Original subtitles

A message to future scientists #10: Thermal expansion

Thermal expansion.

Thermal expansion is the tendency of matter

to increase in volume as its temperature increases.

For example, let's examine this aluminum pipe.

When we heat it with a burner,

it expands and lengthens.

However, the amount of thermal expansion is very small,

and cannot be seen with the naked eye.

Let's add some things in order to confirm that this pipe is getting longer.

We place a hard block under the pipe.

Then insert an L-shaped wire under the pipe.

Finally, we suspend a weight from the end of the pipe

to hold the wire down.

Now, we heat the pipe again

and the wire begins to move.

The pipe's lengthening causes the wire to rotate, lifting the L-shaped arm.

In this way,

a clever contraption magnifies a tiny change in the length of the pipe

and makes it visible.

Let's do another experiment

that dramatically reveals slight thermal expansion.

We heat a spoon thoroughly with a burner.

Then, we put it on a chilled lead ingot.

Take a moment and try to imagine what will happen next.

Ok, let's try it.

It emits a bell-like ringing sound.

When the spoon is removed,

the sound stops.

As the surface of the lead ingot is heated by the spoon,

it expands rapidly.

This quick expansion causes it to hit the spoon.

The continuous impacts at both ends sound like a bell.

Positive proof of slight thermal expansion is revealed by sound.

A message to the scientists of the future,

NIMS.