The Transit of Venus Horizon


The Transit of Venus

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MUSIC: Little Green Bag by George Baker Selection

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# Yeah...

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# Lookin' back... #

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Just after 11 o'clock tonight,

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a rare event is going to take place in our solar system

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and it won't happen again in our lifetime or that of our children or even our grandchildren.

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In fact, it won't happen again for over a century.

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In just a few hours' time,

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Venus will begin its journey across the face of our sun,

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giving us the opportunity to watch its transit for the very last time.

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This is going to be a truly beautiful spectacle,

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but it is far more than just that.

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It's helping us answer some of the most profound questions we can ask

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about life in our own solar system.

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And it's helping astronomers explore the realms of much more distant stars in the search for life

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-on planets hundreds of light years away.

-You need to keep watching

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because tonight is your very last chance to witness the transit of Venus.

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This is the Observatory Science Centre, for decades the home of British astronomy.

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And in just two hours it will all begin.

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Across the globe right now, telescopes are being aligned and focused on Venus

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so that we can better understand the secrets of our universe.

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Transits represent some of our greatest scientific achievements

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and to me they stand for our insatiable desire to constantly push the boundaries of our knowledge

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and to explore the unknown.

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So tonight it feels like I'm part of a very special moment in history

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and it's a moment that you can be part of, too.

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'As stargazers across the world are getting ready,

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'we'll be showing you why this event is so important.'

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You're sure that's Venus?

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'From the first transits that are the basis of all modern astronomy

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'to the one tonight that's helping us search for alien life.

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'And if you want a piece of the action for yourself, we'll be showing you how.'

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The reason the transit of Venus is so rare is that you need an unlikely set of events

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to all come together. So this is Venus and the Earth in orbit around the sun.

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Now Venus travels faster than the Earth.

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And its orbit is shorter.

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For a transit to happen, it has to overtake us, but that only happens once every 1.6 years.

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Not only that, but Venus's orbit is tilted compared to the Earth's

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at an angle

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of 3.4 degrees.

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And that means that Venus's and Earth's orbits will only ever cross at two points.

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But because of the relative speeds of Earth's and Venus's orbits

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and because of their position relative to the sun,

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only two transits, separated by eight years, will happen every 100 years or more

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and one of them is happening tonight.

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'All astronomy today is built on one particular transit that happened over two centuries ago

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'and observing it led to one of the most epic voyages in history.'

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On August 26th, 1768,

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Captain James Cook, then a young lieutenant, embarked on one of the greatest ever voyages of discovery.

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It was a journey that was fraught with danger. The men on board knew

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that half of them probably wouldn't make it home alive.

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But it was all for one magnificent goal,

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to reach Tahiti in time to observe the transit of Venus.

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For me, Cook's voyage was like a modern space mission,

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a voyage of discovery, a testing ground for the latest technologies,

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but above all a test of human endurance. Just like astronauts voyaging into space.

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'And in 1768, they believe the transit was a risk worth taking

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'because it held the key to a great mystery.

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'It promised to reveal nothing less than the size of the solar system.'

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As a scientist today, I feel humbled by the lengths people went to in those days to discover new things.

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I can't imagine putting myself through that ordeal.

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But finding the size of the solar system was the great mystery of the time,

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like understanding dark matter or detecting the Higgs-Boson is today.

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Observing the transit of Venus was the key to unravelling it.

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Without leaving the planet, how could you measure distances out in space?

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It had baffled the greatest minds for thousands of years.

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Astronomers at the time knew the relative distances of the planets from the sun,

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but they didn't know what this distance was in miles.

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It was like having a map without a scale.

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It was my all-time favourite hero, Edmond Halley, who realised that Venus held the key.

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He worked out that if you were in the right place at the right time during the transit,

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you could work out the distance between the sun and the Earth

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and he did it by using the most beautifully simple solution,

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a phenomenon you can observe by holding up one thumb and closing one eye.

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The principle is called parallax.

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It's the shift you see when you hold up your thumb and look at it first through one eye,

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and then through the other.

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You can measure the shift in position of your thumb, with the distance between your eyes

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and actually work out how far away your thumb is from you.

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In a stroke of genius, Halley saw that this simple technique can understand the solar system's size.

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He worked out that the problem could be solved

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by timing the transit from two very distant points on Earth.

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Effectively, it's like drawing the largest triangles ever in space.

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To do this, you need widely separated observers on Earth, for example in Canada and Tahiti.

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From those two different locations, they see Venus transiting the sun along two different tracks.

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And they can work out those tracks very precisely if they time the transits.

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That information, along with the distance between your two observers,

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allows you to build up the triangles that you need to work out the distance between the Earth and sun.

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'And this is why Cook made the 12,000-mile voyage to Tahiti.

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'And he wasn't alone.

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'Observers were sent to the four corners of the known world in the name of science.

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'And after eight months battling stormy seas,

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'desertion and even suicide,

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'Cook finally reached his destination, just in time to observe the transit.'

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When the time came, Cook and the other two observers set up their stations.

