This is the great connection, and it represents the moment the penny dropped for the physicists of the late 1800s. If you want to control electricity, you need magnets. If you want to control magnets, you need electricity. Electricity and magnetism are part of the same phenomenon. Both an electric field and a magnetic field can push on a moving electron. But the result of the push is different. An electric field will push an electron in the direction of the field. A magnetic field will push a moving electron sideways.
Creating a beam of electrons is all well and good, but the real cleverness of these old television sets was to control what that beam was pointed at. And the deep connection between electricity and magnetism is at the heart of it. As an electron zooms through a magnetic field, it gets pushed to one side. The stronger the magnetic field, the more it gets pushed. So by changing the magnetic fields inside an old TV, the electron beam could be pushed and pulled to a point wherever it was needed. The large, permanent magnet that my aunt showed me was used very close to the electron gun, to do the basic focusing. But the steering electromagnets positioned a bit closer to the screen were being controlled directly by the signal from the aerial. They pushed the electron beam so that it scanned horizontally across the screen, one line at a time. The beam itself was being switched on and off during each line, and where it hit the screen, a bright spot was created. The “line output transformer” that Nana mentioned was the bit of kit that controlled the scanning. To make a smooth picture, 405 lines were scanned, 50 times each second, with the electron beam flicking on and off at exactly the right time for each pixel.
This is an incredibly intricate electronic dance. To see any picture at all as a result of it requires a lot of fiddly components all doing the right thing at the right time. So early televisions had lots of knobs and dials to make adjustments, and it sounds as though the temptation to mess with them was too much for many TV owners. Jack had the knack of knowing how to readjust them. It must have seemed like magic at the time. For centuries, craftsmen had been respected for what they could produce, and everyone could appreciate what they’d done even if they couldn’t do it for themselves. Now the world had changed. Electronics engineers could make a device function, but it was impossible to see what exactly they’d done or why it had worked.
It’s odd that silent, invisible electrons locked away in a vacuum were the key to the huge richness of visual broadcasting with all its sound and spectacle. And for fifty years televisions were based on the same simple principle. Put an electron in an electric field, and you’ll speed it up or slow it down. Put that moving electron in a magnetic field, and its path will curve. Leave it there long enough, and it will go around in circles.
The massive physics experiment at CERN in Geneva, famous for the discovery of the Higgs boson in 2012,?? works on exactly the same principles as a cathode ray tube, although the particles it can shift around aren’t just electrons. Any charged particle can be accelerated by an electric field and have its path curved by a magnetic field. The Large Hadron Collider, the experiment that finally confirmed the existence of the Higgs boson, had protons zooming around in its guts. In this case, the speeds reached were incredibly close to the speed of light, so fast that even with extremely powerful magnets to steer the zooming particles, the circle had to be 17 miles in circumference.
So the basic setup used both to discover the electron itself and to run the Large Hadron Collider at CERN, a controlled stream of charged particles in a vacuum, also sat in a corner of many homes until very recently. These days, the bulky CRT televisions have been replaced almost entirely by flat screens. In 2008, sales of flat panel displays overtook CRT screens worldwide, and the world has never looked back. The switch made laptops and smartphones possible because it made them portable. The new displays are also controlled by electrons, but in a much more sophisticated way. The screen is split into many tiny boxes called pixels, and electronic control of each pixel determines whether or not it gives out light. If you have a screen resolution that is 1280 × 800 pixels, that means that you’re looking at a grid made up of just over a million individual dots of color, each separately switched on and off with tiny voltages, and each updated at least sixty times every second. It’s an astonishing feat of coordination, but it’s still trivial compared to what your laptop gets up to.
Let’s return to the magnets. A magnetic field can push electrons around, and so it can control electric currents. But that’s not the limit of the interlinking of electricity and magnetism. Electric currents also make their own magnetic fields.
AS WE SAW in chapter 5, toasters heat toast very efficiently using infrared light. But the real brilliance of a toaster isn’t that it provides lots of heat—your grill can do that; it’s that it knows when to stop. The universal rule of toasters is that the bread only disappears down into the innards of the toaster when you press on a lever at one side. If you don’t press it all the way down, it pops right back up. But if you push the lever all the way to the bottom, there’s a click and it stays put until it’s time for the hot toast to pop out of its mini-furnace. I don’t need to stand over it, checking how well browned the bread is. When the bread has turned into toast, there will be another mechanical click and the toast will pop up by itself. So as I prowl around the kitchen, looking for butter and jam, something is holding the bread in place.