The greatest triumph of civilization
is often seen as our mastery of heat.
Yet our conquest of cold is an equally epic journey,
from dark beginnings, to an ultra cool frontier.
For centuries, cold remained a perplexing mystery
Nobody had any idea what it was.
Much less how to harness its effects.
Yet in the last 100 years,
cold has transformed the way we live and work.
Imagine homes or supermarkets without fridges and frozen foods
or skyscrapers without air-conditioning,
or hospitals without liquid oxygen.
We take for granted the technology of cold,
yet it has enabled us to explore outer space
and the inner depths of our brain.
And as we develop new ultra cold technology
to create quantum computers and high-speed networks,
it may even change the way we think and interact.
This is the story of
how scientists and dreamers over the past four centuries
plunged lower and lower down the temperature scale
to conquer the cold, enrich our lives
and attempt to reach the ultimate limit of cold.
A Holy Grail as elusive as the speed limit of light:
absolute zero.
Extreme cold has always held
a special place in our imagination.
For thousands of years, it seemed like a malevolent force
associated with death and darkness.
Cold was an unexplained phenomenon.
Was it a substance, a process, or some special state of being?
Back in the 17th century, no one knew,
but they certainly felt its effects
in the freezing London winters.
(Simon Schaffer) 17th-century England was in the middle
of what's now called "the little Ice Age."
It was fantastically cold by modern standards.
You have to imagine a world lit by fire
in which most people are cold most of the time.
Cold would've felt like a real presence,
a kind of positive agent that was affecting how people felt.
And not fitted nicely
with the most orthodox received view,
that natural philosophers inherited from the greeks,
from Aristotle, hundreds of years earlier,
that there are two agents in the world:
hot and cold.
They function symetrically.
They can combine
or separate.
Back then, people felt at the mercy of cold.
This was a time when such natural forces
were viewed with awe as acts of God.
So anyone attempting to tamper with cold did so at their peril.
The first to try was an alchemist, Cornelius Drebbel.
On a hot summer's day in 1620,
King James I and his entourage
arrived to experience an unearthly event.
Drebbel, who was also the court magician,
had a wager with the King
that he could turn summer into winter.
He would attempt to chill the air
in the largest interior space in the British Isles:
the great hall of Westminster.
Drebbel hoped to shake the King to his core.
(Andrew Szydlo) He had a phenomenally fertile mind.
He was an inventor par excellence.
His whole world was steeped in the world of alchemy,
of perpetual motion machines,
of the idea of time, space,
planets, moon, sun, gods.
He was a fervently religious man.
He was a person for whom nature presented
a phenomenal... a galaxy of possibilities.
Dr. Andrew Szydlo, a chemist
with a lifelong fascination for Drebbel,
enjoys his reincarnation as the great court magician.
Like most alchemists, Drebbel kept his method secret.
Dr. Szydlo wants to test his ideas
on how Drebbel created artificial cold.
When Drebbel was trying to achieve
the lowest temperature possible, he knew that ice, of course,
was the freezing point, or the coldest you could get normally.
But he would've been aware of the facts
through his experience that mixing ice with different salts
could get you a colder temperature.
Salts will lower the temperature at which ice melts.
Dr. Szydlo thinks Drebbel probably used common table salt,
which gives the biggest temperature drop.
But salt and ice alone would not be enough
to cool down such a large interior.
Drebbel was famous for designing elaborate contraptions,
a passion shared by Dr. Szydlo,
who has an idea for the alchemist's machine.
So here, we would've had a fan,
which would've been turned over
blowing warm air over the cold vessels there,
and as the air blows over these cold jars,
we would've had, in effect,
the world's first air-conditioning unit.
But could this really turn summer into winter?
(Dr. Szydlo) The idea was to stir it in as well as possible
in the 5 seconds that you have to do it.
Dr. Szydlo stacks the jars of freezing mixture
to create cold corridors for the air to pass through.
We can feel it's very cold,
in fact I could feel cold air
actually falling on my hands,
because cold air, of course, is denser than warm air,
and one can feel it quite clearly on the fingers.
The vital question:
would the gust of warm air become cold?
I can feel certainly a blast of cold air hitting me
as that 2nd cover was released.
Well, temperature, we're on 14 at the moment.
Yes, keep it going. That's definitely the right direction.
I think possibily even closer still would give us the best of...
So, how would the King have reacted
to this encounter with man-made cold?