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They would have had a tent to keep them out of the heat of the sun and, of course, their telescopes

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with an all-important filter to block the glaring light of the sun and view the transit directly.

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'After the transit passed, Cook and his fellow astronomers compared notes.

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'But they found something they weren't expecting.

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'There was a difference between their timings.'

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What Cook noticed was something called the Black Drop Effect.

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I have a copy here of Cook's drawings and you can see

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the edge of the sun and then the disc of Venus.

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And, literally, a black drop appears between the two.

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This mean that getting those crucial timings, the contact times when Venus is at the edge of the sun,

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became incredibly difficult.

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'But it was a long journey home.

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'After the transit, Cook opened his sealed orders.

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'They told him to set off in search of unknown lands,

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'ones we now know as Australia and New Zealand.

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'So it was another two years before they eventually returned with their precious data.'

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Finally, back in London, it was down to the mathematicians to crunch the numbers.

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They collected data from expedition sites at over 40 locations around the globe

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and they came up with a number.

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They came up with 93 million, 726 thousand

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and 900 miles as the distance between the sun and the Earth.

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Now today we know, using modern radar equipment,

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that the distance between sun and Earth is just under 93 million miles,

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which means, incredibly, in the 1700s they were accurate to within 1%.

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'It was a real triumph for science and one that marked the birth of modern astronomy as we know it.'

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I find it simply amazing that in 1769 they could work out

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the size of the solar system.

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And this number, the astronomical unit, couldn't be more important today.

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It's the foundation of modern astronomy and without it, my job simply wouldn't exist.

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And just to think, they did all this using only the sun and Venus.

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It still blows my mind.

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In the early hours of tomorrow morning, you, like Captain Cook,

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will be able to view the transit.

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All around the world, scientists will also be observing and studying it,

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but this time they'll be looking for answers to new mysteries.

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This is a truly global event

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and your view depends on where in the world you're going to be.

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Not everyone is going to see the same bit of the transit.

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The first contact between Venus and the sun will occur at precisely 23:03:47 our time.

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So obviously the first places to see that will be those in daylight,

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so we're talking North America, East Asia and most of Australia and New Zealand.

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And then for the next six and a half hours, Venus will journey across the sun.

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Until, eventually, as the sun rises in the UK

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at precisely 05:37:20,

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if the skies are clear enough we should be able to spot the third contact

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as Venus touches the inner edge of the sun's disc before leaving it for the last time this century.

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For hundreds of years, Venus was shrouded in mystery.

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Because it's a comparable size to Earth and a similar distance from the sun,

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many thought that Venus was just like our own planet.

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But there was no real way to know because it lay hidden beneath a thick layer of cloud.

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'When they say, "Take me to your leader," and they take them to a creature like this,

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'you know they're on planet Venus.'

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Because we couldn't see its surface, we could only really hazard a guess at the planet's true identity

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and Venus has certainly fired our imagination over the years.

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# I'm your Venus, I'm your fire... #

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From poptastic tunes to great works of art,

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it's even seen highly unscientific attempts at matchmaking.

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'The most talked about woman in the world knows what she wants on Venus, too.'

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But as for the true Venus, it took us quite some time before we really got to know her.

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'Eventually, the Soviets sent a probe to have a look.

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'After 16 failed attempts,

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'one eventually managed to land on Venus's surface.

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'But these first pictures revealed something no one was expecting.'

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It soon became clear that our planetary neighbour had a very different temperament to ours

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and was nothing like the calm, tropical world we'd imagined.

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Venus was, in fact, a hostile, raging inferno,

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our polar opposite, our evil twin.

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Something had happened to Venus to change its fate,

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making it very different to Earth.

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And it's a mystery that has led scientists to search for answers here on our own planet.

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'If you want to understand Venus, you need to go somewhere a bit like it.

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'Somewhere like this.

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'Kilauea Iki crater on the big island of Hawaii.'

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This may seem pretty nasty, but this is mild compared with Venus

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because, for a start, I couldn't be standing on the surface there.

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The temperature is 460 degrees Celsius.

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That's hot enough to melt lead and certainly too hot for me.

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But even if I survived the temperature, the weight of the atmosphere would be crushing me

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because the atmospheric pressure on Venus is 92 times that on Earth.

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And that is like being squashed by a kilometre of ocean.

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'But what I really want to know

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'is what happened to Venus to turn it into such a hostile place.

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'How did Venus and Earth turn out so differently?

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'I spend my life studying the forces that shape our planet

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'and I know that the answer to this question lies deep in the heart of these two worlds.

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'And that's what scientists are studying here on Hawaii.'

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So why, apart from the amazing weather, work in Hawaii?

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There are many volcanoes just like Hawaii on Venus.

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I've been studying those

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for almost 20 years now and Hawaii is a great place to come and see

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the volcanoes we can't see directly on the surface of Venus.

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I mean, the thing that I really like about volcanoes is that they link

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the interior, which is the part that I study most, to the surface, which we can see on other planets.

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It feels like we're... I don't want to say like we're on a different planet,

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-but that's what I want to say!

