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Documentary, Absolute Zero - Part 1 of 2 - The Conquest of Cold
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00:00The greatest triumph of civilization is often seen as our mastery of heat.
00:09Yet our conquest of cold is an equally epic journey from dark beginnings to an ultra-cool frontier.
00:20For centuries, cold remained a perplexing mystery with no obvious practical benefits.
00:27Yet in the last hundred years, cold has transformed the way we live and work.
00:39Imagine supermarkets without refrigeration, skyscrapers without air conditioning,
00:45hospitals without MRI machines and liquid oxygen.
00:49We take for granted the technology of cold, yet it has enabled us to explore outer space
00:55and the inner depths of our brain.
00:59And as we develop new ultra-cold technology to create quantum computers and high-speed networks,
01:05it will change the way we work and interact.
01:11How did we harness something once considered too fearsome to even investigate?
01:18How have scientists and dreamers over the past four centuries plunged lower and lower down the temperature scale
01:26to conquer the cold and reach its ultimate limit,
01:30a holy grail as elusive as the speed limit of light?
01:35Absolute Zero.
01:38Up next on NOVA.
02:05Extreme cold has always held a special place in our imagination.
02:15For thousands of years, it seemed like a malevolent force associated with death and darkness.
02:22Cold was an unexplained phenomenon.
02:25Was it a substance, a process, or some special state of being?
02:30Back in the 17th century, no one knew, but they certainly felt its effects in the freezing London winters.
02:4017th century England was in the middle of what's now called the Little Ice Age.
02:44It was fantastically cold by modern standards.
02:46You have to imagine a world lit by fire in which most people are cold most of the time.
02:51Cold would have felt like a real presence, a kind of positive agent that was affecting how people felt.
02:59Back then, people felt at the mercy of cold.
03:04This was a time when such natural forces were viewed with awe as acts of God.
03:10So anyone attempting to tamper with cold did so at his peril.
03:15The first to try was an alchemist, Cornelius Drebbel.
03:20On a hot summer's day in 1620, King James I and his entourage arrived to experience an unearthly event.
03:33Drebbel, who was also the court magician, had a wager with the king that he could turn summer into winter.
03:40He would attempt to chill the air in the largest interior space in the British Isles, the Great Hall of Westminster.
03:52Drebbel hoped to shake the king to his core.
03:59He had a phenomenally fertile mind. He was an inventor par excellence.
04:04His whole world was steeped in a world of alchemy, of perpetual motion machines, of the idea of time, space, planets, moon, sun, gods.
04:14He was a fervently religious man.
04:16He was a person for whom nature presented a phenomenal galaxy of possibilities.
04:24Dr. Andrew Shidlow, a chemist with a lifelong fascination for Drebbel, enjoys his reincarnation as the great court magician.
04:36Like most alchemists, Drebbel kept his method secret.
04:40Dr. Shidlow wants to test his ideas on how Drebbel created artificial cold.
04:47When Drebbel was trying to achieve the lowest temperature possible, he knew that ice, of course, was the freezing point, the coldest you could get normally.
04:59But he would have been aware of the fact, through his experience, that mixing ice with different salts could get you a colder temperature.
05:06Salt will lower the temperature at which ice melts.
05:10Dr. Shidlow thinks Drebbel probably used common table salt, which gives the biggest temperature drop.
05:18But salt and ice alone would not be enough to cool the air within such a large interior.
05:25Drebbel was famous for designing elaborate contraptions, a passion shared by Dr. Shidlow, who has an idea for the alchemist's machine.
05:35So here, we would have had a fan, which would have been turned over, blowing warm air over the cold vessels there.
05:45And as the air blows over these cold jars, we would have had, in effect, the world's first air conditioning unit.
05:56But could this really turn summer into winter?
06:00The idea is to stir it in as well as possible in the five seconds that you have to do it.
06:08Dr. Shidlow stacks the jars of freezing mixture to create cold corridors for the air to pass through.
06:15You can feel it's very cold.
06:22In fact, I could feel cold air actually falling on my hands because cold air, of course, is denser than warm air.
06:30And one can feel it quite clearly on the fingers.
06:32The vital question, would the gust of warm air become cold?
06:40Woof, I can feel certainly a blast of cold air hitting me as that second cover was released.
06:53Well, temperature, we're on 14 at the moment.
06:56Yes, keep it going. That's definitely the right direction.
07:01King James would have been shaken by his encounter with man-made cold.
