Winds The Weather


Winds

Documentary series about the weather looks at wind, caused by the interaction of temperature, pressure and the earth's rotation, which took scientists over 1,000 years to explain.


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Transcript


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# Let him blow, let him blow

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# From the east to the west.

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# I love you the best. #

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Wind.

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The British get a lot of it.

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Our language is full of wind and the words that we use to describe it are kind of windy words.

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Windbag, whistle down the wind, wind of change, it's an ill wind.

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We can't see the wind.

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But we can feel it...

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and see its effects.

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I was frightened stiff because it was something I couldn't control.

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So how did we discover what causes the winds?

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Where they come from? Why they change?

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How to forecast them, how to harness them.

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Scientists are learning to predict the slightest breeze,

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and the fastest tornado.

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Although we understand the wind,

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will we ever control it?

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# From the east to the west

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# I love you the best. #

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Air is invisible...

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until it moves, then we call it wind.

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Once, we believed the wind was a punishment from the gods.

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Then science explained the wind.

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It took over 1,000 years to put the pieces together.

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But now we know.

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It is the interaction of temperature, pressure and the Earth's rotation.

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It's a complex cocktail.

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Wind is moving air,

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so we are standing on the Earth's surface

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and if the air moves past us, then we call that wind.

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The atmosphere moves far more in some places than in others.

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We British get a lot of movement, a lot of wind.

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Why is that?

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We're right on the eastern seaboard

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of a major ocean and this puts us right at the end of the storm tracks.

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The storms form in the western part of the Atlantic generally,

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and they come across and then, of course, we get hit by them.

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And the first port of call for the Atlantic winds

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is an island in the Hebrides, off the west coast of Scotland.

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This is Tiree, the windiest place in the British Isles.

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Maybe not today, but don't be fooled.

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You step out of the front door

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and if you're not leaning forwards at 45 degrees

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you're going to be blown over.

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It's a different experience altogether and most people coming up here

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who haven't experienced that kind of wind before are very welcome to come up here in December, January

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and February, and you won't know what you're in for until you do actually experience it.

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Tiree is an island formed from windborne sand. There are few trees here.

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It's so flat and low there's nothing to stop the winds as they rush onto mainland Britain.

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And once the wind arrives, we never know quite what to expect.

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It can be playful, exhilarating,

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buffeting, and threatening.

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What begins as a whisper

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can become a shout, and the shout a scream.

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The wind blows good fortune as well as bad.

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On February the 5th 1941, off the Isle of Eriskay in the Hebrides,

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a ship called the SS Politician was blown onto the rocks.

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Aboard her were 22,000 cases of finest scotch whisky.

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There was a war on and you couldn't get whisky for love nor money.

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But the west wind delivered 264,000 bottles to the islanders.

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They liberated 84,000 before custom officials blew the wreck sky high.

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It's an ill wind, they say.

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But how can the wind disperse a fleet or deliver crates of whisky?

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The first clue comes to us from the seafaring Greeks.

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Aristotle proposed that the winds were "exhalations"

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caused by the sun's effect on the Earth.

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During the day, where the sun hit dry land,

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Aristotle said there would be warm, dry exhalations.

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Where the sun hit water, or snow, cool, moist exhalations.

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According to Aristotle, each evening these large blocks of warm and cool air would mingle

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as in a gentle breeze, or wrestle and clash like two warring gods.

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Today, scientists recognise the meeting of warm and cold air as a front.

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The way that the atmosphere organises this is it brings warm and cold air to close proximity,

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and this is what we call a front.

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So you have a front forming where there is a very sharp gradient in temperature.

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In the laboratory, it's possible to simulate a simple

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cold front just by adding salt and dye to water at one end of a tank.

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Cold air, represented by the blue water, is denser and heavier than warm air.

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When a cold front pushes forward, the warmer air rises over it.

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The movement of warm and cold air at the fronts gives us much of the wind we experience.

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The greater the temperature difference at a front, the stronger the wind.

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And Aristotle was right.

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It is the sun that drives the circulation of these air masses.

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The cause of the wind is actually the sun in the first place.

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That's what starts it all off.

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The sun comes and it stirs it all up and it creates temperature contrasts and we get wind.

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Britain is an exciting place to live, in terms of the weather.

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Perhaps if you were in a more continental location, you'd tend to get hot summers

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and cold winters, but you wouldn't get the variety of fronts that we see from day to day in our weather.

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# Stormy weather

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# since Monday night... #

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Exciting, perhaps.

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But some of us tend to take these fronts and winds rather personally.

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Paul Rose is an explorer and sailor.

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He knows what it's like to be on the receiving end of the wind.

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I've been in situations in my life

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when I'm pretty certain that wind's out to get me and has a personality!

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No matter how much rational and science thinking you might have,

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that the wind is completely impersonal...

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Forget it, because when you're really up against it, you're pretty sure it's out to get you.

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Some believe the wind is heaven-sent.

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Others are sure it comes from elsewhere.

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My mother's favourite phrase was, even if it was only slightly breezy,

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she'd say, "This wind is straight from Siberia."

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And that's interesting, the idea that somehow the wind has come from somewhere else to torment us.

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The Greeks blamed the gods for their torment.

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Zephyrus was the friendly god.

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He was the one who had the pleasant breezes.

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He's wearing light clothing, smiling, bringing in bowls of fruit.

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You have Kaikias, he's got a great big sort of shield and it's full of hailstones.

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That's the vicious north-easter that sweeps down.

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The Greeks were fascinated by the winds.

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They're called arrogant,

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wild,

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uncontrollable, vicious.

