Storm in a Teacup: The Physics of Everyday Life(45)

Just after midnight on April 15, 1912, circular pulses of radio waves were rippling outward from a handful of spots in the North Atlantic Ocean. The patterns started and stopped sporadically, and each one faded as the ripple traveled outward from its source. Some of the ripples reached the other spots that were broadcasting, and these were relayed on. The strongest ripples of all came from a spot 400 miles south of Newfoundland in Canada, where Jack Phillips was using one of the most powerful marine radio transmitters in service to beg for help. The gigantic RMS Titanic, the largest ship in the world, was sinking. Jack was up on the boat deck, at the top of the ship, sending short electric pulses up to the antenna, which was strung between the funnels. The oscillations in the aerial wire sent crude bursts of radio waves out from the ship, and the radio operators of other ships could decode the pattern and understand the message.

Radio only works because waves like this don’t travel in a single direction, but ripple outward in all directions. You don’t need to know the exact position of the person who’s listening, and many different people can listen to the same waves. The pulses that the Titanic sent out could be detected by the Carpathia, the Baltic, the Olympic, and several other ships within a few hundred miles. The information transmitted may have been limited and the means clumsy, but for the first time in human history it was possible to have a conversation across an ocean. The arrival of radio technology changed shipping forever. Twenty years earlier, the Titanic would have disappeared beneath the waves alone and it would have taken a week or so to work out that it had gone. The first transatlantic radio signal had been sent only ten years previously. But that night, via the waves rippling out through the dark, nearby ships were connected to the tragedy as it happened. The staccato pulses weren’t random. The ripples came in patterns, and each pattern conveyed a message sent by one human, broadcast out across the vast distances of the ocean at the speed of light. It represented a huge revolution in human communication. This was the roar that signaled the real beginning of the age of radio.

One of the reasons why the demise of the Titanic is so famous is that it happened on the cusp of this new age. It showed the enormous potential of radio waves—the RMS Carpathia did arrive two hours after Titanic sank, in time to save many lives. But it also showed that the radio system of the time was really too crude to be useful. Messages were slow to send, and some of the warnings of icebergs that the Titanic had received were lost in the flood of trivial or more general messages. More importantly, using crude bursts of waves meant that signals easily got confused. Who was speaking and who was listening? Messages might not be heard in their entirety, or they might not be heard at all. To use waves to send information, you need to alter them in some way, so that the receiver can see a pattern. But all these ships had was “on” and “off”—a burst of radio waves or nothing. There was only one channel, and everyone had to share.

Radio waves weren’t the only waves zooming over the ocean that night. The Titanic sent up distress flares and the nearby Californian tried to communicate with her by using Morse lamps, sending out flashes of visible light. But the radio waves could travel much farther, because of a convenient quirk of the atmosphere. An upper atmospheric layer (called the ionosphere) acts as a partial mirror for radio waves. So the radio signals from the Titanic weren’t just sweeping outward over the surface of the ocean; they were bouncing up into the atmosphere and then back down again. This is why radio waves can travel across oceans, even though the curvature of the Earth means that there’s no line of sight between sender and receiver. Reflecting waves can travel around a planet, because the reflections help them get around the curved surface. There’s no equivalent mirror in the sky for visible light.

Jack Phillips continued to fill the night sky with pulses of radio waves, broadcasting the ship’s position to anyone who was listening until water flooded into the wireless room. He didn’t survive, but long-distance communication by radio waves meant that 706 others out of the 2,223 on board did. And they lived to see a world that went from total radio silence to a cacophony of communication via these invisible waves. Almost nowhere on Earth is untouched by them now, and human civilization is interconnected as never before.

Light waves rule our world. They are the vehicle that delivers to us the tiny fraction of solar leftovers that power our planet. They connect us to the rest of the universe. But in the past century, our civilization started to develop a new relationship with the suite of all possible light waves, the electromagnetic spectrum. Where once we were passive consumers, grateful for the energy and information that accidentally came our way, now we are prolific producers and users of light waves. Our sophistication at manipulating light has opened the doors to colossal skill at monitoring our world, the ability to broadcast information almost instantly to almost every living human, and being able to talk, right now, to any individual on the planet in possession of a mobile phone.

But you can only make sense of the flood of waves if you have some way to separate out the many messages being sent. Fortunately, the waves themselves provide the answer, and you don’t need any specialist kit to see it for yourself.

The Great Smoky Mountains in Tennessee are spectacular, a huge stretch of valleys and peaks blanketed by deep green forest. The serenity and untouched feel of the forest were particularly striking because to get there we had to drive through Dolly Parton’s home town. I knew of the great country singer, of course, but I wasn’t prepared for the sight of Dollywood, a huge theme park celebrating Tennessee, country music, fairground rides, and of course Dolly herself. And that’s just the epicenter. Pink cowboy hats, highly decorated guitars, and an all-pervasive background of country music seep into the surrounding towns, along with big blond hair, vintage denim jackets, and a big Southern welcome. Bourbon after dinner seemed to be a cultural imperative, although secretly I’d have preferred a cowboy hat. But it all changed when we got up into the mountains the following day. Crowds flocked in with deck chairs and drink coolers, and quietly set themselves up to watch the forest. Anything other than complete darkness would spoil the show, so all lights were extinguished, and flashlights and phones were forbidden. As dusk fell, the dance of the fireflies began. The forest sparkled with the flashing of millions of tiny broadcasting insects. We were there to make a science documentary, and we had just one evening to capture the whole event. The problem with filming something like this is that you need to move about and to be able to see where you’re going. We had been told that if we really had to, we could use red lights, as apparently they won’t disturb the fireflies as much as white lights. So we crept around the forest, dimly glowing red. By about 1 a.m., the fireflies had mostly stopped, and we were preparing to film the last segment. While the director and cameraman were setting up lights, I parked myself in a pitch-black clearing with my red headlamp, huddled under a piece of blackout cloth because of the cold, and scribbled notes about what I was going to say. When the others were ready, I went to join them, and opened my notebook for a last reminder of the ideas I’d had. But under the director’s white headlamp, I couldn’t read my notes. On the page were two sets of scribbles, one in red pen and one in blue, right on top of each other. It was impossible to read either one.