1 00:00:07,440 --> 00:00:10,800 This is a film about bubbles. 2 00:00:12,000 --> 00:00:16,960 To most people, bubbles are just toys children play with. 3 00:00:18,760 --> 00:00:22,160 But they're so much more. 4 00:00:23,520 --> 00:00:27,280 They're amazingly powerful tools that are pushing back 5 00:00:27,280 --> 00:00:28,880 the boundaries of science. 6 00:00:30,360 --> 00:00:34,040 I'm a bubble physicist and the reason that I care about bubbles 7 00:00:34,040 --> 00:00:36,720 is that they're part of how the planet works. 8 00:00:36,720 --> 00:00:41,520 Out at sea, breaking waves generate huge plumes of bubbles 9 00:00:41,520 --> 00:00:44,400 and those bubbles help the oceans breathe. 10 00:00:45,840 --> 00:00:49,920 Then there's the soap bubble with its delicate, fragile skin, 11 00:00:49,920 --> 00:00:53,880 something we can all see and touch, yet it can tell us 12 00:00:53,880 --> 00:00:58,160 about how nature works on scales as large as our solar system... 13 00:00:59,160 --> 00:01:02,800 ..and as small as a single wavelength of light. 14 00:01:04,560 --> 00:01:07,880 Here we've identified what we think are interesting questions 15 00:01:07,880 --> 00:01:10,440 that will open up new areas in mathematics. 16 00:01:10,440 --> 00:01:14,800 We're learning that bubbles influence our world 17 00:01:14,800 --> 00:01:17,440 in all sorts of unexpected ways. 18 00:01:19,680 --> 00:01:21,520 From animal behaviour... 19 00:01:22,680 --> 00:01:25,240 ..to the sounds of running water. 20 00:01:27,280 --> 00:01:29,520 And even the way drinks taste. 21 00:01:30,960 --> 00:01:35,480 The bubble cavity collapses, it can eject a tiny champagne jet 22 00:01:35,480 --> 00:01:38,080 up to several centimetres above the surface. 23 00:01:40,400 --> 00:01:42,760 And perhaps most exciting of all, 24 00:01:42,760 --> 00:01:45,600 we're only just beginning to appreciate 25 00:01:45,600 --> 00:01:47,600 the potential of bubble science. 26 00:01:49,680 --> 00:01:52,200 But there's still so much we don't know about bubbles, 27 00:01:52,200 --> 00:01:53,800 so much to learn. 28 00:01:53,800 --> 00:01:57,680 These little things are full of secrets and surprises. 29 00:01:59,360 --> 00:02:03,960 Welcome to my world. The wonderful world of bubbles. 30 00:02:25,240 --> 00:02:27,600 Bubbles really matter to our planet. 31 00:02:28,600 --> 00:02:32,040 Three quarters of the Earth is covered in water 32 00:02:32,040 --> 00:02:35,920 and just under the ocean's surface are billions of bubbles, 33 00:02:35,920 --> 00:02:39,320 formed as breaking waves drag air underwater. 34 00:02:42,560 --> 00:02:44,120 Right in front of our eyes, 35 00:02:44,120 --> 00:02:47,360 these bubbles are playing an important but invisible role. 36 00:02:50,840 --> 00:02:53,760 At a bubble, the ocean and atmosphere meet 37 00:02:53,760 --> 00:02:55,480 and both are affected. 38 00:02:58,640 --> 00:02:59,960 And this is all thanks 39 00:02:59,960 --> 00:03:03,160 to just a handful of a bubble's fundamental properties, 40 00:03:03,160 --> 00:03:05,920 which we're learning about in ever more detail. 41 00:03:07,880 --> 00:03:09,800 And that's the focus of my work, 42 00:03:10,880 --> 00:03:13,120 both out at sea 43 00:03:13,120 --> 00:03:16,360 and here in my laboratory at Southampton University. 44 00:03:18,720 --> 00:03:21,480 If we understand the basic processes of bubble formation 45 00:03:21,480 --> 00:03:23,880 in different situations in the ocean, 46 00:03:23,880 --> 00:03:26,280 we will be able to use that information 47 00:03:26,280 --> 00:03:28,000 to improve weather and climate models. 48 00:03:28,000 --> 00:03:30,440 You wouldn't think that something so small 49 00:03:30,440 --> 00:03:33,880 could affect something as big as a weather system, but it can. 50 00:03:37,120 --> 00:03:40,160 Let me start with a simple question... 51 00:03:41,480 --> 00:03:43,720 What is a bubble? 52 00:03:45,040 --> 00:03:48,080 There are two different but related kinds. 53 00:03:50,200 --> 00:03:55,120 The first are these - underwater bubbles, the focus of my research. 54 00:04:02,400 --> 00:04:08,320 But the bubbles most people know are these - soap bubbles. 55 00:04:10,640 --> 00:04:14,040 Despite being made of the most mundane of substances - 56 00:04:14,040 --> 00:04:16,760 soap, air and water - 57 00:04:16,760 --> 00:04:18,760 they're incredibly beautiful. 58 00:04:24,120 --> 00:04:27,200 These ethereal objects and the lessons they can teach us 59 00:04:27,200 --> 00:04:30,200 have fascinated scientists for decades. 60 00:04:37,280 --> 00:04:41,880 As the most famous of Victorian physicists, Lord Kelvin said... 61 00:04:43,080 --> 00:04:45,600 "Blow a soap bubble and observe it. 62 00:04:45,600 --> 00:04:47,720 "You may study it all your life 63 00:04:47,720 --> 00:04:50,920 "and draw one lesson after another in physics from it." 64 00:04:56,720 --> 00:05:00,600 Kelvin was fascinated by the way the delicate skin of the bubble 65 00:05:00,600 --> 00:05:03,240 affected the behaviour of light. 66 00:05:06,760 --> 00:05:09,840 And in particular, the beautiful colours it reveals. 67 00:05:19,480 --> 00:05:24,040 Just look at the fantastic patterns on this soap film here. 68 00:05:24,040 --> 00:05:26,840 They're there because the film is so thin - 69 00:05:26,840 --> 00:05:30,440 it's only a few hundredths of the diameter of a human hair. 70 00:05:32,480 --> 00:05:35,520 That means a soap film is around the same thickness 71 00:05:35,520 --> 00:05:38,880 as a single wavelength of visible light. 72 00:05:40,280 --> 00:05:43,200 The different colours on the film correspond to different 73 00:05:43,200 --> 00:05:45,720 wavelengths of light in the spectrum. 74 00:05:48,080 --> 00:05:51,200 And what fascinated Kelvin and scientists like him was, 75 00:05:51,200 --> 00:05:53,040 "How is this possible? 76 00:05:53,040 --> 00:05:56,040 "How can something so thin possibly exist?" 77 00:05:57,160 --> 00:06:00,040 And the answer is to do with the weird nature 78 00:06:00,040 --> 00:06:02,640 of something very everyday...water. 79 00:06:17,320 --> 00:06:20,640 So this is just freshwater and one of the things 80 00:06:20,640 --> 00:06:23,720 we associate most with liquids is droplet formation, 81 00:06:23,720 --> 00:06:28,160 so I'm going to use my sleeve and put some drops of water on it. 82 00:06:29,560 --> 00:06:31,400 And they're really pretty! 83 00:06:31,400 --> 00:06:33,920 You can see that these droplets are sort of curved inwards 84 00:06:33,920 --> 00:06:37,120 and the reason for that is that the water molecules on the surface 85 00:06:37,120 --> 00:06:40,480 are being pulled into the bulk of the water really strongly 86 00:06:40,480 --> 00:06:41,800 just on one side. 87 00:06:41,800 --> 00:06:47,080 So water behaves as though it's covered with an elastic skin, 88 00:06:47,080 --> 00:06:49,760 and we call that surface tension. 89 00:06:55,800 --> 00:06:58,520 Surface tension is one of the most delicate 90 00:06:58,520 --> 00:07:01,120 and intriguing forces in all of nature 91 00:07:01,120 --> 00:07:04,200 and its causes lie with the shape of the water molecule. 92 00:07:06,520 --> 00:07:10,160 Something very strange happens when hydrogen and oxygen - 93 00:07:10,160 --> 00:07:12,960 the atoms it's made of - join together. 94 00:07:14,240 --> 00:07:17,960 And the reason for that is that when the hydrogens join the oxygen, 95 00:07:17,960 --> 00:07:20,520 the molecule doesn't become a straight line, 96 00:07:20,520 --> 00:07:22,720 there's a kink in it, and so overall, 97 00:07:22,720 --> 00:07:25,480 one side of the molecule has a slight positive charge 98 00:07:25,480 --> 00:07:28,160 and the other side has a slight negative charge. 99 00:07:28,160 --> 00:07:32,080 What that means is that when other water molecules come close, 100 00:07:32,080 --> 00:07:33,520 the positive side of one 101 00:07:33,520 --> 00:07:37,280 is attracted to the negative sides of the other, and so overall, 102 00:07:37,280 --> 00:07:40,320 the bonds that attract water molecules to each other 103 00:07:40,320 --> 00:07:42,640 are really, really strong. 104 00:07:44,360 --> 00:07:47,760 These bonds mean that the molecules in the body of the water 105 00:07:47,760 --> 00:07:49,840 are pulled equally in every direction. 106 00:07:51,160 --> 00:07:55,120 But the molecules on the surface are pulled inwards... 107 00:07:55,120 --> 00:07:58,560 making the surface of the water like an elastic sheet. 108 00:07:59,560 --> 00:08:02,760 This is critical for understanding all the amazing properties 109 00:08:02,760 --> 00:08:04,520 of soap bubbles. 110 00:08:08,520 --> 00:08:09,800 But how? 111 00:08:09,800 --> 00:08:13,040 And crucially, why can't you make bubbles with pure water, 112 00:08:13,040 --> 00:08:14,480 why do you need soap? 113 00:08:15,720 --> 00:08:20,000 This was a surprisingly difficult question to answer 114 00:08:20,000 --> 00:08:23,800 and the key to solving it came not from the great men 115 00:08:23,800 --> 00:08:28,600 of Victorian science, but from an obscure house in Germany. 116 00:08:31,600 --> 00:08:34,280 Some of the earliest experiments on surface tension were done 117 00:08:34,280 --> 00:08:36,800 by a German lady called Agnes Pockels 118 00:08:36,800 --> 00:08:39,840 and her work was only published in 1891. 119 00:08:39,840 --> 00:08:41,960 I've got a copy of the paper here. 120 00:08:41,960 --> 00:08:47,640 The paper is prefaced by a note by Lord Rayleigh, 121 00:08:47,640 --> 00:08:50,920 who was a very famous English physicist, and this is what he said 122 00:08:50,920 --> 00:08:52,920 and this was his note to Nature. 