Original subtitles

It's 10 degrees below zero...

and a silent killer that has stalked mankind for thousands of years...

is about to strike again.

Cold is one of the most surprising forces in nature-

both a dealer of death...

and the key to life...

in ways only revealed by big history.

We think of history as a timeline...

a series of events stretching a few thousand years into the past.

It's time to think bigger.

Instead of a line, imagine a web of infinite connections...

interacting over billions of years...

linked together to create everything we've ever known-

our universe, our planet...

and us.

When we consider our most epic moments though the lens of science...

we unleash a revolutionary new idea.

The movement of atoms steered the movements of men...

civilizations, galaxies.

History as we know it is about to get big.

French emperor Napoléon Bonaparte's invasion of Russia...

has ended in disaster.

Six hundred thousand French troops went in.

Six months later, more than 60% of them are dead.

But the killer isn't the Russian army.

It's the subzero temperatures.

Traditional history tells us that Napoleon was defeated by the Russian cold.

But big history shows that the root of his downfall...

is hidden within us.

Big history reveals that humans have been at grips with cold...

from the beginning of our history.

Cold impacted us in a great way...

simply because we had to adapt to it.

If we don't adapt...

we die.

Humans are not built for extremes.

As our core temperature drops...

organs like the liver begin shutting down. -.

To preserve heat for the brain.

If our core drops below 86 degrees Fahrenheit...

for more than a few minutes...

we die.

To understand why our bodies shut down in the cold...

big history connects back to a time before humans-

250 million years ago.

All the animals on Earth are cold-blooded.

They're sluggish and helpless...

until the sun's energy warms them and speeds up their metabolism.

But now a tiny, mammal-like creature...

evolves the ability to generate heat within its own body.

No longer dependent on the sun to warm it...

this creature can be active at any time of the day or night.

Warm-blooded creatures are always ready to move.

So warm-bloodedness does really have some advantages.

It's a survival edge that passes to all warm-blooded descendants...

including us.

But this advantage can also be a limitation.

In nature, heat moves from hot to cold.

So our bodies' warmth is always escaping...

radiating out through our breath and our skin.

As humans spread across the planet to cold climates...

they'll need to figure out ways to hold in that heat.

These humans have left tropical Africa, where they evolved...

and headed north...

into the grip of a brutal ice age.

This is the Mediterranean.

But it's as frigid as the Arctic Circle.

To survive the cold...

these humans invent one of humanity's most momentous tools-

the humble needle.

They had to have had the ability to make finely-tailored clothing...

because there's simply no way you could survive in ice-age Europe...

without having those technologies.

Clothing gives humans a thicker skin...

that insulates us against the cold.

But clothing also changes who we are...

because this thicker skin blocks something all humans need-

the sun hitting our skin.

And covering up, they weren't getting enough sunlight...

so they didn't create as much vitamin D as they needed.

Our bodies create vitamin D...

when exposed to the sun's U. V. radiation.

Back in Africa, our dark skin alone blocked most of the sun...

letting in just enough to create the vitamin D we need.

But now, in the colder north...

the combination of dark skin and head-to-toe clothes...

blocks the sun far too much.

One way of dealing with that is to evolve lighter skin...

that didn't block the rays of the sun as much.

So cold and clothes...

lead to lighter skin...

and a fundamental division we think of today as race.

Just as cold changes people...

it' also has a power over the elements.

Big history links forward to Napoleon's battlefield...

where his soldiers are defeated...

by the chemistry of cold.

Some French soldiers use tin buttons on their coats.

Bu! in subzero weather, tin has a fatal flaw.

Cold can change the properties of certain elements...

in some cases adversely.

For example, shiny metallic tin...

under cold conditions, can change form...

and then even turn into a powdery substance.

Coming from a Warm climate...

the French don't realize their buttons will fail.

That loss may have doomed thousands.

But the Russians have the home advantage...

and they're well prepared for the cold.

They knew how to dress. They knew exactly how to build shelter.

And they knew how to live with it. It was just that simple.

And big history reveals...

that this frigid defeat...

is a key to understanding a deeper story.

Cold divides the planet into opposing tribes...

and is the secret force behind the longest-running battle in history.

Big history is a new way to see the world.

It reveals how our battle against the cold...

turns us warm-blooded...

divides us into races...

and turns the tide of war.

But cold ls also at the heart of a global struggle...

a 5, 000-year war that can only be revealed...

on big history.

On planet Earth, warm climates produce farming...

cities, civilization.

But further north, in places like the frozen steps of Asia...

it's too cold for anything to grow...

except endless grass.

Grazing animals, like cattle and horses, thrive here.

People adapt.

They become herders. ..

And the world's first horsemen-

experts at raiding and plundering.

Horse-based warrior cultures...

are going to be the optimal mode of existence.