-I'm sure it looks a lot like this on Venus.

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I think we've reached the end of the road here!

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-Wow! Look at that.

-Yeah, geology in action, huh?

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-How long has this been here?

-This is less than 10 years old. 2003.

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-It just swept over the road. You used to be able to drive all the way across...

-But not any more.

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'Sue has been piecing together a picture of what's happening on the surface of Venus

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'in an attempt to understand what's going on inside it.'

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No humans have ever visited Venus and it's such a long way away,

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-how do we know there are volcanoes there?

-Well, in the '90s,

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there was a mission that mapped the surface of the planet using radar

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so we have these radar images that show us there are these huge volcanoes. This is Maat Mons.

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It's about 9km high.

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Hawaii, if we measured from the ocean floor, is similarly about 11km high.

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-So we're sitting on top of Earth's version of that.

-We're about here!

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'The surface of Venus is littered with volcanoes, but the key to understanding its fate

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'is not how many there are, but where they're located.

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'On Earth, volcanoes sit along the edges of tectonic plates,

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'the vast slabs of rock that drift across the surface of our planet.

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'But on Venus things are very different.'

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-So this is a map of the volcanoes on Venus.

-Well, you can see the little volcanoes poking out,

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almost evenly distributed around the planet. On Venus they're everywhere.

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Some of them are on these big hot spot areas, some out on the plains.

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There are hundreds and hundreds evenly distributed around the planet.

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So because there's no pattern of lines, we think Venus doesn't have plate tectonics?

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There are big tectonic features, but no plates.

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And it's this lack of tectonic plates on Venus that makes Earth and Venus so different.

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On Earth, the moving plates are driven by currents of molten rock beneath the surface

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making our world a dynamic and changing place.

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But Venus has no plates and no dynamic core

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and this one difference can mean life or death for a planet.

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And it's most obvious with one vital substance.

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Water makes our planet what it is - a place teeming with life in all its diversity.

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But because of the different way Venus works on the inside,

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water is one thing it couldn't keep.

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Venus used to be a much more comfortable place to live

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because billions of years ago it had liquid oceans.

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But it's 30% closer to the sun than we are and that made a crucial difference.

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Being that little bit warmer meant that a little bit more water evaporated from the ocean

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and that went into the atmosphere as water vapour.

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On its own, this wouldn't necessarily have spelt disaster for Venus,

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but this is where the two planets took different paths.

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The dynamic nature of the Earth's core helps generate a vital magnetic field.

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It's this field that shields us from the devastating solar wind

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that would otherwise strip our planet of its water.

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And this is what happened to Venus.

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With no magnetic field to protect it, its water was simply carried off into space.

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What I find amazing is that these two planets that had such similar beginnings, Earth and Venus,

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have ended up so differently.

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Earth has become this beautiful, diverse, living planet

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and Venus has become this horrible place, the evil twin.

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The surface of Venus is such an extreme environment

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that it's impossible to imagine any life forms surviving on it,

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but we also know that Venus wasn't always like this.

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It once had a much more temperate climate and it had oceans.

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So just like Earth it had all the vital ingredients for life

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and when life takes hold, it tends to hold on pretty tightly.

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So if life did once exist on Venus, is there a remote chance that it's still there today,

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hidden somewhere we just haven't thought to look?

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'This frozen, icy cave couldn't be more different to fiery, volcanic Venus.'

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Wow.

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'But hidden in this ice are clues that are challenging our most fundamental assumptions

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'about our evil twin.'

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The main reason I became a biologist

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is because I am constantly amazed by the beautiful, almost unbelievable complexity of life.

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And how it manages to find a foothold in the most improbable,

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challenging environments.

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And it's by studying these hidden oases at the outermost edges of our living world

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that we can understand more about how life persists,

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both on this planet but also throughout the universe.

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And it's by studying extreme environments like this

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that scientists like Birgit Sattler are rewriting the story of where life can be found,

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even on places like Venus.

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Birgit, what are we looking for down here, 30 metres below the surface?

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It's dark, it's cold, just frozen, but if you melt this ice up

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you will see millions of bacteria just dwelling in this environment.

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You can even shine them up. If we do a digital evaluation,

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we can actually detect the photosynthetic active pigments.

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It's pitch dark normally without the lights and there is still photosynthesis possible.

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The microbes thriving here show how life can survive in extreme conditions.

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'But to understand Venus we have to hunt for life in an even more distant part of our planet.

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'And to find it, we have to go up there.

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'In one of these.'

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That's as secure as it gets.

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Oh, sweet Jesus! Butterflies!

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-It's quite speedy.

-Mm-hm.

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And windy!

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I was told it was a cable car. It's more like a crate,

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-supported by metal bars.

-Yeah.

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-Has this ever had an MOT?

-What is an MOT?

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Ooh. The angle's changing. Is this the 45 angle...? Oh!

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Ooh! I didn't like that.

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Wow. That's... That was amazing!

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'We've come to the top of one of Austria's highest peaks to look for life.

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'We're not looking on the ground, but high up in the clouds.'

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Some nice clouds surrounding us.