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And for this, the gods got so sick of them that they had them put

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under a king, Aeolus, and walled up in a cavern under a mountain.

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There they all are, like an army sort of forming ranks, and when

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the doors open in the mountainside, out they go and hell breaks loose.

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It wasn't the gods that broke loose on the night of January 15th, 1968.

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What began with a cold front in the Caribbean

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ended with an almighty storm across northern Scotland.

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Wind gusts of 117mph were recorded on Tiree.

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On the Ayrshire coast, it woke a young girl.

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I could hear just this huge rushing noise outside of my bedroom window,

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and it sounded just like a steam train whooshing past.

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And then the storm force wind howled up the River Clyde.

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There it met the high tenements of Glasgow.

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Willy Mackie was just 21 years old, and living with his parents.

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Back in 1968, I stayed at 555 Dumbarton Rd,

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which was actually here.

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About three in the morning, there was a bang at the door

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and it was the neighbour across the landing.

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He shouted, "You'll need to get out quick because the building's falling down."

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All the people that stayed in the building ran into the middle of Dumbarton Rd.

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So we assembled there and did a head-count and found there was four people missing.

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That's what left of the chimney, which was about 15ft tall.

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And the wind blew the whole of that chimney over onto our roof

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and then from there, that chimney went straight through all the front bedrooms, right into the basement.

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But the wind didn't stop in Glasgow.

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It carried on, reaching the outskirts of Edinburgh.

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To come back after all these years...

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I found that difficult.

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That's very difficult, seeing the name. That's very difficult.

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Elsie Greenan, was also 21 in 1968.

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She'd recently married and was living with her parents in Northcote Place, Edinburgh.

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Her tenement building is now demolished.

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It's the first time she's returned to the area for many years.

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Roughly six o'clock in the morning, there was a huge, huge whooshing noise.

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It was just horrendous.

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Just this terrible, terrible noise.

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And I got up and switched the light on, and what had happened was the chimney in the kitchen

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had been blown over and the soot had come down the chimney in the kitchen and was all over the carpet.

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So my first thought was, "Oh, my God, Mum's new carpet."

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I went through to tell her.

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And when I opened the bedroom door,

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there was just nothing there,

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except this huge... huge pile of rubble.

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No ceiling. And the wind was unbelievable. It was awful.

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You don't think, when you're looking in on it, they're dead.

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You think they're under there and they're OK.

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But Elsie's parents were dead.

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Willy Mackie's neighbours were killed.

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In all, 20 people died, and the scars remain.

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To this day, if it's an exceptionally high wind, I mean a real high wind, I'm still nervous.

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I can, believe it or not, still taste the dust from that night.

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I can still smell it. I can still taste it.

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It's a thing that's never, never left me in all these years.

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By the morning of January 15th, the warring masses of warm and cold air left Glasgow in pieces.

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80,000 homes damaged by the winds.

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The next day, when we were watching the news and we heard

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about all the people that died, I just wanted to understand.

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"Well, how could wind be so strong, that it could blow down roofs, how it could kill people?"

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And I just became very fascinated about how the weather could be so severe

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that it could bring such devastation.

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You never think that a solid-built, as you think,

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tenement in Edinburgh,

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that this is going to happen.

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It's a freak, freak accident,

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you know,

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but put down as an act of God.

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So how CAN wind be so destructive?

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What makes it so powerful?

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We learnt from Aristotle that air currents move in part because of temperature differences,

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but there's something else.

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Air has weight,

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and it was this discovery that revolutionised our understanding of what makes the wind blow.

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Above my head at this moment, there's a lot of atmosphere,

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and it's pressing down on my head about...

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probably about half a ton on my head.

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Now, it might sometimes feel like that in the morning, but in general,

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one does not feel there's half a ton on your head, so why not?

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I mean, on my finger there's...there's a sort of huge amount of atmosphere pressing

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down on my finger, but there's also atmosphere pressing up on my finger, here, from the other side,

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so we don't feel it because it's pressing in in all directions. That's why call it pressure.

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It took a young Italian scientist to realise that air has weight.

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He wrote, memorably, "We live submerged at the bottom of an ocean of air."

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Evangelista Torricelli is an Italian experimentalist, a physicist,

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and he's working in the early 1640s.

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Torricelli's experiment was very simple,

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a glass test tube filled with mercury and a dish also filled with mercury.

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Then Torricelli turned the test tube upside down.

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Insert the bottom of the tube into a dish of mercury and stand it upright.

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Well, always... "Ptcch!" The mercury level drops.

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Some of the mercury slid down the tube, but instead of it all

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gushing out into the dish, most of it stayed in the glass column.

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Something was holding up the mercury.

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Torricelli concluded that it must be air pressure.

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The weight of the air on the surface of the mercury in the dish

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was squeezing the mercury up into the column and holding it in position.

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Torricelli noted that the column of mercury rose and fell within the tube.

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The higher the pressure, the more the column rose.

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In time, he was able to relate the movement

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of the mercury to weather patterns.

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High pressure signalled settled, fair weather.

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Low pressure warned of turbulence and storms.

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Wind is the movement of air from high pressure to low pressure.

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The air having weight feels perfectly natural to me, particularly as a sailor.

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The wind really does go from high pressure to low pressure.

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But it was Torricelli who figured it out.

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He actually invented what we think of as the barometer.

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I haven't got a barometer on this boat but I've been on enough boats where you look at it and sure enough

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the pressure's dropping, and it's dropping a lot.

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And immediately you think, "There's strong winds coming."