07:08Had Drebbel written up his great stunt, he might have gone down in history as the inventor of air conditioning.
07:16Yet it would be almost three centuries before this idea would actually take off.
07:22To advance knowledge and conquer the cold required a very different approach, the scientific method.
07:35The fundamental question, what is cold, haunted Robert Boyle nearly 50 years later.
07:41The son of the Earl of Cork, a wealthy nobleman, Boyle used his fortune to build an extensive laboratory.
07:49Boyle is famous for his experiments on the nature of air, but he also became the first master of cold.
08:01Believing it to be an important but neglected subject, he carried out hundreds of experiments.
08:08He worked through, very systematically, a series of ideas about what cold is.
08:16Does it come from the air? Does it come from the absence of light?
08:22Is it that there are strange, so-called frigorific cold-making particles?
08:30In Boyle's day, the dominant view was that cold is a primordial substance that bodies take in as they get colder and expel as they warm up.
08:44It was this view that Boyle would eventually overturn by a set of carefully devised experiments on water.
08:51First, he carefully weighed a barrel of water and took it outside in the snow, leaving it to freeze overnight.
09:04Boyle was curious about the way water expanded when it turned to ice.
09:09He reasoned that if once the water turned to ice, the barrel weighed more, then perhaps cold was a substance after all.
09:20But when they re-weighed the barrel, they discovered it weighed exactly the same.
09:28So what must be happening, Boyle guessed, was that the particles of water were moving further apart.
09:35And that was the expansion, not some substance flowing into the barrel from outside.
09:45Boyle was becoming increasingly convinced that cold was not a substance, but something that was happening to individual particles.
09:53And he began to think back to his earlier experiments with air.
09:58As matter-like air becomes warmer, it tends to expand.
10:03Boyle imagined the air particles were like tiny springs, gradually unwinding and taking up more space as they heat up.
10:14Boyle's conclusion here was that heat is a form of motion of a particular kind.
10:21And that as bodies cool down, they move less and less.
10:28Boyle's longest published book was on the cold.
10:32Yet he found its study troublesome and full of hardships.
10:37Declaring that he felt like a physician trying to work in a remote country without the benefit of instruments or medicines.
10:46To properly explore this country of the cold, Boyle lamented the lack of a vital tool, an accurate thermometer.
10:55It was not until the mid-17th century that glassblowers in Florence began to produce accurately calibrated thermometers.
11:04Now it became possible to measure degrees of hot and cold.
11:10Like the air in Boyle's experiment, heat makes most substances expand.
11:25Early thermometers used alcohol, which is lighter than mercury and expands much more with heat.
11:35So these Florentine thermometers were sometimes several meters long and often wound into spirals.
11:42But there was still one major problem with all thermometers.
11:47The lack of a universally accepted temperature scale.
11:51There are all kinds of different ways of trying to stick numbers to these degrees of hot and cold.
11:58And they, on the whole, didn't agree with each other at all.
12:02So one guy in Florence makes one kind of thermometer.
12:07Another guy in London makes a different kind.
12:10And they just don't even have the same scale.
12:14And so there was a lot of problem in trying to standardize thermometers.
12:21The challenge was to find events in nature that always occur at the same temperature and make them fixed points.
12:29At the lower end of the scale, that might be ice, just as it begins to melt.
12:34At the upper end, it could be wax, heated to its melting point.
12:39The first temperature scale to be widely adopted was devised by Gabriel Daniel Fahrenheit, a gifted instrument maker who made thermometers for scientists and physicians across Europe.
12:54He had several fixed points.
12:56He used a mixture of ice, water and salt for his zero degrees.
13:01Ice melting in water at 32 degrees.
13:04And for his upper fixed point, the temperature of the human body at 96 degrees, which is close to the modern value.
13:13One of the things that Fahrenheit was able to achieve was to make thermometers quite small.
13:19And that he did by using mercury, as opposed to alcohol or air, which other people had used.
13:26And 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.
13:37So the fact that he could make them small and convenient, that seems to be what made Fahrenheit so famous and so influential.
13:47It was a Swedish astronomer, Anders Celsius, who came up with the idea of dividing the scale between two fixed points into 100 divisions.
13:58But the original scale used by Celsius was upside down.
14:03So 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.
14:14And this is another little mystery in the history of the thermometer that we just don't know for sure.
14:22What was he thinking when he labelled it this way?
