0:00:02 > 0:00:06I'm Jon Chase. Scientist, rapper, and maybe one day, space traveller.
0:00:06 > 0:00:08I'm going to be answering some big questions
0:00:08 > 0:00:10about space and the universe
0:00:10 > 0:00:14by exploring the science we see all around us, right here on Earth.
0:00:14 > 0:00:16If you want to get your head around space,
0:00:16 > 0:00:19here are some of the questions you need to ask.
0:00:26 > 0:00:28Have you ever stopped to think about
0:00:28 > 0:00:31where everything around us came from?
0:00:31 > 0:00:33It's a question as big as the universe itself.
0:00:33 > 0:00:36In order to make sense of where it came from,
0:00:36 > 0:00:39we need to understand the sheer scale of the universe.
0:00:39 > 0:00:43And I think I've got a wicked way to put that into perspective.
0:00:43 > 0:00:46I've come to Edinburgh armed with toilet roll
0:00:46 > 0:00:48and peppercorns to show you what I mean.
0:00:48 > 0:00:50Do you lot know how big the solar system is?
0:00:50 > 0:00:52- Big.- It's big, innit?
0:00:52 > 0:00:57- Yeah.- Right, basically if I took that as the Sun,
0:00:57 > 0:00:59Earth would be about 100 times smaller.
0:00:59 > 0:01:01We'll use these to represent different planets.
0:01:01 > 0:01:04I'm going show you lot how far Neptune is. That's the Sun.
0:01:04 > 0:01:07I'm going to use a special measuring device, bog roll.
0:01:07 > 0:01:11It's the most scientific. I got it from NASA. Nah, blatantly not.
0:01:11 > 0:01:13This is the distance from the Sun to Mercury, yeah?
0:01:13 > 0:01:15Closest planet to the Sun.
0:01:15 > 0:01:18There's Mercury, that little bad boy there.
0:01:18 > 0:01:20Does anyone know the order of the planets?
0:01:20 > 0:01:22Mercury, Venus, Earth, Mars, Saturn.
0:01:22 > 0:01:25- Uranus.- Jupiter.- Jupiter.- Uranus.
0:01:25 > 0:01:28Right. I'll give you the method that you'll never forget from now on.
0:01:28 > 0:01:30My very easy method just speeds up naming planets.
0:01:30 > 0:01:33If you can remember that My starts with an M, so it's Mercury.
0:01:33 > 0:01:35Very starts with a V, so it's Venus.
0:01:35 > 0:01:38Easy starts with an E, so it's Earth, you get my drift.
0:01:38 > 0:01:39My very easy method.
0:01:39 > 0:01:42Although Pluto's now been reclassified as a dwarf planet.
0:01:42 > 0:01:43There's Venus,
0:01:43 > 0:01:44Earth is at two-and-a-half,
0:01:44 > 0:01:46Mars is at four.
0:01:46 > 0:01:49So Venus is closer to Earth than Mars is. I thought Mars was closer.
0:01:49 > 0:01:52No. Yeah, Mars is a bit further. See, you're surprised, innit?
0:01:52 > 0:01:55We could go to Venus, but the thing about Venus,
0:01:55 > 0:01:57it's a rubbish planet to go to. It smells of farts.
0:01:57 > 0:01:59I'm not joking! It smells of rotten eggs,
0:01:59 > 0:02:02it's 400 degrees and it rains acid. Venus is rubbish. Go to Mars.
0:02:02 > 0:02:06The next planet, Jupiter, is at 13. Let's go to Saturn.
0:02:08 > 0:02:11And remember, this is all if the Sun was this big.
0:02:12 > 0:02:17Uranus, as you can see, it's twice as far, as far as Saturn.
0:02:17 > 0:02:19This is how far Neptune is.
0:02:21 > 0:02:26Right. So as you can see, at this scale, space gets really big.
0:02:26 > 0:02:27If you wanted to see the nearest star,
0:02:27 > 0:02:29you'd have to have it in Glasgow.
0:02:29 > 0:02:33And in this model, the distance from our peppercorn Sun in Edinburgh
0:02:33 > 0:02:35to the furthest point in our galaxy
0:02:35 > 0:02:37would mean rolling out toilet paper
0:02:37 > 0:02:38to the Moon and back.
0:02:38 > 0:02:39It's hard to imagine,
0:02:39 > 0:02:41but our solar system is just
0:02:41 > 0:02:43a tiny part of our universe
0:02:43 > 0:02:45that evolved over billions of years.
0:02:46 > 0:02:48To find out where the universe came from,
0:02:48 > 0:02:51it helps to know a bit about where it's going.
0:02:56 > 0:02:59You can get an idea about the movements of the universe
0:02:59 > 0:03:01by visiting a racetrack like this.
0:03:03 > 0:03:05ENGINE REVS
0:03:05 > 0:03:06When the car comes closer,
0:03:06 > 0:03:09the pitch of the engine appears to get higher.
0:03:11 > 0:03:13As the car travels away from me,
0:03:13 > 0:03:16the pitch appears to be lower.
