But it all started 200 years ago with some giant ice cubes.
In the early summer months of 1834, a three-masted ship named the Madagascar sailed into the port of Rio de Janeiro, its hull filled with the most implausible of cargo - a frozen New England lake.
The Madagascar and her crew were in the service of an enterprising and dogged Boston businessman named Frederic Tudor.
As a well-to-do young Bostonian, Tudor’s family had long enjoyed the frozen water from the pond on their country estate, Rockwood - not just for its aesthetics, but also for its enduring capacity to keep things cold.
Like many wealthy families in northern climes, the Tudors stored blocks of frozen lake water in ice houses, 200lb (90kg) ice cubes that would remain marvellously unmelted until the hot summer months arrived, and a new ritual began. Chipping off slices from the blocks to freshen drinks, make ice cream, cool down a bath during a heat wave.
At the age of 17, Tudor’s father sent him on a voyage to the Caribbean. Suffering through the inescapable humidity of the tropics in the full regalia of a 19th Century gentleman suggested a radical - some would say preposterous - idea to young Frederic Tudor.
If he could somehow transport ice from the frozen north to the West Indies, there would be an immense market for it.
In November 1805, Tudor dispatched his brother William to Martinique as an advance guard, bought a brig called the Favorite and began harvesting ice in preparation for the journey.
In February, Tudor set sail from Boston Harbour, the Favorite loaded with a full cargo of Rockwood ice, bound for the West Indies.
“No joke,” the Boston Gazette reported.
A vessel with a cargo of 80 tons of Ice has cleared out from this port for Martinique. We hope this will not prove to be a slippery speculation.”
The Gazette’s derision would turn out to be well founded, though not for the reasons one might expect.
Despite weather-related delays, the ice survived the journey in remarkably good shape. The problem proved to be one that Tudor had never contemplated.
The residents of Martinique had no interest in his exotic frozen bounty. They simply had no idea what to do with it.
The indifference to ice’s magical powers had prevented Tudor’s brother William from lining up an exclusive buyer for the cargo.
Even worse, William had failed to establish a suitable location to store the ice.
Tudor had made it all the way to Martinique but found himself with no demand for a product that was melting in the tropical heat at an alarming rate.
The trip was a complete failure.
The bleak pattern of the Martinique voyage would repeat itself in the years to come, with ever more catastrophic results.
Tudor’s fledgling business had a demand and a storage problem. But there were also advantages.
Ships tended to leave Boston harbour empty, heading off for the West Indies to fill their hulls with valuable cargo, which meant that he could negotiate cheaper rates for transporting his ice on the otherwise empty vessels.
Furthermore, the ice itself was basically free. Tudor needed only to pay workers to carve blocks of it out of the frozen lakes.
New England’s economy generated another product that was equally worthless. Sawdust – the primary waste product of lumber mills.
After years of experimenting, Tudor discovered that sawdust made a brilliant insulator for his ice.
Blocks layered on top of each other with sawdust separating them would last almost twice as long as unprotected ice.
This was Tudor’s frugal genius. He took three things that the market had effectively priced at zero - ice, sawdust, and an empty vessel - and turned them into a flourishing business.
Tudor’s initial catastrophic trip to Martinique had made it clear that he also needed on-site storage in the tropics.
He tinkered with multiple ice house designs, finally settling on a double-shelled structure that used the air between two stone walls to keep the interior cool.
Tudor didn’t understand the molecular chemistry of it, but both the sawdust and the double-shelled architecture revolved around the same principle.
For ice to melt, it needs to pull heat from the surrounding environment to break the tetrahedral bonding of hydrogen atoms that gives ice its crystalline structure.
(The extraction of heat from the surrounding atmosphere is what grants ice its miraculous capacity to cool us down.)
The only place that heat exchange can happen is at the surface of the ice, which is why large blocks of ice survive for so long - all the interior hydrogen bonds are perfectly insulated from the exterior temperature.
Fifteen years after his original hunch, Tudor’s ice trade finally turned a profit.
By the 1820s, he had ice houses packed with frozen New England water all over the American South.
By the 1830s, his ships were sailing to Rio and Bombay. (India would ultimately prove to be his most lucrative market.)
By his death in 1864, Tudor had amassed a fortune worth more than $200m in today’s dollars. And in New York 2 out of 3 homes had a daily delivery of ice.
In less than a century, ice had gone from a curiosity to a luxury, to a necessity.
Ice-powered refrigeration began to change the map of America, nowhere more so than in the transformation of Chicago.
