The Set Price

Every old star that flashes helium flashes at exactly the same brightness, in every galaxy, down to the last decimal. That’s the standard candle, the tape measure we use on the universe, and it never wiggles, not once in a hundred years of data from every observatory. A real constant wiggles. A dial doesn’t.

Stars die at a set price.

The price is 2.44, distance-corrected, in the units we use. An old star swells up, burns helium in its core, and at one exact brightness it flashes and stops being a red giant. Brighter than that, none anywhere. Fainter than that, none anywhere. Same in Andromeda. Same in galaxies that don’t have names yet. Same in every galaxy, down to the last decimal.

We call it a standard candle. We measure the universe with it, the way a carpenter measures a room with a tape. Our best candle. Our favorite candle.

It works. That’s the trouble. It works too well.

I’m the night man at the big glass on the dry mountain. Six years now. Same canned spaghetti. Warm room. The mirror, the sky, and the number never moving. The number sits there like a parked car.

A natural constant has scatter. Gravity has scatter. The speed of light has scatter, if you measure it hard enough. The tip of the flash has no scatter. Not within our noise. Last spring I re-reduced the same field a hundred ways, with a hundred zero-points. The answer changed less than a bad penny. I stayed up the whole night and did it again, with a different field, a different reduction, a different everything. Same penny.

Keefer found me at sunrise, still at the terminal. “You look like your grandmother died,” he said.

“Somebody’s grandmother did,” I told him. “Everywhere. At the same time.”

“More data,” he said, which is what Keefer says to everything, including his wife.

I didn’t need more data. I had a hundred years of data. Every observatory on Earth had been pointing at the same number since before the war, and the number had never once wiggled. That’s not a constant. Constants wiggle. A dial doesn’t wiggle. A dial is set.

I started talking to the catalog. That’s what night men do. “All right,” I told it, “what are you?”

A standard candle, it said.

Candles are made, I told it.

That was the idea. It got me, and neither of us has let go since. Standard. Like a screw with four turns on it.

I took the idea down the mountain to a bar, with beer and talk. There was a plumber there, telling a table about a furnace that wouldn’t stay lit. He’d cleaned the jets, replaced the thermocouple. Then he found it. The pilot was set wrong. Four turns on a screw, and it burned like a match.

“If you wanted to do the same thing every time,” he said, “you don’t trust nature. You set it.”

The universe is a factory, and the factory makes the same flame every time. Factories make things. So the question is: what does a factory do with one flame, made over and over, fourteen billion years running?

Not light. Not heat. That leaves fire. A flame set to one spec is not a lamp. A flame set to one spec forever is a pilot.

A pilot light has one job. It lights the gas.