[Music] it's now my pleasure to introduce the naked scientists they're going to take us on a Whistle Stop tour of the world of waves gases and chemistry they'll detonate bombs they'll electrocute vegetables they'll turn out they'll turn air into liquid and they'll launch hydrogen powered Rockets as part of this those of you in the front row may get get a little bit wet so please do prepare yourselves um for such now in this talk we want to hear a lot of noise we want a lot of interaction this talk is definitely not for the faint-hearted so without further Ado it's my pleasure to introduce the naked [Applause] scientists Moon full of people hello hello welcome to the Cambridge science festiv first of all I'm Chris Smith and let me introduce two fine colleagues from The Naked Scientist Ben [Applause] vler and Dave [Music] anel now I'm really sorry if anyone's disappointed that we aren't actually naked I can probably safely reassure you you would be a lot more disappointed if we were okay so please enjoy the next 45 minutes is please please interrupt us shout out questions and get involved we love that let me introduce first of all our first experiment which is all about light can we have the lights off please it's not working why isn't that working ohal hey okay what we've got here is two lights but not actually giving out light which you can see if you imagine all the colors of the rainbow it goes from red orange yellow green blue indigo and violet but the end of that rainbow isn't anything to do with the world it's not about physics it's just about your eyes your eyes aren't good enough to see beyond it these lights are giving out a color of light called ultraviolet Beyond The Violet in the Spectrum as you can see on Ben's arms something interesting is happening when that hits his arms not actually seeing his bones what we've actually done is we've taken a high highter pen and we've drawn on his arm and as you can see this highlighter pen is converting this invisible ultraviolet light into light you can see in this case bright yellow color and it's really quite cute you sometimes see them in discos and things like that discos I get told off when I talk about Club it's been a long time since they been to a nightclub now one of the things about UV of course you do see see them in nightclubs they used to great effect for looking flash at Raves and that sort of thing but ultraviolet light also comes from the Sun and when we get exposed to too much of it it can be very damaging and lead to skin cancer Dave now what do you do if you want to avoid getting sunburn or get getting skin cancer Sun cream so this ought to stop the ultraviolet light getting to Ben's skin so we'll test it on his arm now if it blocks the UV we should it should stop the UV from getting to the highlighter so it should stop glowing let's see what happens get a bit more on there so it would seem that sun cream Works which is kind of reassuring I feel there we go you probably shouldn't use that much sun cream but do make sure you reapply okay do you have the lights back up so you can see if you look at Ben's arm that actually you can still see the highlighter pen underneath demonstrating that it wasn't just blocking out all the light getting through there are particles or chemicals in that sun cream that specifically block the ultraviolet part of light and that's what's stopping it getting into the into the ink and making it fluores I thought that's was pretty cool I think they deserve R of [Applause] [Music] Cl okay now the next thing I'm going to do is show you another way that we can give energy to things we gave energy to the Dy in that ultraviolet in that pen using ultraviolet lights but we can also put energy into things with flame this is a blowtorch you can make creme brulee with it if you're into that kind of thing but what I've done is to dissolve some common chemicals in alcohol and water and I'm going to spray these through this flame and what will happen is that the energy in the flame will go into the particles that come out of this liquid and it will excite the atoms and they will then soak up some of that energy and then give it out again and this is the basis of a a field called spectroscopy so let's just give it a go if we could have the lights off please see if anyone can guess what these particular chemicals are what color is that any guesses what color it could what what chemical it could be indeed it is it's a solution of copper we have another chem here to try see what color this one this is all very Harry Potter I think is it's a red color and this is a salt of a metal called strontium I wouldn't advise you to put strontium on your chips it's actually quite poisonous um see if you can guess what this one is and I think you probably may have put this one on your dinner so that's right it's orange and it's sodium now what's actually going on here is that the atoms are getting energy from the flame and this is making the atoms excited and specifically the electrons around the atoms excited and when they soak up that energy they have to give it out again and every single chemical on Earth gives out energy at a specific wavelength or frequency and that's why you see different colors with different chemicals and we can use this technique to identify what is in various things so we know for