0:00:08 > 0:00:10The natural world is beautiful...
0:00:11 > 0:00:12..but complex.
0:00:17 > 0:00:19The skies dance with colour.
0:00:19 > 0:00:22Yay! Yes!
0:00:22 > 0:00:23Shapes form...
0:00:25 > 0:00:26..and disappear.
0:00:31 > 0:00:34But this seemingly infinite complexity
0:00:34 > 0:00:36is just a shadow of something deeper.
0:00:37 > 0:00:39The underlying laws of nature.
0:00:46 > 0:00:49The world is beautiful to look at.
0:00:49 > 0:00:51But it's even more beautiful to understand.
0:01:16 > 0:01:18Come on.
0:01:22 > 0:01:24A regular day in the snow.
0:01:26 > 0:01:29THEY PLAY AND CHATTER
0:01:29 > 0:01:31But if you look carefully,
0:01:31 > 0:01:32there's something deeper.
0:01:37 > 0:01:38This is fun!
0:01:42 > 0:01:43Every one...
0:01:44 > 0:01:48..is perfect, pretty much.
0:01:48 > 0:01:50It looks like they've been cut out of thin paper.
0:01:53 > 0:01:54I got one.
0:01:57 > 0:02:00Snowflakes are complex, intricate things.
0:02:00 > 0:02:04They are all different but there's something similar about them.
0:02:04 > 0:02:06They are beautiful,
0:02:06 > 0:02:08but there is also, I think, a deeper beauty.
0:02:08 > 0:02:11And that beauty is in an idea.
0:02:11 > 0:02:15The idea is that all the similarities and difference,
0:02:15 > 0:02:18the structure of snowflakes can be explained
0:02:18 > 0:02:21using a few simple laws of nature.
0:02:21 > 0:02:24And that idea goes to the very heart of science,
0:02:24 > 0:02:27because those laws themselves are beautiful,
0:02:27 > 0:02:29and they're universal.
0:02:29 > 0:02:32They can explain so many things,
0:02:32 > 0:02:35from snowflakes to stars.
0:02:38 > 0:02:40How do snowflakes form?
0:02:42 > 0:02:44Why are they all different,
0:02:44 > 0:02:46and yet tantalisingly similar?
0:02:50 > 0:02:52These are questions that can be asked
0:02:52 > 0:02:54about any naturally occurring structure.
0:02:58 > 0:03:00Why are beehives regular hexagons?
0:03:01 > 0:03:03Why do icebergs float?
0:03:04 > 0:03:05Why are planets spherical?
0:03:06 > 0:03:09And what has this got to do with free-diving grannies?
0:03:12 > 0:03:16The answers allow us to glimpse the underlying laws of nature
0:03:16 > 0:03:18that shape them.
0:03:22 > 0:03:25This is why, when you look at a snowflake...
0:03:28 > 0:03:30..you're peering beyond the everyday world...
0:03:31 > 0:03:34..at the deep structure of nature itself.
0:03:36 > 0:03:37The universe in a snowflake.
0:03:45 > 0:03:47Wow! I can see a star!
0:03:47 > 0:03:51It really looks like snow crystals stuck to the bubble.
0:03:51 > 0:03:54Oh! Wow!
0:03:58 > 0:04:02There's a shape that appears at all scales in the universe.
0:04:07 > 0:04:10Seen from space, the Earth is a near perfect sphere...
0:04:14 > 0:04:17..sculpted by one of the fundamental forces of nature.
0:04:25 > 0:04:26THEY SPEAK CATALAN:
0:04:44 > 0:04:47Carla and her friends are about to pit themselves
0:04:47 > 0:04:49against the force that shaped our planet.
0:05:03 > 0:05:04LOUD CHEERING
0:05:15 > 0:05:17FAINT CHEERING GROWS LOUDER
0:05:51 > 0:05:54These children are going into battle...
0:05:55 > 0:05:56..with gravity.
0:05:59 > 0:06:01HUGE CROWD CHANTING AND CHEERING
0:06:10 > 0:06:12Towns from across Catalonia...
0:06:14 > 0:06:17..have gathered to enter into a fierce competition...
0:06:20 > 0:06:23..to build a human tower as high as possible.
0:06:32 > 0:06:36Mum and Dad are here with their daughters, Mariana and Carla,
0:06:36 > 0:06:38to represent the town of Vilafranca.
0:06:42 > 0:06:44People of all ages take part,
0:06:44 > 0:06:46but it's the lightest members of the team,
0:06:46 > 0:06:48children as young as five,
0:06:48 > 0:06:51who ascend daringly to the summit.
0:07:00 > 0:07:02The family put their trust
0:07:02 > 0:07:07in the most experienced members of the team, like David Merit.
0:07:07 > 0:07:08HE SPEAKS CATALAN:
0:07:16 > 0:07:19ROAR AND CLAMOUR OF CROWD
0:07:39 > 0:07:42David feels the weight of everyone above him...
0:07:45 > 0:07:48..as gravity pulls them down to the ground.
0:07:52 > 0:07:56And he knows the secret to defying gravity is geometry.
0:08:08 > 0:08:11To support David, and eventually the kids,
0:08:11 > 0:08:14the rest of the town all push inwards
0:08:14 > 0:08:17with equal force, in all directions,
0:08:17 > 0:08:19buttressing the tower from all sides.
0:08:23 > 0:08:27And this results in the emergence of a symmetrical shape.
0:08:28 > 0:08:30A circle.
0:08:30 > 0:08:32No other shape gives the tower such strength.
0:08:44 > 0:08:47But gravity is unforgiving.
0:09:16 > 0:09:18CROWD CHANTING
0:09:20 > 0:09:24And that's a worry if your child is climbing to the top.
0:10:59 > 0:11:02It's clear that the force of gravity is unrelenting.
