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00:00Our world is beautiful to look at.
00:25It's even more beautiful to understand.
00:42Forces of unimaginable power have forged our precious planet.
00:56They've created landscapes of endless variety and wonder.
01:06The forces of nature are hidden in the shapes that surround us.
01:15Read the codes written into the shapes of nature, and you will understand the rules
01:25that shape everything in the cosmos.
01:55Children playing in the late autumn sun in northern Spain.
02:07Nothing could seem more normal.
02:14But these aren't ordinary children.
02:28Carla Balcias and her friends are about to put their lives in the hands of a force so
02:33strong that it creates the shape of our planet.
03:03They're going to do something that would terrify most parents.
03:33These children are going into battle with a fundamental force of nature.
03:50The force of gravity.
03:56Towns from across the region compete to build the highest human towers.
04:15Carla's family are here with their team from Villafranca.
04:27The family put their trust in the strongest members of the Villafranca team.
04:33People like David Moret.
04:45It may seem like we're a group of people from the outside,
04:53and that we dress up in a totally anarchic way, without any rigor.
05:00But no, no, all the structures are symmetrical at the bottom,
05:05they have their own crest, and they create concentric lines towards that point,
05:10so that all the forces go together.
05:13These human towers give us a glimpse into what it takes to defy gravity.
05:23At the base, each team member is positioned
05:26so the bodies spread the weight above them as evenly as possible.
05:33To diffuse the force of gravity acting on them.
05:38It produces strong, simple shapes.
05:45The strongest is the circle.
05:50It's symmetrical, equal in all directions.
05:54No other shape distributes the weight of the tower more evenly.
05:59No other gives the tower such strength.
06:05But no matter how strong these shapes are, gravity is unforgiving.
06:35That's a worry if it's your child climbing to the very top.
07:06Villafranca are attempting to build the highest,
07:11most complex tower of the day to win the competition.
07:18And Carla, being so light, must climb to the very top.
07:25The power of Earth's gravity means the weight bearing down on David
07:32is hard to endure.
07:37If one person falters, the entire tower could buckle
07:42and Carla will plunge to the bottom.
07:47If they fall, it's the biggest defeat.
07:51The kids are the weakest. You never want them to fall.
07:55You want them to keep going.
08:26They've done it.
08:34The Castellers from Villafranca are the champions.
08:42The team's skill and the shape of their tower has defied gravity.
08:56But look at these towers in a different way
09:03and they reveal how gravity works.
09:11Imagine a group of kids in a tower.
09:17Imagine a competition like this in every country around the world.
09:24All the towers would fall in the same direction,
09:29not just down to Earth, but towards the very centre of our planet.
09:36Earth's gravity pulls everything down to one point.
09:43Earth's gravity pulls everything down towards its centre,
09:49no matter where you stand.
10:02And it's this property that shapes our planet.
10:13The gravity of our planet pulls everything inwards,
10:20including the rock from which it's made.
10:28Rock is forced inwards in every direction.
10:34And when that happens,
10:40there's only one shape a planet can be.
10:45A sphere.
10:59Our planet, a beautiful sphere, suspended in space.
11:09Earth is round because it has enough mass and so enough gravity
11:14to pull itself into shape.
11:19It's the same for the Moon
11:24and all the planets of the Solar System.
11:29It's why our Sun and stars throughout the Universe are spheres.
11:36Gravity is a universal force of nature,
11:41but it's not the only one.
11:47There's another force of nature.
11:50It holds atoms and molecules together,
11:54creating the shapes that surround us.
11:58It's called the electromagnetic force.
12:07It's so mystical when you leave in the morning in the fog.
12:13You're just looking around,
12:17and then you see these shapes that come out of the fog.
12:29They are big, big heavy objects,
12:33far bigger than anything that we've created floating on the sea.
12:39Doug Allen is an underwater photographer,
12:44and he wants to track down a dangerous and unpredictable shape.
12:52He's come to Newfoundland because this is iceberg season,
12:57and this place is called Iceberg Alley.
13:04Icebergs from the great glaciers of Greenland
13:08have drifted south to these shores.
13:12From here, ocean currents take them out into the Atlantic,
13:17and that's when icebergs can become lethal.
13:21Each summer, hundreds of icebergs drift into shipping lanes
13:25and oil fields off the coast here,
13:28threatening a multibillion-dollar industry.
