0:00:07 > 0:00:10This is a film about bubbles.
0:00:12 > 0:00:16To most people, bubbles are just toys children play with.
0:00:18 > 0:00:22But they're so much more.
0:00:23 > 0:00:27They're amazingly powerful tools that are pushing back
0:00:27 > 0:00:28the boundaries of science.
0:00:30 > 0:00:34I'm a bubble physicist and the reason that I care about bubbles
0:00:34 > 0:00:36is that they're part of how the planet works.
0:00:36 > 0:00:41Out at sea, breaking waves generate huge plumes of bubbles
0:00:41 > 0:00:44and those bubbles help the oceans breathe.
0:00:45 > 0:00:49Then there's the soap bubble with its delicate, fragile skin,
0:00:49 > 0:00:53something we can all see and touch, yet it can tell us
0:00:53 > 0:00:58about how nature works on scales as large as our solar system...
0:00:59 > 0:01:02..and as small as a single wavelength of light.
0:01:04 > 0:01:07Here we've identified what we think are interesting questions
0:01:07 > 0:01:10that will open up new areas in mathematics.
0:01:10 > 0:01:14We're learning that bubbles influence our world
0:01:14 > 0:01:17in all sorts of unexpected ways.
0:01:19 > 0:01:21From animal behaviour...
0:01:22 > 0:01:25..to the sounds of running water.
0:01:27 > 0:01:29And even the way drinks taste.
0:01:30 > 0:01:35The bubble cavity collapses, it can eject a tiny champagne jet
0:01:35 > 0:01:38up to several centimetres above the surface.
0:01:40 > 0:01:42And perhaps most exciting of all,
0:01:42 > 0:01:45we're only just beginning to appreciate
0:01:45 > 0:01:47the potential of bubble science.
0:01:49 > 0:01:52But there's still so much we don't know about bubbles,
0:01:52 > 0:01:53so much to learn.
0:01:53 > 0:01:57These little things are full of secrets and surprises.
0:01:59 > 0:02:03Welcome to my world. The wonderful world of bubbles.
0:02:25 > 0:02:27Bubbles really matter to our planet.
0:02:28 > 0:02:32Three quarters of the Earth is covered in water
0:02:32 > 0:02:35and just under the ocean's surface are billions of bubbles,
0:02:35 > 0:02:39formed as breaking waves drag air underwater.
0:02:42 > 0:02:44Right in front of our eyes,
0:02:44 > 0:02:47these bubbles are playing an important but invisible role.
0:02:50 > 0:02:53At a bubble, the ocean and atmosphere meet
0:02:53 > 0:02:55and both are affected.
0:02:58 > 0:02:59And this is all thanks
0:02:59 > 0:03:03to just a handful of a bubble's fundamental properties,
0:03:03 > 0:03:05which we're learning about in ever more detail.
0:03:07 > 0:03:09And that's the focus of my work,
0:03:10 > 0:03:13both out at sea
0:03:13 > 0:03:16and here in my laboratory at Southampton University.
0:03:18 > 0:03:21If we understand the basic processes of bubble formation
0:03:21 > 0:03:23in different situations in the ocean,
0:03:23 > 0:03:26we will be able to use that information
0:03:26 > 0:03:28to improve weather and climate models.
0:03:28 > 0:03:30You wouldn't think that something so small
0:03:30 > 0:03:33could affect something as big as a weather system, but it can.
0:03:37 > 0:03:40Let me start with a simple question...
0:03:41 > 0:03:43What is a bubble?
0:03:45 > 0:03:48There are two different but related kinds.
0:03:50 > 0:03:55The first are these - underwater bubbles, the focus of my research.
0:04:02 > 0:04:08But the bubbles most people know are these - soap bubbles.
0:04:10 > 0:04:14Despite being made of the most mundane of substances -
0:04:14 > 0:04:16soap, air and water -
0:04:16 > 0:04:18they're incredibly beautiful.
0:04:24 > 0:04:27These ethereal objects and the lessons they can teach us
0:04:27 > 0:04:30have fascinated scientists for decades.
0:04:37 > 0:04:41As the most famous of Victorian physicists, Lord Kelvin said...
0:04:43 > 0:04:45"Blow a soap bubble and observe it.
0:04:45 > 0:04:47"You may study it all your life
0:04:47 > 0:04:50"and draw one lesson after another in physics from it."
0:04:56 > 0:05:00Kelvin was fascinated by the way the delicate skin of the bubble
0:05:00 > 0:05:03affected the behaviour of light.
0:05:06 > 0:05:09And in particular, the beautiful colours it reveals.
0:05:19 > 0:05:24Just look at the fantastic patterns on this soap film here.
0:05:24 > 0:05:26They're there because the film is so thin -
0:05:26 > 0:05:30it's only a few hundredths of the diameter of a human hair.
0:05:32 > 0:05:35That means a soap film is around the same thickness
0:05:35 > 0:05:38as a single wavelength of visible light.
0:05:40 > 0:05:43The different colours on the film correspond to different
0:05:43 > 0:05:45wavelengths of light in the spectrum.
0:05:48 > 0:05:51And what fascinated Kelvin and scientists like him was,
0:05:51 > 0:05:53"How is this possible?
0:05:53 > 0:05:56"How can something so thin possibly exist?"
0:05:57 > 0:06:00And the answer is to do with the weird nature
0:06:00 > 0:06:02of something very everyday...water.
0:06:17 > 0:06:20So this is just freshwater and one of the things
0:06:20 > 0:06:23we associate most with liquids is droplet formation,
0:06:23 > 0:06:28so I'm going to use my sleeve and put some drops of water on it.
0:06:29 > 0:06:31And they're really pretty!
0:06:31 > 0:06:33You can see that these droplets are sort of curved inwards
0:06:33 > 0:06:37and the reason for that is that the water molecules on the surface
0:06:37 > 0:06:40are being pulled into the bulk of the water really strongly
0:06:40 > 0:06:41just on one side.
0:06:41 > 0:06:47So water behaves as though it's covered with an elastic skin,
0:06:47 > 0:06:49and we call that surface tension.
0:06:55 > 0:06:58Surface tension is one of the most delicate
0:06:58 > 0:07:01and intriguing forces in all of nature
0:07:01 > 0:07:04and its causes lie with the shape of the water molecule.
0:07:06 > 0:07:10Something very strange happens when hydrogen and oxygen -
0:07:10 > 0:07:12the atoms it's made of - join together.
0:07:14 > 0:07:17And the reason for that is that when the hydrogens join the oxygen,
0:07:17 > 0:07:20the molecule doesn't become a straight line,
0:07:20 > 0:07:22there's a kink in it, and so overall,
0:07:22 > 0:07:25one side of the molecule has a slight positive charge
0:07:25 > 0:07:28and the other side has a slight negative charge.
0:07:28 > 0:07:32What that means is that when other water molecules come close,
0:07:32 > 0:07:33the positive side of one
0:07:33 > 0:07:37is attracted to the negative sides of the other, and so overall,
0:07:37 > 0:07:40the bonds that attract water molecules to each other
0:07:40 > 0:07:42are really, really strong.
0:07:44 > 0:07:47These bonds mean that the molecules in the body of the water
0:07:47 > 0:07:49are pulled equally in every direction.
0:07:51 > 0:07:55But the molecules on the surface are pulled inwards...
0:07:55 > 0:07:58making the surface of the water like an elastic sheet.
0:07:59 > 0:08:02This is critical for understanding all the amazing properties
0:08:02 > 0:08:04of soap bubbles.
0:08:08 > 0:08:09But how?
0:08:09 > 0:08:13And crucially, why can't you make bubbles with pure water,
0:08:13 > 0:08:14why do you need soap?
0:08:15 > 0:08:20This was a surprisingly difficult question to answer
0:08:20 > 0:08:23and the key to solving it came not from the great men
0:08:23 > 0:08:28of Victorian science, but from an obscure house in Germany.
0:08:31 > 0:08:34Some of the earliest experiments on surface tension were done
0:08:34 > 0:08:36by a German lady called Agnes Pockels
0:08:36 > 0:08:39and her work was only published in 1891.
0:08:39 > 0:08:41I've got a copy of the paper here.