instance what is in the sun because without actually going to the sun we can just look at the light coming from the Sun and we can see these different colors and this tells us what the chemical composition of the sun is which is really clever but what about if I asked you about a an item that you might find in a hamburger Ben okay can we have the lights back on what we thought we would do is get you to work out some of the substances in this this is a girkin perfectly normal innocent girkin now we need some way of giving this girkin some energy now we could put it in the flame but that's kind of a bit boring a bit p a Chris has already done that so I thought we would try electrocuting it so what I have here is essentially an electric chair for girkins it's made up of two forks which I've slightly mutilated a couple of couple of months ago and they're wide up to the mains not quite at the moment otherwise I would be very worried about doing this bit put them on the forks okay now um what I'm going to do in a moment is put full 240 volt Mains electricity through this girin is it possible to put this on the camera by any chance so we can we can see it on the screen can we see it on the screen possibly not no no oh well we'll carry on you should be able to see okay so every dip the lights a bit oh it's coming up oh it's warming up can we have the lights off please thank you okay okay I can't see it oh well you'll see it in a minute okay so hang on Dave CU it's warming up it's looking promising we there yeah it looks like we're there hold on let's find out yeah we're that okay so have a good okay I'm now going to attach Main's electricity to this girkin now the the girkin slowly drying out around the fork it's getting very hot giving off lots of steam and where it dries out it doesn't conduct electricity anymore and you get sparks those give the girkin lots of energy now what color are those Sparks now what chemical do do you think might be in that girkin what what made a bright orange color earlier sodium do we have another go compare [Music] here and if I look at the ingredients of these girkins it does include sodium chloride salt so well done we'd like to point out that this is not the best way to cook girkins at home but once they've been pickled you may as well and raw but of course you may have seen that orange color elsewhere in fact you might have seen it along pretty much every Road in Cambridge and that's because of sodium lamps now these are the things that we use for street lights and this works in a very similar way it passes electricity through sodium in order to give out that orange light and it's very very efficient because instead of giving out lots of different colors of light that we see as white it just gives out that one color that one orange and it uses very little electricity to light up the streets at night so there you go you could perhaps light the streets with gerkins but those around here in the room will probably know how bad the streets would smell if we were to do that and slowly the rest of you will enjoy that smell as well it's actually really nice to be here in Cambridge because actually for these experiments we did this so that we could go to other countries in fact we've done this show and a variant of it in three different continents and three different countries so far never come to Cambridge which is our home so it's great to actually be here and doing it for you today and when we were in South Africa last year I had a microwave on a table like this and and I made the mistake of saying what's this and of course I want a shout out microwave and this little girl in the front when I said and how's it work looked at me like I was a complete idiot and said well you turn it on but one way of getting energy into things is with with flames and electricity but microwave Wes are energetic too and a microwave is actually a form of light and in the side of this microwave is something called a magnetron and this turns electrical energy into a microwave a form of light and the light wave goes across the microwave bounces off the far side and comes back again mapping onto itself and it creates what's called a standing wave but what that means because a light wave is effectively a changing electromagnetic field in other words you've got a changing magnetic field because you have a changing magnetic field you get a changing electric field and this propagates if you put something metal in a microwave you can induce a very large electric field in that in that metal object and this will make a very large current flow has anyone ever done this by accident have you hands up if you've ever put something you shouldn't have done by accident of course in the microwave so what happened big shower of Sparks isn't it very dangerous isn't it should never do it should you shall we try well actually what we're going to do is um we're we're going to try it with with this now these are our signature experiment if you like they're Cris packets but they're silver and the reason they're silver is because this is a plastic packet but sandwich between the layers of plastic is a very thin film of aluminum it's there for freshness to keep the food fresh but the aluminium is of course metal so if we put this in the microwave what should happen is that the changing electromagnetic