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Strong winds mean trouble ahead for sailors.

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But if they don't know the storm is coming, it can be disastrous.

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Storms have even changed the course of British history.

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In 1588, the Spanish Armada, in retreat from the English Navy,

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was desperate to sail round Britain's north-west coast.

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Violent westerly winds dashed them onto the rocky shores of Scotland and Ireland

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and destroyed half the entire fleet.

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The wind destroyed five times as many ships as did the English.

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Queen Elizabeth I, quick to claim divine intervention, had medals struck with the legend

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"He blew with His winds & they were scattered."

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Her archenemy Philip of Spain said, ruefully,

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"I sent the Armada against men, not the winds and waves of God."

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It was a low pressure system blowing in from the Atlantic that scuppered the Armada.

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If the barometer had been invented in 1588,

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they would have seen the mercury dropping and sailed for shelter.

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In Torricelli's day, the rise and fall of the mercury was measured in inches.

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Today, meteorologists measure pressure in millibars.

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These differences in pressure are not actually all that huge.

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The mean pressure at the surface of the Earth is a 1,000 millibars or so

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and you don't get much more than, say 30 millibars' difference either side of that.

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The swings of pressure are surprisingly small to generate all that we experience as weather.

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The variations in pressure are small,

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but they occur in a very narrow space called the troposphere.

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The troposphere is a narrow band of air,

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so thin that if the planet was the size of a beach ball and you were to wrap the beach ball in cling film,

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that's how thin the troposphere is.

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And because it's so thin and narrow, it amplifies the effect of pressure changes.

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And all the many forms of wind occur there,

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between the stratosphere and the sea.

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The air moves because the pressure is different.

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High pressure on one side, low pressure on the other,

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and so it moves, it accelerates towards the low pressure, so that's why air starts to move.

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But it can move very rapidly because of the temperature contrasts around

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and because of the rotating planet that we live on, planet Earth.

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So, wind is just air trying to move from high pressure to low pressure,

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sucked and blown around with a constant unpredictability.

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In turn, tragedy and comedy.

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We can see what this movement of air does, but the wind is invisible.

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We can't see the wind...or can we?

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We can't see the wind with our eyes of course,

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because the air's transparent, so we have to find some way of sensing the wind,

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and that means we have to bounce something off the air.

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We have to get the air to give us a signal.

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One way of doing that is to use VHF radar.

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At this facility in the Welsh hills, Professor Vaughan and his team use radar to track the wind.

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Basically, what this field of aerials does

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is it transmits a pulse of radar energy,

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and as this very loud pulse, which shouts very loudly into the atmosphere,

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and then it listens very intently for a very faint echo, and that's basically what this thing does.

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The radar tracks turbulent air.

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The returning echo provides a measurement of wind speed and direction.

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So, shouting at the heavens is not the waste of time it may once have been.

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Professor Vaughan gets answers, radar echoes that give us a picture of the winds.

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Well, what you've got here is a day's worth of measurements from the radar.

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This was a day when we would have had a front.

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That's a warm front there.

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And similarly, on this side, we would have had a cold front coming along.

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What we're looking at is a section through the troposphere,

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a constantly unfolding picture of temperature and pressure

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within the thin atmospheric membrane that wraps our planet.

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We're measuring winds, we're measuring the structure of the atmosphere, and we're

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measuring it all 24/7, and we're measuring it every two minutes.

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So that's what this thing can do for us.

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An up-to-the-minute picture for the movement of winds.

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Today, sophisticated radar reveals the wind.

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In the 17th century, merchants were desperate for ways to make the winds visible.

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The world had been opened up by great adventurers such as Columbus and Magellan.

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Now vast fortunes beckoned for those who could master the winds and rule the waves.

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Sailors needed their own picture of the wind.

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They all had very little to go on, very little indeed, and in fact,

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knowledge of wind direction and prevailing winds that we call trade winds,

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was a closely guarded secret, because if you found them and your enemy, if you like,

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didn't have them, you'd have an advantage.

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Mariners were using the trade winds to cross the great oceans.

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At the equator, the winds blow from east to west.

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But when the ships sailed north, the winds changed direction.

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The mariners needed the winds to be mapped.

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But a young British genius asked a more fundamental question about the winds.

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His name was Edmund Halley.

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He's one of the great exotics of science, no doubt about it.

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Halley has travelled quite a lot.

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He's already been on an expedition to St Helena in the South Atlantic,

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so he's travelled through the trade wind zones and some of the most complex storm systems of the world.

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On his travels, Halley made systematic observations

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of wind patterns in both the northern and southern hemispheres.

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He puzzled over the behaviour of the winds.

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Why, for instance, in the northern hemisphere,

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is the predominant wind pattern from the north to the equator,

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and the south, from the south to the equator?

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There's this great vortex somehow, in two hemispheres.

0:24:550:24:59

Halley reasoned that the sun must be playing a part.

0:25:010:25:05

Could it be that there was a hot spot on the Earth's surface where the sun is directly overhead?

0:25:050:25:10

In the course of a day, this rotates completely around the world,

0:25:100:25:15

and as it does this, you have a column of air constantly rising underneath the sun.

0:25:150:25:22

Halley argued that this constantly rising column of air would move towards the poles.

0:25:260:25:31

Cold air from the poles would move in to take its place.

0:25:310:25:35

Halley had discovered that it's the sun that drives the circulation of air around the globe.

0:25:370:25:42

Basically, it's the sun.

0:25:420:25:44

We get our weather from the sun and the sun heats the equator more than it heats the pole,

0:25:440:25:49

so it sets up a temperature gradient.