0:03:17 > 0:03:19You can hear the same thing
0:03:19 > 0:03:22when an ambulance drives past with its siren on.
0:03:22 > 0:03:23SIREN WAILS
0:03:23 > 0:03:26And this is called the Doppler Effect.
0:03:26 > 0:03:28Sound travels in waves.
0:03:28 > 0:03:30When the car is coming towards me,
0:03:30 > 0:03:32the waves appear to be closer together.
0:03:32 > 0:03:34As they travel away from me,
0:03:34 > 0:03:37there are fewer waves arriving to me each second,
0:03:37 > 0:03:38so the pitch appears to drop.
0:03:41 > 0:03:43Light also travels in waves.
0:03:43 > 0:03:47When a light source moves away from an object at high speed,
0:03:47 > 0:03:49the light looks redder.
0:03:49 > 0:03:52Waves from a receding star have further to travel
0:03:52 > 0:03:53to reach the object,
0:03:53 > 0:03:55so appear to have a longer wavelength...
0:03:56 > 0:03:59..or are red shifted.
0:03:59 > 0:04:03Because you only see red shift in objects travelling away from you,
0:04:03 > 0:04:07when scientists observed distant galaxies and found that they were also red shifted,
0:04:07 > 0:04:12it proved that the space between everything in the universe was expanding.
0:04:12 > 0:04:15If you imagine that this balloon is the actual fabric of space
0:04:15 > 0:04:19and each one of these dots is a different galaxy.
0:04:19 > 0:04:21As it expands...
0:04:25 > 0:04:27..the dots get further apart.
0:04:27 > 0:04:30If they're getting further apart over time,
0:04:30 > 0:04:33it must mean that at some time in history,
0:04:33 > 0:04:36all of these dots were closer together.
0:04:39 > 0:04:43And at this point, when they were all really close together,
0:04:43 > 0:04:47is what we see as the beginning of our universe.
0:04:47 > 0:04:51Most scientists believe that the whole universe began
0:04:51 > 0:04:54in an explosion about 14 billion years ago.
0:04:55 > 0:04:58This is known as the Big Bang theory
0:04:58 > 0:05:01and states that originally, all the matter in the universe
0:05:01 > 0:05:04was concentrated in a single point.
0:05:04 > 0:05:09So we can see the effects of the Big Bang, but we can also hear them.
0:05:09 > 0:05:12Scientists have discovered microwaves and radio waves
0:05:12 > 0:05:14coming from every direction in space.
0:05:14 > 0:05:19This is called Cosmic Microwave Background Radiation,
0:05:19 > 0:05:22or CMBR.
0:05:23 > 0:05:26CMBR comes from light created at the beginning of the universe,
0:05:26 > 0:05:29which, as the universe has expanded,
0:05:29 > 0:05:32has been stretched into microwaves and radio waves.
0:05:32 > 0:05:361% of the static I'm picking up is radio waves,
0:05:36 > 0:05:38which are part of the CMBR.
0:05:38 > 0:05:41So even though it's the part of the radio you never want to listen to,
0:05:41 > 0:05:44the part that you're least interested in,
0:05:44 > 0:05:47it's still really amazing to think that actually,
0:05:47 > 0:05:50that's the sound of the beginning of the universe
0:05:50 > 0:05:54almost 14 billion years ago.
0:05:54 > 0:05:57It's impossible to deny the huge impact of red shift
0:05:57 > 0:06:01on our understanding of where everything in the universe came from.
0:06:01 > 0:06:05So if we know that galaxies are moving away from each other,
0:06:05 > 0:06:09maybe the next big question is, where are we all headed?
0:06:20 > 0:06:26In the 1950s, scientists first started testing a new type of bomb
0:06:26 > 0:06:291,000 times more powerful than the atomic fission bomb
0:06:29 > 0:06:31dropped on Hiroshima during the Second World War.
0:06:31 > 0:06:34Four...three...two...one.
0:06:34 > 0:06:37BOOM!
0:06:38 > 0:06:40It was called the hydrogen bomb
0:06:40 > 0:06:42and it was the first time mankind had recreated
0:06:42 > 0:06:44the way the Sun makes its energy.
0:06:44 > 0:06:46Now, as massive as this bomb was,
0:06:46 > 0:06:50the energy it released was only a tiny fraction
0:06:50 > 0:06:55of the massive amounts of energy released by the Sun every second.
0:06:55 > 0:06:57BOOM!
0:06:58 > 0:07:01This demonstration is to help us try and show you
0:07:01 > 0:07:04how energy is produced in a star like our Sun.
0:07:04 > 0:07:08Obviously, we couldn't give you an exact reaction that happens on the Sun.
0:07:08 > 0:07:10That would produce so much energy,
0:07:10 > 0:07:14you'd probably blow up your school, if not half of this country.
0:07:14 > 0:07:17So we're going to give you a representative demonstration right here.
0:07:17 > 0:07:19- You lot ready for this?- ALL: Yeah.