field will make a very large current begin to flow backwards and forwards in that aluminium field and as you know when you pass electricity through metal it gets hot and what that does is pass the heat into the plastic and if you ever put a crisp packet in the oven it shrinks and changes shape doesn't it so what the Cris packet it tries to do is to change shape really fast and this effectively cracks or splits the metal foil and as this surge of electricity is running through the foil it suddenly hits a gap and all the electricity piles up on itself and it's forced to jump the Gap and make sparks so if we've got this right I should be able to put this in the microwave and we should see something so let's have a go so this is um this is a stunt microwave I'm just joking it's a cheap microwave in other words uh I just going to put the packet in here uh and if I ask that the camera just focus on the inside of the microwave and I've got my hand on the knob if we could turn the lights down now please thank you and you want to Count Me In oh maybe not so we H these Tech technical people again they're great aren't they just joking are we in business yeah okay do you want to count me in three two it's pretty good is [Music] it I'm not sure that this would taste too appetizing although if you've ever eaten at the Adam Brooks canteen maybe you'd disagree do you want to try it again okay we'll try a different flavor of crisps just to show that flavor isn't the deciding factor both all other flavors work [Music] too other crisps are available but this one is The Real McCoys okay let's have the lights off please so done to perfection thank you now that was something fairly UND daring you can probably if you're careful do that at home but just don't touch the Cris bag afterwards because the melted plastic is molten and it could burn you but here's something you probably should never do at home but I'm going to do it anyway telling you not to do it and put one of these who knows what this is well this is an environmental disaster of course because we're not allowed these anymore are we because um they they use huge amounts of energy they only turn a small proportion of it into light you can see but how do they work well the answer is on the end here you've got some electrodes and current passes through those electrodes and there's a very thin filament inside made of tungsten and the passage of electricity through the tungsten makes the tungsten glow because it Heats it to about 2000° C and that glowing is the visible light you can see and there's some heat too but because there's metal in there if we put this bulb in the microwave we should be able to make a very large current flow in the filament it will get excited and it will glow but there's an added effect as well because what else is in this bulb there's some gas in here actually does anyone know what the gas is that's right there's some argon an inert gas to help cool the filament cuz argon's unreactive it's a noble gas and just like a neon sign you've seen a neon sign the writing in lights argon is in the same family of the periodic table as neon so it glows in the same way neon does so if I put this this light bulb in the microwave this bulb says it's 60 watts so we're going to put a kilowatt through a 60 wat light bulb shall we have a [Applause] go okay can can we have the lights down please can we turn that one off please on the camera thank you okay here we go ready you want to count me in three [Applause] two now I only do it for a very short time because it is possible to make the the light bulb physically melt and explode if you do that for any longer than about 15 seconds and and as I found out my wife has killed me for because I did this at home it does actually damage your microwave if you're not careful so and and my wife is more dangerous than the microwave I tell you thank you be careful if you ever do that now one thing that you may or may not not have heard about and it almost sounds a bit silly is that the American Military amongst a few others are actually looking at using microwave energy as a weapon to try and clear crowds now the idea is that they don't actually cook people that obviously would be unethical and the American government wouldn't dream of doing anything unethical but but it can make you uncomfortably warm make you a bit fidgety and so if there is a big crowd if they're being Troublesome can make them dis first now cook them a little bit basically cook them a little bit yes we figured that we would try and come up with something else another type of weapon for clearing crowds made not with a microwave with something else you find in your house a vacuum cleaner now this is admittedly quite a fancy looking vacuum cleaner but a vacuum cleaner nonetheless you know how these work they suck and you put something on the end of there usually a head that will go into corners or something like and you use it to suck up all of the Dust which goes into a bag in here now I've taken the bag out of there because uh it works bit better when we do this what we've put on the end of our vacuum cleaner is a bit of Plumbing now that obviously isn't going to work very well at the moment because you're trying to suck dust in but there's other stuff coming in from this way and you'll get bits of cat hair stuck in it won't