If you have earbuds, or in-ear headphones, you know that sooner or later, they get tangled up. It appears that a visiting physicist in Aston University in Birmingham, England has a mathematical theory on how it happens, and proposes a way to store the darn thing without it tangling.
Matthews’ years of study suggest that clipping the two earbuds together, then attaching them to the end near the audio jack to form a loop, will cause a tenfold reduction in knot formation.“First, by forming the loop you've effectively reduced the length of string able to explore the 3D space by 50 per cent, which makes a big difference.” Matthews said. “Second, you've also eliminated the two ends, which are the prime movers of knot formation.”
Unfortunately, as is a common practice in the popular media, they didn't cite source or if this has been published, or submitted for publication. Heaven forbid, a reader of their website would actually want to look it up and study this closer than beyond their superficial reporting.
Addendum. The Daily Mail has a bit more to say about this than the above website.