0:11:07 > 0:11:12The collapsing towers are shadows of the process that shaped our planet.
0:11:17 > 0:11:20These people aren't just falling towards the ground.
0:11:23 > 0:11:25They're falling towards the centre of the Earth.
0:11:26 > 0:11:29And the Earth's gravity pulls everything down.
0:11:31 > 0:11:33From people to snowflakes...
0:11:38 > 0:11:40..to the very rock that the Earth is made of.
0:11:42 > 0:11:45And this is ultimately why the Earth is spherical.
0:11:47 > 0:11:51So why does gravity sculpt things into spheres?
0:11:51 > 0:11:55Well, the first thing to say is that it doesn't, necessarily.
0:11:57 > 0:11:59If I pick up a snowball...
0:12:01 > 0:12:03..it's not spherical. Kind of an irregular shape.
0:12:05 > 0:12:08But if I apply pressure to it,
0:12:08 > 0:12:12squash it, evenly, in all directions...
0:12:13 > 0:12:16..then I can turn that into a sphere.
0:12:16 > 0:12:19And that is what's happening with gravity.
0:12:19 > 0:12:21As I start adding mass to it,
0:12:21 > 0:12:25that gravitational pull becomes bigger,
0:12:25 > 0:12:27so I'll get to a point where this snowball,
0:12:27 > 0:12:29if I kept adding mass to it,
0:12:29 > 0:12:33would be so massive that the gravitational pull on its surface
0:12:33 > 0:12:38would be so strong that it would start to squash the material
0:12:38 > 0:12:39out of which it is made.
0:12:39 > 0:12:41In this case, snow,
0:12:41 > 0:12:43or in the case of a planet or moon, the rock.
0:12:44 > 0:12:50That pressure exerts on the surface equally in all directions,
0:12:50 > 0:12:54because gravity works equally in all directions.
0:12:55 > 0:12:56You could ask the question,
0:12:56 > 0:13:00how much matter do I need for gravity to get strong enough
0:13:00 > 0:13:03to start overcoming the strength of rock,
0:13:03 > 0:13:05and sculpting things into spheres?
0:13:05 > 0:13:09Well, that minimum size has got a name.
0:13:09 > 0:13:11It's a brilliant name. It is called the potato radius.
0:13:11 > 0:13:13You can see why.
0:13:13 > 0:13:17Because things that are too small for gravity to be strong enough
0:13:17 > 0:13:20to sculpt them look like misshapen potatoes.
0:13:23 > 0:13:26The great thing is you don't even need to imagine it.
0:13:27 > 0:13:29You can calculate it.
0:13:29 > 0:13:32I did that this morning, and I got an answer, just roughly,
0:13:32 > 0:13:34of between 100 and 200km.
0:13:34 > 0:13:36The brilliant thing,
0:13:36 > 0:13:39the most beautiful thing is if you look up into space,
0:13:39 > 0:13:42and look at the moons of Mars and Saturn and Jupiter,
0:13:42 > 0:13:44and objects out there in the solar system,
0:13:44 > 0:13:47you'll find that, roughly speaking,
0:13:47 > 0:13:50if their radius is bigger than about 200km,
0:13:50 > 0:13:52they're beautiful spheres,
0:13:52 > 0:13:55and if their radius is less than about 200km,
0:13:55 > 0:13:58they look more like misshapen potatoes.
0:13:58 > 0:14:00So you can calculate it.
0:14:04 > 0:14:07If you're small, spheres don't come easily.
0:14:11 > 0:14:14Even asteroids or moons don't quite manage it.
0:14:14 > 0:14:18The potato shape might be as close as you can get.
0:14:23 > 0:14:27But when you're the size of a planet, spheres come naturally.
0:14:35 > 0:14:374.5 billion years ago,
0:14:37 > 0:14:41rocks circling the sun began sticking together,
0:14:41 > 0:14:45until they had sufficient mass for gravity to really get to work...
0:14:46 > 0:14:50..turning potato shapes into one very important sphere,
0:14:50 > 0:14:52suspended in space.
0:14:59 > 0:15:03A universal law sculpted the familiar, elegant,
0:15:03 > 0:15:04symmetrical shape of our planet.
0:15:12 > 0:15:14But closer to the surface,
0:15:14 > 0:15:18it's littered with endless shapes and forms.
0:15:22 > 0:15:26And in every one of these naturally occurring structures,
0:15:26 > 0:15:30there are a simple, underlying laws waiting to be glimpsed.
0:15:36 > 0:15:37Here in the Himalayas,
0:15:37 > 0:15:42there's a shape that's a shadow of a fundamental mathematical law.
0:15:45 > 0:15:47It's guarded by the Himalayan honeybee.
0:15:49 > 0:15:50CHAOTIC DRONING BUZZ
0:15:51 > 0:15:54The largest species of honeybee on the planet.
0:15:56 > 0:16:01And collecting honey from under their watchful compound eyes
0:16:01 > 0:16:03is one of the most dangerous jobs you could imagine.
0:16:11 > 0:16:13THEY SPEAK NEPALESE
0:16:24 > 0:16:27And today is the first time for one of the young villagers.
0:16:28 > 0:16:31Min and his nephew Hira will be the ones leading the hunt
0:16:31 > 0:16:33for the precious honey.
0:16:33 > 0:16:36It's prized for its medicinal properties,
0:16:36 > 0:16:37and sells for a high price.
0:16:48 > 0:16:49CHATTERING AND LAUGHTER
0:16:52 > 0:16:55Hidden beneath the seething mass of bodies
0:16:55 > 0:16:58sits a network of exquisitely engineered hexagons.
0:17:03 > 0:17:06The bees appear to be master builders,
0:17:06 > 0:17:10performing structural calculations with architectural precision.
