The moon is hollow, and the city is on the inside of it, and the only thing that keeps us on the floor is that everyone walks.
I came in on a supply hauler with three crates of membranes and a headache. My contract called me a balance engineer. That is a job that does not exist anywhere else. I would find out why.
The first thing you notice is the sound. A low grinding, everywhere, under the floors and in the walls and in your teeth. The second thing is that everyone is moving the same direction. Old men, kids, nurses, everyone, drifting along the curved streets with their faces set the same way, like commuters, except there are no destinations and no one is going anywhere. They just walk.
I asked the dock clerk what the sound was.
"The rail," she said. "Keep your feet on the gold line when you're on the main streets. You'll pick it up."
The gold line ran through every street like a vein. Walking shoes clicked into it. When you stepped on the line facing the right way, the city pulled you gently forward, one long polite tug, and walking became the easiest thing your body had ever done. Step off the line and you weighed a little more, and the day felt longer.
That's the whole trick. The moon spins. The spin makes the weight. The spin is always slowing. So the city built a ring of gears under the gold line, and when enough people walk the same direction on the line at the same time, they push the gears, and the gears push the moon, and the moon keeps turning. Everyone walks so that down stays down.
I did the math the first night, because that's what I was hired for. I sat in my room with the grinder in my teeth and a pad of real paper and worked it out.
Here's the part they leave out of the contract. A person walking cannot push a moon. A person walking can push a gear, and the gear can push a bigger gear, and on and on, but every gear takes its tax, and the whole system throws away almost everything you feed it. The Walk, all of it, every citizen on the gold line every day of their lives, buys the moon maybe a few extra decades. And only if the flywheel it all feeds into still turns. And the flywheel, I could hear it through the floor my first night, turned the way a tired heart turns. With effort. With a catch.
I went to the Hall and asked to see the records for the ring.
The keeper was an old woman named Nadi. She had worked the ring forty years and had the hands for it, knuckles gone to knobs, nails worn flat. She didn't argue with me. That was the first wrong thing. I had come ready to be told I didn't understand. Instead she unlocked a cabinet and gave me the whole ledger and stood there while I read, and the grinder kept grinding under our feet.
The numbers were worse than mine. The flywheel had a flaw in its casting, from the founding, that no one knew about until it was already sealed under a hundred meters of city. Every year for a century the elders had cut the projected remaining life of the ring roughly in half. The last entry was five years old. It said, in a young person's handwriting, that the ring would seize within sixty years and probably within thirty. That entry was followed by one line, in different ink, in Nadi's hand:
Continue the Walk.
"Why?" I said.
Nadi looked at me the way you look at a child who has asked why the sun comes up. "Because if they stop, they don't fall," she said. "Not for a long time. There is plenty of spin left for them to grow old inside. Nothing about the Walk saves anyone. It never did. But a person who is walking is a person who has a direction. A person who is walking believes tomorrow is a place you can get to. You give three thousand people thirty years of down and no reason to walk, and you find out very fast what people do when they understand they are only waiting."
"So it's a lie."
"It's a liturgy," she said. "There is a difference, and the difference is not small, and I will not have you flatten it."
I wanted to argue. I had the math. But you don't win an argument with someone who already agrees with your numbers and has gone on walking anyway.
The second wrong thing was the children.
I took a shift on the line, because everyone does, and I ended up beside a girl of maybe nine, matching my step to hers, because that's what happens on the line, you fall in with whoever is next to you. She asked if I was the new engineer. I said yes. She asked if I was going to fix the turning.
"Maybe," I said.
"Good," she said. "Because my dad says it's slowing down. He says you can feel it in your knees."
I looked down the street, the long curve of it, a thousand backs all leaning the same way, and I thought: every one of them knows. Not the number, not the flaw in the casting, but the thing under the number. They all feel it in their knees. They walk anyway. The Walk is not a lie the elders tell the people. It is a lie the people agree to tell each other, every morning, by walking, so that nobody has to say it out loud alone.
Nadi was still wrong, and I was still right, and both of those things were true at once, and neither one helped.
Here is what I did, and I am not going to make it clean.
I spent a month on the ring. I found what I already knew I would find. There is no fix. Any honest report I could write said the same as the five-year-old entry: thirty years, then a long fall, and the gold line going dark.
So I wrote a different report. I wrote that the ring was holding, that adjusted shift rotations could buy more time, that the Walk should continue. Every word of it was a lie. All of it was also, in the only way that mattered to three thousand people already living inside the truth, a kind of maintenance.
I gave the report to Nadi. She read it. She didn't thank me. She filed it, and went back out to the line, and took her shift, and I took mine beside her, and we walked.
The moon turns because we walk. That is not true. The moon turns because it was spinning a very long time ago, and it is slowing, and one day it will stop, and so will we. But that is not a thing you can say to a person while they are walking, because they will stop to hear it, and then where will any of us be.
Some mornings I still think about standing on the line and turning the other way. Just to see. Just to feel my own weight change, and the city hesitate, and every face on the street come up at once.
I haven't. Not yet. That's the closest I can get to the truth: not yet.