0:25:490:25:52

This temperature gradient then drives the weather systems.

0:25:520:25:56

What they're trying to do, these weather systems, is to take heat from the equator to the pole, so

0:25:560:26:01

our poles are a lot warmer than they would be if there wasn't circulation

0:26:010:26:06

in the atmosphere and in the ocean bringing heat in from the equator.

0:26:060:26:09

Edmund Halley is chiefly remembered for discovering a comet that bears his name.

0:26:090:26:14

But his discovery that the sun is the engine of the winds is just as significant.

0:26:140:26:20

He basically gets it right by 1690, and I think that is utterly amazing.

0:26:200:26:27

From the data he gathered from the world's oceans, Halley made detailed notes on wind direction and speed.

0:26:290:26:36

The result was the first ever wind charts,

0:26:360:26:39

described as "a masterpiece of practical navigation."

0:26:390:26:43

His charts were detailed and accurate.

0:26:430:26:46

They gave mariners and merchants THE picture of the winds that they needed.

0:26:460:26:51

Halley was correct that the sun generated the circulation of air.

0:26:510:26:55

But that's not enough to explain the direction of the winds.

0:26:550:26:59

It would take another 50 more years and another British genius

0:26:590:27:03

to understand that there was an additional force that drove the wind.

0:27:030:27:06

The 18th century was the golden age of the amateur scientist.

0:27:110:27:15

One such was George Hadley, so amateur no image of him exists.

0:27:180:27:24

But in 1735, this unknown set out to solve the riddle of why the great

0:27:240:27:29

winds of the world blew in different directions.

0:27:290:27:32

Hadley accepted Halley's idea that air circulated between the poles and

0:27:320:27:37

the equator, but realised that there had to be a second force at play.

0:27:370:27:42

Something more than the sun was making the wind go sideways.

0:27:420:27:46

And then he got it.

0:27:480:27:50

Wind direction comes from the rotation of the Earth.

0:27:500:27:54

The impact of this rotation on the atmosphere is known as the Coriolis force.

0:27:540:28:00

The Coriolis force...

0:28:010:28:03

Ahhh!

0:28:030:28:05

That's such a naughty question!

0:28:050:28:08

Right, OK...

0:28:080:28:11

The Coriolis effect.

0:28:110:28:13

It's a difficult thing to understand, I think.

0:28:130:28:15

It's to the left... Oh, is it to the right?

0:28:150:28:18

-I always get it wrong.

-Ummm...

0:28:180:28:20

Ask that to Brian Hoskins.

0:28:220:28:24

If you're on a roundabout, in the park...

0:28:240:28:28

..and I throw a ball at you, straight at you...

0:28:280:28:31

..it'll appear to the person on the roundabout, if you like, that the ball follows a curved path.

0:28:310:28:38

In fact, the ball is travelling straight.

0:28:380:28:40

The Coriolis force is linked to the spinning of the Earth...

0:28:400:28:45

When you're on a rotating system and you start to move, there's all sorts of different things happen and you

0:28:450:28:51

tend to be flung off at right angles to the way you want to go, and that's what the Coriolis force is.

0:28:510:28:56

It's saying, "OK, you want to go to that direction? I want you to go that direction."

0:28:560:29:00

George Hadley could only write about the impact of the Earth's rotation on the winds.

0:29:000:29:05

Professor Hoskins has found ways of showing us.

0:29:050:29:09

Here we've got an old satellite dish which we've painted black,

0:29:090:29:14

and if I put a ball bearing on this,

0:29:140:29:17

it's just as you'd expect.

0:29:170:29:19

It rolls towards the middle.

0:29:190:29:21

Gravity pulls it down towards the middle, there.

0:29:210:29:24

Professor Hoskins spins the dish to simulate the rotation of the Earth.

0:29:240:29:29

To witness the effect of this rotation on a travelling object,

0:29:290:29:33

he has set up a revolving camera above the dish.

0:29:330:29:36

The ballbearing represents the air moving across the Earth's surface.

0:29:360:29:40

Clearly, the ball is travelling backwards and forwards,

0:29:420:29:46

but the revolving camera shows that it is going in circles as well.

0:29:460:29:51

You can see from here, it's almost rotating with the dish,

0:29:510:29:54

but when you look on there, what you see relative to this camera that's rotating with it,

0:29:540:29:59

it's going round almost in circles, snaking on itself.

0:29:590:30:03

This simple experiment demonstrates that air is spun around by the earth's rotation.

0:30:050:30:10

The reason that it's complicated is because the earth is spinning

0:30:100:30:14

and the spinning means you can't just take warm air from the Equator and just move it to the Poles.

0:30:140:30:21

A second demonstration shows why air can't move in a straight line from the Equator to the Pole.

0:30:270:30:33

Particles of aluminium are suspended in water.

0:30:330:30:36

This is like a polar view of the planet and its weather.

0:30:360:30:41

The centre, the pole, is cooled.

0:30:410:30:44

The outside, the equator, is heated.

0:30:440:30:48

Now this world revolves.

0:30:480:30:50

The tiny flakes of aluminium make the invisible visible.

0:30:530:30:57

For water, think air.

0:30:590:31:02

Rotation spins the particles around as they journey from the warm part of the apparatus to the cold.

0:31:020:31:09

Just as moving air is spun as it travels from the Equator to the Pole.

0:31:090:31:14

This is the air swirling around the planet.

0:31:160:31:19

The wind in a state of chaos.

0:31:190:31:22

George Hadley had worked it out.