He would've been shocked,
he wouln't have known what's happening,
he could've in fact been wondering
whether there was some action of gods
or some sort of forces,
demonological forces, which were in action
and he would have let pacefully freezing as he did so.
Had Drebbel written up his great stunt,
he might've gone down in history
as the inventor of the air-conditioning.
Yet it would be almost 3 centuries
before this idea eventually took off.
To advance knowledge and conquer the cold
required men with a very different mind set.
King James' Lord Chancellor Francis Bacon
was the first to apply the scientific method
to the study of heat and cold.
He believed it was important to conduct experiments
and analyze the results
rather than rely on the established wisdom of the ancients.
For Francis Bacon, heat and cold turned out to be
right at the center of his world view.
One way of understanding why that's so
is think why heat and cold matter to human beings.
They really matter in XVII century for two reasons:
one is the weather and one is disease.
There was after all an obvious tension in everyday experience
between the healty effects of warmth
and the healthy effects of cold.
Warmth made you healthy because it
stops you radiating away the vital spirits within you.
But cold obviously had crucial effects
against death as well.
It could preserve things for immensely long times
and maybe it could preserve Francis Bacon's body too.
Bacon rarely carried out experiments himself
but his one foray into the preservative effects of the cold
had disastrous consequences.
He took a freshly killed chicken.
and stuffed it full of ice and snow
to investigate how much longer the chicken meat might stay fresh.
He was impressed by the results.
The chicken did remain fresh for many days.
Unfortunately, during the process
of exposing his own body to the cold
he caught pneumonia.
As Bacon laid dying
it dawned on him that his fascination with the cold
was going to cost him his life.
The irony, tragedy of that rough sad experiment
didn't disuade his followers from doing more experiments
on ice and snow and its vital or preservative effects.
The men who followed Bacon were really convinced that
if we could understand the way in which
motion, cold and heat fitted together
we could save ourselves from disease,
we'd unlock the mysteries of the universe.
This fundamental question, "What is cold?"
haunted Robert Boyle,
who was born the year after Bacon died.
The son of the Earl of Cork, a wealthy nobleman,
Boyle used his fortune to build an extensive laboratory.
Boyle is famous for his experiments
on the nature of air,
but he also became the first master of cold.
Believing it to be an important, but neglected subject,
he carried out hundreds of experiments.
(Simon Schaffer) He worked through very systematically
a series of ideas about what cold is.
Does it come from the air?
Does it come from the absence of light?
Is it that there are strange,
so-called "frigorific" cold-making particles?
The dominant view, certainly in Boyle's lifetime,
the view that he set out to attack,
is that cold is a primordial substance
that when bodies get colder
they're sucking in this primordial cold
and as they get warmer they expel it.
Boyle thought that was wrong
and he did experiments to show that it was wrong.
Boyle was curious about the way water expanded when it turned to ice.
He wondered whether the increase in volume
was accompanied by an increase in weight.
He carefully weighed a barrel of water
and took it outside in the snow,
leaving it to freeze overnight.
Boyle reasoned that if once the water turned to ice the barrel weighed more,
then perhaps cold was a substance, after all.
But when they reweighed the barrel,
they discovered it weighed exactly the same.
So what must be happening, Boyle guessed,
was that the particles of water were moving further apart,
and that was the expansion,
not some substance flowing into the barrel from outside.
Boyle was becoming increasingly convinced
that cold was not a substance
but something that was happening to the particles,
and began to think back to his earlier experiments with his air pump.
Boyle's idea was that the air trapped in this glass container
is springy, it's elastic
and as you're trying compress it, it resists.
Now, this is very closely linked in Boyle's program
to the way he studies heat and cold
because his idea was
that as substances like the air get warmer
they tend to expand.
It's as though the little particles, little springs,
out of which he imagined each air particle is made,
were gradually unwinding,
so they take up more space and they expand.
Boyle's conclusion here
was that heat is a form of motion of a particular kind
and that as bodies cool down, they move less and less.
Boyle's longest-published book was on the cold.
Yet he found its study troublesome and full of hardships,
declaring that he felt like a physician
trying to work in a remote country
without the benefit of instruments or medicines.
To properly explore this country of the cold,
Boyle lamented the lack of a vital tool:
an accurate thermometer.
It was not until the mid-17th century,
that glassblowers in Florence
began to produce accurately calibrated thermometers.
Now it became possible to measure degrees of hot and cold.
Because rather than mercury they used alcohol, which is much lighter,
they made thermometers that were sometimes several meters long
and were often wound into spirals.
