We’ve all done it. You put in the weekly wash with its usual 12 dark socks, a pair for every day except Sunday (I know, I know but let him who is without sin throw the first smelly shoe). But when the spin cycle ends and you take out the load, one of the identical socks has gone missing. You search inside the duvet cover, in the sleeves of jumpers and shirts, even inside other socks. And to be fair one does sometimes pop back into the known universe. And when you replace your washing machine you are likely to find one dusty old sock snuggling behind the hot water pipe, lonely but dry. But over the years every month or so a genuinely odd number emerges despite an even number going in. So where do they go?
It has puzzled me since I first visited the launderette as a student and persisted through washing machine renting then ownership. Where do the odd socks go? Then suddenly it stopped.
Needing to top up my sock drawer I grabbed a pack of twelve cotton rich in the supermarket. They were black, of course, but each pair had a different coloured stripe round the toe and each colour spelled out a day of the week – Tuesday was a yellow stripe, Friday green and so on. Of course, when I wore them I ignored the days – no-one can say I don’t still have a youthful streak of rebellion – though I was curious as to which day would begin to disappear first as they came out of the washday drum.
But when I came to fold and match my washing I had the jigsaw-completing joy of six socks of each stripe. The same thing happened the following week. And the next. In fact in the nine months I have been using these colour coded socks not a single one has gone missing (I don’t count the week when I thought one had only to discover the unmatched singleton still unwashed in the bottom corner of the basket).
There is only one explanation of these observations – quantum physics. It is well said that anyone who thinks they understand quantum physics is mistaken. The famous two slit experiment found that if you fire single photons through a pair of slits then each single particle will go through both slits as if it was a wave and leave a wave interference pattern where it strikes the wall behind. But if you set up a way of measuring which slit they go through they will form two distinct clumps as if each photon had gone through one or the other. So measuring what they do – or rather setting up a mechanism to measure it – changes the nature of particles ‘on the quantum scale’ – a scientist’s way of saying ‘no, we don’t know how it works either.’
Normally quantum effects apply only to very tiny particles like photons or electrons. But my sock phenomenon is clearly a quantum event. If the socks are all identical you cannot watch each pair in and watch each pair out. All you can do is count them afterwards. But if they have a different coloured stripe on the toe they can be watched in pair by pair and then counted out pair by pair. It doesn’t matter whether you actually watch them or not. The fact you have set up the measuring device – the coloured stripes – causes the collapse of the wave function into a singularity.
Until now the largest particle that has been shown to exhibit quantum effects is a complex carbon molecule. My washed socks take the quantum universe into a new domestic domain.