Episode 20 - The Electric Age

Tomlin Hawthorne

You walk into a room and flick the light switch. The light comes on at once. No delay you could ever notice.

Tomlin Hawthorne

So here's the question. Inside the copper wire that runs from the switch to the bulb, there are electrons, and when you flick the switch, they start to move. How fast are they going?

Tomlin Hawthorne

The speed of light? A thousand miles an hour? Walking pace?

Tomlin Hawthorne

If you raced one against a snail, the snail would win. Easily. The electrons in the wire drift along at a fraction of a millimetre per second. An electron leaving your switch as you turn on the light would take hours to reach the bulb.

Tomlin Hawthorne

And yet the light comes on instantly. So something else is travelling down that wire, something very fast, and it isn't the electrons. Today we find out what, and how a laboratory curiosity of 1831 turned into the thing that modern life is built on.

Tomlin Hawthorne

Last time, you looked at lamps in the reflection of a CD. If you tried a filament bulb, you saw a smooth rainbow. If you tried a fluorescent tube, you saw separate bands of colour with gaps. Those bands are the barcode of mercury vapour. You did, with a scratched disc, what Kirchhoff and Bunsen did with a cigar box, and what Auguste Comte said nobody would ever do.

Tomlin Hawthorne

This is the last episode of Part Four. For four weeks we've been in the realm of ideas: fields, waves, spectra. Today I want to bring it down to earth, because this is the physics that left the laboratory and rearranged the world. And it did it, as these things do, by way of a commercial brawl.

Tomlin Hawthorne

Edison was already the most famous inventor alive. The phonograph, the practical light bulb. But his real genius, I think, wasn't either of those. It was seeing that a light bulb on its own is worthless. Nobody can use one. To sell bulbs you have to sell the whole thing: the generators, the cables under the street, the fuses, the sockets, the meter on the wall to send the bill. He invented the electricity business.

Tomlin Hawthorne

And he built it on direct current. That's current that flows steadily one way, like water in a pipe. It worked. It was fairly safe. And it had one severe drawback. It couldn't travel. A wire carrying current wastes energy as heat, and at the low pressures Edison used, the losses were so heavy that a power station could only serve customers within about a mile. A city would need one every few blocks.

Tomlin Hawthorne

Now, enter the other two characters.

Tomlin Hawthorne

Nikola Tesla arrived in New York in 1884, a Serbian engineer of twenty-eight, with, he said, four cents in his pocket, a few poems, and a letter of introduction to Edison. He was six foot two, immaculately dressed, spoke eight languages, and had a mind that worked in a way nobody has quite explained. He claimed he could design a machine entirely in his head, run it in his imagination for weeks, and then check it for wear.

Tomlin Hawthorne

He went to work for Edison and lasted about six months. There's a story that Edison promised him fifty thousand dollars for improving the generators, and when Tesla did it and asked for the money, Edison laughed and said he didn't understand American humour. Tesla resigned, and for a while he dug ditches.

Tomlin Hawthorne

What Tesla had in his head was a way to do it differently. Alternating current. Current that doesn't flow steadily, but surges back and forth, reversing direction many times a second.

Tomlin Hawthorne

And the third character is George Westinghouse, a blunt, generous industrialist from Pittsburgh who'd made his fortune from an air brake for trains. He bought Tesla's patents, and bet the company on them.

Tomlin Hawthorne

Why does it matter which way the current goes? This is the physics, and it's Faraday.

Tomlin Hawthorne

Here's the problem again. Wires waste energy as heat. The waste depends on how much current is flowing. But the power you deliver depends on two things multiplied together: the current, and the electrical pressure pushing it, which is called voltage. So you can deliver the same power with a big current at low voltage, or a small current at high voltage. And the second way wastes far less. If you raise the voltage a hundred times, you cut the losses by a factor of ten thousand.

Tomlin Hawthorne

So you'd like to send electricity across country at an enormous voltage. Hundreds of thousands of volts. But you can't have that coming out of a socket in somebody's kitchen. It would kill them. You need to step it up for the journey and step it down at the other end.

Tomlin Hawthorne

And there's a device that does exactly that. It's called a transformer, and it's nothing but Faraday's iron ring from 1831. Two coils of wire wound on one piece of iron. Current in the first coil makes a magnetic field. The field passes through the second coil and makes a current there. And by choosing how many turns of wire are in each coil, you can trade voltage for current in any ratio you like.

Tomlin Hawthorne

But remember the catch. Remember what Faraday found, the thing everyone had missed for ten years. A steady magnet does nothing. It has to be changing.