But there was still one major problem with all thermometers:
the lack of a universally agreed temperature scale.
There are all kinds of different ways of trying to stick numbers
to these degrees of hot and cold,
and they, on the whole, didn't agree with each other at all.
So one guy in Florence makes one kind of thermometer,
another guy in London makes a different kind,
and they just don't even have the same scale,
and so there was a lot of problem in trying to standardise thermometers.
Imagine that you want to make a scale of temperature.
What do you do?
Well, the obvious thing to do,
and this is well understood by instrument makers and experimentalists
in the 17th and 18th century
is to try to find something in nature
which you know always has the same temperature
and make that your fixed point.
A better strategy even is to find two such phenomena in nature
and then you have a lower fixed point,
something rather cold,
and an upper fixed point, something rather warm
and divide the degrees of temperature between
into say a hundred convenient bite sized chunks.
The problem however was to find, define a phenomenon
whose temperature you guessed was fixed.
So for the lower fixed point you might choose
the temperature of ice. just as it's melting.
And then there's an almost indefinite range
of possible candidates for your upper fixed point.
And Isaac Newton, for example,
worked rather hard on constructing what he called the Scale of Heat.
He, for example, defined
the temperature which a human can only just tolerate
if they plunge their hand into warm water.
It could be the normal human underarm,
the temperature of the human blood,
the temperature of wax just as it's melting.
The first temperature scale to be widely adopted
was devised by Daniel Fahrenheit,
an accomplished instrument maker
who made thermometers for doctors in Holland.
He used a mixture of ice, water, and salt for his 0 degrees;
ice melting in water at 32 degrees
and for his upper fixed point,
the temperature of the human body, at 96 degrees,
which is close to the modern value.
(Hasok Chang) One of the things that Fahrenheit was able to achieve
was to make thermometers quite small,
and that he did by using mercury
as opposed to alcohol or air, which other people had used.
And because mercury thermometers are compact,
clearly if you're trying to use it for clinical purposes,
you don't want some big thing sticking out of the patient!
So the fact that he could make them small and convenient,
that seems to be what made Fahrenheit
so famous and so influential.
It was a Swedish astronomer, Anders Celsius,
who came up with the idea of dividing the scale
into 100 divisions.
The original scale used by Celsius was upside down,
so he had the boiling point of water as zero
and the freezing point as 100,
with numbers just continuing to increase
as we go below freezing.
And this is another little mystery in the history of the thermometer
that we just don't know for sure.
What was he thinking when he labeled it this way?
And it was the botanist Linnaeus,
who was then the president of the Swedish Academy,
who after a few years said, "We need to stop this nonsense,"
and inverted the scale
to give us what we now call "Celsius scale" today.
A question nobody thought to ask
when devising temperature scales was "how low can you go?".
Is there an absolute lower limit of temperature?
The idea that there might be
would become a turning point in the history of cold.
The story begins with the French physicist Guillaume Amontons.
He was doing experiments on heating and cooling bodies of air
to see how they expand and contract.
- We're now going to put ice around that bulb and see what happens.
And he was noticing that, well, when you cool a body of air,
the volume or the pressure would go down.
And he speculated "Well, what would happen
if we just kept cooling it?"
By plotting temperature against pressure,
Amontons saw that as the temperature dropped,
so did the pressure, and this gave him an extraordinary idea.
Amontons started to consider the possibility
"What would happen if you projected this line back
until the pressure was zero?"
And this was the first time in the course of history
that people actually considered
the concept of an absolute zero of temperature.
Zero pressure, zero temperature.
It was quite the revolutionary idea when you think about it
because you wouldn't just think
that temperature has a limit of lower bound, or zero,
because in the upper end, it can go on forever,
we think, until it's hotter and hotter and hotter.
But somehow, maybe there's
a zero point where this all begins.
So you could actually give a calculation
of where this zero point would be.
Amontons didn't do that calculation himself,
but some other people did later on, and when you do it,
you get a value that's actually not that far
from the modern value of roughly minus 273 °C.
In one stroke, Amontons had realized
that although temperatures might go on rising forever,
they could only fall as far as this absolute point.
For him, this was a theoretical limit,
not a goal to attempt to reach.
Before scientists could venture towards this zero point,
far beyond the coldest temperatures on Earth,
they needed to resolve a fundamental question.
By now, for most scientists, the penny had dropped
that cold was simply the absence of heat.
But what was actually happening as substances warmed or cooled
was still hotly debated.