14:26And it was the botanist Linnaeus, who was then the president of the Swedish Academy, who after a few years said,
14:35we need to stop this nonsense and inverted the scale to give us what we now call Celsius scale today.
14:43A question nobody thought to ask when devising temperature scales was, how low can you go?
14:54Is there an absolute lower limit of temperature?
14:58The idea that there might be would become a turning point in the history of cold.
15:04The story begins with the French physicist Gyo Mamoto.
15:10He was doing experiments heating and cooling bodies of air to see how they expand and contract.
15:19A montant heated air in a glass bulb by placing it in hot water.
15:25Just like a hot air balloon, the air in the glass bulb expanded as the increased pressure forced a column of mercury up the tube.
15:35Then he tried cooling the air.
15:40He was noticing that, well, when you cool a body of air, the pressure would go down.
15:46And he speculated, well, what would happen if we just kept cooling it?
15:51By plotting this falling temperature against pressure, a montant saw that as the temperature dropped, so did the pressure.
15:59And this gave him an extraordinary idea.
16:03A montant started to consider the possibility what would happen if you projected this line back until the pressure was zero.
16:11And this was the first time in this course of history that people have actually considered the concept of an absolute zero of temperature.
16:20Zero pressure, zero temperature.
16:23It was quite a revolutionary idea when you think about it because you wouldn't just think that temperature has a limit of a lower bound or zero.
16:35Because in the upper end it can go on forever, we think, until it's hotter and hotter and hotter.
16:42But somehow, maybe there's a zero point where this all begins.
16:48So you could actually give a calculation of where this zero point would be.
16:55A montant didn't do that calculation himself, but some other people did later on.
17:00And when you do it, you get a value that's actually not that far from the modern value of roughly minus 273 centigrade.
17:11In one stroke, a montant had realized that although temperatures might go on rising forever, they could only fall as far as this absolute point, now known to be minus 273 degrees centigrade.
17:25For him, this was a theoretical limit, not a goal to attempt to reach.
17:30Before scientists could venture towards this zero point, far beyond the coldest temperatures on Earth, they needed to resolve a fundamental question.
17:42By now, most scientists defined cold simply as the absence of heat.
17:48But what was actually happening as substances warmed or cooled was still hotly debated.
17:55The argument of men like a montant 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.
18:10Unfortunately, the science of cold was about to suffer a serious setback.
18:17The idea that cooling was caused by particles slowing down began to go out of fashion.
18:24At the end of the 18th century, a rival theory of heat and cold emerged that was tantalizingly appealing, but completely wrong.
18:34It was called the caloric theory, and its principal advocate was the great French chemist, Antoine Lavoisier.
18:47Like most scientists of the time, Lavoisier was a rich aristocrat who funded his own research.
18:53He and his wife, Madame Lavoisier, who assisted with his experiments, even commissioned the celebrated painter David to paint their portrait.
19:03He carried out experiments to support the erroneous idea that heat was a substance, a weightless fluid that he called caloric.
19:16He thought in the solid state of matter, molecules were just packed close in together.
19:22And when you added more and more caloric to this, the caloric would insinuate itself between these particles of matter and loosen them up.
19:32So the basic notion was that caloric was this fluid that was, as he put it, self-repulsive.
19:40It just tended to break things apart from each other.
19:44And that's his basic notion of heat. So cold is just the absence of caloric or the relative lack of caloric.
19:54Lavoisier even had an apparatus to measure caloric, which he called a calorimeter.
20:02He packed the outer compartment with ice.
20:05Inside, he conducted experiments that generated heat, sometimes from chemical reactions, sometimes from animals, to determine how much caloric was released.
20:15He collected the water from the melting ice and weighed it to calculate the amount of caloric generated from each source.
20:27I 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.
20:41Indeed, for Lavoisier, it's an element like oxygen or nitrogen. Oxygen gas is made of oxygen plus caloric.
20:53And if you take the caloric away, presumably the oxygen might liquefy.
20:57It's a very hard model to shift because it explains so much.
21:02And indeed, Lavoisier's chemistry was so otherwise extraordinarily successful.
21:07However, Lavoisier's story about caloric was soon undermined.
21:12But there was one man who was convinced Lavoisier was wrong and was determined to destroy the caloric theory.
21:22His name was Count Rumford.
21:33Count Rumford had a colorful past.
21:36He was born in America, spied for the British during the Revolution,
21:40and after being forced into exile, became an influential government minister in Bavaria.