Tomlin Hawthorne

So a transformer does nothing at all with steady, direct current. The needle twitches once when you switch on, and that's it. It only works if the current keeps changing. Which is to say, if it alternates.

Tomlin Hawthorne

That's the whole war, in one sentence. Alternating current can be transformed, so it can be sent hundreds of miles. Direct current, with the technology of the day, couldn't.

Tomlin Hawthorne

Edison knew he was on the wrong side of the physics. And he fought dirty. His line was that alternating current, at those high voltages, was a killer. He was right that it was dangerous. His people staged public demonstrations in which stray dogs, and calves, and a horse were electrocuted with Westinghouse's current, in front of reporters. An associate of his lobbied New York State to adopt, for its new and supposedly humane method of execution, an electric chair, and made sure it ran on a Westinghouse generator. The first execution, in 1890, was a horror. It took two attempts. Edison's camp tried to get the public to call the process being westinghoused.

Tomlin Hawthorne

It didn't work. In 1893 Westinghouse won the contract to light the great World's Fair in Chicago, underbidding Edison's company by half. On the opening night, the President pressed a key, and a hundred thousand lamps came on at once, across a whole artificial city. Twenty-seven million people came to see it that summer. Most had never seen an electric light.

Tomlin Hawthorne

Three years later, Westinghouse and Tesla had harnessed Niagara Falls, and sent its power twenty-six miles to the city of Buffalo. That was the end of the argument.

Tomlin Hawthorne

As for Edison: his own financiers had by then merged his company with a rival and removed his name from it. It became General Electric. He'd invented the industry and been eased out of it.

Tomlin Hawthorne

You'll recognise the shape. A standards war. The first mover with the weaker technology and the stronger brand. Fear as a marketing tool. A showpiece contract that tips the market. It's been replayed many times since, with videotape and with operating systems. The historian Thomas Hughes wrote the classic study, and his conclusion was that the winners weren't the people with the best invention. They were the people who built the best system.

Tomlin Hawthorne

So here's what's behind your wall socket.

Tomlin Hawthorne

Somewhere, something is turning. A turbine, spun by steam from burning gas or splitting atoms, or by falling water, or by wind. On its shaft are magnets, spinning inside coils of wire. That's Faraday's 1831 experiment, scaled up until the rotor weighs as much as a house. Nearly all the electricity in the world is made that way. Solar panels are the one real exception.

Tomlin Hawthorne

The voltage is stepped up to hundreds of thousands of volts and sent out over the pylons. Near your town it's stepped down. In your street, down again.

Tomlin Hawthorne

And all of this, every generator in a whole country, is spinning in step. In Europe, fifty turns a second. In North America, sixty. Every one of them locked together like dancers. An electricity grid is a single machine, the largest humans have ever built.

Tomlin Hawthorne

And it has a remarkable property. It stores almost nothing. The electricity you're using this second was generated this second. Supply has to match demand, instant by instant, all day, every day. There are people in control rooms whose job is to watch the nation's kettles.

Tomlin Hawthorne

I mean that literally. In Britain, the engineers used to study the television schedule. When a hugely popular programme ended, millions of people would get up at the same moment and put the kettle on, and demand would leap by the output of a couple of large power stations in the space of a minute or two. They'd have a reservoir in Wales standing by, ready to open the gates.

Tomlin Hawthorne

Now, the snail.

Tomlin Hawthorne

Picture a long pipe, already completely full of marbles, end to end. Push one more marble in at this end. A marble pops out at the far end. At once. But no marble has travelled the length of the pipe. Each one just nudged its neighbour.

Tomlin Hawthorne

A wire is like that. It's already full of electrons. When you close the switch, the electrons near the switch don't have to get to the bulb. They shove their neighbours, who shove theirs. And that shove travels down the wire at close to the speed of light, while the electrons themselves barely stir.

Tomlin Hawthorne

And in the wire in your house, with alternating current, they don't even go anywhere. They shuffle a tiny distance one way and a tiny distance back, fifty or sixty times a second. The electrons in your reading lamp have probably been in that lamp since you bought it.

Tomlin Hawthorne

So what is it that travels? What carries the energy from the power station to your kettle?

Tomlin Hawthorne

The field. It's Faraday and Maxwell again. The energy isn't carried inside the wire by the electrons. It's carried by the electric and magnetic fields in the space around the wire. The wire is more like a guide rail. I find that hard to believe every time I look at a pylon, and it's true.

