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Biotech

How and Why Knots Spontaneously Form 145

Posted by CmdrTaco from the knot-a-good-story dept.
palegray.net writes "Scientists believe they have found the underlying reasons why knots are so common in the universe. This research helps us understand how knotty arrangements in various molecules lead to biological patterns, as in certain proteins. The article also provides a look at the field of topology, and how it relates to knots."
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How and Why Knots Spontaneously Form More

How and Why Knots Spontaneously Form

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  • Hair (Score:5, Funny)

    by Verteiron ( 224042 ) on Sunday December 30, 2007 @11:13AM (#21856914) Homepage
    But can they explain why knots form in your hair after laying still for as little as an hour? My wife blames gnomes, and I'm inclined to agree with her.

    • Re:Hair (Score:5, Funny)

      by nuclearpenguins ( 907128 ) on Sunday December 30, 2007 @11:21AM (#21856970)
      Gnomes? I'm afraid knot.

    • Re:Hair (Score:5, Funny)

      by Anonymous Coward on Sunday December 30, 2007 @11:21AM (#21856972)
      It can't be gnomes, it has to be KDEs.

    • Re:Hair (Score:5, Funny)

      by dbolger ( 161340 ) on Sunday December 30, 2007 @11:23AM (#21856986) Homepage
      A more relevant example would be how you can set up a PC for the first time, and have all the cables carefully arranged so that there is no crossing over or tangling, and yet when you come back six months later, to add a new device or to swap out a cable, every single one of them is wrapped tightly around the others to such an extent that you can't understand how it could come about without somebody doing it intentionally.

      • Re:Hair (Score:5, Funny)

        by SetupWeasel ( 54062 ) on Sunday December 30, 2007 @11:59AM (#21857246) Homepage
        I like how a post about a woman's hair gets no moderation, but a reply about computer wires with exactly the same point gets +5.

        Since this is Slashdot, all must be right with the universe.

        • Re: (Score:1, Funny)

          by ScrewMaster ( 602015 )
          Because the computer reference has relevance to the Slashdot crowd (I mean, they've actually seen this phenomenon happen with cables) but a woman's hair? How often does a basement dweller get close enough to a woman to notice that her hair is tangled or not?

          • Re: (Score:3, Insightful)

            by orasio ( 188021 )

            Because the computer reference has relevance to the Slashdot crowd (I mean, they've actually seen this phenomenon happen with cables) but a woman's hair? How often does a basement dweller get close enough to a woman to notice that her hair is tangled or not?

            Ten years have passed. We finally moved out of our parents basement. We grew old. People who are young now are no longer the nerds we were back in the day. Add to that the fact that nerds are much more attractive for the ladies right now, and you will see that most of us have seen a girl from up close, and even touched them with their consent.

            It was a nice joke, to say that slashdot people were virgins, but sadly that joke died. Learn to live with it. there are a lot of nerds still here, but B.O. and probl

            • Re: (Score:2, Offtopic)

              by Afrosheen ( 42464 )
              "but B.O. and problems with girls does not define us anymore"

              Actually we're bordering on Old Man Smell now and the problems with girls we have are along the lines of "my wife isn't giving me any" and "my daughter is about to reach puberty, hand me the xanax".
        • When I parsed the mentioned comment, it stated "undeclared-your" hair was the subject of the knotting. The Wife's spurious attribution of the cause to small semi-sentient beings does not change the knots in your hair.

          Meanwhile, when is the last time you swapped your hair strands around with the purpose of installing new hardware?

          • Re: (Score:3, Funny)

            by SetupWeasel ( 54062 )
            I've never personally purchased a weave, but I hear many women do.

          • Meanwhile, when is the last time you swapped your hair strands around with the purpose of installing new hardware?
            The last time I jacked into the Matrix, you insensitive clod!

            Oh, dear. I've said too much.
        • My wife is bald, you insensitive clod!
        • What would a bunch of bald guys know about women's hair?

        • Re: (Score:2)

          by Lavene ( 1025400 )

          I like how a post about a woman's hair gets no moderation, but a reply about computer wires with exactly the same point gets +5.

          Since this is Slashdot, all must be right with the universe.

          Wow! I AM a woman... with long hair, and I have modpoints. And it didn't occour to me to mod the post about hair but I wanted to mod the one about wires! (It was already at +5 though, which is good really since I'm kinda blond too and constantly mod first and post later throwing my points down the drain...)