0:31:250:31:27

There were not one, but two elemental forces to the wind.

0:31:290:31:33

The sun, which heats the air at the Equator, and the rotation of the earth,

0:31:360:31:41

which bends and twists the air as it journeys towards the Poles.

0:31:410:31:45

The planet is locked into a constant struggle to balance temperature and pressure

0:31:520:31:57

while subject to the forces of the earth's rotation.

0:31:570:31:59

We experience these warring forces as wind.

0:32:020:32:05

This is a picture of a hurricane.

0:32:140:32:17

The coriolis force is spinning it in an anti-clockwise direction.

0:32:170:32:21

Hurricanes are the whirlpools of the air - feeding on heat and turning it into wind energy.

0:32:210:32:28

Hurricanes themselves grow over the sea because they need the energy

0:32:280:32:34

that they obtain from the sea to make them grow.

0:32:340:32:37

They have to have a sea temperature of at least 27 degrees Celsius.

0:32:370:32:42

In the Mexican Gulf, the sea is warm - so hot it's like high octane fuel to a passing hurricane.

0:32:420:32:49

In 2005, a deadly hurricane struck the United States -

0:32:530:32:57

Hurricane Katrina, in which almost 2,000 people lost their lives,

0:32:570:33:02

was the costliest natural disaster in US history.

0:33:020:33:06

For eight days, Katrina journeyed around the Gulf of Mexico, gathering strength and wreaking havoc.

0:33:110:33:17

There is another kind of rotational wind that causes havoc - the tornado.

0:33:230:33:28

The formation of tornados happens in a completely different way from hurricanes.

0:33:280:33:34

They're much smaller features to start off with

0:33:360:33:39

and they also form out of one particular cloud which is called a cumulonimbus cloud.

0:33:390:33:44

Now, if those clouds build high enough and have enough energy,

0:33:460:33:51

then they will spawn what we call funnel clouds, which come out of the base of those clouds

0:33:510:33:58

and once they touch the ground they become tornados.

0:33:580:34:01

Britain gets lots of tornados.

0:34:010:34:04

One year saw over 150.

0:34:040:34:06

In relation to its area, Britain has the highest number of reported tornados in the world.

0:34:060:34:11

This is the seaside resort of Bognor Regis.

0:34:190:34:23

On 28 October 2000, late in the afternoon, a tornado ripped through the town.

0:34:230:34:29

A tornado wind can reach speeds of 300mph.

0:34:400:34:44

Anything in its path is swept aside or dashed to pieces.

0:34:440:34:47

Tornados cut a swathe of destruction and terror.

0:34:470:34:52

All these bricks started hitting the door and I've run out screaming. I thought the kitchen had blown up.

0:34:520:34:57

No-one was hurt...

0:34:580:35:01

..until the tornado reached the Riverside Caravan Centre.

0:35:030:35:06

I was just leaving the park, coming down the front drive,

0:35:080:35:12

and I heard a really, really loud crash.

0:35:120:35:15

I looked in my mirror and I saw a tornado go across the back of the road.

0:35:150:35:22

Dorothy Allwright was directly in its path.

0:35:220:35:27

I saw what I thought was a bush.

0:35:270:35:30

It had come out of a bin or something, just coming across the car park.

0:35:300:35:36

And then all of a sudden, something...hit the caravan.

0:35:360:35:42

I can only describe it as a graunching noise.

0:35:420:35:45

And that must have been the chains, because the caravan was well chained down.

0:35:450:35:52

The chains started to snap, and then up in the air we went.

0:35:520:35:57

I can remember screaming as we were moving,

0:35:580:36:03

and then all of a sudden down we must have plopped.

0:36:030:36:08

The tornado ripped Dorothy's caravan from the ground, spun it in the air

0:36:080:36:13

and slammed it down on top of that of her neighbour.

0:36:130:36:16

Everything started to go haywire. I think panic mode came in.

0:36:160:36:21

Petrified.

0:36:210:36:22

I could just remember screaming, "What is happening?"

0:36:220:36:26

It then went past the first caravan, did no damage to that at all,

0:36:260:36:32

came across the fun-pool that we see here and picked all the water up.

0:36:320:36:37

It seemed to suck it up as it went passed.

0:36:370:36:40

I could see it in my car mirror throwing the water everywhere

0:36:400:36:44

as it went through those caravans there and went. Just left the site.

0:36:440:36:48

The emergency services rescued Dorothy, her friend and her two dogs from the mangled wreck.

0:36:500:36:57

I was frightened stiff because it was something that I couldn't control.

0:36:570:37:03

Tornados can spring up in a matter of minutes and can disappear just as quickly.

0:37:110:37:16

Until now, they've been impossible to predict.

0:37:160:37:20

But at a research establishment in Chilbolton, Hampshire,

0:37:320:37:35

scientists on the frontier of weather forecasting are about to change that.

0:37:350:37:40

Sensitive radar is being used to predict the formation of highly dangerous winds.

0:37:400:37:46

And they're doing it in an ingenious way,

0:37:460:37:49

turning a problem of 50 years ago into a solution.

0:37:490:37:53

In the early days of radar development,

0:37:550:37:59

progress was bedevilled by unexplained interference the boffins dubbed "angels".

0:37:590:38:03

The angels, as it turned out, were birds and insects

0:38:030:38:07

and that's what gave rise, half a century later, to the Chilbolton Project.

0:38:070:38:12

These scientists are trying to dramatically improve forecasting by close observation of nature.

0:38:140:38:21

What they're observing are insects.

0:38:210:38:24

Why do we need to look at the insects?