123 00:08:52,920 --> 00:08:54,880 "I shall be obliged if you can find space 124 00:08:54,880 --> 00:08:57,680 "for the accompanying translation of an interesting letter 125 00:08:57,680 --> 00:09:00,160 "which I have received from a German lady, 126 00:09:00,160 --> 00:09:03,840 "who with very homely appliances has arrived at viable results 127 00:09:03,840 --> 00:09:07,600 "respecting the behaviour of contaminated water surfaces." 128 00:09:07,600 --> 00:09:10,360 The reason that he wrote the preface is because 129 00:09:10,360 --> 00:09:12,360 Agnes was born in 1862 in a time 130 00:09:12,360 --> 00:09:16,560 when women were not allowed to study physics to any great degree 131 00:09:16,560 --> 00:09:18,000 or to go to university, 132 00:09:18,000 --> 00:09:21,120 and so she was not allowed to publish the paper herself. 133 00:09:22,800 --> 00:09:26,760 The first thing Agnes did, just using the equipment in her kitchen, 134 00:09:26,760 --> 00:09:29,560 was come up with a new and incredibly clever way 135 00:09:29,560 --> 00:09:32,160 of measuring the surface tension of water. 136 00:09:33,160 --> 00:09:35,680 I've got a version of her experiments here 137 00:09:35,680 --> 00:09:40,640 and what she was looking at was how hard surface tension can pull 138 00:09:40,640 --> 00:09:42,320 and she had this experiment... 139 00:09:42,320 --> 00:09:45,480 Now, she describes it as a small disc at the bottom 140 00:09:45,480 --> 00:09:48,360 and that's been interpreted as being a button, 141 00:09:48,360 --> 00:09:49,880 so I've got a button on mine. 142 00:09:49,880 --> 00:09:52,640 My button is held by elastic thread 143 00:09:52,640 --> 00:09:56,720 and so the elastic thread is pulling upwards on the button 144 00:09:56,720 --> 00:09:59,040 and if I let it go, 145 00:09:59,040 --> 00:10:02,000 you'll see it hangs quite a long way above the water surface. 146 00:10:02,000 --> 00:10:05,200 But when the button is touching the water, 147 00:10:05,200 --> 00:10:07,400 the surface tension is pulling the button down 148 00:10:07,400 --> 00:10:09,480 and the elastic is pulling the button up, 149 00:10:09,480 --> 00:10:12,640 and Agnes realised that you could measure surface tension 150 00:10:12,640 --> 00:10:17,000 by adjusting the pull from above 151 00:10:17,000 --> 00:10:20,240 just until you got to the point 152 00:10:20,240 --> 00:10:23,400 where the button was just about to break away, 153 00:10:23,400 --> 00:10:25,880 and that moment there is when the forces are balanced. 154 00:10:25,880 --> 00:10:28,440 She had scales effectively that measured 155 00:10:28,440 --> 00:10:30,600 how much upward pull there was 156 00:10:30,600 --> 00:10:33,120 and so she knew how much downward pull 157 00:10:33,120 --> 00:10:34,880 the water was providing. 158 00:10:39,240 --> 00:10:42,600 But what Agnes did next was the really clever bit 159 00:10:42,600 --> 00:10:46,360 and it would be the key to understanding soap bubbles... 160 00:10:46,360 --> 00:10:48,640 Why they exist and what they do. 161 00:10:50,360 --> 00:10:54,480 Agnes realised that you could also use this device to measure 162 00:10:54,480 --> 00:10:58,080 how surface tension changed in different situations. 163 00:10:58,080 --> 00:11:00,920 What she did was, she contaminated the surface. 164 00:11:00,920 --> 00:11:02,960 This is just detergent. 165 00:11:02,960 --> 00:11:06,240 I'm just going to put a few spots of it nearby 166 00:11:06,240 --> 00:11:08,320 and as I put them on the water surface, 167 00:11:08,320 --> 00:11:11,160 the detergent is lowering the surface tension 168 00:11:11,160 --> 00:11:13,800 and so the button will pop off the surface. 169 00:11:16,880 --> 00:11:20,120 Agnes' measurements showed that adding soap to water 170 00:11:20,120 --> 00:11:22,160 reduces its surface tension. 171 00:11:23,360 --> 00:11:25,240 That's a crucial observation. 172 00:11:26,320 --> 00:11:29,720 It's the answer to the first question about soap bubbles... 173 00:11:32,840 --> 00:11:37,240 And why you can't make bubbles with clean or pure water. 174 00:11:40,040 --> 00:11:43,960 If you make bubbles in clean water and they rise to the surface, 175 00:11:43,960 --> 00:11:47,160 they make a spherical lid like this for a very short period of time 176 00:11:47,160 --> 00:11:50,720 and then the surface tension of the water is so strong 177 00:11:50,720 --> 00:11:52,280 that it pulls this film 178 00:11:52,280 --> 00:11:55,080 and breaks it up into lots and lots of tiny, tiny droplets, 179 00:11:55,080 --> 00:11:58,640 so clean water has surface tension which is far too strong 180 00:11:58,640 --> 00:12:01,160 to let foam like this last 181 00:12:01,160 --> 00:12:03,440 and that's where the bubblebath comes in. 182 00:12:04,600 --> 00:12:08,280 The soap molecules in the bubblebath position themselves 183 00:12:08,280 --> 00:12:11,080 at the surface of the water, 184 00:12:11,080 --> 00:12:13,280 changing how the surface behaves. 185 00:12:18,320 --> 00:12:20,400 If we look at one of these bubbles here, 186 00:12:20,400 --> 00:12:23,200 the reason that this thin film can exist for so long 187 00:12:23,200 --> 00:12:26,600 is that the soap molecules have reduced the water surface tension, 188 00:12:26,600 --> 00:12:30,640 so the pull to make that pop isn't as strong as it was. 189 00:12:30,640 --> 00:12:33,840 The soap molecules are allowing these thin films, 190 00:12:33,840 --> 00:12:36,920 beautiful thin films, to last for a really long time. 191 00:12:37,920 --> 00:12:39,800 But the fact that soap and water 192 00:12:39,800 --> 00:12:42,120 can combine to make something so thin... 193 00:12:43,520 --> 00:12:46,400 ..doesn't just mean that we have beautiful toys to play with. 194 00:12:47,800 --> 00:12:49,680 Soap films are helping us solve 195 00:12:49,680 --> 00:12:51,960 the toughest mathematical problems in nature. 196 00:12:58,560 --> 00:13:01,200 These are the storms in Jupiter's atmosphere. 197 00:13:04,120 --> 00:13:07,960 This is a massive example of one of these tough problems - 198 00:13:07,960 --> 00:13:11,000 the complex ways that fluids flow. 199 00:13:12,200 --> 00:13:16,960 And this is that process, recreated on the surface of a soap bubble. 200 00:13:20,080 --> 00:13:22,200 Fluid flows really beautiful, 201 00:13:22,200 --> 00:13:24,480 but it's also really difficult to study 202 00:13:24,480 --> 00:13:26,000 and soap films can help 203 00:13:26,000 --> 00:13:30,280 because by following the colours on the surface of the film 204 00:13:30,280 --> 00:13:33,920 you can track how the fluid is moving and that gives you a way into 205 00:13:33,920 --> 00:13:39,160 studying systems that are otherwise either inaccessible or invisible. 206 00:13:41,560 --> 00:13:44,560 These are clouds above the Indian Ocean. 207 00:13:44,560 --> 00:13:47,440 They form these patterns - vortices - 208 00:13:47,440 --> 00:13:49,760 as they get blown around an island. 209 00:13:51,800 --> 00:13:53,400 These and other flow patterns - 210 00:13:53,400 --> 00:13:56,760 for instance, the way that water travels around a solid object - 211 00:13:56,760 --> 00:14:01,240 can be replicated and studied in soap films in a laboratory. 212 00:14:10,760 --> 00:14:14,480 And it's not just questions about fluid flow that soap films 213 00:14:14,480 --> 00:14:15,880 could help answer. 214 00:14:22,360 --> 00:14:26,200 Soap films are mathematical problem solvers. 215 00:14:28,000 --> 00:14:30,840 You can see it in their almost uncanny search 216 00:14:30,840 --> 00:14:32,800 for geometrical perfection. 217 00:14:35,080 --> 00:14:38,280 Left to themselves, they're perfect spheres. 218 00:14:40,600 --> 00:14:42,480 But they can do other tricks too. 219 00:14:44,200 --> 00:14:47,440 For instance, what's the most efficient way 220 00:14:47,440 --> 00:14:49,680 to join these four points? 221 00:14:49,680 --> 00:14:54,240 Blow on the soap film, and it finds precisely the right answer. 222 00:14:59,480 --> 00:15:03,400 All these angles are exactly 120 degrees. 223 00:15:06,280 --> 00:15:08,960 Soap films do this because of surface tension, 224 00:15:08,960 --> 00:15:12,480 pulling in every direction on the bubble's surface. 225 00:15:16,120 --> 00:15:20,880 That means a soap film will always try and minimise its surface area. 226 00:15:24,520 --> 00:15:28,040 Free-floating bubbles are spherical because that's the shape 227 00:15:28,040 --> 00:15:30,560 with the least amount of surface for any given volume. 228 00:15:33,600 --> 00:15:36,280 The soap film connects the four points like this 229 00:15:36,280 --> 00:15:39,040 because it's the arrangement with the least surface area. 230 00:15:42,240 --> 00:15:46,040 And what's really amazing is that this ability of soap films 231 00:15:46,040 --> 00:15:50,840 to minimise their area is still at the forefront of science. 232 00:16:13,480 --> 00:16:16,560 In nature, these are common occurrences. 233 00:16:17,920 --> 00:16:20,200 They're called "singularities," 234 00:16:20,200 --> 00:16:23,920 sudden changes in shape or structure. 235 00:16:27,120 --> 00:16:30,760 They're incredibly hard to describe and understand mathematically. 