13:32We've got to remember it was an iceberg that sailed past Newfoundland
13:36which ended up sinking the Titanic.
13:40Icebergs are some of nature's most spectacular natural sculptures,
13:46and they can be massive, hundreds of thousands of tonnes of solid ice.
13:53But despite their weight, icebergs never sink to the bottom of the ocean.
13:59They float.
14:01This strange property is a direct result of the force of electromagnetism,
14:09the force of nature that binds countless billions of molecules of water together
14:14to create these bergs.
14:19Water is a polar molecule.
14:21It has a positive end and a negative end.
14:24And at normal temperatures, the kinetic energy,
14:27the energy of the movement of the molecules,
14:29is way, way stronger than this polar forces.
14:32But as the water cools down and the molecules move more slowly,
14:37they begin to affect how the molecules line up.
14:44Water molecules are electrically charged,
14:48and opposites attract.
14:53The positive hydrogen atoms of one water molecule
14:56bond with the negative oxygens of others.
15:00And as water freezes, the molecules arrange into a lattice of hexagons.
15:07And that makes them take up more space.
15:12Ice is a really structured substance.
15:16It's almost hollow.
15:18It's a lattice structure.
15:20And as such, it's less dense than water.
15:24And the fact that it's less dense means that it floats.
15:29Almost all other liquids become more dense when they freeze.
15:35But water expands.
15:40The innumerable hexagons in each iceberg
15:43mean a 100,000-tonne block of ice can freely float in the sea.
15:49Icebergs still pose a significant hazard to shipping,
15:53not just local shipping to St John's,
15:55but also shipping coming across the Atlantic.
16:09Ever since the tragic loss of life on the Titanic,
16:13icebergs have been intensely monitored.
16:19Today, Doug is joining a team of scientists
16:22who want to predict how icebergs behave.
16:29The team want to gather data on the shape of an iceberg,
16:33information that will help predict its trajectory out to sea.
16:41The scientists are using specially designed remote sensors
16:45to scan icebergs from every direction.
16:53It's a complicated jigsaw, it's a little bit...
16:55You could think of it as a crime scene
16:57where you have the forensic people go in
16:59and they pick up little bits of clues
17:01and together you make a bigger picture.
17:06Aerial mapping and sonar robots are still in their test phase,
17:10so there's no substitute for first-hand observation.
17:18Particularly underwater,
17:20where the shape of the iceberg becomes just a shadow.
17:26It's hard to piece together what we're seeing above water
17:29with underwater without your imagery,
17:31so that's what this is going to be really helpful for.
17:37I'll actually get a picture of what the thing actually looks like
17:40so they can hopefully tell more about how accurate
17:43their sonar picture is compared to the real thing.
17:51BUBBLING
18:12It's quite eerie going down the side of the iceberg.
18:17You're going down into the darkness, into the blue, into the green.
18:29And very occasionally there'll be this really loud thump,
18:33just like someone had hit you with the flat of their heart
18:36in the centre of your chest.
18:41Being this close gives Doug an unrivalled view
18:44of the shape that's hidden beneath the waves.
18:51Thanks to the electromagnetic force
18:53that holds frozen water molecules together,
18:56ice floats, but only just.
19:01Seven-eighths of an iceberg is beneath the surface.
19:05The part underwater is called the keel.
19:10It catches the ocean's currents.
19:15And affects the speed and direction the iceberg will travel.
19:20Up this close, Doug has discovered the keel of the berg
19:24is riddled with even more intricate shapes.
19:29So while I'm swimming along the iceberg,
19:31I'm very aware of the dimpled shapes.
19:33It's like a giant golf ball on one side of me.
19:36And I'm just hoping that all these sort of observations from me myself
19:40and the fact that I'm putting them down on film,
19:42I'm hoping that that will be useful for the scientists.
19:48How was that?
19:52How was it? It was cold.
19:56It's a little bit murky.
19:58And I'll tell you all about it when I get on the boat.
20:04The irregular and hidden shape of iceberg keels
20:07means predicting their trajectory is still an immense challenge.
20:13Yet no matter how complicated their shape,
20:17it's the simple hexagon that makes an iceberg float.
20:25Billions upon billions of them form whenever water freezes.
20:35All icebergs started their life as tiny, delicate snowflakes.
20:43Come on.
20:48Each one shaped by the electromagnetic force.
20:56Up in the clouds, water molecules move fast and are flowing free.
21:03But when it's cold enough, the molecules slow down.
