Y Cosmos: Yr Haul Y Cosmos
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-Subtitles | 0:00:00 | 0:00:00 | |
-Subtitles - -Subtitles | 0:00:00 | 0:00:02 | |
-The sun. | 0:00:04 | 0:00:05 | |
-Without it, we'd be in darkness -and nothing could live. | 0:00:07 | 0:00:11 | |
-The sun is essential -to all life on earth. | 0:00:15 | 0:00:18 | |
-Life relies on the amazing journey -of a small packet of light. | 0:00:23 | 0:00:28 | |
-The photon. | 0:00:28 | 0:00:29 | |
-The photon has been -on a very long journey... | 0:00:31 | 0:00:35 | |
-..and has struggled to reach us. | 0:00:36 | 0:00:38 | |
-The photon, which brings us -light and heat, is ancient. | 0:00:39 | 0:00:44 | |
-It's fantastic that the light -we see today from the sun... | 0:00:45 | 0:00:49 | |
-..was created -in the age of the dinosaurs. | 0:00:49 | 0:00:52 | |
-In this programme, we follow the -photon on its incredible journey... | 0:00:54 | 0:00:59 | |
-..from the sun's core -to its escape to earth. | 0:00:59 | 0:01:03 | |
-And we learn how, and why, -everything on earth relies on it. | 0:01:05 | 0:01:09 | |
-The cosmos. | 0:01:24 | 0:01:26 | |
-Home to billions of galaxies... | 0:01:26 | 0:01:29 | |
-..each made of billions of stars. | 0:01:30 | 0:01:32 | |
-And in an unremarkable corner -of the Milky Way, our galaxy... | 0:01:34 | 0:01:39 | |
-..lies the sun, our closest star. | 0:01:39 | 0:01:41 | |
-A dazzling sphere of intense light. | 0:01:46 | 0:01:48 | |
-Too bright for the naked eye... | 0:01:50 | 0:01:52 | |
-..but strip away that glare, -and the sun transforms. | 0:01:54 | 0:01:58 | |
-The sun is the most important thing -in our local system. | 0:02:07 | 0:02:11 | |
-Think of the sun as the mother. | 0:02:12 | 0:02:15 | |
-All the planets, including earth, -are like small children around her. | 0:02:15 | 0:02:20 | |
-The sun drives everything -in our local system. | 0:02:23 | 0:02:26 | |
-The sun generates heat and light. -It sustains life. | 0:02:35 | 0:02:39 | |
-The energy we get from the sun -drives all life on earth. | 0:02:42 | 0:02:47 | |
-Unbeknown to us, -the sun is our nuclear powerhouse. | 0:02:51 | 0:02:55 | |
-Our entire existence... | 0:02:58 | 0:03:00 | |
-..is powered by the energy emitted -in nuclear reactions in the sun. | 0:03:00 | 0:03:05 | |
-We are here -because of the light from the sun. | 0:03:05 | 0:03:08 | |
-No aspect of our existence -could persist if it wasn't there. | 0:03:09 | 0:03:13 | |
-Light is essential to life. | 0:03:17 | 0:03:19 | |
-Light is the fastest thing -in the cosmos. | 0:03:31 | 0:03:33 | |
-It travels -at 186,000 miles per second. | 0:03:34 | 0:03:38 | |
-The sun is about 93 million miles -away from us. | 0:03:44 | 0:03:47 | |
-Light travels at a speed -of around 186,000 miles per second. | 0:03:48 | 0:03:53 | |
-Light takes around eight minutes -to reach us from the sun. | 0:03:55 | 0:04:00 | |
-The final leg through space... | 0:04:02 | 0:04:04 | |
-..is just a tiny part -of the photon's journey. | 0:04:04 | 0:04:08 | |
-It can take up to a million years... | 0:04:15 | 0:04:18 | |
-..for light to escape -from the sun's interior. | 0:04:18 | 0:04:21 | |
-When we see light coming from -the sun, we don't realize... | 0:04:30 | 0:04:35 | |
-..how old those photons are. | 0:04:36 | 0:04:38 | |
-They took centuries to travel -from the sun's interior... | 0:04:38 | 0:04:41 | |
-..before whizzing for eight minutes -to reach earth. | 0:04:42 | 0:04:45 | |
-I remember first hearing that fact. | 0:04:47 | 0:04:49 | |
-It's remarkable -that the light we see today... | 0:04:51 | 0:04:54 | |
-..was created when our forefathers -were monkeys in Africa. | 0:04:54 | 0:04:58 | |
-The journey starts -deep inside the sun. | 0:05:03 | 0:05:06 | |
-If we could open up the sun we'd see -layers of dense hydrogen gas... | 0:05:09 | 0:05:14 | |
-..hundreds of thousands -of miles deep. | 0:05:15 | 0:05:18 | |
-And at its centre, -the sun creates light... | 0:05:19 | 0:05:22 | |
-..out of the most violent reaction -in the cosmos. | 0:05:23 | 0:05:27 | |
-Nuclear fusion. | 0:05:29 | 0:05:31 | |
-A nuclear reaction -happens in the sun... | 0:05:32 | 0:05:35 | |
-..when protons, -the nuclei of hydrogen atoms... | 0:05:35 | 0:05:39 | |
-..fuse together -to create nuclear fusion. | 0:05:39 | 0:05:42 | |
-It sounds simple but it isn't. | 0:05:44 | 0:05:46 | |
-These protons have equal charge. | 0:05:47 | 0:05:50 | |
-When they collide, -they try to separate. | 0:05:50 | 0:05:53 | |
-If a proton is positive, -and we put two positives together... | 0:05:54 | 0:05:58 | |
-..it's like trying to push -two magnet heads together. | 0:06:00 | 0:06:04 | |
-You need a huge pressure and heat -to force them together. | 0:06:05 | 0:06:09 | |
