Science Questions

Why do wires tangle?

Sun, 6th Jan 2008

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Question

Francis Tapon, San Francisco asked:

I listened to the Naked Scientists podcast while walking across America, and I have a question about tangling wires - I would put my MP3 player into a pocket, and whenever I pull it out the wires are completely tangled up. In fact, they're so tangled I couldn't have done it on purpose! Why do wires tangle up?

Answer

We put this question to Mike Pearson, from Cambridge University's Millennium Mathematics Project.

Tangled headphonesI hear that someone has called in asking about the fact that their headphones get in a mess whenever they put them into a bag. This is one of those things that seems to happen rather more often than it should. Itís kind of surprising what damage a mindless bag can do. There are many more tangled possibilities than there are untangled possibilities if you think of the wires in the bag. In a way just picking one of those tangles is quite improbable but it doesnít really matter. Any old tangled state will do so the probability that one of those tangle states appears when you put your hand into the bag to get your cables out is actually quite high. All we need is something that will allow those wires to move within the bag. We need them to pick up some energy from somewhere and jiggling those headphones around is going to be exactly what we need in order to generate the randomness, the chaos that we need in order to create all these knots. Any old knot will do.

An analogy we might look at is the cells of our body. Thereís an enormous problem that they have keeping all the DNA that they have organised inside the nucleus. You can think of the nucleus as being a tiny, tiny little bag. Itís only about 20Ķm big. The DNA is a big, long string or wire about 3m long. Thatís the equivalent, if you imagine it of having an iPod cable 30km long stuffed into a 20cm bag. How this all happens is quite a problem which has puzzled both biologists and mathematicians a lot.

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Isn't it just a result of then being moved around inside your pocket by the action of walking? As you take a step the MP3 player is raised in your pocket, which is a tight enclosed space, and as such the wires moved down. with the next step the opposite happens, so the more you walk, the more tangled the wires become.

that's my guess. there is a method of wrapping the wires to prevent this (so i am told), it is knitting technique called butterflying. paul.fr, Fri, 4th Jan 2008

Could it have something to do with electromagnetism? (and possibly the close proximity of a mobile phone etc). 

Or could it have something to do with the fact that most people wind their wires up, which makes them twisted, and subsequently they try to unwind in your pocket?  Roadies and musicians are taught a special way to wind microphone cables so they don't become twisted and tangled, it might be a similar principle.

ahtnamas83, Sun, 6th Jan 2008

I haven't heard the podcast yet.

I would guess it's a statistical effect - the untangled configuration is just one of many many states, the vast majority of which are tangled. Put it in your pocket, jiggle about, and the odds are near-certain that you'll end up with a tangled state.

On the subject of headphone cables, please don't wrap them tightly around your gadget, and certainly don't cause the cable to kink sharply where it comes out of the plug as that is a sure-fire way to creating "loose connections" and sending the 'phones to an early grave. techmind, Mon, 7th Jan 2008

Just for Kat.




With your right hand make devil horns (third and fourth fingers tucked, second and fifth extended)
Use your thumb to hold the earbuds against your palm
Wrap the cable around your 2nd and 5th fingers using a figure-8. This is really the key part, the cris-crossing prevents it from knotting
When you have 6 to 8 inches of cable left, wrap the remaining cable around the center of the figure-8 a few times
Tuck remaining cable to taste. Sometimes I tuck it through one of the figure-8 loops, sometimes through the center wrapping, sometimes not at all.
Tightness of the wrapping determines how well it holds together, but if you use a loose wrap, you can just pull on the earbuds and the whole thing comes undone without a single knot.

http://lifehacker.com/software/life-hacks/keep-headphone-wires-from-getting-tangled-152499.php

If this is the same technique used by musicians, i wonder if this is where the hand gesture used by teenagers originated? It does look very similar to one of those stupid pointless hand gestures i see them use. paul.fr, Thu, 10th Jan 2008

Leave it to physicist's to actually investigate this daily annoyance.  Dorian Raymer and Douglas Smith discuss the creation of knots in strings in an article entitled "Spontaneous Knotting of an Agitated String" in the October 16th Proceeding of the National Academy of Sciences. http://www.pnas.org/cgi/content/abstract/104/42/16432 has the abstract available.

