"Can you do things like conjure for the results a conjuration would have for another person if they tried it, or is that too nested for the magic to work with?"

"This is not known to work - the cases it's been checked for involve private information of other kinds than 'faeries exist' but only generate distinguishable results if some private information is involved."

"Hmmm. All right. - any distant planets that do have vegetation?"

"Too distant to reasonably get to unless you can fastify spaceships and also want to spend a longass time on them."

"Not my first idea of an entertaining activity but we have a million years so - how long exactly?"

"We could go to Tau Ceti's system but it'd take about forty thousand years."

" - so, spaceship fast, any fairies on it slowed down."

"Do you have any reason to believe being on a fast vehicle while slow won't just paste you?"

"No. No one's tried changing whether they're fast while on something that's moving, not that I know of, except in the sense that the earth is moving. But you could test it safely enough with a big slow-moving wagon. I think."

"Since slowing down is gradual I guess you could."

"But it's certainly not something you could get all fairies to do even if it works perfectly so it can't be the answer to the mystery of where all the fairies are."

"Yeah, doubt it. And someone would have noticed if I'd made a planet or terraformed one with plants."

"Even if it was far away?"

"They might miss one in another galaxy, I'd have to look things up to know."

"Oh well."

"Oh well is right."

"Is there a reason you want to shoo us away from Earth, or is it just that you feel like since we apparently do leave some day it'd be better if that were under our own power?"

"The latter, I'm worried Earth gets inhospitable or something. But I'm not sure my reasoning here isn't screwy, it's hard to think about the implications of time travel."

Nod. 

"It's definitely more cultivated and built up in the future. Also I guess something random like carbon dioxide could affect you badly."

"I should probably -" he waves someone else over. "What's carbon dioxide?"

(He comes over to listen).

"It's the stuff animals exhale as a byproduct of respiration."

"And it changes a lot in the next thousand years?"

"There's more of it; it's also a byproduct of some transitional fuel use, and plants which usually soak it up become less numerous."