21:07Electromagnetism takes over and a hexagon appears.
21:12This simple shape becomes more intricate as each snowflake falls.
21:17Crystals grow from each corner.
21:27Every snowflake takes up a unique shape
21:30as it descends through the chaos of the atmosphere.
21:33Every snowflake is different.
21:36But the beautiful six-sided symmetry
21:39is an echo of the water molecules that made it.
21:45Perfect symmetrical shapes are the exception, not the rule,
21:49because the forces that shape nature
21:52are in a constant battle for supremacy.
21:56Gravity causes rivers to flow.
22:01The constant rush of water breaks the structure of rock apart.
22:11And so does gravity.
22:15It's the force of gravity.
22:19It's the force of gravity.
22:22Eroding and carving some of the greatest landscapes on our planet.
22:39In the vast sweep of African deserts,
22:42sand dunes are in a state of constant motion.
22:46Wind breaks the electromagnetic friction that sticks sand grains together.
22:52The force of gravity takes over
22:54and they tumble downhill until the two forces are back in balance again.
23:01At least for a moment.
23:16Mountains are the greatest testament
23:18to the battle between the forces of nature on our planet.
23:26Most of Earth's largest mountains peak at around 4,000 metres.
23:33Beyond that, the force of gravity makes them too heavy.
23:36The molecular bonds holding Earth's crust together
23:39can't support their weight.
23:47But in the Himalayas,
23:49Everest and its neighbours sit on particularly strong foundations.
23:57The Himalayas are one of the most important places in the world
24:01for the evolution of life on Earth.
24:06They can support the pull of gravity better.
24:14These are the highest mountains on our planet.
24:21But they're not the highest mountains that can exist.
24:29Mars is smaller than Earth.
24:31Crucially, that means it has less gravity, the great mountain slayer.
24:38On Mars, we can see the highest mountain in the solar system.
24:47With about a third less gravity pulling it down,
24:50Olympus Mons is nearly three times higher than Everest.
24:55It rises up 25 kilometres.
25:05Our beautiful sphere has been made rough
25:08by the battle between the forces of nature.
25:13Each wrinkle has created a new landscape.
25:17Landscapes that are home to life.
25:25And with life comes another rule of nature
25:28that creates myriad shapes in the natural world.
25:34Evolution.
25:36Nepal is home to a magnificent shape,
25:39created by life itself.
25:45A shape that is essential to life to survive up here.
25:52And a shape that is essential to life to survive up here.
25:59And a shape that is essential to life to survive up here.
26:07These men of the Gurung people are preparing to seek it out.
26:22They're going on an expedition
26:25to find one of nature's perfect shapes,
26:28superbly designed to save energy.
26:31The men are honey hunters,
26:33and they're leaving their village to find these.
26:41The largest honeybees in the world.
26:48The Himalayan honeybee builds giant hives
26:51that can be up to two metres across.
26:56The bees work endlessly to protect them.
27:00This Mexican wave is meant to scare off predators that approach it.
27:08Hidden beneath the protective layer of ferocious bees
27:11is a delicate network of exquisitely engineered hexagons.
27:21These carefully built cells are used to produce honey.
27:29These cells will be used to store honey.
27:33Essential food that will get the bees through the lean months.
27:40But why hexagons?
27:44What is it about hexagons this time
27:46that makes them the best shape for honeycombs?
27:50CHILDREN SING
27:56Some shapes are purely decorative.
28:02But the hexagon is useful.
28:07It's a shape that tessellates.
28:10It packs together, leaving no gaps.
28:14Other shapes do the same trick, like triangles or squares.
28:22But the honeybee only uses the hexagon.
28:33The hexagon is different to other shapes that tessellate.
28:37It's the shape that allows the bees to store their honey most efficiently.
28:44The bees have discovered a hidden physical rule
28:47that helps them survive the cold Himalayan winters.
28:57And twice a year, the Gurung villagers head into the mountains
29:01to exploit the space.
29:03On this trip, the leader, Min, is taking his young nephew, Hira,
29:08along for the first time.
29:33Building these enormous cones is hard work.
29:36It takes energy.
29:39For every gram of wax,
29:41a bee has to consume at least six grams of valuable honey.
29:46But the bees have learnt to use a rule of geometry.
29:50Of all the shapes that could be used for packing,
29:53the hexagon is the most efficient.
29:57It's the shape that needs the least wax to build.