0:38:250:38:27

The insects are sitting there and they follow the wind.

0:38:270:38:31

The reason they go up in in the morning is to get a free ride

0:38:310:38:35

so they can follow the wind and migrate across the country.

0:38:350:38:38

On 28 July 2005, the Chilbolton radar was tracking insects.

0:38:420:38:47

Starting early in the morning, scientists watched a compelling story unfold on screen.

0:38:490:38:54

It ended with a tornado.

0:38:540:38:57

So this is the picture from the radar at 10-10.15 in the morning.

0:38:570:39:04

And this is a low level sweep so it's a map over the country.

0:39:040:39:07

Here's the radar in the middle, and out to about 40 or 50 kilometres in each direction

0:39:070:39:13

we're getting this very low level signal here and these are associated with insects.

0:39:130:39:18

The radar signal not only detects the insects, it also tracks their course.

0:39:200:39:26

Insects act as tracers for the wind's direction and speed.

0:39:260:39:31

These insects, you can see there's a lot of them here, so we're getting the winds,

0:39:310:39:36

every 100 metres or so we're getting a velocity of the wind.

0:39:360:39:39

Based on these observations, Professor Illingworth makes some predictions.

0:39:420:39:47

So we've got a way of measuring the air flow using the insects.

0:39:470:39:52

Can you see the insects formed in lines here?

0:39:520:39:56

This is where we're expecting to get rows of clouds forming.

0:39:560:40:01

By noon, storm-clouds have formed and they're heading north to Birmingham.

0:40:010:40:07

Later on the satellite picture, can you see that rows of clouds have formed in that direction?

0:40:070:40:13

That's from the satellite.

0:40:130:40:15

Now we've left the insects far behind. This satellite image shows a developing storm.

0:40:150:40:23

There's a much more power being reflected here, an enormous amount where it's white.

0:40:230:40:27

That's a very intense storm.

0:40:270:40:30

This is at 2.30pm, and indeed it was about 3pm, that's where the tornado developed over Birmingham.

0:40:300:40:38

Oh! There goes a roof!

0:40:380:40:41

In the space of five hours, what began with a swarm of insects ended with this.

0:40:410:40:48

The strongest tornado to hit the UK for 30 years.

0:40:480:40:51

It caused £40 million worth of damage and 19 injuries.

0:40:510:40:57

By tracking insects first thing in the morning, the Chilbolton radar

0:40:570:41:01

anticipated the Birmingham tornado two hours ahead of time.

0:41:010:41:05

The system was only being tested that day. So no warning was given.

0:41:060:41:11

Soon it will be in regular use.

0:41:110:41:14

The idea is that in a couple of years the insect winds will be measured by these radars over the UK

0:41:150:41:21

and at 10am in the morning on the day when it's forecast

0:41:210:41:25

that thunderstorms will break out somewhere over southern England,

0:41:250:41:30

this measurement of the winds will be put into the model,

0:41:300:41:33

therefore you'll be able to have a couple more hours more specific warning

0:41:330:41:38

of precisely where the storms are going to break out.

0:41:380:41:41

'And now the shipping forecast issued by the Met Office.

0:41:410:41:44

'Here are your forecasts for the next 24 hours.

0:41:440:41:47

-'Viking, variable, becoming cyclonic...'

-The familiar litany of the shipping forecast.

0:41:470:41:53

Required listening for those at sea.

0:41:530:41:56

Wherever the wind is and no matter how strong, we will be warned using a simple scale.

0:41:560:42:02

The Beaufort Scale.

0:42:020:42:04

Throughout history, scientists endeavoured to give us a picture of the wind.

0:42:080:42:13

Rear Admiral Sir Francis Beaufort decided to put it into words.

0:42:130:42:18

If you have a method,

0:42:180:42:20

an elegant method to talk about conditions,

0:42:200:42:25

and you can just do it in one word or one number,

0:42:250:42:29

it means if you pass the signals by flag or sound signals

0:42:290:42:33

or indeed on the radio, you don't have to have long, complex conversations.

0:42:330:42:37

Beaufort translated the winds in all their complexities of mood directly into mariner-speak.

0:42:370:42:44

Wind force one - light air of sufficient to give steerage way.

0:42:480:42:54

Force two - light breeze.

0:42:540:42:56

Force three - gentle breeze,

0:42:560:42:59

that in which a man of war with all sails set would go in smooth water from three to four knots.

0:42:590:43:05

And finally force 12 - hurricane,

0:43:080:43:11

on which no canvas can withstand.

0:43:110:43:14

The Beaufort Scale became the international standard for wind measurement and remains so today.

0:43:170:43:24

If I was on the radio now

0:43:240:43:26

and the communication was maybe noisy or was a long way and the signal was a bit weak,

0:43:260:43:33

I could pass on to somebody my local weather observation,

0:43:330:43:37

and say it's gusting force four and anyone in the world would know exactly what these conditions were.

0:43:370:43:43

The Beaufort scale went on to be interpreted for landlubbers.

0:43:430:43:48

Moderate breeze. Wind raises dust and loose paper.

0:43:480:43:52

And even appeared in France in a slightly more Gallic form.

0:43:520:43:56

Force 12. Les enfants moins de six ans volent.

0:43:560:44:01

Children less than six fly.

0:44:010:44:04

Francis Beaufort was pivotal in putting a young Charles Darwin on board the HMS Beagle,

0:44:080:44:13

captained by Robert Fitzroy.

0:44:130:44:16

They set sail in the summer of 1831.

0:44:160:44:19

It was a voyage that would change history.

