Lunchtime Labs: Sea Gliding Science

hi everyone I'm Beth and I'm jJack and  in today's lunchtime lab we're going to teach you a bit about oceanography which  is the study of oceans and how they work. In this lunchtime lab we're going to walk you  through a few experiments that we've performed which will help you to understand some  of the things that we as oceanographers have got to understand and think  about when we look at the oceans, and some of them you'll be able  to do along with us at home. At the end we're going to take y

ou down to the  tank room and there'll be some robots there and we can show you how they work and how  we use them to help us study the oceans. In this experiment we're going to  look at something called density. Density is a scientific word which explains  how much material there is in a certain space. To look at this idea I've got a wooden  block and a metal block in front of me. Both of them have a mass of 100 grams and  because they have the same mass that means in my hands they feel pretty

much the same. However of course the wooden block is a lot bigger than the metal block that is because in  the metal block all of the particles and atoms are packed into a much smaller  space but you could say that there's pretty much the same number of  particles but just in a smaller space. So that means that this metal block  is more dense than the wooden block. Why is density an important thing for us as  oceanographers? Why does it matter? It's because in the water in the oceans the density

of objects  controls where they are, whether or not they're at the top or at the bottom and to explain this  I'm going to put these objects in the water. The metal block sinks to the bottom of the water  very very easily whereas the wooden block sits on top even if I try to push it down that's  because in water if an object is very dense then it will sink down to the bottom. But if  like the wooden block an object is not very dense it will float at the top and in water different  things can mak

e water have different densities so if you get water which is very dense and water  which is not very dense, then the water which is very dense will sit at the bottom and the  water which is less dense will sit at the top. So there are a few things that we have  to think about when we study the ocean, and these are temperature and salinity or  how salty the sea is so we think about these because these have an influence on density. First off our temperature - if something's really cold it's going

to be more dense and sit  at the bottom then something which is hot and going to be less dense and float at the top. So  if you had cold water it would be underneath hot water whereas if we look at salinity or how  salty or fresh something is so fresh means water that's not got very much salt in it and  salty is water that's got lots of salt in it. So salty water has all the salt particles mixed  in with the water and that makes it more dense so it'll be at the bottom whereas fresh water  will

float at the top because it's less dense. So we have to think about all these  things when we're studying the ocean and what we're going to do now is we're going  to take two very cold ice cubes and we're going to put one in our tank of salty water here and  one in our tank of fresh water and we're going to have a look at what happens and use that  to show you a little bit more about density. So what do you think might  happen before we put them in? I'm back with two ice cubes and we're going  t

o pop these in our tank of salty water and a tank of fresh water to see what happens. So these ice cubes have been made with purple food dye so that you can see the water  spread out throughout the tanks as they melt. Now ice is less dense than water so when we put  these in the tanks they're going to float on top of the water but the water that melts out of  the ice cubes might do something different. What do you think might  happen when I put these in? Let's find out. So we can see now our ice

cubes are in our  tanks of water and if we look at our fresh tank first our ice cube is starting to melt and  we can see all this purple water that's really cold and fresh from our ice cubes sinking down  to the bottom of our tank and that's because this cold water is more dense than the room  temperature water that's in that tank already. But if we look at our salty tank things look  a little bit different and why might that be? So our ice cube is still melting and giving  out really cold wate

r but this time it seems to be floating at the top and that's all to do  with the salinity of our tank so remember this tank is full of really salty water and what's  happening is we're putting fresh water into that so our fresh water is floating at the top  because it's less dense. So that's the fresh water from our ice cube melting even though it's  cold - it's still floating on top of the tank. Cool so to recap, in this experiment we've been  looking at density and if we remember there are tw

o things that affect the density of water  - that is the temperature and the salinity. We saw that the temperature affected the water  in the fresh water tank because the cold water coming from the ice cube sunk to the bottom. So we showed that cold water sinks in the salty tank; we showed that salty water sinks because the  salt water in the main tank stayed below the fresh water with no salt that came out of the ice cube. So if you like this experiment you can try it at home by getting yoursel

f some table salt, a  container, some tap water and some food dye. Now you might need a parent or guardian's help  to do this one and you're going to freeze some ice cubes with some food dye mixed in and  use gloves so you don't stain your fingers, and then mix yourself up a salty tank and a  fresh tank. You can make your salty tank by using 35 grams of table salt in a litre of water. And  take your ice cubes once they're frozen and have a look and see what happens when you put them  in the wate

