|
 previous / next column
A PHYSICIST WRITES . . .
(January 2014)
Let us consider some topics that I caught sight of last year, before they become absurdly old news. Actually, one item looked absurd even when it was new (but then we were in the middle of the August silly season): Birds observe speed limits, even if motorists don’t. This was a rather confusing newspaper headline, over a story based on a report in a biology-research journal, by two Canadians working in France. Driving at a variety of speeds on country roads with speed limits that ranged widely from 20 to 110 km per hour, they measured – by calculation from speed and time – the distance ahead at which birds took flight to avoid being run over.
I assume that bird-scaring wasn’t their main research activity! But anyway, the results of this investigation were intriguing. Birds, it seems, take almost no account of the actual approach speed of a car but instead blithely assume, for the purposes of escape, that it’s travelling at the speed limit. Or to put it more accurately, they wait (before jumping) until the vehicle is at a distance that depends mainly on the size of the limit.
Naturally this doesn’t imply that the birds first looked at or “observed” the speed-limit signs. The researchers’ conclusion was that each bird adapted its behaviour to the typical speeds on its own patch (rather than assessing the speed of each vehicle). Plausible? Maybe so – though I did find a correction in a later issue of the journal: “Our statement that the reaction-distances were longer in spring and summer (than in autumn and winter) should have said that they were shorter.” This suggests that something became inverted during the analysis ... a verre de vin, maybe?
In July, Brittania Rescue published a survey of awareness of dashboard warning lights: 2000 drivers were shown 16 common symbols and asked to identify them. Only 2% of those questioned succeeded fully, 35% failed to recognize the tyre-pressure warning, and 71% couldn’t give a name to the airbag-fault symbol. (What doesn’t help is that across all makes of car, at least 100 different warning and indicator symbols are in use.) Worse, a significant number of drivers admitted to ignoring a warning light and driving on, for a week or more. And getting the problem fixed then cost them on average twice as much as an immediate investigation cost others: be warned!
Failing all else, of course, read the instructions. The manual for my VW Golf lists 37 distinct dashboard symbols. I think I've seen 23 of them lit up at various times (many appear briefly when I switch the ignition on, for example). Two others are diesel-related and therefore irrelevant. But what about the remaining twelve symbols in the book: do they relate to equipment or sensors that aren’t fitted to this car, or have their lights perhaps failed? I shall have to investigate...
A BBC2 Horizon programme in October was entitled A guide to car crashes, and offered a potted history of attempts to bring down the death toll on the roads. Something that I hadn’t understood properly before concerned shocks to the brain. The lasting damage from these may not occur until hours after the accident: it’s possible for someone to appear and to feel almost normal for a while, before a delayed and irreversible reaction sets in. When this was realized, a couple of decades ago, it led to a significant improvement in casualty rates. Nowadays, paramedics should be aware of the need to get even apparently unaffected accident victims to hospital for urgent assessment, and treatment if needed.
In November I encountered not only the largest percentage value I have ever seen or heard stated, but also a simple word that was new to me (though evidently not to many other people): the publishers of Oxford Dictionaries announced that their chosen Word Of The Year was “selfie”, and that its rate of usage had increased by 17,000% in twelve months.
You won’t need me to explain the word here, I’m sure. But to get any sensible idea of its growth in popularity you must work out, from the percentage, how many times bigger the usage was at the end of the period compared with the beginning – and I bet not a lot of people can do that. Even I had to think about it! What’s your guess at this growth-multiple?
I felt obliged to contact the publishers in order to check their calculation of such a huge percentage increase, and to point out how uninformative it was (to the general public). But they wouldn’t reveal to me the numbers used in working it out. Nor did they admit to agreeing with me that it’s rarely helpful to use a percentage for describing any change in a quantity that’s more than a factor of two (ie, going beyond a 100% rise or, the other way, a 50% decrease). Still, they did say they would take note of my comments when they came to reveal the 2014 Word Of The Year...
[Did you guess the multiple represented by the 17,000% increase: strictly, it’s “171 times bigger” (not 170) – though that’s assuming we can trust the publishers’ calculation.]
Finally, Mercedes announced last year that their W222 S-Class luxury saloon would feature a stereo camera at the front, for “Magic Body Control”: a system that rapidly analyses images of the road surface up to 15 metres ahead and prepares the suspension for any approaching bump or pothole. Said a spokesman: “You don’t feel a thing from bumps up to 18 cm high, and traffic-calming speed humps are especially well handled.” Isn’t that just great news, for road safety? The bad (or rather, quietly satisfying) news is that the system is unable to detect potholes full of rainwater...
Peter Soul
previous / next column
|