236 00:16:32,640 --> 00:16:35,280 And that's where soap films come in. 237 00:16:38,560 --> 00:16:43,960 Here's one captured by a camera that slows down time fifty-fold. 238 00:16:45,040 --> 00:16:47,240 Stretched between two hoops, 239 00:16:47,240 --> 00:16:49,920 it suddenly splits into two, 240 00:16:49,920 --> 00:16:51,240 instantly changing 241 00:16:51,240 --> 00:16:53,720 from one shape into another. 242 00:16:58,880 --> 00:17:03,040 This is Professor Ray Goldstein at Cambridge University. 243 00:17:03,040 --> 00:17:07,080 For him, the soap film could be a vital clue to understanding 244 00:17:07,080 --> 00:17:08,640 the singularity. 245 00:17:11,400 --> 00:17:12,720 You see them all the time... 246 00:17:12,720 --> 00:17:14,480 When a drop of fluid breaks up. 247 00:17:14,480 --> 00:17:17,280 When certain structures come off of the sun 248 00:17:17,280 --> 00:17:19,640 they form these beautiful arcing filaments 249 00:17:19,640 --> 00:17:22,000 and give rise to huge ejections from the sun. 250 00:17:22,000 --> 00:17:24,520 So on every length scale you can imagine... 251 00:17:24,520 --> 00:17:27,400 And for many decades physicists and mathematicians 252 00:17:27,400 --> 00:17:30,080 have been interested in understanding the mathematics 253 00:17:30,080 --> 00:17:31,920 of what we call the singularity, 254 00:17:31,920 --> 00:17:34,400 the moment that rearrangement happens. 255 00:17:34,400 --> 00:17:38,360 And they're so non-linear, they're so hard to solve 256 00:17:38,360 --> 00:17:41,120 that we really are at the infancy of this study 257 00:17:41,120 --> 00:17:42,960 of these kinds of singularities. 258 00:17:42,960 --> 00:17:46,400 What we hope is that we'll see a pattern emerging 259 00:17:46,400 --> 00:17:50,080 that will teach us something deep about these kinds of transitions. 260 00:17:52,080 --> 00:17:55,320 And the surface tension on the soap film is the key. 261 00:17:56,280 --> 00:17:58,960 It ensures that they perform their shape changes 262 00:17:58,960 --> 00:18:00,680 with the minimum use of energy, 263 00:18:00,680 --> 00:18:03,720 which is the preferred way nature operates. 264 00:18:06,000 --> 00:18:09,120 They're also relatively easy to study in the lab. 265 00:18:09,120 --> 00:18:14,840 For us, this is a laboratory example of a singularity 266 00:18:14,840 --> 00:18:18,720 that is similar in its structure to many kinds of singularities 267 00:18:18,720 --> 00:18:20,040 that occur in nature. 268 00:18:20,040 --> 00:18:24,040 It has the advantage that we can study it in great detail in the lab. 269 00:18:24,040 --> 00:18:27,160 We can do these high-speed movies. We can do some mathematics. 270 00:18:27,160 --> 00:18:31,320 We can vary particular quantities like the viscosity of the fluid 271 00:18:31,320 --> 00:18:33,800 or the surface tension, the size of the wire, 272 00:18:33,800 --> 00:18:36,240 whereas it's difficult studying the sun 273 00:18:36,240 --> 00:18:39,040 since we can't get near the sun to fiddle with it. 274 00:18:39,040 --> 00:18:43,040 By looking at these soap films in the lab 275 00:18:43,040 --> 00:18:45,680 where we can control everything, 276 00:18:45,680 --> 00:18:48,360 we have a hope of testing our theories in a way that allows us 277 00:18:48,360 --> 00:18:51,440 to go back and forth and refine them to the point that we can finally say, 278 00:18:51,440 --> 00:18:53,560 "Yes, I think we understand what's going on." 279 00:19:07,680 --> 00:19:10,480 It's incredible that we can study the sun 280 00:19:10,480 --> 00:19:12,400 with the help of a soap film, 281 00:19:13,400 --> 00:19:15,320 that it might unlock the secrets 282 00:19:15,320 --> 00:19:18,720 behind some of the strangest phenomena in the universe. 283 00:19:24,360 --> 00:19:28,040 But amazing though they are, I want to show you that soap films 284 00:19:28,040 --> 00:19:31,600 and soap bubbles are just the start of the story. 285 00:19:35,200 --> 00:19:38,560 I want to return to the other kind of bubble I mentioned. 286 00:19:38,560 --> 00:19:40,640 The kind I study. 287 00:19:40,640 --> 00:19:42,800 Underwater bubbles. 288 00:19:42,800 --> 00:19:47,080 These are pockets of gas that are trapped within liquids. 289 00:19:50,640 --> 00:19:53,960 They're a treasure chest of scientific riches 290 00:19:53,960 --> 00:19:55,440 and they affect everything 291 00:19:55,440 --> 00:19:57,920 from animal behaviour to the taste of champagne. 292 00:20:01,960 --> 00:20:04,920 And they make a surprisingly important contribution 293 00:20:04,920 --> 00:20:07,080 to the Earth's climate. 294 00:20:11,480 --> 00:20:14,360 I want to start this story here in this pool, 295 00:20:14,360 --> 00:20:18,400 which is equipped to make huge plumes of underwater bubbles. 296 00:20:20,200 --> 00:20:23,960 We'll see these underwater bubbles dramatically change the properties 297 00:20:23,960 --> 00:20:26,120 of the liquid they move in. 298 00:20:26,120 --> 00:20:30,000 And that can be incredibly useful. 299 00:20:30,000 --> 00:20:34,480 In this pool, it's used to help train springboard divers. 300 00:20:37,880 --> 00:20:40,800 Diving pools like this have a big air reservoir underneath. 301 00:20:40,800 --> 00:20:43,240 They can send a big plume of bubbles up and that means that 302 00:20:43,240 --> 00:20:44,960 when a diver is learning a dive, 303 00:20:44,960 --> 00:20:48,200 they come down and instead of hitting flat water, 304 00:20:48,200 --> 00:20:50,840 they hit bubbly water with a lower density, 305 00:20:50,840 --> 00:20:54,040 so that instead of having a short, sharp shock, 306 00:20:54,040 --> 00:20:56,760 they get slowed down but over a longer period of time, 307 00:20:56,760 --> 00:20:58,880 so bubbles help divers train. 308 00:21:00,240 --> 00:21:03,320 And it's because the bubbles do this that... 309 00:21:03,320 --> 00:21:05,960 although I haven't done any diving for a long time, 310 00:21:05,960 --> 00:21:08,600 I'm prepared to try it again. 311 00:21:20,120 --> 00:21:23,320 The reason bubbles make water less painful to dive into 312 00:21:23,320 --> 00:21:25,680 goes to the heart of what a bubble actually is. 313 00:21:28,800 --> 00:21:31,960 A bubble is what you get when a liquid-like water 314 00:21:31,960 --> 00:21:33,840 and a gas-like air 315 00:21:33,840 --> 00:21:37,680 that really don't want to mix are forced together. 316 00:21:39,520 --> 00:21:42,920 The surface tension of water tries to squeeze the bubble 317 00:21:42,920 --> 00:21:45,920 into having a smaller surface area. 318 00:21:46,920 --> 00:21:49,600 And the air is rising as fast as possible. 319 00:21:54,120 --> 00:21:58,160 But during their brief co-existence, they form something new, 320 00:21:58,160 --> 00:22:01,720 a mixture much more substantial than air, 321 00:22:01,720 --> 00:22:05,320 but considerably softer and less dense than water. 322 00:22:14,720 --> 00:22:17,840 It's hard to get round. That happened really quickly. 323 00:22:19,280 --> 00:22:22,640 But it's good. I did it. I haven't done that dive for six years. 324 00:22:23,800 --> 00:22:25,640 Bubbles are good, right? 325 00:22:29,440 --> 00:22:32,640 Animals that spend a lot of time underwater 326 00:22:32,640 --> 00:22:35,160 have evolved some incredibly ingenious ways 327 00:22:35,160 --> 00:22:38,920 of exploiting the fact that bubbles reduce the density of water. 328 00:22:43,520 --> 00:22:47,920 These are Emperor penguins, diving to depths of ten metres. 329 00:22:49,000 --> 00:22:51,480 They store air in their feathers 330 00:22:51,480 --> 00:22:55,240 which they release as clouds of bubbles as they zoom upwards. 331 00:22:57,280 --> 00:22:59,920 This makes the water around the penguin less dense 332 00:22:59,920 --> 00:23:01,800 and much easier to move through. 333 00:23:05,320 --> 00:23:08,800 It means the penguins can travel up to 50% faster 334 00:23:08,800 --> 00:23:10,360 than if there were no bubbles. 335 00:23:12,680 --> 00:23:16,200 I love this, because it shows just how useful bubbles are. 336 00:23:16,200 --> 00:23:19,280 It helps divers like me get into the water safely. 337 00:23:21,080 --> 00:23:24,080 And it helps the penguins get out safely. 338 00:23:39,840 --> 00:23:43,480 And in the shipping industry, there's intensive research going on 339 00:23:43,480 --> 00:23:46,960 into how bubbles can make water less dense and easier to move through. 340 00:23:51,680 --> 00:23:55,200 This tall steel drum spinning inside a cylinder of water 341 00:23:55,200 --> 00:23:58,600 is part of an experiment at a Dutch university. 342 00:24:01,920 --> 00:24:06,160 Engineers here stream bubbles in varying amounts and sizes across 343 00:24:06,160 --> 00:24:10,480 the drum's surface to learn how they reduce friction from the water. 344 00:24:15,160 --> 00:24:19,160 And in late 2012, Japanese shipbuilders Mitsubishi 345 00:24:19,160 --> 00:24:23,400 fitted a bubble lubrication system under one of their ships. 346 00:24:24,440 --> 00:24:28,840 They hope that this will reduce fuel consumption by up to 15%, 347 00:24:28,840 --> 00:24:32,000 potentially saving billions of pounds. 348 00:24:36,720 --> 00:24:40,720 Bubbles are proving to be incredibly useful to the modern world. 349 00:24:43,000 --> 00:24:46,280 The next really important use of bubbles is connected 350 00:24:46,280 --> 00:24:49,920 to one of their most surprising properties, 351 00:24:49,920 --> 00:24:52,560 their relationship with sound. 352 00:24:55,480 --> 00:24:58,000 This has all sorts of consequences - 353 00:24:58,000 --> 00:25:01,440 everywhere from industry to medical research. 