The argument of men like Amontons
relied completely on the idea that heat is a form of motion,
and that particles move more and more closely together
as the substance in which they're in
gets cooler and cooler.
Unfortunately, the science of cold
was about to suffer a serious setback.
The idea that cooling was caused by particles slowing down
began to go out of fashion.
At the end of the 18th century,
a rival theory of heat and cold emerged
that was tantalizingly appealing, but completely wrong.
It was called "The Caloric Theory"
and its principal advocate was the great French chemist
Antoine Lavoisier.
Like most scientists at the time,
Lavoisier was a rich aristocrat who funded his own research.
He and his wife, Madame Lavoisier,
who assisted with his experiments,
even commissioned the celebrated painter David
to paint their portrait.
Lavoisier carried out experiments
to support the erroneous idea that heat was a substance,
a weightless fluid that he called "caloric."
He thought in the solid state of matter,
molecules were just packed close in together,
and when you added more and more caloric to this,
the caloric would insinuate itself
between these particles of matter and loosen them up.
So the basic notion was that caloric was this fluid
that was, as he put it, "self-repulsive."
It just tended to break things apart from each other.
And that's his basic notion of heat,
as the cold is just the absence of caloric,
or the relative lack of caloric.
Lavoisier even had an apparatus to measure caloric,
which he called a "calorimeter."
He packed the outer compartment with ice.
Inside, he conducted experiments that generated heat.
Sometimes from chemical reactions,
sometimes from animals,
to determine how much caloric was released.
He collected the water from the melting ice
and weighed it to calculate
the amount of caloric generated from each source.
(Robert Fox) I think the most striking thing about Lavoisier
is that he sees caloric as a substance
which is exactly comparable with ordinary matter,
to the point that he includes caloric
in his list of the elements.
It's very easy to talk about the quantity of heat
and to think of it, as a fluid,
whereas the talk about the quantity of heat
and to think that it's a vibration
of the particles of matter, which was the other alternative,
that's much more difficult, conceptually.
It's a very hard model to refute
because if you can accept there's a substance
that doesn't have any weight
(indeed, for Lavoisier, heat, caloric, is an element.
Is an element like oxygen or nitrogen.
Oxygen gas is made of oxygen + caloric
and if you take the caloric away,
presumably the oxygen might liquify.),
that's a very hard model to shift because it explains so much,
and indeed, Lavoisier's chemistry
was so otherwise extraordinarily successful.
However, Lavoisier's story about caloric was soon undermined.
There was one man who was convinced Lavoisier was wrong
and was determined to destroy the caloric theory.
His name was Count Rumford.
Count Rumford had a colourful past.
He was born in America,
spied for the British during the Revolution,
and after being forced into exile
became an influential government minister in Bavaria.
Among his varied responsibilities was the artillery works,
and it was here in the 1790s
that he began to think about how he might be able to disprove
the caloric theory using cannon boring.
Rumford had noticed that the friction
from boring out a cannon barrel generated a lot of heat.
He decided to carry out experiments to measure how much.
He adapted the machine to produce even more heat
by installing a blunt borer
that had one end submerged in a jacket of water.
As the cannon turned against the borer,
the temperature of the water increased and eventually boiled.
The longer he bored, the more heat was produced.
For Rumford, what this showed was
that heat must be a form of motion,
and heat is not a substance,
because you could generate
indefinitely large amounts of heat
simply by turning the cannon.
Despite Count Rumford's best efforts,
Lavoisier's caloric theory remained dominant
until the end of the 18th-century.
His prestige as a scientist
meant that few dared challenge his ideas.
Sadly this did not protect him
from the revolutionary turmoil in France,
which was about to interrupt his research.
At the height of the reign of terror,
Lavoisier was arrested and eventually guillotined.
The reason he was guillotined was not because of his science
but because he helped run
the privatized income tax service of the French state.
There's nothing more unpopular, even in France,
than a privatized tax collector.
Once he was guillotined, his wife left France
and eventually met Rumford
when he moved to Western Europe in the early 1800s.
Rumford then married her.
So he'd married the widow of the man
who'd founded the theory that he destroyed.
The marriage was short-lived.
After a tormented year, Rumford left Madame Lavoisier
and devoted the rest of his life to his first love, science.
It would be nearly 50 years
before his theory of heat and cold was finally accepted.
A founder of the Royal Institution,
Rumford continued to support the pursuit of science.
And it was here that the next major breakthrough
in the conquest of cold would occur.
