The answer “because they just do” could possibly be your first response to the question (indeed, it was mine), but it’s knot a good one (Yeah, yeah, I know…)
In fact, it must do with Entropy (the 2nd rule of thermodynamics) and things tending toward ailment. In fact, the world seems to exist in a situation of prepared chaos (or chaotic order, whichever way you select to see it) and your headphones are obeying the order of the Universe by producing chaos whilst inside your pocket. Perhaps.
Alternatively, Summer Ash of ‘NPR.org’ claims that,
“Mathematicians have studied knots forever and developed all sorts of theories and classifications of their variations, but physicists have only recently began to explore what equations govern their formation”.
She goes on to explain an experiment, administered by Physicists Douglas Smith and Dorain Raymer, which involved spinning a length of string using a motor to check if it was tangled or not, they did this 3,415 times. Why that specific number?
Well, depending on Smith, “The scientific answer is that 3,415 was around the point where we had statistically compelling results. The human answer is that 3,415 times was about as much as we could stand.”
You wouldn’t expect a man who appears to have taken the idea ‘String Theory’ exactly to own a sense of humour, but there you go. I’ll let Summer explain the remainder;
“They concluded that with a minimum length of string (18.124 inches) and sufficient space for the string to shift around in its container, knots formed fairly quickly, often within the first few seconds. Inputting these results into a computer model, they even managed to create a program that could identify the “Jones polynomial” for each resulting knot, a mathematical property based on parameters such as the number of string crossings”.
Ergo, when you think about the length of the earphone chord and how much space these have to move around within your pocket (especially when you’re out and about, going to/from work, jogging, walking the dog or whatever), it will become clear which you’re knot going to avoid the odd entanglements (sorry. I’ll stop now). It is just physics. In reality, if it doesn’t happen all the time, you have most likely beaten odds close to winning a decent amount on the lottery. Consider that.
Nevertheless, to sum up, today, we have now learned together that entangled earphone cables are a normal symptom of business as usual within the Universe. It’s indicative of the great wide somewhere winking down at us and reassuring us that it’s all going to be alright and that everything is going exactly according to plan. A means of saying the days of our lives are as destined as every grain of sand on every single beach on each world in each galaxy…
Or, if you like, the Universe is basically a Grant Morrison re-write of the Phillip K. Dick wet dream.
Or, if you favor:
Headphones get tangled up within your pocket. Why? Because they just do.