354 00:25:01,440 --> 00:25:03,600 But, for me, it's a fabulous tool 355 00:25:03,600 --> 00:25:08,480 because sound lets me monitor what bubbles are doing in the ocean. 356 00:25:08,480 --> 00:25:12,240 And this will help me understand their role in our climate. 357 00:25:12,240 --> 00:25:14,800 It goes pop, pop, pop, pop. 358 00:25:14,800 --> 00:25:18,680 Bubble acoustics is a branch of science in its own right, 359 00:25:18,680 --> 00:25:23,440 but it begins with the simplest of observations. 360 00:25:23,440 --> 00:25:28,160 So, I have a tank of water here with a nozzle down at the bottom 361 00:25:28,160 --> 00:25:31,520 and I'm going to feed air into it... 362 00:25:34,560 --> 00:25:37,440 ..by pushing on a syringe here. 363 00:25:37,440 --> 00:25:40,800 So I can see there's air coming along the nozzle. 364 00:25:40,800 --> 00:25:43,680 And I'm just going to make one bubble at a time. 365 00:25:45,760 --> 00:25:47,040 And here's the thing - 366 00:25:47,040 --> 00:25:50,120 if you put your ear up against the tank, 367 00:25:50,120 --> 00:25:54,280 you can hear it's going "ping, ping, ping" for each little bubble. 368 00:25:58,560 --> 00:26:01,920 Every new bubble that's formed like this 369 00:26:01,920 --> 00:26:05,400 is like a little bell being hit with a hammer and it goes "ping". 370 00:26:07,160 --> 00:26:10,600 If you pour out a drink or you hear a babbling stream, 371 00:26:10,600 --> 00:26:12,320 this is the sound you're hearing, 372 00:26:12,320 --> 00:26:14,520 you're hearing new bubbles being formed. 373 00:26:14,520 --> 00:26:17,400 But they tell you more than that. 374 00:26:17,400 --> 00:26:19,440 Now I'm going to make some big bubbles, 375 00:26:19,440 --> 00:26:21,480 just by putting a bottle in the water. 376 00:26:21,480 --> 00:26:25,040 And the sound is very, very different. So if I... 377 00:26:25,040 --> 00:26:27,720 It's not very elegant. I've just got my thumb over the top 378 00:26:27,720 --> 00:26:30,880 and I'm going to put this down below and let bubbles of air come out. 379 00:26:30,880 --> 00:26:34,480 BUBBLES GURGLE 380 00:26:36,000 --> 00:26:39,040 And you're all familiar with that sound, 381 00:26:39,040 --> 00:26:42,680 but the interesting thing here is that the big bubbles 382 00:26:42,680 --> 00:26:45,400 make a deeper note and the smaller bubbles make a higher note. 383 00:26:45,400 --> 00:26:47,760 So they're like big and little bells. 384 00:26:47,760 --> 00:26:50,640 When you hear this "ping" noise of a new bubble being formed, 385 00:26:50,640 --> 00:26:52,320 it's telling you how big it is. 386 00:26:52,320 --> 00:26:54,440 And it's a very precise relationship. 387 00:26:58,720 --> 00:27:02,200 Bubbles make sounds for the same reasons many other things do - 388 00:27:02,200 --> 00:27:04,440 they vibrate or oscillate. 389 00:27:06,000 --> 00:27:08,080 GUITAR NOTE SOUNDS 390 00:27:09,200 --> 00:27:13,080 They do this because the air inside the bubble can be squashed 391 00:27:13,080 --> 00:27:15,560 and then the squashed air pushes back. 392 00:27:18,400 --> 00:27:22,760 But a few years ago, some colleagues and I wanted to solve a mystery. 393 00:27:22,760 --> 00:27:24,360 THUMB PIANO NOTE SOUNDS 394 00:27:24,360 --> 00:27:28,920 What starts bubbles oscillating in the first place? 395 00:27:28,920 --> 00:27:32,120 If you think of bubbles like bells, it's a bit like asking 396 00:27:32,120 --> 00:27:35,520 what is the hammer that hits the bell, what gets it started? 397 00:27:35,520 --> 00:27:37,640 So, in order to answer that question, 398 00:27:37,640 --> 00:27:39,720 I took this series of photographs 399 00:27:39,720 --> 00:27:43,800 and what you're looking at here is a tube of air 400 00:27:43,800 --> 00:27:46,800 where air is being blown upwards into water, 401 00:27:46,800 --> 00:27:50,520 and this is the moment that the bubble breaks away from the tube 402 00:27:50,520 --> 00:27:53,560 and escapes up into the rest of the water column. 403 00:27:53,560 --> 00:27:57,520 So you can see right here that just as the bubble starts to break, 404 00:27:57,520 --> 00:28:00,320 it generates this neck which narrows. 405 00:28:00,320 --> 00:28:03,600 And then, as we carry on in time, it gets narrower and narrower. 406 00:28:03,600 --> 00:28:06,320 This is the last moment that the bubble is attached 407 00:28:06,320 --> 00:28:09,280 to the rest of the gas before it breaks away. 408 00:28:09,280 --> 00:28:13,560 And in the next frame, a 10th of a millisecond later, 409 00:28:13,560 --> 00:28:15,320 it's over, the bubble is free. 410 00:28:15,320 --> 00:28:19,760 And what we found is that the sound all originates from this point. 411 00:28:19,760 --> 00:28:24,400 Bubbles hate sharp corners, and that bubble's got a corner. 412 00:28:24,400 --> 00:28:27,640 So all of that liquid rushes up inside the bubble 413 00:28:27,640 --> 00:28:29,280 to get rid of the corner, 414 00:28:29,280 --> 00:28:32,480 we get this little jet, that squeezes the air inside the bubble 415 00:28:32,480 --> 00:28:34,720 and that's what starts these oscillations. 416 00:28:34,720 --> 00:28:36,600 So we could actually physically see 417 00:28:36,600 --> 00:28:39,720 the hammer hitting the bell. 418 00:28:41,160 --> 00:28:42,680 PING 419 00:28:44,720 --> 00:28:47,520 WATER GUSHES 420 00:28:47,520 --> 00:28:50,880 It's astonishing to realise that all of these sounds 421 00:28:50,880 --> 00:28:53,760 are the sounds of bubbles being made. 422 00:28:53,760 --> 00:28:55,880 WINE GLUGS 423 00:29:01,040 --> 00:29:04,560 But how about animals that live in water? 424 00:29:04,560 --> 00:29:07,320 Then the relationship between bubbles and sound 425 00:29:07,320 --> 00:29:09,880 is incredibly important. 426 00:29:09,880 --> 00:29:13,240 Imagine you're a sea creature and you're not just living in an ocean, 427 00:29:13,240 --> 00:29:15,240 but you're living in a bubbly ocean. 428 00:29:15,240 --> 00:29:18,640 Now, most marine creatures get a lot of their information from sound. 429 00:29:18,640 --> 00:29:21,440 So they know about what's going on in the world around them 430 00:29:21,440 --> 00:29:23,080 because sound is coming to them. 431 00:29:23,080 --> 00:29:26,360 And bubbles are directly affecting that sound. They're absorbing it 432 00:29:26,360 --> 00:29:27,720 and they're scattering it. 433 00:29:27,720 --> 00:29:29,440 So, if you're a marine creature, 434 00:29:29,440 --> 00:29:33,400 the bubbles are directly affecting your perception of your world. 435 00:29:37,080 --> 00:29:39,280 Humpback whales hunt small fish 436 00:29:39,280 --> 00:29:42,720 by exploiting the acoustic properties of bubbles. 437 00:29:45,080 --> 00:29:47,640 The whales blow columns of bubbles 438 00:29:47,640 --> 00:29:51,840 and also send sound into those bubbles which is trapped by them. 439 00:29:51,840 --> 00:29:53,920 This terrifies the fish 440 00:29:53,920 --> 00:29:56,400 and make them easy prey for the whales. 441 00:30:03,200 --> 00:30:05,280 The way bubbles vibrate 442 00:30:05,280 --> 00:30:08,760 and interact with sounds can be exploited by humans too. 443 00:30:10,280 --> 00:30:12,120 Now, then, I have here... 444 00:30:12,120 --> 00:30:15,160 This is Professor Tim Leighton, my scientific mentor 445 00:30:15,160 --> 00:30:19,320 and probably the world's foremost expert on bubble acoustics - 446 00:30:19,320 --> 00:30:23,840 the relationship between bubbles and sound. 447 00:30:23,840 --> 00:30:28,240 And what he's about to show me is, well, it's almost like magic. 448 00:30:30,480 --> 00:30:32,920 Here we have a device that we've built. 449 00:30:32,920 --> 00:30:35,560 It's a black cone. You could fit it on the end of a tap 450 00:30:35,560 --> 00:30:38,480 or on top of a fire extinguisher or something. 451 00:30:38,480 --> 00:30:41,800 And just cold water is coming out of it. 452 00:30:41,800 --> 00:30:45,160 This is an experimental rig, which, thanks to bubbles, 453 00:30:45,160 --> 00:30:49,400 could one day completely change the way we clean things. 454 00:30:50,400 --> 00:30:54,280 Lipstick is notoriously difficult to remove 455 00:30:54,280 --> 00:30:57,360 because it's designed to be sticky. 456 00:30:57,360 --> 00:31:00,160 And if we take this normal kitchen tile 457 00:31:00,160 --> 00:31:05,040 and we were to, say, write - I'm not very good writing with lipstick - 458 00:31:05,040 --> 00:31:10,160 say, BBC on it... Like this. 459 00:31:12,560 --> 00:31:17,120 And then we hold this into the stream of cold water. 460 00:31:17,120 --> 00:31:19,440 As expected, it stays on. 461 00:31:19,440 --> 00:31:21,320 It's really good at sticking. 462 00:31:21,320 --> 00:31:24,480 Now, with the flick of a switch, the magic happens. 463 00:31:24,480 --> 00:31:26,840 And here we go. 464 00:31:26,840 --> 00:31:29,440 It's stunning. The difference is amazing. 465 00:31:29,440 --> 00:31:32,520 This incredibly effective way of cleaning 466 00:31:32,520 --> 00:31:36,880 relies entirely on bubbles and their relationship with sound. 467 00:31:36,880 --> 00:31:42,640 Water comes through this device and we add microscopic bubbles 468 00:31:42,640 --> 00:31:49,200 and we had ultrasound, using this silver sound source at the back. 469 00:31:49,200 --> 00:31:53,640 And when the bubbles hit the device to be cleaned, 470 00:31:53,640 --> 00:31:57,600 the ultrasound hits them and turns these bubbles 471 00:31:57,600 --> 00:31:59,920 from nice little balls of gas 472 00:31:59,920 --> 00:32:04,040 into quite excitable little scrubbing machines. 