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Yeah, even if we don't see here obvious clouds, there are lots of microbes, viruses, algae spores,

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fungi floating around. So anything that is floating in the atmosphere we want to catch.

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'We've known for a while that microbes exist in the Earth's clouds

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'but we thought they were just blown up there. We didn't think clouds could permanently sustain life.'

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We attach it to here.

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'But we're here to prove otherwise.'

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This lovely cloud right there is perfect.

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-All right?

-Oh!

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So this machine is going to be collecting microbes for a couple of hours now. It's straightforward.

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But the key thing here is to be able to prove that the microbes can actively reproduce

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and survive up there without the need to get back down to Earth.

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And if we can find evidence that life is replicating in these clouds,

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it doesn't only tell us something about life here on Earth,

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it may also have implications for Venus.

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Birgit, Venus is a super-hot, choked greenhouse planet.

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We've sent probes there, they've burnt to a crisp.

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We concluded there could not be life on that planet.

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What does your research here have to do with Venus?

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You can actually find one layer in the atmosphere where it's actually habitable

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with warm temperatures, but not too hot. We have moisture.

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So if you're able to prove that life can reproduce and live happily in the clouds up there,

0:30:090:30:14

we can dare to think that it might be possible in this particular cloud layer of Venus? Is it that simple?

0:30:140:30:20

It's not that simple, but why not? We have to go step by step.

0:30:200:30:25

If we see life is possible here, why shouldn't it be possible in a warmer environment?

0:30:250:30:30

Life in Venus's clouds might seem inconceivable.

0:30:340:30:38

As well as being very hot, they are also very acidic.

0:30:380:30:42

But evidence here on Earth has shown us that life can adapt to highly toxic conditions,

0:30:420:30:48

so if Birgit can prove life can live in Earth's clouds,

0:30:480:30:53

maybe we were wrong to write Venus off so quickly.

0:30:530:30:57

In the lab, the cloud samples are offered DNA which carries a radioactive marker.

0:31:050:31:11

If the DNA is taken up, it's proof replication is taking place.

0:31:110:31:16

Well, I'm looking here at a sample from the cloud layer which we brought to the lab

0:31:190:31:24

and we fixed the sample to get a snapshot of the condition of the cells,

0:31:240:31:30

and this is very surprising, but I can see one dividing cell.

0:31:300:31:34

-OK, where am I looking?

-If you go to the right side,

0:31:340:31:37

so approximately to five o'clock on this slide, you can see it -

0:31:370:31:41

-two tiny cells being very tightly together.

-My gosh! Yeah, yeah, yeah.

0:31:410:31:45

-Right?

-Oh, yeah.

-Two tiny cells.

-It's tiny.

-Very tightly together.

0:31:450:31:50

-Yeah, it's really tiny.

-That is cell replication?

-That's replication, yes.

0:31:500:31:55

-That's incredible.

-Yeah.

0:31:550:31:58

What about the radioactive basis, the new DNA strands? Have you got any results for that?

0:31:580:32:03

This is the outcome of the reaction 24 hours later.

0:32:030:32:06

What just looks like dry numbers is actually the proof that the radioactivity is inside the cells,

0:32:060:32:13

so it must have been taken up actively.

0:32:130:32:16

Absolute proof that replication is going on in the micro-organisms that we sampled from that cloud?

0:32:160:32:23

-Right.

-That's huge, Birgit.

-That's the proof, yeah.

0:32:230:32:27

So when you first saw this data being crunched up by your computer, how did you feel?

0:32:270:32:33

I was just sitting in front of the machine, praying, "Please spit i out, please spit out higher numbers.

0:32:330:32:39

-And it did and it was so exciting. I just ran over and said, "I got it!

-To your colleagues?

-Yeah.

0:32:390:32:46

It's a wonderful thought that the clouds we thought were hiding Venus's true identity

0:32:500:32:56

may be the one place where life exists.

0:32:560:32:59

We already know that life on Earth can survive in hot, acidic conditions.

0:33:030:33:07

And now we know it can also survive in our clouds.

0:33:080:33:13

It's just incredible to think that life has managed to carve a niche out for itself

0:33:200:33:25

and thrive up there in the clouds and that we've only just found out about it.

0:33:250:33:31

But for me what's most fascinating is what this means for Venus.

0:33:350:33:41

We had completely written off the possibility that it could harbour life,

0:33:410:33:45

but all this latest evidence makes for a pretty compelling case.

0:33:450:33:49

Right now, Venus is hurtling through space at over 78,000 miles per hour,

0:33:550:34:01

nearing the perfect position for its transit with our sun.

0:34:010:34:05

And it's already incredible how much we've learnt about our solar system from this one planet,

0:34:050:34:11

but this year, scientists are hoping that the transit will do even more.

0:34:110:34:17

As well as hunting for life in our own planetary neighbourhood,

0:34:190:34:23

they will also be turning their attention to the realm of much more distant stars...

0:34:230:34:27

..using the transit to hunt for alien life

0:34:280:34:32

and possibly even intelligent life.