work very well at all because this is actually designed for going under your sink we even have more to you in it as well now this is getting increasingly less like a vacuum cleaner there we are what this is now is a bazooka just check this works I don't even know how to switch this on there we go when the vacuum cleaner is on the pressure in this tube the air pressure will be lower than the pressure around the tube because it's pulling air through now that means that the higher pressure air around it is going to push in through these holes so it'll push in through there and it'll push in through there but if we block this hole then all of that air pressure is only pushing in through that end but what if we then put what we have uh we call it a sort of safe sausage uh it just in case anybody gets anywhere into this it is very soft contains blue Tac and bubble wrap and other Pleasant soft stationary items but there will be air pressure behind that projectile which will push it along the tube because the air can't get in here it should push it all the way along here now what do you think will happen to that projectile when it gets to this end a few mumbled ideas nobody's truly confident are they what do you think will happen someone shout out with a few different ideas somebody said it would get stuck might do um some say it's getting sucked down the tube yeah might do quite a tight corner but let's see what actually happen so remember air pressure pushing the projectile the air pressure can't go this way it's going to go along this tube and then we'll see what happens now it's your opportunity to shoot me okay y okay turn it [Music] on you ready three three 2 1 [Applause] [Music] so when it gets to this end it's already moving so quickly having been pushed by the weight of the air along the tube that it actually shoots past this bit and because there's only this much tube at this end it only gets sucked back a little tiny bit so it ends up with lots of momentum going that way and it heads off and I can shoot my boss one more okay we turn it on and we block this end and 3 2 [Applause] 1 and that is how you turn a vacuum cleaner into a bazooka we go now can anyone tell me what the vast majority of this room is full of don't say people air and what's it made of yeah it's a mixture of gases and about one part in five is the stuff we need oxygen because without oxygen we asfixiate but four fths of the air four fths 80% of Every Breath You Take is the gas nitrogen and I've actually got some here because in this container I have got some nitrogen which we have turned into a liquid this is at about- 200° C so I'm going to try to get some out I might struggle actually can we get the um projector on so would you mind refilling so what I've got in this cup is a liquid which is liquid nitrogen so if you take the air in the room and squeeze it down into a very small space and take all the heat away it will condense into a liquid which you see in front of you and this is actually boiling in the same way as your Kettle would boil in your kitchen at 100° C this is boiling at minus 200° C if I put my hand in there it would very quickly within seconds turn to solid ice and if I hit it with a hammer I could smash my fingers into a million pieces I'm not going to suggest we try that but actually it's quite funny because in Scandinavia there's a company which have decided that one answer to the environmentally friendly fuel uh funeral is to put people into liquid nitrogen when they're dead obviously and then blast them to death with sound waves ultrasound and this fragments you into millions of tiny pieces which you can then scatter in the same way as you could if someone have been crated the difference is if you if you're crated it takes about seven gallons of diesel equivalent to Crate someone so this is viewed as a slly more energy uh or a slightly more environmentally friendly alternative but with something this cold and if I blow into here you can see that's water vapor it means that we can take energy away from things very very efficiently and very very quickly so if I take these rather nice flowers which Ben gave to me this morning I love you too Ben lovely if I put these in we'll see what flowers look like at minus about 200° so all that steam came off because that's the energy and the flowers being taken away as the nitrogen boils and now we've got flowers which are beautiful but very very cold watch this that's why I was unen to put my hand in there should we do it [Applause] again okay so it's just freezing the flour so the flour was floppy and now it's not and the reason for that is that all of the proteins that make up the tissue of the flour are normally long chains of molecules which have energy and these chains of molecules can wriggle around and slip past each other very easily which makes them Wiggly but if you make them very very cold they stop moving very fast and they can't slip past each other very easily and that's what makes the whole thing very brittle not so pretty now which is it anyone fancy doing the washing up who likes doing the washing up oh I bet this is a rubber glove and it's really stretchy and the reason it's stretchy is because latex polymers which are rubber are long chains like snakes or chains of spaghetti and at room temperature when they're warm