473 00:32:05,520 --> 00:32:08,520 This works because the bubbles are resonating, 474 00:32:08,520 --> 00:32:10,840 vibrating in response to ultrasound - 475 00:32:10,840 --> 00:32:15,360 the high-frequency sound waves that are travelling through the water. 476 00:32:17,800 --> 00:32:20,800 The wall is shimmering and moving very rapidly 477 00:32:20,800 --> 00:32:23,160 with thousands of tiny little ripples. 478 00:32:23,160 --> 00:32:26,840 And at the edge of those ripples, you have very high shear in the water. 479 00:32:26,840 --> 00:32:30,240 And so what that does is, it scrubs away at any surface. 480 00:32:30,240 --> 00:32:34,200 - Shear is like this sort of action, so it's scrubbing? - That's right. 481 00:32:34,200 --> 00:32:38,120 It really is scrubbing away at the surface, cleaning away, 482 00:32:38,120 --> 00:32:41,200 removing dirt and particles. 483 00:32:41,200 --> 00:32:44,640 So the bubble wall shimmers to clean, 484 00:32:44,640 --> 00:32:48,240 but specifically, using the bubbles in this way, they're targeted to 485 00:32:48,240 --> 00:32:52,440 seek and find crevices and cracks, and clean the dirt out of those. 486 00:32:53,800 --> 00:32:56,120 This is the second really clever bit. 487 00:32:56,120 --> 00:32:59,400 The vibrating bubbles send out sound. 488 00:32:59,400 --> 00:33:03,600 This echoes off nearby surfaces, and the reflected waves pull 489 00:33:03,600 --> 00:33:09,240 the bubbles closer to those surfaces and into any tiny cracks that exist. 490 00:33:09,240 --> 00:33:11,720 Those crevices are exactly the places 491 00:33:11,720 --> 00:33:14,000 that are usually hardest to clean. 492 00:33:16,440 --> 00:33:20,200 So it's really strongly attracted into that crevice 493 00:33:20,200 --> 00:33:22,600 and it burrows into it, keeps burrowing, 494 00:33:22,600 --> 00:33:27,120 digging out the dirt as it goes because its surface is shimmering. 495 00:33:27,120 --> 00:33:30,880 And what sort of applications has this got out in the real world? 496 00:33:30,880 --> 00:33:32,720 We're looking first of all 497 00:33:32,720 --> 00:33:36,280 at manufacturers with production lines with big plants. 498 00:33:36,280 --> 00:33:38,800 Right at the other end of the scale, we would like to see 499 00:33:38,800 --> 00:33:40,920 one of these in every home and every hospital 500 00:33:40,920 --> 00:33:44,080 so that hands, scalpels, endoscopes 501 00:33:44,080 --> 00:33:49,440 and anything else that you want to clean is safely cleaned 502 00:33:49,440 --> 00:33:52,080 and, not only that, but cleaned using cold water 503 00:33:52,080 --> 00:33:53,680 with very little additives, 504 00:33:53,680 --> 00:33:57,320 so that you're not wasting water and so that you don't incur 505 00:33:57,320 --> 00:33:59,720 the energy bills and the clean-up bill 506 00:33:59,720 --> 00:34:01,640 to make that water drinkable after. 507 00:34:01,640 --> 00:34:04,200 And all that is possible because of tiny bubbles 508 00:34:04,200 --> 00:34:06,720 - that we can't even see? - Exactly. 509 00:34:09,240 --> 00:34:12,160 So, we're going to give you the microbubbles now. 510 00:34:13,280 --> 00:34:16,240 Three, two, one, inject. 511 00:34:17,520 --> 00:34:21,120 This is Charing Cross Hospital, and here they're using 512 00:34:21,120 --> 00:34:25,760 the way that bubbles respond to sound very differently... 513 00:34:25,760 --> 00:34:28,880 To see inside a person. 514 00:34:28,880 --> 00:34:31,880 They're injecting microscopic bubbles 515 00:34:31,880 --> 00:34:34,400 into the patient's bloodstream. 516 00:34:36,280 --> 00:34:40,680 These bubbles dramatically improve the quality of ultrasound scans, 517 00:34:40,680 --> 00:34:45,120 giving doctors a much better chance of making an accurate diagnosis. 518 00:34:46,600 --> 00:34:50,400 Breathe in, sir. Hold your breath there very still. 519 00:34:50,400 --> 00:34:52,040 Perfect. There you go. 520 00:34:52,040 --> 00:34:55,640 Can you see how it's enhancing all around that lesion now? 521 00:34:55,640 --> 00:34:58,880 There is the contrast in here, you see? 522 00:34:58,880 --> 00:35:03,080 All done. Didn't feel too much at all, hopefully? Good. Perfect. 523 00:35:03,080 --> 00:35:07,120 Normally, ultrasound works by sending high-frequency sound 524 00:35:07,120 --> 00:35:10,800 into the body and listening to the echoes that come back. 525 00:35:12,280 --> 00:35:16,280 The problem is, there isn't much contrast between 526 00:35:16,280 --> 00:35:18,880 different tissues of the body. 527 00:35:18,880 --> 00:35:20,840 But, if bubbles are present, 528 00:35:20,840 --> 00:35:24,480 the ultrasound makes them vibrate and scatter sound. 529 00:35:24,480 --> 00:35:28,000 This makes the echo that comes back much stronger. 530 00:35:30,960 --> 00:35:34,880 At Oxford University, my friend and fellow bubble scientist, 531 00:35:34,880 --> 00:35:37,440 Dr Eleanor Stride, explains. 532 00:35:37,440 --> 00:35:40,080 So we put these very, very tiny bubbles into the bloodstream 533 00:35:40,080 --> 00:35:42,720 and suddenly you're able to see where the blood is flowing. 534 00:35:42,720 --> 00:35:45,440 If I show you an image of that in action... 535 00:35:45,440 --> 00:35:47,520 This is a scan of the liver. 536 00:35:47,520 --> 00:35:49,920 This is before the contrast agent has got to the liver. 537 00:35:49,920 --> 00:35:53,000 And what you'll see when I start the video is, the contrast agent 538 00:35:53,000 --> 00:35:56,160 - starts to wash into the blood vessels. - So the bubbles are coming... 539 00:35:56,160 --> 00:35:58,960 You can see all these little tendrils. Those are blood vessels? 540 00:35:58,960 --> 00:36:01,880 Those are blood vessels, exactly. So, because bubbles are in there, 541 00:36:01,880 --> 00:36:03,960 they're reflecting the sound really strongly. 542 00:36:03,960 --> 00:36:06,800 You see the major blood vessel here and smaller ones branching off. 543 00:36:06,800 --> 00:36:10,280 - We can see there's a lot of blood in this area here. - Nice and clearly. 544 00:36:10,280 --> 00:36:13,000 And you can't see those under normal ultrasound imaging. 545 00:36:13,000 --> 00:36:14,640 And this is what bubbles provide. 546 00:36:14,640 --> 00:36:17,560 - So you can see abnormal tissue, basically? - Precisely. 547 00:36:22,400 --> 00:36:25,240 Bubbles resonate like musical instruments. 548 00:36:25,240 --> 00:36:29,600 That's the secret behind many of the things we're now using them for. 549 00:36:29,600 --> 00:36:32,960 But there is another aspect of bubble science 550 00:36:32,960 --> 00:36:37,080 with perhaps the most surprising consequences of all. 551 00:36:40,960 --> 00:36:44,400 It's to do with the way bubbles move through the liquid 552 00:36:44,400 --> 00:36:47,480 and carry things to the air and back. 553 00:36:49,360 --> 00:36:51,600 This affects many aspects of nature 554 00:36:51,600 --> 00:36:54,880 and we'll see how it's vital to our oceans and atmosphere. 555 00:36:56,720 --> 00:36:58,280 And to see how that works, 556 00:36:58,280 --> 00:37:01,880 I want to show you how bubbles do what they're most famous for... 557 00:37:04,080 --> 00:37:07,400 Perform their magic in champagne. 558 00:37:16,280 --> 00:37:18,560 I've got quite mixed feelings about today 559 00:37:18,560 --> 00:37:22,640 because on one hand, this is the bubble physicist's dream day out 560 00:37:22,640 --> 00:37:25,600 and it's something I've always wanted to do. 561 00:37:25,600 --> 00:37:28,640 And on the other hand, I'm never going to live this down 562 00:37:28,640 --> 00:37:32,040 because this is the Champagne region of France, and I'm here 563 00:37:32,040 --> 00:37:35,640 to spend the day in a laboratory where they study champagne. 564 00:37:35,640 --> 00:37:37,520 But - would-be teasers take note - 565 00:37:37,520 --> 00:37:39,680 there is a scientific reason for this, 566 00:37:39,680 --> 00:37:43,440 because bubbles are crucial to how we taste and perceive champagne. 567 00:37:44,800 --> 00:37:46,440 Before going to the lab, 568 00:37:46,440 --> 00:37:50,760 I start my investigation into how bubbles work in champagne 569 00:37:50,760 --> 00:37:53,360 in one of the classiest restaurants in Reims, 570 00:37:53,360 --> 00:37:55,680 the capital of the Champagne region. 571 00:37:58,760 --> 00:38:01,080 We're starting on a big one. 572 00:38:01,080 --> 00:38:03,680 I'm here with sommelier Philippe Jamesse 573 00:38:03,680 --> 00:38:09,160 and physicist Gerard Liger-Belair, who studies champagne bubbles. 574 00:38:11,400 --> 00:38:15,000 To show me how important bubble movement is in champagne, 575 00:38:15,000 --> 00:38:16,680 they subjected me to a test. 576 00:38:18,800 --> 00:38:20,640 They've poured the same champagne 577 00:38:20,640 --> 00:38:24,600 into three differently shaped glasses. 578 00:38:24,600 --> 00:38:27,600 Apparently, the bubbles will move differently 579 00:38:27,600 --> 00:38:30,080 in the different glasses, 580 00:38:30,080 --> 00:38:34,520 and that in turn will change the way the champagne smells and tastes. 581 00:38:35,840 --> 00:38:38,480 But I was doubtful I'd notice 582 00:38:38,480 --> 00:38:42,120 because when it comes to champagne, I'm a complete novice. 583 00:38:45,600 --> 00:38:48,400 It is actually really different. 584 00:38:51,600 --> 00:38:55,320 And that one's much... It's like it gets a lot calmer. 585 00:38:58,440 --> 00:39:02,680 In a tall, thin glass, the bubbles reaching the surface are bigger 586 00:39:02,680 --> 00:39:06,200 and are moving faster than in a wide glass. 