r - do they sink or do they float? So now we're going to take our tank of  salty water and a tank of fresh water some pencils and some plasticine and we're  going to look a bit more about density and try and teach her about buoyancy. So if we take a pencil and put it in a tank  of fresh water what do you think might happen? So it floats up to the top and this is because  our pencil is less dense than our fresh water, whereas if we take some  plasticine what might happen here? Pop it in the water

it's more dense than  the water so it sinks to the bottom. So now what might happen if we take another  pencil and a blob of plasticine and put the two of them together to make one object. I'm going  to start with just a little bit of plasticine and put it on the end of the pencil... ...like that okay so if I put this now in the tank  of fresh water do we think it will float because the pencil's less dense in the water or sink  because the plaster seems more dense in the water? It floats to the

top and that's because  there's not very much plasticine so the density of the overall object  is less dense than the fresh water. But what happens now if we put even  more plasticine onto the object? Okay, that's quite a lot of plasticine that  we've got on the object now. So what happens if we put this back in the fresh water that  sinks to the bottom which means that now because of the extra plasticine the overall  object is more dense than the fresh water. So earlier we took a pencil and pu

t just  the right amount of plasticine on it so that it'll have the same  density as our fresh water. So what do you think might happen if  we put this in the water? Let's see... So what's happened is our pencil was hovered  in the water just where we put it and that is because it has the same density as the water. And this is something called neutral buoyancy. So what happens now if we take this  pencil out of the fresh water tank (if I can actually grab it) and put it in the  salt water tank w

hich we know is more dense than the fresh water tank? Will it float sink or be  neutrally buoyant in this tank? Let's take a look. It floats in the salty water tank which means that  this object which is the same density as the fresh water which is why it was neutrally buoyant in  this tank is less dense than the salty water. So earlier we've repaired a  pencil with some plasticine on it just the right amount of plasticine so that  it's neutrally buoyant in our salty tank here. So if we pop this

in the water... again it's going to hover just where we left  it and that is because it has the same density as the salt water. So what do you think will happen now if we put this pencil and  plasticine back into the fresh water tank? Will it sink float or be neutrally  buoyant? Remembering that the fresh water is less dense than the salty water and  it was neutrally buoyant in the salty water. It sinks to the bottom which again is what we  expected because the fresh water it's easier for thing

s to sink in it because it's less dense. So this object is more dense than the fresh water. So just to recap we've shown  you that our salty water is more dense than our fresh water and what  neutral buoyancy is, which is where the our pencil and our plasticine had the  same density as the water it was in. So you can try this experiment at  home if you get a clear mixing bowl. You measure out 35 grams of salt and put it  in a litre of water, mix it all together. Find yourself a pencil into plast

icine or if  you don't have any some blue tack will work too, and see if you can make your pencil float sink and  be neutrally buoyant in your bowl of salty water. In this experiment we're going to  be salt tasting which is something that you guys at home can join in with us for. In front of me I've got four different containers full of different amounts of table salt and soon  I'm going to add some water into all of them and stir them up so that they all look the same. A fun fact that you might

not know is that different seas and oceans around the world are not  all exactly as salty as each other some of them are more salty and some of them are more fresh. The table on screen now is showing how to make these four different solutions at home with  your own table salt, water and containers. I'm going to add water to these four  containers and once I've done that I'm going to bring Beth here and she's going  to try and taste the four different samples and see if she can work out which on

e represents  which sea in which ocean from around the world. Welcome Beth in front of us we've  got four different containers full of solutions of salty water and all  of them have different amounts of salt in. They represent different seas and oceans from  around the world. The seas and oceans that they represent are melted Antarctic sea ice, the Baltic  sea, the Mediterranean sea and the Dead sea, but they're not necessarily in that order. So your job is to try and take a small taste from eac

h of them and work out by  how salty they are which one's which. If you're doing this experiment with us at  home please be careful when you're tasting the different solutions of water because  the salty ones will taste rather nasty and it might make you a little bit ill so please  only taste a little bit and don't swallow any! So can you talk us through which ones you would  expect to be the most and the least salty and why? Okay so I think the and melted sea ice from  Antarctica is going to be