Its fortuitous location as a transportation hub enabled wheat to flow from the bountiful plains to the Northeast population centres.
But meat couldn’t make the journey without spoiling.
As the century progressed, a supply/demand imbalance developed between the hungry cities of the Northeast and the cattle of the Midwest.
As immigration fueled the population of New York and Philadelphia in the 1840s and 50s, the supply of local beef failed to keep up with the surging demand.
Meanwhile, the conquest of the Great Plains had enabled ranchers to breed massive herds of cattle, without a corresponding population base of humans to feed.
It was ice that ultimately provided a way around this impasse.
In 1878, Gustavus Franklin Swift hired an engineer to build an advanced refrigerator car.
Ice was placed in bins above the meat; at stops along the route, workers could swap in new blocks of ice from above, without disturbing the meat below.
“It was this application of elementary physics,” Donald Miller, in his history of 19th Century Chicago writes, “that transformed the ancient trade of beef slaughtering from a local to an international business, for refrigerator cars led naturally to refrigerator ships, which carried Chicago beef to four continents”.
Cooling the Deep South
It’s a story that begins at the scale of insects, in the town of Apalachicola, Florida, where people live alongside a swamp in a subtropical climate - the perfect environment for breeding mosquitoes.
In 1842, abundant mosquitoes meant, inevitably, the risk of malaria.
At the modest local hospital, a doctor named John Gorrie sat helpless as dozens of his patients burned up with fever.
Desperate for a way to reduce his patients’ fevers, Gorrie tried suspending blocks of ice from the hospital ceiling. It turned out to be an effective solution: the ice blocks cooled the air; the air cooled the patients.
With fevers reduced, some of his patients survived their illnesses. But then a string of shipwrecks delayed ice shipments from New England, which left Gorrie without his usual supply.
And so the young doctor began mulling over a more radical solution for his hospital - making his own ice.
Luckily for Gorrie, it happened to be the perfect time to have this idea.
For thousands of years, the idea of making artificial cold had been almost unthinkable to human civilisation. We invented agriculture and cities and aqueducts and the printing press, but cold was outside the boundaries of possibility.
And yet somehow artificial cold became imaginable in the middle of the 19th Century.
To use the wonderful phrase of the complexity theorist Stuart Kauffman, cold became part of the “adjacent possible” of that period.
How do we explain this breakthrough?
It’s not just a matter of a solitary genius coming up with a brilliant invention because he or she is smarter than everyone else.
And that’s because ideas are fundamentally networks of other ideas.
We take the tools and metaphors and concepts and scientific understanding of our time, and we remix them into something new.
But if you don’t have the right building blocks, you can’t make the breakthrough, however brilliant you might be.
The smartest mind in the world couldn’t invent a refrigerator in the middle of the 17th Century. It simply wasn’t part of the adjacent possible at that moment.
But by 1850, the pieces had come together.
The first thing that had to happen seems almost comical to us today. We had to discover that air was actually made of something, that it wasn’t just empty space between objects.
In the 1600s, amateur scientists discovered a bizarre phenomenon - the vacuum, air that seemed actually to be composed of nothing and that behaved differently from normal air.
Flames would be extinguished in a vacuum. A vacuum seal was so strong that two teams of horses could not pull it apart.
In 1659, the Anglo-Irish scientist Robert Boyle had placed a bird in a jar and sucked out the air with a vacuum pump. The bird died, as Boyle suspected it might, but curiously enough, it also froze.
If a vacuum was so different from normal air that it could extinguish life, that meant there must be some invisible substance that normal air was made of.
And it suggested that changing the volume or pressure of gases could change their temperature.
Our knowledge expanded in the 18th Century, as the steam engine forced engineers to figure out exactly how heat and energy are converted, inventing a whole science of thermodynamics.
Tools for measuring heat and weight with increased precision were developed, along with standardised scales such as Celsius and Fahrenheit. And as is so often the case in the history of science and innovation, when you have a leap forward in the accuracy of measuring something, new possibilities emerge.
All of these building blocks were circulating through Gorrie’s mind, and he started to build a refrigeration machine.
It would use energy from a pump to compress air. The compression heated the air. The machine then cooled down the compressed air by running it through pipes cooled with water.
When the air expanded, it pulled heat from its environment, and just like the tetrahedral bonds of hydrogen dissolving into liquid water, that heat extraction cooled the surrounding air.
It could even be used to create ice.
Amazingly, Gorrie’s machine worked. No longer dependent on ice shipped from a thousand miles away, Gorrie reduced his patients’ fevers with home-grown cold.