0:17:24 > 0:17:27The bees benefit from a hidden mathematical law
0:17:27 > 0:17:32that explains why they build hexagons to store their honey.
0:17:32 > 0:17:35And twice a year, the Gurung people head into the mountains
0:17:35 > 0:17:37to exploit the bees' secret.
0:17:42 > 0:17:44Because it's Hira's first time,
0:17:44 > 0:17:47this trip will be particularly challenging.
0:17:53 > 0:17:54HE GRUNTS
0:17:54 > 0:17:56THEY CHATTER IN NEPALESE
0:18:20 > 0:18:22BUZZING GROWS LOUDER
0:18:31 > 0:18:34The bees make their hives as inaccessible as possible
0:18:34 > 0:18:36to protect them from predators.
0:19:10 > 0:19:12The hives the bees are defending
0:19:12 > 0:19:17contain a vivid, visible solution to a deep mathematical problem,
0:19:17 > 0:19:19and a very practical one.
0:19:21 > 0:19:24They need to store honey to sustain their colony
0:19:24 > 0:19:25through the long winter months.
0:19:26 > 0:19:28They build their hives out of wax.
0:19:30 > 0:19:33But for every gram of wax a bee produces,
0:19:33 > 0:19:37it will have to consume more than six grams of honey.
0:19:40 > 0:19:42So they benefit from building efficiently,
0:19:42 > 0:19:45using as little wax as possible.
0:19:59 > 0:20:02THEY SHOUT DOWN
0:20:15 > 0:20:16HE SHOUTS
0:20:39 > 0:20:43Each sting is like a hypodermic needle.
0:20:44 > 0:20:46After the bees sting, they die.
0:20:49 > 0:20:53The ultimate sacrifice to guard the hexagons
0:20:53 > 0:20:54and the honey they hold.
0:21:41 > 0:21:43THEY SHOUT OUT HAPPILY
0:22:07 > 0:22:09THEY CHATTER EXCITEDLY
0:22:15 > 0:22:16For Hira, this is all about
0:22:16 > 0:22:20keeping the Gurung tradition of honey hunting alive.
0:22:23 > 0:22:26And the hexagon is at the heart of it all.
0:22:45 > 0:22:48So why DO bees build hexagonal honeycombs?
0:22:51 > 0:22:54Well, that is, in fact, a very good question.
0:22:54 > 0:22:55It's actually a mathematical question.
0:22:58 > 0:22:59The problem is,
0:22:59 > 0:23:05how do I divide up a volume into shapes of equal size
0:23:05 > 0:23:07using the minimum amount of stuff?
0:23:08 > 0:23:10Now, why does that matter to a bee?
0:23:10 > 0:23:12Because that stuff is wax,
0:23:12 > 0:23:15and wax is extremely valuable to the bees.
0:23:15 > 0:23:18So, what shape should it be?
0:23:18 > 0:23:20Should it be squares?
0:23:20 > 0:23:22Or should it be triangles?
0:23:22 > 0:23:24You can see it can't be circles
0:23:24 > 0:23:26because circles, when you pack them together,
0:23:26 > 0:23:28leave gaps, so they're not very efficient.
0:23:28 > 0:23:32Or could it be that hexagons are the most efficient?
0:23:32 > 0:23:36Well, that is actually a simple sounding question,
0:23:36 > 0:23:38with a very complicated answer.
0:23:38 > 0:23:41It's one of the oldest questions in mathematics.
0:23:41 > 0:23:42It's got a name, actually.
0:23:42 > 0:23:44It's called the honeycomb conjecture.
0:23:44 > 0:23:49Mathematicians have worked on it for thousands and thousands of years,
0:23:49 > 0:23:53and it's only recently that the honeycomb conjecture was proved.
0:23:54 > 0:23:55Here is one of the proofs.
0:23:56 > 0:23:58A huge paper.
0:23:59 > 0:24:02Pages and pages of complex mathematics...
0:24:03 > 0:24:07..and it turns out that the hexagon IS the most efficient shape.
0:24:07 > 0:24:11The bees knew what human mathematicians didn't know
0:24:11 > 0:24:13for thousands of years.
0:24:13 > 0:24:16Actually, I'm using "know" in quite a loose sense, there.
0:24:16 > 0:24:19There's still a great deal of debate amongst biologists
0:24:19 > 0:24:22as to how the bees actually do it.
0:24:22 > 0:24:26Do they build hexagons from scratch
0:24:26 > 0:24:29using some kind of instinctive behaviour?
0:24:29 > 0:24:31Or do they in fact build a simpler shape?
0:24:31 > 0:24:35Perhaps circles, and then, because the wax heats up, it can deform,
0:24:35 > 0:24:37and the laws of physics themselves
0:24:37 > 0:24:40change the circles into hexagons?
0:24:40 > 0:24:42That's still not agreed upon,
0:24:42 > 0:24:46but what is agreed upon by the mathematicians and the bees
0:24:46 > 0:24:49is the hexagon is the most efficient shape.
0:24:49 > 0:24:51That just shows you. It's a beautiful thing.
0:24:51 > 0:24:54Mathematics is the universal language,
0:24:54 > 0:24:57and when you look at a perfect honeycomb,
0:24:57 > 0:25:01you see a shadow of that language of mathematics
0:25:01 > 0:25:04made real by bees.
0:25:10 > 0:25:13Perfect shapes reveal simple laws.
0:25:19 > 0:25:21Whether it's spherical planets,
0:25:21 > 0:25:23sculpted by gravity...
0:25:27 > 0:25:29..pulling us to the centre of the Earth...
0:25:33 > 0:25:38..or the mathematically refined efficiency of hexagonal honeycombs.
0:25:41 > 0:25:45Simple laws underpin the shapes we can see.
0:25:46 > 0:25:47And they're universal.
