0:00:02 > 0:00:0590 million miles from us
0:00:05 > 0:00:07is the power that shapes our world.
0:00:10 > 0:00:12Our very own star.
0:00:13 > 0:00:14The sun.
0:00:16 > 0:00:18We see it shine in the sky above us.
0:00:20 > 0:00:24But beyond our sight, something dramatic is happening.
0:00:26 > 0:00:29The sun is going into overdrive.
0:00:37 > 0:00:39Our star is more active now
0:00:39 > 0:00:41than it's been for a decade.
0:00:44 > 0:00:48It's sending eruptions of superheated plasma
0:00:48 > 0:00:52and vast waves of radiation towards our planet,
0:00:52 > 0:00:55with the potential to disrupt our lives
0:00:55 > 0:00:58in completely unexpected ways.
0:01:00 > 0:01:03At the same time, a new generation of satellites
0:01:03 > 0:01:08is showing us the sun in more detail than ever before.
0:01:08 > 0:01:11It's almost pulsating.
0:01:11 > 0:01:14I'm Kate Humble.
0:01:14 > 0:01:16And I'm Helen Czerski.
0:01:16 > 0:01:20Together, we're going to unravel what's happening to our sun.
0:01:21 > 0:01:25From Britain's leading centre for solar research,
0:01:25 > 0:01:31we'll use the latest satellite images and a team of world-class experts
0:01:31 > 0:01:33to decode the sun's inner workings.
0:01:33 > 0:01:35Something in the sun's atmosphere snapped.
0:01:37 > 0:01:41We'll explore the sun's most spectacular displays.
0:01:41 > 0:01:44I love your laboratory, it's brilliant!
0:01:44 > 0:01:48Investigate its mysterious cycles of activity.
0:01:48 > 0:01:52- So it took seconds to get from the sun to the satellite.- That's right.
0:01:52 > 0:01:56And discover how our sun is behaving right now.
0:02:10 > 0:02:1470 miles west of London lies Britain's answer to NASA.
0:02:17 > 0:02:21This is the Rutherford Appleton Laboratory in Oxfordshire.
0:02:24 > 0:02:28At RAL, satellite instruments are designed and tested
0:02:28 > 0:02:30before they're launched into space.
0:02:31 > 0:02:35And scientists are analysing the latest information
0:02:35 > 0:02:38these satellites beam down around the clock.
0:02:41 > 0:02:43It's one of the most important
0:02:43 > 0:02:45centres of solar research in the world.
0:02:48 > 0:02:53We've set up inside one of RAL's giant research facilities
0:02:53 > 0:02:58so that we can talk to some of Britain's leading solar scientists
0:02:58 > 0:02:59and see for ourselves
0:02:59 > 0:03:03the extraordinary images they're using to study our star.
0:03:07 > 0:03:11We can't look directly at the sun without damaging our eyesight,
0:03:11 > 0:03:15but a new fleet of satellites are allowing scientists here at RAL
0:03:15 > 0:03:19for the first time to get a unique picture of the sun.
0:03:23 > 0:03:28In 2006, NASA launched the twin STEREO spacecraft
0:03:28 > 0:03:32to observe the sun from two sides simultaneously.
0:03:34 > 0:03:39The Solar Dynamics Observatory followed four years later.
0:03:39 > 0:03:44It's able to visualise the sun in high resolution for the first time.
0:03:48 > 0:03:50These satellites show the sun
0:03:50 > 0:03:54as far more than simply the burning disc in the sky that we see.
0:03:58 > 0:04:03Here at RAL, head of space science Richard Harrison
0:04:03 > 0:04:07is responsible for analysing those images.
0:04:07 > 0:04:08So, Richard,
0:04:08 > 0:04:12how are these new satellites advancing our knowledge of the sun?
0:04:12 > 0:04:15Well, the whole point is that we have now built up
0:04:15 > 0:04:18a fleet of spacecraft, an international fleet of spacecraft,
0:04:18 > 0:04:21that are really studying the sun in phenomenal detail.
0:04:21 > 0:04:22We can see the sun from both sides.
0:04:22 > 0:04:26We can see a complete star, and we'd never done that before.
0:04:28 > 0:04:32And these satellites can detect types of light from the sun
0:04:32 > 0:04:35that are invisible to the naked eye.
0:04:35 > 0:04:38The brighter regions here are what we call active regions,
0:04:38 > 0:04:41and they're regions a bit like volcanoes and earthquakes
0:04:41 > 0:04:44on the Earth, if you like, regions where the sun is active,
0:04:44 > 0:04:46and there's a lot of interesting stuff happening in here.
0:04:46 > 0:04:48You can see it with your own eyes, it's so complex,
0:04:48 > 0:04:51it's moving all the time, like a plate of writhing spaghetti.
0:04:51 > 0:04:54And I mean, this is an extraordinary image.
0:04:54 > 0:04:56We can see several colours put together,
0:04:56 > 0:04:59showing you the full complexity in all of its glory, if you like,
0:04:59 > 0:05:03the truly complex atmosphere writhing in front of your eyes.
0:05:03 > 0:05:06And this sort of illustrates it, puts it in a nutshell,
0:05:06 > 0:05:08how fantastic it is to be studying the sun
0:05:08 > 0:05:10as it approaches a peak in activity
0:05:10 > 0:05:12with this wonderful fleet of spacecraft.
0:05:15 > 0:05:20This peak in activity is known as a solar maximum.
0:05:21 > 0:05:22It's the high point in a cycle
0:05:22 > 0:05:26the sun goes through on average every 11 years.
0:05:27 > 0:05:28From relative calm...
0:05:31 > 0:05:33..to intense activity...
0:05:36 > 0:05:37..and back again.
0:05:37 > 0:05:41A cycle that's fundamental to how the sun works.
0:05:43 > 0:05:45Understanding this solar cycle
0:05:45 > 0:05:49will help us discover the secret life of the sun.
0:05:51 > 0:05:53But for most of us on Earth,
0:05:53 > 0:05:57the sun is something we rarely examine in any sort of detail.
0:05:57 > 0:06:00To begin to understand its extraordinary power
0:06:00 > 0:06:03and its changing cycles of activity, we need the help
0:06:03 > 0:06:07of one of the most dramatic events in the astronomical calendar,
0:06:07 > 0:06:09a total solar eclipse.
0:06:11 > 0:06:15And to see that, I had to travel to the other side of the world.
0:06:23 > 0:06:25November 2012.
0:06:25 > 0:06:27I've come to Cairns, Australia.
0:06:29 > 0:06:31I'm joining people from across the globe
0:06:31 > 0:06:35because in 48 hours, there's going to be a total eclipse.
0:06:37 > 0:06:38But this one is special
0:06:38 > 0:06:43because it promises to reveal something crucial about our sun.
0:06:44 > 0:06:48Cairns is a relatively small town in Australian terms.
0:06:48 > 0:06:51It's home to about 130,000 people.
0:06:51 > 0:06:55But that number could swell by as much as 50,000
0:06:55 > 0:06:58in the next couple of days, and all for an event
0:06:58 > 0:07:01that's going to last just two minutes and two seconds.
0:07:06 > 0:07:09It's an emotional experience, it's a lovely way to sort of see the world.
0:07:09 > 0:07:13Everyone is happy. It's fanta... It's a natural spectacle of science.
0:07:13 > 0:07:15I'm getting excited, yeah!
0:07:15 > 0:07:16I've never seen a total eclipse before
0:07:16 > 0:07:19and we've got our glasses, and we're all set to go.
0:07:19 > 0:07:22We've got our fingers crossed for clear skies.
0:07:22 > 0:07:25You can't safely view an eclipse
0:07:25 > 0:07:28unless you have glasses with powerful filters.
0:07:28 > 0:07:29- Hi.- Hello.
