Issue 7 - February 2001
According to Murphy's Law, "If something can go wrong, it will". And according to physicist Robert Matthews, it can be seen at work in many everyday phenomena.
Have you ever wondered why the supermarket queue you're standing in so often gets beaten by the one next to you ? Or why the place you're looking for in an atlas is so often on the awkward bit of the map ? Or why string or rope ties itself in knots at the slightest provocation ?
Like everyone else, Robert Matthews of Aston University in Birmingham has put up with all these irritations over the years. But instead of just dismissing them as just part of life's frustrations, he's looked into the science behind them. And he's found that in many cases, it's possible to show scientifically that Murphy's Law really is at work...
Take that case of the supermarket queue. Why does the one we pick so often get beaten by the one next to us ? As Robert explains, if we pick a long queue, or one with a family of 12 shopping for the winter, then it's not hard to see why your queue will be beaten. But, says Robert, scientists insist that in the long run all the queues are as likely to finish first as any other, so there just can't be a "Murphy's Law of Queues": that if your queue can be beaten, it will be.
"The trouble with this argument is that on any one visit to the supermarket, we don't care about 'the long run' ", says Robert, "We just want our queue to finish first on that occasion. And if there are N queues, the chances that we've picked the fastest-moving one on that trip is just 1 / N".
And, says Robert, this holds the key to the reality of Murphy's Law of Queues: "When we queue up, there are three queues we care about: the one we're in, plus the two queues to either side. So the chances our queue will beat both our neighbours is just 1 in 3. In other words, in almost 70 per cent of trips to the supermarket, Murphy's Law will prove correct, and one or other of the queues next to us will beat ours !"
Over the years Robert has investigated many other manifestations of Murphy's Law. For example, why is it that when we're using a road atlas, the place we want so often turns up on the awkward part of the map, down the central crease or on the edge ? The answer, he says, is that although those "awkward parts" don't seem very wide, they track the total perimeter of the map - and simple geometry shows they actually take up over 50 per cent of its total area. So a location picked at random in an atlas has a 50:50 chance of turning up in the map's awkward "Murphy Zone".
For more details of the sums behind this result, check out Robert's web-page on Murphy's Law of Maps:
And if you want to find out why rope gets knotted so easily, take a look at his paper on Murphy's Law of Rope:
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