0:07:19 > 0:07:22We're going to have to step a bit back because it will get really hot.
0:07:22 > 0:07:26And we have to make sure we've got our goggles ready just in case.
0:07:26 > 0:07:29Now, this looks a lot better in the dark, so let's give it ten minutes.
0:07:29 > 0:07:32TICKING
0:07:32 > 0:07:35This reaction of iron oxide and aluminium powder
0:07:35 > 0:07:39will create loads of energy in the form of heat and light.
0:07:39 > 0:07:43It can help us imagine the way the Sun gives off heat and light,
0:07:43 > 0:07:45but on a slightly different scale.
0:07:45 > 0:07:47THEY GASP
0:07:49 > 0:07:53- Was that pretty cool?- ALL: Yeah!
0:07:53 > 0:07:55So what we just saw there was a chemical reaction.
0:07:55 > 0:07:58But when you look at a star,
0:07:58 > 0:08:02the reactions that go on inside isn't a chemical reaction.
0:08:02 > 0:08:04It's actually a reaction called nuclear fusion.
0:08:04 > 0:08:11Nuclear fusion involves light atomic nuclei fusing to form heavier ones.
0:08:11 > 0:08:13The two nuclei are both hydrogen
0:08:13 > 0:08:16and they join to form one helium nucleus.
0:08:16 > 0:08:17In our demonstration,
0:08:17 > 0:08:20the heat produced by the flame started the reaction.
0:08:20 > 0:08:24In a star, the reaction is started by gravity.
0:08:24 > 0:08:29The force squeezes all the hydrogen at the centre of a star so tight
0:08:29 > 0:08:32that it gets hot enough for their nuclei to collide together
0:08:32 > 0:08:36with enough energy and speed to start fusing into helium.
0:08:36 > 0:08:39In this process, more energy is released.
0:08:39 > 0:08:43So in this reaction, it soared up to temperatures in excess of...
0:08:43 > 0:08:46Actually, let me see what your kind of guesses are.
0:08:46 > 0:08:48What type of temperatures do you think it was?
0:08:48 > 0:08:52- 1,000.- 1,000?- 2,000.- 2,000? - 3,000.- 3,000?
0:08:52 > 0:08:54Exactly!
0:08:54 > 0:08:57You lot are on the ball, aren't you? 3,000 degrees Celsius.
0:08:57 > 0:09:01But in a nuclear reaction inside a star,
0:09:01 > 0:09:06temperatures are actually in excess of 15 million degrees Celsius.
0:09:06 > 0:09:11That's about 5,000 times hotter than this reaction that just went off.
0:09:11 > 0:09:13- Impressed?- ALL: Yeah.
0:09:13 > 0:09:17And it's so hot that it's enough to burn through the metal of this can.
0:09:17 > 0:09:20I'm going to pull it off now that it's cooled down a bit.
0:09:20 > 0:09:23We've had it here for a while.
0:09:23 > 0:09:27So that was the top of the can and this is the bottom of the can.
0:09:29 > 0:09:32When scientists tested the hydrogen bomb,
0:09:32 > 0:09:36they weren't able to control the amount of heat and light released.
0:09:36 > 0:09:39This made it a massive uncontrolled explosion.
0:09:39 > 0:09:43If scientists were able to carry out nuclear fusion in a controlled way,
0:09:43 > 0:09:48it would solve all our energy needs in one go.
0:09:48 > 0:09:54the Sun produces 400 trillion trillion watts of power each second.
0:09:54 > 0:09:58That means in a single second, the Sun produces enough energy
0:09:58 > 0:10:02to supply the whole Earth with power for half a million years.
0:10:02 > 0:10:07So stars are like massive nuclear reactors.
0:10:07 > 0:10:09They're fuelled by nuclear fusion,
0:10:09 > 0:10:12which releases huge amounts of energy,
0:10:12 > 0:10:15keeping the reaction alive so the star shines brightly in our sky.
0:10:17 > 0:10:21So inside a star, it's like a billion hydrogen bombs
0:10:21 > 0:10:23going off every second.
0:10:23 > 0:10:27Man, that's immense!
0:10:27 > 0:10:29BOOM!
0:10:42 > 0:10:45Our closest star is the Sun.
0:10:45 > 0:10:48And it's one of many billions of stars
0:10:48 > 0:10:51in the galaxy we know as the Milky Way.
0:10:51 > 0:10:56Just like people, stars are born, they live and then they die.
0:10:57 > 0:11:00- Have any of you lot played Jenga before?- ALL: YEAH.
0:11:00 > 0:11:02Yeah, you've played then? Right.
0:11:02 > 0:11:06This actual stack represents a star in the main part of its life cycle.
0:11:06 > 0:11:08We call it the main sequence.
0:11:08 > 0:11:13And that's the part where the star's forces inside it are stable.
0:11:13 > 0:11:16And that basically means that when it creates all its energy
0:11:16 > 0:11:19like heat and light that you see coming from the Sun,
0:11:19 > 0:11:21it pushes out with an outward pressure on the star
0:11:21 > 0:11:23and it tries to blow the star apart.