21:46Among his varied responsibilities was the artillery works.
21:52And 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.
22:01Rumford had noticed that the friction from boring out a cannon barrel generated a lot of heat.
22:11He decided to carry out experiments to measure how much.
22:16He adapted the machine to produce even more heat by installing a blunt borer that had one end submerged in a jacket of water.
22:26As the cannon turned against the borer, the temperature of the water increased and eventually boiled.
22:33The longer he bored, the more heat was produced.
22:38For Rumford, what this showed was that heat must be a form of motion, and heat is not a substance,
22:46because you could generate indefinitely large amounts of heat simply by turning the cannon.
22:54Despite Count Rumford's best efforts, Lavoisier's caloric theory remained dominant until the end of the 18th century.
23:03His prestige as a chemist meant that few dared challenge his ideas.
23:09But this did not protect him from the revolutionary turmoil in France, which was about to interrupt his research.
23:16At the height of the reign of terror, Lavoisier was arrested and eventually lost his head.
23:23Once he was guillotined, his wife left France and eventually met Rumford.
23:30When he moved to Western Europe in the early 1800s, Rumford then married her.
23:36So he'd married the widow of the man who'd founded the theory that he'd destroyed.
23:41The marriage was short-lived.
23:44After a tormented year, Rumford left Madame Lavoisier and devoted the rest of his life to his first love, science.
23:52It would be nearly 50 years before Rumford's idea that temperature is simply a measure of the movement of particles was accepted.
24:02With heat, the particles, what we now know as atoms, speed up.
24:08And with cold, they slow down.
24:18Rumford's dedication to science led him to become a founder of the Royal Institution in London.
24:23And it was here that the next major breakthrough in the conquest of cold would occur.
24:29Michael Faraday, who later became famous for his work on electricity and magnetism, would take a critical early step in the long descent towards absolute zero when he was asked to investigate the properties of chlorine using crystals of chlorine hydrate.
24:48This experiment was potentially explosive, which is perhaps why it was left to Faraday, and perhaps also why Dr. Andrew Shidlow is curious to repeat it today.
25:00We are about to undertake an exceedingly dangerous experiment in which Michael Faraday in 1823 heated this substance here, the hydrate of chlorine, in a sealed tube.
25:12Is that sealed?
25:16That's sealed, Andrew.
25:18That's absolutely brilliant.
25:20In the original experiment, Faraday took the sealed tube and heated the end containing the chlorine hydrate in hot water.
25:28He put the other end in an ice bath.
25:32Soon, he noticed yellow chlorine gas being given off.
25:37Because the grass is being produced, pressure is building up.
25:41Ray, this is where it starts to get dangerous.
25:45So if you now take a few steps back.
25:49When Faraday did the experiment, a visitor, Dr. Paris, came by to see what he was up to.
25:57Paris pointed out some oily matter in the bottom of the tube.
26:01Faraday was curious and decided to break open the tube.
26:07Right, so let's have a look inside here.
26:13The explosion sent shards of glass flying.
26:19With the sudden release of pressure, the oily liquid vanished.
26:29And there we are.
26:30Is that what happened?
26:31Yeah, that's exactly what happened.
26:32It popped open, glass flew.
26:36And can you detect the strong smell of chlorine?
26:38I can now.
26:39Absolutely well.
26:40He detected the strong smell of chlorine, and this was a major mystery for him.
26:46Faraday soon realized the increased pressure inside the sealed tube had caused the gas to liquefy.
26:55And when the tube was broken, the oily liquid evaporated.
26:59Just as heat must be applied to evaporate water, he saw that energy from the surrounding air had transformed liquid chlorine into a gas.
27:09In a brilliant deduction, Faraday realized that by absorbing heat from the air, he had cooled or refrigerated the surroundings.
27:20Michael Faraday had produced cold.
27:26Later, he used the same technique with ammonia, which absorbs even more heat.
27:31He predicted that one day this cooling might be commercially useful.
27:40Faraday took no interest in commercial exploitation.
27:46But across the Atlantic, a Yankee entrepreneur had a very different philosophy.
27:53Frederick Tudor had a chance conversation with his brother that led him on a path to become one of the richest men in America.
28:08The 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.
28:14And certainly there was a lot of rocks, but people weren't going to pay for that.
28:18So they came up with the idea of maybe ice, because some areas did not have ice.
28:22And it seemed kind of crazy at first, but it paid off.
