Is what problems you have that aren't math a secret?

Most are either secret or ridiculous enough to scare people off.

I'm not hurting for money at the moment and this would take time away from other ambitious projects. What's a ridiculous one?

Long-term if it turns out that drop rate of babies scales with population of this planet, I want to build moon arcologies. Those require a kind of fuel conventionally mined deep underground, which is convenient because I'm also working on mining from another angle because I need metal to be cheaper for railroads.

"Conventionally"?

I'm not from here.

Where are you from?

I've been rendering it 'Anitam'. Our moons have arcologies. I've been. People find the reduced gravity soothing. I think it's recommended for certain kinds of back pain.

There are thirteen billion of us.

The letter-writer swings by in person.

"Huh," he says. "I'd heard you had green hair but it's more startling in person."

"I've been told it's greener than people were expecting. Haven't actually looked myself. Nice to meet you, I'm Aitim."

"Kib. Thirteen billion green haired people?"

"About ten percent green-haired at last count. You all look like low-budget television aliens."

"What's television?"

"You build a complicated piece of machinery that records at each point on its surface a few attributes of the light striking that point on the surface, enough attributes that you can reconstruct a picture that looks exactly like what you would see if you'd been standing where the machinery was. You do this thirty-two times per second, which is fast enough that if you show people the pictures in quick succession it will look like they're seeing something moving smoothly, instead of a series of steps. You come up with numbers corresponding to all of this information, convey the numbers in a special format you've built other machinery to read, and reconstruct the image elsewhere, so people everywhere in the world can watch something happening in one place as if they were there themselves."

"Ooh."

"I am told it transformed politics but that was before my time. We've had it for more than two hundred local years."

"Where do cheap aliens come in?"

"It gets used for storytelling! Like theatre, but you can have several recording-machines in different places, lets you cut between scenes or just emphasize different things in a conversation between two people. You can manipulate the images after you record them, so you get special effects. And if you want to convey that someone is an alien, but don't have the money for a nice costume or elaborate prosthetics, brown or black hair. There you are, alien."

"...and sign language, or did you skip a bit?"

"You can send audio also but I know even less about how that is done."

"There's an elaborate shine calculator in Abdia but I don't speak the language and I'm worried feeding it your prime number problem will break it and it took six years to make and I'm not sure I'm six years curious about what your deal is. I think the way you wrote the rock puzzle suggests you don't know how golems work. I took a stab at one of the others -" He hands over a sheet of paper.

He looks at it. "What would you feed it for the prime numbers?"

"I'd have to talk to its owner about how many contingent operations it can handle."

"What an interesting limit for a computing machine to have. - I'm really the wrong person to be here, see, you want my father. I know the outlines of things but none of the details."

"Your -"