      • Re: (Score:1)

        by Deaddy ( 1090107 )
        I bet it's this strange quantum physics thing and it only does happen if you don't observe it.
        At least you'll see how it happens, perhaps because of the inner torsion of the cables or someone just unplugged a cable because he wanted to test something. Maybe one should put Folding@Home to good use.

      • Hands-on knot theory (Score:5, Insightful)

        by clawsoon ( 748629 ) on Sunday December 30, 2007 @01:10PM (#21857838)
        As a sysadmin who has spent days untangling hundreds of tangled cables from the backs of too-crowded racks - hundreds of A/V lines criss-crossed by dozens of network lines criss-crossed by power cords - I've had some time to think about practical knot theory. I've established two primary hypotheses:

        1. Placing cables is difficult because you are not just defining the position of that cable, you are also defining the position of every other cable in relation to that cable. As the number of cables rises, the complexity increases combinatorially. (Or exponentially. Or something. I faked my way through those math classes.)

        2. There are many more ways for cables to be tangled than to be untangled, so statistically, tangling is overwhelmingly likely. It's like entropy that way: There are many more ways for particles to move in different directions than there are ways for particles to move in the same direction, so it takes special effort or special circumstances to get them all to line up.

        • Re: (Score:3, Interesting)

          by poopdeville ( 841677 )
          2. There are many more ways for cables to be tangled than to be untangled, so statistically, tangling is overwhelmingly likely. It's like entropy that way: There are many more ways for particles to move in different directions than there are ways for particles to move in the same direction, so it takes special effort or special circumstances to get them all to line up.

          You need to make the notion of counting ways to be tangled and untangled more precise. In any case, the problem with real cables is that mos

    • Re: (Score:2, Interesting)

      by captain_dope_pants ( 842414 )
      I used to be a fisherman for a living. Miles and miles of nets, rope etc. When the "knot gnomes" had their way with that lot it was a nightmare!
      There are also undersea variants of the "gnot knome". You go to haul your nets after a couple of days and they're gnotted all to hell.

    • Re: (Score:1, Funny)

      by Zeros ( 1016135 )
      Or why is it that even when i organize my cables on the back of the computer they will become a huge knot, i think bush just comes every night and tangles them.

    • Re: (Score:1, Funny)

      by Anonymous Coward
      If your wife lies still while laying, you have other problems than knotted hair.

    • Re: (Score:2)

      by Zak3056 ( 69287 )

      But can they explain why knots form in your hair after laying still for as little as an hour? My wife blames gnomes, and I'm inclined to agree with her.

      Well, duh! It actually has a really simple explanation. The gnomes have a business plan, which goes:

      1. Tie hair into knots.
      2. ???
      3. Profit!

    • Re: (Score:2)

      by GWBasic ( 900357 )

      But can they explain why knots form in your hair after laying still for as little as an hour? My wife blames gnomes, and I'm inclined to agree with her.

      It's because you need a hair cut, damn hippie! (joke)

    • On behalf of my fellow gnomes that's Gnot even funny.
  • I thought this might be about the jungle under my desk.
  • and I thought it was just me...

    TFA revealed some interesting physics.

  • Slashdotted article text (Score:2, Informative)

    by Anonymous Coward
    http://www.sciencenews.org.nyud.net:8090/articles/20071222/bob11.asp [nyud.net]

    Tied Up in Knots
    Anything that can tangle up, will, including DNA

    Davide Castelvecchi

    Knotted threads secure buttons to shirts. Knots in ropes attach boats to piers. You can find knots in shoestrings, ties, ribbons, and bows. But even without Boy Scouts or sailors, knots would be everywhere.

    Call it Murphy's Law of knots: If something can get tangled up, it will. "Anything that's long and flexible seems to somehow end up knotted," says Andrew B

  • All knotted up for next year. (Score:5, Funny)

    by theleoandtherat ( 1115757 ) on Sunday December 30, 2007 @11:29AM (#21857042)
    Any tip about packing christmas lights?

    • Wrap them (Score:5, Informative)

      by Chmcginn ( 201645 ) * on Sunday December 30, 2007 @11:47AM (#21857162) Journal
      Get a long sheet (about 50 cm x 2-5 meters, depending on the number of lights.) Starting at one end, wrap it around the short end of the rectangle, then fold it over about 10 cm. Repeat until all your lights are in a big cigar tube.

    • Re: (Score:1, Informative)

      by Anonymous Coward
      Real Simple has a great list [tinyurl.com] of holiday organization tips, including this one which tackles the problem of Christmas lights.