the least salty and that's because sea ice doesn't really  have much salt in it from where the water in the sea is frozen to make the ice. And then I think the one from the Dead sea is probably going to be the most salty  and that's because the Jordan river flows into the Dead sea but there's no  rivers that float out of the Dead sea. So the water evaporates that's in the Dead sea  and goes up into the air and that leaves all the salt behind and makes it really really salty. And then the Medite

rranean and the Baltic I'm not sure which way around they're going to  be so I'll have to taste them and find out. That's interesting thank you, I'll let  you taste them now and you can see. Okay I'll switch something How did that one taste? It's a little bit salty but not too bad. Okay. Oh that one tastes a bit more salty number three. That one tastes almost like regular  tap water. That tastes quite fresh. Interesting, okay. Number four. Oh that's very salty. Oh interesting. So I think number

four is going to be the Dead  sea because that's the saltiest by quite far. I think number three is going to be the  sea ice because that's the freshest. And then Mediterranean and Baltic. I  think the saltier one which was number two is going to be the Mediterranean which  makes number one the Baltic. Was that right? Well done! That was four out of four. That was a very good effort indeed. So perhaps we should give a quick explanation  of why the Mediterranean is more salty than the Baltic, bec

ause they're pretty close. But there's  a little bit of a difference - there's a little bit more rain over the Baltic sea which means and  of course rain is fresh water. So if you get rain over a sea it makes it less salty which is why  the Baltic is more fresh than the Mediterranean. Wonderful you did a very good job there! So we hope you were able to work these out alongside us at home but if not just  to recap number one is the Baltic sea, number two is the Mediterranean sea,  number three is

a melted Antarctic sea ice, and number four is the Dead sea. Thanks for joining in! So next we're going to show you a  little bit more about density and we're going to teach you about pressure. Now pressure is the force acting in an area so if I take my fingers and push against the  bottle here you've got the force of me pressing on the bottle and the area that's happening  is where my fingers are touching the bottle. And what we're going to do is we're going  to use this idea of pressure I'm g

oing to show you how it works by using these little  divers that we have in our bottles here. So in water you can't really squash water  very far because all of the bits that make up the water, the molecules and the atoms  are already really tightly packed together, whereas in air which is a gas all of the molecules  and atoms that make it up are spread out all over the place and they're all whizzing around  really quickly and so we can squash them all together and make it a lot smaller. Cool. S

o as Beth says if you put pressure on the outside of the bottle then that pressure  increases the pressure inside the bottle as well. So what happens if I start to squeeze the bottle  I'm increasing the pressure on the outside and that pressure means that everything  on the inside is trying to get smaller, but as Beth said you can't really make water  smaller. However you can make air smaller and these little divers on the inside of the  bottle, there's air inside them so when we squeeze the bot

tle the air inside the diver will  start to compress inwards and as it does that the little hole in the back of the diver will  start to suck the water from the bottle into it to fill the gap where the air is getting smaller. And what that means is that as the water is going into the diver the diver is going to get denser  because there's more material inside it and as it gets denser that means that if I squeeze  it hard enough it will get denser than the water in the bottle, which means that it

sinks. And now if I start to release my pressure so if I start to lighten my fingers then the air inside  the diver will start to expand outwards again and that means that it's become less  dense in the surrounding water once again. For our final segment we're here in the  tank room at the University of East Anglia and we're going to look at one of the robots  that we use to learn about the oceans, which is here in the tank next to us. We're also going to look at this glider here which is clear

which means that  we can look closely at the inside of it to see how what's happening on the inside of this  one, which is exactly the same as the inside of that one, affects the way that it moves. So if we think back to our pencil buoyancy experiment that we did earlier we managed to make  our pencil and our plasticine together neutrally buoyant so it's sat in the middle of our tank. That's exactly what we've done with our sea glider here ready to do our experiments so  how does this glider mo

ve you might wonder it doesn't have an engine on the inside of it  like a car or like a ship and that's because we want gliders like this to be able to stay  in the oceans for lots of months at a time and engines have to be re-fueled quite frequently. So instead we've got to be very clever about the ways that we make it move and we're  going to show you now how we do that. We're going to start by showing you how we get  our sea glider to go down through the water. Once the sea glider is in the 

