In Step

How a continent became one machine, and what holds it together. The narrator is Lily; my cloned voice comes in for a minute after the cold open, with the one corner of this machine I know with my hands. You will hear a sound in the opening that beats once every five seconds. That is the real rhythm of what happened.

At three minutes past noon on the twenty-eighth of April last year, half an hour before Spain and Portugal lost their power, the people who watch the Spanish grid saw a rocking on their instruments: one end of the country against the other. They calmed it. A quarter of an hour later a second one began, slower and far wider. Every spinning machine in Spain and Portugal was leaning one way, all together, and the rest of the continent was leaning the other. One beat every five seconds.

The engineers have a name for that movement. It is a property of the thing they look after, the way a long bridge has a rhythm it likes to swing at. But a bridge sways because it is one object. For Spain to sway against a country a thousand miles away, the two would have to be one object too. They are. Nearly every power station on the Continent, from Lisbon to Istanbul, is part of one machine, and every spinning generator in it turns in step with every other, to a beat of fifty a second.

As a young engineer officer on a Swedish missile boat I used to put a second generator on line by hand. You match the voltage. You match the speed. You watch a needle swing round a dial called a synchroscope, and at the one moment when the two machines are in step you close the breaker. Get it wrong and you put the ship in the dark. This episode is about how that small ritual came to be performed by a continent.

Only change gives current

It begins with a bookbinder. Michael Faraday, a blacksmith’s son, educated himself by reading the books he bound. In a basement in London he wound two coils of wire on an iron ring the size of a saucer, with wire sold for stiffening ladies’ bonnets, and connected one coil to a battery. His notebook: “Immediately a sensible effect on needle. It oscillated and settled at last in original position.” The needle jumped, and then, with the current still flowing, went back to rest. A steady current in one coil does nothing to the other. Only a change does. Some weeks later he wrote to a friend that it might be “a weed instead of a fish”. It was a fish. That autumn he spun a copper disc between the poles of a magnet and got a steady current for as long as he turned the handle. A magnet sitting still beside a wire gives you nothing. You have to keep something moving. Until a few years ago, everything that fed the grid was something that turned.

The circus

Half a century later Thomas Edison lit a few hundred lamps in lower Manhattan from a building on Pearl Street. The whole of part one is inside that building: coal burns under boilers, steam drives engines that live on the fall of heat, and each engine turns a dynamo, Faraday’s disc grown up. What came out was new in the world: work sent away from the fire that made it, along a wire, with nothing carried and nothing piped.

Not far, though. Turn your kettle over: it says something like 230 volts and 10 amps. Voltage is the height of the fall. The amps are the current, how much comes down each second. Multiply them and you have the power. Edison chose a low height because it was safe in a house, so he needed a large current, and a large current warms the wire and wastes the power. A city lit his way needed a coal-burning power station every mile or so. He had no way to raise the height for the journey and lower it at the door.

Pearl Street had a second problem. The first time they ran two of the great dynamos on the same wires, Edison said: “Of all the circuses since Adam was born, we had the worst then! One engine would stop, and the other would run up to about a thousand revolutions, and then they would see-saw.” Men ran into the street. The trouble was the governors, the devices that hold an engine to a steady speed, as cruise control holds a car. Each engine had one, each minded its own speed, and on a shared wire the two fought. So at the birth of the power station two questions were open. How do you change the height of the fall? And how do machines that share a wire agree?

Falling water

The answer to the first had been in Faraday’s basement all along. Two coils on one loop of iron: give the second coil ten times the turns and you get ten times the height and a tenth of the current. A tenth of the current warms the wire a hundred times less. It needs a current that never stops changing, alternating current, which is what comes out of every socket in your house. Three Hungarian engineers made the device a product and named it: the transformer.

The proof came one summer at an exhibition in Frankfurt. A hundred and seventy-five kilometres to the south, at Lauffen on the Neckar, a town named for its rapids, a cement works had a water turbine in the river. They put a generator on it, raised the height to about fifteen thousand volts, and ran three thin copper wires to Frankfurt on thousands of wooden poles. On an August evening the current arrived. By the next day it lit a thousand lamps and drove a pump that fed an artificial waterfall. Falling water on the Neckar made a waterfall in Frankfurt, and three quarters of the power had arrived. In part one we said that we put steps in the fall of energy and live on them, and that electricity is the top step. That summer somebody picked up the top step and carried it across a country.

There is a Swedish end to it. Jonas Wenström, disabled for life by a childhood illness, patented a complete three-wire system of his own; the company built on his inventions is known today as ABB. One December it went to work: water from a forest lake at Hellsjön led down a drop of forty-four metres to the turbines, and wires running up to fourteen kilometres through the forest to the iron mines at Grängesberg. A machinist remembered that at the trial run Wenström’s colleague was “eld och lågor”. Wenström was not there. He had caught a cold that went to his lungs, and within days of the current reaching the mine he died, at thirty-eight.

