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A PHYSICIST WRITES . . .
(November 2011)
From October into November ... first the tedious task of tracking down every clock, watch and timer in the house (and not forgetting mobile phones, clocks in the cars etc) to put them back an hour, and then the ordeal of resetting the body clock, which takes me a week and loses me an hour of sleep every morning until I’ve done it.
I wouldn’t care whether we went for GMT, BST, CET or an Irish time-zone if there was one (instead, they enjoy up to an extra half-hour of evening light simply by aligning with our time) as long as we stuck to it and didn’t keep changing twice a year. How I envy the Russians, who have decided – or have been told – not to readjust their clocks (ticking and body) any more. They discovered, apparently, that the six-monthly switch was causing a 50% increase in the occurrence of heart attacks and suicides.
Something else I notice as the evenings darken is the number of vehicles with one or both headlights maladjusted and dazzling me, either from ahead or in my rear-view mirror. You would think that their drivers would be aware of the problem and would want to do something to correct it pronto, for their own safety. Out-of-town, single-carriageway roads are enough of a hazard in daylight, with only the white line there to keep opposing traffic apart at closing speeds of up to 120 mph. After dark, with headlight glare added, they must be the most dangerous roads of all.
Don’t stop me if you think I’ve said all this before (which I have, some of it anyway), because it’s leading me on to a new tale. The headlights on my Corolla have never needed adjustment – until a few weeks ago, when I realized that sometime since last winter’s darkness both of them had tilted down significantly. Full beam didn’t point horizontally, and when dipped their ‘upper cut-off’ was clearly visible on the road not far ahead. My first thought was that one of the two garages I had recently visited (for servicing and for an MOT) might have adjusted the lamps, but when I asked, they both denied it.
Now, like many other models I guess, my car has an adjustment control inside for when it’s loaded in the rear and you actually want to lower the headlight aim. I had always kept it at 1.5 (on a scale from 0 to 5) which put the dipped cut-off at just below the horizontal, on the car in front. The control was still working, but now even on zero the angle was wrong. Because both lamps had dropped together, I concluded the problem lay in the adjustment-control electrics.
I extracted the control to discover below it not a simple connector as I’d hoped, but a complicated printed circuit. So I decided to leave (un)well alone, and turned my attention to the headlights themselves. I located their manual adjustment points, which were strange hard-to-reach toothed wheels. Eventually I worked out that these were meant to be turned with a thin screwdriver poked, without difficulty, down into the teeth. But how to see clearly where the headlight beams were pointing, in daylight (so that I could see what I was doing with the screwdriver)?
Having moved the Corolla down the driveway, I tried shining its headlights on white surfaces, black surfaces, the garage door (it’s lime green, if you are curious), Mrs S’s Micra, then anything else I could think of, but with no visible throw-back at all. Then finally I hit upon my yellow reflective hi-vis vest. Success! With its white stripes hanging vertically and at a distance, and with my eye down near each headlight, I could see exactly what the beam was doing and, in particular, where the dipped upper cut-off was.
Checking first that the in-car adjustment was turned to zero, I managed to bring each beam up to roughly the right position (and level with each other). Later, on the road at night, they turned out to be perfectly adjusted. But how long will they stay this way...?
Let me go back again, to a column I wrote about different sorts of illumination. I mentioned that the brighter gas-discharge headlights you often see are much harder on the eye than the standard ones, not least because the light comes from a narrower aperture. So you get bright spots before the eyes, just when you don’t want them. And I do rather wonder now how close these lamps are getting to having the effect of the Sun during an eclipse: when it's showing just a small part of its intensely bright surface, you can quite easily look straight at it, but you will very easily burn the retinas of your eyes permanently if you do.
I then went on to discuss fluorescent energy-saving bulbs. These are not nearly bright enough to serve as headlights, but they are up to five times more efficient, that’s 400% more efficient (because 1 + 4 = 5), than ordinary incandescent bulbs. Or to put it another way, they draw one-fifth (0.2) of the electrical power, that’s 80% less power (because 1 – 0.8 = 0.2), for the same light output. I pointed a scornful finger at a national newspaper which had managed to misconstrue these percentages by telling us that low-energy bulbs were “80% more efficient” than the others.
That’s less than twice the efficiency – much less impressive than the true figure. And now what do I read in this month’s Which? magazine: “Fluorescent lamps are 60–80% more efficient than incandescents.” Well! If this glossy consumer journal can’t get ‘simple’ percentages right, how can we trust its more weighty reports and comparisons? I hope to see a correction and an apology in the next issue. Also the helpful comment that I sent in.
[The Which? website version of the magazine report initially made the same absurdly timid claim for fluorescents. After I contacted them a second time, it was corrected to: “...use 60–80% less energy...”. But does even this make the average reader appreciate that they are up to five times more efficient? As I said in my ‘helpful comment’, percentages are far better avoided when you are talking about changes or comparisons that are more than a factor of two in size. Meanwhile, I await the December magazine.]
Peter Soul
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