ocean we want it to sink down so we can study what's happening deep  down all the way to a thousand meters. I you think back to our bottle diver experiment  from earlier we made the diver sink by filling the diver with water as the air bubble  was squashed when we squeezed our bottle. What we do with our sea glider is very similar  in the back of the sea glider we have a bladder which is a bit like a balloon containing oil. When we put the sea glider in the water this section of the sea glider f

ills  up with the water from around it. If we suck some of the oil out of the  bladder and further into the sea glider then more water goes into this back section  to fill the space where our bladder was. This makes the glider more  dense overall so it sinks. That's great. S now we know how to get the  glider to sink deep into the ocean below the surfac,e but right now it's only going  straight downwards so is there any way we can get the sea glider to travel forward through  the ocean too, so t

hat it can explore more of it? Yes there is. We have to make the glider  point its nose a little bit downwards and then the way the ocean water pushes  on the sea glider wings as it's sinking will push it forwards as well as going downwards. To make the nose of the glider point  downwards we have to move things around inside the sea glider so that the  front becomes more heavy than the back. So we use the glider battery this big thing in  the middle which has a metal weight attached to it as wel

l to make it even heavier and we move  that forward towards the nose of the glider. Let's see what happens when we send  this command to the sea glider. So we can see that the nose of the sea  glider has just tilted down as the battery has gone forward towards the nose. If you're wondering why the sea glider isn't traveling forwards now  that we've got it tilted forwards it's because it's got to be sinking at the  same time as having its nose pointing forwards. Now we've seen how the glider  can

get down deep into the ocean, but we need it to get back to the surface. Think back to our bottle diver experiment again the diver floated back up when  we stopped squeezing the bottle and let the extra water back out  of the diver as the air expanded. Again we do something very  similar with our sea glider. If we make the bladder fill up with oil from  further inside the sea glider, this makes the bladder take up more space which forces some of  that water out in the back section making the se

a glider less dense, and help it float back to  the surface, through the surrounding sea water. So now we have a glider that can move up down  and forwards but what happens if the sea glider isn't going in the direction we want it to go? What happens if we want to turn it? Can we do that? We can - again we use the battery from  before and instead of moving it forwards and backwards we twist it and that means that we're  changing the bit the side of the glider which is heavier the heavier side of

the glider will then  sink downwards and it'll cause the glider to roll. So let's see what happens  when we rotate the battery and help the sea glider keep moving  forwards as well as upwards when it's rising and not just straight upwards, we can do the  opposite of what we did earlier and tilt the nose upwards instead of downwards, so the glider will  be rising and be tilted upwards at the same time. We can see what happens when we send this command  to the sea glider. To do this we have to mo

ve the battery further away from the nose. We've shown that our glider can move up down and forward through the water  and can also change direction by rolling. So now we have a robot that can explore  anywhere down to a thousand meters in the ocean but what do we scientists do with it? So we put sensors on our sea gliders to measure lots of different things in the ocean. This glider in the tank has sensors in three different places which help us  measure temperature, salinity, pressure, amount

of light in the water  and amount of chlorophyll in the water. We can add other sensors to our sea  gliders to measure even more things like the amount of oxygen in the water or  even listens to sounds that are in the water. When we launch our gliders into the ocean  we use measurements like these to learn more about what happens in the ocean itself. The glider group has previously studied areas of the ocean where the oxygen levels are  becoming so low that animals can't survive. In other areas

we've managed to use sea  gliders to go out and listen to whales. So when our gliders are out in the ocean,  we can't plug a cable in like we did in the tank to give commands. So what do we do instead? We have to use satellites to talk to our sea  gliders and tell them where to go, so then the sea guider does lots and lots of calculations  whilst it's under the water to change its pitch its roll and its density, just like we saw in  the tank so it can try and reach its target. The sea glider can

stay in the water for months  at a time before we go and pick it up with a ship. So now you know lots about sea gliders  and how we study the ocean with them. That's it from Beth and I on  this lunchtime lab on sea glider. We hope that you've enjoyed watching  these experiments and learning about the robots that we use to study the  ocean if you've got any questions, pop them in the comments down below and if you'd  like to learn more about the missions that we do with our sea gliders go to the

UEA glider website  with a link down below. Thanks for watching.