0:25:51 > 0:25:53But the action of these simple laws
0:25:53 > 0:25:56seems at odds with the complex shapes of life.
0:26:09 > 0:26:11These shallow springs are home to
0:26:11 > 0:26:14one of nature's seemingly less elegant shapes.
0:26:24 > 0:26:25The manatee.
0:26:26 > 0:26:28Like all marine animals,
0:26:28 > 0:26:30they're free from the effects of gravity.
0:26:30 > 0:26:33No need for strong bones to support their weight.
0:26:35 > 0:26:38But they don't have complete freedom from the laws of physics.
0:26:38 > 0:26:40RADIO BLARES
0:26:43 > 0:26:45It's winter,
0:26:45 > 0:26:48and if the water temperature here drops below 20 degrees...
0:26:48 > 0:26:51- RADIO:- Due to cool temperatures Friday morning...
0:26:51 > 0:26:53..for the manatee, it's deadly.
0:26:54 > 0:26:57..very dangerous, in search of warmer aquatic environments.
0:26:59 > 0:27:02Manatees, like this female, are vegetarians.
0:27:04 > 0:27:08Basically, she is a 10ft long aquatic cow with no legs.
0:27:09 > 0:27:14To stay warm, she has to consume up to 50kg of leaves and seagrass
0:27:14 > 0:27:15every day.
0:27:16 > 0:27:19And the females here are eating for others, too.
0:27:19 > 0:27:22This one is suckling two young calves.
0:27:22 > 0:27:25And the weather is only getting colder.
0:27:35 > 0:27:36Looking good.
0:27:41 > 0:27:42There's Doug.
0:27:42 > 0:27:45Doug likes it up here now.
0:27:45 > 0:27:48Researcher Wayne Hartley is doing this morning's headcount,
0:27:48 > 0:27:50part of a manatee census.
0:27:55 > 0:27:57It's a special thing to come to work...
0:27:59 > 0:28:01..come down in the morning,
0:28:01 > 0:28:02and it's quiet.
0:28:03 > 0:28:05The steam's coming off the water.
0:28:10 > 0:28:14I can hear the manatees out there breathing. It's just "whoosh".
0:28:16 > 0:28:18And they are so peaceful.
0:28:18 > 0:28:20They are so calm.
0:28:22 > 0:28:26Just watching manatees has got to be good for your blood pressure,
0:28:26 > 0:28:28and anything else that may ail you.
0:28:38 > 0:28:41Biologist Amy Tegg is working with Wayne
0:28:41 > 0:28:43to do a health check on the families.
0:28:45 > 0:28:48Well, he's just sort of hanging around, checking things out.
0:28:48 > 0:28:52Manatees are very docile, gentle creatures.
0:28:53 > 0:28:55But they are very curious.
0:28:55 > 0:28:57Anything new in their environment,
0:28:57 > 0:28:59they often like to come check out.
0:28:59 > 0:29:01So he's probably just checking me out.
0:29:01 > 0:29:03MANATEE SQUEAKS GENTLY
0:29:03 > 0:29:05Yeah, he's just chewing on my flipper.
0:29:06 > 0:29:07Got 23.5 degrees Celsius.
0:29:09 > 0:29:12Manatee families are drawn in from colder waters,
0:29:12 > 0:29:13because this is a hot spring.
0:29:14 > 0:29:17And some make it just in time.
0:29:17 > 0:29:19He is severely cold stressed.
0:29:21 > 0:29:23With the cold stress, they don't eat.
0:29:24 > 0:29:26Their immune system shuts down.
0:29:27 > 0:29:30They're here to keep themselves alive in the winter.
0:29:30 > 0:29:34They really require warm water.
0:29:38 > 0:29:43It might look like these animals keep warm using blubber, like seals.
0:29:44 > 0:29:45But they're not fat.
0:29:45 > 0:29:47They're round.
0:29:48 > 0:29:49In terms of pure physics,
0:29:49 > 0:29:52the best way to stay warm is to be a sphere.
0:29:57 > 0:30:01It has the smallest surface area to volume ratio of any shape.
0:30:02 > 0:30:04Less area for heat to escape from.
0:30:06 > 0:30:09A beautiful example of the naturally occurring shape
0:30:09 > 0:30:12reflecting a deeper mathematical law.
0:30:13 > 0:30:16The manatee could well be the most spherical mammal on earth.
0:30:17 > 0:30:19What a wonderful thing to be.
0:30:25 > 0:30:26Sorry, their breath stinks.
0:30:26 > 0:30:28SHE LAUGHS
0:30:28 > 0:30:31To me, it smells like the inside of a hot truck tyre.
0:30:31 > 0:30:33SHE LAUGHS
0:30:36 > 0:30:38But, of course, they're not perfect spheres.
0:30:40 > 0:30:44There are many other competing factors that determine their shape.
0:30:44 > 0:30:51Like all animals, they have to live, breathe, eat and move.
0:30:54 > 0:30:56The manatee's natural habitat is shrinking.
0:30:57 > 0:30:59And they need to find warmth elsewhere.
0:31:03 > 0:31:06This power station helps provide energy
0:31:06 > 0:31:08for around nine million people,
0:31:08 > 0:31:11and in the process warms the water
0:31:11 > 0:31:14that keeps over half of Florida's manatees alive through the winter.
0:31:19 > 0:31:22The same families that Wayne and Amy study
0:31:22 > 0:31:25can end up here - over 300km away...
0:31:27 > 0:31:28..where their mothers and calves
0:31:28 > 0:31:30can hold on to as much heat as possible...
0:31:32 > 0:31:33..because of their round bodies.
0:31:36 > 0:31:39To a physicist, the perfect shape for a manatee
0:31:39 > 0:31:42would be a symmetrical sphere.
0:31:42 > 0:31:44But biology complicates things.