they're vibrating and moving around very fast and this means that if I stretch the rubber These Chains which are wound up very very tightly can easily unwind and slip past each other very easily to make the rubish stretch but if we take all the energy away from them with the cold liquid nitrogen they'll slow down and stop and as a result it's much more difficult for them to slip past each other and so the rubber glove should turn into the clothing equivalent of those flowers should you have a go okay here we go so we'll put the glove into the liquid nitrogen cool it down there it is doesn't look much different does it until you do this so not quite so useful [Applause] now now one one other thing I wanted to demonstrate to you was I've just got a balloon here which is full of air and the the balloon is inflated because I blew this up earlier the air molecules in here have energy from the room there zipping around very very fast if this was full of helium some of them would be moving at speeds of up to 2 km a second very very rapid movement and that means that the molecules are continuously hitting the side of the balloon and pushing on it pushing it outwards and that's why the balloon is inflated so if we take energy away from those molecules we slow them down and if we slow them down they don't hit the side of the balloon so hard so the balloon should go down so let's find out I've just got some more liquid nitrogen in this other bucket here so if if I put the balloon into this we should see it shrink and as a result it's much smaller now if you watch what happens as it gets hot again and soaks up energy from the room the gas speeds up pushes on the side of the bloom much harder and the bloom reinflates itself okay so now we can now we can use that principle with a in a cunning little experiment which you can do at home perfectly well now this is a Hightech piece of scientific apparatus known as a bin bag in fact a particularly cheap bin bag and this is a piece of high-tech kitchen apparatus known as a toaster in fact it's a particularly cheap toaster there's a theme running here okay anyone have any guess how much air what weight of air is in this bag just shout out 100 100 what three Gant elepant 100 elephants worth of air in that bag got fairly wide range of guesses about five gram okay I'll tell you the answer it's actually about 50 g of air which air is actually heavier than you think each liter of air weighs about a gr each cubic meter of air weighs about a kilogram so there's probably best part of a ton of air in this room so air is heavier than you expect okay so if we make that air hotter what's it going to do it's going to expand if it starts off full of air will it all fit something's going to fall out it's going to get less air in the bag and so the bag and the air inside it's going to get lighter and lighter and lighter if you put something lighter than water in water what happens floats floats so should we find what happens if you put something lighter than air in air okay now this is another piece of technical apparatus this is years of development and Dave's time spent in his lab has worked out that the best thing to do to protect a toaster from a plastic bag is shove a bit of cardboard on it otherwise you end up with plastic in the toaster and plastic flavored toast is not good so the toaster is on and that's heating up the air inside this bag as we've just seen from the nitrogen when air gets hotter it gets bigger takes up more space so we can watch as the air inside this bag takes up more space and some of it is going to spill out from underneath so now there's less air here than there is in the same shape next to it and this stuff next to it it's going to have to go somewhere it's going to go underneath it [Music] gently what we just built a hot air balloon this is exactly how hot air balloons work except you these toasters you'd need a hell of a toaster and the cable would be a right pain to drag around the countryside it would take the whole fun out of it okay we got one more little demo related to that we're going to heat up some air in a slightly different way instead of using a toaster we're going to make a fire if Ben can get at the fuel don't have any fingernails ah there we are right this is normal ligh of fuel that we're using so nothing unusual about this you can buy this in many different news agents for zipper lighters and unsurprisingly if you set fire to lighter fuel it burns do I not get a round of applause what direction the Flames going in up that's cuz the air is very hot it's expanded and it's floating upwards now we're going to do something slightly odd I put this little Grill around the outside so as the air is floating upwards more air is coming in from the side to take its place what I'm going to do is make that air coming in from the side spin can we drop the lights a bit please lights down please there we go I stop it stops go the other way it's really nice and warm here it's toasty okay can we have the lights up again quickly now so what's happening is the air coming in from the sides is being forced to spin Slowly by this Grill now bizarrely this is very related to ice skating has anyone seen any ice skaters on TV recently on the Winter Olympics you ever seen them do those really fast spins what they do is they spread their weight