-Forcing protons together takes -intense heat and huge pressure. | 0:06:10 | 0:06:15 | |
-This happens -due to the power of gravity. | 0:06:17 | 0:06:21 | |
-The sun contains almost all -the matter in the solar system. | 0:06:24 | 0:06:29 | |
-Incredible amounts of gravity -stops the sun from breaking up. | 0:06:29 | 0:06:34 | |
-The gravity created by all this mass -creates huge density in the sun... | 0:06:38 | 0:06:43 | |
-..which allows nuclear fusion -to happen. | 0:06:44 | 0:06:48 | |
-In this nuclear powerhouse, hydrogen -atoms constantly slam together. | 0:06:51 | 0:06:56 | |
-Atoms fuse, releasing energy... | 0:07:01 | 0:07:04 | |
-..but, unexpectedly, -fusion does not happen every time. | 0:07:12 | 0:07:16 | |
-Less than 1% of this mass -is converted into energy. | 0:07:23 | 0:07:27 | |
-It's an inefficient process. | 0:07:28 | 0:07:30 | |
-Protons smash together -but most don't react. | 0:07:33 | 0:07:37 | |
-Most of the protons that collide -don't fuse. | 0:07:40 | 0:07:43 | |
-Electromagnetic force -pushes them apart before they fuse. | 0:07:43 | 0:07:49 | |
-Once in every billion years... | 0:07:53 | 0:07:55 | |
-..a proton -will be lucky enough to fuse... | 0:07:55 | 0:07:58 | |
-..and this energy sustains the sun. | 0:07:59 | 0:08:01 | |
-That's good news for us. | 0:08:04 | 0:08:05 | |
-Most protons wait -almost the lifetime of the earth... | 0:08:09 | 0:08:13 | |
-..before they have a reaction. | 0:08:13 | 0:08:15 | |
-If they all reacted right away, -the sun will go poof in an instant. | 0:08:15 | 0:08:19 | |
-That means the sun can keep going -for much longer... | 0:08:20 | 0:08:23 | |
-..than if all the protons fused -with every collision. | 0:08:24 | 0:08:27 | |
-The sun's core is so dense, -atoms are forced together... | 0:08:32 | 0:08:36 | |
-..and the rare reaction of fusion -is achieved. | 0:08:36 | 0:08:39 | |
-Millions of tons of hydrogen... | 0:08:41 | 0:08:44 | |
-..are turned into helium -in the sun's core every second. | 0:08:44 | 0:08:48 | |
-This is like many Mount Snowdons -coming together every second. | 0:08:50 | 0:08:54 | |
-Nuclear fusion -also happens on earth. | 0:09:05 | 0:09:08 | |
-Hydrogen bombs harness the raw power -of fusion reactions. | 0:09:14 | 0:09:18 | |
-A huge amount of energy is created -from a tiny amount of hydrogen. | 0:09:19 | 0:09:24 | |
-On earth, the closest we've come -to re-creating a similar process... | 0:09:27 | 0:09:32 | |
-..is hydrogen bombs. | 0:09:32 | 0:09:34 | |
-Huge energy can be created -from a small amount of matter. | 0:09:35 | 0:09:39 | |
-The biggest nuclear bomb -ever detonated... | 0:09:42 | 0:09:45 | |
-..had ten times more power than all -the explosives used in World War II. | 0:09:46 | 0:09:52 | |
-An immense amount of energy. | 0:09:54 | 0:09:56 | |
-But this is nothing -compared to the sun. | 0:09:57 | 0:10:01 | |
-When we talk about the sun, we're -talking about a much larger scale. | 0:10:04 | 0:10:09 | |
-Around 100 billion hydrogen bombs -explode every second in the sun. | 0:10:09 | 0:10:14 | |
-In the core of our sun, -hydrogen atoms collide and explode. | 0:10:18 | 0:10:22 | |
-Each collision creates a photon... | 0:10:26 | 0:10:28 | |
-..a tiny but incredibly powerful -packet of light. | 0:10:29 | 0:10:32 | |
-The photon delivers its energy to -earth, where it makes life possible. | 0:10:34 | 0:10:40 | |
-But when it starts its journey, -it's nothing like the light we see. | 0:10:40 | 0:10:45 | |
-It has massive amounts of energy... | 0:10:46 | 0:10:49 | |
-..and it can be deadly. | 0:10:49 | 0:10:51 | |
-. | 0:11:01 | 0:11:01 | |
-Subtitles | 0:11:04 | 0:11:04 | |
-Subtitles - -Subtitles | 0:11:04 | 0:11:06 | |
-The light we see -from our star, the sun, is old. | 0:11:14 | 0:11:18 | |
-It's much older... | 0:11:19 | 0:11:21 | |
-..than the eight minutes it takes -to get from the sun to earth. | 0:11:21 | 0:11:25 | |
-That short leap across space is -the end of a long, hard journey... | 0:11:27 | 0:11:32 | |
-..which starts deep inside our sun. | 0:11:32 | 0:11:35 | |
-When we look at the sun, -we see a bright ball of light... | 0:11:41 | 0:11:45 | |
-..which is fairly calm. | 0:11:45 | 0:11:47 | |
-But there's much more going on which -we can't see with the naked eye. | 0:11:47 | 0:11:52 | |
-The journey starts in -the immense heat of the sun's core. | 0:11:57 | 0:12:01 | |
-Crushed together -by the sun's gravity... | 0:12:05 | 0:12:08 | |
-..atoms smash into each other -and fuse... | 0:12:09 | 0:12:12 | |
-..releasing a tiny packet of energy. | 0:12:13 | 0:12:16 | |
-A photon of light. | 0:12:17 | 0:12:19 | |
-Far smaller than an atom, photons -travel faster than anything else... | 0:12:20 | 0:12:24 | |
