Doppler echo location is something I've put to use in recent years
for observing bats.
I have a small doppler radar here for measuring bat flight speeds
and it also can observe details of their wing motion and their aerobatics.
And we've learnt quite a lot about the details of bird flight
by pointing it at birds.
My first one proved that it was a useful technique
and then I got some very welcome help from Marconis
who made me this superb little doppler radar.
This is a true microwave radar.
We could try to demonstrate this on the bats if we get one of them to fly.
Here he is.
Let's switch it on first.
Oh, I forgot.
[Low wooshing sound]
Thank you, Bill.
Of course that's at point blank range.
The radar will detect a bat of that size at up to about 30 metres.
And a pigeon out to considerably further away.
We're going to demonstrate it though by looking at a different problem.
You remember Galileo and the leaning tower of Pisa?
Where he dropped balls to see at what rate they would fall.
Well Phil here is going to try and take some pictures
of balls as they fall from the ceiling.
While I measure their speed on the doppler radar.
Phil, I think you better have this protective clothing.
Thank you.
Is that comfortable?
I'll switch on the radar.
And you see the balls up there?
See if we can get one as it comes down.
OK, release one.
Did it get you?
- Yes.
You or the camera?
- I don't know.
Let's try again.
You hear the ball accelerate.
The note goes up as it accelerates under gravity.
Fire two.
Fire three.
And now I think there's a parachute up there.
Can we have the parachute, please?
[Whooshing whoomping sound]
[Applause]
Ten years before that machine was made said Eric Eastwood that err...
was interested in a problem that had puzzled radar engineers for a long time.
Since the second world war.
They often saw slow moving targets, moving around over the countryside,
and couldn't explain what they were.
Using the powerful Marconi radar in Essex, Sir Eric Eastwood discovered
that most of these angels, as they were called for want of a better term,
were in fact birds.
I'm going to show you a film that he made.
There's a watch in the top corner of the film.
Those are planes moving over Heathrow.
And you see in the middle they keep disappearing as they land
and occasionally take off.
Gives some impression for the, of the job of air traffic controllers.
Now there's southern England, France and Holland.
You see some planes whizzing around
but the slow moving targets are birds migrating across the Channel.
And going up to East Anglia.
There's some clouds going up from the Isle of Wight towards the Midlands.
And there again planes and birds migrating south, in the opposite direction.
Across the Channel towards France.
Now there are ring angels.
You see up to the North West.
You see the ring angels going out and the line to the North East is the rising sun.
Wave after wave of starlings going out.
There are several roosts there but the best one is to the North West.
And finally a radar microscope close up view
of starlings radiating out from their roost at dawn.
Most of them have gone now.
The ripples get weaker and weaker and the show is over.