Oceans, they cover two-thirds of the surface of the Earth.
For centuries, humans have been able to do little more than skim across the ceiling of
this alien world, most of it remained catalyzingly out of reach.
The creatures of the deep were shrouded in mystery, surrounded by myths of lost cities,
mermaids and monsters.
Over the last 150 years, we have explored ever deeper into the ocean.
Since then our knowledge of this hidden world has been steadily rising, but we began on
the surface, staring at an endless horizon.
So what is an ocean?
An ocean is quite simply a large expanse of water, today there are five of them.
The Arctic Ocean is the smallest and made up almost entirely of ice.
The Southern Ocean completely surrounds the continent of Antarctica.
Next is the Indian Ocean, with the warmest sea on Earth.
The Atlantic is so big, it would cover the continents of Africa and Europe and still
have room to spare.
But even this is dwarfed by the largest ocean of all, the Pacific, it covers a third of
the globe, parts of it are 35,000 feet deep, that's 29 Empire State Buildings piled up.
In ancient times people had little idea about the huge scale of the oceans, the Greeks believed
a river ran around the edge of the world, surrounding a single landmass, they called
the river ocean.
From earliest times people thought the Earth was flat, and that if they traveled too far
they would be dragged over the edge by a huge waterfall.
The Earth was never flat, but its surface has changed much over billions of years.
Soon after it was formed, the Earth began to cool, clouds formed, and rain gradually
filled the oceans.
Much later, land formed into a single continent, called Pangaea, surrounded by one vast ocean
called Panthalysa, meaning all sea.
Ever since, the rocks of the Earth's crust have been shifting to produce the continents
as we know them today, and the oceans have formed between them.
Under the waves, the Earth is still restless.
Up beneath the Atlantic, hidden under two miles of water, molten rock bubbles out of
the ground.
It has formed a mountain range longer than the Himalayas, the Rockies and the Andes combined.
Called the Mid-Atlantic Ridge, it is a sign of growth, the Atlantic is actually getting
wider each year.
It may be a slow process, but it all adds up.
If Christopher Columbus made his voyage today, he'd find the ocean stretched further by
a whole ship's length.
Where there is growth, there must also be shrinkage, or the Earth would burst open.
The shrinkage happens at the deepest points on Earth, or trenches.
Here one part of the crust slides under another, carrying the rock down to the heart of the
planet.
Around Hawaii, the ocean is so deep that if you add its depth to the height at the peak
above, Mauna Kea, you discover the highest mountain on Earth.
But despite millions of years of change, the oceans remain linked in one vast mass.
Wherever you are on the planet, dip your toe in the water and you are connected to every
ocean.
Considering the scale of the ocean, it's a wonder that this planet is not called water
instead of Earth.
Oceans are where life began, and the source of the water that sustains all life.
They contain 99% of the living space on the planet, a living space providing homes for
the most remarkable creatures.
There's a huge variety of life in the ocean, many more groups of animals than on land.
The startling colors of coral may resemble flower gardens, but these submarine cities
are made up of billions upon billions of tiny creatures.
Although they are small, coral have created the largest structure on the planet made by
living things, Australia's Great Barrier Reef.
The largest fish is the whale shark, reaching 60 feet long, but this huge creature eats
mostly tiny plankton.
And some smaller fish join forces to create an impression of size.
These shoals contain tens of thousands of fish, all swimming together to confuse predators.
It's a complex food pyramid of the ocean, at the base are plankton, countless tiny plants
and animals.
These are in turn eaten by thousands of fish, which may provide a meal for a single whale,
the largest creatures on earth.
Color of the ocean always seems blue, because other colors penetrate water less easily.
Red light travels the least distance, and even blue light can only reach down 1500 feet.
Though this, the waters are dark, and until recently we believed, devoid of life, how
wrong we were.
Like light, we were excluded from the depths, and for centuries the oceans were a barrier
to exploration, even on the surface.
Legend has it that the Egyptians and Phoenicians found it impossible to defeat the currents
of the Mediterranean, until the invention of the sail, nearly 8,000 years ago.
In ancient times, the power of the oceans was attributed to gods, like the Greek Poseidon,
who rode in a carriage drawn by dolphins.
Sea creatures were said to dance at his passing.
In early voyages around 1000 AD, the Vikings may have been the first to discover America,
but such journeys were rare.
The great civilizations of the world remained isolated.
For early civilizations, maps were virtually useless, although by the time of Ptolemy,
the Greeks had changed their thinking.
As of a central land mass, his map shows the ocean completely surrounded by land.
By 1519, the map of the world began to resemble the picture we have now.
In that year, Magellan set off on his three-year voyage, the first circumnavigation of the
globe, which proved at last that all the oceans were joined.
Early explorations were fueled by trade.
