was nopony there.  Turning forward again, she sucked in a deep breath and closed the remaining distance in a fraction of a second.

Scootaloo snickered.  “What took you so long?”

“How did you… I… but you’re just… you were right behind…” Dash turned around again to point a hoof.  She stopped.  Something caught her eye.  Something orange.  Again blasting off at an incredible speed, Rainbow Dash was staring down at Scootaloo before the little filly had a chance to move an inch.  She had been trying to hide in an alleyway, but couldn’t resist peeking her head out to get a look at the action.

“What in the hay… but you’re over there!”  Dash turned back to other orange pegasus.  “How are you…”  The gears in the cyan pegasus head started turning again.

“Did you see me do any Sonic Rainbooms today?”

“YEAH!  It was amazing!”

An orange blur shot across the streets “WHAT?  NO FAIR!  HOW COME YOU GOT TO SEE IT AND I DIDN’T?”  Scootaloo was breathing heavily in her own face.

Rainbow Dash turned toward the outraged filly and put on a very serious expression.  “Scootaloo, you need to go home.  Right now.  You need to stay away from me for a while.”

The filly’s eyes started quivering.  “I’m sorry… did… did I do something wrong?”

“No Scoots, it’s okay.  But I need you to promise me you won’t follow me for a few days.  I’ll come get you and show you a Sonic Rainboom after this is all over.  Right now I need to go and find Twilight.”

“Isn’t she at the library, like always?”

“… It’s complicated.”  Dash turned to face the other orange pegasus.  “Come on, Scoots.  Twilight is going to fix everything and send you home… I hope.”

“WHAT?  I thought you said I needed to stay away from you!  How come SHE gets to go find Twilight with you?  THAT’S NOT FAIR!”

Scootaloo blew a raspberry at herself.  “Come on Rainbow Dash!  Let’s go find Twilight!”

“NO!  That isn’t fair!  Why does she get to see a Sonic Rainboom AND go do more stuff with you while I have to sit at home and not see you at all?  I thought you were finally starting to think I was cool!  We were hanging out and doing cool stuff and we were both having fun!  What did I do wrong?  Am I not cool enough?”

Rainbow Dash turned away from the angry filly and sighed.  “I’m no good at explaining this crud.  Just trust me, everything’s gonna be fine and you’ll get to do all the things you’re doing right now.”

“Huh?”

“Um… okay, how about this.  Scootaloo, do you remember being over there getting mad that you wouldn’t get to hang out with me?”

“Yeah!  It sucked.”

“But now you’re coming with me to find Twilight.  Before, I told you that you couldn’t, but now you can!  Isn’t that awesome?”

“Yeah!”

“So now Scootaloo, listen to yourself here.  You remember that you were here getting mad, but then later you came back and now you get to go with me  So right now you're here getting mad, but later you get to come with me!”

Both Scootaloos tilted their heads to the side and made confused faces.

Dash sighed again.  “Okay, how about HEYLOOKOVERTHERE!”

Scootaloo turned her head back.  “There’s nothing there!”

And there was nothing in front of her anymore either.

---------------------------------------------------

Of course!  The problem was one of targeting!  How would any two Rainbow Dashes be able to trade places with each other when there were so many others?  There was no way to pick which two would be linked by the spell.  Any time she sent Dash back, she could end up trading places with of any number of other Dashes.  There wasn’t even any way to ensure the Dash she was working on was the one going backward and not forward!

She would have to add some kind of seeking to the spell, so that the right connection would be made.  That wouldn’t be too hard, but now it was a question of finding something unique to seek.  Just seeking Dash or some residue from Twilight’s magic wouldn’t work, because ALL of them were Dash and ALL of them would have the same magic residue on them from the spell.  Maybe if she just designed a pile of throwaway spells with different magical signatures and used a different one on each Dash…  That could work, but then how would she know which one to seek?  Any Dash that needed to go forward would need to have her spell tweaked to seek the right signature from the future, but the magical signature was in the FUTURE and there was no way Twilight could know what it was before she placed it herself.

Even if THAT problem were resolved, that would just add one more variable to track in her notes.  As much as she didn’t want to admit it, it was getting to be too much for her to handle.  She would need a simple solution that didn’t require any extra information…

Lost in the invigorating buzz of solving a new puzzle, Twilight Sparkle lost track of the light tugging in the back of her head.  It had weakened, but not disappeared.  Somewhere deep in her subconscious, Twilight continued to pull on a loose thread that was begging to come unraveled.