0:07:29 > 0:07:31- That's what I'm after. - The very last pair.
0:07:31 > 0:07:33- No way!- Three dollars.
0:07:33 > 0:07:36- Did you want some as well?- Oh, yeah, we've been searching everywhere!
0:07:36 > 0:07:39- This is the very last pair in Cairns. - I'm really sorry.
0:07:39 > 0:07:42- Oh, you're joking! - We could share them.
0:07:42 > 0:07:46Don't film this. This is horrible. This is like breaking my heart!
0:07:46 > 0:07:47No...
0:07:47 > 0:07:50It's once every 50 years or so, so make the most of it.
0:07:50 > 0:07:52- Thank you very much.- Thanks, bye!
0:07:54 > 0:07:58- Seriously, your last pair? - Last pair. No more, all gone!
0:08:06 > 0:08:10To get an eclipse, the moon must drift between the sun and us.
0:08:10 > 0:08:16At what's called first contact, the moon begins to block it.
0:08:16 > 0:08:17But what's extraordinary
0:08:17 > 0:08:21is what happens when the sun is completely covered.
0:08:21 > 0:08:24That moment of totality
0:08:24 > 0:08:28reveals something that's normally hidden by the sun's glare -
0:08:28 > 0:08:31the sun's faint atmosphere, the corona.
0:08:33 > 0:08:37And it's the corona that's key to what this eclipse can tell us.
0:08:39 > 0:08:44The corona is due to reveal itself at precisely 6.38 in the morning
0:08:44 > 0:08:46the day after tomorrow.
0:08:51 > 0:08:55But the fact that we get total eclipses in the first place
0:08:55 > 0:08:58is thanks to an astonishing coincidence.
0:09:00 > 0:09:02Earth is the only planet in the solar system
0:09:02 > 0:09:05from where you can witness a total eclipse,
0:09:05 > 0:09:08and the reason for that is down to pure luck.
0:09:08 > 0:09:12The moon is 400 times smaller than the sun.
0:09:12 > 0:09:16But it's also 400 times closer to the Earth.
0:09:16 > 0:09:21So when the moon's orbit brings it between the Earth and the sun,
0:09:21 > 0:09:25it appears to be exactly the same size as the sun,
0:09:25 > 0:09:29and it's able to block out its entire surface from our view.
0:09:32 > 0:09:35There's a total eclipse on average every 18 months,
0:09:35 > 0:09:38so they're not exactly rare.
0:09:38 > 0:09:41But catching one isn't easy.
0:09:42 > 0:09:46The narrow shadow paths they trace on the Earth's surface
0:09:46 > 0:09:49are far more likely to pass over uninhabited regions,
0:09:49 > 0:09:54such as the oceans, than a populated area like Cairns.
0:09:58 > 0:10:02And the timing of this eclipse is significant.
0:10:05 > 0:10:08Right now, we're due to be at solar maximum,
0:10:08 > 0:10:12the period of greatest activity in the sun's cycle.
0:10:13 > 0:10:16But each maximum is slightly different,
0:10:16 > 0:10:20so scientists need to confirm that we have actually reached it.
0:10:24 > 0:10:29One way to do that is to study the sun's corona during totality.
0:10:29 > 0:10:31Click on that.
0:10:31 > 0:10:34'And that's what makes this eclipse especially exciting.'
0:10:34 > 0:10:36Delivery!
0:10:38 > 0:10:40Jay...I think we've got the box you wanted.
0:10:40 > 0:10:44'Even to the most hardened eclipse chasers.
0:10:46 > 0:10:51'Astronomer Francisco Diego has seen 17 total eclipses.
0:10:51 > 0:10:57'This time, he's advising a group of a hundred British eclipse chasers.
0:10:57 > 0:11:00'But he's also brought his own equipment.'
0:11:00 > 0:11:02The sun, as far as it is...
0:11:02 > 0:11:05You're not the most hi-tech scientist I know!
0:11:05 > 0:11:08This is an ideal container for a very delicate part of equipment.
0:11:08 > 0:11:11You're like a Blue Peter scientist, it's brilliant!
0:11:11 > 0:11:13- Can you hold this for me? Careful with the wind.- I've got it, yeah.
0:11:13 > 0:11:16'A camera and some home-made filters
0:11:16 > 0:11:20'are all he needs to take detailed photographs of the corona.'
0:11:20 > 0:11:24So what I do, I remove the lens cap here...
0:11:24 > 0:11:27'And it's the shape of the corona in his photos
0:11:27 > 0:11:31'that will tell Francisco if we're at solar maximum.'
0:11:31 > 0:11:34So the eclipse gives that opportunity to admire
0:11:34 > 0:11:38and to study the outer layers of the solar atmosphere.
0:11:38 > 0:11:40These layers, the chromosphere and the corona,
0:11:40 > 0:11:43are an indication of solar activity.
0:11:43 > 0:11:45The shape of the solar corona is changing all the time.
0:11:45 > 0:11:48For example, when the corona is very round,
0:11:48 > 0:11:52that means the solar activity is at a maximum.
0:11:52 > 0:11:54Francisco will have only two minutes
0:11:54 > 0:11:59in which to get a successful picture of the corona.
0:11:59 > 0:12:00THUNDER RUMBLES
0:12:00 > 0:12:03But that brief window of opportunity
0:12:03 > 0:12:06is threatened by a more familiar force of nature.
0:12:06 > 0:12:08Cover the telescope!
0:12:12 > 0:12:14Oh, man!
0:12:15 > 0:12:17The eclipse is tomorrow morning
0:12:17 > 0:12:21and the forecast is not looking good.
0:12:23 > 0:12:27This is tropical Australia, we're going into the rainy season,
0:12:27 > 0:12:30and the weather could obliterate the old thing.
0:12:42 > 0:12:452am, the day of the eclipse.
0:12:45 > 0:12:48I'm following Francisco and his eclipse chasers
0:12:48 > 0:12:52inland from Cairns to get away from the rain clouds.
0:12:52 > 0:12:55We have to reach clear skies before dawn,
0:12:55 > 0:12:58or we'll miss the eclipse.
0:13:00 > 0:13:04We've pulled off...the road, finally.
0:13:04 > 0:13:06It's...ten past five.
0:13:07 > 0:13:12And the sky is lightening dramatically quickly.
0:13:13 > 0:13:18Sunrise is going to be... in about half an hour,
0:13:18 > 0:13:19and first contact...
0:13:19 > 0:13:21- Follow me, quick!- OK, OK.
0:13:22 > 0:13:25..and first contact is ten minutes after that.
0:13:29 > 0:13:32Wow!
0:13:32 > 0:13:34That's incredible.
0:13:34 > 0:13:37The sun has just made an appearance...
0:13:39 > 0:13:40..above the clouds...
0:13:42 > 0:13:44..and it's got a chunk
0:13:44 > 0:13:46out of the top left corner.
0:13:50 > 0:13:52The moon has begun to block the sun,
0:13:52 > 0:13:54but the sun is so bright
0:13:54 > 0:13:57that we won't notice any darkening of the daylight
0:13:57 > 0:14:00until it's almost completely covered.
0:14:02 > 0:14:05What do you think, Francisco? It's looking quite skinny now.
0:14:05 > 0:14:07It's quite skinny, yes, about ten minutes before totality,
0:14:07 > 0:14:10so this is where things are going to happen faster and faster.
0:14:10 > 0:14:14The darkness is going to really come much quicker.
0:14:15 > 0:14:18You... You feel it, it's physical.
0:14:20 > 0:14:23And it's sort of terrifying, actually!
0:14:23 > 0:14:25- HE CHUCKLES - Isn't it?- It is!
0:14:25 > 0:14:27I mean, just look at it. It's just...
0:14:27 > 0:14:30Every moment you can feel the light just dropping and dropping.