0:34:320:34:35

But what hampers this search is the sheer vastness of space.

0:34:350:34:40

To understand the problem,

0:34:400:34:42

we need to get a sense of scale,

0:34:420:34:45

so there's our sun, the Earth and Venus,

0:34:450:34:49

and as we now know thanks to the transit,

0:34:490:34:51

the distance between us and the sun is 93 million miles.

0:34:510:34:56

Now, that might seem like a lot,

0:35:010:35:03

but the distance to the outermost regions of our solar system

0:35:030:35:07

is something like a thousand times that.

0:35:070:35:10

It took the spacecraft Voyager 34 years to even get close to it.

0:35:100:35:14

But then, the distance to our nearest star, Proxima Centauri, is over four light years away.

0:35:230:35:29

It would take Voyager 70,000 years to reach it.

0:35:290:35:33

And it's just the first of the 200 billion stars that make up our own galaxy, the Milky Way...

0:35:410:35:48

..which is just one of billions of galaxies that are millions of light years apart.

0:35:510:35:57

So how do you go about hunting for life on planets hundreds of light years away?

0:36:020:36:08

Once again, the transit is showing us the way.

0:36:080:36:12

FAINT WHIZZING SOUNDS

0:36:120:36:14

When I come to a place like this,

0:36:320:36:35

I get a sense of how small I am against the vastness of this landscape.

0:36:350:36:40

But it all pales into insignificance when I look up into space.

0:36:440:36:48

I'm utterly overwhelmed by the magnitude of the universe out there.

0:36:480:36:53

And I don't know about you,

0:36:530:36:55

but a little part of me always wonders, "Are we really alone?"

0:36:550:36:59

It's one of the most important questions to ask,

0:37:040:37:07

but one of the hardest to answer.

0:37:070:37:09

In recent years, we really seem to be coming to one of those points in history where things are changing

0:37:110:37:17

just like when Kepler and Halley worked out the size of the solar system.

0:37:170:37:22

But I really think we're closer than ever before to finding some answers.

0:37:230:37:28

I've come to Nevada far away from the bright lights.

0:37:340:37:38

It's the stargazing capital of the world.

0:37:380:37:41

You can't come to a place like this

0:37:470:37:50

and not be bowled over by the stars.

0:37:500:37:53

They are simply breathtaking.

0:37:530:37:56

And look, there's Venus, the brightest light in the sky,

0:37:570:38:01

and for me, a shining example of how far we've come in everything we've achieved.

0:38:010:38:05

But Venus is just a small planet that's relatively close to us.

0:38:100:38:14

In this patch of sky alone, there ar literally millions of stars.

0:38:140:38:19

So when it comes to looking for life out there, just where do we look?

0:38:220:38:27

Searching for stars is all very well

0:38:320:38:34

In the right conditions, they're easy to find.

0:38:340:38:38

But if we want to look for life, we have to search for planets.

0:38:380:38:42

And not just any planets. The right kind of planets.

0:38:420:38:46

Probably a planet very much like Earth - rocky, rather than a gas giant like Jupiter

0:38:460:38:52

But not only that, the planet has to be just the right distance from the star.

0:38:520:38:57

Not too far away...

0:38:570:38:59

..and also not too close to the parent star.

0:39:010:39:05

It needs to be just the right distance, so that liquid water can exist on the surface,

0:39:050:39:11

a habitable exoplanet.

0:39:110:39:13

The problem with finding these exoplanets is they are lost in the glare of the stars they orbit

0:39:160:39:23

So finding them is like looking for a flea crawling across a car headlight...

0:39:280:39:33

..from a mile away.

0:39:340:39:37

'Five, four,

0:39:400:39:43

'three, two...

0:39:430:39:45

'Engine start, one, zero, and lift-off for the Delta II rocket with Kepler

0:39:450:39:50

'on a search for planets.'

0:39:500:39:52

But recently, we've had a new tool to help us, a telescope in space - Kepler.

0:39:530:39:58

When a planet crosses between us and its star,

0:40:010:40:04

the light from the star dips by a fraction of a percent.

0:40:040:40:08

And it's by measuring this dimming that Kepler tracks down planets.

0:40:120:40:17

Kepler carries a photometer on board

0:40:190:40:22

that measures this tiny dip in light and it sends back a signal.

0:40:220:40:27

Now, it's not a picture or a message from the aliens.

0:40:270:40:31

It's this - a light curve.

0:40:310:40:33

And this may not look like very much

0:40:340:40:37

but this dip can tell us a lot about the planet that is in orbit around the star,

0:40:370:40:42

for example, how long it takes to orbit and what size the planet is

0:40:420:40:46

And using data like this, we can even work out the key question -

0:40:460:40:51

is the planet in the star's habitable zone?

0:40:510:40:54

In the last four years alone, Kepler has discovered 61 new planets

0:40:560:41:02

and there are more than 2,000 others awaiting confirmation.

0:41:020:41:08

Such a rapid rate of discovery makes this one of the most exciting fields of exploration today.

0:41:100:41:17

And these new techniques are not onl helping our search for planets.