30:00Which means the bees use up less energy making it
30:03and more honey can be put into storage.
30:17Hira approaches the hives from above.
30:20There's a lot riding on these homemade rope ladders.
30:50It's a lot of work.
30:54Be careful.
30:56Don't let the bees get away.
30:58Don't let the bees get away.
31:10It's scary.
31:12It's like being in a cave.
31:14It's a little scary.
31:20I'm scared that I'll die.
31:22I'm scared that I'll die.
31:28Finally, Min and Hira make it to the honeycombs.
31:37The honey hunters are precariously hanging in front of the swarm.
31:45Under constant attack,
31:47Min guides Hira,
31:49keeping him focused on the task ahead.
32:04Holding out the ladder,
32:06Hira and Min are on their way to the honeycombs.
32:14Min's long cutting tool makes the balancing act even harder.
32:23The hexagonal cells of the combs are packed full of honey.
32:28So much honey that each piece of honeycomb
32:31can weigh around 20 kilograms.
32:35One slip could mean all this effort is wasted.
32:39But Hira's first attempt at honey hunting is a success.
32:44Yes, that's it.
32:47I fell from the top.
32:49My uncle fell from the top.
32:52After my uncle fell,
32:54I fell too.
32:56I took the opportunity and fell too.
33:01The honey hunter told me
33:03that this is a very difficult task.
33:06I was scared.
33:08But he did a good job.
33:11He did a good job.
33:27Safely on the ground,
33:29the honey hunters can return home with their prize.
33:38In crafting their hexagonal cells,
33:40the bees are observing a rule of nature.
33:45The rule of efficiency,
33:47of saving and minimising energy.
33:53The bees need less wax.
33:56Less energy is spent on building their home.
34:01More honey can be stored.
34:04It's good for the Gurung people of Nepal and the bees.
34:10Hexagonal honeycombs
34:12are a magnificent expression of evolution.
34:24Evolution shapes life.
34:28And in the wetlands of Nepal,
34:31and in the wetlands of Florida,
34:33there's a bizarre creature
34:35that has adapted its shape to survive.
34:41These shallow waters provide shelter and protection
34:44for a vast array of marine life.
34:49But one creature is living life on the edge.
35:01The manatee.
35:06Florida is at the northern limit of where manatees live.
35:12Any further north would be perishingly cold.
35:24For this warm-blooded creature,
35:26it's a struggle for survival.
35:30Particularly with two extra mouths to feed.
35:37Each winter,
35:39manatees seek refuge in Florida's natural hot springs.
35:45Here to do a health check
35:47are Amy Tagg and Wayne Hartley.
35:50Got 23.5 degrees Celsius.
35:5323.5, OK.
35:57He is severely cold-stressed.
36:01With the cold stress, they don't eat.
36:04Their immune system shuts down.
36:07Not a good thing.
36:11They're here to keep themselves alive in the winter.
36:15They really require warm water.
36:20For manatees, a winter in Florida
36:23is like being in the Arctic.
36:27Although they're living on the edge of existence,
36:30their body shape has evolved to help them survive.
36:36Looking at this animal, you might think that he's quite fat,
36:40but in actuality, they have a very thick dermis layer,
36:44which is their skin, but they don't have a very thick fat layer.
36:49It might look like these animals keep warm like seals, using blubber.
36:55But they're not fat.
36:57They're just round.
36:59And round is the shape to be
37:01if you're trying to hold on to body warmth.
37:04This round shape has actually come to their benefit
37:07in that it reduces their surface area-to-volume ratio,
37:10so it's kind of like us getting cold
37:13and sort of being in the cold,
37:15and it's kind of like us getting cold and sort of huddling into a ball.
37:19Well, their roundness acts essentially in the same way
37:22to help them conserve their heat.
37:32Their bulbous bodies are also heated from the inside.
37:38They're filled with up to 40 metres of intestines,
37:41which act like an internal furnace as they digest their food.
37:50Sorry, their breath stinks.
37:53Of course. To me, it smells like the inside of a hot truck tyre.
38:00Florida manatees have evolved in this cold environment,
38:04and their shape has adapted to cope.
38:08In terms of pure physics,
38:10it would be ideal for the manatees to be spheres,
38:14the shape with the lowest surface area-to-volume ratio of all.
38:21But life doesn't quite work like that.
38:25Manatees have some pretty essential non-spherical parts.
38:30They share an ancestor with elephants.
