Anyone who has kept earphones in their pocket knows this: a wire left loose in a confined space has a natural tendency to form knots. This “Murphy’s law” of the threads does not even spare the Christmas decorations: we challenge anyone who has decorated their Christmas tree with the classic Christmas lights not to have cursed to unravel the tangle that spontaneously formed, in spite of the care with which it had been placed the previous year.
The study on thread knots in a box
In 2007 Dorian Raymer And Douglas Smithtwo researchers from the University of Chicago, conducted a conceptually very simple experiment: they inserted wires of different lengths into a box and shook the box. You won’t be surprised to discover that the threads have systematically formed knots, tangling spontaneously. On 3415 tests accomplished, the two researchers found 120 types of knots different. The “ability” of the threads to form knots increased with length and – according to the results of Raymer and Smith – drops to zero below i 46 centimetres: threads shorter than this do not knot. But Christmas lights are several meters long, so the possibility of creating chaos in their boxes is practically a certainty.
From a scientific point of view it is simply statistics: they exist thousands of ways in which a thread can be knotted, but only one in which it can be perfectly ordered. In short, “knotted” states are much more probable than “ordered” states. This means that, starting from an ordered configuration, any variation (even just moving the decoration box to the cellar or attic) takes the system towards a decidedly more probable state, that is, knotted.
If this reminds you of the concept of entropyyou are not mistaken. In statistical mechanics, entropy is precisely an index of the number of states associated with a particular condition, which in this context we can call “knotted thread” and “ordered thread”. In nature, entropy increases simply because as systems evolve they tend towards more probable states, which we tend to consider more “disordered” than probable ones.
We must then consider the particular shape of Christmas lights, whose cable is made of copper (therefore a relatively rigid material) and above all they have many bulbs, which act a bit like “leverage points” that the cable can use to form knots.
How to prevent Christmas lights from getting tangled
Unfortunately there is little that can be done against the unstoppable law of entropy: the lights will always tend, statistically, to become knotted. However, we can use very simple tricks to avoid the formation of knots upstream.
For example, wrap Christmas lights around cardboardor otherwise rigid material: as long as the cable remains firmly fixed in place, it will be much more difficult for it to move enough to end up forming knots. Another obvious solution is wrap the lights in a circle and attach the circle in several placesalways with a view to limiting the freedom of movement of the cable.