Michael Faraday, who later became famous
for his work on electricity and magnetism,
unwittingly carried out an experiment
that would begin the long descent towards absolute zero.
He was asked to explore the properties
of a newly discovered pungent gas called chlorine.
This experiment was potentially explosive,
which is perhaps why it was left to Faraday
and perhaps also why Dr. Andrew Szydlo
is curious to repeat it today.
We are about to undertake
an exceedingly dangerous experiment
in which Michael Faraday in 1823 heated this substance here,
the hydrates of chlorine, in a sealed tube.
Is that sealed?
(man) That's sealed, Andrew.
(Andrew) That's absolutely brilliant!
In the original experiment,
Faraday took the sealed tube and heated the end
containing the crystals.
He put the other end in an ice bath.
Soon he noticed yellow chlorine gas being given off.
(Andrew) Because the gas is being produced,
pressure's building up.
But because this side is so very cold,
hopefully what we'll see
is some tiny oily droplets of chlorine, liquid chlorine, being produced.
It's the pressure which is causing this.
Ray, this is where it starts to get dangerous,
so if you'll now take a few steps back...
When Faraday did the experiment, a visitor, Dr. Paris,
called him to see what he was up to.
Paris pointed out some oily matter in the bottom of the tube.
Faraday was curious and decided to break open the tube.
Right, so let's have a look inside here.
The explosion sent shards of glass flying.
With the sudden release of pressure,
the oily liquid vanished.
And there we are. Is that what happened?
Yes, that's exactly what happened.
It popped open, glass flew.
And can you detect
the strong smell of chlorine? - I can now.
Absolutely. Well, he detected the strong smell of chlorine
and this was a major mystery for him.
Faraday soon realized the increased pressure
inside the sealed tube had caused the gas to liquify.
Later, he used the same technique to liquify ammonia gas.
He noticed that on releasing the pressure, the liquid evaporated,
triggering a dramatic drop in temperature.
He predicted that one day this cooling might be useful:
"There is great reason to believe that this cooling technique with ammonia
may be successfully employed
for the preservation of animal and vegetable substances
for the purposes of food."
But Faraday's idea of using ammonia as a refrigerant
was ahead of its time.
Besides, he had no interest in commercial exploitation.
Across the Atlantic,
a Yankee entrepreneur had a very different philosophy.
and was about to commercialize cold.
Frederic Tudor had a chance conversation with his brother
that led him on a path
to become one of the richest men in America.
(Dennis Picard) The story goes, at the dinner table
they were trying to decide what they had on their father's farm
they could make money off of.
And certainly there was a lot of rocks,
but people weren't going to pay for that,
so they came up with the idea of maybe ice,
'cause some areas did not have ice.
And it seemed kind of crazy at first, but it paid off.
When Tudor began harvesting ice from New England ponds,
he soon realised he needed specialised tools
to keep up with the huge demand.
(Dennis Picard) We had the saws,
and the saws were an improvement over the old wood saws.
They have teeth that are sharpened on both sides
and set, so it cuts on both the up and the down stroke.
The crew could clear a 3-acre pond easily in a couple of days.
Tudor's dream to make ice available to all
was not confined to New England.
He wanted to ship ice to hot parts of the world
like the Caribbean and the deep South.
(Dennis Picard) When Tudor first tried to convince shipmasters
to put his load of frozen water into the ships,
they all refused, 'cause they told him
that water belonged outside the hull, not inside.
So he had to go find other investors to get the money
to buy his own ship, and he bought a ship
by the name of the "Favorite."
New England became the refrigerator for the world,
with ice shipments to the Caribbean,
the coast of South America and Europe.
Tudor even reached India and China.
Watching the ice cutters working Walden Pond,
Henry Thoreau marveled that water from his bathing beach
was traveling halfway around the globe
to end up in the cup of an East Indian philosopher.
Tudor, who soon became known as the "Ice King,"
began using horses and huge teams of workers to harvest
larger and larger lakes as the demand for ice grew.
During the latter half of the 19th century, the ice industry
eventually employed tens of thousands of people.
(Dennis Picard) Tudor became the largest distributor of ice,
and he became one of the first American millionaires.
And we're talking about one of his ships
going to the Caribbean giving him a profit of $6,000!
Now, this is in a time period when people were earning
$200 to $300 a year, the average family.
So someone earning thousands of dollars was just inconceivable,
and that would be losing 20% of your ice when it got there.
There was still huge amounts of profit.
