"Yeah, could be either or both."

Shrug. "I wonder what else is like that - differences between our worlds that aren't obvious until you run into them..."

"I mean, the physics thing will have all kinds of implications."

"Like what?"

"Maybe electricity wouldn't work here, or airplanes wouldn't. Mountain climbing must be easier if the air doesn't get thinner - maybe mountains don't usually have snow on top -"

"Many of them do!"

"Even in places that aren't cold?"

"I don't remember offhand, but we could probably manage to look it up..."

"It's not terribly important. I think at home it has to do with the thinner air though."

"Huh. I'm now tremendously curious what all the other worlds are like..."

"You can see why I wondered why there wasn't more contact with them!"

"The practical and ethical difficulties remain but maybe I'll sink the time into inventing a random transworld scry with some reasonably sensible targeting constraint - 'wide-angle view of a population center' or something. There's probably a good reason why those aren't already in widespread use but I bet it is a circumventable reason."

Giggle.

"I find that with effort and ingenuity most things are circumventable!"

"What have you circumvented so far - the age limit on the scoot racing -"

"I wasn't technically circumventing anything by getting my wizard certification in my early sixties, but they really don't expect kids at that equivalency to go to the first wizardry school that will take them and then spend the next several years doing almost nothing but study magic and pass tier tests. I haven't looked up if I was the youngest person in history to get the credential, but I might've been."

"Ooh. You'd think that would be the sort of thing someone would tell you, but maybe not."

"It's also possible that I found it out at the time and then forgot, it having been over a century since then, but I feel like that's the sort of thing I'd remember knowing, you know?"

"Yep."

"How would you design a world, if you had the opportunity?"

"Ooh, good question. I'd start with my normal physics, I think, they're a nice baseline - maybe I only think that because I haven't studied the advanced stuff, perhaps they get horrible, but I like the gravitational constant being a thing."

"It is tidy. And I get the sense it's better-understood than the Elcenian scheme, which seems like it'd be important once you start tweaking things from the extant version. I'd hate to say 'planets should be arranged in a predictable grid relative to one another' and then find out that that's the condition under which the fire of the suns consumes all the air in the universe. And designing your own functionality-of-a-world from scratch would involve making a lot of explicit decisions about edge cases. For example, if I went that route, I would be sure to note that there are no conditions under which the fire of the suns consumes all the air in the universe."

She giggles. "And then where would you be? Holding your breath and much too warm, I guess is where."

He cracks up.