out they sort of stick their bum out one way they stick their leg out the other way and spread their weight out a long way and they start to spin slowly and they pull all their weight into the middle and they go really fast yeah and exactly the same thing is happening with this Grill the air on the outside is spinning slowly as it's been pulled into the center it's spinning faster and faster so you get this really really beautiful spinning flame have you ever heard of a hurricane same principle but less fire you get some very hot water you get hot air above it that floats upwards drags in air from the sides but because it's so so hot water the water so hot it's dragging in so much air cuz the Earth is spinning that air which you're dragging in is spinning so as it comes inward it goes sp spins faster and faster and faster until it's moving fast enough to pick up a car and hurl it around the place scary things now another reason why things can float is because they are less dense than air and we showed you how to make a hot air balloon by making the air inside a balloon way less than the air around it make it spread out and expand another of doing this is to use a gas that's less dense so this balloon and this balloon have got gases in them that are less dense than the air around them does anyone know what this gas might be yeah it could be hydrogen or it could be helium now unfortunately helium is quite expensive and I couldn't find any so I had to fill it up with hydrogen but it's floating and the reason it's floating is because the hydrogen is pushing out of the way to fill the balloon more air than the hydrogen ways itself so the balloon keeps on Rising either until the string runs out or until the amount of air it's pushing out of the way weighs the same as the hydrogen and the balloon together do and that's why balloons work but one other thing about hydrogen of course is what yeah it Burns quite well so I thought we'd have a go would anyone like me to try it carefully um I'm going to wear some ear Defenders you might want to put your fingers in your ears um what's going to happen hopefully is that I'm going to put a flame to this balloon and hopefully the hydrogen will begin to mix with oxygen in the air and it should go back B you might just hear it just take just doing this as a precaution okay do you want to count me in 3 2 [Applause] 1 did anyone miss it anyone asleep now now what happened is that hydrogen mixed with oxygen from the air and hydrogen reacts with oxygen to make what water yeah so two hydrogen molecules 2 H2O mixes with one oxygen molecule O2 and they react to make two molecules of water but they also release enormous amounts of energy and the reason you hear a nice big bang is because this energy heats the air around the site of explosion and this causes the air to expand but it does so very very quickly f faster than it can actually get out of the way and this creates a shock wave and that's why you hear a thump the problem is the reaction's quite slow believe it or not because the hydrogen's all in one place and the Oxygen's in the air and the two have to mix before they can react together can anyone think how you'd speed up the reaction well the answer is you mix the two together and it's very dangerous so that's what we've done so uh in this balloon uh I've got just the right amount of hydrogen and oxygen mixed together so it should react faster and that means that the shock wave we get should be a little bit faster and therefore a little bit more of a thump so you might if you missed the first one you might hear this one if it works really want to put your fingers in your ears for this one okay do should we Count 2 1 [Applause] okay so that's kind of impressive I'll give it that but not especially useful makes a lot of noise but otherwise not very much I'm going to try and use the same reaction to do something a little bit more useful what I've got here is a lemonade bottle with a bit of hydrogen in it and quite a lot of air mies the right quantities roughly roughly not really Precision science this one B if you got lighter I'm going to put it down this tube and the thing about um lemonade bottles is they're actually very very strong so if we can create cause a reaction to happen in here all that gas or that explosion or that expansion of gas can can only get get out in One Direction so we're going to get lots and lots of gas going in One Direction now if you push something it has to push you back so if the B which Isaac Newton worked out few hundred years ago so if the bottle is pushing lots of gas downwards then the gas is going to push the bottle upwards I can so ready 3 2 1 what if I just built a rocket this is actually exactly how space rockets work the space shuttle reacts hydrogen and oxygen they actually get a lot more of it in a small space react hydrogen oxygen together they get very very hot they expand and push downwards really really gets pushed downwards really fast that pushes the rocket upwards should I try [Applause] again if I can make the three [Applause] two again now earlier on using the liquid nitrogen which I'll do over here using the liquid nitrogen we showed you that when you put a balloon it's normally full of air and you make it very cold it'll get smaller now that's partly because it has less energy so it takes