-..and they never stop moving. | 0:12:28 | 0:12:30 | |
-Photons don't just come from -the core of stars. | 0:12:36 | 0:12:40 | |
-Any matter that moves creates light. | 0:12:41 | 0:12:45 | |
-Matter at any temperature -above absolute zero moves... | 0:12:45 | 0:12:50 | |
-..and creates light. | 0:12:50 | 0:12:52 | |
-It's the temperature that determines -how much light is generated. | 0:12:56 | 0:13:01 | |
-Everything consists -of different elements. | 0:13:01 | 0:13:05 | |
-When moving, they emit light -from the electromagnetic spectrum. | 0:13:05 | 0:13:11 | |
-We humans are made out of these -elements, so we also emit light. | 0:13:12 | 0:13:17 | |
-White light can be split -into the colours of the rainbow. | 0:13:22 | 0:13:26 | |
-Each colour is a photon of light... | 0:13:29 | 0:13:32 | |
-..with slightly different amounts -of energy. | 0:13:32 | 0:13:35 | |
-But what we can see is only -a fraction of the light spectrum. | 0:13:36 | 0:13:40 | |
-We can see light -in the optical spectrum... | 0:13:41 | 0:13:44 | |
-..so we can see the sun's light and -we can see things from day to day. | 0:13:44 | 0:13:49 | |
-We can't see infrared - the thermal -radiation emitted by our bodies. | 0:13:49 | 0:13:55 | |
-However, we can use -thermal imaging cameras... | 0:13:59 | 0:14:03 | |
-..to see the infrared radiation -emitted by our bodies. | 0:14:03 | 0:14:07 | |
-Using special cameras, we can see -the infrared light that humans emit. | 0:14:10 | 0:14:15 | |
-This infrared light has less energy -than the visible light we see. | 0:14:16 | 0:14:21 | |
-Some light is too energetic to see, -such as ultraviolet and X-rays. | 0:14:23 | 0:14:29 | |
-The vast, hot sun -generates all forms of light. | 0:14:36 | 0:14:40 | |
-At NASA's Solar Dynamics Observatory -in America... | 0:14:43 | 0:14:47 | |
-..they can see the sun -in its true light. | 0:14:48 | 0:14:51 | |
-SDO measures light -in ten different band passes... | 0:14:51 | 0:14:55 | |
-..most of which -are in the far ultraviolet. | 0:14:55 | 0:14:58 | |
-They cut through the glare to reveal -a different perspective on the sun. | 0:15:06 | 0:15:11 | |
-The images from SDO are just -amazingly spectacular to look at. | 0:15:15 | 0:15:20 | |
-And they were the day -we turned on the instruments. | 0:15:22 | 0:15:26 | |
-By looking at the sun -in different forms of light... | 0:15:29 | 0:15:32 | |
-..we can see the complete picture. | 0:15:33 | 0:15:35 | |
-But in the nuclear furnace -of the sun's core... | 0:15:43 | 0:15:46 | |
-..every photon starts out -as a gamma ray. | 0:15:46 | 0:15:49 | |
-The most energetic form of light -in the cosmos. | 0:15:49 | 0:15:53 | |
-In the sun's core, -a nuclear reaction happens... | 0:15:54 | 0:15:57 | |
-..and hydrogen turns into helium. | 0:15:57 | 0:16:00 | |
-As part of that process, -gamma ray photons are created. | 0:16:01 | 0:16:04 | |
-They emit a million times the energy -of visible photons. | 0:16:04 | 0:16:08 | |
-Gamma rays can transform... | 0:16:09 | 0:16:12 | |
-..and even kill. | 0:16:13 | 0:16:15 | |
-Gamma rays have so much energy, -they destroy atoms and molecules. | 0:16:15 | 0:16:20 | |
-If millions of photons -get into the body... | 0:16:20 | 0:16:23 | |
-..they can destroy DNA -and cause cancer. | 0:16:23 | 0:16:26 | |
-Fortunately for us... | 0:16:29 | 0:16:31 | |
-..our gamma ray photon -can't head straight out of the sun. | 0:16:31 | 0:16:35 | |
-Processes in the sun's core create -these energetic gamma ray photons. | 0:16:40 | 0:16:46 | |
-Fortunately for us, they are not -released straight from the sun... | 0:16:47 | 0:16:51 | |
-..or we'd be fried in an instant. | 0:16:52 | 0:16:54 | |
-After its birth as a gamma ray... | 0:16:57 | 0:16:59 | |
-..our photon races out from the -sun's core at the speed of light. | 0:17:00 | 0:17:05 | |
-But it encounters an obstacle. | 0:17:07 | 0:17:09 | |
-A journey that should take seconds -slows down to a cosmic crawl. | 0:17:12 | 0:17:16 | |
-Photons should take a few seconds -to escape from the sun's core. | 0:17:19 | 0:17:24 | |
-It actually takes -hundreds of thousands of years. | 0:17:24 | 0:17:28 | |
-What could possibly slow a photon -moving at the speed of light? | 0:17:31 | 0:17:36 | |
-Something slams on the brakes. | 0:17:39 | 0:17:41 | |
-Something hot, dense and huge. | 0:17:42 | 0:17:45 | |
-So powerful, it doesn't just -slow light, it transforms it. | 0:17:48 | 0:17:53 | |
-The sun is a massive ball of gas. | 0:17:58 | 0:18:00 | |
-The photon must travel through -several layers within the sun... | 0:18:01 | 0:18:06 | |
-..before it can be released -into space. | 0:18:06 | 0:18:09 | |