0:31:46 > 0:31:48Manatees can't just bob around
0:31:48 > 0:31:50waiting for food or warmth to come to them.
0:31:51 > 0:31:54They need fins and a tail to move around.
0:31:56 > 0:31:59Whether that is to a hot spring or to a power station.
0:32:11 > 0:32:16The forces of nature sculpt and restrict the shapes of all things,
0:32:16 > 0:32:20the inanimate, like pebbles or rocks or cliffs,
0:32:20 > 0:32:22or living things.
0:32:25 > 0:32:29But of course, basic physics is not the only force shaping life.
0:32:33 > 0:32:35Evolution, by natural selection,
0:32:35 > 0:32:38moulds living things over time
0:32:38 > 0:32:40in response to their environment
0:32:40 > 0:32:42and their interaction with other life forms.
0:32:46 > 0:32:49And it's had billions of years to do it.
0:32:51 > 0:32:55So you can't understand the shape of living things
0:32:55 > 0:32:58without understanding their evolutionary history.
0:33:10 > 0:33:14KOREAN WOMAN OVER TANNOY:
0:33:31 > 0:33:34We are all the product of our experiences,
0:33:34 > 0:33:37our history, our culture.
0:33:37 > 0:33:40Our lives make an indelible impression
0:33:40 > 0:33:42and make us all different.
0:33:47 > 0:33:49But we are also all similar.
0:33:50 > 0:33:53Not just to each other as human beings,
0:33:53 > 0:33:56but to countless other animals on Earth.
0:33:56 > 0:33:59We are obviously related.
0:34:03 > 0:34:07Most obviously through the symmetry of our bodies.
0:34:29 > 0:34:31Mrs Chae and Miss Kim
0:34:31 > 0:34:33are haenyeo, are women of the sea.
0:34:33 > 0:34:37They've grown up collecting seafood along these shores.
0:34:38 > 0:34:40And they still do.
0:34:53 > 0:34:55The haenyeo are part of a dying tradition.
0:34:55 > 0:34:58Not many youngsters are interested any more.
0:34:59 > 0:35:03It's hard work, especially if you're in your 70s.
0:35:03 > 0:35:05IN KOREAN:
0:35:31 > 0:35:35Right now, the women are catching conch, or sea snails.
0:35:38 > 0:35:40It's a crucial time of year,
0:35:40 > 0:35:43when they have a chance to make the most money.
0:35:55 > 0:35:58The tradition of freediving for food
0:35:58 > 0:36:01is part of these women's cultural history.
0:36:01 > 0:36:04But the details of the human form itself,
0:36:04 > 0:36:09in particular, its symmetry that allows them to dive, swim and hunt,
0:36:09 > 0:36:11is part of their evolutionary history.
0:36:16 > 0:36:19IN KOREAN:
0:36:50 > 0:36:53For Mrs Chae and Miss Kim,
0:36:53 > 0:36:55this is all about the search for food.
0:36:59 > 0:37:02And that's where the symmetrical structure of their bodies comes in.
0:37:03 > 0:37:06A blueprint that started out here in the oceans
0:37:06 > 0:37:08hundreds of millions of years ago.
0:37:12 > 0:37:15Very few animals have steered clear of it.
0:37:38 > 0:37:43Life is, and always has been, a competition.
0:37:43 > 0:37:45In a free-floating world,
0:37:45 > 0:37:49life grew to adopt different types of symmetry to get what it needed.
0:37:52 > 0:37:56Some animals became round, or radially symmetric,
0:37:56 > 0:37:59organising their sensory organs around a central axis.
0:38:00 > 0:38:02Rather than chasing down food,
0:38:02 > 0:38:05they waited for food to come to them.
0:38:06 > 0:38:09But in order to really go after prey,
0:38:09 > 0:38:12you need to leave that strategy behind.
0:38:15 > 0:38:17You need to be divided down the middle.
0:38:18 > 0:38:22That gives you two sides - bilateral symmetry.
0:38:22 > 0:38:24Basically, you have a left and a right.
0:38:28 > 0:38:33And you can build on this plan with arms to grab and search
0:38:33 > 0:38:35and a head and a tail.
0:38:36 > 0:38:39All this means you can orientate yourself
0:38:39 > 0:38:42and really target your prey.
0:38:50 > 0:38:55This body plan has been selected for over hundreds of millions of years.
0:38:56 > 0:38:58It confers a survival advantage.
0:38:59 > 0:39:02And it turns out that all animals with brains
0:39:02 > 0:39:04are bilaterally symmetrical.
0:39:09 > 0:39:12Bilateral symmetry provided the agility
0:39:12 > 0:39:16that drove a spiral of cunning and fast predators
0:39:16 > 0:39:17and skittish, speedy prey.
0:39:48 > 0:39:53The beautiful symmetry of the human body, which we all take for granted,
0:39:53 > 0:39:57is the product of a sweeping, majestic story...
0:39:58 > 0:40:01..stretching back to some of the earliest life on Earth.
0:40:11 > 0:40:15So we can understand the symmetry of organisms
0:40:15 > 0:40:17by understanding their history.
0:40:20 > 0:40:22You're essentially seeing
0:40:22 > 0:40:24the results of evolution by natural selection
0:40:24 > 0:40:28over hundreds of millions, even billions of years.
0:40:32 > 0:40:35But how do you understand
0:40:35 > 0:40:38the structure and symmetry of a snowflake?
0:40:38 > 0:40:41There's no natural selection here.
0:40:41 > 0:40:46There's no DNA to record and reproduce information.
0:40:46 > 0:40:51These things arise spontaneously from basic laws of physics.
0:40:57 > 0:41:02The intricate beauty of a snowflake is at first sight baffling,
0:41:02 > 0:41:04given the simplicity of their story.