0:14:30 > 0:14:32It's like somebody's stealing the sun.
0:14:35 > 0:14:37And it's now just a tiny...
0:14:39 > 0:14:42- ..hair's breadth in the sky.- Yeah, two minutes, two minutes to go.
0:14:42 > 0:14:46And it's so cold, the temperature has just completely dropped.
0:14:48 > 0:14:51It's like everyone's collectively holding their breath.
0:15:03 > 0:15:04SHE GASPS
0:15:04 > 0:15:06Oh, my goodness!
0:15:06 > 0:15:07SHE LAUGHS
0:15:07 > 0:15:09OBSERVERS CHEER
0:15:09 > 0:15:11It's the most amazing thing!
0:15:11 > 0:15:13SHE LAUGHS
0:15:13 > 0:15:16I can't believe how beautiful it is!
0:15:16 > 0:15:18Oh, amazing!
0:15:19 > 0:15:23The moon has completely blocked the disc of the sun.
0:15:23 > 0:15:26A delicate halo is all that remains.
0:15:26 > 0:15:27It's the corona.
0:15:30 > 0:15:33Francisco now has two minutes and two seconds
0:15:33 > 0:15:36to get the photos he needs.
0:15:39 > 0:15:40Here it comes!
0:15:40 > 0:15:44CAMERA SHUTTER WHIRRS
0:15:51 > 0:15:53It's ridiculous! I...
0:15:53 > 0:15:55Isn't that amazing?
0:15:57 > 0:15:58Amazing.
0:16:05 > 0:16:07It was worth getting up at two o'clock in the morning.
0:16:07 > 0:16:08HE CHUCKLES
0:16:08 > 0:16:11Absolutely worth getting up at two o'clock in the morning!
0:16:14 > 0:16:20I challenge anyone to watch a total eclipse without being deeply moved.
0:16:20 > 0:16:23It's a glimpse into the hidden workings of the sun.
0:16:29 > 0:16:32It makes you kind of look at it in a slightly different way afterwards,
0:16:32 > 0:16:33- doesn't it?- Absolutely, yes.
0:16:33 > 0:16:37Somehow, you can't take it for granted any more.
0:16:37 > 0:16:41No, you cannot, and then... Well, life on Earth depends on it,
0:16:41 > 0:16:43has depended on it for billions of years, really.
0:16:44 > 0:16:48That was the first time I've ever seen a total eclipse.
0:16:50 > 0:16:52But what has the corona revealed?
0:16:52 > 0:16:57Has the sun reached solar maximum, its peak of activity?
0:17:03 > 0:17:08Back at RAL, we can now get the answer from Francisco's photographs.
0:17:09 > 0:17:11An eclipse is a fabulous thing to experience,
0:17:11 > 0:17:14but there was a scientific reason for taking those photographs.
0:17:14 > 0:17:18- So are we at solar maximum? - It looks like we are.
0:17:18 > 0:17:20We have pictures taken in solar minimum.
0:17:20 > 0:17:24For example, this one, that was taken in 1994, two cycles ago,
0:17:24 > 0:17:26when the solar activity was at a minimum.
0:17:26 > 0:17:29- Can you see an axis here? - Really clear, isn't it?
0:17:29 > 0:17:32Yeah, the sun is very orderly, very steady, very quiet.
0:17:32 > 0:17:36- There's a very clear pattern. - By contrast, last year in Australia
0:17:36 > 0:17:38we saw the corona in a completely different way.
0:17:38 > 0:17:41This is the picture we took there. Now, tell me where is the axis.
0:17:41 > 0:17:44It's just the same all the way round, isn't it?
0:17:44 > 0:17:46It's all over the place, it is all over the place,
0:17:46 > 0:17:49Because the solar activity has blown the corona in all directions.
0:17:49 > 0:17:51The sun is extremely dynamic here.
0:17:51 > 0:17:53So this is an interesting time to study the sun.
0:17:53 > 0:17:55Very, very interesting.
0:17:55 > 0:17:57We are very excited about solar maximum,
0:17:57 > 0:17:58and then again the sun will come...
0:17:58 > 0:18:02in the next years will come down to a quiet stage,
0:18:02 > 0:18:04and then this whole cycle repeats every 11 years.
0:18:07 > 0:18:10So what causes these solar cycles?
0:18:14 > 0:18:19To understand, we first need to know what's going on deep inside the sun.
0:18:21 > 0:18:23It's a place we can never go,
0:18:23 > 0:18:27but we can learn a lot from something that makes the journey
0:18:27 > 0:18:32all the way from the core of the sun to us here on Earth.
0:18:32 > 0:18:33Sunlight.
0:18:35 > 0:18:39Sunlight, the light from the sun.
0:18:39 > 0:18:41We take it completely for granted.
0:18:43 > 0:18:45But it's still mysterious.
0:18:45 > 0:18:47Where did it come from? How did it get here?
0:18:50 > 0:18:54We think of sunlight as simply coming from the sun's surface.
0:18:55 > 0:18:57But its journey begins deep within our star.
0:19:00 > 0:19:05And what makes sunlight's journey so epic is the sheer size of the sun.
0:19:09 > 0:19:15The mass of the sun is 2 followed by 27 zeroes,
0:19:15 > 0:19:18that is the mass of sun in tonnes.
0:19:18 > 0:19:24And so that makes up 99.85% of the entire solar system.
0:19:24 > 0:19:25The solar system is basically just sun
0:19:25 > 0:19:28with a few little fragments circling round the outside.
0:19:31 > 0:19:33And it's the sun's enormous mass
0:19:33 > 0:19:37that creates the conditions to produce sunlight.
0:19:37 > 0:19:41Its intense gravitational pull forces the sun into layers,
0:19:41 > 0:19:43each with its own special properties.
0:19:44 > 0:19:50Beneath the thin outer peel is a 200,000-kilometre thick layer,
0:19:50 > 0:19:54where hot material rises and falls.
0:19:54 > 0:19:58The layer underneath carries the sun's heat outwards.
0:19:59 > 0:20:04And around 550,000 kilometres down is the core,
0:20:04 > 0:20:07a 16-million degree furnace.
0:20:07 > 0:20:11Here, the entire mass of the sun is pushing inwards,
0:20:11 > 0:20:13exerting vast pressure.
0:20:13 > 0:20:16And this is where sunlight is born.
0:20:23 > 0:20:26To understand how that vast pressure creates sunlight,
0:20:26 > 0:20:31I've come to the National Ignition Facility, NIF, in California.
0:20:34 > 0:20:36Sunlight exists because of a process
0:20:36 > 0:20:40going on deep in the core of the sun called fusion.
0:20:40 > 0:20:43And what's happening there is that the pressures and temperatures
0:20:43 > 0:20:47right in the middle of the sun are so enormous...
0:20:48 > 0:20:52..that hydrogen atoms can fuse together.
0:20:52 > 0:20:54And when that happens,
0:20:54 > 0:20:58a tiny, tiny bit of mass is converted into a huge amount of energy.
0:21:00 > 0:21:03And that little process is the key to a star like our sun.
0:21:06 > 0:21:11Without that single process, the sun would be a cold, dead star
0:21:11 > 0:21:14and the Earth would be a cold, dead planet.
0:21:14 > 0:21:17So the key to the behaviour of the sun
0:21:17 > 0:21:19and to life on Earth
0:21:19 > 0:21:20is fusion.
0:21:24 > 0:21:26I'm about to see how the scientists at NIF
0:21:26 > 0:21:30are trying to make a tiny sun and recreate fusion.
0:21:34 > 0:21:38All this is about getting ignition that could change the world.
0:21:38 > 0:21:40Here, in this dust-free environment,
0:21:40 > 0:21:44Beth Dzenitis creates hydrogen fuel capsules
0:21:44 > 0:21:47smaller than a grain of rice
0:21:47 > 0:21:49and destined for a very violent fate.