587 00:39:09,560 --> 00:39:12,960 That makes the drink smell and taste very different. 588 00:39:16,320 --> 00:39:19,080 To find out why, I went with Gerard 589 00:39:19,080 --> 00:39:22,360 to his lab at the University of Reims. 590 00:39:24,840 --> 00:39:28,200 A lab dedicated to the study of champagne bubbles. 591 00:39:30,840 --> 00:39:35,040 About 15 years ago, I got interested in bubbles, 592 00:39:35,040 --> 00:39:39,560 especially by drinking - not champagne, I was too young - 593 00:39:39,560 --> 00:39:41,880 but I was drinking beer. 594 00:39:41,880 --> 00:39:46,160 And I focused on the tiny bubble trains on the beer wall 595 00:39:46,160 --> 00:39:48,880 - on the glass wall - and I imagined 596 00:39:48,880 --> 00:39:52,360 that it could make a fantastic PhD project. 597 00:39:52,360 --> 00:39:55,600 So from the food mechanics point of view... 598 00:39:55,600 --> 00:39:58,640 - In vino veritas! - You're right. In vino veritas, yes. 599 00:39:58,640 --> 00:40:00,040 I knew that obviously, bubbles 600 00:40:00,040 --> 00:40:02,280 are very important in the champagne industry, 601 00:40:02,280 --> 00:40:08,000 so maybe I could mix my passion with bubbles with the champagne industry 602 00:40:08,000 --> 00:40:11,000 if they want to know more information 603 00:40:11,000 --> 00:40:13,400 about their bubbling process. 604 00:40:15,840 --> 00:40:18,760 Champagne bubbles are full of carbon dioxide, 605 00:40:18,760 --> 00:40:21,720 a gas made while the drink was being fermented. 606 00:40:24,360 --> 00:40:28,640 When the bottle is sealed, the gas stays dissolved inside the liquid. 607 00:40:32,360 --> 00:40:35,200 When the cork comes off, the gas escapes as bubbles. 608 00:40:36,240 --> 00:40:40,680 The glass they're in has a big influence on their journey. 609 00:40:42,400 --> 00:40:44,680 Gerard wanted to know 610 00:40:44,680 --> 00:40:47,360 how that process starts, how the bubble forms. 611 00:40:47,360 --> 00:40:49,200 What's this showing us? 612 00:40:49,200 --> 00:40:53,040 Yeah, this is champagne and we have fitted 613 00:40:53,040 --> 00:40:56,280 microscope objective on a high-speed video camera 614 00:40:56,280 --> 00:40:58,880 to see where the bubbles are coming from. 615 00:40:58,880 --> 00:41:01,400 - And so where are they forming? - They form everywhere 616 00:41:01,400 --> 00:41:04,840 where a tiny particle or imperfection is. 617 00:41:04,840 --> 00:41:08,200 So we are going to see this on the screen. 618 00:41:08,200 --> 00:41:12,400 You can clearly see that the bubbles are not coming from nowhere, 619 00:41:12,400 --> 00:41:15,760 they're coming from a tiny particle stuck on the wall, 620 00:41:15,760 --> 00:41:18,760 and this is indeed a tiny dust particle. 621 00:41:18,760 --> 00:41:22,960 - So they're actually coming from specks of dirt? - Yes, you're right. 622 00:41:22,960 --> 00:41:25,160 Gerard had shown that bubbles are born 623 00:41:25,160 --> 00:41:29,640 whenever there are imperfections on the glass's surface. 624 00:41:29,640 --> 00:41:32,120 And this has surprising consequences. 625 00:41:33,840 --> 00:41:37,440 This says to me that you can artificially make places, 626 00:41:37,440 --> 00:41:41,240 you could choose that your champagne glass would make more bubbles. 627 00:41:41,240 --> 00:41:45,000 When you see such a column on the centre of the glass, 628 00:41:45,000 --> 00:41:46,880 it is because the glass has been etched. 629 00:41:46,880 --> 00:41:50,040 So they've scratched away at the bottom to make these rough surfaces? 630 00:41:50,040 --> 00:41:51,720 Yes, to promote effervescence. 631 00:41:51,720 --> 00:41:54,120 By putting dye into the champagne, 632 00:41:54,120 --> 00:41:58,840 you can clearly see the effect of scratching the bottom of the glass. 633 00:42:00,240 --> 00:42:03,280 It forces the bubbles to travel in a narrow column 634 00:42:03,280 --> 00:42:04,960 up the centre of the glass. 635 00:42:06,280 --> 00:42:09,560 And we'll see that this is really important. 636 00:42:09,560 --> 00:42:12,040 The lovely thing that I think is really clear here 637 00:42:12,040 --> 00:42:14,400 is that you can see the bubbles are starting really tiny 638 00:42:14,400 --> 00:42:17,000 and they're being released and they're growing as they go up 639 00:42:17,000 --> 00:42:19,400 and as they get more and more buoyant, they get bigger, 640 00:42:19,400 --> 00:42:20,640 they go faster and faster. 641 00:42:20,640 --> 00:42:23,080 Yes, because the CO2 continues to accumulate 642 00:42:23,080 --> 00:42:26,520 inside the rising bubbles, so it grows inside and accelerates. 643 00:42:28,560 --> 00:42:31,880 So, in a tall glass, the bubbles travel further 644 00:42:31,880 --> 00:42:37,080 and they get bigger and are moving much further than in a short glass. 645 00:42:37,080 --> 00:42:41,640 This has the effect of mixing the drink more vigorously, 646 00:42:41,640 --> 00:42:45,280 which in part explains the more intense flavour 647 00:42:45,280 --> 00:42:48,520 I'd noticed in the tall, thin glass. 648 00:42:48,520 --> 00:42:51,400 But that's only half the story. 649 00:42:51,400 --> 00:42:54,360 With his high speed camera, 650 00:42:54,360 --> 00:42:58,680 Gerard found that the bubbles do another crucial job in champagne. 651 00:42:58,680 --> 00:43:02,920 So here we have a high-speed photograph of the champagne jet 652 00:43:02,920 --> 00:43:05,160 which is injected by the bubble, 653 00:43:05,160 --> 00:43:08,280 and we also have a high-speed film of the process. 654 00:43:08,280 --> 00:43:10,920 So this is just as the bubble is just at the surface 655 00:43:10,920 --> 00:43:14,040 and it sits there for a little while, and then the top of it breaks 656 00:43:14,040 --> 00:43:16,080 and this is what happens next? 657 00:43:16,080 --> 00:43:20,240 Then the bubble cavity collapses and when it collapses, it can eject 658 00:43:20,240 --> 00:43:25,440 a tiny champagne jet up to several centimetres above the surface. 659 00:43:27,080 --> 00:43:30,080 Gerard now went one step further. 660 00:43:30,080 --> 00:43:33,560 He analysed the droplets being spat out by the bubbles. 661 00:43:35,040 --> 00:43:39,160 The molecules that carry the distinctive aromas of champagne 662 00:43:39,160 --> 00:43:42,080 were really concentrated in the droplets. 663 00:43:46,800 --> 00:43:48,960 They'd been carried by the bubble, 664 00:43:48,960 --> 00:43:52,360 somehow sticking to the bubble surface. 665 00:43:52,360 --> 00:43:54,480 Bubbles carry, obviously, CO2, 666 00:43:54,480 --> 00:43:58,360 but also aromatic molecules stuck on the bubble wall 667 00:43:58,360 --> 00:44:00,680 and when the bubble collapses, 668 00:44:00,680 --> 00:44:05,400 it ejects all those molecules above the surface. 669 00:44:05,400 --> 00:44:08,440 So this moment here right where we see the hole in the water, 670 00:44:08,440 --> 00:44:11,720 that hole is coated with these molecules, and then when 671 00:44:11,720 --> 00:44:15,480 it squirts it upwards, those molecules are going up into the air. 672 00:44:15,480 --> 00:44:19,200 - Yes. - That's beautiful. I love all this photography, it's fantastic. 673 00:44:19,200 --> 00:44:21,000 I could watch this all day. 674 00:44:21,000 --> 00:44:23,440 It's a very efficient way to transfer 675 00:44:23,440 --> 00:44:25,840 the champagne into the vapour phase 676 00:44:25,840 --> 00:44:28,320 so that you can feel it with your nose. 677 00:44:30,280 --> 00:44:32,640 What Gerard had found in the champagne 678 00:44:32,640 --> 00:44:35,600 is a property of bubbles that's really important. 679 00:44:36,680 --> 00:44:39,720 As we'll see, it's crucial to our oceans and atmosphere. 680 00:44:40,760 --> 00:44:43,880 Bubbles have the ability to transport substances 681 00:44:43,880 --> 00:44:47,040 from within a liquid to its surface and beyond. 682 00:44:49,280 --> 00:44:53,240 But why? What's going on, on their surface, 683 00:44:53,240 --> 00:44:55,920 this mysterious place where gas and liquid touch, 684 00:44:55,920 --> 00:44:58,560 that means certain molecules stick to it? 685 00:45:01,600 --> 00:45:05,200 It's hard to show because these molecules are invisible, 686 00:45:05,200 --> 00:45:08,400 so I've come up with another example. 687 00:45:08,400 --> 00:45:10,760 And so what I've got down here is an experiment 688 00:45:10,760 --> 00:45:12,760 to show how bubbles can carry glitter. 689 00:45:12,760 --> 00:45:15,720 And glitter is like those aroma molecules here 690 00:45:15,720 --> 00:45:18,520 because it doesn't want to be underwater. 691 00:45:18,520 --> 00:45:21,880 If it can find a place where it's touching both the water and the air, 692 00:45:21,880 --> 00:45:23,080 it will stick there. 693 00:45:24,440 --> 00:45:27,640 Parts of these molecules are repelled by water. 694 00:45:27,640 --> 00:45:30,760 So they rush to the one place where there's no water, 695 00:45:30,760 --> 00:45:33,040 the surface of the bubble. 696 00:45:33,040 --> 00:45:34,720 So, the way that this works is, 697 00:45:34,720 --> 00:45:37,640 I'm just going to take lots and lots of photographs, 698 00:45:37,640 --> 00:45:39,680 and hopefully one or two of them at least 699 00:45:39,680 --> 00:45:42,440 will show the glitter sticking to the bubbles 700 00:45:42,440 --> 00:45:44,680 and being carried up to the surface. 701 00:45:44,680 --> 00:45:46,400 Let me set this going. 