    • Re:All knotted up for next year. (Score:4, Informative)

      by SimonTheSoundMan ( 1012395 ) on Sunday December 30, 2007 @12:11PM (#21857374)
      Google 'reverse coil' or 'overhand coil'. Wires tangle because people do not know how to coil them up correctly.

      • Re: (Score:2)

        by Phroggy ( 441 )
        Those didn't help at all. Do you have a more specific link?
      • But the wires aren't moving! How can they tangle up if they're not moving?? How can a box of Christmas lights left for a year in a closet get more tangled up than they were when placed in the closet?

        Someone should make a time sequence film of Christmas wire tying itself in knots.

      • Google 'reverse coil' or 'overhand coil'. Wires tangle because people do not know how to coil them up correctly.

        Oddly enough, as of 3:16pm EST, googling for 'overhand coil' -- the second search result on google is this thread.

        Sadly, I think now simply mentioning an uncommon term on Slashdot is enough to completely skew search results since Slashdot rates so damned high.

        Too odd. :-P

        Cheers
      • How odd. The google result for "overhand coil [google.co.uk]" lists your post at #2 mere hours after you posted it. The overhand coil must not be a popular method.

        -Grey [silverclipboard.com]

      • Re: (Score:2)

        by fbjon ( 692006 )
        I don't know if this is common, but I have a different method for shorter cables:

        Simply double the cable, putting the two ends together. Then double over again, putting the two ends and the midpoint of the cable together on one side. Continue doubling until the bundle has a nice length/thickness ratio. At this point, squeeze it all together in the middle and make a simple knot with the ends (one end over the other, twist around it).

        You need "access" to the entire length of the cable, so it doesn't work a

        • Re: (Score:3, Interesting)

          by hazem ( 472289 )
          I worked for a summer with a flooring contractor before going to basic training in the army. They did a cool technique with their extension cords where they basically made a long loose crochet chain out of them. A 50 ft cord would end up about 10 feet long and then they'd toss them all in their big "contractor box".

          For some reason, cords that were already looped up like this didn't tend to knot up with each other. Which makes me wonder if there is a maximum knotty potential... straight un-knotted cords h
    • I have found that if you roll each strand up, and place each strand in a separate plastic grocery bag (the type that they bag your food in at the store), then place the bagged strands into a box, they do not tangle. Makes it much easier on yourself the next year.

      • Re: (Score:2)

        by hazem ( 472289 )
        For my Christmas lights, I Just use a piece of cardboard - like the side cut out of a box, put a notch near one corner. I stick the end of the cord into that notch to hold it in place, then I just wrap the lights around the cardboard with the wires close like I were winding a coil. At the other end, I make another notch to hold the other end of the lights.

        I usually make the piece of cardboard smaller than the lights' original box so I can just slide the whole bunch back into that box.

    • Re: (Score:3, Informative)

      by gbutler69 ( 910166 )
      I've found that rolling them up in a ball, like one would yarn, works absolutely perfectly. It never tangles. It's compact. It's easy. It seems a little counter-intuitive, but, if you think about it, why do women who knit or crotchet wrap their yarn in balls? Because it works!

    • Re: (Score:1)

      by rubah ( 1197475 )
      we use sheets of cardboard 8)

    • Re: (Score:3, Informative)

      by pwnies ( 1034518 ) *
      I think what SimonTheSoundMan was trying to get at was something called "Over/under cable wrapping". It's a method of wrapping cables used mostly by sound guys that eliminates spin in the wires (which from my personal experience is the #1 reason why cables get all tangled about). You can check out the wikipedia article on it (albeit short) here: http://en.wikipedia.org/wiki/Over/under_cable_coiling [wikipedia.org] , and a great tutorial for it here: http://www.techno-fandom.org/~hobbit/flipcoil/howto.html [techno-fandom.org] .
      In regards to C

  • Do we really need an answer? (Score:5, Funny)

    by pla ( 258480 ) on Sunday December 30, 2007 @11:39AM (#21857096) Journal
    This research helps us understand how knotty arrangements in various molecules lead to biological patterns, as in certain proteins.

    Because He reached out his noodly appendage and put the spark of life in our universe.


    "And the earth was without form, and void; and straightness was upon the face of the pan. And His Noodly Appendage moved upon the face of the sauce.

    And FSM said, Let there be knots: and there were knots.

    And FSM saw the knots, that they were good: and FSM divided the knots from the straightness as happens when you boil short and long pasta at the same time.

    And FSM called the knots Spaghetti, and the straightness he called Ziti. And the strands and tubes were the first course."