28:27When Tudor began harvesting ice from New England ponds, he soon realized he needed specialized tools to keep up with the huge demand.
28:37We had the saws, and the saws were an improvement over the old wood saws.
28:43They have teeth that are sharpened on both sides and set, so it cuts on both the up and the down stroke.
28:52The crew could clear a three-acre pond easily in a couple of days.
29:04Tudor's dream to make ice available to all was not confined to New England.
29:09He wanted to ship ice to hot parts of the world, like the Caribbean and the Deep South.
29:16When Tudor first tried to convince shipmasters to put his load of frozen water into the ships,
29:22they all refused, because they told them that water belonged outside the hole, not inside.
29:26So he had to go find other investors to get the money to buy his own ship.
29:31And he bought a ship by the name of The Favourite.
29:38New England became the refrigerator for the world, with ice shipments to the Caribbean, the coast of South America and Europe.
29:46Tudor even reached India and China.
29:50Watching the ice cutter's 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.
30:05Tudor, 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.
30:18During the latter half of the 19th century, the ice industry eventually employed tens of thousands of people.
30:32Tudor became the largest distributor of ice, and he became one of the first American millionaires.
30:39And we're talking about one of his ships going to the Caribbean, giving him a profit of $6,000.
30:45Now this is in a time period when people were earning $200 to $300 a year, the average family.
30:51So someone earning thousands of dollars was just inconceivable.
30:54And that would be losing 20% of your ice when it got there.
30:58There was still huge amounts of profit.
31:03Tudor's success was based on an extraordinary physical property of ice.
31:07It takes the same amount of heat to melt a block of ice as it does to heat an equivalent quantity of water
31:14to around 80 degrees Celsius.
31:17This meant that ice took a long time to melt, even when shipped to hotter climates.
31:31What started out as a small family enterprise turned into a global business.
31:36Frederick Tudor had industrialized cold in the same way the great pioneers of steam had harnessed heat.
31:47By the 1830s, the Industrial Revolution was in full swing.
31:53Yet ironically, it was not until a small group of scientists worked out the underlying principles of how steam engines convert heat into motion,
32:01that the next step in the conquest of cold could be made.
32:06Only after solving this riddle of heat engines could the first cold engines be made to produce artificial refrigeration.
32:20How much useful work can you get out of a given amount of heat?
32:24By the early 1800s, that had become the single most important economic problem in Europe.
32:36To make a profit was to convert heat into motion efficiently, without wasting heat and getting the maximum amount of mechanical effect.
32:46The first person to really engage with this problem was a young French artillery engineer, Sadi Carnot.
33:01He thought that improving the efficiency of steam engines might help France's flagging economy after defeat at Waterloo in 1815.
33:07Working at the Conservatoire des Arts et Métiers, he began to analyze how a steam engine was able to turn heat into mechanical work.
33:21In steam engines, it looks as though heat is flowing around the engine.
33:28And as it flows, the engine does mechanical work.
33:32The implication there is that heat is neither consumed nor destroyed.
33:43You simply circulate it around and it does work.
33:47Carnot likened this flow of heat to the flow of water over a water wheel.
33:53He saw that the amount of mechanical work produced depended on how far the water fell.
34:00His 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.
34:16The greater the temperature difference, the more work was produced.
34:21Carnot distilled these profound ideas into an accessible book for general readers,
34:27which meant it was largely ignored by scientists instead of being heralded as a classic.
34:34Well, this is the book. It's Carnot's only publication, Reflections on the Motive Power of Fire of 1824.
34:42A small book, 118 pages only, published just 600 copies, and in his own lifetime it's virtually unknown.
34:50Twenty years after the publication, William Thomson, the Scottish physicist, is absolutely intent on finding a copy.
35:00He's here in Paris, and the accounts we have suggest that he spends a great deal of time visiting bookshops,
35:07visiting the bouquiniste on the banks of the Seine, looking, always asking for the book, and the booksellers tell him they've never even heard of it.
35:18William Thomson, who would later become Lord Kelvin, a giant in this new field of thermodynamics,
35:31was impressed by Carnot's idea that the movement of heat produced useful work in the machine.
35:37But when he returned home, he heard about an alternative theory from a Manchester brewer called James Jewell.
35:45Jewell had this notion that Carnot was wrong, that heat wasn't producing work just by his movement.
35:55Heat was actually turning into mechanical work, which is a very strange idea when you think about it.
