And these stars have compressed down to maybe something like 12, 15 miles wide, and they are black holes.

It means I can take two identical squares, put them in light and dark surrounds, and the one on the dark surround looks lighter than on the light surround.

Mawhinney's Eyes

Round them up.

We have two identical tiles on the left, one in a dark surround, one in a light surround.

Perhaps the easiest model of a camera is called a pinhole camera.

Environmental viscosity

Let's say I have another circle here.

McGee, David... Perimeter.

You come with me. McGee, take the perimeter.

The pond was encircled with trees.

In an infinite expanse of nothingness...

Tall pine trees make a ring around the lake.

So all we're interested in here is comparing the temperature of the beetle against the background.

Area and Perimeter

Each iceberg has its own individual personality.

Whereas on the right, the two tiles look nearly the same.

This tree measures three meters around.

They are labor intensive and inefficient.

So this right here, this is just a formula for the perimeter of a rectangle.

Anyway, we're done.

So it's equal to 28 centimeters square or squared centimeters.

We'll secure the perimeter.

Clear the area.

There is a fence about the house.

There is a fence around the house.

And of course, the major thing

The tree is four feet around.

The lake is five kilometers round.

The earth goes around the sun.

So let me draw a square here. My best attempt. So this is A, B, C, D. And we're going to tell ourselves that this right here is a square.

If AB is x, then BC is x, then DC is x, and AD is x. All of the sides are congruent. All of these segments are congruent.

No! Right and might are on our side.

Watch your spacing.

But I had to make a little barrier, going around it, out of cellophane, to stop it moving.

The court is partly surrounded by a high wall.

We have to figure out its length as well. So, how do we figure that out?

(Laughter)

I don't know where they've gone.

How do we inspire everyone around us?

And yet, look around us.

The lake is ten miles about.

Remember, a seamount turns into an island when it hits the surface. And what's the context of the Phoenix Islands?

I photographed this thing last week in Dorset.

Bar the gate. And set a watch on the surround.