About me

For my professional website, with information about my research, publications and teaching, see www.sites.google.com/site/rmlevans.

Monday, 18 November 2013

Good Old-Fashioned Technology

Remember the good old days when micro-electronics were traditional and wholesome? OK, perhaps my sense of nostalgia is a mite over-developed, but I have noticed an unfortunate trend in recent technological developments. While it is nice to have affordable tech with almost magical power, the slickness of the designers' art has a tendency to conceal the real world from us. I care about that because, as a physicist and an educator, my raison d'être is to reveal the real world.

I don't want to over-state the case because, actually, I love new gizmos that allow me to browse my music collection through my TV and to photograph the Orion Nebula in mere moments using the unbelievably sensitive ISO25600 setting on my camera. I wouldn't want to halt the inevitable march of progress even if I could. But I would like to take this opportunity to mark the passing of some dearly loved and enlightening technology that has gone the way of all flesh.


Magnetic entertainment
Take, for instance, the cathode ray tube (CRT). Until about ten years ago, all televisions lit up our livingrooms by smashing high-energy electrons into phosphorescent pixels inside a glass vacuum tube. The elementary particles were launched from an electron gun at the back of the TV, in which they leapt from a hot, negatively charged electrode and raced towards a positive electrode, narrowly missed it, and hit the screen instead. A negative electrode is called a cathode, hence the electrons were dubbed "cathode rays" before J. J. Thompson discovered their true identity. The name stuck.

The CRT was a real-life particle accelerator residing in every home and, in retrospect, it was an absolute gift to all physics teachers. It's harder to teach about electrons if students have to take their existence on trust, or observe them only inside some arcane laboratory glassware.

Credit: Marcin Białek
Anyone with a magnet and a sense of mischief could discover how their traditional telly steered its beam of charged particles magnetically. Before consigning my own idiot-lantern to the tip last month, I took these pictures that show a magnet exerting a Lorentz force on the electrons, making them swerve and hit the wrong pixel. (It's slightly risky to do this if you want to keep your TV, as it could become permanently magnetized!)


Analogue ghosts
The switch-over from analogue to digital TV signals has robbed us of another neat physics demo. "Ghosting" was an annoying artefact that appeared on the screen if you used the wrong type of aerial cable. The people in TV-land each seemed to be stalked by a spectral doppelganger standing a few inches to their right.
Credit: Cablefax.com
Back in the analogue age, it was a familiar sight in any students' TV lounge, and I used to discuss it in my "Vibrations and Waves" lectures as a nice example of impedance-mismatching. You see, the electromagnetic oscillations, picked up by the TV aerial, travel as waves down a co-ax cable to the television. Like any wave-carrying medium, this cable is characterised by a wave-impedance that indicates how much power is needed to push a given size of wave along it. If the wave meets a joint between two cables with different impedances, only part of its power continues through the second cable to the telly. Some fraction of the signal is reflected back along the first cable, where it bounces off the aerial and sets out again towards the TV, slightly delayed. So the same signal arrives twice at the TV, resulting in a double image.

These days, the electromagnetic waves still perform the same physics as ever, echoing off mismatched cables. But the digital encoding of audio-visual information lets clever circuitry reconstruct a pristine picture from a degraded signal. So we can enjoy our high-brow entertainment without the distraction of aberrant natural phenomena.

Of course, physics lecturers could preface their discussion of wave-impedance by explaining what TV looked like in the olden days, but the relevance of the example is lost. Still, I'm in no position to complain about this development since, like any consumer of electronics, given the choice, I'll opt for the TV with the clearest picture. 
 
Discotheque versus MP3otheque
My record player is another old friend that accompanied the CRT to the dump during this month's domestic clear-out (so I told my wife; it's really hidden in my workshop. Shhh!). Having at last finished converting all my old vinyl into the vastly more convenient MP3 format, before "throwing it out", I used the turntable to teach my young children about sound. It was great fun and, with the music safely backed-up, I could relax about the youngsters scratching the discs.

The wonderful thing about a record is that it's very obviously a frozen sound wave. Look closely at its surface, and the wiggling shape of the sound is there right before your eyes. Peer at the stylus as it follows the groove, and you can see how it shakes in time with the air.

To demonstrate even more directly that sound is nothing more than shaking air, we did away with the intervention of the amplifier by creating a primitive gramophone. It was easily done by rolling a sheet of paper into a cone, and sticking a sharp pin through it near the apex. Gently resting the pin's point on the record as it turns on the turntable makes the paper cone sing with a scratchy human voice. If you still own a turntable, I recommend trying out this magic, but only on discs that you don't mind scratching. With a bit of practise, the demo can be simplified even more, using only a flat sheet of paper and resting one corner of it in the record's groove.

True beauty is flawed
Many new devices distance us from physical phenomena, for the valid reason that they are just much more complicated, and often much smaller, than their forebears. I have little chance of showing my children how MP3 files create sound because, unlike a gramophone stylus, all of the processing is complex and rather abstract.

Other devices shield us from reality only because it is fashionable to do so. For example, when you switch on a fairly old radio - even one with automatic tuning - you hear a few seconds of white or coloured noise as the tuner seeks the right frequency. It's a nice sound, evocative of the electromagnetic physics of the carrier wave. Newer models refuse to engage the speaker until their furtive tuning is completed, and the sterile perfection of the user's experience can be guaranteed. This trend is not confined to radios; it's the reason why a lot of new gadgets are slow to switch on. They are designed not to betray the imperfect physical nature of their workings. That is a shame, because imperfections are important in helping us to understand the world.

Biologists learn how complicated organisms work by observing them going wrong in various ways. One standard technique that geneticists use, to discover the purpose of a gene, is to deliberately break it. They breed organisms in which a particular gene is switched off or made to malfunction. This sheds light on the workings of the genome. In humans, where ethics prevents tampering for the purposes of research, doctors glean the most knowledge by observing imperfections and accidents that arise randomly. Oliver Sachs's book, "The man who mistook his wife for a hat" gives many fascinating examples of brain function that could not have been understood without observing the results of some unfortunate mishaps.

By hiding imperfections from us, the designers of new gadgets are doing us a disservice. Back in the days when cars were basic and unreliable, every motorist knew how an engine worked. Now that they are flawlessly controlled by microprocessors, we have lost those skills and knowledge. As the technologists get better at polishing their performance, our opportunities for insight diminish.

I am glad that some new devices buck the trend and flaunt their mechanisms for all to see. Among the products not afraid to bare all are the TAG Heuer belt-driven wrist-watchDyson's celebrated vacuum cleaners, and most motorbikes. Let's encourage manufacturers to do more of this sort of thing.

Meanwhile, I am making the most of the old gadgets while they are still with us. It's a race against time to show the children how to build a crystal set before the analogue radio signal is switched off. And I have lost count of the number of steam engines and beam engines that we have visited together. Perhaps you can share some other examples of illuminating venerable technology that I should introduce them to before it's too late.

Although I feel misty-eyed at the demise of old machines with all their educational potential, I feel no kinship for the luddites or for King Canute. As simple contraptions disappear, we educators will just have to raise our game. Sic transit gloria mundi.