I actually thought I first heard about this on the Naked Scientist, although the popular press took hold of it too, such as this article in the New York Times http://www.nytimes.com/2007/12/09/magazine/09knotphysics.htm tigerstargazer, Wed, 16th Jan 2008

Surely during use and winding up and out again of the cables would put some twisting into the cable, and as a result would have tensions in said cables and they work themselves out whilst being moved around in the bag, and we see the result.
AlphBravo, Tue, 12th Feb 2008

I have the same trouble with lunge lines. No matter how carefully I wind them, they always end up knotted. DoctorBeaver, Tue, 12th Feb 2008

Just nature's way of irritating us all. johnnyfr, Tue, 11th Mar 2008

I have a Newton's cradle which I have to transport around on school visits. It drove me mad because I would have to spend 10 minutes of setting up time untangling the thing. Then I discovered that if I fastened a scout waddle on one side it never tangles. I think you should tie up your cables tightly so that they are not lose and able to tangle. Make it Lady, Tue, 11th Mar 2008

I wonder why they don't make small audio cables with a 'lay' like they make ropes. With ropes, you can  hank many metres  by 'dropping'  it, clockwise, over your left hand with your right hand; no twisting force is needed and it uncoils so easily.
paul f''s method works a treat but your fingers can only hold so much and it doesn't work for long lengths. A BBC wireman taught me to coil them, effectively, in a figure of eight - taking alternate loops in different directions in the left hand  (straightforward to demonstrate but hard to describe in words). The coil it produces looks the same as the unidirectional coil but it drops apart with no tangling at all because there is no overall twist in it. lyner, Thu, 13th Mar 2008

"Just nature's way of irritating us all."
Yep, it's called entropy.
http://en.wikipedia.org/wiki/Entropy
Bored chemist, Fri, 14th Mar 2008




that is the ASL sign for 'I love you' JnA, Wed, 27th Aug 2008

The twisted wire knot-look and quick pull release makes this a nice trick for a six year olds birthday party and even if it's not perfect solution for entanglement, it is pretty neat!  Phillip1@rogers, Sun, 19th Jun 2011

I realize this is a little old.  But, thanks to Phillip, it has been brought back to the top.

I don't use an ipod.  Perhaps blue-tooth will make the wires obsolete sometime.

If you take something like a factory roll of Romax electrical wire (flat).
If you unroll the roll, then it will come out flat.
If you pull the roll off the side, without unwinding the roll, then it will introduce a twist into the wire. 

I wonder if that propensity to introduce a twist is part of what causes some of the tangles.  The other thing is the introduce the ability for loops to overlap in a coil (which is one of the advantages of the figure 8 spooling above).

One of the most amazing things is a boating "throw rope".  Essentially you stuff a 50 to 100 foot rope into a little bag, then you toss the bag, and the rope deploys back out...  100% of the time, no tangles, and it must do so as a tangle could mean death for your swimmer.

http://shanesliquidlogic.blogspot.com/2009_12_01_archive.html


The trick with the throw bag is that it is not as much coiled as it is stuffed from bottom to top, again somewhat with overlapping loops just like the figure-8 above.  The article linked actually talks about a new design of a bag.  I guess after using the "classic" throw bags, I'd be reluctant to try something new without a lot of practice.

Anyway, doing a simple coil around your fingers is probably the worst thing to do with ipod wires. CliffordK, Sun, 19th Jun 2011

With due respect to the mathematicians, who are much smarter than I, I think something else might be going on, besides randomness, and ambient movement, shaking, etc. Particularly with two examples: Those very thin, flexible ear bud leads, and, that great mystery, the 'coil-cable' standard-style telephone handset cables - they don't 'tangle' as such, but become inexplicably wound, twisted - requiring disconnecting and turning many times to untwist. What repeated phone-user behaviors could possibly create all these twists? My theory: The cables are pre-energized,so to speak, because of systematic twists - potential energy - already in the multiple conductors within them, created in the manufacturing process. Perhaps in the boating throw-rope example given, there's little tangling because the the rope is made in a way that doesn't introduce preloaded tensions. Just a guess. Bob Bob Trent, Tue, 8th May 2012

Some of the problem is probably to do with twists, but less when they are made and moe how they are used, coiling puts twist into a cable, but rolling doesn't, so if you roll and then uncoil, or coil and then unroll you will change the number of twists. daveshorts, Tue, 8th May 2012

Thank you Paul.fr? You gave me and all a solution that works great!

Though simple enough, I finally figured out why wires tangle - when just looped in a circle, the loops intermix under/over each other, producing a knot, hence the elegant and simple solution of the figure 8! BJ in San Jose, Tue, 17th Jul 2012

Here's a little trivia for you: The human tendency is to try to create order out of chaos. As an example, after you've used an ear bud (earphone) you will generally wrap the cord around and around your fingers before you put it in your pocket. When you pull it out, you will notice that it has tangled and is generally a mess and a lot of trouble to straighten out again. You will actually have less problems if you just bunch it up and then pocket the cord. Go ahead, prove it to yourself next time. Proving it mathematically is a whole 'nother problem **smile** Tom, Mon, 28th Jan 2013

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