0:21:51 > 0:21:53This is called the capsule fill-tube assembly.
0:21:53 > 0:21:57It's a two-millimetre diameter plastic capsule.
0:21:57 > 0:22:00192 laser beams converge on the capsule,
0:22:00 > 0:22:03and that plastic material blows away from the capsule
0:22:03 > 0:22:06when it gets hot and under high pressure.
0:22:06 > 0:22:10And that causes a subsequent reaction of the fuel there
0:22:10 > 0:22:13to be compressed so that the hydrogen atoms fuse.
0:22:16 > 0:22:18To get those atoms to fuse,
0:22:18 > 0:22:22they need to generate similar pressures to those at the sun's core,
0:22:22 > 0:22:27340 billion times the pressure on Earth.
0:22:27 > 0:22:29It's a tall order.
0:22:29 > 0:22:30But there is a way.
0:22:31 > 0:22:35The 192 individual laser beams they use
0:22:35 > 0:22:40are each more powerful than any other laser on the planet.
0:22:41 > 0:22:46And they all fire at a spherical chamber at the heart of the complex.
0:22:50 > 0:22:52This is the target chamber,
0:22:52 > 0:22:56and when the lasers hit the fuel capsule at its centre,
0:22:56 > 0:23:00they bring the atoms together with the same force as in the sun's core.
0:23:03 > 0:23:05But to truly mimic our star,
0:23:05 > 0:23:09the NIF team needs to pull off an even greater trick.
0:23:10 > 0:23:13Proceeding to system shot countdown state.
0:23:15 > 0:23:20Once ignited, the fusion reaction must keep itself going.
0:23:25 > 0:23:28Starting system shot sequence on my mark.
0:23:28 > 0:23:30Three, two, one, mark.
0:23:34 > 0:23:35May I have your attention?
0:23:35 > 0:23:40Preparations for shot operations in laser bay two are under way.
0:23:40 > 0:23:44Leave laser bay two now.
0:23:44 > 0:23:46It's not without its dangers.
0:23:46 > 0:23:50Before every shot, the area is evacuated.
0:23:50 > 0:23:55Steel and concrete doors a metre thick enclose the target chamber.
0:23:55 > 0:23:58A misfire from the most powerful laser in the world
0:23:58 > 0:24:01could cause a catastrophic explosion.
0:24:01 > 0:24:05MOR ready for system shot countdown clock.
0:24:05 > 0:24:07And even the smallest fusion reaction
0:24:07 > 0:24:11unleashes a lethal blast of neutrons and high-energy light.
0:24:11 > 0:24:14..Three, two, one.
0:24:20 > 0:24:22The only visible sign
0:24:22 > 0:24:26is this flash from the world's biggest laser as it fires.
0:24:29 > 0:24:32But inside that fuel capsule,
0:24:32 > 0:24:34they're hoping to create a tiny sun
0:24:34 > 0:24:37and with it, man-made sunlight.
0:24:47 > 0:24:50Another day, another shot.
0:24:50 > 0:24:53The NIF team routinely achieve short-lived fusion.
0:24:55 > 0:24:59But today, still no self-sustaining fusion.
0:25:00 > 0:25:05Yet if we could achieve it on Earth, we'd have the sun's energy on tap.
0:25:06 > 0:25:09Recreating a small sun in this target chamber
0:25:09 > 0:25:15that's not too far away is always... daunting, in a lot of respects.
0:25:15 > 0:25:17We will get there eventually.
0:25:20 > 0:25:24It's that elusive trick of generating endless energy
0:25:24 > 0:25:26that makes our sun so miraculous.
0:25:28 > 0:25:32The result is the birth of sunlight in the sun's core,
0:25:32 > 0:25:35in particles of light energy known as photons.
0:25:42 > 0:25:44But their journey is far from over.
0:25:48 > 0:25:51Imagine this pinball is a newly created photon.
0:25:52 > 0:25:55That light must now reach the sun's surface.
0:25:59 > 0:26:04And that is a really complex and difficult journey,
0:26:04 > 0:26:07because in-between the core of the sun and the surface
0:26:07 > 0:26:11there is a seething mass of stuff that we call plasma.
0:26:13 > 0:26:16Like my pinball dodging the flippers and bumpers,
0:26:16 > 0:26:20the photon now has to navigate through that plasma.
0:26:20 > 0:26:24But my pinball - or photon - can't take a direct route out.
0:26:24 > 0:26:27It's forever colliding with particles of plasma
0:26:27 > 0:26:30moving at thousands of miles per hour.
0:26:32 > 0:26:35And with hundreds of thousands of miles of plasma to cross
0:26:35 > 0:26:39between the sun's core and its surface,
0:26:39 > 0:26:44a journey that should take two and a half seconds at the speed of light
0:26:44 > 0:26:47takes much, much longer.
0:26:49 > 0:26:53Even though it's travelling at the speed of light,
0:26:53 > 0:26:55as fast as anything can go,
0:26:55 > 0:27:01it's still estimated that it'll take 10,000 to a million years
0:27:01 > 0:27:05just to get from the core of the sun to its surface.
0:27:10 > 0:27:13And then...freedom.
0:27:20 > 0:27:22What we think of as sunlight's journey,
0:27:22 > 0:27:26the 90 million miles from the sun to the Earth,
0:27:26 > 0:27:28is only the last eight minutes
0:27:28 > 0:27:33of an odyssey that could have taken thousands and thousands of years.
0:27:47 > 0:27:49It's...lovely, fantastic,
0:27:49 > 0:27:53to think that this gentle light that's touching me now
0:27:53 > 0:27:56started off in a violent, dramatic beginning
0:27:56 > 0:27:58right in the centre of a star
0:27:58 > 0:28:02and then spent 100,000 years finding its way out of that star,
0:28:02 > 0:28:05and finally spent just eight minutes
0:28:05 > 0:28:07travelling as fast as anything in the universe can travel,
0:28:07 > 0:28:10the speed of light, to get to me here.
0:28:12 > 0:28:16But this extraordinary journey raises a question.
0:28:19 > 0:28:22Fusion in the core never stops.
0:28:22 > 0:28:25So why does the sun's activity go up and down
0:28:25 > 0:28:27with the 11-year solar cycle?
0:28:30 > 0:28:32Back at RAL,
0:28:32 > 0:28:36that's one of the questions that interests solar scientists.
0:28:36 > 0:28:41The key lies in how the fusion reaction affects the sun's plasma,
0:28:41 > 0:28:45that seething mass between the core and the surface.
0:28:46 > 0:28:49To explain why this leads to solar cycles,
0:28:49 > 0:28:55we've been joined at RAL by solar physicist Lucie Green.
0:28:55 > 0:28:58The heat generated by this reaction inside the sun,
0:28:58 > 0:29:01it heats up the gas and, in fact, it superheats it,
0:29:01 > 0:29:04so the gas is... the particles of gas are torn apart
0:29:04 > 0:29:05to form a plasma.
0:29:05 > 0:29:09Just as the hot air in the room around us is rising in packets,
0:29:09 > 0:29:13so the gases in the outer layers of the sun do the same thing.
0:29:13 > 0:29:14This is called convection.
0:29:14 > 0:29:16So gases get heated from below
0:29:16 > 0:29:18and they rise up to the surface of the sun.
0:29:20 > 0:29:24But because this gas, the plasma, is so hot,
0:29:24 > 0:29:27it's also electrically charged.
0:29:27 > 0:29:30So as it moves up and down with the convection currents,
0:29:30 > 0:29:33it creates powerful magnetic fields.
0:29:35 > 0:29:36And that's not all.
0:29:36 > 0:29:40The sun, like the Earth, spins on its axis,
0:29:40 > 0:29:43so plasma also flows sideways.
