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For Steve Strogetz, a mathematician who we sometimes have on the show, it all started with a pendulum.

He was sitting in math class. Our teacher handed us a little toy pendulum. Basically just a little device with a ball on the end of a string.

That was retractable. That is, you could change the length of the string. Like an old telescope,

you know, that the pirate stretches out of spyglass, click, click, click,

you could make it longer in discrete clicks.

And then the teacher gave us a stopwatch and said, I want you to time how long it takes

for this pendulum to swing back and forth ten times.

Okay, so I do the experiment.

Ten swings.

I record how many seconds it took. Then he says, now make the pendulum

a little bit longer. One click longer. Click. Do it again. And as you might expect, since now

the string is longer, takes a bit more time. To make the ten swings. And I write down the number.

Click, do it again. Click, do it again.

And I do this five or six times dutifully plotting the results on graph paper, which is what the

experiment was really supposed to teach us how to use graph paper. So he's clicking, measuring,

making a little dot. Click, measure, dot.

Click, measure, dot.

Soon the thing is filled with dots, and that is when he noticed something.

This spooky thing was happening, which is that the dots were falling on an arc, on a curve.

They weren't on a straight line, they fell on a particular curve, and I noticed that this curve was a

curve I had seen before because I had just learned about it in algebra class, and it's

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