The black hand and the gold hand

Now machines a long way apart shared their wires, which brings back the circus. What keeps them together?

Henry Warren, an engineer near Boston, built an electric clock around a small motor that turns in exact step with the current that feeds it. He plugged it in. “As a time-keeper the device was a failure. It was off as much as 10 or 15 minutes a day.” The motor was perfect. It was counting every swing of the current. His clock was right, and the power company was wrong.

Alternating current swings a fixed number of times a second: fifty in Europe. That number, the frequency, is not set by a dial. It is the generators turning, the turns and the swings locked together like the teeth of two gears. Warren’s clock was a counter of the turns of the generators of Boston. In October 1916 he installed a master clock at a Boston power station: a black hand driven by a pendulum clock, a gold hand driven by the station’s own current. If the gold hand dropped behind, the operator opened the steam until it caught up. A historian has argued that this was one of the things that made it practical to join power systems, because two stations can share their wires only if they keep the same beat, and for the first time there was a way to see it.

Europe still keeps that clock. A few winters ago two countries in the Balkans were in dispute over a small shortfall of power, and for seven weeks neither made it up. Every clock on the Continent that counts the mains, from Spain to Turkey, lost close to six minutes.

Jumping onto a moving train

The test Ukraine had planned was to cut every line to Russia and run alone for three days. It began in the early hours of the twenty-fourth of February 2022. About four hours later, Russia invaded. They never reconnected. Three days became three weeks, in wartime, holding their own beat. On the fourth day of the war Ukraine and Moldova asked Europe to take them in early. Bring two systems to the same height and the same beat, wait for the swings to line up, close the switch: from that instant every generator in Ukraine turns in step with every generator in Portugal, and a power station knocked out in Ukraine is a jolt on every shaft on the Continent. It had been planned to take another year. It was done in the middle of March.

Four seconds

When you switch on your kettle, where does the power come from in that first instant? No power station has been told. It comes out of the spin. Every big generator has a rotor weighing many tonnes, all locked to the same beat, and your kettle reaches all of them at once as a slight extra drag. If nobody pushes harder they all slow together. That is what Warren’s clock read and what the ovens of Europe recorded. The frequency is the speed of one machine. It falls when the continent uses more than it makes. At a dam in the north a governor feels its turbine slow and opens the gates. Nobody rang the dam. The anthropologist Gregory Bateson once defined information as “a difference which makes a difference”. He was talking about minds, not megawatts, and the borrowing is mine. But it fits.

How much is in the spin? The Nordic countries are a machine of their own, joined to the Continent only by direct-current cables, which pass power and do not pass the beat, and their operators publish the figure. All the energy of motion in every turbine and generator comes, on an average day, to about what is stored in eight hundred electric cars. It would run those countries for about four seconds. There is no tank of electricity anywhere. A wire is a link, not a tank. The top step is about four seconds wide, and nothing stands behind it.

And now the sway has an explanation. Machines joined by wires are held the way two weights are held by a spring, firmly, with some give, and anything heavy on a spring has a rhythm of its own. Spain and Portugal hang at the far end of the machine on a few lines across the Pyrenees. Give that end a push and it rocks, a beat every five seconds.

At 12:33 that Monday the power stations of Spain began dropping off faster than anything could replace them, and the peninsula turned slower than the continent it was joined to. For two seconds the rest of Europe tried to hold it up. A spring can pull only so hard. To save France, the lines opened. It had happened before, four summers earlier, when a forest fire cut the peninsula loose; that time Spain and Portugal kept a beat of their own and were back within the hour. This time they were dark in seconds, and not because any machine had been destroyed: nothing was broken.

But falling out of step was how it ended, not how it began. The number you have just spent an episode learning is not the one that brought Spain down. What did is part three.

Sources, for readers who want the originals: Bence Jones, The Life and Letters of Faraday (1870), and Faraday’s letter to Richard Phillips of 23 September 1831; Dyer and Martin, Edison: His Life and Inventions (1910), for Pearl Street and the circus; the New York Times of 5 September 1882; the IEEE Milestone for Lauffen to Frankfurt, 1891, and the VDE’s account; Tekniska museet on Jonas Wenström, and the ASEA brochure of 1894 reprinted in Daedalus (1940); Allison Marsh, “This Clock Made Power Grids Possible” (IEEE Spectrum, February 2024), and the Ashland Historical Society on Henry Warren; ENTSO-E’s press release of 6 March 2018 on the frequency deviation, its releases of 16 March 2022 on Ukraine and Moldova and of 9 February 2025 on the Baltic states, its report on the inter-area oscillations of 1 December 2016, and its final report on the separation of the Iberian Peninsula on 24 July 2021; the Nordic operators’ “Requirements for minimum inertia in the Nordic power system” (August 2025); Red Eléctrica’s incident report of 18 June 2025; Gregory Bateson, “Form, Substance and Difference” (1970).

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