-Our newborn photon leaves the core -at the speed of light... | 0:18:14 | 0:18:18 | |
-..only to run into a dense soup -of hydrogen atoms. | 0:18:22 | 0:18:25 | |
-A photon's nightmare. | 0:18:25 | 0:18:27 | |
-A nightmare that stretches -for over 400,000 miles. | 0:18:27 | 0:18:31 | |
-The radiation zone -surrounds the sun's core. | 0:18:39 | 0:18:43 | |
-This zone is made of hydrogen gas, -but not a gas as we think of it. | 0:18:45 | 0:18:50 | |
-The weight of all the material above -compresses the radiation zone... | 0:18:51 | 0:18:56 | |
-..until it's denser than lead and -nearly impossible to pass through. | 0:18:56 | 0:19:01 | |
-If a photon travelled straight from -the sun's centre to its surface... | 0:19:05 | 0:19:10 | |
-..it would take ten seconds. | 0:19:11 | 0:19:13 | |
-But it takes -between 100,000 and 200,000 years. | 0:19:13 | 0:19:16 | |
-It goes on a very long journey. | 0:19:17 | 0:19:19 | |
-The gases are dense and hot. | 0:19:19 | 0:19:22 | |
-Superheated to over -12.5 million degrees Fahrenheit... | 0:19:24 | 0:19:28 | |
-..the gas in the radiation zone... | 0:19:28 | 0:19:30 | |
-..is transformed into plasma - -the fourth state of matter. | 0:19:31 | 0:19:35 | |
-Atoms in normal matter have -a nucleus with orbiting electrons. | 0:19:37 | 0:19:41 | |
-In plasma, -the atoms have been torn apart... | 0:19:44 | 0:19:48 | |
-..and the electrons ripped away. | 0:19:48 | 0:19:50 | |
-We're familiar with -the three main states of matter... | 0:19:53 | 0:19:56 | |
-..liquids, solids and gases. | 0:19:57 | 0:19:59 | |
-We drink liquids, we breathe gases -and we eat solids. | 0:19:59 | 0:20:03 | |
-But there's a fourth, which is -the most common in the universe... | 0:20:03 | 0:20:08 | |
-..and it's called plasma. | 0:20:08 | 0:20:10 | |
-Compared to the rest of the cosmos, -earth is a calm and safe place. | 0:20:15 | 0:20:20 | |
-But plasma is also created here -inside a lightning strike. | 0:20:24 | 0:20:28 | |
-Temperatures inside a lightning bolt -can reach 53,000 degrees Fahrenheit. | 0:20:37 | 0:20:42 | |
-Enough to momentarily -rip a few atoms apart. | 0:20:42 | 0:20:46 | |
-The plasma lasts an instant... | 0:20:48 | 0:20:50 | |
-..then the electrons rebind -and it's gone. | 0:20:51 | 0:20:54 | |
-But in our massive sun, the plasma -lasts for billions of years... | 0:20:58 | 0:21:03 | |
-..and makes up the entire -200,000 mile deep radiation zone. | 0:21:03 | 0:21:07 | |
-Worse for our photon, -the plasma is electrically charged. | 0:21:10 | 0:21:14 | |
-This forms a cosmic trap. | 0:21:14 | 0:21:16 | |
-A photon collides with a proton -or electron... | 0:21:19 | 0:21:23 | |
-..and some of the energy -of the photon... | 0:21:24 | 0:21:26 | |
-..is transferred to the proton -or electron. | 0:21:27 | 0:21:30 | |
-What that means is the plasma -then becomes hotter and hotter. | 0:21:30 | 0:21:35 | |
-Light interacts more strongly with -electronically charged objects... | 0:21:35 | 0:21:39 | |
-..than with neutral objects. | 0:21:39 | 0:21:41 | |
-When you have a neutral atom, -light can pass by. | 0:21:41 | 0:21:44 | |
-But separate -the positive and negative charges... | 0:21:44 | 0:21:47 | |
-..and light can't make it through. | 0:21:47 | 0:21:49 | |
-Our photon, in the form of a gamma -ray, has entered the radiation zone. | 0:21:51 | 0:21:56 | |
-It then smashes -into charged plasma particles. | 0:21:56 | 0:22:00 | |
-For a fraction of a second, -the particle absorbs the photon... | 0:22:02 | 0:22:06 | |
-..then spits it back out... | 0:22:06 | 0:22:08 | |
-..and the photon -collides with another particle. | 0:22:09 | 0:22:12 | |
-The charged plasma particles -make it difficult for the photon... | 0:22:12 | 0:22:17 | |
-..to work its way out of the sun -to the surface. | 0:22:18 | 0:22:21 | |
-The photon loses -some of its original energy. | 0:22:24 | 0:22:27 | |
-The dense plasma makes it difficult -for the photon to reach the surface. | 0:22:27 | 0:22:32 | |
-It's an atomic game of basketball. | 0:22:35 | 0:22:37 | |
-The court is the radiation zone. | 0:22:40 | 0:22:42 | |
-The players -are the particles in the plasma... | 0:22:43 | 0:22:46 | |
-..and the ball is the photon. | 0:22:48 | 0:22:50 | |
-You can imagine the photon -as the ball. | 0:22:50 | 0:22:53 | |
-The ball is passed -from one player to the next. | 0:22:54 | 0:22:58 | |
-This happens very quickly -and in a really random pattern. | 0:23:00 | 0:23:06 | |
-But the ball will gradually make its -way to the other side of the court. | 0:23:11 | 0:23:16 | |
-The photon wants the quickest route -up the court... | 0:23:22 | 0:23:25 | |
-..but it's thrown, -slowing its progress. | 0:23:26 | 0:23:29 | |
-This process transforms the photon. | 0:23:32 | 0:23:36 | |