0:11:23 > 0:11:25But the star has got so much mass
0:11:25 > 0:11:27that's trying to pull it together with gravity.
0:11:27 > 0:11:31That pulling together versus the pressure pushing out
0:11:31 > 0:11:33eventually gets in a balance.
0:11:33 > 0:11:35You get an equilibrium.
0:11:35 > 0:11:37Each one of these pieces,
0:11:37 > 0:11:40each one of these blocks represents a bit of energy.
0:11:40 > 0:11:45So the idea is to try and see how much energy we can release
0:11:45 > 0:11:47before it becomes unstable
0:11:47 > 0:11:49and everything comes falling to the floor.
0:11:49 > 0:11:53And then you lose...and I win.
0:11:54 > 0:11:56The energy released by the star through nuclear fusion
0:11:56 > 0:11:59creates an outward pressure.
0:11:59 > 0:12:02The force of gravity acting on the star's mass
0:12:02 > 0:12:04creates an inward pressure.
0:12:04 > 0:12:08In the main sequence, these two forces are balanced.
0:12:11 > 0:12:13This is the main sequence and the star will spend about
0:12:13 > 0:12:1590 percent of its life doing this,
0:12:15 > 0:12:17just slowly giving off energy.
0:12:17 > 0:12:21And as long as gravity's balanced, we have equilibrium.
0:12:21 > 0:12:24Oh-oh-oh-oh. Wow!
0:12:24 > 0:12:27So as you can see, it's taking a while, isn't it?
0:12:27 > 0:12:30Different stars do this at different rates.
0:12:30 > 0:12:33So big stars use up all their energy really quickly,
0:12:33 > 0:12:35they just kind of throw it all out, eject it.
0:12:35 > 0:12:38There we go, energy's gone. Boom!
0:12:38 > 0:12:43The smaller stars can stay on the main sequence for, like, a billion years,
0:12:43 > 0:12:44maybe even billions of years.
0:12:44 > 0:12:49So our Sun is a few billion years old and it's in its main sequence.
0:12:49 > 0:12:51EXCITED CHATTER
0:12:51 > 0:12:53It's looking very precarious here.
0:12:53 > 0:12:54The star's about to end its life.
0:12:54 > 0:12:57It's inevitable, you can't avoid it.
0:12:57 > 0:13:00All stars eventually run out of the fuel they're burning,
0:13:00 > 0:13:02it's just a question of when.
0:13:02 > 0:13:04Whoo!
0:13:04 > 0:13:07Another gravitational collapse of the core.
0:13:07 > 0:13:10Gravity wins!
0:13:10 > 0:13:13That marks the end of a star.
0:13:13 > 0:13:15It's released so much energy
0:13:15 > 0:13:16that now, it can't balance
0:13:16 > 0:13:19the gravity that's pulling it together.
0:13:19 > 0:13:21And eventually, inevitably,
0:13:21 > 0:13:22gravity wins.
0:13:22 > 0:13:25And that happens to every single star.
0:13:25 > 0:13:29The gas and dust released when stars reach the end of their life
0:13:29 > 0:13:32then goes on to form new stars and solar systems.
0:13:34 > 0:13:37So, in a sense, by learning about the death of a star,
0:13:37 > 0:13:40we're also learning about the birth of a star.
0:13:40 > 0:13:44And that's because all stars go through a life cycle.
0:13:47 > 0:13:50Stars form when enough dust and gas from space
0:13:50 > 0:13:53is pulled together by gravitational attraction.
0:13:53 > 0:13:56As this happens, the gravitational energy
0:13:56 > 0:14:00is converted into heat energy and the temperature rises.
0:14:00 > 0:14:03This is called a protostar.
0:14:03 > 0:14:05Once the temperature gets high enough,
0:14:05 > 0:14:08hydrogen in the star undergoes nuclear fusion.
0:14:08 > 0:14:10This is when it enters a long stable period,
0:14:10 > 0:14:13which we saw earlier playing Jenga.
0:14:15 > 0:14:19The fate of a star depends on how much matter it contains.
0:14:19 > 0:14:21At the end of its main sequence,
0:14:21 > 0:14:23a low-mass star, like our Sun,
0:14:23 > 0:14:25will expand into a red giant,
0:14:25 > 0:14:27then a planetary nebula
0:14:27 > 0:14:30before contracting into a white dwarf,
0:14:30 > 0:14:32and eventually a black dwarf.
0:14:32 > 0:14:36A really massive star will expand into a super red giant
0:14:36 > 0:14:38before exploding in a supernova.
0:14:38 > 0:14:41What's left will either be a dense neutron star
0:14:41 > 0:14:44or, if the star is really massive,
0:14:44 > 0:14:46it will end its life as a black hole.
0:14:46 > 0:14:48So, you getting it?
0:14:48 > 0:14:50Maybe a rap will help.
