"Yes it is."

"That is so cool. Have you been to the Moon? I heard Muggles have been to the Moon but I don't see how they could have done."

"I've been to the Moon! But I haven't actually flown there in a spaceship, and it wasn't actually the moon in this world, I got there by magic and it was the moon in the universe I'm from instead. Nonetheless it is true that it's possible to get there without magic and it has been done."

Now the kid has eyes like saucers. "Wow! How did they do it?"

"The kind of magical creature I am is pretty easy to move around if you know how but I need to do some groundwork before I can teach people."

"Can you teach the nonmagic way? Witches should be able to do it if muggles can."

"I'm not sure that's true, Hogwarts disrupts a lot of electronics and I don't know if exposure to witches and wizards can do the same thing at high enough doses, but in principle, sure. Once the Statue of Secrecy's out of the way, anyway, someone would sure notice a lot of shuttles flying around eventually - mine's cloaked and I surround it with clouds when I go places but in larger numbers that doesn't scale well."

"And they wouldn't think they were Muggle shuttles? Oh, right, because you're from the future. So how does the shuttle stay up?"

Does she want a physics lesson because that's how you get a physics lesson.

She absolutely wants a physics lesson. She asks a dozen follow-up questions and says "oh wow" a lot and clearly thinks Cam and/or rocketry is the coolest thing since sliced bread.

Adorable. He will send her off with a physics book once he has a good idea of her level of understanding and interest.

She has the interest of someone who really loves science and the understanding level of someone whose last science class was years ago. She thanks him and skips off to show all her friends the textbook.

A week after Gringott's said they would get back to him in three business days, Cam gets an owl requesting a meeting as soon as possible. It's signed by the goblins' deputy ambassador to the Ministry of Magic.

Goodness. He can hop over via the stupid fireplace-based transit method rather than suffuse Britain with more clouds than it has already and pop up quite promptly.

This time the cart-ride is much longer, going at least twice as deep by a route so twisty it's practically impossible to tell which direction they've gone on net other than "down". The cart arrives at a little underground train station shared by similar carts and larger, more nicely-appointed ones. From there Cam is shown down a series of increasingly fancy corridors until he reaches an office that would be, if not at home in a Manhattan skyscraper, at least among equals. Everything is shiny, from the walls (marble) to the furniture (mahogany) to the goblin behind the desk (wearing red silk robes with moving silver embroidery). His escort introduces him to Deputy Ambassador Rangvald and leaves.

"So it seems you can create material that does not disappear or revert," he says without preamble. 

"Yes, like I said."

"What limits does this ability have? Is it learnable by any wizard, or restricted to a subset?"

"I'm not a wizard," Cam says.

"Are you a different variety of human, or a different species? How many of you are there? Is it heritable?"

"I used to be a human but now I'm a different species, billions, no."

"Billions? That seems highly unlikely."

"I mean, they don't live around here," he replies blandly.

"Does anyone other than you currently have the ability to dump gold into the economy of this planet."

"Not yet."

Deputy Ambassador Rangvald is not having the best day. "Would you care to explain."

"Well, I got here, and others could too, and on the whole it might be good if they did since it's easier to end material scarcity that way, but I can tell you about the monetary arrangements that work where this is already common."