-As the photon is thrown from -one electron or proton to another... | 0:23:40 | 0:23:45 | |
-..it loses energy. | 0:23:46 | 0:23:47 | |
-It turns from being -a very powerful gamma ray... | 0:23:48 | 0:23:52 | |
-..to something with less energy, -like X-ray or ultraviolet. | 0:23:52 | 0:23:56 | |
-Over hundreds of thousands -of years... | 0:24:00 | 0:24:03 | |
-..the photon keeps bouncing -through the dense radiation zone. | 0:24:03 | 0:24:08 | |
-Each collision -takes away some energy... | 0:24:09 | 0:24:12 | |
-..transforming it -from a lethal gamma ray photon... | 0:24:15 | 0:24:18 | |
-..to a lower energy X-ray. | 0:24:19 | 0:24:21 | |
-Almost a million years -after its creation in the core... | 0:24:27 | 0:24:31 | |
-..the photon has made it -through the radiation zone. | 0:24:31 | 0:24:35 | |
-But there's no escape and it's about -to start another difficult journey. | 0:24:36 | 0:24:41 | |
-This happens in a place so violent, -it makes the sun roar. | 0:24:45 | 0:24:50 | |
-. | 0:24:55 | 0:24:56 | |
-Subtitles | 0:25:01 | 0:25:01 | |
-Subtitles - -Subtitles | 0:25:01 | 0:25:03 | |
-We're following -a tiny piece of light a photon... | 0:25:14 | 0:25:19 | |
-..on its journey towards earth. | 0:25:19 | 0:25:21 | |
-A journey -that will sustain all our lives. | 0:25:22 | 0:25:25 | |
-A million year journey... | 0:25:27 | 0:25:29 | |
-..which is nearing its end. | 0:25:33 | 0:25:35 | |
-Battered and sapped of energy... | 0:25:37 | 0:25:39 | |
-..it has changed -from a deadly gamma ray to an X-ray. | 0:25:40 | 0:25:44 | |
-But it now enters -a mysterious layer of the sun. | 0:25:46 | 0:25:50 | |
-The convection zone. | 0:25:52 | 0:25:53 | |
-The convection zone... | 0:25:56 | 0:25:58 | |
-..lies between the radiation zone -and the sun's surface. | 0:25:58 | 0:26:02 | |
-We can't see this zone -with our telescopes. | 0:26:05 | 0:26:08 | |
-But we can hear it. | 0:26:10 | 0:26:11 | |
-NASA's Solar Dynamics Observatory -listens to the sun. | 0:26:17 | 0:26:23 | |
-The sound it picks up -is too deep for humans to hear. | 0:26:23 | 0:26:27 | |
-But if you speed up forty days' -recording into a few seconds... | 0:26:27 | 0:26:33 | |
-..this is what you get. | 0:26:33 | 0:26:35 | |
-The sound of chaos. | 0:26:40 | 0:26:41 | |
-As we can't see into the sun, -its sound is vital to scientists. | 0:26:49 | 0:26:53 | |
-When a gun fires, the bullet -rushes out and smashes into air... | 0:26:56 | 0:27:01 | |
-..creating waves of turbulence. | 0:27:01 | 0:27:04 | |
-We hear the gun firing when -these waves vibrate our eardrums. | 0:27:05 | 0:27:10 | |
-What we can see here is sound. | 0:27:15 | 0:27:17 | |
-The sun works the same way, -on a much larger scale. | 0:27:20 | 0:27:23 | |
-When we see waves moving across... | 0:27:26 | 0:27:28 | |
-..we see material moving up from -inside the sun and it makes noise. | 0:27:29 | 0:27:34 | |
-It's like it ran into a wall -and it generates sound... | 0:27:34 | 0:27:38 | |
-..and we see that sound -moving all around the sun. | 0:27:38 | 0:27:42 | |
-Sound waves crashing through plasma -create ripples in the sun's surface. | 0:27:43 | 0:27:48 | |
-All we see are these ripples. | 0:27:49 | 0:27:52 | |
-Those are the sound waves -of the sun. | 0:27:52 | 0:27:54 | |
-They move around inside the sun -and back up to the surface. | 0:27:55 | 0:27:59 | |
-By tracking the sound, -scientists can see into the sun. | 0:28:03 | 0:28:07 | |
-They pick up sound waves smashing -against the sun's surface... | 0:28:08 | 0:28:12 | |
-..and resonating -throughout the interior. | 0:28:12 | 0:28:15 | |
-This reveals a violent, -boiling convection zone. | 0:28:18 | 0:28:21 | |
-In a similar way to earthquakes, you -can feel the waves travelling along. | 0:28:23 | 0:28:28 | |
-The same happens on the sun. | 0:28:30 | 0:28:33 | |
-It's possible -to look at one point... | 0:28:33 | 0:28:36 | |
-..and measure in which direction -these waves are travelling. | 0:28:36 | 0:28:41 | |
-By mapping it, we can measure waves -travelling on the sun's surface... | 0:28:43 | 0:28:48 | |
-..so there's a noise inside the sun. | 0:28:49 | 0:28:51 | |
-Columns of gases rise and fall. | 0:28:53 | 0:28:56 | |
-The sun's convection zone is very -similar to a pan of water boiling. | 0:28:59 | 0:29:04 | |
-Some bubbles of gas or plasma -are hotter than others... | 0:29:06 | 0:29:10 | |
-..and those rise to the top. | 0:29:10 | 0:29:12 | |
-The colder bubbles -sink to the bottom. | 0:29:13 | 0:29:16 | |
-At the bottom -of the convection zone... | 0:29:18 | 0:29:21 | |
-..photons smash into atoms -in the plasma... | 0:29:22 | 0:29:25 | |
-..heating them to a boil. | 0:29:25 | 0:29:27 | |
-Next, the atoms -absorb the photons... | 0:29:27 | 0:29:30 | |