0:08:41 > 0:08:47The paper is prefaced by a note by Lord Rayleigh,
0:08:47 > 0:08:50who was a very famous English physicist, and this is what he said
0:08:50 > 0:08:52and this was his note to Nature.
0:08:52 > 0:08:54"I shall be obliged if you can find space
0:08:54 > 0:08:57"for the accompanying translation of an interesting letter
0:08:57 > 0:09:00"which I have received from a German lady,
0:09:00 > 0:09:03"who with very homely appliances has arrived at viable results
0:09:03 > 0:09:07"respecting the behaviour of contaminated water surfaces."
0:09:07 > 0:09:10The reason that he wrote the preface is because
0:09:10 > 0:09:12Agnes was born in 1862 in a time
0:09:12 > 0:09:16when women were not allowed to study physics to any great degree
0:09:16 > 0:09:18or to go to university,
0:09:18 > 0:09:21and so she was not allowed to publish the paper herself.
0:09:22 > 0:09:26The first thing Agnes did, just using the equipment in her kitchen,
0:09:26 > 0:09:29was come up with a new and incredibly clever way
0:09:29 > 0:09:32of measuring the surface tension of water.
0:09:33 > 0:09:35I've got a version of her experiments here
0:09:35 > 0:09:40and what she was looking at was how hard surface tension can pull
0:09:40 > 0:09:42and she had this experiment...
0:09:42 > 0:09:45Now, she describes it as a small disc at the bottom
0:09:45 > 0:09:48and that's been interpreted as being a button,
0:09:48 > 0:09:49so I've got a button on mine.
0:09:49 > 0:09:52My button is held by elastic thread
0:09:52 > 0:09:56and so the elastic thread is pulling upwards on the button
0:09:56 > 0:09:59and if I let it go,
0:09:59 > 0:10:02you'll see it hangs quite a long way above the water surface.
0:10:02 > 0:10:05But when the button is touching the water,
0:10:05 > 0:10:07the surface tension is pulling the button down
0:10:07 > 0:10:09and the elastic is pulling the button up,
0:10:09 > 0:10:12and Agnes realised that you could measure surface tension
0:10:12 > 0:10:17by adjusting the pull from above
0:10:17 > 0:10:20just until you got to the point
0:10:20 > 0:10:23where the button was just about to break away,
0:10:23 > 0:10:25and that moment there is when the forces are balanced.
0:10:25 > 0:10:28She had scales effectively that measured
0:10:28 > 0:10:30how much upward pull there was
0:10:30 > 0:10:33and so she knew how much downward pull
0:10:33 > 0:10:34the water was providing.
0:10:39 > 0:10:42But what Agnes did next was the really clever bit
0:10:42 > 0:10:46and it would be the key to understanding soap bubbles...
0:10:46 > 0:10:48Why they exist and what they do.
0:10:50 > 0:10:54Agnes realised that you could also use this device to measure
0:10:54 > 0:10:58how surface tension changed in different situations.
0:10:58 > 0:11:00What she did was, she contaminated the surface.
0:11:00 > 0:11:02This is just detergent.
0:11:02 > 0:11:06I'm just going to put a few spots of it nearby
0:11:06 > 0:11:08and as I put them on the water surface,
0:11:08 > 0:11:11the detergent is lowering the surface tension
0:11:11 > 0:11:13and so the button will pop off the surface.
0:11:16 > 0:11:20Agnes' measurements showed that adding soap to water
0:11:20 > 0:11:22reduces its surface tension.
0:11:23 > 0:11:25That's a crucial observation.
0:11:26 > 0:11:29It's the answer to the first question about soap bubbles...
0:11:32 > 0:11:37And why you can't make bubbles with clean or pure water.
0:11:40 > 0:11:43If you make bubbles in clean water and they rise to the surface,
0:11:43 > 0:11:47they make a spherical lid like this for a very short period of time
0:11:47 > 0:11:50and then the surface tension of the water is so strong
0:11:50 > 0:11:52that it pulls this film
0:11:52 > 0:11:55and breaks it up into lots and lots of tiny, tiny droplets,
0:11:55 > 0:11:58so clean water has surface tension which is far too strong
0:11:58 > 0:12:01to let foam like this last
0:12:01 > 0:12:03and that's where the bubblebath comes in.
0:12:04 > 0:12:08The soap molecules in the bubblebath position themselves
0:12:08 > 0:12:11at the surface of the water,
0:12:11 > 0:12:13changing how the surface behaves.
0:12:18 > 0:12:20If we look at one of these bubbles here,
0:12:20 > 0:12:23the reason that this thin film can exist for so long
0:12:23 > 0:12:26is that the soap molecules have reduced the water surface tension,
0:12:26 > 0:12:30so the pull to make that pop isn't as strong as it was.
0:12:30 > 0:12:33The soap molecules are allowing these thin films,
0:12:33 > 0:12:36beautiful thin films, to last for a really long time.
0:12:37 > 0:12:39But the fact that soap and water
0:12:39 > 0:12:42can combine to make something so thin...
0:12:43 > 0:12:46..doesn't just mean that we have beautiful toys to play with.
0:12:47 > 0:12:49Soap films are helping us solve
0:12:49 > 0:12:51the toughest mathematical problems in nature.
0:12:58 > 0:13:01These are the storms in Jupiter's atmosphere.
0:13:04 > 0:13:07This is a massive example of one of these tough problems -
0:13:07 > 0:13:11the complex ways that fluids flow.
0:13:12 > 0:13:16And this is that process, recreated on the surface of a soap bubble.
0:13:20 > 0:13:22Fluid flows really beautiful,
0:13:22 > 0:13:24but it's also really difficult to study
0:13:24 > 0:13:26and soap films can help
0:13:26 > 0:13:30because by following the colours on the surface of the film
0:13:30 > 0:13:33you can track how the fluid is moving and that gives you a way into
0:13:33 > 0:13:39studying systems that are otherwise either inaccessible or invisible.
0:13:41 > 0:13:44These are clouds above the Indian Ocean.
0:13:44 > 0:13:47They form these patterns - vortices -
0:13:47 > 0:13:49as they get blown around an island.
0:13:51 > 0:13:53These and other flow patterns -
0:13:53 > 0:13:56for instance, the way that water travels around a solid object -
0:13:56 > 0:14:01can be replicated and studied in soap films in a laboratory.
0:14:10 > 0:14:14And it's not just questions about fluid flow that soap films
0:14:14 > 0:14:15could help answer.
0:14:22 > 0:14:26Soap films are mathematical problem solvers.
0:14:28 > 0:14:30You can see it in their almost uncanny search
0:14:30 > 0:14:32for geometrical perfection.
0:14:35 > 0:14:38Left to themselves, they're perfect spheres.
0:14:40 > 0:14:42But they can do other tricks too.
0:14:44 > 0:14:47For instance, what's the most efficient way
0:14:47 > 0:14:49to join these four points?
0:14:49 > 0:14:54Blow on the soap film, and it finds precisely the right answer.
0:14:59 > 0:15:03All these angles are exactly 120 degrees.
0:15:06 > 0:15:08Soap films do this because of surface tension,
0:15:08 > 0:15:12pulling in every direction on the bubble's surface.
0:15:16 > 0:15:20That means a soap film will always try and minimise its surface area.
0:15:24 > 0:15:28Free-floating bubbles are spherical because that's the shape
0:15:28 > 0:15:30with the least amount of surface for any given volume.
0:15:33 > 0:15:36The soap film connects the four points like this
0:15:36 > 0:15:39because it's the arrangement with the least surface area.
0:15:42 > 0:15:46And what's really amazing is that this ability of soap films
0:15:46 > 0:15:50to minimise their area is still at the forefront of science.
0:16:13 > 0:16:16In nature, these are common occurrences.
0:16:17 > 0:16:20They're called "singularities,"
0:16:20 > 0:16:23sudden changes in shape or structure.
0:16:27 > 0:16:30They're incredibly hard to describe and understand mathematically.
0:16:32 > 0:16:35And that's where soap films come in.
0:16:38 > 0:16:43Here's one captured by a camera that slows down time fifty-fold.
0:16:45 > 0:16:47Stretched between two hoops,
0:16:47 > 0:16:49it suddenly splits into two,
0:16:49 > 0:16:51instantly changing
0:16:51 > 0:16:53from one shape into another.
