Twilight Sparkle
"Oh stop worrying so much Spike!" I said, triple checking my calculations. "This is a tiny, simple spell and I've used time travel magic before."
The dragon winced.
I sighed. "Okay, so my past experience didn't end all that well, but even then no one was hurt. And the time line corrected itself so there doesn't seem to be much of a chance of paradox occurring."
The little dragon didn't look convinced. "That was going backwards in time." Spike noted. "You've never gone forwards in time before."
I considered explaining to Spike that I went forward in time every day at a rate of one second per second, but realized that that wouldn't be very reassuring.
Instead I put my hoof on his shoulder. "Spike, I've triple checked the calculations. I'm only going 16 seconds into the future. It's an infinitesimal amount of magic energy. Sweetie Bell could do this spell."
His eyes bulged. I could practically see the visions of terror the 'Cutie Mark Crusaders Time Travelers' would cause.
I wasn't batting a thousand on comforting speeches today.
"Look," I said, trying a different tactic entirely. "I know you get nervous when I test new spells, but I'm the Alicorn Princess of Friendship, I've done way more dangerous things before... and not always for such noble reasons."
He raised an eyebrow. "Noble reasons? You're just testing the spell because you thought it was interesting!"
I shook my head. I needed to explain this more carefully. I looked around my study for a good example. In the old library I would have had it in seconds, but the new castle was still confusing. I settled on a candle from the desk. "Spike do you know what this is?"
He blinked. "Uh... A candle?"
"This," I continued, "Is an innovation. There was a time when the only light non magical ponies had at night was Luna's starlight. Then came fires, But they were dangerous, too difficult to control and too smoky to use in confined areas. Eventually somepony very smart realized that wax could fuel and contain a small fire at the same time, it lit up classrooms and art studios..."
"Late night pubs?" Spike suggested.
I rolled my eyes. "Look, the point is, understanding the world helps us to make things that make the world a better place. To do things we could never do, and even do things that we could do before better! Candles look like they're on the way out, soon to be replaced completely by those new, more efficient light bulbs. They've already taken over Manehatten and I think Ponyville will be wired up pretty soon too."
I stood up tall. "But leaps forward like that don't occur without ponies like me working to discover them. The future is going to be a better place Spike, but not because we sat around doing nothing. Tomorrow will be brighter because we were here to make it so!"
Spike paused. He looked utterly astounded. "Wow... That was really rehearsed."
I blushed. Okay, so maybe I'd written that out a few times.
"Look," I said, "The test is safe."
The dragon shrugged. "Humor me." He said. He went over to the nearest window and started rooting around in the gutter.
I tilted my head, confused. "Spike, what are you doing?"
"Getting you a better test subject than yourself." He produced a leaf encrusted acorn and plopped it on the floor. "You want to send something 16 seconds forward in time? Go right ahead. It's even alive if that's important."
I blinked. "I... I guess that could work. I... I actually don't know why I didn't think of it."
The dragon shrugged. "As an added bonus you get to hang out with me for an extra 16 seconds of my awesome life."
I rolled my eyes. "Rainbow Dash is a terrible influence on you. Do you have the stopwatch ready to check my calculations."
He held it up.
I smiled. "Alright then, let's get started..."