-..and they ride the boiling current -to the top. | 0:29:32 | 0:29:36 | |
-The hot atoms -drag the photons with them. | 0:29:37 | 0:29:40 | |
-Within the convection zone... | 0:29:42 | 0:29:44 | |
-..photons that collide with atoms -are carried up with the bubbles. | 0:29:45 | 0:29:50 | |
-Suddenly, their journey is easier. | 0:29:53 | 0:29:56 | |
-It's still a random route but it -does take them to the sun's surface. | 0:29:56 | 0:30:01 | |
-Our photon is now in the hands of -a single player making a fast break. | 0:30:05 | 0:30:10 | |
-In the convection layer, it's as if -one player has held onto the ball... | 0:30:12 | 0:30:17 | |
-..and is going -straight for the basket... | 0:30:17 | 0:30:20 | |
-..carrying the ball with it. | 0:30:21 | 0:30:23 | |
-The atom carries the ball -up the court rapidly. | 0:30:25 | 0:30:30 | |
-The photon's journey through the -convection zone takes just a week. | 0:30:33 | 0:30:38 | |
-But, again, the photon transforms. | 0:30:38 | 0:30:41 | |
-The bottom of the convection zone -is incredibly hot. | 0:30:44 | 0:30:47 | |
-At the top, the temperature falls. | 0:30:51 | 0:30:53 | |
-So as the photon rises up, -it cools, losing energy... | 0:30:56 | 0:31:00 | |
-..and changes from an energetic -X-ray to a light we can see. | 0:31:01 | 0:31:06 | |
-It loses some of its energy -due to the temperature drop. | 0:31:10 | 0:31:13 | |
-The nature of the photon -depends on the temperature. | 0:31:14 | 0:31:18 | |
-It goes from being an X-ray photon -to being an ultraviolet photon... | 0:31:18 | 0:31:23 | |
-..or a photon -we can see with the naked eye. | 0:31:23 | 0:31:26 | |
-At the top of the convection zone, -the atom releases the photon... | 0:31:29 | 0:31:34 | |
-..which shoots out as visible light. | 0:31:34 | 0:31:37 | |
-This cools the atoms, which fall -back down to absorb more photons... | 0:31:39 | 0:31:44 | |
-..then they heat up and rise again. | 0:31:45 | 0:31:48 | |
-The photon is ready to be released -from the sun's surface... | 0:31:51 | 0:31:55 | |
-..but the convection zone -unleashes another force. | 0:31:55 | 0:31:59 | |
-A force that powers huge storms, -detonates bombs... | 0:32:00 | 0:32:04 | |
-..and threatens -to stop our light from escaping. | 0:32:05 | 0:32:08 | |
-Finally, it has reached the shell -of the sun - the photosphere. | 0:32:14 | 0:32:20 | |
-The photosphere -is the sun's outer layer. | 0:32:25 | 0:32:28 | |
-When we look at the sun, -what we see is the photosphere. | 0:32:29 | 0:32:33 | |
-Behind this outer shell -lies a spectacular and savage world. | 0:32:35 | 0:32:41 | |
-This image of the sun was taken -in an extreme ultraviolet light... | 0:32:46 | 0:32:51 | |
-..which is close to X-ray. | 0:32:51 | 0:32:53 | |
-Suddenly, instead of being -a calm white ball... | 0:32:54 | 0:32:58 | |
-..we see a surface -that's full of activity. | 0:32:58 | 0:33:01 | |
-Look closely at the photosphere -and you'll see... | 0:33:03 | 0:33:06 | |
-..it's like the surface -of boiling water in a saucepan. | 0:33:06 | 0:33:11 | |
-We can see cells -constantly rising and falling. | 0:33:11 | 0:33:14 | |
-It's terrifying -to look at the sun like this. | 0:33:16 | 0:33:19 | |
-The realization hits you that we -exist close to a very active star. | 0:33:20 | 0:33:24 | |
-It has so much energy -it's terrifying. | 0:33:26 | 0:33:29 | |
-It's a huge hydrogen bomb -in our back garden. | 0:33:30 | 0:33:34 | |
-The surface of the sun -is a turbulent barrier. | 0:33:39 | 0:33:42 | |
-Once again, -our photon is taken hostage. | 0:33:44 | 0:33:48 | |
-At Kitt Peak Observatory, Arizona, -solar astronomer Matt Penn... | 0:33:55 | 0:34:00 | |
-..studies the solar surface to see -how photons of light get trapped. | 0:34:00 | 0:34:05 | |
-Using the McMath-Pierce Telescope, -he focuses the sun's light... | 0:34:15 | 0:34:20 | |
-..to scan the photosphere in detail. | 0:34:21 | 0:34:24 | |
-What we've got -are a few small sunspots. | 0:34:25 | 0:34:27 | |
-Two large sunspots -are heading to the edge of the sun. | 0:34:28 | 0:34:31 | |
-To the limb of the sun. | 0:34:32 | 0:34:33 | |
-But they're all accompanied -by groups of smaller sunspots. | 0:34:34 | 0:34:38 | |
-Sunspots mark out areas -where light is trapped. | 0:34:41 | 0:34:45 | |
-A sunspot forms a dark spot... | 0:34:46 | 0:34:49 | |
-..by removing energy -from that part of the sun. | 0:34:49 | 0:34:52 | |
-It blocks convective fluids -that transport heat and light... | 0:34:52 | 0:34:56 | |
-..from inside the sun to space. | 0:34:56 | 0:34:58 | |
-We see a cooler region -that appears dark to us. | 0:34:59 | 0:35:02 | |
-A powerful force stops our photon -from leaving the sun's surface. | 0:35:06 | 0:35:10 | |