0:16:58 > 0:17:03This is Professor Ray Goldstein at Cambridge University.
0:17:03 > 0:17:07For him, the soap film could be a vital clue to understanding
0:17:07 > 0:17:08the singularity.
0:17:11 > 0:17:12You see them all the time...
0:17:12 > 0:17:14When a drop of fluid breaks up.
0:17:14 > 0:17:17When certain structures come off of the sun
0:17:17 > 0:17:19they form these beautiful arcing filaments
0:17:19 > 0:17:22and give rise to huge ejections from the sun.
0:17:22 > 0:17:24So on every length scale you can imagine...
0:17:24 > 0:17:27And for many decades physicists and mathematicians
0:17:27 > 0:17:30have been interested in understanding the mathematics
0:17:30 > 0:17:31of what we call the singularity,
0:17:31 > 0:17:34the moment that rearrangement happens.
0:17:34 > 0:17:38And they're so non-linear, they're so hard to solve
0:17:38 > 0:17:41that we really are at the infancy of this study
0:17:41 > 0:17:42of these kinds of singularities.
0:17:42 > 0:17:46What we hope is that we'll see a pattern emerging
0:17:46 > 0:17:50that will teach us something deep about these kinds of transitions.
0:17:52 > 0:17:55And the surface tension on the soap film is the key.
0:17:56 > 0:17:58It ensures that they perform their shape changes
0:17:58 > 0:18:00with the minimum use of energy,
0:18:00 > 0:18:03which is the preferred way nature operates.
0:18:06 > 0:18:09They're also relatively easy to study in the lab.
0:18:09 > 0:18:14For us, this is a laboratory example of a singularity
0:18:14 > 0:18:18that is similar in its structure to many kinds of singularities
0:18:18 > 0:18:20that occur in nature.
0:18:20 > 0:18:24It has the advantage that we can study it in great detail in the lab.
0:18:24 > 0:18:27We can do these high-speed movies. We can do some mathematics.
0:18:27 > 0:18:31We can vary particular quantities like the viscosity of the fluid
0:18:31 > 0:18:33or the surface tension, the size of the wire,
0:18:33 > 0:18:36whereas it's difficult studying the sun
0:18:36 > 0:18:39since we can't get near the sun to fiddle with it.
0:18:39 > 0:18:43By looking at these soap films in the lab
0:18:43 > 0:18:45where we can control everything,
0:18:45 > 0:18:48we have a hope of testing our theories in a way that allows us
0:18:48 > 0:18:51to go back and forth and refine them to the point that we can finally say,
0:18:51 > 0:18:53"Yes, I think we understand what's going on."
0:19:07 > 0:19:10It's incredible that we can study the sun
0:19:10 > 0:19:12with the help of a soap film,
0:19:13 > 0:19:15that it might unlock the secrets
0:19:15 > 0:19:18behind some of the strangest phenomena in the universe.
0:19:24 > 0:19:28But amazing though they are, I want to show you that soap films
0:19:28 > 0:19:31and soap bubbles are just the start of the story.
0:19:35 > 0:19:38I want to return to the other kind of bubble I mentioned.
0:19:38 > 0:19:40The kind I study.
0:19:40 > 0:19:42Underwater bubbles.
0:19:42 > 0:19:47These are pockets of gas that are trapped within liquids.
0:19:50 > 0:19:53They're a treasure chest of scientific riches
0:19:53 > 0:19:55and they affect everything
0:19:55 > 0:19:57from animal behaviour to the taste of champagne.
0:20:01 > 0:20:04And they make a surprisingly important contribution
0:20:04 > 0:20:07to the Earth's climate.
0:20:11 > 0:20:14I want to start this story here in this pool,
0:20:14 > 0:20:18which is equipped to make huge plumes of underwater bubbles.
0:20:20 > 0:20:23We'll see these underwater bubbles dramatically change the properties
0:20:23 > 0:20:26of the liquid they move in.
0:20:26 > 0:20:30And that can be incredibly useful.
0:20:30 > 0:20:34In this pool, it's used to help train springboard divers.
0:20:37 > 0:20:40Diving pools like this have a big air reservoir underneath.
0:20:40 > 0:20:43They can send a big plume of bubbles up and that means that
0:20:43 > 0:20:44when a diver is learning a dive,
0:20:44 > 0:20:48they come down and instead of hitting flat water,
0:20:48 > 0:20:50they hit bubbly water with a lower density,
0:20:50 > 0:20:54so that instead of having a short, sharp shock,
0:20:54 > 0:20:56they get slowed down but over a longer period of time,
0:20:56 > 0:20:58so bubbles help divers train.
0:21:00 > 0:21:03And it's because the bubbles do this that...
0:21:03 > 0:21:05although I haven't done any diving for a long time,
0:21:05 > 0:21:08I'm prepared to try it again.
0:21:20 > 0:21:23The reason bubbles make water less painful to dive into
0:21:23 > 0:21:25goes to the heart of what a bubble actually is.
0:21:28 > 0:21:31A bubble is what you get when a liquid-like water
0:21:31 > 0:21:33and a gas-like air
0:21:33 > 0:21:37that really don't want to mix are forced together.
0:21:39 > 0:21:42The surface tension of water tries to squeeze the bubble
0:21:42 > 0:21:45into having a smaller surface area.
0:21:46 > 0:21:49And the air is rising as fast as possible.
0:21:54 > 0:21:58But during their brief co-existence, they form something new,
0:21:58 > 0:22:01a mixture much more substantial than air,
0:22:01 > 0:22:05but considerably softer and less dense than water.
0:22:14 > 0:22:17It's hard to get round. That happened really quickly.
0:22:19 > 0:22:22But it's good. I did it. I haven't done that dive for six years.
0:22:23 > 0:22:25Bubbles are good, right?
0:22:29 > 0:22:32Animals that spend a lot of time underwater
0:22:32 > 0:22:35have evolved some incredibly ingenious ways
0:22:35 > 0:22:38of exploiting the fact that bubbles reduce the density of water.
0:22:43 > 0:22:47These are Emperor penguins, diving to depths of ten metres.
0:22:49 > 0:22:51They store air in their feathers
0:22:51 > 0:22:55which they release as clouds of bubbles as they zoom upwards.
0:22:57 > 0:22:59This makes the water around the penguin less dense
0:22:59 > 0:23:01and much easier to move through.
0:23:05 > 0:23:08It means the penguins can travel up to 50% faster
0:23:08 > 0:23:10than if there were no bubbles.
0:23:12 > 0:23:16I love this, because it shows just how useful bubbles are.
0:23:16 > 0:23:19It helps divers like me get into the water safely.
0:23:21 > 0:23:24And it helps the penguins get out safely.
0:23:39 > 0:23:43And in the shipping industry, there's intensive research going on
0:23:43 > 0:23:46into how bubbles can make water less dense and easier to move through.
0:23:51 > 0:23:55This tall steel drum spinning inside a cylinder of water
0:23:55 > 0:23:58is part of an experiment at a Dutch university.
0:24:01 > 0:24:06Engineers here stream bubbles in varying amounts and sizes across
0:24:06 > 0:24:10the drum's surface to learn how they reduce friction from the water.
0:24:15 > 0:24:19And in late 2012, Japanese shipbuilders Mitsubishi
0:24:19 > 0:24:23fitted a bubble lubrication system under one of their ships.
0:24:24 > 0:24:28They hope that this will reduce fuel consumption by up to 15%,
0:24:28 > 0:24:32potentially saving billions of pounds.
0:24:36 > 0:24:40Bubbles are proving to be incredibly useful to the modern world.
0:24:43 > 0:24:46The next really important use of bubbles is connected
0:24:46 > 0:24:49to one of their most surprising properties,
0:24:49 > 0:24:52their relationship with sound.
0:24:55 > 0:24:58This has all sorts of consequences -
0:24:58 > 0:25:01everywhere from industry to medical research.
0:25:01 > 0:25:03But, for me, it's a fabulous tool
0:25:03 > 0:25:08because sound lets me monitor what bubbles are doing in the ocean.
0:25:08 > 0:25:12And this will help me understand their role in our climate.
0:25:12 > 0:25:14It goes pop, pop, pop, pop.