702 00:45:46,400 --> 00:45:48,280 So, I'm going to push down on the plunger, 703 00:45:48,280 --> 00:45:50,280 which is going to send air down here 704 00:45:50,280 --> 00:45:53,040 and out through the funnel where the bubbles are. 705 00:45:58,280 --> 00:45:59,760 So now I can look at the photos 706 00:45:59,760 --> 00:46:02,920 and see if I can see the bubbles carrying the glitter upwards. 707 00:46:02,920 --> 00:46:07,000 OK, so here's one. This is really, really nice. 708 00:46:07,000 --> 00:46:09,800 There's a big whoosh of bubbles have all come out together, 709 00:46:09,800 --> 00:46:10,920 a cluster of them, 710 00:46:10,920 --> 00:46:13,480 and you can clearly see that the glitter has just stuck 711 00:46:13,480 --> 00:46:16,040 to the surface of the bubbles, and there's actually 712 00:46:16,040 --> 00:46:19,040 a little cloud of glitter at the bottom where bits have fallen off 713 00:46:19,040 --> 00:46:22,000 and so they're leaving a trail of glitter behind them as well. 714 00:46:22,000 --> 00:46:23,640 So it's really obvious here 715 00:46:23,640 --> 00:46:26,560 that the bubbles are carrying glitter upwards. 716 00:46:29,520 --> 00:46:31,400 The fact that certain molecules 717 00:46:31,400 --> 00:46:34,120 can stick to bubbles is incredibly important 718 00:46:34,120 --> 00:46:39,520 and has inspired some very exciting medical research. 719 00:46:39,520 --> 00:46:40,800 What we're doing is, 720 00:46:40,800 --> 00:46:44,680 we're pumping liquid through one channel, gas through another channel, 721 00:46:44,680 --> 00:46:47,400 and where they meet we're getting a bubble. 722 00:46:47,400 --> 00:46:52,320 Scientists hope that bubbles will become magic bullets. 723 00:46:52,320 --> 00:46:55,840 It's all about the bubble surface. 724 00:46:55,840 --> 00:46:58,760 The basic idea is that instead of glitter, 725 00:46:58,760 --> 00:47:01,520 scientists will stick drugs there. 726 00:47:01,520 --> 00:47:04,680 We're actually attaching a cancer chemotherapy drug 727 00:47:04,680 --> 00:47:06,560 right onto the bubble surface. 728 00:47:06,560 --> 00:47:08,880 So, if you have a drug that's got the right properties, 729 00:47:08,880 --> 00:47:11,080 - it will stick to the surface of the bubble? - Exactly. 730 00:47:11,080 --> 00:47:13,000 It'll stick right onto the bubble surface, 731 00:47:13,000 --> 00:47:15,200 and it won't come off until we want it to come off. 732 00:47:15,200 --> 00:47:17,400 - How small are these bubbles? - Really, really tiny. 733 00:47:17,400 --> 00:47:20,280 Their equivalent size is a red blood cell, 734 00:47:20,280 --> 00:47:23,240 so that they can go through the capillaries within the body 735 00:47:23,240 --> 00:47:26,760 just that much easier. So they won't get filtered out by the lungs, 736 00:47:26,760 --> 00:47:29,600 they can go where they need to go, and we can use them 737 00:47:29,600 --> 00:47:32,320 for both diagnostic and therapeutic applications. 738 00:47:34,040 --> 00:47:37,240 But there's a second really important benefit 739 00:47:37,240 --> 00:47:39,440 to using bubbles to carry drugs. 740 00:47:39,440 --> 00:47:42,520 They can target specific places in the body. 741 00:47:43,720 --> 00:47:47,760 That means the drugs they carry don't affect the rest of the body 742 00:47:47,760 --> 00:47:50,640 and this helps avoid damaging side-effects. 743 00:47:55,400 --> 00:47:59,680 One really clever way of doing this is for the bubbles also to carry 744 00:47:59,680 --> 00:48:03,640 tiny particles of iron, so they can be directed by magnets. 745 00:48:05,880 --> 00:48:09,120 So this is a bit like a very sophisticated version of that thing 746 00:48:09,120 --> 00:48:10,880 where you get iron filings and a magnet, 747 00:48:10,880 --> 00:48:12,400 and as you pull the magnet around, 748 00:48:12,400 --> 00:48:15,680 - you can pull the iron filings around? - Yes, exactly like that, 749 00:48:15,680 --> 00:48:19,840 except this time we just see bubbles moving, as opposed to iron filings. 750 00:48:19,840 --> 00:48:22,920 So you can see at the top, there's a brown layer. 751 00:48:22,920 --> 00:48:26,160 So it's brownish because it's like rust. Rusty bubbles here. 752 00:48:26,160 --> 00:48:28,480 Rusty bubbles, but they're not bad for you in any way. 753 00:48:28,480 --> 00:48:31,000 And if you bring a magnet nearby, 754 00:48:31,000 --> 00:48:33,880 you can actually see the cloud move down, 755 00:48:33,880 --> 00:48:36,880 - and when you move it away, it turns. - They're well-behaved! 756 00:48:36,880 --> 00:48:38,480 Look at that! 757 00:48:41,480 --> 00:48:45,400 That's lovely. So, yeah, you can really push and pull them around. 758 00:48:45,400 --> 00:48:47,560 Yeah. Wherever the magnetic field is strongest, 759 00:48:47,560 --> 00:48:49,360 that's exactly where they'll head for. 760 00:48:49,360 --> 00:48:51,960 Once you've put your magnets on the person, 761 00:48:51,960 --> 00:48:54,800 how do you know whether the bubbles have stopped in the right place? 762 00:48:54,800 --> 00:48:58,240 We can see the bubbles completely under ultrasound in real time. 763 00:48:58,240 --> 00:49:00,280 That's one of the amazing things with these. 764 00:49:00,280 --> 00:49:04,160 With other drug delivery vehicles, you have no idea where they are, you hope for the best. 765 00:49:04,160 --> 00:49:07,280 With this, you actually see them stop. You can see where they are 766 00:49:07,280 --> 00:49:10,920 and then you can actually, when you remove the magnetic field, see them go away. 767 00:49:10,920 --> 00:49:14,160 - So, have you got pictures of that? That sounds fantastic. - Yes. 768 00:49:14,160 --> 00:49:18,240 So on this screen here, we have a video I recorded earlier on. 769 00:49:18,240 --> 00:49:20,240 So this is the tube, the outer wall. 770 00:49:20,240 --> 00:49:22,720 And you can see the inside completely empty 771 00:49:22,720 --> 00:49:24,440 because there's no bubbles. 772 00:49:24,440 --> 00:49:26,960 So this is like a blood vessel, a capillary vessel, 773 00:49:26,960 --> 00:49:30,240 somewhere in the body, and the cells over here and blood is running? 774 00:49:30,240 --> 00:49:32,120 Exactly, yes. 775 00:49:32,120 --> 00:49:34,040 And below here we have a magnet, 776 00:49:34,040 --> 00:49:37,840 so it's sitting a bit of a distance away, a few millimetres. 777 00:49:37,840 --> 00:49:42,720 So when I press play, we'll actually see the bubbles then flow in. 778 00:49:42,720 --> 00:49:45,920 So things are flowing through the pipe, but we can't see anything. 779 00:49:45,920 --> 00:49:47,640 And here are the bubbles. 780 00:49:47,640 --> 00:49:50,760 So you can actually see they're being drawn down towards the magnet 781 00:49:50,760 --> 00:49:53,920 and then on the bottom you see an increase in bubble concentration. 782 00:49:53,920 --> 00:49:55,000 So, here's the magnet 783 00:49:55,000 --> 00:49:57,640 - and here are all the bubbles that are attracted to it. - Yes. 784 00:49:57,640 --> 00:49:59,600 And that would be where your tumour was 785 00:49:59,600 --> 00:50:02,680 - or wherever it was that you wanted to treat? - Exactly, yeah. 786 00:50:03,960 --> 00:50:05,880 If this research works out, 787 00:50:05,880 --> 00:50:10,640 one day bubbles will carry drugs to exactly where they're needed. 788 00:50:10,640 --> 00:50:12,080 Once there, the final step 789 00:50:12,080 --> 00:50:15,240 is to persuade them to release their payload of medicine. 790 00:50:17,080 --> 00:50:21,920 And, to do that, we exploit the way bubbles respond to sound. 791 00:50:21,920 --> 00:50:24,080 When we want to use them for drug delivery, though, 792 00:50:24,080 --> 00:50:25,720 we just turn the ultrasound energy up, 793 00:50:25,720 --> 00:50:29,640 they oscillate more violently and the drug is released. 794 00:50:29,640 --> 00:50:31,600 So, that's lovely. 795 00:50:31,600 --> 00:50:34,680 You keep them calm and when it's time, you thump them with sound. 796 00:50:34,680 --> 00:50:38,040 - Oh, that was a big clap... - Well, that's actually exactly what happens. 797 00:50:38,040 --> 00:50:41,400 The bubbles expand to a large extent and then they collapse. 798 00:50:41,400 --> 00:50:44,200 It's the collapse that releases the drug and destroys the bubble. 799 00:50:44,200 --> 00:50:47,840 - Have you got video of this collapse process? - We do indeed. 800 00:50:47,840 --> 00:50:52,400 So, these are images taken at a few million frames per second. 801 00:50:52,400 --> 00:50:55,400 Sound comes in, you see the bubble expand, contract 802 00:50:55,400 --> 00:50:59,160 - and then break open and release its contents. - That's great! 803 00:50:59,160 --> 00:51:01,600 So just like you might have been injected in the arm 804 00:51:01,600 --> 00:51:02,960 with a vaccine or something, 805 00:51:02,960 --> 00:51:05,280 - this is injecting the drug into the body. - Exactly. 806 00:51:05,280 --> 00:51:07,400 Bubbles have been described as micro-syringes, 807 00:51:07,400 --> 00:51:09,400 as one of the interesting things about this jet 808 00:51:09,400 --> 00:51:12,360 is that this jet is being emitted very, very fast - 809 00:51:12,360 --> 00:51:15,080 sufficiently fast to actually puncture a cell membrane. 810 00:51:15,080 --> 00:51:19,280 - So the cell doesn't have a choice about this! - No! Provided the jet's in the right direction. 811 00:51:19,280 --> 00:51:22,280 The bubbles provide a fantastic way of encapsulating a drug, 812 00:51:22,280 --> 00:51:25,040 so the drug will have no action on the body until it's released. 813 00:51:25,040 --> 00:51:28,240 - The bubbles keep it insulated. - It's packaged. - It's packaged, exactly. 