Is there a science of strings?

August 27, 2007 8:09 AM

How and why cables/strings/hoses/lines/cords etc. become entangled? Is there any scientific explanation of the process and more generally a science studying the physical/topological properties and behaviour of string materials?

It's always been a mystery to me that any number of cables left alone for a while end up in complex structures (like knots) that would take some energy to create from scratch. Of course, they're not really "alone": energy is brought by the external forces (people, wind...) that move them. But I'm still wondering whether the process of transforming a series of separate cables into an unruly (or organised?) tangle is being studied? Is there a "science of strings" like there is a science of granular materials?

posted by elgilito to science & nature (6 comments total)

there's knot theory, but it's more static than what you are looking for, i think.
posted by andrew cooke at 8:25 AM on August 27, 2007

Knot theory
posted by ormondsacker at 8:25 AM on August 27, 2007

this seems like a useful starting point. "entanglement" seems to be a good search term, along with "knot" and "dynamic".
posted by andrew cooke at 8:27 AM on August 27, 2007

Next up, how posts become entangled.

In my intro knot theory class, they did emphasize repeatedly that knot theory only studies closed loops. What you're looking for is actually closer to braid theory or tangle theory.
posted by ormondsacker at 8:43 AM on August 27, 2007

Well, this isn't really an answer to your question, but my daily work as a syadmin has taught me:

*) Cables are generally sheathed with a rubber/plastic coating. As the cables are wound, usually at the factory, one side of the cable is stretched a little, while the other side is compressed.
*) Because of this stress on the sheathing material, cables like to twist and coil. Think of the coiled cords on a telephone handset and how they get messed up. Then imagine 30 such cords just kinda hanging out together.
*) Different cords will have different sheath materials, so will coil differently. As such, a bunch of different cords will coil around each other in a knot like fashion.
*) People don't connect cords in parallel, they thread them through and around each other, creating the loops necessary to knot them.
*) Even cords that aren't entangled or looped will knot, as loops can thread through other loops. A good example of this is a poorly wound vacuum cleaner cord, all the knots are just loops catching on each other.

To overcome this:
*) Save the twist ties you get in every electronics box that contains cords.
*) "Wind" cables in a circular motion on your off hand, against the palm/fingers, holding the end between your thumb and the part of your hand below your index finger.
*) Don't wind the cable, give it a slight quarter twist between thumb and finger such that the cable wants to form a loop by itself.
*) Use this natural loop to form the circle of the cable and hold the loop with your off hand.
*) Repeat.
*) Use 2 twist ties to keep the cable coil circular.

If you do this repeatedly to a cable, such as a vacuum cleaner cable, you'll find that over time it will want to coil for you.

To organise cables, just unwind as much as you need from the coil you made and twist tie the rest. Keep the cable "run" as short as you can and you have less chance of knotting.

(I wish I could draw or shoot video!)

(also, that was way too much information!)
posted by Danaid at 9:26 AM on August 27, 2007 [2 favorites]

There are some very useful heuristic explanations. As mentioned, wire is stressed and twisted during manufacture. Also, repetitive use in a certain way can add unexpected twisting. Back when phone handsets had wires you'd sometimes get very strange spaghetti knotting because some people would always add a twist when they went through a pick up the receiver put down the receiver cycle. Finally, the same kind of twist adding happens when you wind up long wires. Winding wires by alternating the twist direction can solve a lot of tangling problems.

I think another aspect of the problem comes up from combining the human twisting and manufacturing stress mechanisms. If you try to untwist a twisted wire (like hanging a phone handset and letting it spin out the extra twistyness), it can sometimes make the problem worse..
posted by Chuckles at 8:48 PM on August 27, 2007