38:33Their fins are built like legs.
38:37They've even held on to fingernails
38:40that protect their skin so they can walk on the bottom.
38:46And they have an elegant, paddle-shaped tail.
38:51It means although they're not the fastest animal, they can move.
38:57And keeping moving has become as important as keeping warm.
39:02Because the manatees are beginning to gather
39:05at another very unlikely hot spot.
39:14Amy is heading off to find them.
39:21The manatees' natural warm-water havens are fast disappearing.
39:28And their highly specialised bodies aren't adapting fast enough.
39:33Well, as the human population grows,
39:36more demand goes on to resources that we share with the manatees.
39:41It concerns me in that, you know,
39:43manatees' warm-water habitat availability is uncertain.
39:47It's really sad.
39:50You know, I don't want to see the species get to the point
39:53where it's going to disappear.
39:55Nobody wants to see that.
40:03The manatees' habitat is being replaced by ours.
40:10But in a strange twist to this story, that's not always such bad news.
40:20In winter, manatees have started to head to the city.
40:25To this power station, to be precise.
40:31The warm outflow water is a new haven for these vulnerable creatures.
40:41Around half of all Florida manatees now rely on power stations for warmth.
40:48Their round bodies holding on to this essential man-made heat
40:53to get them through winter.
41:06There are physical threats to the manatees' habitat.
41:11There are physical forces that shape our world.
41:23Gravity and the electromagnetic bonds between matter
41:27are the great sculptors of our planet.
41:41When it comes to life, evolution plays its part.
41:49Physical rules are compromised.
41:56But there's one rule of shape that is found everywhere.
42:02Symmetry.
42:04There is a beauty in the perfection of symmetrical shapes.
42:10There is a beauty in symmetrical patterns.
42:16Symmetry appears time and again in the shape of living things.
42:21That's because it's useful.
42:24It helps life survive.
42:27THUNDER RUMBLES
42:38These women are about to do something
42:41that will reveal why symmetry is essential to life.
42:46Why symmetry governs the shape of nearly every animal.
42:57They have a unique and inspirational way of making ends meet.
43:17Mrs Chae and Miss Kim are old friends
43:20and have grown up collecting seafood along these shores.
43:27And they still do it.
43:44These women are known as haenyeo, or sea women,
43:47part of a proud tradition.
43:57They'll take whichever sea creatures they find.
44:01But right now, it's the season for collecting conch.
44:10For Miss Kim and Mrs Chae,
44:12this is all about the search for food.
44:16But they are connected to the sea creatures which they are hunting
44:19in a much more fundamental way.
44:22We all are.
44:24We are all connected through symmetry.
44:29It's a rule of shape that evolved in Earth's ancient oceans
44:33billions of years ago.
44:37It's a rule of shape
44:39that evolved in Earth's ancient oceans billions of years ago.
44:46Evolution has taken this rule and used it to shape life.
44:57At first glance, it looks like it's purely decorative.
45:02But it's much more than that.
45:06It's a rule of life found across the animal kingdom.
45:16EXPLOSION
45:23Life is, and always has been, a competition.
45:28In an ancient, free-floating world,
45:30life adopted different types of symmetry to get what it needed.
45:35Some organisms became round, or radially symmetric.
45:40Their bodies are organised equally around a central axis.
45:46Rather than hunting down food,
45:49they wait for food to come to them from any direction.
46:00But to go on the hunt, it pays to be divided down the middle.
46:07This bilateral symmetry gives you a left and a right.
46:11This means a head with sense organs can develop.
46:14And this means you can control direction,
46:17orient yourself, escape, or target your prey.
46:29A symmetrical body plan
46:31has become part of nearly every type of animal on the planet.
46:35From a plankton to a person.
47:05It feels good when you catch fish,
47:08but it feels bad when you don't catch anything.
47:2410kg.
47:2711kg, 14kg.
47:3614kg.
47:54The rules that govern the natural world are all around us.
47:59We can't see them directly,
48:02but we can see their shadows in the shapes that make up our world.
48:10Every shape we see is made from building blocks.
48:19Bound by the forces of nature,
48:22moulded by gravity,
48:26moulded by gravity,
48:30honed by evolution.
48:39From a few simple rules emerges complexity.
48:47The rich, magnificent diversity of our planet.
48:55From a few simple rules emerges complexity.
49:07From a few simple rules emerges complexity.
49:16The rich, magnificent diversity of our planet.