Created by the cold...

these fighters from the frozen north, where resources are scarce...

will wage war against their rich neighbors to the south.

It's a pattern repeated around the world.

Where it's cold, people become fierce nomadic warriors.

Where it's warm, people build vast civilizations.

Then the warriors of the cold charge in on horseback...

to take what they can.

From the tribes that swarm over China's great wall...

to the Goths and Vandals who destroyed the Roman Empire...

to the Mongols who conquer most of the known world...

an epic raid by people of the cold...

that lasts 5,000 years.

From the perspective of big history, we see this division...

will be sort of a critical dynamic in human history.

Cold has such a power over us...

because humans are not designed for extremes.

We must adapt or die.

Bu! what' if man could figure out how to control cold?

An American businessman, Frederic Tudor...

is one of the first to try.

He had a crazy entrepreneurial idea...

which was to cut large blocks of frozen New England ponds in January...

and sell them to the tropics as a form of ice.

Tudor is trying to solve an ancient problem.

In Earth's oxygen-rich atmosphere...

it's easy to create fire.

As far back as a million years ago...

our ancestors learned how to harness portable heat.

But it's trickier to master cold.

It's a law of the universe...

that heat likes to flow from hot to cold.

So it's easier to warm up something cold...

than to cool something hot.

Ice is concentrated cold...

and a possible solution...

but it can't exist everywhere...

because in order to cool things down, ice has to melt.

So when you plop an ice cube into a drink...

it's not that it's radiating coldness out into the drink to keep it cold.

What it's actually doing is drawing energy...

away from the liquid around it...

in order to melt.

Big history connects the physics of melting ice...

to the way the Earth works.

Ice forms across nearly a quarter of the Northern Hemisphere during winter.

Most of that ice is inaccessible...

sitting atop mountains...

or locked in glaciers in the remote far north.

Across the world today...

five billion of the planet's seven billion people...

live in areas where ice forms rarely or not at all.

So to truly harness cold...

we have to move ice from where it occurs naturally...

to where it doesn't...

and keep it from melting too fast...

which is exactly what Frederic Tudor figures out how to do.

He ships a load of ice 2,000 miles...

from Boston to the tropical island of Martinique.

For the first time in history, man controls the cold...

by making it portable.

He figured out new ways to pack the ice in sawdust in the ship's holds...

and then put layers of straw and apples on top to defray the costs.

Eventually he was able to sell it at an astronomical profit.

Now the world will no longer be divided...

between places that have cold and places that need it.

The simple act of spreading cold across oceans...

and continents...

will remake life on planet Earth.

Big history has revealed that cold...

had a hidden power over our bodies...

and our civilization.

But once we take control over cold by making it portable...

cold can be anywhere...

and it changes everything.

Cold begins to ignite a revolution in how we live...

and where we build our cities.

With ice-cooled freight cars...

you can transport the power of cold overland...

and ship fresh food across a continent.

Major industries rise up built entirely on cold.

But once people are hooked on it...

they have a problem if ice doesn't form in warm winters.

So that spurs innovation...

replacing ice with electric refrigeration and air conditioning...

that let our cities rise to the skies...

and our deserts bloom into metropolises.

But as much as it has shaped civilization...

the big history of cold has also shaped our entire universe.

13.7 billion years ago...

the big bang is the hottest thing that ever happens in the cosmos.

But it's cold that turns that primal energy...

into a universe of atoms, stars and planets.

Right after the big bang, things were incredibly hot...

so hot that the very atoms that we know today didn't exist.

They would have just disintegrated because it was too warm out.

So, really, it was a process of cooling down over time...

that gave us the universe we had.

And in a sense the story of the universe...

is the story of cooling down.

Billions of years later...

when our own solar system takes shape...

Earth forms in a narrow band...

where the perfect level of coldness allows liquid water to exist-

the prerequisite for life.

So the idea of coldness itself...

runs right across big history...

from the creation of the universe itself to the creation of stars...

to the creation of the Earth itself...

which appeared in just the right degree of coldness for us.

But the cold that created the physical universe...

will ultimately bring it to an end.

Because the same physics...

that cause a melting ice cube to draw heat from a glass of water...

exist everywhere.

Stars and galaxies will slowly dissipate into the cold emptiness of space.

Eventually, stars die...

temperatures drop...

atoms spread out.

In a sense, the story of big history is the story of starting extremely hot...

in the big bang...

and moving slowly towards extremely cold.

Because in countless billions of years in the future...

it's gonna get so cold that there are no gradients.

There's no difference between hot and cold.

And in a universe born in a blaze of heat...

cold will rule forever.

But the story of cold is just the beginning.

There's a much bigger puzzle hidden in big history.

Each episode unlocks a clue.

Everyday things like meteors...

secret codes...

and silver hold the key.

Watch them all and you'll see this grand mystery revealed-

the big history of time, of space.

The big history of us.