0:25:14 > 0:25:18Bubble acoustics is a branch of science in its own right,
0:25:18 > 0:25:23but it begins with the simplest of observations.
0:25:23 > 0:25:28So, I have a tank of water here with a nozzle down at the bottom
0:25:28 > 0:25:31and I'm going to feed air into it...
0:25:34 > 0:25:37..by pushing on a syringe here.
0:25:37 > 0:25:40So I can see there's air coming along the nozzle.
0:25:40 > 0:25:43And I'm just going to make one bubble at a time.
0:25:45 > 0:25:47And here's the thing -
0:25:47 > 0:25:50if you put your ear up against the tank,
0:25:50 > 0:25:54you can hear it's going "ping, ping, ping" for each little bubble.
0:25:58 > 0:26:01Every new bubble that's formed like this
0:26:01 > 0:26:05is like a little bell being hit with a hammer and it goes "ping".
0:26:07 > 0:26:10If you pour out a drink or you hear a babbling stream,
0:26:10 > 0:26:12this is the sound you're hearing,
0:26:12 > 0:26:14you're hearing new bubbles being formed.
0:26:14 > 0:26:17But they tell you more than that.
0:26:17 > 0:26:19Now I'm going to make some big bubbles,
0:26:19 > 0:26:21just by putting a bottle in the water.
0:26:21 > 0:26:25And the sound is very, very different. So if I...
0:26:25 > 0:26:27It's not very elegant. I've just got my thumb over the top
0:26:27 > 0:26:30and I'm going to put this down below and let bubbles of air come out.
0:26:30 > 0:26:34BUBBLES GURGLE
0:26:36 > 0:26:39And you're all familiar with that sound,
0:26:39 > 0:26:42but the interesting thing here is that the big bubbles
0:26:42 > 0:26:45make a deeper note and the smaller bubbles make a higher note.
0:26:45 > 0:26:47So they're like big and little bells.
0:26:47 > 0:26:50When you hear this "ping" noise of a new bubble being formed,
0:26:50 > 0:26:52it's telling you how big it is.
0:26:52 > 0:26:54And it's a very precise relationship.
0:26:58 > 0:27:02Bubbles make sounds for the same reasons many other things do -
0:27:02 > 0:27:04they vibrate or oscillate.
0:27:06 > 0:27:08GUITAR NOTE SOUNDS
0:27:09 > 0:27:13They do this because the air inside the bubble can be squashed
0:27:13 > 0:27:15and then the squashed air pushes back.
0:27:18 > 0:27:22But a few years ago, some colleagues and I wanted to solve a mystery.
0:27:22 > 0:27:24THUMB PIANO NOTE SOUNDS
0:27:24 > 0:27:28What starts bubbles oscillating in the first place?
0:27:28 > 0:27:32If you think of bubbles like bells, it's a bit like asking
0:27:32 > 0:27:35what is the hammer that hits the bell, what gets it started?
0:27:35 > 0:27:37So, in order to answer that question,
0:27:37 > 0:27:39I took this series of photographs
0:27:39 > 0:27:43and what you're looking at here is a tube of air
0:27:43 > 0:27:46where air is being blown upwards into water,
0:27:46 > 0:27:50and this is the moment that the bubble breaks away from the tube
0:27:50 > 0:27:53and escapes up into the rest of the water column.
0:27:53 > 0:27:57So you can see right here that just as the bubble starts to break,
0:27:57 > 0:28:00it generates this neck which narrows.
0:28:00 > 0:28:03And then, as we carry on in time, it gets narrower and narrower.
0:28:03 > 0:28:06This is the last moment that the bubble is attached
0:28:06 > 0:28:09to the rest of the gas before it breaks away.
0:28:09 > 0:28:13And in the next frame, a 10th of a millisecond later,
0:28:13 > 0:28:15it's over, the bubble is free.
0:28:15 > 0:28:19And what we found is that the sound all originates from this point.
0:28:19 > 0:28:24Bubbles hate sharp corners, and that bubble's got a corner.
0:28:24 > 0:28:27So all of that liquid rushes up inside the bubble
0:28:27 > 0:28:29to get rid of the corner,
0:28:29 > 0:28:32we get this little jet, that squeezes the air inside the bubble
0:28:32 > 0:28:34and that's what starts these oscillations.
0:28:34 > 0:28:36So we could actually physically see
0:28:36 > 0:28:39the hammer hitting the bell.
0:28:41 > 0:28:42PING
0:28:44 > 0:28:47WATER GUSHES
0:28:47 > 0:28:50It's astonishing to realise that all of these sounds
0:28:50 > 0:28:53are the sounds of bubbles being made.
0:28:53 > 0:28:55WINE GLUGS
0:29:01 > 0:29:04But how about animals that live in water?
0:29:04 > 0:29:07Then the relationship between bubbles and sound
0:29:07 > 0:29:09is incredibly important.
0:29:09 > 0:29:13Imagine you're a sea creature and you're not just living in an ocean,
0:29:13 > 0:29:15but you're living in a bubbly ocean.
0:29:15 > 0:29:18Now, most marine creatures get a lot of their information from sound.
0:29:18 > 0:29:21So they know about what's going on in the world around them
0:29:21 > 0:29:23because sound is coming to them.
0:29:23 > 0:29:26And bubbles are directly affecting that sound. They're absorbing it
0:29:26 > 0:29:27and they're scattering it.
0:29:27 > 0:29:29So, if you're a marine creature,
0:29:29 > 0:29:33the bubbles are directly affecting your perception of your world.
0:29:37 > 0:29:39Humpback whales hunt small fish
0:29:39 > 0:29:42by exploiting the acoustic properties of bubbles.
0:29:45 > 0:29:47The whales blow columns of bubbles
0:29:47 > 0:29:51and also send sound into those bubbles which is trapped by them.
0:29:51 > 0:29:53This terrifies the fish
0:29:53 > 0:29:56and make them easy prey for the whales.
0:30:03 > 0:30:05The way bubbles vibrate
0:30:05 > 0:30:08and interact with sounds can be exploited by humans too.
0:30:10 > 0:30:12Now, then, I have here...
0:30:12 > 0:30:15This is Professor Tim Leighton, my scientific mentor
0:30:15 > 0:30:19and probably the world's foremost expert on bubble acoustics -
0:30:19 > 0:30:23the relationship between bubbles and sound.
0:30:23 > 0:30:28And what he's about to show me is, well, it's almost like magic.
0:30:30 > 0:30:32Here we have a device that we've built.
0:30:32 > 0:30:35It's a black cone. You could fit it on the end of a tap
0:30:35 > 0:30:38or on top of a fire extinguisher or something.
0:30:38 > 0:30:41And just cold water is coming out of it.
0:30:41 > 0:30:45This is an experimental rig, which, thanks to bubbles,
0:30:45 > 0:30:49could one day completely change the way we clean things.
0:30:50 > 0:30:54Lipstick is notoriously difficult to remove
0:30:54 > 0:30:57because it's designed to be sticky.
0:30:57 > 0:31:00And if we take this normal kitchen tile
0:31:00 > 0:31:05and we were to, say, write - I'm not very good writing with lipstick -
0:31:05 > 0:31:10say, BBC on it... Like this.
0:31:12 > 0:31:17And then we hold this into the stream of cold water.
0:31:17 > 0:31:19As expected, it stays on.
0:31:19 > 0:31:21It's really good at sticking.
0:31:21 > 0:31:24Now, with the flick of a switch, the magic happens.
0:31:24 > 0:31:26And here we go.
0:31:26 > 0:31:29It's stunning. The difference is amazing.
0:31:29 > 0:31:32This incredibly effective way of cleaning
0:31:32 > 0:31:36relies entirely on bubbles and their relationship with sound.
0:31:36 > 0:31:42Water comes through this device and we add microscopic bubbles
0:31:42 > 0:31:49and we had ultrasound, using this silver sound source at the back.
0:31:49 > 0:31:53And when the bubbles hit the device to be cleaned,
0:31:53 > 0:31:57the ultrasound hits them and turns these bubbles
0:31:57 > 0:31:59from nice little balls of gas
0:31:59 > 0:32:04into quite excitable little scrubbing machines.
0:32:05 > 0:32:08This works because the bubbles are resonating,
0:32:08 > 0:32:10vibrating in response to ultrasound -
0:32:10 > 0:32:15the high-frequency sound waves that are travelling through the water.
