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