0:14:50 > 0:14:52# It starts as a big cloud of dust and gas
0:14:52 > 0:14:55# But then the gravity takes over and it starts to contract
0:14:55 > 0:14:57# The gases are squeezed together as the masses attract
0:14:57 > 0:15:00# To make the core get hotter from the steady collapse
0:15:00 > 0:15:02# The hot gases expand with an outward pressure
0:15:02 > 0:15:05# That can balance the gravity that's holding the star together
0:15:05 > 0:15:08# Then at a certain temperature the core will start to enter
0:15:08 > 0:15:10# Into nuclear fusion of Hydrogen at the centre
0:15:10 > 0:15:12# They shine like beacons entering the main sequence
0:15:12 > 0:15:15# The larger the mass the more energy they're releasing
0:15:15 > 0:15:18# And as the core's depleting all the energy it's keeping
0:15:18 > 0:15:20# The pressure pushing outward from the core begins to weaken
0:15:20 > 0:15:22# Gravity takes over now beginning to squeeze
0:15:22 > 0:15:25# The core shrinks under the weight thus increasing the heat
0:15:25 > 0:15:27# For nine tenths of its life the main sequence has been
0:15:27 > 0:15:30# It's main home, now it's growing and it's ready to leave
0:15:30 > 0:15:32# A low-mass star can become a red giant
0:15:32 > 0:15:35# Then a planetary nebula is next in line
0:15:35 > 0:15:37# Where you'll find a white dwarf that was left behind
0:15:37 > 0:15:40# Before dimming into a black dwarf over time
0:15:40 > 0:15:42# We get a red super giant from a star that's large
0:15:42 > 0:15:45# A supernova marks death of these larger stars
0:15:45 > 0:15:47# They leave a neutron star in their aftermath
0:15:47 > 0:15:50# And if not, a black hole is thought to end their path. #
0:15:50 > 0:15:55This life cycle of stars is an essential component of the universe.
0:15:55 > 0:15:58At its heart is the process that produces
0:15:58 > 0:16:00almost all the elements on Earth.
0:16:00 > 0:16:04So every atom of carbon that makes up my body
0:16:04 > 0:16:06was actually born in a dying star.
0:16:06 > 0:16:11So really, we're all made of stardust.
0:16:17 > 0:16:19On Earth, scientists can work out
0:16:19 > 0:16:21the chemical composition of most objects.
0:16:21 > 0:16:26But what do they do if the object is thousands of kilometres away?
0:16:28 > 0:16:30The Sun is our nearest star
0:16:30 > 0:16:34and it's a staggering 150 million kilometres away.
0:16:34 > 0:16:36Now, the fastest car on planet Earth
0:16:36 > 0:16:39goes at 430 kilometres per hour,
0:16:39 > 0:16:41but even at that speed directly to the Sun,
0:16:41 > 0:16:44it would still take us more than 40 years to get there.
0:16:44 > 0:16:47Now, I haven't got a car that goes anywhere near that speed,
0:16:47 > 0:16:52so, how are we going to find out what it's made of in five minutes?
0:16:52 > 0:16:57I reckon I can get halfway there with this cardboard tube and an old CD.
0:17:00 > 0:17:02Have you ever seen a demonstration
0:17:02 > 0:17:05where white light has been split into loads of different colours?
0:17:05 > 0:17:07Red, orange, yellow, green, blue?
0:17:07 > 0:17:09- No.- No.- Like a rainbow?
0:17:09 > 0:17:12Oh, yes! It is exactly a rainbow.
0:17:12 > 0:17:16But you can also do it using a tube and a CD.
0:17:16 > 0:17:20Don't look on the other side, you don't want to see the music that I listen to.
0:17:20 > 0:17:23And if we use this special device like that,
0:17:23 > 0:17:27what we can do is, if you look through that hole at the CD,
0:17:27 > 0:17:30you'll be able to see, kind of, different colours.
0:17:30 > 0:17:32So I'll let you all have a go.
0:17:37 > 0:17:39Point it around, see if you can catch the light.
0:17:39 > 0:17:42- I don't know how to do this! - LAUGHTER
0:17:42 > 0:17:44I've got another way to make it a bit brighter.
0:17:44 > 0:17:46So this is an LED light
0:17:46 > 0:17:49and that will give you a nice white light
0:17:49 > 0:17:51that consists of all the different colours like that.
0:17:51 > 0:17:55If we shine that through the end, you might be able to see it a bit better.
0:17:55 > 0:17:57- I can see it now.- Can you see all the different colours?
0:17:57 > 0:18:01- Oh, my gosh, yeah. That is so cool! - It's like making your own rainbow.
0:18:02 > 0:18:05This simple, homemade spectrometer
0:18:05 > 0:18:08is surprisingly similar to the equipment scientists have used
0:18:08 > 0:18:10to observe the light being emitted from the Sun.
0:18:10 > 0:18:13And we can learn more about the light that the Sun emits on Earth
0:18:13 > 0:18:17by observing the colours produced in the flames of burning elements.