0:41:200:41:25

They are also helping us hunt for ET

0:41:260:41:29

I've always wanted to come here to this eerie place.

0:41:540:41:58

These telescopes are very famous, but they're not telescopes that are looking.

0:41:580:42:03

They're telescopes that are listenin and they're listening out for any sign at all of a message from ET

0:42:030:42:09

a bit like an interplanetary telephone exchange.

0:42:090:42:13

This is the Allen Telescope Array, home to the SETI Institute,

0:42:230:42:28

a group of scientists who have dedicated their careers to searching for extra-terrestrial intelligence.

0:42:280:42:35

And leading the search is Dr Seth Shostak.

0:42:390:42:43

How do these telescopes actually go about getting data for you?

0:42:450:42:49

In principle, all you do is aim all these antennas in the direction

0:42:490:42:53

of some star system that, for one reason or another,

0:42:530:42:56

maybe just because it's a close star or a star known to have planets,

0:42:560:43:00

you think, "That might be a habitat for ET,"

0:43:000:43:02

then you just search over a wide range of the radio dial, looking for a signal at one spot on the dial.

0:43:020:43:09

It is a big universe out there. In our galaxy alone, there's 100 billion stars.

0:43:090:43:13

-How do you focus your search?

-We tend to look at star systems that are like the sun

0:43:130:43:19

because we know that a star system like the sun can have planets where you get intelligent life.

0:43:190:43:24

-We're here.

-We're here. We also tend to pick nearby star systems if we can as the signals would be stronger

0:43:240:43:30

and if you found something, it would be more interesting

0:43:300:43:33

to find nearby neighbours than somebody 5,000 light years away.

0:43:330:43:37

NASA's Kepler mission is now studying 150,000 stars, looking for planetary transits.

0:43:370:43:43

How has that technique helped your search?

0:43:430:43:46

One of the problems we had was that we're aiming these antennas towards the south

0:43:460:43:50

on the assumption that whatever star we're aimed at has a signal coming our way

0:43:500:43:55

that's arriving just at the right time, so it gets picked up.

0:43:550:43:58

It's like two cowboys aiming their pistols at one another and having the bullets meet in the middle.

0:43:580:44:03

-Across the vastness of the sky.

-I mean, it's not very likely.

0:44:030:44:07

But transits, the transit of the Earth in front of the sun,

0:44:070:44:11

as seen by ET, gives them a clock and they might be clever enough to say,

0:44:110:44:16

"Wait, what we'll do is broadcast a signal that gets to Earth just as it's transiting the sun."

0:44:160:44:21

OK? That way, they'll know where to look when, so the bullets have a chance of meeting.

0:44:210:44:27

This is where all the action happens, there is where the signals from the telescopes are brought in,

0:44:390:44:45

20 million channels a second being analysed. Tell me what happens here.

0:44:450:44:49

There's a whole room full of electronics and fibre optics and other hi-tech stuff.

0:44:490:44:54

And all the signals from all the antennas go in there.

0:44:540:44:57

They're sliced and diced and sampled

0:44:570:45:00

and, you know, some part of them is then sent to be analysed for signals.

0:45:000:45:05

What would the signal have to be lik to get you out of bed at three in the morning?

0:45:050:45:09

Nobody would call me unless the signal had the characteristics required to get me out of bed,

0:45:090:45:14

but it would have to be a very clean-looking signal,

0:45:140:45:17

a very narrow band and drifting at a rate that looks like it's not a transmitter here on Earth.

0:45:170:45:22

ET, yeah, I'll get out of bed!

0:45:220:45:25

It's utterly incredible to think that these images,

0:45:250:45:28

which amount to really nothing more than noise and fluff on the screen,

0:45:280:45:33

could ultimately be the first tantalising glimpse that we get of life elsewhere?

0:45:330:45:38

Yes, it doesn't look very dramatic, but that's the nature of discovery science and that's what we're doing.

0:45:380:45:44

A little plot like this with just a little wiggly, scraggly bit of brightening across it,

0:45:440:45:49

that's the clue that would tell us that there's somebody out there.

0:45:490:45:54

Seth's pretty bullish about his chances of finding ET

0:46:020:46:06

and actually, I think he's got reall good reason to think that way.

0:46:060:46:10

Kepler and the science that's coming out of the planetary transits

0:46:100:46:14

is really reviving and giving focus to his search.

0:46:140:46:17

If I was new to science today, I would very much want to go into this area.

0:46:170:46:22

There's so much data being collected about these planets

0:46:220:46:25

and we're learning so much about their size and suitability for life.

0:46:250:46:30

And I think that in the coming years we will find what we're looking for.

0:46:300:46:34

Transits have been crucial in helping us track down Earth-like planets.

0:46:390:46:45

But to find out if they sustain life,

0:46:470:46:51

we need to take the next step.

0:46:510:46:53

We need to get closer to these planets than ever before.

0:46:540:46:58

Close enough to peer inside their atmospheres.

