Transcript:

Let's say you were sitting on a beach many, many, many years ago, and you had a palm tree, and at the top of the palm tree at night, you noticed a star. And you would go to the beach every night, and using the treetop as the reference, you would notice that the position of that star every night has changed a little bit.

And over many, many, many measurements, you would notice that every 360 measurements, the pattern repeats itself. It is because the Earth takes 365 days to make a full circle around the sun. And it's just by dumb luck that your measurements repeat every 360 times.

If the Earth took 800 days to go around the sun or 800 nights, your measurements would repeat every 800 times. And then 360 would not be the angle subtended in the center of the circle.

For example, the French came up with this unit of angle called grad. One hundred grads is one right angle. It just doesn't fit. It doesn't fit anything. Have you heard anybody using the angle grad?

Three hundred sixty works because the Earth takes 365 days around the sun.