    Duh?
    • Great and Manifold are the Blessings of his Holy Pastaness but I don't recall the simplest overhand knot in hundreds of pots of spaghetti that I have cooked. Perhaps I should reevaluate my faith and say some Hail Marinaras .

  • Yes, but what about shoe laces, huh? (Score:5, Funny)

    by Prototerm ( 762512 ) on Sunday December 30, 2007 @11:47AM (#21857164)
    That explains why knots spontaneously form in wires and cables when you stick them in a box, but what about the way knots spontaneously come undone in your shoe laces? Perhaps in an alternate universe, shoe laces spontaneously knot themselves, and wires and cables untangle in storage. Of course, with that sort of altered physics, Homer Simpson would probably be the President of the United States.

    Oh, wait.

    • Re: (Score:3, Informative)

      by Jugalator ( 259273 )

      but what about the way knots spontaneously come undone in your shoe laces?
      That's often because they're in that case an unbalanced granny knot [kovaya.com]. :-)

    • Re:Yes, but what about shoe laces, huh? (Score:4, Interesting)

      by Tony Hoyle ( 11698 ) <tmh@nodomain.org> on Sunday December 30, 2007 @12:06PM (#21857320) Homepage
      What gets me is how knots form when both ends of the cable are plugged into something. And they form in such a way that there's no way to untangle it without unplugging everything and painstakingly unpicking it from the mess.
      • The answer to that is in String Theory. You see, in 11-dimensional space-time, the entire universe folds over itself, leaving the seemingly paradoxical knots you mention as the only trace.

        - RG>

    • Re:Yes, but what about shoe laces, huh? (Score:4, Informative)

      by Anonymous Coward on Sunday December 30, 2007 @12:17PM (#21857408)
      Shoelaces come undone due to the type of knot being used. There is an entire site http://www.shoeknots.com/ [shoeknots.com] devoted to this, and another site http://shoelaceknot.com/shoelace/index.htm [shoelaceknot.com] with exhaustive details on shoelaces in general.

      [disclaimer: I maintain one of the sites]
    • Why are you still wearing shoes with laces? Technology has progressed beyond the need for such archaic devices.
      • Because velcro looks silly.
        • Velcro looks Silly, Laces look silly. Why have either?
          • What else? Magnets? Actually, that would be so bad... just as long as you don't keep your computers at floor level.
            • My shoes have neither. There are plenty that don't. Most women's flats and formal wear. Men's formal wear (loafers, etc). Mine are lace/velcroless shoes from Merrell which have an opening at the top surrounded by stretchy padded fabric (it's not elastic, but I don't know a better way to describe it). They fit snugly (but not too tightly to be uncomfortable) around my ankle, and they stay firmly in place.

    • That explains why knots spontaneously form in wires and cables when you stick them in a box, but what about the way knots spontaneously come undone in your shoe laces?

      I tie my shoes with wires and cables. The only problem is when I want to take them off...
    • I used to have this problem for years, until I learned a simple trick: tie the knot backwards (left-over-right instead of right-over-left or vice-versa). When the string in the knot and the bow run parallel to each other, the increased friction holds the bow together.
  • !knotcometonaught = notknotcometonaught?

  • Fishing line (Score:4, Funny)

    by Eudial ( 590661 ) on Sunday December 30, 2007 @12:10PM (#21857358)
    Fishing line is epic.

    It can be straight, but the moment it comes into contact with anything, or disappears outside of the line of view, or for no apparent reason at all, it's a virtual loom of spontaneous knots.
    • That's because applying a forgetful functor to an epic results in multiple morphisms in the preimage connecting the ends of the arrow, hence loops in the graph.
    • True story.. I remember one time as a yougin' off to Grandma's house, I had my fishing pole with me. Now, for some silly reason I had a bunch of fishing line running through all of the loops going up the pole, instead of reeled in and simply tied off at the end like it should have been. I must have had twenty or thirty strands of line looped between the eyelets on the pole. I leaned the pole up against the screen door and walked away for a moment, and when I came back, I went to grab the pole and open the
  • Despite being pretty much a Macfan boy I have one MAJOR irk with Apple -- the stuff they make all their cable out of. It has to be the most knottable substance known to mankind.

    Every single time I pick up the earphones from my iPod they are knotted. I am very careful to wrap them in a way I think they will stay unknotted, but every time, every time, they are knotted again.

    Drives me nuts.
    • I have a set of headphones with a tiny cloth storage bag...I had the same trouble, but eventually I figured out that not wrapping them at all, but rather stuffing the cables into the bag, solved it.

