Now I would like to show you one more experiment concerned
with waterproof and wetting.
I would like to get some nitrogen
which has been cooled and pushed together.
Alright.
I'm going to pour into this goblet with a protecting vacuum.
Liquid air, namely liquid nitrogen.
You'll see it boiling.
All the time.
And I want a short piece of that if I can.
We'll leave that there and same supply.
I'd like to put this rubber tube in.
Anybody want to try it?
Here is some more.
Take it.
Now by this time it's well frozen.
And so, I will take this out here.
I will give Mr. Coates that in exchange for a good hammer.
And we will see what the rubber tube is like.
Ready?
[Laughter, applause]
Now, don't put your finger in liquid nitrogen.
Unless you do it very, very quickly.
Now here is liquid nitrogen again.
It's a nice white liquid.
I'm going to put my finger in.
Because I don't... because I know what I'm doing.
Don't do this. This is not a thing to imitate.
Is that right, George?
He said yes.
So George is the head of the whole Royal Institution
and he and I confer about what's good for people and not.
Watch that. Look what happens.
Now why did they run along?
Because this thing is liquid nitrogen proof.
For a different reason.
It bubbles away boiling, and coasts like a hover craft on a piece...
on a layer of nitrogen gas.
We'll do that again for you people.
Any more left?
No, no, I want both lots.
We'll pour it along the floor here.
What's the evidence from that?
There are two pieces of evidence. Very interesting.
First, nitrogen molecules attract each other.
If they didn't attract, they couldn't make that liquid.
They couldn't stick together.
Second. Nitrogen molecules repel each other when very close.
Cause if they didn't repel, the liquid would have
collapsed and disappeared like that suddenly.
So we know they attract, and we know when very close they repel.
And that's how we get evidence about things
which are much too small to see.