0:44:190:44:24

People often forget what that expedition was for.

0:44:240:44:27

The real purpose of the expedition was for meteorological, magnetic and oceanographic purposes.

0:44:270:44:34

How did the great forces of the world work together?

0:44:340:44:39

Especially in those places where HMS Beagle spent so much of her time, off South America -

0:44:390:44:45

some of the bleakest, most devastating seas in the world.

0:44:450:44:50

What did the winds do there?

0:44:500:44:52

So in many ways, the Beagle actually starts off as a geophysical and meteorological expedition.

0:44:520:44:58

Evolution is a sideshow.

0:44:580:45:01

As a meteorological expedition it was a triumph.

0:45:050:45:09

On his return, Robert Fitzroy was chosen to head up a new, experimental government department.

0:45:090:45:15

The British Meteorology Office was born,

0:45:150:45:18

familiar to us as the Met Office.

0:45:180:45:21

The Met Office starts as a way of coordinating all the information about weather for Britain,

0:45:210:45:28

for Europe, and especially, of course, for the Navy and for the merchant marine.

0:45:280:45:35

Britain was developing the biggest merchant marine on the face of the earth by the 1840s.

0:45:350:45:41

Steam ships of course were coming in, but most of the traffic globally was still under sail,

0:45:410:45:47

so the merchants of places like London, Liverpool, Newcastle wanted the most accurate data they could

0:45:470:45:54

for how to understand what was happening basically at sea and how to make sense of it.

0:45:540:46:00

Fitzroy didn't waste a minute.

0:46:020:46:04

He asked ships' captains to feed-back wind and weather information from all over the globe,

0:46:040:46:10

where possible using the newly invented telegraph.

0:46:100:46:13

CLICKING

0:46:130:46:15

And he put the data to good use.

0:46:150:46:18

In 1860, Fitzroy issued the first "weather forecast".

0:46:180:46:23

Within a year, weather forecasts were a daily feature of the press.

0:46:230:46:29

The British public were learning to read the wind.

0:46:290:46:32

Meteorology was a craze.

0:46:350:46:37

Weather forecasting attracted the learned and the eccentric alike.

0:46:370:46:41

None more eccentric than the inventor of the Tempest Prognosticator.

0:46:410:46:46

Created by George Merryweather, it consists of 12 glass jars each containing a leech.

0:46:530:46:59

At the top of each jar there is a piece of whalebone attached to a chain.

0:46:590:47:03

Each chain is attached to a hammer.

0:47:060:47:08

Dr Merryweather thought that leeches were sensitive to atmospheric pressure.

0:47:080:47:13

If the pressure fell, they would climb from their private lagoons,

0:47:130:47:17

dislodge the whalebone, pull on the chain and ring the bell.

0:47:170:47:22

Merryweather sought government funding for the project

0:47:220:47:26

in order to establish a national grid of leech barometers.

0:47:260:47:30

He didn't get it.

0:47:300:47:31

The Met Office wisely put its trust in Robert Fitzroy instead.

0:47:340:47:38

Sciences like meteorology and engineering were the new articles of faith in the Victorian age.

0:47:410:47:47

The wind was a spur to both.

0:47:470:47:49

While science predicted the winds, engineers built structures to defy them.

0:47:490:47:54

The Tay Bridge was one such structure.

0:47:570:48:00

When it opened for business in June 1878, it was the longest bridge in the world, over two miles long.

0:48:000:48:07

The poet William McGonegal wrote in celebration.

0:48:070:48:11

Beautiful new railway bridge of the silvery Tay

0:48:110:48:14

with your strong brick piers and buttresses in so grand array

0:48:140:48:18

and your thirteen central girders which seem to my eye strong enough all windy storms to defy.

0:48:180:48:25

The engineer who built this bridge, Thomas Bouch, believed he had the measure of the wind.

0:48:290:48:34

He was wrong.

0:48:340:48:37

On 28th December 1879, an almighty storm blew in from the Atlantic.

0:48:370:48:43

First it hit Tiree.

0:48:430:48:45

The old household was down by the shore there, very near the shore edge.

0:48:470:48:53

The tide and the wind got up so much

0:48:530:48:56

that eventually they had to abandon the house.

0:48:560:48:59

They had to come out in the storm and make their way up the lane between the crofts here.

0:48:590:49:05

They must've been on their hands and knees

0:49:050:49:08

because the old grand-uncle described how, as they were coming up, a barrel flew over their head.

0:49:080:49:14

And that was the same night that the Tay Bridge disaster occurred.

0:49:140:49:19

28th December 1879.

0:49:190:49:22

When these violent winds reached the Tay Bridge, they tore into the structure at right angles.

0:49:280:49:33

The centre section collapsed, taking with it a train running along its single track.

0:49:330:49:39

75 people were on board.

0:49:460:49:48

75 lives were lost.

0:49:480:49:51

It remains the worst structural disaster in British history.

0:49:510:49:56

The bridge he so admired now in ruins, the poet McGonegal took up his pen again.

0:49:560:50:03

Twas about seven o'clock at night and the wind blew with all its might

0:50:030:50:07

and the rain came pouring down and the dark clouds seemed to frown

0:50:070:50:11

and the demon of the air seemed to say, "I'll blow down the Bridge of Tay."

0:50:110:50:16

And you can feel the wind blowing through those verses, I think, anyway.

0:50:160:50:20

150 miles to the west, on Tiree, the islanders and their ancient crofts rode out the winds.

0:50:280:50:35

They, and their homes, have evolved with the wind.