0:18:17 > 0:18:20By burning compounds containing different elements,
0:18:20 > 0:18:23we can see that they each have their own characteristic colour.
0:18:34 > 0:18:37Potassium gives a lilac flame.
0:18:38 > 0:18:40Lithium gives a red flame.
0:18:40 > 0:18:43Sodium gives a yellow flame,
0:18:43 > 0:18:45whereas copper gives a greenish blue flame.
0:18:45 > 0:18:51Now, each element not only emits a certain type of light,
0:18:51 > 0:18:54it will also absorb
0:18:54 > 0:18:56the exact same colour of light.
0:18:58 > 0:19:01It's because of the light given off by the elements reacting
0:19:01 > 0:19:03that we are able to know what the Sun's made of.
0:19:03 > 0:19:07This is an absorption spectrum of the Sun.
0:19:07 > 0:19:09It's just like the spectrum we saw earlier,
0:19:09 > 0:19:11but it's a lot more detailed.
0:19:11 > 0:19:15These dark lines show where light of certain wavelengths
0:19:15 > 0:19:18is absorbed by the elements present in the Sun.
0:19:18 > 0:19:23We know elements emit and absorb the same wavelengths of light,
0:19:23 > 0:19:26so this means the dark lines also correspond
0:19:26 > 0:19:30to elements being emitted by the Sun.
0:19:30 > 0:19:32As white light passes through
0:19:32 > 0:19:33the Sun's atmosphere,
0:19:33 > 0:19:35some wavelengths are absorbed
0:19:35 > 0:19:37by atoms of the elements present.
0:19:41 > 0:19:42This means that the light
0:19:42 > 0:19:44that reaches us from the Sun
0:19:44 > 0:19:45is missing some wavelengths,
0:19:45 > 0:19:47which correspond to an element
0:19:47 > 0:19:49in the Sun's atmosphere.
0:19:52 > 0:19:54So the dark lines in the spectra of the Sun
0:19:54 > 0:19:57show that it's made of hydrogen, about 70%,
0:19:57 > 0:20:00helium, about 28%, and elements
0:20:00 > 0:20:03such as nitrogen, oxygen and iron
0:20:03 > 0:20:05in much smaller quantities.
0:20:05 > 0:20:08If we look at the spectrum of any distant star,
0:20:08 > 0:20:10we can work out what they're made of, too.
0:20:10 > 0:20:12This has helped scientists make some amazing discoveries
0:20:12 > 0:20:15about stars in our universe.
0:20:15 > 0:20:19Many of which are very different from our own star, the Sun.
0:20:28 > 0:20:29If you travelled to another planet,
0:20:29 > 0:20:32it's not just extra terrestrials you might have to contend with,
0:20:32 > 0:20:35you might also weigh twice as much as you would on earth.
0:20:35 > 0:20:37Now, it might sound a bit strange,
0:20:37 > 0:20:40but finding out about how our weight would change
0:20:40 > 0:20:42on different planets of the solar system,
0:20:42 > 0:20:45is linked to understanding how forces act.
0:20:45 > 0:20:48And I've come to the fairground to find out more.
0:20:51 > 0:20:52Gravity is a force.
0:20:52 > 0:20:56It attracts objects with mass towards each other.
0:20:56 > 0:20:59In space, it might look like there's no gravity,
0:20:59 > 0:21:02but astronauts are weightless because they're in orbit,
0:21:02 > 0:21:05so they're constantly falling towards the earth.
0:21:08 > 0:21:11The weight of something depends on its mass
0:21:11 > 0:21:14and the gravitational field strength.
0:21:14 > 0:21:15Weight is measured in Newtons
0:21:15 > 0:21:17and mass is measured in kilograms.
0:21:19 > 0:21:20Weight is a force.
0:21:20 > 0:21:24And it's caused by the pull of gravity acting on a mass.
0:21:24 > 0:21:27Mass is the amount of matter in an object.
0:21:27 > 0:21:29Unlike weight, it's not a force.
0:21:29 > 0:21:33An object's mass has the same value anywhere in the universe.
0:21:33 > 0:21:36On other planets, our mass stays the same,
0:21:36 > 0:21:39but our weight would change.
0:21:39 > 0:21:42That's because the gravitational force
0:21:42 > 0:21:44on different planets is different.
0:21:44 > 0:21:48Some of my mates have come down to help me show you what I mean.
0:21:48 > 0:21:50It's not the warmest of days here on Earth,
0:21:50 > 0:21:54but I'm not one to let a bit of cold get in the way of a science demo.
0:21:54 > 0:21:57Guys, do you have any idea what it would be like
0:21:57 > 0:22:01to be on another planet and what it would feel like, what you'd weigh?
0:22:01 > 0:22:06- ALL: No.- Right. Well, this ride will give us some idea of that.
0:22:06 > 0:22:07Let's give it a go.
0:22:08 > 0:22:11So we are presently, currently on planet Earth.
0:22:11 > 0:22:13Let's do a visit to Jupiter.