0:32:17 > 0:32:20The wall is shimmering and moving very rapidly
0:32:20 > 0:32:23with thousands of tiny little ripples.
0:32:23 > 0:32:26And at the edge of those ripples, you have very high shear in the water.
0:32:26 > 0:32:30And so what that does is, it scrubs away at any surface.
0:32:30 > 0:32:34- Shear is like this sort of action, so it's scrubbing?- That's right.
0:32:34 > 0:32:38It really is scrubbing away at the surface, cleaning away,
0:32:38 > 0:32:41removing dirt and particles.
0:32:41 > 0:32:44So the bubble wall shimmers to clean,
0:32:44 > 0:32:48but specifically, using the bubbles in this way, they're targeted to
0:32:48 > 0:32:52seek and find crevices and cracks, and clean the dirt out of those.
0:32:53 > 0:32:56This is the second really clever bit.
0:32:56 > 0:32:59The vibrating bubbles send out sound.
0:32:59 > 0:33:03This echoes off nearby surfaces, and the reflected waves pull
0:33:03 > 0:33:09the bubbles closer to those surfaces and into any tiny cracks that exist.
0:33:09 > 0:33:11Those crevices are exactly the places
0:33:11 > 0:33:14that are usually hardest to clean.
0:33:16 > 0:33:20So it's really strongly attracted into that crevice
0:33:20 > 0:33:22and it burrows into it, keeps burrowing,
0:33:22 > 0:33:27digging out the dirt as it goes because its surface is shimmering.
0:33:27 > 0:33:30And what sort of applications has this got out in the real world?
0:33:30 > 0:33:32We're looking first of all
0:33:32 > 0:33:36at manufacturers with production lines with big plants.
0:33:36 > 0:33:38Right at the other end of the scale, we would like to see
0:33:38 > 0:33:40one of these in every home and every hospital
0:33:40 > 0:33:44so that hands, scalpels, endoscopes
0:33:44 > 0:33:49and anything else that you want to clean is safely cleaned
0:33:49 > 0:33:52and, not only that, but cleaned using cold water
0:33:52 > 0:33:53with very little additives,
0:33:53 > 0:33:57so that you're not wasting water and so that you don't incur
0:33:57 > 0:33:59the energy bills and the clean-up bill
0:33:59 > 0:34:01to make that water drinkable after.
0:34:01 > 0:34:04And all that is possible because of tiny bubbles
0:34:04 > 0:34:06- that we can't even see?- Exactly.
0:34:09 > 0:34:12So, we're going to give you the microbubbles now.
0:34:13 > 0:34:16Three, two, one, inject.
0:34:17 > 0:34:21This is Charing Cross Hospital, and here they're using
0:34:21 > 0:34:25the way that bubbles respond to sound very differently...
0:34:25 > 0:34:28To see inside a person.
0:34:28 > 0:34:31They're injecting microscopic bubbles
0:34:31 > 0:34:34into the patient's bloodstream.
0:34:36 > 0:34:40These bubbles dramatically improve the quality of ultrasound scans,
0:34:40 > 0:34:45giving doctors a much better chance of making an accurate diagnosis.
0:34:46 > 0:34:50Breathe in, sir. Hold your breath there very still.
0:34:50 > 0:34:52Perfect. There you go.
0:34:52 > 0:34:55Can you see how it's enhancing all around that lesion now?
0:34:55 > 0:34:58There is the contrast in here, you see?
0:34:58 > 0:35:03All done. Didn't feel too much at all, hopefully? Good. Perfect.
0:35:03 > 0:35:07Normally, ultrasound works by sending high-frequency sound
0:35:07 > 0:35:10into the body and listening to the echoes that come back.
0:35:12 > 0:35:16The problem is, there isn't much contrast between
0:35:16 > 0:35:18different tissues of the body.
0:35:18 > 0:35:20But, if bubbles are present,
0:35:20 > 0:35:24the ultrasound makes them vibrate and scatter sound.
0:35:24 > 0:35:28This makes the echo that comes back much stronger.
0:35:30 > 0:35:34At Oxford University, my friend and fellow bubble scientist,
0:35:34 > 0:35:37Dr Eleanor Stride, explains.
0:35:37 > 0:35:40So we put these very, very tiny bubbles into the bloodstream
0:35:40 > 0:35:42and suddenly you're able to see where the blood is flowing.
0:35:42 > 0:35:45If I show you an image of that in action...
0:35:45 > 0:35:47This is a scan of the liver.
0:35:47 > 0:35:49This is before the contrast agent has got to the liver.
0:35:49 > 0:35:53And what you'll see when I start the video is, the contrast agent
0:35:53 > 0:35:56- starts to wash into the blood vessels.- So the bubbles are coming...
0:35:56 > 0:35:58You can see all these little tendrils. Those are blood vessels?
0:35:58 > 0:36:01Those are blood vessels, exactly. So, because bubbles are in there,
0:36:01 > 0:36:03they're reflecting the sound really strongly.
0:36:03 > 0:36:06You see the major blood vessel here and smaller ones branching off.
0:36:06 > 0:36:10- We can see there's a lot of blood in this area here.- Nice and clearly.
0:36:10 > 0:36:13And you can't see those under normal ultrasound imaging.
0:36:13 > 0:36:14And this is what bubbles provide.
0:36:14 > 0:36:17- So you can see abnormal tissue, basically?- Precisely.
0:36:22 > 0:36:25Bubbles resonate like musical instruments.
0:36:25 > 0:36:29That's the secret behind many of the things we're now using them for.
0:36:29 > 0:36:32But there is another aspect of bubble science
0:36:32 > 0:36:37with perhaps the most surprising consequences of all.
0:36:40 > 0:36:44It's to do with the way bubbles move through the liquid
0:36:44 > 0:36:47and carry things to the air and back.
0:36:49 > 0:36:51This affects many aspects of nature
0:36:51 > 0:36:54and we'll see how it's vital to our oceans and atmosphere.
0:36:56 > 0:36:58And to see how that works,
0:36:58 > 0:37:01I want to show you how bubbles do what they're most famous for...
0:37:04 > 0:37:07Perform their magic in champagne.
0:37:16 > 0:37:18I've got quite mixed feelings about today
0:37:18 > 0:37:22because on one hand, this is the bubble physicist's dream day out
0:37:22 > 0:37:25and it's something I've always wanted to do.
0:37:25 > 0:37:28And on the other hand, I'm never going to live this down
0:37:28 > 0:37:32because this is the Champagne region of France, and I'm here
0:37:32 > 0:37:35to spend the day in a laboratory where they study champagne.
0:37:35 > 0:37:37But - would-be teasers take note -
0:37:37 > 0:37:39there is a scientific reason for this,
0:37:39 > 0:37:43because bubbles are crucial to how we taste and perceive champagne.
0:37:44 > 0:37:46Before going to the lab,
0:37:46 > 0:37:50I start my investigation into how bubbles work in champagne
0:37:50 > 0:37:53in one of the classiest restaurants in Reims,
0:37:53 > 0:37:55the capital of the Champagne region.
0:37:58 > 0:38:01We're starting on a big one.
0:38:01 > 0:38:03I'm here with sommelier Philippe Jamesse
0:38:03 > 0:38:09and physicist Gerard Liger-Belair, who studies champagne bubbles.
0:38:11 > 0:38:15To show me how important bubble movement is in champagne,
0:38:15 > 0:38:16they subjected me to a test.
0:38:18 > 0:38:20They've poured the same champagne
0:38:20 > 0:38:24into three differently shaped glasses.
0:38:24 > 0:38:27Apparently, the bubbles will move differently
0:38:27 > 0:38:30in the different glasses,
0:38:30 > 0:38:34and that in turn will change the way the champagne smells and tastes.
0:38:35 > 0:38:38But I was doubtful I'd notice
0:38:38 > 0:38:42because when it comes to champagne, I'm a complete novice.
0:38:45 > 0:38:48It is actually really different.
0:38:51 > 0:38:55And that one's much... It's like it gets a lot calmer.
0:38:58 > 0:39:02In a tall, thin glass, the bubbles reaching the surface are bigger
0:39:02 > 0:39:06and are moving faster than in a wide glass.