Such profits could be made by transporting exotic goods and spices, with ships able to
carry far more than any land transport.
Even today, 95% of world trade still travels by sea.
But as voyages extended around the world, beneath the surface, the oceans and their
inhabitants remained mysterious.
Sailors turned sea creatures into monsters, with tall tales of huge beasts with names
like the Kraken and Hydra.
Our understanding of ocean chemistry was also rather shallow.
For centuries, people believed a thin layer of salt water rested on top of a mass of freshwater.
In the 1660s, scientists finally analyzed samples from the deep ocean and concluded
that all the water in the ocean is salty.
There is so much salt that if you could extract all of it from the ocean, it would cover every
bit of land to a depth of five feet.
We'd all be up to our necks.
Saltiness varies throughout the oceans, and the more salt, the more buoyant the water.
As people on the Dead Sea, the saltiest sea on earth can attest.
By the 1670s, an Italian scientist showed in a simple test that saltiness is one factor
in keeping the oceans on the move.
Using a divided tank with salty water-colored blue and lighter, fresher water left clear,
he showed that the denser salty water will seep under, lighter freshwater, pushing it
up and creating circular flows, currents.
Many animals hitch rides on ocean currents.
One of the oldest creatures on earth, the blue shark, uses the Gulf Stream on its North
Atlantic journey in search of food.
They travel thousands of miles with their young around the ocean, returning in time
to breed.
Currents present a problem to plants and creatures that want to stay still.
The roots of kelp are actually an anchor to hold the plant in place, with standing currents
that are the equivalent of an underwater gale.
Holding on with their tails are delicate seahorses.
They are among the slowest of all fish and cannot swim against the current, so the tail
becomes an anchor.
At his desk in Washington in the 1840s, Matthew Fontaine Mowry also liked to stay put.
Known as the pathfinder of the seas, he studied thousands of ships' logs, worked out their
speed in different conditions, and created the first ever comprehensive charts of wind
and current.
Their impact was immediate.
Sailing times across the oceans were slashed by up to a third.
Novel methods have been employed to track the shifting seas.
In the 1800s, thousands of bottles were released into the Atlantic.
Each one had a note asking the finder to return to sender, making it possible to chart the
currents, the original message in a bottle.
A clue to the direction of the currents exists in the drain of every wash basin in the world.
North of the equator, the water disappears in a clockwise direction.
But travel through an imaginary pipe to the southern hemisphere, and you'll find the
same spiral appears to move counterclockwise.
The same is true of the ocean currents because it's the spin of the earth that determines
the water's movement.
Water takes 3,000 times more energy to heat than air, and it takes longer to grow cold,
so water stays warm even as it flows to the poles, smoothing out temperature differences
like a global thermostat.
Where hot and cold air meet, terrible storms may develop, unleashing the mighty force
of the ocean.
The highest wave ever recorded was one and a half times the height of Niagara Falls.
In the 19th century, we discovered that it's the wave that moves, not the water.
An object floating in open sea will move in a circle back to its original position as
a wave passes.
It's a different matter, of course, at the shore, that area repeatedly covered and uncovered
by the tides.
As levels of land and sea have shifted over thousands of years, even greater areas have
been uncovered, leaving fossils of sea creatures high and dry.
And cities flooded, like Atlantis, the legendary city forever hidden in the water.
Tides of the ocean vary with the Earth's changing temperature.
The slightest temperature rise, just half a degree, would expand the ocean and melt
enough ice to cause flooding around the world.
Currently more than a tenth of the water on the planet is locked up in the ice caps, forbidding
places for humans, but many animals have adapted to the cold.
The Weddell Seal is the most southerly mammal thriving in the Antarctic freezer.
In the winter, it spends most of its time submerged because the water below the ice
stays warmer than the air above.
The oceans abound with life, and humans have always harvested their riches.
For centuries, fishermen relied on luck as much as skill, and finding the best catch.
Eventually they learned the habits of ocean creatures.
Dolphin often swim above tuna, so humans tagged along to find their catch.
For years they would accidentally kill the dolphin, as well as the tuna.
Modern fishing methods have become far more sophisticated in targeting their catch.
They are now so effective that in some areas, they threaten to fish the oceans clean.
The first confirmation of life throughout the deep came in the 1870s, when the ship
HMS Challenger, equipped with the latest technology, made the first full-scale study of the ocean.
Temperatures at different depths were measured, and nearly four and a half thousand new species
of plants and animals were collected.
The voyage proved conclusively that there was abundant life in the ocean depths.
To find their position at sea, early sailors relied on measuring latitude from the stars,
using a sextet, and longitude from the sun's altitude at certain times of the day.
But knowing the time at sea was an inexact science.
In the 18th century clocks used pendulums, and the motion of a ship made these very unreliable.
It was only with the invention of the chronometer that the problem of longitude was conquered.