up less space but all of the different gases in air if you get them cold enough can we have the projector on please yeah we'll need it for this if you get them cold enough they actually become a liquid now if you look in the bottom of there now I don't know if you can see that or not it's looking good if you look in the bottom of there you should should see a bit of liquid air and that's there probably just over just about a teaspoon just under a teaspoon maybe of liquid air in there and it fairly quickly long as I keep it moving the balloon doesn't break fairly quickly expands to become gaseous air again and so that just less than a teaspoon actually takes up quite a lot of space now that in itself is quite cool it's quite nice to see that you can liquefy air so easily but but it's also the basis of our next experiment for which you once again will probably need to put your fingers in your ears you got a while yet out okay okay I'm now going to do something which in every safety manual involving liquid nitrogen it tells you not to do that's why we're doing it what I'm going to do is I'm going to put a little bit of liquid nitrogen in a lemonade bottle the lemonade bottles I Sayang earlier are very very strong and that's perfectly safe there's nothing wrong with that then what I'm going to do is put the lid on the problem with that is liquid nitrogen when it expand you saw that liquid gas when it expanded liquid air when it expanded it expanded about 600 times when it boils so I don't have to put very much liquid nitrogen in this bottle to expand enough to fill up the bottle in fact I could put enough liquid nitrogen to fill this bottle 100 times in here easily so slowly as this liquid nitrogen boils it's going to produce more and more gas and there's nowhere for that gas to go so that gas is going to push harder and harder and harder on the bottle until something gives and the thing about um lemonade bottles is they're very very strong so nothing gives for a very long time that's got a good amount of liquid ntion on in there I'm going to do it in a bin around here so it's not too loud for you guys no you you probably can't look just to show you what we' there's a bin here and this big sheet we're putting over the top so sorry you guys can't see it in most of you can't see it but we'll have the camera on it and you should hear it I expect that's okay yeah some defense okay so there is a dust bin around the back there okay so I'm going to put the lid on now I'm going to cover it up and then I'm going to retreat and I'm going to give the camera [Applause] a sorry we you probably about to find the remnants of the bottle which aren't especially big thank you guys well that's pretty much our [Applause] show I'd like to say a very big thank you to two wonderful guys who work with me on the naked scientists Dave anel and Ben vler and incidentally if you want to have some experiments you can try it home quite safely we actually published a book called Chris packet fireworks which is out now it's on sale you can get it from Amazon if you get it from the naked scientist.com you can actually get it cheaper than you can from the bookstore so n scientist.com and have a look for Chris packet fireworks and you can get hold of a whole bunch of experim you can do safely at home now have you had enough yeah you people going out you really regret leaving now don't you yeah would you like one more experiment well I think some people smell a bit so I thought some of you could use a bath so we bought this paddling pool it's actually uh magic of the Rainbow very nice isn't it um but what we're going to do what we've got is a very large bin full of very hot water and what we've dissolved in this very hot water is a whole bottle of bubble bath and because we don't like wasting stuff on the Naked Scientist and we've got a very large amount of liquid nitrogen left um we thought we'd find out what happens if you put a very large amount of liquid nitrogen in the region of several liters into a full bin with a whole bottle of bubble bath dissolved in it now um as uh as we showed you with that bottle when liquid nitrogen turns from a liquid into a gas it expands by a factor of 600 times so if I put 2 L of liquid nitrogen in there it will soak up all of the energy from the hot water and turn into 1 12200 lers okay 1 and a half cubic meters of gas and it will do that underneath bubbly fluid with a whole bottle of bubble bar dissolved in it but where are you going with my microwave nowhere um shall we have a go now I'm just going to do my lab coat up because um and and I'm just going to adjust my trousers because um I did this once before and it it all went up my trouser leg I've got two children conceived beforehand hand so probably all right okay now we only have one go at doing this uh because once the nitrogen's gone it's gone so we only have you there's no on core I'm afraid so this really is it sounds like Michael Jackson This Is It uh so I'm going to pour the whole bucket into there and hopefully survive the experience and so will you people at the front Okay thank you very much for coming I hope you've enjoyed our show and hopefully we'll see you again next year he are you ready yes can we count down from three 3 2 [Applause] 1 thank you hey here for the Naked Scientist come on cish make some noise