  • Spongebob: Doesn't anybody know how to tie a knot? (lightning appears as well as the Flying Dutchman)

    Flying Dutchman: Did somebody say knot?

    Spongebob: (eyes grow large) I did.

    Flying Dutchman: So, you wanna tie knots, do ya? Well, do ya?

    Spongebob: Yes, please, Mr Flying Dutchman, sir.

    Flying Dutchman: Then you've come to the right flying ghost, kid. You're looking at the first place winner in the fancy knottin' contest for the last 3,000 years!

    Spongebob: Hooray! (floats up into the air and into a heart)

    Flying Dutchman: (grabs Spongebob) You're gonna have to not do that. And stop staring at me with them big old eyes! (Spongebob's eyes shrink) Now, stand back and watch me be knotty. (laughs and pulls out a rope) Haha! Behold! (rope is in pretzel shape) The pretzel knot!

    Spongebob: Ohh. (Flying Dutchman makes the rope into 2 diamonds)

    Flying Dutchman: The double-diamond knot! (holds the rope, now in the shape of a square, in front of Spongebob) The square knot! (rope slithers over and squeezes Spongebob) The constrictor. (Grabs Spongebob and pulls him apart revealing a knot that looks like intestines) The gut knot! (Flying Dutchman makes a knot in the shape of a pillow) The pillow knot. (turns the knot over where Spongebob is sleeping. Then he makes the knot into a butterfly) The butterfly knot.

    Spongebob: Ohh...

    Flying Dutchman: Wait! There's more. (Spongebob takes out a pen and paper and his glasses) The monkey chain! (shows the rope as a chain) The monkey's fist! (shows the rope into a ball) The monkey! (shows the rope as a monkey)

    Monkey: Ohh, ohh!

    Flying Dutchman: This one here's a loop knot, otherwise known as the 'poop loop'. (pulls the rope)

    Rope: Poooop!

    Spongebob: (laughs) Those are great, Mr Flying Dutchman, sir! Now can you show me how to tie my shoes?

    Flying Dutchman: (laughs) I don't know how to tie me shoes. I haven't worn shoes for over 5,000 years! (holds a sock with two blue stripes up) But sometimes I like to wear this little sock over me ghostly tail. (laughs as he flies off. Scene cuts to Spongebob crawling into his pineapple)

    No need to RTFA, I bet the Flying Duchman would know...we should ask him!!

  • Loose ends cause most of the trouble... (Score:5, Interesting)

    by jddj ( 1085169 ) on Sunday December 30, 2007 @12:37PM (#21857590) Journal

    As a kayaker, I'm familiar with a rescue tool called a throw bag [riversafe.org.nz]. Apparently, throw bags were developed for the maritime industry, then downsized for kayakers.

    The theory is quite simple, but it's amazing to watch how well it works:

    • Tie a rope through a hole in the bottom of a bag.
    • Stuff the bag with the rope, leaving the tail end of the rope sticking out of the top.
    • Grab the tail end of the rope and throw the bag towards the person who needs the rope.
    • Watch as the rope magically pays out of the bag, completely free of knots or tangles.
    • Don't get so awed by the rope coming out untangled that you let go of the end...

    I've watched these bags work time and time again, amazed that with the rope just stuffed into the bag, they work reliably. I've used store-bought bags and ones I've made myself and have never seen the rope tangle.

    I realize that without loose ends proper knots can't form, but with a throw bag, you don't even get close to tangles!

    • thats an interesting point,

        wonder if anyone does this for computer cables I guess you could get a similar effect with a sheet of paper and a couple of elastic bands create a paper tube poke in the wire seal it with 2 elastic bands or a couple of paper clips

      yes it seems to work
    • Like someone else mentioned, how do computer cables still seem to knot when BOTH ends are plugged into something?

      I'm looking down at my headphone cord right now and its knotted and tangled around a microphone cord, and a couple of data/power cables. Everything is plugged in at both ends and the cables almost never get moved around. But that won't stop them from tangling!
      • I think that has to do with torsion(twisted pairs of wires unwinding?) and the multi-material composition of wires as opposed to ropes made of a single woven material(I've never seen braids twist, just loosen).
    • Neat. We used the same idea for rappelling out of choppers - just drop the bag, attach your carabiner, and off you go.