0:41:05 > 0:41:07But in fact, it's a gift.
0:41:09 > 0:41:11A gift of almost nothing.
0:41:11 > 0:41:13One frozen moment
0:41:13 > 0:41:16that can reveal how the underlying laws of nature
0:41:16 > 0:41:19can lead to seemingly infinite complexity.
0:41:24 > 0:41:27Because snowflakes form in minutes
0:41:27 > 0:41:30and are made out of a single ingredient,
0:41:30 > 0:41:32with strange properties
0:41:32 > 0:41:36that give rise to a vast array of naturally occurring forms
0:41:36 > 0:41:39of all shapes, sizes and behaviours.
0:41:43 > 0:41:45Ice.
0:41:53 > 0:41:56- MAN:- You know, it's so mystical when you leave in the morning in the fog.
0:41:57 > 0:41:59You're just looking around...
0:42:01 > 0:42:04..and then you see these shapes that come out of the fog.
0:42:13 > 0:42:16- MAN:- They are big, big, heavy objects.
0:42:16 > 0:42:20Far bigger than anything that we've created floating on the sea.
0:42:40 > 0:42:42We've got to remember,
0:42:42 > 0:42:44it was an iceberg that sailed past Newfoundland
0:42:44 > 0:42:46which ended up sinking the Titanic.
0:42:49 > 0:42:52Doug Allen is here because it's iceberg season.
0:42:55 > 0:42:57He's part of a scientific expedition.
0:42:57 > 0:43:01Every summer, thousands of icebergs float south from the Arctic
0:43:01 > 0:43:03into the shipping lanes and oilfields
0:43:03 > 0:43:06off the coast of Newfoundland.
0:43:08 > 0:43:09This team are here to help protect
0:43:09 > 0:43:12those multibillion dollar industries,
0:43:12 > 0:43:16by trying to understand more about where the icebergs are heading.
0:43:18 > 0:43:21The man leading the expedition is Neil Riggs.
0:43:21 > 0:43:23So you put it back in the water again, OK.
0:43:23 > 0:43:25And if we lose control,
0:43:25 > 0:43:26then we take it in and we secure it.
0:43:26 > 0:43:28And if that goes nowhere, we go home.
0:43:31 > 0:43:34The big problem with icebergs is simple...
0:43:34 > 0:43:36They float.
0:43:43 > 0:43:48- NEIL RIGGS:- Iceberg ice reflects radar 69 times less effectively
0:43:48 > 0:43:50than a ship with the same cross-sectional area.
0:43:52 > 0:43:56Yes, we've got some here.
0:43:56 > 0:43:58So you could be sailing along
0:43:58 > 0:44:00and doing very good seamanship, looking at your radar
0:44:00 > 0:44:03and there's the thing all of a sudden and you're upon it
0:44:03 > 0:44:06and it's still a massive piece of ice relative to your ship.
0:44:06 > 0:44:08So it can make a nice little hole.
0:44:10 > 0:44:13The team will have to understand the influence
0:44:13 > 0:44:15of a large number of variables
0:44:15 > 0:44:18if they are to distinguish between harmless icebergs
0:44:18 > 0:44:20and dangerous ones.
0:44:20 > 0:44:22- DOUG ALLEN: - It's a complicated jigsaw.
0:44:22 > 0:44:24You could think of it as a crime scene
0:44:24 > 0:44:26where you have the forensic people go in
0:44:26 > 0:44:28and they pick up little bits of clues,
0:44:28 > 0:44:30and together you make a bigger picture.
0:44:31 > 0:44:35What I'm doing is just adding my little piece to the overall picture
0:44:35 > 0:44:40and hopefully helping their mathematical models to be more real.
0:44:41 > 0:44:44Doug is a specialist cold water diver.
0:44:44 > 0:44:48It's his job to photograph the underside of the icebergs.
0:44:48 > 0:44:51We'll go over to some of those smaller pieces.
0:44:51 > 0:44:53- OK.- OK.
0:44:53 > 0:44:56Yes, Captain Manning, we are OK to put the diver...
0:44:56 > 0:44:59Rick Stanley is looking after safety.
0:45:04 > 0:45:06Who knows what's going to happen?
0:45:06 > 0:45:08There's so much pressure in this ice
0:45:08 > 0:45:12that it blows, it explodes.
0:45:12 > 0:45:14But there's pressure in there
0:45:14 > 0:45:16that can blow a piece of iceberg off the ice
0:45:16 > 0:45:18probably 15 or 20 feet.
0:45:18 > 0:45:22LOUD BANG AND CRASHING
0:45:25 > 0:45:28- DOUG ALLEN:- And we were just pottering around and suddenly,
0:45:28 > 0:45:31with no warning at all, the whole thing split in half
0:45:31 > 0:45:34and it was almost like it was all falling into each other.
0:45:42 > 0:45:44This might be a bit unstable.
0:45:44 > 0:45:46This is a huge berg.
0:45:46 > 0:45:49I'd rather dive around one that wasn't falling apart.
0:45:49 > 0:45:51Yeah.
0:45:54 > 0:45:57These giant frozen mountains
0:45:57 > 0:46:00are born from the most innocent beginnings.
0:46:05 > 0:46:06Snowflakes.
0:46:09 > 0:46:11Over thousands of years,
0:46:11 > 0:46:13they compress to form glaciers,
0:46:13 > 0:46:17that then break off to form icebergs.
0:46:17 > 0:46:20An average one weighs 200,000 tonnes.
0:46:22 > 0:46:24And that, give or take,
0:46:24 > 0:46:27is around 100 trillion snowflakes
0:46:27 > 0:46:30that form the structures that the expedition is trying to model,
0:46:30 > 0:46:33using a combination of sonar robots
0:46:33 > 0:46:35and Doug's first-hand observations.