Tudor's success was based
on an extraordinary physical property of ice:
it takes the same amount of heat to melt a block of ice
as it does to heat a similar quantity of water
to around 80 °C.
This meant that ice took a long time to melt,
even when shipped to hotter climates.
What started out as a small family enterprise
turned into a global business.
Frederic Tudor had industrialised cold
in the same way
the great pioneers of steam had harnessed heat.
By the 1830s, the Industrial Revolution was in full swing.
Yet ironically, it was not until a small group of scientists
worked out the underlying principles
of how steam engines convert heat into motion
that the next step in the conquest of cold could be made.
Only after solving this riddle of heat engines
could the first cold engines be made
to produce artificial refrigeration.
How much useful work
can you get out of a given amount of heat?
By the early 1800s, that had become
the single most important economic problem in Europe.
To make a profit was to convert heat into motion
efficiently, without wasting heat,
and getting the maximum amount of mechanical effect.
The first person to really engage with this problem
was a young French artillery engineer, Sadi Carnot.
He thought that improving the efficiency of steam engines
might help France's flagging economy
after defeat at Waterloo in 1815.
Working at the Conservatoire des Arts et Mètiers,
he began to analyze how a steam engine
was able to turn heat into mechanical work.
The originality of Carnot's treatement, in my eyes,
is essentially that he shows that in order to extract energy,
to extract work from the heat engine,
you need a high temperature source, which is the boiler,
and you need a low temperature, which is that of the condenser.
And the essence of the heat engine for Carnot
is that heat passes from the high temperature of the boiler
to the low temperature of the condenser.
In steam engines, it looks as though
heat is flowing around the engine,
and as it flows, the engine does mechanical work.
The implication there
is that heat is neither consumed nor destroyed.
You simply circulate it around, and it does work.
So, there the analogy would be between heat, in a steam engine,
and water, in a water wheel.
It's though it's the flow of heat
that's actually getting the work done in the standard steam engine.
Carnot likened this flow of heat
to the flow of water over a waterwheel.
He saw that the amount of mechanical work produced
depended on how far the water fell.
His novel idea was that steam engines worked in a similar way,
except this fall was a fall in temperature
from the hottest to the coldest part of the engine.
The greater the temperature difference,
the more work was produced.
Carnot distilled these profound ideas
into an accessible book for general readers,
which meant it was largely ignored by scientists
instead of being heralded as a classic.
Well, this is the book.
It's Carnot's only publication.
"Reflections on the Motive Power of Fire" of 1824,
a small book, 118 pages only,
published just 600 copies,
and in his own lifetime, it's virtually unknown.
Twenty years after the publication,
William Thompson, the Scottish physicist,
is absolutely intent on finding a copy.
He's here in Paris, and the accounts we have suggest
that he spends a great deal of time
visiting bookshops, visiting the bouquinistes
on the banks of the Seine
looking, always asking for the book,
and the booksellers tell him they've never even heard of it.
Back then, William Thompson, who would later become Lord Kelvin,
a giant in this new field of thermodynamics,
was impressed by Carnot's idea that the movement of heat
produced useful work in the machine.
But when he returned home,
he heard about an alternative theory
from a Manchester brewer called James Joule.
Joule had this notion that Carnot was wrong,
that heat wasn't producing work just by its movement.
Heat was actually turning into mechanical work,
which is a very strange idea when you think about it.
We're all now used to thinking about energy
and how it can take all different forms,
but it was a revolutionary idea
that heat and something like mechanical energy
were, at bottom, the same kind of thing.
The experiment that convinced Joule of this
was set up in the cellar of his brewery.
It converted mechanical movement into heat,
almost like a steam engine in reverse.
He used falling weights
to drive paddles around the drum of water.
The friction from this process
generated a minute amount of heat.
Only brewers had thermometers accurate enough
to register this tiny temperature increase
caused by a measured amount of mechanical work.
Joule's work mattered because it was the first time
that anyone had convincingly measured
the exchange rate between movement and heat.
He proved the existence of something
that converts between heat and motion.
That something was going to be called "energy"
and it's for that reason that the basic unit of energy
in the new International System of Units
is named after him: the Joule.
This apparent contradiction between Joule and Carnot
was eventually resolved by Thomson
in what would later become known as "the laws of thermodynamics".
The first law, from Joule's work, states
that, "Energy can be converted from one form to another,
but can never be created or destroyed."
The 2nd law, from Carnot's theory, states that,
"Heat flows in one direction only, from hot to cold."
