Being one, I subscribe to Straight Dope. Today has a couple of doozies, one of which you can even try out at home.
Dear Cecil: I know this is going to sound crazy, but my Slinky (that's the Original Slinky Walking Spring Toy) has the power to turn on, turn off, and change channels on our TV set! Shortly after receiving the Slinky as a birthday gift, I was watching TV and absentmindedly tumbling the Slinky back and forth in my hands. The TV went off, then came back on a minute or two later. At first I figured our TV was on the blink. But when the TV switched itself on the next time I played with the Slinky the truth dawned. Since then, all our friends and visitors have experienced firsthand the power of Slinky. We can turn the TV off and on and change channels. My brother was even able to adjust the volume. There is no physical contact between the Slinky and the TV. It works best from a chair about six feet from the set. Can you explain this? --Karen Schrage, Chicago Cecil replies: It's questions like this that give me the strength to go on. To be sure, I had heard of such things before. But most of the letters were along the lines of the following: "How come when you hold a chopstick in your teeth and pluck it, the TV screen shimmies? Nothing else shimmies." Clearly a case of heavy-metal poisoning, although whether from cadmium or Aerosmith is hard to say. Karen's letter, however, was refreshingly rational. We called to check one vital detail: did the set have an ordinary remote control? Karen didn't know, but the set was pretty old (it had come with the apartment), and it might have had one once. That was all we needed to know. Prior to the early 1980s, most TV remote controls communicated with the set via ultrasonic sound-- sound too high-pitched for the human ear to hear. Typically these devices worked by striking a series of metal bars with a tiny hammer. There was usually an audible click, but the frequencies that actually did the job were inaudible harmonics. (You acoustics buffs will know what I'm talking about.) Obviously you don't need a remote control box to bang metal together, although getting the right frequencies is a bit hit-and-miss. A call to the folks at Zenith, which introduced the first ultrasonic remote control in 1956, confirmed that there had been occasional reports of kids switching channels by spilling pennies onto the floor from their piggy banks. We had also heard of people switching on TVs by jingling their keys. When Karen told us someone had turned her set on by jingling keys too, we concluded the Slinky was mimicking a long- lost ultrasonic remote control. Unfortunately for those of you who were looking forward to a pleasant evening of experimenting on your own (why stop with Slinkies? why not anvils and sledgehammers, Caribbean steel drums, or samurai swords?), ultrasonic remote controls are now obsolete. They've been supplanted by infrared (invisible light) technology, which is better suited to conveying the complex digital information needed to operate today's plethora of TV controls. Nothing fun ever lasts. WHEN WILL I LEARN? Dear Cecil: Recently you put down an anonymous writer who asked, "How come when you hold a chopstick in your teeth and pluck it, the TV screen shimmies? Nothing else shimmies." You ascribed the effect to heavy metal poisoning. Well, Cece, I think you dismissed the question prematurely, without trying it. This effect does occur and results from a vibration of the eyes (connected to the tooth bone) at a frequency near that of the vertical scan rate on the TV, producing a visible modulation effect of shimmying, speaking vernacularly. The other objects in the visual field may appear slightly fuzzy, but they don't shimmer. Chopsticks are fine, but if you want to see the effect more clearly, vibrate your jaw or head with an electric vibrator using different speeds while viewing TV. Hope this shakes you. Find that letter and apologize. --Jim S., Dallas Dear Jim: I can't stand it. Every time I rummage through the circular file looking for a letter exemplifying the depths to which the Teeming Millions have sunk--believe me, you'd feel the same impulse if you had this job--I come up with somebody who's tapped into some lost truth of physics. As a matter of fact, I did try this silly stunt-- once. But not being the kind of guy who believes in doing it with the shades drawn, I used a well-lit room, which made the effect a lot less noticeable. Having returned to the (darkened) lab, I find that, sho 'nuff, the screen does shimmy. To be more precise, it looks as though it had turned into a jiggling sheet of Jell-O. Very bizarre. Had we discovered this in the 60s it might have replaced the lava lamp. A ripple effect of this sort is characteristic of interference between two wavefronts, in this case the chopstick- (or spoon- or crunchy candy-) induced vibration in your skull and the flicker of the TV. The precise mechanism of this interference I leave to the grad students to figure out, but it happens all right. --CECIL ADAMS