0:46:37 > 0:46:40I'll basically have a good look at one side of the berg
0:46:40 > 0:46:43between the surface and 30 metres.
0:46:43 > 0:46:45Tell them what I saw,
0:46:45 > 0:46:47and it will mean that they can interpret the sonar
0:46:47 > 0:46:48the data that comes back.
0:46:48 > 0:46:51They will get a better idea of it, if I've seen it for myself.
0:47:20 > 0:47:24- DOUG ALLEN:- It's quite eerie going down the side of the iceberg.
0:47:25 > 0:47:29You're going down into the darkness, into the blue, into the green.
0:47:36 > 0:47:40And very occasionally there will be this really loud thud,
0:47:40 > 0:47:43just like someone had hit you with the flat of their hand
0:47:43 > 0:47:45in the centre of your chest...
0:47:46 > 0:47:49..where the iceberg is banging on the bottom.
0:47:57 > 0:47:59You really don't want to go too far down
0:47:59 > 0:48:01because there is a real danger
0:48:01 > 0:48:04of being squished by the iceberg underneath.
0:48:08 > 0:48:11Well, you always worry when divers are in the water.
0:48:11 > 0:48:13But iceberg diving,
0:48:13 > 0:48:17there's even more of that anticipation and excitement
0:48:17 > 0:48:19that goes on in the lower part of your belly.
0:48:28 > 0:48:32So you swim in and you begin to see the details.
0:48:32 > 0:48:36you begin to realise that this is not a flat wall of ice
0:48:36 > 0:48:38going into the depths.
0:48:38 > 0:48:40This has tiny little dimples on it.
0:48:40 > 0:48:43It almost looks like a giant golf ball.
0:48:49 > 0:48:52These features are added to the models,
0:48:52 > 0:48:55to understand how they affect the way the icebergs float
0:48:55 > 0:48:59and travel over long distances and into the shipping lanes.
0:49:01 > 0:49:04It's good to contribute to science at a basic level like this.
0:49:04 > 0:49:06When the science is still developing,
0:49:06 > 0:49:09to come in, take some shots, which helps scientists,
0:49:09 > 0:49:10that's really useful.
0:49:16 > 0:49:18For all their unpredictability,
0:49:18 > 0:49:22there is regularity in the behaviour of icebergs...
0:49:24 > 0:49:28..if you look carefully and ask the right questions.
0:49:29 > 0:49:32Which is what science is all about.
0:49:38 > 0:49:40And the simplest question of all
0:49:40 > 0:49:43is about the most obvious part of their behaviour.
0:49:46 > 0:49:48Why does ice float?
0:49:49 > 0:49:51That's not a naive question,
0:49:51 > 0:49:55because no other commonly occurring solid floats on its own liquid.
0:49:58 > 0:50:02The answer lies in the structure of the water molecule itself.
0:50:03 > 0:50:05Think of what a molecule is.
0:50:05 > 0:50:07Take a water molecule, for example.
0:50:07 > 0:50:11It's two hydrogen atoms stuck to an oxygen atom.
0:50:11 > 0:50:17That's two hydrogen nuclei, which have a positive electric charge,
0:50:17 > 0:50:21sticking to an oxygen nucleus, which has a positive electric charge.
0:50:21 > 0:50:25And they're surrounded by negatively-charged electrons.
0:50:25 > 0:50:27That's what sticks the atoms together.
0:50:27 > 0:50:30The negatively-charged electrons
0:50:30 > 0:50:33tend to cluster around the oxygen nucleus,
0:50:33 > 0:50:40leaving those two legs of hydrogen slightly positively charged.
0:50:40 > 0:50:43That means that those positive charges
0:50:43 > 0:50:48can attract other negatively-charged ends of other water molecules.
0:50:48 > 0:50:54So an oxygen can come and orientate itself and bond to that leg.
0:50:54 > 0:50:57On the other side, another oxygen from another water molecule
0:50:57 > 0:51:01will be attracted to the positive charge and bond to that leg.
0:51:01 > 0:51:04On the top, you get a hydrogen bonding to that leg.
0:51:04 > 0:51:07So you can see you build up a structure,
0:51:07 > 0:51:09an open crystal structure.
0:51:09 > 0:51:12A shape which is actually hexagonal.
0:51:12 > 0:51:16And it's that property, that open structure,
0:51:16 > 0:51:19which is a reflection of the underlying structure
0:51:19 > 0:51:21of the water molecule itself
0:51:21 > 0:51:27that leads to the solid ice being less dense than the liquid.
0:51:27 > 0:51:34And that is why ice cubes and icebergs float on liquid water.
0:51:38 > 0:51:40The hexagonal structure of ice
0:51:40 > 0:51:44is a shadow of the forces of nature that hold molecules together.
0:51:48 > 0:51:51Forces that shape every molecule of water...
0:51:53 > 0:51:57..and that create a sixfold symmetry of snowflakes.
0:52:02 > 0:52:05You can tell they're all the same thing.
0:52:05 > 0:52:06They're all six-sided.
0:52:08 > 0:52:11And yet, you can also see just by eye,
0:52:11 > 0:52:12that every one is different.
0:52:12 > 0:52:15Some radically different.
0:52:15 > 0:52:20It's very difficult to imagine how all this beauty and complexity
0:52:20 > 0:52:25could emerge spontaneously from a few simple laws of nature.
0:52:30 > 0:52:33As snowflakes fall through the sky,
0:52:33 > 0:52:36they form and grow around a symmetrical framework.
0:52:38 > 0:52:42So if you start with an ice crystal
0:52:42 > 0:52:45and some part of it has got a flat bit,
0:52:45 > 0:52:47part of the hexagonal if you like,
0:52:47 > 0:52:49and some bits a bit rough,
0:52:49 > 0:52:52then water molecules are more likely to bind
0:52:52 > 0:52:55to the rough bits than the flat bits.