In the 2nd half of the 19th century,
this new concept of energy paved the way for steam power
to artificially produce cold.
The flow of heat, from hot to cold,
drives any refrigeration cycle
whether it's a modern fridge
or a steam powered ice-making machine.
In the first stage of this cycle,
gigantic pistons compress ammonia gas into a hot liquid.
The hot liquified ammonia is pumped into a condenser
where it is cooled
and fed into pipes beneath the water tanks.
In the next stage the liquid ammonia re-evaporates,
and the temperature drops.
As the ammonia re-absorbs heat from the surrounding water,
gradually, the tanks of water become blocks of ice.
By the 1880's, many towns across America
had ice plants like this one,
which could produce 150 tons of ice a day.
For the first time, artificially produced ice
was threatening the natural ice trade
created by Frederic Tudor.
America's appetite for ice was insatiable.
Slaughterhouses, breweries,
and food warehouses, all needed ice.
Animals were disassembled on production lines in Chicago
and the meat was loaded into ice-cooled boxcars
to be shipped by railroad.
Livestock on its way
to the great meat-packing centers of the nation,
to markets everywhere.
Food of every sort
safely and quickly delivered in refrigerator cars.
From New York to Los Angeles
restaurants were able to serve
thousands of miles from where their meals once roamed.
As fruit and vegetables became available out of season,
urban diets improved, making city dwellers
the best-fed people in the world.
And to keep everything fresh at home,
the iceman made his weekly delivery
to recharge the refrigerator.
(Tom Schachtman) Refrigeration makes a tremendous difference in people's lives.
First of all, in the diet,
what is possible for them to eat.
They can go to the store once a week.
They don't have to go every day.
They can obtain at that store
foods that are from almost anywhere in the world
that have been transported and kept cool,
and then they can keep them in their own home.
Eventually the iceman disappeared
as more and more households bought electric fridges.
These used the same basic principles
as the old ice-making machines.
Heat from the food inside
is drained away by the evaporating coolant
and is dumped, at the back.
The electric pump drives this cycle
of compression, evaporation and condensation.
And that's how the fridge got its hum.
The electric power companies loved refrigerators
because they ran all day and all night.
They may not have used that much power for each hour,
but they continued to use that.
So one of the ways that they sold rural electrification
was the possibility of having your own refrigerator.
In the early days,
the fridge's icebox was used to freeze water, nothing else.
Freezing was seen as having
the same damaging effects as frost.
The man who would change this idea forever
was a scientist and explorer called Clarence Birdseye.
In 1912, Birdseye set off on an expedition to Labrador,
and the temperature dropped to 40 degrees below freezing.
The Inuit had taught Birdseye how to ice fish.
He cut a hole down in the ice which could be several feet thick,
the fish were on the pool and lined down below,
bring the fish up.
And as he did that,
he found that they'd freezed in this terribly cold air,
almost before they hit the shoulder.
(Tom Schachtman) When you went to cook this fish,
it tasted just as good as if fresh,
and he couldn't figure that out,
because when he froze fish at home,
they would taste terrible.
So when he got back home,
he finally tried to figure out what was the difference
between this quick freezing and the usual freezing.
Under closer examination,
he could see what was happening to the fish cells.
With slow freezing, large ice crystals formed,
which distorted and ruptured the cells.
When thawed, the tissue collapsed
and all the nutrients and flavor washed away.
That's the "mushy strawberry" syndrome.
A people's fruit, the freezed strawberries
that they picked in their garden,
and they put them out on the table the next day
and they, they're collapsed, they're all mushy.
But with fast freezing,
only tiny ice crystals were formed inside the cells,
and these caused little damage.
It was all down to the speed of the freezing zone.
What Birdseye found out is that you can get through this zone very quickly:
flash freezing or quick freezing.
You'll avoid this ice crystalization.
And that made it possible for the food, when it's unfrozen and cooked,
to taste just as good as fresh.
The basic concept was simple, but it took Clarence Birdseye
another 10 years to perfect
a commercial fast-freezing technique
that would mimic the natural process he'd experienced in Labrador.
In 1924, he opened a flash freezing plant
in Gloucester, Massachusetts
that froze freshly landed fish at minus 45 degrees.
He then extended that to all sorts of other kinds of meats
and products and vegetables and almost single-handedly
invented the frozen food industry.
Fridges and freezers would eventually become icons of modern living,
but there was a less visible cold transformation
happening at the same time.
This would also have a huge impact on urban living:
the cooling of the air itself.