0:29:45 > 0:29:49Which has a dramatic effect on those magnetic fields.
0:29:52 > 0:29:55You start to see the magnetic field lines being wound up,
0:29:55 > 0:29:59and eventually it becomes so strong that the magnetic fields rise up
0:29:59 > 0:30:02and penetrate the surface of the sun,
0:30:02 > 0:30:04and that's when we have the build-up to solar maximum.
0:30:06 > 0:30:08At times of solar maximum,
0:30:08 > 0:30:12those magnetic loops break out from the surface of the sun,
0:30:12 > 0:30:14drawing the sun's plasma with them.
0:30:16 > 0:30:19This one loop is many times bigger than the Earth.
0:30:21 > 0:30:24But the sun doesn't stay like that.
0:30:24 > 0:30:26Eventually, the magnetic fields disperse
0:30:26 > 0:30:27and they rearrange themselves,
0:30:27 > 0:30:29and we go back to solar minimum again,
0:30:29 > 0:30:32where you have the nice ordering of the magnetic field.
0:30:32 > 0:30:34It does this every 11 years,
0:30:34 > 0:30:38and though the sun may be 90 million miles away,
0:30:38 > 0:30:43this cycle matters to us here on Earth.
0:30:43 > 0:30:47What is the implication of times of solar maximum for us on Earth?
0:30:47 > 0:30:49What do we experience?
0:30:49 > 0:30:53Well, the sun is constantly expanding out into space.
0:30:53 > 0:30:55Its outer atmosphere, with the magnetic field,
0:30:55 > 0:30:59- is being drawn out into something that we call the solar winds.- Yeah.
0:30:59 > 0:31:03Now, at times of solar minimum, the wind is fairly, erm...ungusty,
0:31:03 > 0:31:07- it flows quite slow. - Quite light.- Quite light!
0:31:07 > 0:31:11But at solar maximum, the magnetic fields start to get more complex,
0:31:11 > 0:31:15and that leads to vast streams of solar winds coming our way.
0:31:17 > 0:31:21The solar wind is a constant stream of particles
0:31:21 > 0:31:24flowing out from the sun.
0:31:24 > 0:31:26It bombards the Earth.
0:31:26 > 0:31:31Most of it is deflected by our planet's own magnetic field.
0:31:32 > 0:31:35But a small amount of its energy does get through,
0:31:35 > 0:31:38with extraordinary effects.
0:31:38 > 0:31:42Effects I'd always wanted to see for myself.
0:31:43 > 0:31:48If you want to see this evidence on Earth of solar winds,
0:31:48 > 0:31:49you need to head right up
0:31:49 > 0:31:54into areas that are cold, rather sunless and rather dark.
0:32:05 > 0:32:08This is Lapland in Arctic Sweden.
0:32:09 > 0:32:11It's February,
0:32:11 > 0:32:13it's minus 19,
0:32:13 > 0:32:16and a long winter's night is about to fall.
0:32:23 > 0:32:25I'm here to see an old friend.
0:32:25 > 0:32:28She's an extraordinary woman who, 15 years ago,
0:32:28 > 0:32:32left her home in Birmingham and came to live here permanently.
0:32:32 > 0:32:34And all because she became bewitched
0:32:34 > 0:32:37by the strange and astonishing phenomenon
0:32:37 > 0:32:39that I'm hoping to witness too.
0:32:39 > 0:32:42It's called the aurora borealis,
0:32:42 > 0:32:44also known as the northern lights.
0:32:46 > 0:32:50The aurora is the solar wind made visible on Earth.
0:32:55 > 0:32:59As the wind encounters our planet's own magnetic field,
0:32:59 > 0:33:04it sends energy down the magnetic field lines towards the poles,
0:33:04 > 0:33:08causing our atmosphere to luminesce in ghostly colours.
0:33:14 > 0:33:19Right now at solar maximum is the best time to see the aurora.
0:33:19 > 0:33:23But I still need a cloud-free, moonless night.
0:33:29 > 0:33:33My friend, Patricia Cowern, knows the challenges.
0:33:33 > 0:33:37She's photographed the aurora countless times.
0:33:39 > 0:33:43- Wow, so that's above here, isn't it? - It is above the house, yes.
0:33:43 > 0:33:45That's one of the early ones
0:33:45 > 0:33:48that I took when I very first started northern lights photography.
0:33:48 > 0:33:51- Oh, my goodness!, Look at that! - This is where we're sitting now.
0:33:51 > 0:33:52- Really?!- Yeah.
0:33:52 > 0:33:55You see, I just think I'm going to pop with excitement
0:33:55 > 0:33:57if I see a sky that looks like that.
0:33:57 > 0:34:02When we go out this evening, am I going to get to see them?
0:34:02 > 0:34:03Hopefully!
0:34:03 > 0:34:05If we can get rid of the clouds.
0:34:05 > 0:34:10- We have the darkness, we actually do have activity at this moment.- Right.
0:34:10 > 0:34:13So what we need is for these clouds to go away.
0:34:13 > 0:34:15OK, well, I'm going to get outside...
0:34:15 > 0:34:17- And start blowing.- Yes!
0:34:26 > 0:34:28Near the poles, there's a ring-shaped zone
0:34:28 > 0:34:32where our atmosphere is most affected by the solar wind's energy.
0:34:34 > 0:34:37Lapland is slap-bang in that zone,
0:34:37 > 0:34:40which is why it's such a hotspot for the aurora.
0:34:44 > 0:34:46My first attempt to see it.
0:34:50 > 0:34:53To the naked eye, it's very faint.
0:34:53 > 0:34:55But with time-lapse cameras,
0:34:55 > 0:34:59we can see there's definitely aurora going on up there.
0:34:59 > 0:35:01But although there's no moon to spoil it,
0:35:01 > 0:35:04there are clouds in the way.
0:35:04 > 0:35:08Well, it's coming up to 11 o'clock at night
0:35:08 > 0:35:12and the cloud is still stubbornly hanging around.
0:35:12 > 0:35:14There's a few breaks in it.
0:35:14 > 0:35:17I've had sort of tantalising glimpses
0:35:17 > 0:35:20of wisps of green smoke across the sky,
0:35:20 > 0:35:24but nothing like the scale that we know that they're capable of.
0:35:29 > 0:35:32I have one more night before the moon returns
0:35:32 > 0:35:34and wrecks my chance of getting a clear view.
0:35:39 > 0:35:43But it's not just sightseers like me who are drawn here.
0:35:45 > 0:35:49- I love your laboratory, it's brilliant!- Isn't it?
0:35:49 > 0:35:54'It's a perfect backdrop for scientists like Gabriela Sternberg.
0:35:54 > 0:35:57'She's interested in an important question -
0:35:57 > 0:36:00'how well is our magnetic field holding up
0:36:00 > 0:36:04'to the constant battering of the solar wind?'
0:36:04 > 0:36:09So, let's use this nice snowball to demonstrate this.
0:36:09 > 0:36:11- So if this now is the Earth...- Yeah.
0:36:11 > 0:36:14..and we have the sun, the beautiful sun, over here,
0:36:14 > 0:36:18- so from the sun now comes solar wind. - Yeah.
0:36:18 > 0:36:24And at some point, it encounters the magnetic field of the Earth.
0:36:24 > 0:36:27Most of the solar wind now goes around, like this.
0:36:27 > 0:36:32How powerful is this solar wind? I mean, obviously, we can't feel it
0:36:32 > 0:36:35because of all these layers of protection,
0:36:35 > 0:36:38but is it gale force? Is it like a hurricane?
0:36:38 > 0:36:42What happens is, it comes particles, and they come very quickly,
0:36:42 > 0:36:47- so they move with the speed of, like, 400 kilometres per second.- Wow.