The pendulum was replaced by an escapement wheel, and as a byproduct the world gained
a more accurate watch.
Early efforts to measure depth relied on a cannonball and rope, hardly accurate when
the line itself was heavy enough to keep playing out even after the shot hit bottom, a real
case of how long is a piece of string.
Today depth is measured by sonar, like the echolocation used by dolphins.
The oceans can be very noisy.
The shrimp clicks with such frequency that it creates its very own sonar static.
Sound travels five times further in water than in air, very effective for keeping in
touch.
The humpback whale's mating call is believed to be the acoustic equivalent of the peacock's
tail, announcing the presence of a male to the females.
But thanks to the distant sound travels, the males can start singing while they're still
hundreds of miles away from the females.
Although the song they sing keeps changing, all humpbacks of the same pod sing a similar
song.
Maybe they're just following the latest musical trends.
No one, however, seems able to fathom the mysteries of the Bermuda Triangle.
In this corner of the Atlantic Ocean, strange things happen to instruments.
Whales lose their sense of direction.
There have been over 140 cases in which boats and aircraft have just vanished.
Just as many theories about where they have all gone.
Some suggest they've traveled in time.
Centuries ago, people believed that some animals would literally disappear for a while each
year.
The first one we know today is migration.
Turtles are among the greatest voyagers.
Leatherbacks follow the currents and their food jellyfish thousands of miles from the
West Indies, past Europe, and up to the Arctic.
Humans have used the oceans to migrate too.
Among the earliest were the Polynesians, who crisscrossed the Pacific, visiting every island
big or small, except it seems Australia.
More recently, hundreds of thousands of Europeans crossed the Atlantic to America.
This route gave rise to a famous ocean race, the Blue Ribbon, awarded for the fastest crossing.
In the 1830s, the Great Western took 15 days.
But by 1986, this had been trimmed to just three and a half days.
Nautical speed has always been measured in knots, because sailors would count the knots
in a rope as it passed through their hands into the water from a ship, as the sand in
a timer ran out.
For humans to explore the deep ocean, they needed a protective shell.
One of the first was Halley's diving bell, dating back to 1690.
A wooden cask with an open bottom, it allowed scientists to descend in their own air bubble
and study life to a depth of just 60 feet.
In the 1830s, Augustus Zebers hired helmeted divers, looking more like astronauts than
sailors, could go down to 200 feet, limited by the umbilical link to a ship above.
Exploration in the 19th century prompted authors to dust off tales of underwater adventure,
beasts and monsters.
Jules Verne and H.G. Wells set a fashion that filmmakers would be eager to follow, doing
their best to recreate the drama of the deep.
In 1943, it was Jacques Cousteau's invention of the scuba, standing for self-contained
underwater breathing apparatus, that finally allowed us to fathom this new world untethered.
But the first scuba dives only got us to a depth of 160 feet.
The seal is able to dive straight off land and down into the depths, but humans can't.
We must spend time adjusting to the pressure, and below certain depths, that pressure is
just too much.
How much?
At the deepest point of the ocean, the pressure is the equivalent of a human trying to support
50 jumbo jets, which makes the discovery of animals at these depths even more amazing.
These creatures have adapted to the pressure with lightweight bones and muscles, and their
skin is so fine that they literally disintegrate if we bring them to the surface.
In the 1930s, two Americans, Beebe and Barton, set a new record for deep sea diving, protected
from the pressure in a bathysphere, named for the Greek words for deep ball.
They reached 3,000 feet, we could finally observe life in the darkness of the depths.
The deeper we went, the more we discovered, cut off from any glimmer of sunlight.
Down here, most creatures are able to make their own light, perhaps to dazzle predators
or act as camouflage.
Combined with lights from an exploring vessel, it makes some of them, like these comb jellies,
look more like spacecraft than animals.
And strangely enough, we knew the distance to the moon years before we knew the depth
of the ocean.
We took a scientist from Landlock, Switzerland, to invent a craft capable of reaching the
deepest point on earth, a depth of over 35,000 feet.
In 1960, August Picard's vessel, the Trieste Pacific, it's like going down more than 3,000
floors in an elevator.
And here in 1977, in the depths of our planet, lurked a surprise, a challenge to our understanding
of biology, life evolving without light.
Somehow bacteria were living on hydrogen sulfide gas emitted by deep sea vents, and that bacteria
became food for other creatures.
Photosynthesis had a rival, chemosynthesis.
We may have finally reached the deepest point on earth, but only one twentieth of the ocean
floor has been mapped.
There may be millions of new species in the regions that remain hidden, but such findings
will have to await some future journey.
We are only visitors to this world, and in returning to our world, we can be sure of
only one thing.
Our knowledge of the deep is still little more than a drop in the ocean.
For now, thanks for watching.