Physicists untangle the geometry of rope
Twine, string, cord or cable, it all winds up the same way
Researchers have unraveled the mathematics that keeps ropes from unwinding.
![](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2010/04/12271.jpg?resize=300%2C176&ssl=1)
The trick lies in the number of times each strand in a rope is twisted, say Jakob Bohr and Kasper Olsen, physicists at the Technical University of Denmark in Lyngby. Their paper was posted online April 6 at arXiv.org.
In a traditional rope, each individual strand is twisted as much as possible in one direction. The twisted strands are then wound together in a spiral shape called a helix, which itself rotates in the opposite direction. The interlocking of these twists and countertwists gives the rope strength so that when yanked, it does not unwind.