Three centuries had passed since Cornelius Drebbel
had shaken King James in Westminster.
Now at the dawn of the 20th century,
air cooling was about to shake the world.
Tell me, what is the low down on this air-conditioning thing?
Now you've started something by asking me that.
Air-conditioning was about to transform America,
and the person responsible was Willis Carrier,
whose important breakthrough passed into comfort cooling mythology.
Let's go back to that foggy night,
when the young engineer named Willis Carrier
sought the answer to a problem.
The effects of humidity, of moist air, on industrial production.
"Fog! Maybe that's the answer.
Let's see.
Fog is water vapour, that's been condensed.
That's because the air has become cooler
and cool air can't hold as much moisture as warm air.
Maybe that's the way to reduce humidity.
Cool the air and condense the moisture.
It might work."
Control the humidity through control the temperature.
That was Willis Carrier's idea.
(Marsha Ackermann) Carrier is sent to Brooklyn for a very special job in 1902.
The company that publishes the magazine "Judge",
one of the most popular full-color magazines in America
at this particular time, is having a huge problem.
It's July in Brooklyn and the ink which they use
on their beautiful covers is sliding off the pages.
It will not stick because the humidity is too high.
Carrier, using some principles that he's been developing
as a young new employee of this fan company, finds a way
to get out the July 1902 run of the "Judge" magazine,
and from there he begins
to eventually build his air-conditioning empire.
The demand for air-conditioning gradually grew.
In the 1920's, movie houses
were among the first to promote the benefits.
People would flock there in summer to shelter from the heat.
(Marsha Ackermann) The movies are wildly popular, and the air-conditioning
certainly helps to attract an audience,
especially if they happen to be walking down the street
on a horribly hot day and they duck into this movie theater
and have this wonderful experience.
Air-conditioning became increasingly common in the workplace too,
particularly in the South, where textile and tobacco factories
were almost unbearable without cooling.
(man) When employees breath good air and feel comfortable,
they work faster and do a better job.
I think some people think
that these were nice compassionate employers
who were cooling down the workplace for the workers,
but of course, nothing could be further from the truth.
That was an inadvertent by-product,
but actually this was a quality control device
to control the breaking of fibers in cotton mills
to get consistent quality control in these various industries
to control the dust that had bedeviled
tobacco stemming room workers for decades.
I mean, I think the workers obviously went home
and to their unair-conditioned shacks in most cases
and talked about how nice and cool it was working during the day.
Well, as anybody will tell you who's lived here for very long.
Even today, on the age of the air conditioning
we've so plenty of sun and sweat and humidity
it's something you just have to deal with.
It's silly to suffer from the heat
when you can afford the modest cost of air-conditioning.
By the 1950's, people were air-conditioning their homes
with stand-alone window units that could be easily installed.
This wasn't just an appliance;
it offered a new, cool way of life.
(Raymond Arsenault) Walking down a typical Southern street
prior to the air-conditioning revolution,
you would have seen families, individuals, outside.
They would have been on their porches,
on each other's porches.
There was a visiting tradition, a real sense of community.
Well, I think all that changes with air-conditioning.
You walk down that same street and basically what you'll hear
are not the voices of people talking on the porch;
you'll hear the whirr of the compressors.
Guess what we've got!
An RCA room air conditioner.
I'm a woman, and I know how much pure air means to mother
in keeping our rooms clean and free from dust and dirt.
Control of the cold has transformed city life.
Refrigeration helped cities expand outwards
by enabling large numbers of people
to live at great distances from their source of food.
Air-conditioning enabled cities to expand upwards.
Beyond 20 stories, high winds make open windows impractical,
but with air-conditioning,
100-story skyscrapers were possible.
(Simon Schaffer) Technologies emerged,
which not only worked
to insulate human society against the evils of cold,
but turned cold into a productive,
manageable, effective resource.
On the one hand, the steam engine;
on the other, the refrigerator,
those 2 great symbols of 19th-century world,
which completely changed the society and economy of the planet.
All that is part of, I think,
what we could call bringing cold to market.
Turning it from an evil agent that you feared
into a force of nature from which you could profit.
The explosive growth of the modern world
over the last two centuries
owes much to the conquest of cold.
But this is only the beginning
of the journey down the temperature scale.
Going lower would be even harder,
but would produce greater wonders
that promise extraordinary innovations for the future.
With rival scientists racing towards the final frontier,
the pace quickens and the molecular dance slows
as they approach the Holy Grail of cold: absolute zero.