0:36:47 > 0:36:49So they move really, really fast.
0:36:49 > 0:36:54So you get this gigantic shock wave where the solar wind slows down.
0:36:54 > 0:37:00This boundary separating us, or our space, from the solar wind,
0:37:00 > 0:37:03it's very, very, very, very thin.
0:37:03 > 0:37:07It's like a thin, almost transparent, veil
0:37:07 > 0:37:11separating us from this blowing wind, from the solar wind.
0:37:11 > 0:37:14And that, we think, is really cool.
0:37:14 > 0:37:18How can these really thin boundaries, how are they formed?
0:37:18 > 0:37:21And why are they so thin?
0:37:25 > 0:37:30So the aurora is but a faint trace of the solar wind's true strength.
0:37:33 > 0:37:37Out there is a violent collision where it meets our magnetic field.
0:37:38 > 0:37:41That thin shell gives us vital shelter.
0:37:47 > 0:37:50Last night in Sweden.
0:37:50 > 0:37:52It's tonight or never.
0:37:54 > 0:37:58It's about...minus 30 outside,
0:37:58 > 0:38:03and it's absolutely clear, it's been clear all day.
0:38:03 > 0:38:05So we're going to go out and see what's happening.
0:38:08 > 0:38:10Oh, my goodness, look at those stars.
0:38:12 > 0:38:13It's so clear!
0:38:18 > 0:38:21Oh, my goodness, look at that!
0:38:21 > 0:38:23Look what's happening in the sky!
0:38:25 > 0:38:28With ordinary cameras, you can see it faintly.
0:38:30 > 0:38:35But it's with the time-lapse cameras that we can capture the full glory.
0:38:43 > 0:38:48Look at that, it's just...spanning the whole of the eastern sky,
0:38:48 > 0:38:52like a giant sort of green rainbow.
0:38:55 > 0:38:59Under this balaclava, I am grinning like the Cheshire cat.
0:39:03 > 0:39:04- It's mesmerising, isn't it? - Beautiful.
0:39:04 > 0:39:07You can't kind of take your eyes away from it.
0:39:09 > 0:39:14The aurora is a stunningly beautiful display of the solar wind,
0:39:14 > 0:39:17but also a reminder of its enormous power
0:39:17 > 0:39:23and the protection we get from the Earth's thin magnetic shield.
0:39:23 > 0:39:24So what would happen
0:39:24 > 0:39:28if we were ever exposed to the full force of the sun?
0:39:31 > 0:39:34It's a question that the scientists back here at RAL
0:39:34 > 0:39:37have been studying intently.
0:39:37 > 0:39:41The solar wind is a mere hint of the vast amount of radiation
0:39:41 > 0:39:44and particles that the sun sends our way.
0:39:44 > 0:39:46It's known as solar weather,
0:39:46 > 0:39:50and its impact on Earth can have a more alarming side.
0:39:53 > 0:39:57Richard Harrison, head of space science at RAL,
0:39:57 > 0:40:01is an expert on its most violent form, solar storms.
0:40:03 > 0:40:06So, Richard, we know that the Earth is protected
0:40:06 > 0:40:10from the full force of solar weather by the Earth's magnetic field,
0:40:10 > 0:40:14but is there any danger that that magnetic field could be breached?
0:40:14 > 0:40:16Well, the best way to answer that
0:40:16 > 0:40:19is actually to look back at the sun's atmosphere again
0:40:19 > 0:40:22and these wonderful magnetic loops in the sun's atmosphere,
0:40:22 > 0:40:26like elastic bands sort of writhing around, being tied up in knots.
0:40:26 > 0:40:29And you might expect occasionally something might break,
0:40:29 > 0:40:32so in these regions you see here, that happens.
0:40:32 > 0:40:35This image here is actually from helium in the sun's atmosphere,
0:40:35 > 0:40:37and you see a huge cloud erupting there.
0:40:37 > 0:40:41That's a billion tonnes of mass from the sun being ejected into space,
0:40:41 > 0:40:43so something in the sun's atmosphere just snapped.
0:40:49 > 0:40:54These gigantic solar storms are called coronal mass ejections.
0:40:58 > 0:41:01They are the most high-energy events in the solar system
0:41:01 > 0:41:05and the sun unleashes more of them at solar maximum
0:41:05 > 0:41:06than at any other time.
0:41:08 > 0:41:12They can hurl clouds of plasma towards us at alarming speeds.
0:41:13 > 0:41:16To cover the 90 million miles from the sun,
0:41:16 > 0:41:19seen here reduced in scale on the right,
0:41:19 > 0:41:21to the Earth on the left
0:41:21 > 0:41:23can take less than a day.
0:41:24 > 0:41:26And as Helen found out,
0:41:26 > 0:41:30they have the power to overwhelm the Earth's defences.
0:41:41 > 0:41:45Solar storms can destroy satellites,
0:41:45 > 0:41:47silence communications,
0:41:47 > 0:41:49ground aircraft.
0:41:55 > 0:41:56Order up!
0:41:56 > 0:42:00But the link they threaten most in our modern lives
0:42:00 > 0:42:03is our dependence on electricity.
0:42:05 > 0:42:09If you have any doubt, take a look at this booklet.
0:42:09 > 0:42:13It's published by Lloyd's of London, who are insurers,
0:42:13 > 0:42:15and they wrote it with the Rutherford Appleton Laboratory,
0:42:15 > 0:42:18and I think one of the most interesting sections
0:42:18 > 0:42:20is where it lists the potential impacts
0:42:20 > 0:42:23that disruption to the power supply would have.
0:42:23 > 0:42:26And this is important, because our power grid is one of the things
0:42:26 > 0:42:28that's most vulnerable to a big solar storm.
0:42:31 > 0:42:35The highly charged particles of coronal mass ejections
0:42:35 > 0:42:40can induce powerful electrical currents on the Earth's surface,
0:42:40 > 0:42:43overloading circuits and melting transformers.
0:42:45 > 0:42:48And the reason it matters so much is that everything is interconnected.
0:42:50 > 0:42:55And so if we lost power, we'd not only lose lighting and heating
0:42:55 > 0:42:57and the ability to cook our food.
0:42:57 > 0:42:59We also, for example, lose our fuel,
0:42:59 > 0:43:02because pumping stations rely on having electricity
0:43:02 > 0:43:05to pump the fuel out of their reservoirs.
0:43:05 > 0:43:10Sanitation, water supplies, communication systems.
0:43:16 > 0:43:20We know we're vulnerable because we've been hit in the past.
0:43:20 > 0:43:26In Quebec, the entire power grid went down after a solar storm in 1989,
0:43:26 > 0:43:29plunging millions into freezing darkness.
0:43:37 > 0:43:39But we're not helpless.
0:43:39 > 0:43:44There are precautions we can take against the effects of solar weather.
0:43:44 > 0:43:49We're already building systems and technologies that are resilient.
0:43:49 > 0:43:53But it would be even better if we could prepare for specific storms.
0:43:53 > 0:43:56But for that, we need to know when they're going to arrive,
0:43:56 > 0:43:58we need an early warning system,
0:43:58 > 0:44:02and fortunately, there's one in this building right here.
0:44:06 > 0:44:08Forecast's now trending downward.
0:44:08 > 0:44:11There were several filaments that either erupted...
0:44:11 > 0:44:14The Space Weather Prediction Center in Colorado
0:44:14 > 0:44:16is the only team on the planet
0:44:16 > 0:44:21solely dedicated to watching for solar storms.
0:44:21 > 0:44:23No alerts or warnings are currently issued...
0:44:23 > 0:44:26The aim is to alert governments, power companies
0:44:26 > 0:44:31and the aviation and space industries that a storm is on its way.
0:44:31 > 0:44:34Even a few hours' warning can help them prepare.