0:22:13 > 0:22:16- OK. Yeah, ready, ready. - Oh, no, I'm scared!
0:22:17 > 0:22:18OK.
0:22:18 > 0:22:20YELLING
0:22:21 > 0:22:23LAUGHTER
0:22:24 > 0:22:27YELLING
0:22:28 > 0:22:30- We are still alive.- Whoo!
0:22:30 > 0:22:35Right, so what part of that ride felt the lightest?
0:22:35 > 0:22:39At the top. It made your stomach go funny, dizzy. Dizzy stomach.
0:22:39 > 0:22:43Dizzy stomach! And when did you feel the heaviest?
0:22:43 > 0:22:46As it, kind of, came to the bottom. A little bounce.
0:22:46 > 0:22:50Wicked! You see, that ride is like actually being on other planets.
0:22:50 > 0:22:52When you was at the top and at the lightest,
0:22:52 > 0:22:55it's like being on a planet with less gravity, like Mercury.
0:22:55 > 0:22:59But when you was at the bottom on that bouncy part where you felt a bit heavier,
0:22:59 > 0:23:02well, that heavy feeling, that's like being on a bigger planet.
0:23:02 > 0:23:04For example, like Jupiter.
0:23:04 > 0:23:07Except you wouldn't just be feeling like that when you hit the bottom,
0:23:07 > 0:23:09you'd just always feel like that.
0:23:09 > 0:23:13Being on a ride like this is the closest you can really get
0:23:13 > 0:23:15to actually being on another planet.
0:23:15 > 0:23:17- LAUGHTER - Yeah!
0:23:19 > 0:23:22Because we know that our mass is constant,
0:23:22 > 0:23:24it must be the gravitational forces
0:23:24 > 0:23:25that make our weight change.
0:23:27 > 0:23:31On Earth, the force of gravity on a one kilogram mass is ten Newtons.
0:23:31 > 0:23:34So if my mass is 70 kilograms,
0:23:34 > 0:23:38then the force of gravity on me makes my weight 700 Newtons.
0:23:38 > 0:23:40As the chair and I fall,
0:23:40 > 0:23:41I'm pressing less on the chair
0:23:41 > 0:23:43and appear lighter.
0:23:43 > 0:23:45Similar to astronauts in the space station.
0:23:45 > 0:23:47This would be the same feeling on Mercury.
0:23:47 > 0:23:53There, the force of gravity on a one kilogram mass is just four Newtons.
0:23:53 > 0:23:56So if my mass is 70 kilograms,
0:23:56 > 0:24:00then the force of gravity on me makes me weigh about 280 Newtons.
0:24:00 > 0:24:04That's like me weighing as much as your family dog.
0:24:04 > 0:24:07BARKING
0:24:07 > 0:24:09At the bottom of the ride when it starts to slow down,
0:24:09 > 0:24:12the forces were unbalanced and I felt much heavier.
0:24:12 > 0:24:15This would be the same feeling on Jupiter.
0:24:15 > 0:24:21There, the force of gravity on a one kilogram mass is 25 Newtons.
0:24:21 > 0:24:23So if my mass is 70 kilograms,
0:24:23 > 0:24:29then the force of gravity on me makes my weight about 1,750 Newtons.
0:24:29 > 0:24:33This is like weighing as much as a gorilla.
0:24:33 > 0:24:34So the greater the mass of the object,
0:24:34 > 0:24:36the stronger the force of gravity.
0:24:36 > 0:24:39That's why you'd weigh more on Jupiter.
0:24:40 > 0:24:44Gravity also keeps planets and moons in orbit.
0:24:44 > 0:24:47We know the gravitational pull of an object is determined by its mass.
0:24:47 > 0:24:50This can also help us make sense
0:24:50 > 0:24:53of the movement of the whole solar system.
0:24:53 > 0:24:55All the planets and moons in the solar system
0:24:55 > 0:24:56spin around a central point.
0:24:56 > 0:24:59A bit like me on this roundabout.
0:24:59 > 0:25:02The object with the greatest mass sits at the centre
0:25:02 > 0:25:04and its gravitational pull
0:25:04 > 0:25:07attracts other objects into an orbit around it.
0:25:07 > 0:25:11And that's why every planet in our solar system orbits the Sun.
0:25:11 > 0:25:14It's all down to gravity.
0:25:22 > 0:25:24If you were to travel into space,
0:25:24 > 0:25:27you might feel far away from life on Earth.
0:25:27 > 0:25:30But space can actually help keep us connected.
0:25:30 > 0:25:34It's all down to understanding the properties of different waves.
0:25:38 > 0:25:41Now, you see when I shine this light?
0:25:41 > 0:25:43That's just called visible light.
0:25:43 > 0:25:47But did you know that there's other types of light that you can't see?
0:25:47 > 0:25:51- No.- There's also a type of light called infrared.
0:25:51 > 0:25:54You might have heard of it on things like these, TV remotes.
0:25:54 > 0:25:56To change the channel, you push a button and it changes.
