I'm Steve Strogatz and this is the joy of why.

A podcast from Quantum Magazine that takes you into some of the biggest unanswered questions in science and math today.

In this episode we're going to be talking about knots.

We all know what knots are, right? They're like the kind of knots that you tie in your

shoelaces or the kind that you use to secure your luggage to the top of your car. If you take

a string, which has two free ends and tie a knot in it, that kind of a knot can come undone.

Sometimes the free ends will slip loose and the knot will just unravel.

But if you fuse the ends together, sort of glue them together, then the knot will be locked in there,

trapped in the loop. Then the question becomes, can you somehow remove that knot in the loop

without cutting the string by just cleverly manipulating the loop somehow or wiggling it.

Well, if you can, that's not much of a knot at all.

That's just a circle, something equivalent to a simple loop,

or what mathematicians dismiss as the trivial knot.

But if you can't undo it, well then that raises all sorts of questions, like how far can you simplify a tangled loop?

How do mathematicians distinguish different types of knots?

How many different kinds of knots are there?

And why do mathematicians and scientists care about knots anyway?

Turns out there's lots of real-world applications for this

branch of math, now called knot theory. It started out with the mystery of the chemical elements

about 150 years ago, which were at the time thought to be different kinds of knots tied in

the ether. Nowadays, knot theory is helping us understand how enzymes can disentangle strands

of linked DNA. And also, Nott theory has potential in basic research to create new kinds of

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