0:50:350:50:40

The old thatched cottages, which were the double-walled, thick-walled house,

0:50:400:50:46

and the thatch supported on the inner of two walls.

0:50:460:50:50

When the wind strikes the outer walls,

0:50:500:50:54

it's deflected up and going over the top of the roof, going around the thatch,

0:50:540:51:00

it has an effect of holding the thatch down, rather than tearing at it or damaging it.

0:51:000:51:07

The engineers that built the Tay Bridge could have learned much from the people of Tiree.

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Designing structures to withstand the winds has never been a simple process.

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This is the Tacoma Bridge in Washington State, USA.

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This remarkable footage captured its final moments in 1940.

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Destroyed by a 40 mile an hour wind.

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A gale, but not a hurricane.

0:51:460:51:49

The Taipei 101, once the tallest building in the world, is in a Typhoon hotspot.

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It has been built to accommodate the winds.

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When they blow, the tower will bend and bounce back.

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The Tay Bridge was built to last, the Titanic was unsinkable, the Taipei Tower is typhoon-proof.

0:52:200:52:27

It's not the Gods we place our faith in now, it's engineers and scientists.

0:52:300:52:35

But they have their limits.

0:52:350:52:38

Winds can be explained.

0:52:380:52:41

Winds can be anticipated, but they can never be mastered.

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Yet the winds can be harnessed. We've done it for thousands of years.

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Now its awesome power is attracting the attention of an energy-hungry world.

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Britain has abundant supplies.

0:53:010:53:03

Modern alchemists are turning wind into energy.

0:53:050:53:09

It is sort of magic. When you look at a cold wind and it turns into a hot fire.

0:53:090:53:14

Its marvellous. Its engineering at its best.

0:53:140:53:17

Gordon Proven has been designing and making wind turbines for nearly 30 years.

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His factory in Scotland makes 20 wind turbines a week with orders from all over the world.

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It is relatively simple, but complicated to make work.

0:53:320:53:35

We have wings, like the wings of an aeroplane, which rotate.

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They produce a forward force,

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so they'll rotate just like a kids windmill at the fairground.

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Then we have a shaft that goes to a direct drive generator.

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We have two plates of magnets which rotate past our windings of copper.

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When you pass a magnet past copper, you produce an electric current.

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We take that current out,

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put it into some electronics, and feed it into the grid. Easy.

0:54:090:54:14

The first electricity-producing wind turbine was invented over 100 years ago.

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It was a remarkable Scottish engineer, James Blyth, who led this energy revolution.

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In 1887, Blyth successfully generated electricity from a wind turbine.

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It was a world first.

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This photograph shows his experimental turbines in front of his cottage.

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This one shows the turbine he built for the Montrose lunatic asylum.

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It generated 10 horsepower - enough to light the entire building -

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and ran for nearly 30 years.

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This is Professor Blyth's machine.

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It is giant. These things are about 4 metres in height.

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My calculations indicate that it was about 2% efficient.

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He's got too many cups. One cup is shading the other one.

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He's the first guy in the world to make an electricity-producing wind turbine,

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even though it's only a twentieth of the efficiency of our modern machines.

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It got to work and it lasted 27 years, which is fantastic.

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And its thanks to the pioneering spirit of James Blyth

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that the islanders of Tiree can harvest the wind - their most abundant asset.

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At the eastern end of the island they're planning to erect their own wind turbine.

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We've spent the last three or four years

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pulling together a plan to erect a single wind turbine,

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which will be around 900 kilowatts,

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and will be based on the far east of the island.

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And that will generate, hopefully, depending on if we're lucky,

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around £300,000 of income for the community each year.

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It's definitely something that makes life, at times here, challenging.

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To actually get a payback and use a natural resource that is completely renewable and sustainable,

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I think everyone likes the idea.

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The wind that has scoured this bleak land for thousands of years

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may one day earn this community thousand of pounds a year.

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Money galore. It buys a lot of whisky.

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So now we know.

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We know what the wind is and what causes it.

0:56:410:56:44

We have weather forecasts on the TV, on the radio, on our laptops, even on our telephones.

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Our obsession with the weather is what makes us British.

0:56:520:56:56

No, British weather is what makes us British.

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POP MUSIC PLAYS

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Never knowing what to wear, when to barbecue, vest or no vest - never prepared.

0:57:080:57:13

The winds that blow on to our shores will bring good and ill in equal measure and we'll never know which.

0:57:160:57:22

Sometimes both.

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A mixed blessing.

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Our attitude to the wind is ambivalent at the moment.

0:57:270:57:30

We're living this life - in and out of aeroplanes, taxis, cars and trains, then off to work.

0:57:300:57:36

The only time we might get engaged with the wind is

0:57:360:57:39

when our umbrella goes inside out or your hair gets messed up.

0:57:390:57:43

I'm not sure we do respect the wind enough.

0:57:430:57:46

I mean, it's an incredibly powerful force of nature

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and those of us that live in Britain,

0:57:490:57:52

I don't think we offer enough respect to the great winds of the earth.

0:57:520:57:58

Documentary series about the weather. This episode looks at wind - a phenomenon caused by the interaction of temperature, pressure and the earth's rotation, which took scientists over a thousand years to fully explain.

We witness some remarkable wind-related stories, such as the tornado that flung Dorothy Allwright and her caravan into the air, and how Scottish engineer James Blyth invented the first electricity-producing wind turbine in 1887.

Once we looked to the gods to explain the wind, until science unlocked its mysteries. Today, we may have come to understand the wind, but we have also realised that we will never master it, and that this elemental force cannot be ignored.


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