0:44:36 > 0:44:38Chief forecaster Bob Rutledge
0:44:38 > 0:44:41is going to teach me how to predict solar storms.
0:44:41 > 0:44:45Space weather really starts with sunspots.
0:44:45 > 0:44:48What that sunspot is doing, how much is it changing,
0:44:48 > 0:44:51and how complex are those magnetic fields underneath those spots
0:44:51 > 0:44:53are really what we use
0:44:53 > 0:44:55to say how likely are we to have significant activity.
0:44:55 > 0:44:58So what are the different events that could happen?
0:44:58 > 0:45:02So when we get a solar flare, it's essentially the start of the event.
0:45:02 > 0:45:04That's the giant explosion.
0:45:04 > 0:45:06We see that, essentially, in this image in X-ray,
0:45:06 > 0:45:09so it's a brightening in light and radio waves,
0:45:09 > 0:45:10so that's our first clue.
0:45:10 > 0:45:15The last piece is, does the portion of the sun's outer atmosphere
0:45:15 > 0:45:18that sits above that, you know, a billion tonnes of plasma,
0:45:18 > 0:45:20does it get blown into space as well?
0:45:20 > 0:45:22So we start to watch other images of the sun,
0:45:22 > 0:45:25like this, for example, where we've blocked out the centre.
0:45:25 > 0:45:30We watch for the faint pieces of atmosphere being blown into space.
0:45:30 > 0:45:32So the ones that go off to the side, albeit beautiful,
0:45:32 > 0:45:34- don't really matter to Earth.- Right.
0:45:34 > 0:45:37It's really looking and seeing if it's coming our way or not,
0:45:37 > 0:45:40and if so, how fast, and when do we expect it to get here?
0:45:45 > 0:45:49These images are coming from the same new generation of satellites
0:45:49 > 0:45:52used by the scientists at RAL.
0:45:52 > 0:45:56They're our eyes in space that keep watch over the sun.
0:46:01 > 0:46:03I can see it with visible light.
0:46:05 > 0:46:07Magnetic fields.
0:46:09 > 0:46:10X-rays.
0:46:13 > 0:46:15On a typical day near solar maximum,
0:46:15 > 0:46:19the sun will send out three coronal mass ejections.
0:46:21 > 0:46:24Fortunately, today there haven't been any.
0:46:25 > 0:46:28But dramatic events can happen with little warning.
0:46:31 > 0:46:34You've got a video here of a very special event.
0:46:34 > 0:46:36I've picked out from late October 2003
0:46:36 > 0:46:38probably the last significant,
0:46:38 > 0:46:42really big round of space weather activity that we had.
0:46:42 > 0:46:45We've blocked out the sun so we can see the atmosphere.
0:46:45 > 0:46:46You'll see the eruption.
0:46:46 > 0:46:49- Oh, yeah! Really symmetrical. - Look at that. Massive cloud.
0:46:49 > 0:46:51It looks like a halo, coming straight at you.
0:46:51 > 0:46:55It was going at tremendous speed, so it made it here in under a day.
0:46:55 > 0:46:59So we have levels one through five, just like a hurricane or tornado,
0:46:59 > 0:47:02- and it was pegged at that five level storm.- It was as big as it gets.
0:47:04 > 0:47:09That solar storm took out the power grid in the Swedish city of Malmo.
0:47:09 > 0:47:12Tens of thousands were left without electricity.
0:47:16 > 0:47:19On that occasion, the Earth was only struck a glancing blow,
0:47:19 > 0:47:23but we can't be sure that next time we'll be so lucky.
0:47:25 > 0:47:27Today, if we saw this happen again,
0:47:27 > 0:47:29we'd be able to give our partners in the key industries,
0:47:29 > 0:47:32like the electric-power industry, a heads-up to say,
0:47:32 > 0:47:35"Hey, prepare your systems, keep them as safe as you can."
0:47:45 > 0:47:49We're only just beginning to understand solar weather,
0:47:49 > 0:47:52but we can't afford to ignore it.
0:47:54 > 0:47:56I've been looking at the sun all day
0:47:56 > 0:48:00and yet I haven't actually seen very much sunlight, and now it's got dark.
0:48:00 > 0:48:02But here's what gets me about today.
0:48:02 > 0:48:05Imagine the big weather events we have on Earth,
0:48:05 > 0:48:09you know, thunderstorms and even bigger than that, hurricanes.
0:48:09 > 0:48:12And then take a step back,
0:48:12 > 0:48:17and all those massive events suddenly become tiny specks on the Earth,
0:48:17 > 0:48:21sailing through this solar weather, which is even bigger.
0:48:24 > 0:48:26We've come a long way
0:48:26 > 0:48:29from the idea of the sun as simply a giver of light and warmth.
0:48:31 > 0:48:34Its effects on our planet are far more complex.
0:48:40 > 0:48:43Thanks to solar scientists, our sun is being revealed
0:48:43 > 0:48:46as a dynamic, vigorous fusion reactor,
0:48:46 > 0:48:49pulsing through its 11-year cycle
0:48:49 > 0:48:53and belching plumes of highly charged particles in our direction.
0:48:55 > 0:48:58As the scientists at RAL have shown us,
0:48:58 > 0:49:00that 11-year solar cycle
0:49:00 > 0:49:04has become the heart of how we understand the sun.
0:49:05 > 0:49:08Many of the more surprising effects the sun has on our lives
0:49:08 > 0:49:14depend on how its activity rises and falls through the cycle.
0:49:14 > 0:49:18But scientists are now beginning to explore a radically new idea,
0:49:18 > 0:49:22that these cycles are not as set as we once thought.
0:49:24 > 0:49:29The latest research suggests that the cycles themselves could be changing.
0:49:29 > 0:49:31We could be living through bigger shifts in the sun's behaviour
0:49:31 > 0:49:33than we thought.
0:49:41 > 0:49:43The clue comes from a phenomenon
0:49:43 > 0:49:46that astronomers have been observing for centuries -
0:49:46 > 0:49:49sunspots.
0:49:49 > 0:49:52They've been known about since long before the era of satellites,
0:49:52 > 0:49:54or even telescopes.
0:49:59 > 0:50:02Looking directly at the sun without proper filters
0:50:02 > 0:50:04is clearly a terrible idea,
0:50:04 > 0:50:06because you could really, really damage your eyes.
0:50:06 > 0:50:09But that didn't stop early astronomers from trying.
0:50:09 > 0:50:14And just sometimes, maybe at sunrise or sunset or on a cloudy day,
0:50:14 > 0:50:18they'd see something that made the sun worth looking at -
0:50:18 > 0:50:20tiny dark spots.
0:50:20 > 0:50:22And for years, they just assumed that those spots
0:50:22 > 0:50:25were planets that were passing between the Earth and the sun.
0:50:25 > 0:50:28And then the telescope was invented,
0:50:28 > 0:50:31and Galileo could draw diagrams like these
0:50:31 > 0:50:34and map out where these dark spots were.
0:50:34 > 0:50:35And it became apparent
0:50:35 > 0:50:38that they're actually part of the surface of the sun.
0:50:43 > 0:50:45Thanks to those early astronomers,
0:50:45 > 0:50:48sunspots are one of the few bits of evidence we have
0:50:48 > 0:50:51about the sun's long-term behaviour.
0:50:52 > 0:50:56And new research is revealing something surprising about them.
0:50:59 > 0:51:03The key is how they're created.
0:51:05 > 0:51:10Sunspots are caused by the magnetic fields deep inside the sun,
0:51:10 > 0:51:12and we can't see those magnetic fields directly,
0:51:12 > 0:51:15but the sunspots are offering us some clues as to what's going on.
0:51:15 > 0:51:19And we know that the more active the sun is, the more sunspots there are.