-Sunspots take shape where magnetism -from deep inside the sun... | 0:35:22 | 0:35:27 | |
-..blasts up through the photosphere. | 0:35:27 | 0:35:30 | |
-Where the magnetic field -comes through the photosphere... | 0:35:32 | 0:35:36 | |
-..there are cooler areas which are -5,000 degrees rather than 6,000. | 0:35:37 | 0:35:41 | |
-They then appear darker, -creating these sunspots. | 0:35:42 | 0:35:46 | |
-They can be huge. | 0:35:48 | 0:35:50 | |
-The largest are more than -ten times the size of the earth. | 0:35:51 | 0:35:55 | |
-The magnetism -that generates sunspots... | 0:35:59 | 0:36:02 | |
-..forms field lines -covering the sun. | 0:36:02 | 0:36:04 | |
-On our solid earth, -the whole planet rotates together... | 0:36:06 | 0:36:10 | |
-..including its magnetic field. | 0:36:11 | 0:36:13 | |
-But the sun is a big ball of gas -and the same rules don't apply. | 0:36:15 | 0:36:20 | |
-The sun is a ball of gas... | 0:36:21 | 0:36:23 | |
-..so different parts -rotate at different speeds. | 0:36:23 | 0:36:27 | |
-When a magnetic field moves out -of the photosphere and into space... | 0:36:27 | 0:36:32 | |
-..some parts travel -at different speeds. | 0:36:32 | 0:36:35 | |
-This stretches and pulls the -magnetic field, creating energy. | 0:36:37 | 0:36:42 | |
-The sun rotates faster -at the equator than at the poles... | 0:36:46 | 0:36:50 | |
-..twisting and tangling its -magnetic field with each rotation. | 0:36:51 | 0:36:55 | |
-The result is mayhem. | 0:36:57 | 0:36:58 | |
-The movements -of the magnetic fields... | 0:37:04 | 0:37:07 | |
-..being dragged by movement -in the photosphere creates energy. | 0:37:07 | 0:37:12 | |
-It builds up and it twists -until it almost breaks. | 0:37:13 | 0:37:16 | |
-It's like a complicated knot. | 0:37:17 | 0:37:20 | |
-Where the magnetic lines twist... | 0:37:22 | 0:37:24 | |
-..flows of plasma containing -our photon can't reach the surface. | 0:37:25 | 0:37:30 | |
-A patch of the sun goes dark -where light can't escape. | 0:37:35 | 0:37:40 | |
-A sunspot is created. | 0:37:42 | 0:37:44 | |
-But in the tangle of magnetic lines, -something has to snap. | 0:37:46 | 0:37:51 | |
-Sometimes there's too much tension -and something gives... | 0:37:51 | 0:37:55 | |
-..creating an explosion. | 0:37:57 | 0:37:59 | |
-Huge loops of magnetic energy -arc out over the sunspots... | 0:38:01 | 0:38:05 | |
-..twisted and ready -to be untangled... | 0:38:08 | 0:38:11 | |
-..like a magnetic bomb -which is ready to explode. | 0:38:12 | 0:38:15 | |
-The energy and tension -in the magnetic field... | 0:38:18 | 0:38:21 | |
-..is desperate to be released. | 0:38:23 | 0:38:26 | |
-This usually happens -in an explosion. | 0:38:26 | 0:38:29 | |
-The sun's surface explodes. -We call it a coronal mass ejection. | 0:38:43 | 0:38:47 | |
-These explosions from the sun's -surface create the Northern Lights. | 0:38:48 | 0:38:53 | |
-Solar flares erupt into space, -releasing massive amounts of energy. | 0:39:00 | 0:39:05 | |
-Each explosion is like tens of -thousands of huge nuclear bombs... | 0:39:12 | 0:39:16 | |
-..being detonated simultaneously. | 0:39:16 | 0:39:19 | |
-They can contain -billions of tons of hot plasma... | 0:39:21 | 0:39:27 | |
-..at a temperature -of over one million degrees. | 0:39:28 | 0:39:32 | |
-All this is thrown out into space... | 0:39:33 | 0:39:36 | |
-..at speeds of around -1,000 kilometres per second. | 0:39:36 | 0:39:39 | |
-You can imagine this huge thing -being hurled into space. | 0:39:41 | 0:39:45 | |
-After nearly a million years, our -packet of light makes its escape. | 0:39:49 | 0:39:54 | |
-It is finally free... | 0:39:58 | 0:39:59 | |
-..catapulting out along with -trillions of other photons. | 0:40:00 | 0:40:05 | |
-But their journey is far from over. | 0:40:05 | 0:40:08 | |
-Most photons hurtle onwards -to the far reaches of the cosmos. | 0:40:09 | 0:40:14 | |
-To new worlds. | 0:40:14 | 0:40:16 | |
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-Subtitles | 0:40:26 | 0:40:26 | |
-Subtitles - -Subtitles | 0:40:26 | 0:40:28 | |
-It takes nearly a million years for -tiny parcels of light photons... | 0:40:34 | 0:40:39 | |
-..to finally burst -from the sun's surface. | 0:40:40 | 0:40:43 | |
-Suddenly, it's free -to travel through space... | 0:40:56 | 0:40:59 | |
-..and to travel -through the universe. | 0:41:00 | 0:41:02 | |
-Photons shoot out into empty space -at the speed of light. | 0:41:11 | 0:41:15 | |
-After just eight minutes, -our photon reaches earth. | 0:41:19 | 0:41:23 | |
-Each step of the life of a photon... | 0:41:24 | 0:41:26 | |
-..from the moment it's created -in the sun's core... | 0:41:27 | 0:41:30 | |