814 00:51:28,240 --> 00:51:31,280 And, more importantly, it's packaged in something we can track 815 00:51:31,280 --> 00:51:32,560 because we can track 816 00:51:32,560 --> 00:51:35,680 where the bubbles are flowing under ultrasound. 817 00:51:35,680 --> 00:51:39,440 It's great to see the direct practical benefits of bubbles. 818 00:51:41,960 --> 00:51:45,520 But now it's time to bring together all the things they can do 819 00:51:45,520 --> 00:51:49,800 and see how the tiny bubble matters to our whole planet. 820 00:52:12,200 --> 00:52:16,240 Most of the Earth's bubbles are here in the oceans. 821 00:52:16,240 --> 00:52:19,800 They're formed as breaking waves drag air underwater. 822 00:52:22,160 --> 00:52:24,920 These are the bubbles I study. 823 00:52:24,920 --> 00:52:26,640 And the reason I study them 824 00:52:26,640 --> 00:52:31,280 is that bubbles influence the way the oceans and atmosphere interact. 825 00:52:32,520 --> 00:52:36,360 And they do so in ways we're only just beginning to understand. 826 00:52:38,200 --> 00:52:40,800 I observe bubbles at sea 827 00:52:40,800 --> 00:52:45,120 and I also study them in great detail in my lab. 828 00:52:45,120 --> 00:52:48,440 Here, I can replicate the great variety of conditions 829 00:52:48,440 --> 00:52:50,840 that exist in our oceans. 830 00:52:50,840 --> 00:52:54,120 So what I can do with this tank is basically make it 831 00:52:54,120 --> 00:52:57,040 into any region of the ocean that I want. So it might be 832 00:52:57,040 --> 00:53:00,080 somewhere in the tropics with a high water temperature 833 00:53:00,080 --> 00:53:01,640 and lots of phytoplankton, 834 00:53:01,640 --> 00:53:04,040 it might be somewhere in the Southern Ocean 835 00:53:04,040 --> 00:53:05,680 where the water's very cold, 836 00:53:05,680 --> 00:53:08,400 not so much growing. And I can watch how the bubbles form 837 00:53:08,400 --> 00:53:10,800 in all those different situations in the ocean. 838 00:53:10,800 --> 00:53:14,640 And what's happening is that down at the bottom, there is a nozzle 839 00:53:14,640 --> 00:53:18,120 and it's bubbling away, so it's producing lots of bubbles 840 00:53:18,120 --> 00:53:22,760 and those bubbles rise into a region where there's two tubes 841 00:53:22,760 --> 00:53:26,080 coming down on either side and they're pumping water out. 842 00:53:26,080 --> 00:53:28,600 And so those bubbles rise up in a straight line 843 00:53:28,600 --> 00:53:30,640 and then they hit this region of turbulence 844 00:53:30,640 --> 00:53:34,560 and that's just like what happens to bubbles underneath a breaking wave. 845 00:53:34,560 --> 00:53:37,680 The reason for trying to understand bubbles is that 846 00:53:37,680 --> 00:53:41,840 out in the ocean, they play an important role in our climate. 847 00:53:41,840 --> 00:53:45,240 One part of that role especially is brilliant, 848 00:53:45,240 --> 00:53:47,480 because it's so surprising. 849 00:53:47,480 --> 00:53:51,080 When they rise to the top, and they form that foam, 850 00:53:51,080 --> 00:53:53,640 the white horses on the ocean surface, 851 00:53:53,640 --> 00:53:56,480 they are spitting tiny particles up into the atmosphere, 852 00:53:56,480 --> 00:53:59,200 and those particles can be bits of salt 853 00:53:59,200 --> 00:54:02,600 or they can be organic material that was stuck to the bubble, 854 00:54:02,600 --> 00:54:05,480 and they all get spat up into the atmosphere. 855 00:54:05,480 --> 00:54:06,720 And that matters - 856 00:54:06,720 --> 00:54:10,480 and this is one of my favourite facts in bubble science - 857 00:54:10,480 --> 00:54:14,800 those tiny particles that get spat upwards help clouds form. 858 00:54:14,800 --> 00:54:18,320 So, in a cloud in the atmosphere, all the droplets 859 00:54:18,320 --> 00:54:21,840 have at their centre a little speck of dust of some sort, 860 00:54:21,840 --> 00:54:27,240 and especially over the open ocean, clouds quite often at their centre 861 00:54:27,240 --> 00:54:30,680 have a little speck of dust that was spat out of the ocean by a bubble. 862 00:54:36,880 --> 00:54:39,880 And ocean bubbles aren't just a one-way street. 863 00:54:41,800 --> 00:54:45,120 They also help carry gases like carbon dioxide and oxygen 864 00:54:45,120 --> 00:54:47,080 down into the water. 865 00:54:49,480 --> 00:54:51,120 And so these transport mechanisms 866 00:54:51,120 --> 00:54:53,400 - the fact that the bubbles help gases move around 867 00:54:53,400 --> 00:54:54,960 and help particles move around - 868 00:54:54,960 --> 00:54:57,080 is really important for weather and climate 869 00:54:57,080 --> 00:54:59,320 because it's basically changing the chemistry 870 00:54:59,320 --> 00:55:01,120 of both the atmosphere and the ocean. 871 00:55:04,280 --> 00:55:07,480 So you can see why knowing how many bubbles there are 872 00:55:07,480 --> 00:55:10,480 and how big they are would help our climate models. 873 00:55:12,200 --> 00:55:15,520 And this is the equipment I'm using to do this. 874 00:55:15,520 --> 00:55:19,000 It records bubbles responding to sound. 875 00:55:19,000 --> 00:55:22,920 In principle, by analysing these recordings, 876 00:55:22,920 --> 00:55:24,880 I can calculate how many bubbles there are 877 00:55:24,880 --> 00:55:26,520 in a particular part of the ocean, 878 00:55:26,520 --> 00:55:30,520 and equally important, I can estimate how big they are. 879 00:55:30,520 --> 00:55:33,840 The idea behind how this works is quite simple. 880 00:55:36,040 --> 00:55:37,480 And so you can see now very clearly 881 00:55:37,480 --> 00:55:40,920 that there's this long period oscillation that's the bigger bubble 882 00:55:40,920 --> 00:55:44,720 and this has a frequency of 1.7 kilohertz. It tells me 883 00:55:44,720 --> 00:55:49,400 that the bigger bubble here was about two millimetres in radius. 884 00:55:49,400 --> 00:55:53,080 And the frequency of the other one is 16.5 kilohertz. 885 00:55:53,080 --> 00:55:57,280 That tells me that this bubble here was about a tenth of the radius, 886 00:55:57,280 --> 00:56:00,560 so this one is about 0.2 millimetres in radius. 887 00:56:00,560 --> 00:56:02,440 And you get all that information 888 00:56:02,440 --> 00:56:04,800 just from looking at that sound signal. 889 00:56:04,800 --> 00:56:07,320 And this is why sound is such a powerful technique 890 00:56:07,320 --> 00:56:09,920 to use in the ocean, because all you have to do is listen 891 00:56:09,920 --> 00:56:12,040 and you get this huge amount of information 892 00:56:12,040 --> 00:56:13,360 about what just happened. 893 00:56:19,000 --> 00:56:22,280 It's early days. There's much more work to do 894 00:56:22,280 --> 00:56:27,120 to compare the laboratory results with our measurements at sea. 895 00:56:30,560 --> 00:56:33,040 But one day I hope to be able to estimate 896 00:56:33,040 --> 00:56:36,320 not just how many bubbles form and how big they are, 897 00:56:36,320 --> 00:56:40,400 but exactly when and how they matter most. 898 00:56:40,400 --> 00:56:43,920 And then that information can be added to our climate models. 899 00:56:46,160 --> 00:56:47,800 By understanding bubbles, 900 00:56:47,800 --> 00:56:50,760 we'll have a better understanding of our planet. 901 00:56:56,520 --> 00:56:59,920 At the beginning of this film, I quoted Lord Kelvin 902 00:56:59,920 --> 00:57:03,960 talking about the physics that we can learn from bubbles. 903 00:57:03,960 --> 00:57:07,440 I hope that I've persuaded you that what you might have thought of 904 00:57:07,440 --> 00:57:11,840 as beautiful toys are enormously powerful scientific tools. 905 00:57:15,080 --> 00:57:16,920 They can help us explore nature 906 00:57:16,920 --> 00:57:21,600 at scales that are normally beyond our reach. 907 00:57:21,600 --> 00:57:25,080 They have surprising practical benefits too 908 00:57:25,080 --> 00:57:29,240 in diverse fields such as ship design and medicine. 909 00:57:29,240 --> 00:57:30,880 I hope that from now on 910 00:57:30,880 --> 00:57:34,400 you'll see bubbles in a completely different way. 911 00:57:37,240 --> 00:57:41,640 Imagine just one bubble and all the things it does while it exists, 912 00:57:41,640 --> 00:57:44,680 and then remember that underneath every breaking wave 913 00:57:44,680 --> 00:57:48,120 there are millions of bubbles and under every storm out at sea, 914 00:57:48,120 --> 00:57:51,360 there are millions of breaking waves. And on our planet right now 915 00:57:51,360 --> 00:57:54,600 there are tens or hundreds of storms going on, 916 00:57:54,600 --> 00:57:56,720 so overall on Earth right now, 917 00:57:56,720 --> 00:57:59,280 there are billions of bubbles out there. 918 00:57:59,280 --> 00:58:02,800 And the key to understanding all of what those bubbles are doing 919 00:58:02,800 --> 00:58:05,920 is understanding just one object, one little bubble. 920 00:58:05,920 --> 00:58:07,760 And the thing about bubbles is that 921 00:58:07,760 --> 00:58:09,800 once you know a little bit about them, 922 00:58:09,800 --> 00:58:11,680 you start seeing them everywhere 923 00:58:11,680 --> 00:58:14,040 and start appreciating what they're doing. 924 00:58:14,040 --> 00:58:17,360 And so understanding just one physical principle 925 00:58:17,360 --> 00:58:21,880 means that you start spotting it everywhere in your everyday world. 926 00:58:21,880 --> 00:58:26,120 So just one bit of physics can make your life so much richer. 927 00:58:53,160 --> 00:58:57,840 Subtitles by Red Bee Media Ltd