The original note, as written at the time
A fantasy universe where several habitable worlds, more than the number of people alive, exist and are connected by ancient gateways. Physically these worlds are millions of light years apart. However, these gateways cannot let any matter or energy through save for only the human body. They are only permeable to the genetic signature and soul of a person. When a person goes through, anything that isn’t connected to him does not follow.
Ongoing development
There are more worlds than people and the maths of that is not a comfort.
Stand at a gateway and you can name eleven destinations by the colour of their air. Every one is habitable, every one is empty of us, and every one is millions of light years from the next, which does not matter, because the gateways do not carry distance. They carry a person.
That is the whole of it. Nothing goes through but a body. Not cloth, not tool, not a cup of water. Not energy — a torch will not light on the far side, and the men who tried to carry fire through came back with nothing at all, and some of them came back with no hands.
So a settlement is not a settlement. Everything a man will ever own on the far side must be grown or made from what is already there, by a person who arrived with nothing but their own skin. The first year of every new world is a naked year, and the histories of the colonisation are mostly the histories of what people did in that first year, which is not something we discuss in front of children.
The gateways can tell a person from a thing. They read the signature and they read the soul, and there are people who cannot pass — men who have been in the wars, mostly, and the scholars argue about whether the soul is damaged or merely changed. My aunt cannot pass. She has not said why. She sat by the gate for a week when the family went, and then walked home.
And there is one more thing, which the guilds keep quiet and the priests do not. Every world is empty of us, but they are not all empty. Three of the eleven have marks — cut stone, a pattern in the ground, something that was built. Nothing living. No bones. Just the marks, in a place no one of us could have carried a tool to.
We are not the first to use the gateways. We are the first who cannot carry anything through with us, and it has not yet occurred to anybody that this may be exactly why we are allowed to use them.