0:46:590:47:03

To get a peek at the atmospheres of these distant planets,

0:47:100:47:14

I'm travelling as far out of our own atmosphere as I can get.

0:47:140:47:18

This is a bit of a bumpy drive,

0:47:210:47:23

but we're on the way to a really exciting place.

0:47:230:47:27

We're going to Mauna Kea,

0:47:270:47:29

one of the most famous observatories in the world.

0:47:290:47:32

It's also very, very remote.

0:47:320:47:35

I feel like I'm on top of the world

0:47:590:48:01

and I'm not far off.

0:48:010:48:04

There's very little air up here, compared with down on the ground.

0:48:050:48:09

I can feel it's quite hard to breathe.

0:48:100:48:13

All the weather, the turbulence down there,

0:48:180:48:22

all of that is underneath,

0:48:220:48:25

and that's why all these telescopes are here.

0:48:250:48:28

So this is an amazing place to come to get away from the Earth.

0:48:290:48:34

It's like a step on the way to the sky.

0:48:340:48:37

It's getting really cold here. The sun has just gone down.

0:48:550:49:01

But the telescopes are waking up.

0:49:010:49:03

There's a stunning sunset and we can still just see all the telescope flaps opening.

0:49:030:49:10

So as the view of the land fades away,

0:49:150:49:18

the sky is opening up and I can see Venus up there with my eyes.

0:49:180:49:22

But beyond Venus are billions of planets we can't even see,

0:49:270:49:32

and yet using these telescopes, scientists have developed an exciting new technique

0:49:320:49:37

to find planets with atmospheres that could support life.

0:49:370:49:41

And the most recent focus of their search is a new class of planets only slightly larger than our own -

0:49:410:49:48

super-Earths.

0:49:480:49:50

Now, all of these planets are just so far away. How do you study an atmosphere that's that far away?

0:49:500:49:56

When they pass in front of the star,

0:49:560:49:58

something very special happens.

0:49:580:50:00

The light from the star shines through the planet's atmosphere.

0:50:000:50:05

And as it does so, the light is absorbed at different colours by molecules

0:50:050:50:11

and each molecule has a unique fingerprint.

0:50:110:50:14

What are the chemicals that you're looking for?

0:50:140:50:17

The one that we're using as a key diagnostic right now is methane.

0:50:170:50:21

Here on Earth, of course, methane is connected to life processes.

0:50:210:50:25

We're really looking for life changing the atmosphere

0:50:250:50:29

in a way which can't be explained by any other process.

0:50:290:50:33

So you collect this data using this enormous thing here. How does that work?

0:50:330:50:38

This is the NASA Infrared Telescope Facility, a really marvellous telescope.

0:50:380:50:43

And the instrument my team uses a lo is the SPECS instrument back here, this blue one.

0:50:430:50:49

It works just like a prism. It break light apart into all these different colours, but mainly in the infrared.

0:50:490:50:55

And what's the most recent thing you've been working on?

0:50:550:50:59

This is a well-known super-Earth, GJ 1214b,

0:50:590:51:02

and what you're seeing right here is a preliminary spectrum

0:51:020:51:06

that our team obtained here at the IRTF with SPECS.

0:51:060:51:09

This is the feature we're out to try to confirm.

0:51:090:51:13

But how long are we going to have to wait until we can really look inside a planet's atmosphere

0:51:130:51:18

and answer the question about whether there's life there?

0:51:180:51:22

That's a question I think we will get to over probably the next 10 to 15 years.

0:51:220:51:27

Within my professional life, I expec we will have answered it, but there is still a lot of work to do.

0:51:270:51:32

I find the measurements that they're making here absolutely astonishing.

0:51:430:51:47

The subtlety required to detect an atmosphere from this far away is just amazing.

0:51:470:51:54

Science fiction writers have been inventing crazy planets for decades

0:51:550:52:00

and now we know they really exist.

0:52:000:52:03

And it makes the sky for me a completely different place.

0:52:030:52:07

Studying the atmospheres of distant, transiting planets

0:52:140:52:18

is some of the most exciting science happening today.

0:52:180:52:22

But precision is everything and to be as accurate as possible,

0:52:220:52:26

we need to know if we're doing things right.

0:52:260:52:29

And that's what's happening tonight with one very special telescope 350 miles above us -

0:52:310:52:38

Hubble.

0:52:380:52:39

So what are you hoping to achieve with tonight's transit and Hubble's observation of it?

0:52:410:52:47

We hope to retrieve the atmospheric signal from Venus

0:52:470:52:51

and to do that, we will observe the transit of Venus with a spectrograph

0:52:510:52:56

So a spectrum looks something like this.

0:52:560:52:59

It basically tells you what's inside the atmosphere of the object you are studying.

0:52:590:53:05

But we already know the atmospheric composition of Venus, so why are you doing this?

0:53:050:53:10

Well, the idea is really to be able to test our technique to study the atmosphere of exoplanets.

0:53:100:53:18

We want to use Venus as a template, as a model.

0:53:180:53:22

So, basically, you're testing that your method is correct

0:53:220:53:26

and if it correctly splits up all the components of Venus's atmosphere,

0:53:260:53:30

you can then apply it to exoplanets far away that we haven't analysed yet?