Tomlin Hawthorne

And that's also all that communication is. A radio transmitter shakes electrons up and down a metal mast. That shakes the field. The disturbance spreads out at the speed of light, Maxwell's wave. Miles away, it passes over your aerial, and shakes the electrons in that, very faintly, in the same rhythm. Your voice on a mobile phone is turned into a pattern, stamped on to such a wave, caught by a mast, turned into pulses of light in a glass fibre, flashed across the country or under an ocean, and turned back. Every step of that is in Maxwell's four equations of 1865. He was describing the internet.

Tomlin Hawthorne

I want to end Part Four with a puzzle. It looks small. It isn't.

Tomlin Hawthorne

Your Wi-Fi router and your microwave oven use almost exactly the same kind of electromagnetic wave. Nearly the same wavelength, about twelve centimetres. You measured it, with the chocolate. The difference is power. The router puts out a tenth of a watt or so. The oven, about a thousand.

Tomlin Hawthorne

Now, people worry about whether such waves are harmful. So here's what's known. That kind of wave can warm you up, if there's enough of it. That's how the oven cooks. But it can't damage the molecules of your body directly. It can't break a strand of DNA. And here's the thing: that's true however intense you make it. Turn the power up and you get more heating. You never get a different kind of damage.

Tomlin Hawthorne

Ultraviolet light is the other way round. Even faint ultraviolet, on a cloudy day, can damage DNA and, over the years, cause skin cancer. A tiny dose of X-rays can do it.

Tomlin Hawthorne

Now think about that as a physicist of 1890 would. Light is a wave. The energy in a wave is in how big it is, its amplitude. A powerful wave ought to be able to do anything a feeble one can do, and more. A big ocean wave can do everything a ripple can.

Tomlin Hawthorne

So why can a weak ultraviolet wave break a molecule, when a thousand watts of microwaves can't? Why should the kind of light matter more than the amount?

Tomlin Hawthorne

There's no answer to that in Maxwell. None. The wave theory of light, which we've just spent five episodes establishing, cannot explain it.

Tomlin Hawthorne

Hold that puzzle. In episode twenty-seven it's going to crack classical physics open.

Tomlin Hawthorne

The myth of the week is contained in a single word: radiation. We use it for the signal from a phone mast, the warmth from a radiator, the light from a lamp, X-rays, and the fallout from a nuclear accident. As if they were all one thing, in different strengths.

Tomlin Hawthorne

They aren't. The first four are all light, and they differ enormously in what they can do, as I've just said. The last is mostly something else altogether: fast-moving particles of matter, which we'll meet in episode thirty-five. A word that covers both a candle and Chernobyl isn't helping anybody think.

Tomlin Hawthorne

And the question to take away.

Tomlin Hawthorne

Faraday moved his magnet in 1831. The first power station opened in 1882. Fifty-one years. When Hertz made the first radio waves, he was asked what use they were and he said: none.

Tomlin Hawthorne

In 1939 an American educator, Abraham Flexner, wrote an essay with a title I love: The Usefulness of Useless Knowledge. His argument is that almost everything useful has come, in the end, from people who weren't trying to be useful. Who were just curious. That Marconi was inevitable once Maxwell and Hertz had done their work, and that Maxwell and Hertz had no interest in telegraphs at all.

Tomlin Hawthorne

If that's right, it's awkward. Because a government, or a company, or a foundation, has to decide what to pay for. And "fund things with no foreseeable use, and wait fifty years" is a hard line to put in a budget. How would you decide? Is there any way to tell useful useless knowledge from the plain useless kind in advance?

Tomlin Hawthorne

Your challenge. Two things.

Tomlin Hawthorne

One. Take a sheet of kitchen foil and wrap your phone in it, completely, no gaps. Then ring it from another phone. It won't ring. The waves can't get through a closed metal skin; the electrons in the foil move to cancel the field inside. That's called a Faraday cage, after you know who. Unwrap it and it'll catch up.

Tomlin Hawthorne

Two. With a pencil and paper, trace a voice message from your phone to a friend's. Every stage you can think of. Microphone, chip, radio wave, mast, cable, and so on. At each step, write down which piece of physics from the last five episodes is doing the work. I think you'll find you can name nearly all of it. A month ago you couldn't have.

Tomlin Hawthorne

That's Part Four. We've found that space is full of fields, that light is a ripple in them, and that this one idea runs the world. Next time we begin Part Five, and the comfortable picture breaks. A twenty-six-year-old clerk in the Swiss patent office asks a simple question about Maxwell's speed of light. Relative to what? And by the time he's finished answering it, there's nothing left of space and time as you know them.