-..to the moment it reaches our eyes -here, on earth... | 0:41:31 | 0:41:35 | |
-..is amazing. | 0:41:36 | 0:41:37 | |
-It's formed through a nuclear fusion -in the sun's core. | 0:41:38 | 0:41:42 | |
-It takes a random route -through the sun's core... | 0:41:43 | 0:41:47 | |
-..for hundreds of thousands -of years. | 0:41:47 | 0:41:50 | |
-It then exits the photosphere. | 0:41:51 | 0:41:54 | |
-It travels through space for -eight minutes and reaches our eyes. | 0:41:54 | 0:42:00 | |
-That's how -we can see everything around us. | 0:42:00 | 0:42:03 | |
-Our photon finally arrives... | 0:42:06 | 0:42:09 | |
-..smashes into a leaf -and passes on its energy. | 0:42:09 | 0:42:13 | |
-This is photosynthesis - the -fundamental link in our food chain. | 0:42:15 | 0:42:20 | |
-Carrying energy -born in the sun's core... | 0:42:23 | 0:42:26 | |
-..our photon starts life -on our planet. | 0:42:26 | 0:42:29 | |
-The sun's light creates our fuel -and drives our weather. | 0:42:32 | 0:42:36 | |
-Every single day, -enough photons hit the earth... | 0:42:44 | 0:42:47 | |
-..to power our civilization -for 27 years. | 0:42:47 | 0:42:51 | |
-The sun's light -is more than warmth and heat. | 0:42:53 | 0:42:55 | |
-Without light, we would not survive. | 0:42:59 | 0:43:01 | |
-Without the sun's heat, -which reaches us through photons... | 0:43:03 | 0:43:07 | |
-..any kind of life on earth -would not be possible. | 0:43:08 | 0:43:11 | |
-Trillions of photons -hit the earth every second. | 0:43:15 | 0:43:18 | |
-Many more pass us by, and for them, -the journey is far from over. | 0:43:22 | 0:43:27 | |
-Around 80 minutes after -leaving the sun, they reach Saturn. | 0:43:30 | 0:43:35 | |
-After four hours, -they reach Neptune. | 0:43:36 | 0:43:39 | |
-Only a small part of the light -that comes from the sun hits earth. | 0:43:43 | 0:43:47 | |
-The remainder carries on, going -further and further into the galaxy. | 0:43:47 | 0:43:52 | |
-In 18 hours, -they leave our solar system. | 0:43:55 | 0:43:58 | |
-The sun is now a dim speck -in the distance. | 0:44:00 | 0:44:03 | |
-But the photons keep going, -out into deep space. | 0:44:05 | 0:44:09 | |
-In 1,000 years, some of the photons -reach the Kepler 62 system... | 0:44:13 | 0:44:18 | |
-..another solar system... | 0:44:19 | 0:44:21 | |
-..with potentially habitable -earth-like planets. | 0:44:22 | 0:44:26 | |
-There are billions -of earth-like planets in our galaxy. | 0:44:26 | 0:44:31 | |
-If there is life here... | 0:44:32 | 0:44:33 | |
-..it's possible they could also -see the light from our sun. | 0:44:34 | 0:44:38 | |
-The sun is a star. | 0:44:41 | 0:44:42 | |
-It takes eight minutes for -the sun's light to reach the earth. | 0:44:42 | 0:44:47 | |
-But other photons -continue into space. | 0:44:47 | 0:44:49 | |
-People who live on other stars... | 0:44:50 | 0:44:52 | |
-..may be able to look back -and see our sun. | 0:44:52 | 0:44:55 | |
-In 1,500 years, the photon reaches -other distant parts of the cosmos... | 0:44:58 | 0:45:03 | |
-..like the Horsehead Nebula. | 0:45:04 | 0:45:06 | |
-In 7,000 years, -it passes the Pillars Of Creation. | 0:45:10 | 0:45:14 | |
-At these distances... | 0:45:17 | 0:45:19 | |
-..the light from our star can only -be seen with a powerful telescope. | 0:45:19 | 0:45:24 | |
-Modern telescopes have the capacity -to create huge mirrors... | 0:45:28 | 0:45:33 | |
-..to collect as much light -as possible... | 0:45:33 | 0:45:36 | |
-..so we can look further and further -into the universe. | 0:45:36 | 0:45:40 | |
-Because the light has taken -such a long time to reach us... | 0:45:42 | 0:45:46 | |
-..we can look deeper and deeper -in time. | 0:45:46 | 0:45:49 | |
-With a strong enough telescope... | 0:45:50 | 0:45:53 | |
-..we could see the light from a star -at the far end of the universe. | 0:45:53 | 0:45:59 | |
-Our tiny star is visible -across the universe... | 0:45:59 | 0:46:03 | |
-..if someone is looking. | 0:46:03 | 0:46:05 | |
-In exactly the same way -we look at distant stars... | 0:46:07 | 0:46:11 | |
-..anybody living on those stars -could look back on our sun... | 0:46:12 | 0:46:16 | |
-..and see -an ordinary-looking star. | 0:46:16 | 0:46:19 | |
-Deep inside our sun, the photon -started its remarkable journey. | 0:46:23 | 0:46:27 | |
-It took a million years -to escape the sun's grip... | 0:46:33 | 0:46:36 | |
-..to bring energy, heat and life -to our world. | 0:46:36 | 0:46:40 | |
-Like other stars, light from our sun -journeys through the universe... | 0:46:44 | 0:46:49 | |
-..spreading energy -throughout the cosmos. | 0:46:50 | 0:46:53 | |
-S4C subtitles by Eirlys A Jones | 0:47:29 | 0:47:32 | |
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