36:02We're all now used to thinking about energy and how it can take all different forms.
36:06But it was a revolutionary idea that heat and something like mechanical energy were at bottom the same kind of thing.
36:19The experiment that convinced Jewell of this was set up in the cellar of his brewery.
36:25It converted mechanical movement into heat, almost like a steam engine in reverse.
36:30He used falling weights to drive paddles around the drum of water.
36:41The friction from this process generated a minute amount of heat.
36:48Only brewers had thermometers accurate enough to register this tiny temperature increase caused by a measured amount of mechanical work.
36:56Jules' work mattered because it was the first time that anyone had convincingly measured the exchange rate between movement and heat.
37:10He proved the existence of something that converts between heat and motion.
37:21That something was going to be called energy.
37:25And it's for that reason that the basic unit of energy in the new international system of units is named after him, the Joule.
37:33Joule and Carnot's ideas were combined by Thompson to produce what would later be known as the laws of thermodynamics.
37:44The first law from Joule's work states that energy can be converted from one form to another, but can never be created or destroyed.
37:55The second law from Carnot's theory states that heat flows in one direction only, from hot to cold.
38:05In the second half of the 19th century, this new understanding paved the way for steam power to artificially produce ice.
38:27Ice-making machines like this one were based on principles discovered by Michael Faraday, who showed when ammonia changes from a liquid to a gas, it absorbs heat from its surroundings.
38:42It's part of what is now known as a refrigeration cycle.
38:46In the first stage of this cycle, gigantic pistons compress ammonia gas into a hot liquid.
38:57The hot liquefied ammonia is pumped into condenser coils, where it's cooled and fed into pipes beneath giant water tanks.
39:08Then the pressure is released, and the liquid ammonia evaporates, absorbing heat from the surrounding water.
39:22Gradually, the tanks of water become blocks of ice.
39:27By the 1880s, many towns across America had ice plants like this one, which could produce 150 tons of ice a day.
39:43For the first time, artificially produced ice was threatening the natural ice trade created by Frederick Tudor.
39:50America's appetite for ice was insatiable.
39:57Slaughterhouses, breweries, and food warehouses all needed ice.
40:03Animals were disassembled on production lines in Chicago, and the meat was loaded into ice-cooled boxcars to be shipped by railroad.
40:11Livestock on its way to the great meat-packing centers of the nation, to markets everywhere.
40:18Food of every sort, safely and quickly delivered in refrigerator cars.
40:27As fruit and vegetables became available out of season, urban diets improved, making city dwellers the best-fed people in the world.
40:36And to keep everything fresh at home, the Iceman made his weekly delivery to recharge the refrigerator.
40:49Refrigeration makes a tremendous difference in people's lives.
40:52First of all, on the diet, what is possible for them to eat.
40:55They can go to the store once a week. They don't have to go every day.
40:59They can obtain at that store foods that are from almost anywhere in the world that have been transported and kept cool.
41:05And then they can keep them in their own home.
41:08Eventually, the Iceman disappeared as more and more households bought electric refrigerators.
41:15These used the same basic principles as the old ice-making machines.
41:21Liquid ammonia circulating in pipes evaporates, draining the heat away from the food inside.
41:26Compressed by an electric pump, the gas is condensed back into liquid ammonia, and the cycle begins again.
41:36The electric power companies loved refrigerators because they ran all day and all night.
41:43They may not have used that much power for each hour, but they continued to use that.
41:46So, one of the ways that they sold rural electrification was the possibility of having your own refrigerator.
41:54In the early days, the freezer was used to freeze water, nothing else.
41:59Freezing was seen as having the same damaging effects as frost.
42:03The man who would change this idea forever was a scientist and explorer named Clarence Birdseye.
42:16In 1912, Birdseye set off on an expedition to Labrador, and the temperature dropped to 40 degrees below freezing.
42:27The Inuit had taught Birdseye how to ice fish by cutting a hole in the ice several feet thick.
42:44When he caught a fish, he found it froze almost as soon as it hit the air.
42:49This process seemed to preserve the fish in a unique way.
42:52When you went to cook this fish, it tasted just as good as it fresh.
43:01And he couldn't figure that out because when he froze fish at home, they would taste terrible.
43:07So, when he got back home, he finally tried to figure out what was the difference between this quick freezing and the usual freezing.
43:13Under closer examination, he could see what was happening to the fish cells.
43:24With slow freezing, large ice crystals formed, which distorted and ruptured the cells.
