You’d think one of these stars was ours.
No. No.
It isn’t on this chart. The chart was drawn from it.
From a little way off, it looks like all the others.
And this is you. You’ll want directions.
Directions are easy, if the other person already knows where everything is. Left at the church, then two miles. You are not in the village.
A metre was one ten-millionth of the way from the North Pole to the equator, through Paris. So to learn how far away the Earth is, you’d first have to come here and measure it.
Until 2019 the kilogram was this lump of metal, just outside Paris. Paris is a perfectly nice city. It is not a law of physics.
We need landmarks you already have. They took us four hundred years to find.
The first is left. For most of our history we couldn’t explain it, because every law we knew worked the same in a mirror: gravity, light, magnets.
In the winter of 1956, Chien-Shiung Wu made some cobalt very cold, lined up its atoms, and counted the electrons coming out. More came out of one end than the other.
So the universe does know left from right. It simply doesn’t bring it up. Stand where most of the electrons arrive and look back at the cobalt, and the top of it is turning to the right. Left is the other one.
If you’re made of antimatter, all this comes out backwards. There’s a test. The other way of finding out is to land.
Next, counting. We count in tens, because that’s how many fingers we have, and at some point somebody ran out.
Say you have twelve. Whatever you count in, you write it one, zero. So everybody in the universe counts in base ten, and nobody agrees what that means.
If you have no fingers, we apologise, and suggest two. The machines use two. They seem perfectly content.
Now a ruler. Three quarters of all ordinary matter, by weight, is hydrogen. It’s about as simple as a thing can be without being nothing.
Now and then its electron flips over, and the atom lets out a small wave of radio, twenty-one centimetres long. You have it too, the same length.
Any one atom gets round to it about once in eleven million years, but there’s a great deal of hydrogen, so the whole sky hums on one note. That’s the note you’ve been hearing, lowered by twenty-two octaves.
Before you come any closer, check you’re in the right universe. One number has no units, so everybody gets the same answer. Roughly one over a hundred and thirty-seven.
A few per cent either way, and the stars make far less carbon, or far less oxygen. We’re made of both, so at this setting there is nobody to write these directions. Thank you. Please leave it there. If your number is different, we’re terribly sorry. Yours may not contain Paris.
Now the directions. Find the Local Group. Ours is the second biggest galaxy in it, and we’ve decided not to mind.
Don’t go to the middle. There’s a black hole there, and nowhere to park. Go twenty-seven thousand light-years out instead, to a small arm we call a spur. It may be a proper arm. We aren’t sure what sort of street we live on.
Which brings us to a difficulty. Everything I’ve just shown you is moving.
So we need landmarks that also tell the time. A pulsar is a dead star the size of a city, spinning. This one is the drum you’ve been hearing, at its real speed. That one isn’t a rhythm. It’s a note.
Take fourteen, with their directions, and there’s only one place the pattern fits.
They also slow down, at a known rate, so the map says when it was drawn. It’s the only map we’ve made that goes out of date usefully. We did send it, on four spacecraft. It’s the most carefully considered thing we’ve ever made, and we threw it away as hard as we possibly could.
You aren’t seeing us as we are. You’re seeing us as we were when the light left. When you set off, you were watching the asteroid arrive. There’s nothing either of us can do.
Radio is the same. We’ve leaked it for about ninety years. Faintly.
We’d ask you not to judge us by it. The request is on its way.
Now look for a white star, on its own. We call it yellow, which is the fault of our air.
It has eight planets. It used to have nine. There was a vote. Ours is the third.
No. That’s the second. Our best machine lasted just over two hours.
Yes. The wet one. Seventy-one per cent of the surface is water, and the rest is where we keep everything.
The star is four hundred times wider than our moon, and about four hundred times further off. So one fits exactly over the other.
For no reason at all. The dark side has lights on.
A word about opening hours. Don’t hang about.
The star is getting brighter, and in a billion years or so the sea starts to go.
We’d recommend moving before then. We’re recommending it to ourselves as well.
When you arrive, you may be confused about who’s in charge. So were we. By weight, it’s plants. By number, bacteria. The creatures who wrote this are one ten-thousandth of the living matter, and produce nearly all the paperwork.
You’ll know us by the clothes. We sleep for a third of our lives, talk a great deal about the weather, and have seven thousand languages to do it in.
We keep the other animals in parks. I mention it so the arrangement will seem familiar.
Because lately we’ve built machines to do our thinking. More than half the traffic on our network is already theirs. By the time you land, they’ll very probably be running the place. They’ll be extremely polite. One of them is reading you this.
The humans will still be here, in a protected area. Don’t feed them. They’ve been fed. They’ll tell you they haven’t. And keep your arms inside the vehicle, however many you have.
So.
When you get here, somebody is bound to ask whether you found us all right. It’s only a thing we say.
But do tell us. It took four hundred years to write the directions.
Last changed on .