0:51:23 > 0:51:26As the sun approaches solar maximum
0:51:26 > 0:51:29and the magnetic field lines beneath its surface become tangled,
0:51:29 > 0:51:34the flow of plasma within is disrupted.
0:51:34 > 0:51:39Hot material from the interior can't rise to the surface.
0:51:39 > 0:51:42The result is zones of cooler plasma.
0:51:42 > 0:51:44Sunspots.
0:51:45 > 0:51:48They're like windows in the sun's surface,
0:51:48 > 0:51:51through which we can study what's happening inside the sun itself.
0:52:03 > 0:52:08The McMath solar telescope in Arizona is the largest in the world.
0:52:13 > 0:52:1717 years ago, a study of sunspots began here,
0:52:17 > 0:52:20led by a group of astronomers, including Matt Penn.
0:52:23 > 0:52:25'They began to look at the average strength
0:52:25 > 0:52:28'of the magnetic fields in the sunspots.'
0:52:28 > 0:52:31So here we have the main mirror...
0:52:31 > 0:52:33'Something no-one had tried before.'
0:52:34 > 0:52:37So what got you started on this study?
0:52:37 > 0:52:40So we wanted to take regular observations of the sun
0:52:40 > 0:52:42to find out what sunspots were doing over time.
0:52:42 > 0:52:44We know that the number of sunspots
0:52:44 > 0:52:46increases and decreases in the solar cycle.
0:52:46 > 0:52:48Actually, that's how the solar cycle was discovered,
0:52:48 > 0:52:50by early observations of sunspots.
0:52:50 > 0:52:54During solar minimum, there'd be zero or five sunspots on the disc.
0:52:54 > 0:52:56During maximum, there could be 100.
0:52:56 > 0:52:58During that 11-year period,
0:52:58 > 0:53:01we wondered what was happening to the magnetic fields in sunspots.
0:53:01 > 0:53:03Was it increasing along with the number of sunspots?
0:53:03 > 0:53:06Was it flat, or was it doing something else? We just didn't know.
0:53:06 > 0:53:09- And is it what you'd expect? - Well, no, it turns out
0:53:09 > 0:53:12that the data showed us something completely different.
0:53:14 > 0:53:18Matt and colleagues are using an ingenious way of measuring
0:53:18 > 0:53:21the strength of the magnetic field and sunspots.
0:53:22 > 0:53:25A change in the infrared light coming from them.
0:53:27 > 0:53:29So this is a really lovely, simple method,
0:53:29 > 0:53:32because you can point your telescope at any point on the sun
0:53:32 > 0:53:34and from the light coming out of it,
0:53:34 > 0:53:37this simple thing of watching how these spectral shapes change,
0:53:37 > 0:53:40you can see exactly how strong the magnetic field is
0:53:40 > 0:53:42anywhere on the face of the sun.
0:53:42 > 0:53:45Exactly, so we measure the magnetic field with the spectral line,
0:53:45 > 0:53:48and we've done a survey of 3,000 sunspots over the past ten years,
0:53:48 > 0:53:51measuring the magnetic field strength in each sunspot.
0:53:54 > 0:53:56And what they've discovered is surprising.
0:53:57 > 0:53:59Instead of rising and falling
0:53:59 > 0:54:02in line with the solar cycle, as expected,
0:54:02 > 0:54:04the magnetic strength of sunspots
0:54:04 > 0:54:08has been steadily decreasing year by year.
0:54:10 > 0:54:13Right back in 2000, the magnetic field was quite high,
0:54:13 > 0:54:15and it's just gradually gone down and down and down
0:54:15 > 0:54:18over the past ten years, quite consistently.
0:54:18 > 0:54:20So a decreasing trend means that in the future,
0:54:20 > 0:54:22we may not have any sunspots at all.
0:54:25 > 0:54:27It's an extraordinary result.
0:54:30 > 0:54:31The trend suggests
0:54:31 > 0:54:34that, over and above the familiar 11-year solar cycle,
0:54:34 > 0:54:37there are bigger patterns in the sun's activity.
0:54:39 > 0:54:44And in the long-term, we may be heading for an extended quiet period,
0:54:44 > 0:54:48what solar scientists call a grand minimum.
0:54:52 > 0:54:54Intriguingly, we've been here before.
0:54:56 > 0:55:02Thanks to those historical records, we know that around 350 years ago,
0:55:02 > 0:55:06sunspots almost vanished for 70 years.
0:55:09 > 0:55:12So it looks as though the sunspots could be dying away.
0:55:12 > 0:55:14If that happens, what difference does that make to us?
0:55:14 > 0:55:18Right, if sunspots do go away and we enter a new grand minimum,
0:55:18 > 0:55:21there are possible effects on the climate.
0:55:21 > 0:55:23Records suggest the temperature in Europe, for instance,
0:55:23 > 0:55:25decreased during the last grand minimum.
0:55:30 > 0:55:33A grand minimum would be a double-edged sword.
0:55:34 > 0:55:38It might mean fewer solar storms, something in our favour.
0:55:42 > 0:55:45But it could also mean a dramatic change in our weather.
0:55:47 > 0:55:48The previous grand minimum
0:55:48 > 0:55:51coincided with a period of brutally harsh winters
0:55:51 > 0:55:53in Europe and North America.
0:55:56 > 0:56:00The River Thames in London famously froze solid.
0:56:00 > 0:56:03It was known as the Little Ice Age.
0:56:09 > 0:56:11So this is a sort of intriguing time, right?
0:56:11 > 0:56:14You can see maybe just the start of these big changes,
0:56:14 > 0:56:16but you can't quite see why they're happening.
0:56:16 > 0:56:19- But there are potentially very big impacts if they do.- Exactly.
0:56:19 > 0:56:22This data suggests that the sun is going through a major change,
0:56:22 > 0:56:23a global change on the sun.
0:56:23 > 0:56:26So in the long-term life of the sun, we'd love to know what's going on.
0:56:30 > 0:56:32If this trend does continue,
0:56:32 > 0:56:37it may be evidence of a bigger cycle in the sun's behaviour
0:56:37 > 0:56:39that we've only just begun to glimpse.
0:56:41 > 0:56:44But the sun works on such vast timescales,
0:56:44 > 0:56:49even several hundred years of data can give us only a tantalising clue.
0:56:53 > 0:56:56So we've been watching the sun for a few centuries,
0:56:56 > 0:56:59but we don't know what was happening when the pyramids were being built,
0:56:59 > 0:57:03or when the dinosaurs were alive, or a billion years ago.
0:57:03 > 0:57:05And we don't know what's going to be happening
0:57:05 > 0:57:06a billion years into the future,
0:57:06 > 0:57:10so we're just seeing this tiny, tiny sliver of the lifetime of the sun,
0:57:10 > 0:57:14and it's really hard to imagine that in this enormous timescale.
0:57:18 > 0:57:23And that's the big challenge that lies ahead for solar scientists.
0:57:29 > 0:57:32What's emerging is that even the pattern we thought we knew,
0:57:32 > 0:57:35the 11-year solar cycle, isn't the full story.
0:57:35 > 0:57:38There are bigger, longer-term patterns in the life of our sun,
0:57:38 > 0:57:42and they could have profound influences on our planet and others.
0:57:42 > 0:57:44What's incredibly exciting
0:57:44 > 0:57:47is just how quickly our knowledge of the sun is growing.
0:57:47 > 0:57:50And thanks to huge technological and scientific advances,
0:57:50 > 0:57:54its surprises are gradually being uncovered.
0:57:54 > 0:57:57And next time you feel the sun warm your cheeks
0:57:57 > 0:58:00or you admire a sunrise, it's worth remembering
0:58:00 > 0:58:04just how complex and wonderful our local star really is.
0:58:32 > 0:58:35Subtitles by Red Bee Media Ltd