Placeholder Image

Subtitles section Play video

  • Alright, we're gonna do some street maths

  • here in the outdoors,

  • which I've heard a lot about.

  • But first...

  • my shoe is untied.

  • So we need to fix that.

  • Now, most people would mess around doing some kind of complicated knot,

  • not me - I'm a mathematician.

  • I've got maths to do.

  • Grab the two sides, pass 'em over, boom! There's your knot.

  • Again, in slo-mo!

  • I'd heard about it, you know, on the maths circuit.

  • People would discuss the way that you tie your shoes, right?

  • And so – I know it's been around for a long time, I know it's been passed down

  • from mathematician to mathematician.

  • But I'm not familiar with the earliest case, and I have heard names assigned to it,

  • but I've not come across any one that particularly sticks.

  • I just call it "that brilliant way to tie your shoes."

  • (Brady) Be honest with me, is that how you do your shoes?

  • I do genuinely tie my shoes that way

  • I know I'm always talking about it

  • I literally tie my shoes that way.

  • Up to once a day.

  • Once it's done, it looks exactly the same, right?

  • So then people won't go, "That's an unusual knot," right?

  • But if they actually see it happening

  • It's like they've seen a magic trick, right?

  • It just blows their mind

  • They can't comprehend how a knot can happen so quickly.

  • But, I'm not startled; I'm a mathematician!

  • I know what I'm doing.

  • Okay, you go from completely undone, it starts the same way as a normal knot

  • You do your little foundation thing

  • Which in maths is called a trefoil

  • It has a minimum of three crossings in that particular knot

  • Now to tie the actual bow

  • You get one shoelace that's coming out the back

  • You fold it forward and you hold it on its way down

  • So it goes up over the loop and then down

  • This one curls back in the opposite direction

  • And again you hold it on the way down.

  • And then all you do is you take this one on the way down and put it under that loop

  • At the same time as taking this one and putting it under that loop

  • And then you swap them over to the other hands

  • And then you pull them tight, and that is your knot!

  • And with a little bit of practice,

  • Once you tighten it, hold them on the way down,

  • cross, pull, knot.

  • So the one that comes out the back, you fold it forward into a loop

  • And then you hold it on the way down

  • So it goes up and then on the way down you're grasping it

  • Same with this one except it goes back

  • So it starts at the front, curls back, hold it on the way down

  • Now you're gonna take this lace, put it under that loop

  • at the same time as taking this lace and putting it under that loop

  • So they go past each other

  • They swap hands, you pull it tight

  • And there's your knot.

  • People tie their shoelaces, they get one and they loop the other one around

  • and they pull it through, which is the normal way.

  • Although I've noticed, of course, Brady wears slip-ons.

  • (Brady) Why? What's wrong with them?

  • For those of us who have entered adulthood

  • We do it a long, complicated way.

  • But, the thing is, you end up with a knot that holds your shoe on.

  • That's the goal here

  • My shoelaces

  • Formed with what ordinary people would think is a knot

  • Now, nothing of this is a mathematical knot

  • Because it has loose ends

  • If it has loose ends, you can, in principle, untie it

  • And you can form a different knot.

Alright, we're gonna do some street maths

Subtitles and vocabulary

Operation of videos Adjust the video here to display the subtitles

B1 tie loop mathematician brady lace pull

Super-fast way to tie Shoelaces - Numberphile

  • 0 0
    林宜悉 posted on 2020/03/30
Video vocabulary