0:39:09 > 0:39:12That makes the drink smell and taste very different.
0:39:16 > 0:39:19To find out why, I went with Gerard
0:39:19 > 0:39:22to his lab at the University of Reims.
0:39:24 > 0:39:28A lab dedicated to the study of champagne bubbles.
0:39:30 > 0:39:35About 15 years ago, I got interested in bubbles,
0:39:35 > 0:39:39especially by drinking - not champagne, I was too young -
0:39:39 > 0:39:41but I was drinking beer.
0:39:41 > 0:39:46And I focused on the tiny bubble trains on the beer wall
0:39:46 > 0:39:48- on the glass wall - and I imagined
0:39:48 > 0:39:52that it could make a fantastic PhD project.
0:39:52 > 0:39:55So from the food mechanics point of view...
0:39:55 > 0:39:58- In vino veritas! - You're right. In vino veritas, yes.
0:39:58 > 0:40:00I knew that obviously, bubbles
0:40:00 > 0:40:02are very important in the champagne industry,
0:40:02 > 0:40:08so maybe I could mix my passion with bubbles with the champagne industry
0:40:08 > 0:40:11if they want to know more information
0:40:11 > 0:40:13about their bubbling process.
0:40:15 > 0:40:18Champagne bubbles are full of carbon dioxide,
0:40:18 > 0:40:21a gas made while the drink was being fermented.
0:40:24 > 0:40:28When the bottle is sealed, the gas stays dissolved inside the liquid.
0:40:32 > 0:40:35When the cork comes off, the gas escapes as bubbles.
0:40:36 > 0:40:40The glass they're in has a big influence on their journey.
0:40:42 > 0:40:44Gerard wanted to know
0:40:44 > 0:40:47how that process starts, how the bubble forms.
0:40:47 > 0:40:49What's this showing us?
0:40:49 > 0:40:53Yeah, this is champagne and we have fitted
0:40:53 > 0:40:56microscope objective on a high-speed video camera
0:40:56 > 0:40:58to see where the bubbles are coming from.
0:40:58 > 0:41:01- And so where are they forming? - They form everywhere
0:41:01 > 0:41:04where a tiny particle or imperfection is.
0:41:04 > 0:41:08So we are going to see this on the screen.
0:41:08 > 0:41:12You can clearly see that the bubbles are not coming from nowhere,
0:41:12 > 0:41:15they're coming from a tiny particle stuck on the wall,
0:41:15 > 0:41:18and this is indeed a tiny dust particle.
0:41:18 > 0:41:22- So they're actually coming from specks of dirt?- Yes, you're right.
0:41:22 > 0:41:25Gerard had shown that bubbles are born
0:41:25 > 0:41:29whenever there are imperfections on the glass's surface.
0:41:29 > 0:41:32And this has surprising consequences.
0:41:33 > 0:41:37This says to me that you can artificially make places,
0:41:37 > 0:41:41you could choose that your champagne glass would make more bubbles.
0:41:41 > 0:41:45When you see such a column on the centre of the glass,
0:41:45 > 0:41:46it is because the glass has been etched.
0:41:46 > 0:41:50So they've scratched away at the bottom to make these rough surfaces?
0:41:50 > 0:41:51Yes, to promote effervescence.
0:41:51 > 0:41:54By putting dye into the champagne,
0:41:54 > 0:41:58you can clearly see the effect of scratching the bottom of the glass.
0:42:00 > 0:42:03It forces the bubbles to travel in a narrow column
0:42:03 > 0:42:04up the centre of the glass.
0:42:06 > 0:42:09And we'll see that this is really important.
0:42:09 > 0:42:12The lovely thing that I think is really clear here
0:42:12 > 0:42:14is that you can see the bubbles are starting really tiny
0:42:14 > 0:42:17and they're being released and they're growing as they go up
0:42:17 > 0:42:19and as they get more and more buoyant, they get bigger,
0:42:19 > 0:42:20they go faster and faster.
0:42:20 > 0:42:23Yes, because the CO2 continues to accumulate
0:42:23 > 0:42:26inside the rising bubbles, so it grows inside and accelerates.
0:42:28 > 0:42:31So, in a tall glass, the bubbles travel further
0:42:31 > 0:42:37and they get bigger and are moving much further than in a short glass.
0:42:37 > 0:42:41This has the effect of mixing the drink more vigorously,
0:42:41 > 0:42:45which in part explains the more intense flavour
0:42:45 > 0:42:48I'd noticed in the tall, thin glass.
0:42:48 > 0:42:51But that's only half the story.
0:42:51 > 0:42:54With his high speed camera,
0:42:54 > 0:42:58Gerard found that the bubbles do another crucial job in champagne.
0:42:58 > 0:43:02So here we have a high-speed photograph of the champagne jet
0:43:02 > 0:43:05which is injected by the bubble,
0:43:05 > 0:43:08and we also have a high-speed film of the process.
0:43:08 > 0:43:10So this is just as the bubble is just at the surface
0:43:10 > 0:43:14and it sits there for a little while, and then the top of it breaks
0:43:14 > 0:43:16and this is what happens next?
0:43:16 > 0:43:20Then the bubble cavity collapses and when it collapses, it can eject
0:43:20 > 0:43:25a tiny champagne jet up to several centimetres above the surface.
0:43:27 > 0:43:30Gerard now went one step further.
0:43:30 > 0:43:33He analysed the droplets being spat out by the bubbles.
0:43:35 > 0:43:39The molecules that carry the distinctive aromas of champagne
0:43:39 > 0:43:42were really concentrated in the droplets.
0:43:46 > 0:43:48They'd been carried by the bubble,
0:43:48 > 0:43:52somehow sticking to the bubble surface.
0:43:52 > 0:43:54Bubbles carry, obviously, CO2,
0:43:54 > 0:43:58but also aromatic molecules stuck on the bubble wall
0:43:58 > 0:44:00and when the bubble collapses,
0:44:00 > 0:44:05it ejects all those molecules above the surface.
0:44:05 > 0:44:08So this moment here right where we see the hole in the water,
0:44:08 > 0:44:11that hole is coated with these molecules, and then when
0:44:11 > 0:44:15it squirts it upwards, those molecules are going up into the air.
0:44:15 > 0:44:19- Yes.- That's beautiful. I love all this photography, it's fantastic.
0:44:19 > 0:44:21I could watch this all day.
0:44:21 > 0:44:23It's a very efficient way to transfer
0:44:23 > 0:44:25the champagne into the vapour phase
0:44:25 > 0:44:28so that you can feel it with your nose.
0:44:30 > 0:44:32What Gerard had found in the champagne
0:44:32 > 0:44:35is a property of bubbles that's really important.
0:44:36 > 0:44:39As we'll see, it's crucial to our oceans and atmosphere.
0:44:40 > 0:44:43Bubbles have the ability to transport substances
0:44:43 > 0:44:47from within a liquid to its surface and beyond.
0:44:49 > 0:44:53But why? What's going on on their surface,
0:44:53 > 0:44:55this mysterious place where gas and liquid touch,
0:44:55 > 0:44:58that means certain molecules stick to it?
0:45:01 > 0:45:05It's hard to show because these molecules are invisible,
0:45:05 > 0:45:08so I've come up with another example.
0:45:08 > 0:45:10And so what I've got down here is an experiment
0:45:10 > 0:45:12to show how bubbles can carry glitter.
0:45:12 > 0:45:15And glitter is like those aroma molecules here
0:45:15 > 0:45:18because it doesn't want to be underwater.
0:45:18 > 0:45:21If it can find a place where it's touching both the water and the air,
0:45:21 > 0:45:23it will stick there.
0:45:24 > 0:45:27Parts of these molecules are repelled by water.
0:45:27 > 0:45:30So they rush to the one place where there's no water,
0:45:30 > 0:45:33the surface of the bubble.
0:45:33 > 0:45:34So, the way that this works is,
0:45:34 > 0:45:37I'm just going to take lots and lots of photographs,
0:45:37 > 0:45:39and hopefully one or two of them at least
0:45:39 > 0:45:42will show the glitter sticking to the bubbles
0:45:42 > 0:45:44and being carried up to the surface.
0:45:44 > 0:45:46Let me set this going.