0:52:55 > 0:52:57There are basically more ways for them,
0:52:57 > 0:52:59more sites for them to stick to.
0:52:59 > 0:53:01So that means that the rough bits
0:53:01 > 0:53:04will accumulate more molecules than the flat bit
0:53:04 > 0:53:07and it'll build up faster until it gets flat.
0:53:07 > 0:53:09And then it'll slow down.
0:53:09 > 0:53:11So there's a tendency
0:53:11 > 0:53:15for the underlying structure of the ice crystals themselves
0:53:15 > 0:53:18to get echoed into bigger and bigger units.
0:53:20 > 0:53:22Then there's a second process called branching,
0:53:22 > 0:53:24or the branch instability.
0:53:24 > 0:53:26That happens when the snowflake
0:53:26 > 0:53:30goes into a particularly humid region in a cloud.
0:53:30 > 0:53:33So that's a region where there are lots of water molecules available.
0:53:33 > 0:53:37So you get a little bump on the flat surface.
0:53:37 > 0:53:42That bump is more likely to have water molecules bind to it,
0:53:42 > 0:53:45it's got more binding sites, if you like.
0:53:45 > 0:53:48So it will grow quickly if there are lots of water molecules available.
0:53:48 > 0:53:51So it will grow into a spike
0:53:51 > 0:53:54and then other bumps can appear and they'll grow into spikes.
0:53:54 > 0:53:57So that's how you get that star-like,
0:53:57 > 0:53:59sharp structures on snowflakes.
0:54:00 > 0:54:05But then the snowflake drifts back into a region that's less humid,
0:54:05 > 0:54:07so there are less water molecules available.
0:54:07 > 0:54:10Then the faceting takes over again
0:54:10 > 0:54:14and smooth edges, hexagonal structures start to form.
0:54:14 > 0:54:16Then it goes into a humid region
0:54:16 > 0:54:18and the branching takes over and you get the branches.
0:54:27 > 0:54:30It's a wonderfully complex and intricate process.
0:54:30 > 0:54:33And the thing I find most beautiful about it
0:54:33 > 0:54:35is that when you look at a snowflake,
0:54:35 > 0:54:38then you can read its entire history,
0:54:38 > 0:54:41you can see its history made solid.
0:54:43 > 0:54:48Every individual snowflake has a different history.
0:54:48 > 0:54:51Every snowflake followed a slightly different path
0:54:51 > 0:54:54through the clouds and onto the ground.
0:54:54 > 0:54:59And that means every snowflake grew in a subtly different way.
0:54:59 > 0:55:03And that's why no two snowflakes are ever alike,
0:55:03 > 0:55:08because no two paths through time are ever alike.
0:55:15 > 0:55:18When you look at a snowflake, you see history...
0:55:19 > 0:55:25..and the deep structure of nature condensed into a frozen moment.
0:55:27 > 0:55:30- CHILD:- Look how many stars it is together!
0:55:31 > 0:55:33- WOMAN:- You can see them so clearly.
0:55:36 > 0:55:37You look.
0:55:37 > 0:55:40It is wonderful, you know, that when you think about it,
0:55:40 > 0:55:44the whole universe, the whole of physics is contained in a snowflake.
0:55:45 > 0:55:49To describe them, you need all four forces of nature.
0:55:49 > 0:55:52You need gravity
0:55:52 > 0:55:54to allow the snowflake to fall down through the clouds
0:55:54 > 0:55:55and onto the ground.
0:55:55 > 0:56:00You need electromagnetism to stick all those water molecules together
0:56:00 > 0:56:03to form these beautiful crystals.
0:56:03 > 0:56:05You need the nuclear forces
0:56:05 > 0:56:09to stick the atomic nuclei of oxygen together.
0:56:09 > 0:56:13And then you need to understand about symmetry
0:56:13 > 0:56:15and symmetry breaking.
0:56:15 > 0:56:18All the fundamental ideas that underline modern physics
0:56:18 > 0:56:22can be thought of in the journey of a snowflake to the ground.
0:56:26 > 0:56:29- WOMAN:- Oh, look! How many stars do you think there are?
0:56:29 > 0:56:30- CHILD:- Oh, wow!
0:56:33 > 0:56:37Every snowflake shares the same building blocks,
0:56:37 > 0:56:43the same basic, beautiful symmetric forces of nature at their heart.
0:56:43 > 0:56:46But because of their histories, because of the way they formed,
0:56:46 > 0:56:48they're all different.
0:56:48 > 0:56:51And so it is with solar systems, so it is with planets
0:56:51 > 0:56:54and so it is with people.
0:56:54 > 0:56:56We're all made out of the same building blocks,
0:56:56 > 0:57:00but we're all slightly and magnificently different
0:57:00 > 0:57:02because of the history of our formation.
0:57:10 > 0:57:12The structures we see in the universe,
0:57:12 > 0:57:16like stars and planets and trees and snowflakes,
0:57:16 > 0:57:18are shadows of something deeper.
0:57:20 > 0:57:25They mask an underlying beauty and simplicity.
0:57:27 > 0:57:32But isn't it a beautiful thought that our origin and evolution...
0:57:33 > 0:57:37..just like the structure of a snowflake in a snowstorm,
0:57:37 > 0:57:42can be explained by a few simple natural laws?
0:57:43 > 0:57:46And isn't it a wonderful idea that that thought came
0:57:46 > 0:57:49from just looking carefully at nature
0:57:49 > 0:57:51and trying to understand it?
0:58:04 > 0:58:10# You are my lucky star
0:58:12 > 0:58:16# You open heaven's portals
0:58:16 > 0:58:20# Here on Earth for this poor mortal
0:58:21 > 0:58:27# You're my lucky star. #