PLAN TO PROVE THE IMPOSSIBILITY OF TIME TRAVEL (BACKWARDS IN TIME)

1. General Remark. Time Travel is Not Scientifically Possible.
2. Observation. In spite of (1), I was visited by Myself-From-The-Future just before the Disaster-That-Never-Was, and then travelled back in time to try to tell myself there was nothing to worry about.
3. Further Observation. Had I succeeded in (2), this would have been impossible as I would then not have travelled back in time.
4. This is not scientifically possible (see 1.)
5. Postulate. Was that Me not from my future, but from some other future in a Parallel Universe?
6. I did not succeed in (2), but ended up creating the very thing I was trying to stop. Hence (2) did not prove anything whatsoever.
7. Therefore. To prove this, I need to show that time travel creates a logical impossibility.
8. Obstacle. I can't do this as the spell only works once. I need a friend who can work magic and pays attention to details. That is, Rarity.
9. Action. We wait two minutes. If nothing happens, go to step (10). If we are visited by Future Rarity, go to (11).
10. Rarity travels two minutes back in time to greet herself. This is impossible as she didn't see herself two minutes ago.
11. Rarity does not travel back in time. This is impossible as we just saw her.
12. Either way we have created a logical impossibility and thus proven (1).
13. Note. To ensure scientific integrity, we must follow the plan and not be distracted by anything such as Rainbow Dash crashing through the ceiling (conduct experiment during nap-time to minimise risk). Likewise if any friends stop by, or if Ponyville is attacked by a monster, we must ask them (politely) to wait two minutes until we finish the experiment.

Twilight read out her plan in a proud voice. “Is everything clear?”

“Not exactly,” said Rarity. “But I see what you want me to do.”

“Okay... So, two minutes, starting from now.”

After sixty seconds, a second Rarity appeared with a flash of light.

“Rarity, you've got to listen to me!” said Rarity.

“Well I never. It's me. Oh my. Oh I really like how you did your eye-shadow—I mean, I did—or, I will do—it really accentuates the beauty of your irises—or is it my irises? And where did you get that beret?”

“It's from the Cheval Chapeau boutique on Manefair in Canterlot. But that's not important!”

“Hang on,” said Twilight. “Why are you wearing a hat? You're from two minutes into the future. You haven't had time to change your attire.”

“Actually I'm from next August.”

“What? But that messes up the experiment!”

“Well I had to come back to this particular minute, otherwise I would waste my one shot at time travel on your experiment. Now I've only got a moment and I have an extremely important message from the future, so please listen to me Rarity—full length pleated skirts, crew neck jackets and triple-puffed sleeves are the thing this season.”

“Puff sleeves!?”

“Hoity Toity has done his entire line this way. Photo Finish can't get enough of it. It's all Canterlot is talking about. Rarity—you have to follow this—it's the biggest new look in a generation—if you start now you can ride the wave—you must—”

With a flash of light, Rarity-with-a-beret was sucked back into the future.

“Urgh!” Twilight stomped a hoof and gnashed her teeth. Grey smoke drifted out of her ears. “You messed up the experiment!”

“What did I do?” said Rarity.

“I mean—you will do,” said Twilight. “Don't you see—even if you don't go back in time now, it doesn't prove anything as the Future You came from next August! Hang on—” The smoke stopped and she started smiling. “We can still do it. We can create a logical inconsistency if you now go back to just-before-she-arrived! We didn't see you then!”

“I thought you said we had to follow the plan and not be distracted by anything?”

“Yes... But... Aargh—why do experiments never go as you planned?”

“Twilight...” Rarity placed a hoof on her friend's shoulder. “I think we now need a nice trip to the spa to relax. And anyway, I would say that proved your theory very well.”

“How?”

“She was obviously a visitor from some strange parallel universe with a very odd taste in fashion. You heard what she said—triple-puffed sleeves? Really?.. But I did like her beret. I shall have to visit that boutique.”