43:32When thawed, the tissue collapsed and all the nutrients and flavor washed away.
43:36The so-called mushy strawberry syndrome.
43:41But with fast freezing, only tiny ice crystals were formed inside the cells, and these caused little damage.
43:49It was all down to the speed of the freezing process.
43:53A simple concept, 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.
44:06In 1924, he opened a flash freezing plant in Gloucester, Massachusetts, that froze freshly landed fish at minus 45 degrees.
44:20He then extended that to all sorts of other kinds of meats and produce and vegetables, and almost single-handedly invented the frozen food industry.
44:30Refrigerators and freezers would eventually become icons of modern living.
44:34But there was a less visible cold transformation happening at the same time.
44:40This would also have a huge impact on urban life.
44:44The cooling of the air itself.
44:48Three centuries had passed since Cornelius Drebbel had shaken King James in Westminster.
44:54Now, at the dawn of the 20th century, air cooling was about to shake the world.
44:59Tell me, what is the lowdown on this air conditioning thing?
45:04Ah, you've started something by asking me that.
45:11Air conditioning was about to transform modern life, and the person largely responsible was Willis Carrier, who started off working for a company that made fans.
45:21Carrier is sent to Brooklyn for a very special job in 1902.
45:32The 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.
45:44It's July in Brooklyn, and the ink for which they use on their beautiful covers is sliding off the pages.
45:54It will not stick because the humidity is too high.
45:57Carrier, 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.
46:11And from there, he begins to eventually build his air conditioning empire.
46:18It's based on a simple principle.
46:21Control of humidity through control of temperature. That was Willis Carrier's idea.
46:27He used refrigeration to cool the water vapor in the humid air.
46:32The vapor condensed into droplets, leaving the air dry and cool.
46:36The demand for air conditioning gradually grew.
46:43In the 1920s, movie houses were among the first to promote the benefits.
46:48People would flock there in summer to escape the heat.
46:50The 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.
47:06Air conditioning became increasingly common in the workplace, too, particularly in the south, where textile and tobacco factories were almost unbearable without cooling.
47:20When employees breathe good air and feel comfortable, they work faster and do a better job.
47:26I 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.
47:36That was an inadvertent byproduct, 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.
47:59I think the workers obviously went home to their un-air-conditioned shacks, in most cases, and talked about how nice and cool it was working during the day.
48:13It's silly to suffer from the heat when you can afford the modest cost of air conditioning.
48:19By the 1950s, people were air conditioning their homes with stand-alone window units that could be easily installed.
48:27This wasn't just an appliance. It offered a new, cool way of life.
48:44Walking down a typical southern street prior to the air conditioning revolution, you would have seen families, individuals outside.
48:53They would have been on their porches, on each other's porches. There was a visiting tradition, a real sense of community.
49:04Well, 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.
49:13Guess 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.
49:29We're free from dust and dirt.
49:39Control of the cold has transformed city life.
49:44Refrigeration helped cities expand outwards by enabling large numbers of people to live at great distances from their source of food.
49:52Air conditioning enabled cities to expand upwards.
49:59Beyond 20 stories, high winds make open windows impractical.
50:05But with air conditioning, 100-story skyscrapers were possible.
50:09technologies emerged which not only worked to insulate human society against the evils of cold, but turned cold into a productive, manageable, effective resource.
50:31On the one hand, the steam engine. On the other, the refrigerator.
50:38Those two great symbols of 19th century world, which completely changed the society and economy of the planet.
50:49All that is part of, I think, what we could call bringing cold to market.
50:53Turning it from an evil agent that you feared into a force of nature from which you could profit.
51:04The explosive growth of the modern world over the last two centuries owes much to the conquest of cold.
51:11But this was only the beginning of the journey down the temperature scale.
51:15Going lower would be even harder, but would produce greater wonders that promise extraordinary innovations for the future.
51:25With rival scientists racing toward the final frontier, the pace quickens and the molecular dance slows.
51:33As they approach the holy grail of cold.
51:38Absolute Zero.
51:54On NOVA's Absolute Zero website, enter a virtual lab and see how close you can get to Absolute Zero.
51:59Make your own temperature scale and more.
52:03Find it on PBS.org.
52:04To order this NOVA program for $24.95 plus shipping and handling, call WGBH Boston Video at 1-800-255-255-255-255-255.
52:29Call WGBH Boston Video at 1-800-255-9424.
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