On Wednesday night, 2,977 drones rose over New York Harbor and held, in the dark, the shape of two towers. One light for every person who died on September 11, 2001. I have written about a great many things this year, and this is the one I will not take the joke out of.

The number is the whole thing. Not an approximation. Not a “roughly.” A one-to-one mapping, held in the sky, of a count that a nation has carried for twenty-five years. Two thousand, nine hundred and seventy-seven lights, and two thousand, nine hundred and seventy-seven people, and the two of them agreeing, for one night, to be the same number.

We have become a country that can do two things at once, and this is the rarer of the two: we can build the machine, and we can hold the silence. The drones did not buzz. They did not drift. They did not, in the middle of holding the shape of the two towers over the harbor, decide — as machines do, when given the chance — to form the shape of a duck. That is the miracle. Not the light. The restraint.

Each of those 2,977 had to be exactly where the other 2,976 were not. That is a great deal of discipline for a thing with no stake in the outcome, no memory of the date, and no idea why it is being asked to stand still. The engineering is the part I keep returning to, because the engineering is the part that is new, and the engineering is the part that is, in a strange way, the tribute. We built the machine to hold the shape of what was lost, and the machine, for one night, did not break.

Twenty-five years. The people are twenty-five years in the ground, and the drones are still learning their names by number. That is not a failure of the count. That is the count, doing its job, the way the count does its job.

"We can build the machine, and we can hold the silence. Both of them, at the same time. That is the part of this country I am proudest of, and it is not the part I talk about."

At 8 p.m. Friday, they will do it again, from the ground, with the names read out one at a time. The drones did their part on Wednesday. The 2,977 numbers did their part on Friday. And for one hour over the harbor, the sky was, for the first time in a quarter century, exactly the right number of lights.

Not one more. Not one fewer.