    • Re: (Score:2)

      by khallow ( 566160 )
      Here's my more or less educated guess on what's happening. If the rope had been free, then it would tangle in short order. But the bag constrains the rope in two ways. First, some knots would occupy more space so it requires more energy than before to reach those configurations because you need to stretch the bag to some extent in order to accomodate the knot. Second, the bag limits how much kinetic energy is in the system to go into knot forming. My take is that you will still see knot formation in a bag o

    • Re: (Score:2)

      by martinX ( 672498 )
      Good link. Thanks.

      I like the advice: Make sure there are no sharp and hard objects in the bag.

  • The photo of the DNA in the article does not appear knotted to me. Does anyone have a link to a DNA image that is truly knotted?
    • If you go clockwise from the top the thread goes over a thread, then under, over, under, over and under to get back to its starting point.
      Once you agree with that, I think the string can't be twisted to become an simple loop.

      There is an interesting feat of DNA more or less counter to the example given: how a chromosome manages to unfold into a string with length of the order of centimeters during cell division without getting completely entangled.

    • Re: (Score:2)

      by g-san ( 93038 )
      @

      How's that? Happy New Year.

  • Knot-unknot asymmetry (Score:5, Insightful)

    by SpinyNorman ( 33776 ) on Sunday December 30, 2007 @01:02PM (#21857772)
    Surely the fundamental reason why knots form (or rather why they persist/accumulate)is because of the inherent assymmetry of them formign/unforming.

    A loose end in a jumble of coils, if jiggled around, is almost bound at some point to pass though a coil and form a potential knot, but a knot once formed is by no means destined to become unknotted, especially once additional knots form on the loose end thereby securing earlier knots.

    If the chance of becoming knotted is less than the chance of becoming unknotted, then there's going to be a trend towards becoming increasingly knotted (to some limit where the accumulated knots limit mobility of the mass).

    It seems there may also be a ratcheting effect once a loose knot forms - the knot/loop being bulky will more likely catch on the surrounding mass then the single stands leading into it, so that if the loose ends get tugged by the jiggling of the surrounding mass then the knot will tighten.

    But there again I'm just a dude who uses string rather than a high powered topologist getting paid to research string, so what do I know?!

  • So this is where string theory leads us? (Score:4, Funny)

    by rickb928 ( 945187 ) on Sunday December 30, 2007 @01:04PM (#21857796) Homepage Journal
    How hard is this? The Universe is a box full of string. Knots form. Some make pretty big knots.

    Eventually, when the chimps write a decent but unpopular novel, balls of string form. Many balls. In time, these seem to have gathered and caused all sorts of interesting phenomenae, like stars, Western clothing, and Jessica Alba.

    Unfortunately, this can only end one of two ways...

    1- The string gets untangled. All devolves into a box of string again. Knots form again.

    2- All this gets emptied into another box. Sold at a yard sale. Who knows what happens with the new owner... Actually, even if the string gets untangled, it ends up in a yard sale.

    Physics. It's really all about yard sales.

  • Does this also explain why shoelaces tie themselves into knots while I'm sleeping? I have long suspected my cat, but I guess science has a better explanation...
  • I read along time ago baton a whatknot. It's supposed to be what flat "ropes" like seatbelts become. Anybody know what I am talking about?

  • A string walks into a bar. (Score:3, Funny)

    by Fjord ( 99230 ) on Sunday December 30, 2007 @06:55PM (#21860398) Homepage Journal
    A string walks into a bar.

    He asks for a shot of tequila. The bartender replies "Sorry we don't serve strings". So the string leaves.

    The next day, the same string walks back into the bar. He asks for a shot of tequila. The bartender replies "Sorry we do not serve strings, please go away."

    The following day the string stands outside the bar debating about whether to go in or not. He ties himself up and messes the top of end so that it's loose and uneven.

    He goes in and asks for a shot of tequila. The bartender replys "Hey aren't you that string that's been coming in here all the time."

    The string replies "No I'm a freyed knot".
  • Persistent length is a characteristic of a linear object (polymer molecule, for example) which characterizes bendability of this object.

    I have thick USB cable to my Belkin wireless adapter and thin one to the mobile mouse. The first one never tangles, the second one tangles all the time. Belkin cable is twice longer than mobile mouse one. The difference is a persistent length.

  • Keeping DNA tidy may be crucial to some of the cell's most important functions. That's because copying DNA and reading out the information it contains are performed by other enzymes, called polymerases, which walk along DNA. "When [a polymerase] comes to a knotted area, it will be stuck," Belmonte says.

    It's known that ageing is due in part because of the accumulating errors in copying DNA. This article leaves one speculating whether this knotting could be one major source of those copy errors?

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