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A PHYSICIST WRITES . . .
(September 2011)
It’s been a classic silly season. I have tried in recent columns to report fairly on the slow advance of electric cars towards wider acceptance – but in July their cause seemed to be set back considerably by the BBC’sTop Gear (which some might regard as defining the silly season): Jeremy Clarkson and James May took a different model each for a filmed drive, over-dramatically running the batteries down and then desperately searching for charging-points.
It was reported in my paper that one of the manufacturers later complained that although the battery was fully charged when their car had been supplied to the BBC, their monitoring device (a good move, fitting this!) revealed that the vehicle had been “driven extensively”, before the filmed journey started with the battery only 40% charged. A most unfair demonstration of electric cars, in other words (though the newspaper dug the knife in by going on to discuss the problem of ‘range anxiety’ and the possible cost of a replacement battery: £19,000 after maybe 10 years).
Clarkson’s response was that the whole purpose of the film was to emphasize the difficulties of recharging. “At no point did we mislead the viewer. The cars had to be low on charge. That’s how TV works. Don’t believe that electric cars can be run as simply as you have been told: charging them is a pain in the ****.” For all I know, the argument is going on still, to the further detriment of such vehicles. Though it certainly wasn’t obvious to me that the two cars were on low charge from the start.
Our [Thames Valley Group] newsletter editor told me that when seeing mention of winds and weather in my column last time, he thought at first that I might be going to explain the butterfly effect – the notion that “the flap of a butterfly’s wings in Brazil can set off a tornado in Texas.” Well, since he mentioned it, I’ll try ... it’s really telling us that weather is often ‘chaotic’ (in a scientific sense): if the conditions today, locally, were just minutely different from what they actually are, this change could ripple out and completely alter the global weather pattern (from what it would have been) in a few weeks time. The ‘butterfly’ can’t be said to cause the ‘tornado’ – but might just make it possible. And if it did occur, you could think of it as an extreme example of amplification (which I also started to discuss in July).
This process was not really understood or much thought about, until someone who was running a weather prediction on a computer decided to repeat it from a midway stage, but left some of the end decimal digits off the numbers, not thinking it necessary to type them all back in: because of this tiny change (he eventually realized), before his eyes the forecast day by day started to diverge from the previous sequence, until the state of the weather looked utterly different from before. He later presented a report based on his discovery at a scientific conference, but couldn’t think of a title for it. At the last minute someone else came up with the butterfly and tornado sentence above, and so ‘chaos theory’ hit the headlines.
It’s the reason for the impossibility of long (and often short) range accurate forecasting! It occurs to me, though, that a football match offers a much clearer example of chaotic behaviour: a millimetre’s difference in how a boot contacts the ball can alter first the direction of its flight and then, very likely, the whole course of the game.
And is there also a motoring connection? I do believe so. Suppose I give way to another driver, when I need not have done. We each continue on, but slightly behind or ahead of time, compared with what we would have been. Some vehicles along the routes may thus be differently affected by ours, and they in turn will affect others. Scores or perhaps hundreds of people will arrive at their destinations earlier or later than they otherwise would. This is, genuinely, chaos on the roads – though not the serious sort, fortunately!
I’ll let you decide if this next story is a silly-season one or not. The B3001 from Milford across to Farnham is a road we take very rarely (when we do, Mrs S tends to go misty-eyed, as it was her daily school-bus route long ago), but in July we found ourselves on it. At one point, beyond Elstead, I became unsure of the speed limit: any repeaters must have been well hidden in greenery (though I was certain we had emerged from the Elstead 30 limit).
Then we passed a side road with a pair of big 40 signs at the entrance to it. Naturally I deduced that our road had at least a 50 limit ... but then a little further on I saw a 40 repeater! Well, you know me: I contacted Surrey County Council to enquire if the two 40 signs at the junction were not rather large to be acting as repeaters, themselves. There followed a confusing exchange of emails. I kept being told: “They are the correct size for terminal signs.”
Well, I think I’ve now unconfused myself, having studied both the traffic-sign regulations and the manual that explains them to the highways authorities. One regulation says: large terminal signs shall be placed at each end of a road with a speed limit. The next says: this isn’t necessary at a T-junction if the limits are the same on both roads. But evidently Surrey CC, in their wisdom, decided to put terminal signs there anyway, at the risk of misleading someone logical like me. I now drive looking neither to left nor right (only joking).
Finally a real silliness: I’ve no intention of driving in Spain, but (as I wrote here a while ago) I am perplexed by the requirement mentioned in July’s newsletter that if you wear specs then you must carry a spare pair. Obviously it’s a good idea to do so. But let’s say you damage your regular glasses and don the spare pair to drive: you’re now breaking the law (think about it!). Where’s the sense in a regulation that stops you from using the very item it requires you to carry?
Peter Soul
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