0:25:56 > 0:25:58There's a little red light in there.
0:25:58 > 0:26:00There's a little light in there, isn't it?
0:26:00 > 0:26:04- Tell me if any of you can see it. - No.
0:26:04 > 0:26:05Have you all got mobile phones?
0:26:05 > 0:26:08- I do!- Wicked!
0:26:08 > 0:26:09- They've got cameras on them, yeah? - Yeah.
0:26:09 > 0:26:12You need something that's sensitive to infrared light.
0:26:12 > 0:26:14- But look what your phones are capable of doing.- Red!
0:26:14 > 0:26:18- Yeah, it's red.- Can you see the light? You can see a light off it?
0:26:18 > 0:26:23- Yeah!- And that's because your phones don't just see visible light,
0:26:23 > 0:26:25your phones see infrared.
0:26:25 > 0:26:28But your eyes only see visible.
0:26:28 > 0:26:30The sensor on the phone's camera can detect
0:26:30 > 0:26:33a wider range of wavelengths of light than our eyes can.
0:26:33 > 0:26:36We can only see visible light,
0:26:36 > 0:26:39but there are other light waves, all with similar properties.
0:26:39 > 0:26:41We call all of these types of waves
0:26:41 > 0:26:43electromagnetic waves.
0:26:43 > 0:26:44And they are all arranged
0:26:44 > 0:26:46on the electromagnetic spectrum.
0:26:46 > 0:26:47At one end of the spectrum,
0:26:47 > 0:26:51we have low-frequency radio waves and microwaves.
0:26:51 > 0:26:56Infrared, visible and ultraviolet waves have a higher frequency.
0:26:56 > 0:26:57While X-rays and gamma rays
0:26:57 > 0:26:59have a very high frequency
0:26:59 > 0:27:02and are at the opposite end of the spectrum.
0:27:04 > 0:27:08All electromagnetic waves carry energy from one place to another.
0:27:08 > 0:27:10And they do it at the speed of light.
0:27:10 > 0:27:13They can also travel through a vacuum, such as space.
0:27:13 > 0:27:16That's why they're used in communications,
0:27:16 > 0:27:20because the signals can be sent rapidly across large distances.
0:27:20 > 0:27:24Vans like this make sure we never have to miss any event, however far away.
0:27:24 > 0:27:28They're equipped to send live video back to a TV broadcaster
0:27:28 > 0:27:30from anywhere in the world.
0:27:30 > 0:27:32They do this by sending microwaves
0:27:32 > 0:27:33through the atmosphere to be
0:27:33 > 0:27:35picked up by satellites in space
0:27:35 > 0:27:38thousands of miles above the Earth's surface.
0:27:38 > 0:27:41The signal is then sent via satellite
0:27:41 > 0:27:43back to a TV broadcaster.
0:27:43 > 0:27:48So, how does the signal actually get to my TV set at home?
0:27:48 > 0:27:53The TV broadcaster can transmit it to your TV in different ways.
0:27:53 > 0:27:55If you've got an aerial on your TV at home,
0:27:55 > 0:27:59you receive the signals via radio waves transmitted by a TV mast.
0:27:59 > 0:28:01If you've got a satellite dish on the side of your house,
0:28:01 > 0:28:05you receive the signals via microwaves sent from a satellite.
0:28:05 > 0:28:10Ah! Does that mean when I watch my favourite football team live on TV,
0:28:10 > 0:28:12the signals have to go miles into space
0:28:12 > 0:28:14and back again before getting to me?
0:28:14 > 0:28:16Got it in one.
0:28:17 > 0:28:19The signal isn't sent directly
0:28:19 > 0:28:22because it would be absorbed by obstacles such as buildings.
0:28:22 > 0:28:25Ah, that makes sense. I'm feeling your hat, by the way.
0:28:25 > 0:28:27Nice one. Yours ain't too bad yourself.
0:28:27 > 0:28:29Yeah!
0:28:29 > 0:28:31So nearly all forms of communication,
0:28:31 > 0:28:34whether emails, texting, TV or the internet,
0:28:34 > 0:28:37uses some part of the electromagnetic spectrum
0:28:37 > 0:28:39being sent through space.
0:28:39 > 0:28:42And that's pretty amazing!
0:28:42 > 0:28:45Now all it leaves for me to do is...wave goodbye.
0:28:47 > 0:28:49# It starts in the radio waves
0:28:49 > 0:28:51# With a lower frequency than the microwaves
0:28:51 > 0:28:54# That come next as we step over the infrared
0:28:54 > 0:28:57# To find Richard of York giving battle in vain
0:28:57 > 0:29:00# But no threat, that's a mnemonic for the visible spectrum
0:29:00 > 0:29:02# That blends into ultraviolet radiation
0:29:02 > 0:29:04# Then X-rays come at increased frequencies
0:29:04 > 0:29:08# With the gamma rays taking up the highest energies. #
0:29:09 > 0:29:12Subtitles by Red Bee Media Ltd