We'll just look at two of the most dramatic pictures.
One of which is of a jumbo jet at night taken by what light was available at the airport.
The next slide shows a picture taken from exactly the same
view, position but taken by this camera,
which is recording not the light, but the heat being radiated
by the different things that it can see.
And you can see that the aircraft itself is slightly warm
with respect to the background, at least most of it is,
its tail plane here isn't you see, but there you can see.
And you can see the detail, you can see which airline it belongs to.
And these improvements which have taken place in the last two or three years
really have changed this situation out of recognition,
and we can now actually with this camera, which is here,
have a look and see what it can see.
And if someone will come and operate the camera
It's visual presentation is here
but it's entirely compatible with the BBC television.
And the signals can be fed straight in
and so we'll be able to see them on the monitor.
And now you see we've got no light, pretty well, in the lecture room.
And there you are, all radiating.
Your faces... would you like to hold your hands up?
And you see at once there are your hands showing up, or wave them about.
Even separate fingers are being seen, you see. Like that.
And so you can see for example if you're guarding a site
where you might have intruders,
this will give you a very good picture in complete darkness.
Purely by the heat radiation coming off the, even just one's face like that.
There are various things it may do, if I can find...
Oh, here's a sponge, I'll go out in front for the moment.
And one can, you see, because water evaporating loses its fastest molecules
like that, a wet surface is always slightly cooler than the surface, than the body,
than the things around it.
And there you can see immediately that the sponge is really quite cold,
because you see my hand is quite warm but this is blacker than anything,
anything else it can see, just because of the slight lowering in surface temperature
because of the cooling produced by evaporation.
So there is that.
I wonder what happens if we put this in front of it.
Ah, yes, this is beautiful. You see now we see the Royal Institution as black on white.
Now much of that difference is not due to the fact that those
letters are at a different temperature, it may be partly that,
but one of the effects which is very clear here,
is that the black is showing up there,
whereas if we have the visual picture, and I think we can now have the lights up,
you'll see that it in fact is light on dark. And the reason is that,
and it's a very, you probably learnt this rule,
who knows, who'd know the rules that good absorbers make good radiators?
Well you see here is a case in point.
The black is a good absorber, the metal is a good reflector, bad radiator,
and the thermal picture you see shows it quite correctly the other way around,
because the black is radiating more effectively than the white.