0:53:300:53:35

Yeah, with much more confidence than we would have without doing this experiment.

0:53:350:53:41

But it's not quite as simple as just focusing the Hubble telescope on the transit, is it?

0:53:410:53:46

No, actually, it's forbidden to point Hubble to the sun because it could damage the instruments,

0:53:460:53:53

so we are going to use a trick which is pointing at the moon.

0:53:530:53:57

In other words, we are going to use the moon as a giant mirror.

0:53:570:54:01

It just seems like such a huge undertaking

0:54:010:54:04

and there's only one chance in your lifetime to get it right.

0:54:040:54:08

This is a unique opportunity to record the transit of Venus with Hubble.

0:54:080:54:14

-Does that make you a little bit nervous about getting it right?

-More than a little bit.

-Really?

0:54:140:54:19

From the first transits we witnessed

0:54:220:54:26

to the one that's happening tonight,

0:54:260:54:28

the transit of Venus has transformed our understanding

0:54:280:54:33

of the vast universe we belong to.

0:54:330:54:36

It's given us the size of our own solar system

0:54:380:54:42

and now it's helping us to take giant leaps into distant space

0:54:420:54:47

in our search for life.

0:54:470:54:50

It's meant so much to so many people

0:54:520:54:56

and tonight is no exception.

0:54:560:54:59

I'm going to watch it with my kids.

0:54:590:55:01

This is kind of a way I get to share with them a little bit of what I do and the excitement of astronomy.

0:55:010:55:08

I'm excited to be going to Svalbard.

0:55:080:55:10

I'll meet the Venus Express team there and we'll see the transit together.

0:55:100:55:14

Hopefully, somewhere up on the mountains for the best view.

0:55:140:55:17

During the transit, I might actually be in bed trying to get some sleep

0:55:170:55:22

because the real work for me starts after it.

0:55:220:55:26

During the next transit of Venus, I'll get some of my colleagues together, we'll have a big party,

0:55:260:55:31

haul out our telescope, put a solar filter on it and watch Venus pass across the sun.

0:55:310:55:36

After all, we won't be around the next time this happens.

0:55:360:55:39

And if you want to enjoy this spectacle safely,

0:55:430:55:47

you don't even need a telescope. It's something everyone can share.

0:55:470:55:51

Now, there are lots of ways in which you can take part,

0:55:510:55:55

but there's one thing that you must keep in mind and that's never look at the sun directly.

0:55:550:56:01

It gives out a lot of light and heat that would damage your eyes without you even realising.

0:56:010:56:06

By far the simplest way to view the transit is by using a filter,

0:56:090:56:14

so, for example, one of these, and they're extremely easy to use.

0:56:140:56:19

All you have to do is put them up in front of your eyes and then turn to look at the sun. Let's give it a go.

0:56:190:56:26

Wow! What does it look like to you?

0:56:280:56:30

Green.

0:56:300:56:32

Green?

0:56:320:56:34

Now, Venus is only one-thirtieth of the size of the sun,

0:56:340:56:39

so you'll have to have pretty keen eyes to see the transit.

0:56:390:56:42

-Do you think you'll be able to see Venus?

-Yeah.

-You'll give it a go?

0:56:420:56:46

If you want to project an image of the sun that's bigger, you can us a telescope like this one

0:56:480:56:53

and you should never look through the eyepiece.

0:56:530:56:56

Instead, project the image of the su on to the card like we have here.

0:56:560:57:01

Hold it just underneath the telescop and what can you see on here?

0:57:010:57:05

I can see quite a lot of sunspots and there's quite a large one.

0:57:050:57:08

-This one is massive.

-Yes.

-Using this kind of technique makes the sun much, much bigger.

0:57:080:57:14

-Do you think you'll be viewing the transit?

-Yeah. It's going to be exciting.

0:57:140:57:19

-SHE LAUGHS

-Yeah.

0:57:310:57:33

-Absolutely beautiful.

-Yeah.

0:57:330:57:36

I look at the moon quite a lot through binoculars.

0:57:370:57:40

You're a bit of a pro at this, aren't you?

0:57:400:57:43

Wherever you're watching it,

0:57:440:57:46

this is going to be a spectacular event.

0:57:460:57:49

There's just over an hour to go before Venus makes its first contact with the outer edge of our star.

0:57:490:57:55

And I absolutely cannot wait to find out what this transit teaches us about our incredible universe.

0:57:550:58:02

And since this is the last transit of Venus until 2117, make the most of it.

0:58:020:58:07

Be a part of this rare moment in history.

0:58:070:58:11

And remember, the next time you look up at the morning star,

0:58:110:58:15

just take a moment to consider how remarkable it is.

0:58:150:58:20

# I'm wishing on a star

0:58:290:58:33

# To follow where you are

0:58:330:58:37

# I'm wishing on a dream

0:58:400:58:44

# To follow what it means

0:58:450:58:49

# To follow where you are... #

0:58:510:58:53

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