0:45:46 > 0:45:48So, I'm going to push down on the plunger,
0:45:48 > 0:45:50which is going to send air down here
0:45:50 > 0:45:53and out through the funnel where the bubbles are.
0:45:58 > 0:45:59So now I can look at the photos
0:45:59 > 0:46:02and see if I can see the bubbles carrying the glitter upwards.
0:46:02 > 0:46:07OK, so here's one. This is really, really nice.
0:46:07 > 0:46:09There's a big whoosh of bubbles have all come out together,
0:46:09 > 0:46:10a cluster of them,
0:46:10 > 0:46:13and you can clearly see that the glitter has just stuck
0:46:13 > 0:46:16to the surface of the bubbles, and there's actually
0:46:16 > 0:46:19a little cloud of glitter at the bottom where bits have fallen off
0:46:19 > 0:46:22and so they're leaving a trail of glitter behind them as well.
0:46:22 > 0:46:23So it's really obvious here
0:46:23 > 0:46:26that the bubbles are carrying glitter upwards.
0:46:29 > 0:46:31The fact that certain molecules
0:46:31 > 0:46:34can stick to bubbles is incredibly important
0:46:34 > 0:46:39and has inspired some very exciting medical research.
0:46:39 > 0:46:40What we're doing is,
0:46:40 > 0:46:44we're pumping liquid through one channel, gas through another channel,
0:46:44 > 0:46:47and where they meet we're getting a bubble.
0:46:47 > 0:46:52Scientists hope that bubbles will become magic bullets.
0:46:52 > 0:46:55It's all about the bubble surface.
0:46:55 > 0:46:58The basic idea is that instead of glitter,
0:46:58 > 0:47:01scientists will stick drugs there.
0:47:01 > 0:47:04We're actually attaching a cancer chemotherapy drug
0:47:04 > 0:47:06right onto the bubble surface.
0:47:06 > 0:47:08So, if you have a drug that's got the right properties,
0:47:08 > 0:47:11- it will stick to the surface of the bubble?- Exactly.
0:47:11 > 0:47:13It'll stick right onto the bubble surface,
0:47:13 > 0:47:15and it won't come off until we want it to come off.
0:47:15 > 0:47:17- How small are these bubbles? - Really, really tiny.
0:47:17 > 0:47:20Their equivalent size is a red blood cell,
0:47:20 > 0:47:23so that they can go through the capillaries within the body
0:47:23 > 0:47:26just that much easier. So they won't get filtered out by the lungs,
0:47:26 > 0:47:29they can go where they need to go, and we can use them
0:47:29 > 0:47:32for both diagnostic and therapeutic applications.
0:47:34 > 0:47:37But there's a second really important benefit
0:47:37 > 0:47:39to using bubbles to carry drugs.
0:47:39 > 0:47:42They can target specific places in the body.
0:47:43 > 0:47:47That means the drugs they carry don't affect the rest of the body
0:47:47 > 0:47:50and this helps avoid damaging side-effects.
0:47:55 > 0:47:59One really clever way of doing this is for the bubbles also to carry
0:47:59 > 0:48:03tiny particles of iron, so they can be directed by magnets.
0:48:05 > 0:48:09So this is a bit like a very sophisticated version of that thing
0:48:09 > 0:48:10where you get iron filings and a magnet,
0:48:10 > 0:48:12and as you pull the magnet around,
0:48:12 > 0:48:15- you can pull the iron filings around?- Yes, exactly like that,
0:48:15 > 0:48:19except this time we just see bubbles moving, as opposed to iron filings.
0:48:19 > 0:48:22So you can see at the top, there's a brown layer.
0:48:22 > 0:48:26So it's brownish because it's like rust. Rusty bubbles here.
0:48:26 > 0:48:28Rusty bubbles, but they're not bad for you in any way.
0:48:28 > 0:48:31And if you bring a magnet nearby,
0:48:31 > 0:48:33you can actually see the cloud move down,
0:48:33 > 0:48:36- and when you move it away, it turns. - They're well-behaved!
0:48:36 > 0:48:38Look at that!
0:48:41 > 0:48:45That's lovely. So, yeah, you can really push and pull them around.
0:48:45 > 0:48:47Yeah. Wherever the magnetic field is strongest,
0:48:47 > 0:48:49that's exactly where they'll head for.
0:48:49 > 0:48:51Once you've put your magnets on the person,
0:48:51 > 0:48:54how do you know whether the bubbles have stopped in the right place?
0:48:54 > 0:48:58We can see the bubbles completely under ultrasound in real time.
0:48:58 > 0:49:00That's one of the amazing things with these.
0:49:00 > 0:49:04With other drug delivery vehicles, you have no idea where they are, you hope for the best.
0:49:04 > 0:49:07With this, you actually see them stop. You can see where they are
0:49:07 > 0:49:10and then you can actually, when you remove the magnetic field, see them go away.
0:49:10 > 0:49:14- So, have you got pictures of that? That sounds fantastic.- Yes.
0:49:14 > 0:49:18So on this screen here, we have a video I recorded earlier on.
0:49:18 > 0:49:20So this is the tube, the outer wall.
0:49:20 > 0:49:22And you can see the inside completely empty
0:49:22 > 0:49:24because there's no bubbles.
0:49:24 > 0:49:26So this is like a blood vessel, a capillary vessel,
0:49:26 > 0:49:30somewhere in the body, and the cells over here and blood is running?
0:49:30 > 0:49:32Exactly, yes.
0:49:32 > 0:49:34And below here we have a magnet,
0:49:34 > 0:49:37so it's sitting a bit of a distance away, a few millimetres.
0:49:37 > 0:49:42So when I press play, we'll actually see the bubbles then flow in.
0:49:42 > 0:49:45So things are flowing through the pipe, but we can't see anything.
0:49:45 > 0:49:47And here are the bubbles.
0:49:47 > 0:49:50So you can actually see they're being drawn down towards the magnet
0:49:50 > 0:49:53and then on the bottom you see an increase in bubble concentration.
0:49:53 > 0:49:55So, here's the magnet
0:49:55 > 0:49:57- and here are all the bubbles that are attracted to it.- Yes.
0:49:57 > 0:49:59And that would be where your tumour was
0:49:59 > 0:50:02- or wherever it was that you wanted to treat?- Exactly, yeah.
0:50:03 > 0:50:05If this research works out,
0:50:05 > 0:50:10one day bubbles will carry drugs to exactly where they're needed.
0:50:10 > 0:50:12Once there, the final step
0:50:12 > 0:50:15is to persuade them to release their payload of medicine.
0:50:17 > 0:50:21And, to do that, we exploit the way bubbles respond to sound.
0:50:21 > 0:50:24When we want to use them for drug delivery, though,
0:50:24 > 0:50:25we just turn the ultrasound energy up,
0:50:25 > 0:50:29they oscillate more violently and the drug is released.
0:50:29 > 0:50:31So, that's lovely.
0:50:31 > 0:50:34You keep them calm and when it's time, you thump them with sound.
0:50:34 > 0:50:38- Oh, that was a big clap...- Well, that's actually exactly what happens.
0:50:38 > 0:50:41The bubbles expand to a large extent and then they collapse.
0:50:41 > 0:50:44It's the collapse that releases the drug and destroys the bubble.
0:50:44 > 0:50:47- Have you got video of this collapse process?- We do indeed.
0:50:47 > 0:50:52So, these are images taken at a few million frames per second.
0:50:52 > 0:50:55Sound comes in, you see the bubble expand, contract
0:50:55 > 0:50:59- and then break open and release its contents.- That's great!
0:50:59 > 0:51:01So just like you might have been injected in the arm
0:51:01 > 0:51:02with a vaccine or something,
0:51:02 > 0:51:05- this is injecting the drug into the body.- Exactly.
0:51:05 > 0:51:07Bubbles have been described as micro-syringes,
0:51:07 > 0:51:09as one of the interesting things about this jet
0:51:09 > 0:51:12is that this jet is being emitted very, very fast -
0:51:12 > 0:51:15sufficiently fast to actually puncture a cell membrane.
0:51:15 > 0:51:19- So the cell doesn't have a choice about this!- No! Provided the jet's in the right direction.
0:51:19 > 0:51:22The bubbles provide a fantastic way of encapsulating a drug,
0:51:22 > 0:51:25so the drug will have no action on the body until it's released.
0:51:25 > 0:51:28- The bubbles keep it insulated.- It's packaged.- It's packaged, exactly.
0:51:28 > 0:51:31And, more importantly, it's packaged in something we can track
0:51:31 > 0:51:32because we can track
0:51:32 > 0:51:35where the bubbles are flowing under ultrasound.
0:51:35 > 0:51:39It's great to see the direct practical benefits of bubbles.
0:51:41 > 0:51:45But now it's time to bring together all the things they can do
0:51:45 > 0:51:49and see how the tiny bubble matters to our whole planet.
0:52:12 > 0:52:16Most of the Earth's bubbles are here in the oceans.
0:52:16 > 0:52:19They're formed as breaking waves drag air underwater.
0:52:22 > 0:52:24These are the bubbles I study.
0:52:24 > 0:52:26And the reason I study them
0:52:26 > 0:52:31is that bubbles influence the way the oceans and atmosphere interact.
0:52:32 > 0:52:36And they do so in ways we're only just beginning to understand.
0:52:38 > 0:52:40I observe bubbles at sea
0:52:40 > 0:52:45and I also study them in great detail in my lab.
0:52:45 > 0:52:48Here, I can replicate the great variety of conditions
0:52:48 > 0:52:50that exist in our oceans.
0:52:50 > 0:52:54So what I can do with this tank is basically make it
0:52:54 > 0:52:57into any region of the ocean that I want. So it might be
0:52:57 > 0:53:00somewhere in the tropics with a high water temperature
0:53:00 > 0:53:01and lots of phytoplankton,
0:53:01 > 0:53:04it might be somewhere in the Southern Ocean
0:53:04 > 0:53:05where the water's very cold,
0:53:05 > 0:53:08not so much growing. And I can watch how the bubbles form
0:53:08 > 0:53:10in all those different situations in the ocean.
0:53:10 > 0:53:14And what's happening is that down at the bottom, there is a nozzle
0:53:14 > 0:53:18and it's bubbling away, so it's producing lots of bubbles
0:53:18 > 0:53:22and those bubbles rise into a region where there's two tubes
0:53:22 > 0:53:26coming down on either side and they're pumping water out.
0:53:26 > 0:53:28And so those bubbles rise up in a straight line
0:53:28 > 0:53:30and then they hit this region of turbulence
0:53:30 > 0:53:34and that's just like what happens to bubbles underneath a breaking wave.
0:53:34 > 0:53:37The reason for trying to understand bubbles is that
0:53:37 > 0:53:41out in the ocean, they play an important role in our climate.
0:53:41 > 0:53:45One part of that role especially is brilliant,
0:53:45 > 0:53:47because it's so surprising.
0:53:47 > 0:53:51When they rise to the top, and they form that foam,
0:53:51 > 0:53:53the white horses on the ocean surface,
0:53:53 > 0:53:56they are spitting tiny particles up into the atmosphere,
0:53:56 > 0:53:59and those particles can be bits of salt
0:53:59 > 0:54:02or they can be organic material that was stuck to the bubble,
0:54:02 > 0:54:05and they all get spat up into the atmosphere.
0:54:05 > 0:54:06And that matters -
0:54:06 > 0:54:10and this is one of my favourite facts in bubble science -
0:54:10 > 0:54:14those tiny particles that get spat upwards help clouds form.
0:54:14 > 0:54:18So, in a cloud in the atmosphere, all the droplets
0:54:18 > 0:54:21have at their centre a little speck of dust of some sort,
0:54:21 > 0:54:27and especially over the open ocean, clouds quite often at their centre
0:54:27 > 0:54:30have a little speck of dust that was spat out of the ocean by a bubble.
0:54:36 > 0:54:39And ocean bubbles aren't just a one-way street.
0:54:41 > 0:54:45They also help carry gases like carbon dioxide and oxygen
0:54:45 > 0:54:47down into the water.
0:54:49 > 0:54:51And so these transport mechanisms
0:54:51 > 0:54:53- the fact that the bubbles help gases move around
0:54:53 > 0:54:54and help particles move around -
0:54:54 > 0:54:57is really important for weather and climate
0:54:57 > 0:54:59because it's basically changing the chemistry
0:54:59 > 0:55:01of both the atmosphere and the ocean.
0:55:04 > 0:55:07So you can see why knowing how many bubbles there are
0:55:07 > 0:55:10and how big they are would help our climate models.
0:55:12 > 0:55:15And this is the equipment I'm using to do this.
0:55:15 > 0:55:19It records bubbles responding to sound.
0:55:19 > 0:55:22In principle, by analysing these recordings,
0:55:22 > 0:55:24I can calculate how many bubbles there are
0:55:24 > 0:55:26in a particular part of the ocean,
0:55:26 > 0:55:30and equally important, I can estimate how big they are.
0:55:30 > 0:55:33The idea behind how this works is quite simple.
0:55:36 > 0:55:37And so you can see now very clearly
0:55:37 > 0:55:40that there's this long period oscillation that's the bigger bubble
0:55:40 > 0:55:44and this has a frequency of 1.7 kilohertz. It tells me
0:55:44 > 0:55:49that the bigger bubble here was about two millimetres in radius.
0:55:49 > 0:55:53And the frequency of the other one is 16.5 kilohertz.
0:55:53 > 0:55:57That tells me that this bubble here was about a tenth of the radius,
0:55:57 > 0:56:00so this one is about 0.2 millimetres in radius.
0:56:00 > 0:56:02And you get all that information
0:56:02 > 0:56:04just from looking at that sound signal.
0:56:04 > 0:56:07And this is why sound is such a powerful technique
0:56:07 > 0:56:09to use in the ocean, because all you have to do is listen
0:56:09 > 0:56:12and you get this huge amount of information
0:56:12 > 0:56:13about what just happened.
0:56:19 > 0:56:22It's early days. There's much more work to do
0:56:22 > 0:56:27to compare the laboratory results with our measurements at sea.
0:56:30 > 0:56:33But one day I hope to be able to estimate
0:56:33 > 0:56:36not just how many bubbles form and how big they are,
0:56:36 > 0:56:40but exactly when and how they matter most.
0:56:40 > 0:56:43And then that information can be added to our climate models.
0:56:46 > 0:56:47By understanding bubbles,
0:56:47 > 0:56:50we'll have a better understanding of our planet.
0:56:56 > 0:56:59At the beginning of this film, I quoted Lord Kelvin
0:56:59 > 0:57:03talking about the physics that we can learn from bubbles.
0:57:03 > 0:57:07I hope that I've persuaded you that what you might have thought of
0:57:07 > 0:57:11as beautiful toys are enormously powerful scientific tools.
0:57:15 > 0:57:16They can help us explore nature
0:57:16 > 0:57:21at scales that are normally beyond our reach.
0:57:21 > 0:57:25They have surprising practical benefits too
0:57:25 > 0:57:29in diverse fields such as ship design and medicine.
0:57:29 > 0:57:30I hope that from now on
0:57:30 > 0:57:34you'll see bubbles in a completely different way.
0:57:37 > 0:57:41Imagine just one bubble and all the things it does while it exists,
0:57:41 > 0:57:44and then remember that underneath every breaking wave
0:57:44 > 0:57:48there are millions of bubbles and under every storm out at sea,
0:57:48 > 0:57:51there are millions of breaking waves. And on our planet right now
0:57:51 > 0:57:54there are tens or hundreds of storms going on,
0:57:54 > 0:57:56so overall on Earth right now,
0:57:56 > 0:57:59there are billions of bubbles out there.
0:57:59 > 0:58:02And the key to understanding all of what those bubbles are doing
0:58:02 > 0:58:05is understanding just one object, one little bubble.
0:58:05 > 0:58:07And the thing about bubbles is that
0:58:07 > 0:58:09once you know a little bit about them,
0:58:09 > 0:58:11you start seeing them everywhere
0:58:11 > 0:58:14and start appreciating what they're doing.
0:58:14 > 0:58:17And so understanding just one physical principle
0:58:17 > 0:58:21means that you start spotting it everywhere in your everyday world.
0:58:21 > 0:58:26So just one bit of physics can make your life so much richer.
0:58:53 > 0:58:57Subtitles by Red Bee Media Ltd