Despite his success as an inventor, Gorrie went nowhere as a businessman. But the idea of artificial cold didn’t die.
Refrigeration was suddenly everywhere, not because people had stolen Gorrie’s idea, but because they’d independently hit upon the same basic architecture.
One of these inventors was the French engineer Ferdinand Carre, who designed a refrigeration machine that followed the same basic principles as Gorrie’s.
After the American Civil War broke out in 1861, the Union blockaded the southern states and in so doing, stopped the flow of ice. The sweltering southern states suddenly found themselves in desperate need of artificial cold.
Soon ice-making machines, based on Carre’s design were being smuggled through the blockade.
These new devices used ammonia as a refrigerant and could churn out 400lbs (181kg) of ice per hour. Carre’s machines were smuggled all the way from France to Georgia, Louisiana, and Texas.
By 1870, the southern states made more artificial ice than anywhere else in the world.
Almost everything in the 19th Century story of cold was about making it bigger, more ambitious.
But the next revolution in artificial cold would proceed in the exact opposite direction. Cold was about to get small.
In the winter of 1916, an eccentric naturalist and entrepreneur moved his young family up to the remote tundra of Labrador.
He had spent several winters there on his own, starting a fur company breeding foxes and occasionally shipping animals and reports back to the US Biological Survey.
The food left a great deal to be desired.
The bleak climate in Labrador meant that everything you ate during the winter was either preserved or frozen, and would be mushy and tasteless when thawed out.
Other than fish there were no fresh sources of food.
The naturalist took up ice fishing with some of the local Inuits, carving holes in frozen lakes and casting a line for trout.
With air temperatures so far below zero, a fish pulled out of the lake would freeze solid in a matter of seconds.
Unwittingly, the young naturalist had stumbled across a powerful scientific experiment as he sat down to eat with his family in Labrador.
When they thawed out the frozen trout from the ice-fishing expeditions, they discovered it tasted far fresher than the usual grub.
The difference was so striking that he became obsessed with trying to figure out why.
And so Clarence Birdseye began an investigation that would ultimately put his name on packages of frozen peas and fish fingers in supermarkets around the world.
He began experimenting and eventually, he hit upon a coherent explanation for the dramatic difference in taste. It was all about the speed of the freezing process.
A slow freeze allowed the hydrogen bonds of ice to form larger crystalline shapes. But a freeze that happened in seconds - ‘flash freezing' as we now call it - generated much smaller crystals that did less damage to the food itself.
The Inuit fishermen hadn’t thought about it in terms of crystals and molecules, but they had been savouring the benefits of flash freezing for centuries by pulling live fish out of the water into shockingly cold air.
An idea began to form in the naturalist’s mind. With artificial refrigeration becoming increasingly commonplace, the market for frozen food could be immense, assuming you could solve the quality problem.
In the first decades of the 20th Century, the frozen-food business was considered to be the very bottom of the barrel. (Frozen food was so appalling that it was banned at New York State prisons for being below the culinary standards of convicts.)
One key problem was that the food was being frozen at relatively high temperatures, often just a few degrees below freezing.
Yet scientific advances had made it possible to artificially produce temperatures that were positively Labradorian. By the early 1920s, Birdseye had developed a flash-freezing process using stacked cartons of fish frozen at -40C (-40F).
He found that just about anything he froze with this method - fruit, meat, vegetables - would be remarkably fresh after thawing.
Frozen food was still more than a decade away from becoming a staple of the American diet. (It required a critical mass of freezers - in supermarkets and home kitchens - that wouldn’t fully come into being until the post-war years.)
But Birdseye’s experiments were so promising that in 1929, just months before the Black Friday crash, his company General Seafood was acquired by the Postum Cereal Company.
His adventures in ice fishing had made him a multimillionaire.
In our age of locally sourced, artisanal food production, the frozen ‘TV dinners’ have fallen out of favour. But in its original incarnation, frozen food had a positive impact on health, introducing more nutrition into the diets of Americans.
Flash-frozen food extended the reach of the food network in both time and space.
Produce harvested in summer could be consumed months later. Fish caught in the North Atlantic could be eaten in Denver or Dallas. It was better to eat frozen peas in January than it was to wait five months for fresh ones.
Turning on the air
By the 1950s, Americans had adopted a lifestyle that was profoundly shaped by artificial cold, buying frozen dinners purchased in the refrigerated aisles of the local supermarket, and stacking them up in the deep freeze of their new Frigidaires, featuring the latest in ice-making technology.
In that iconic 1950s American household, the most novel cold-producing device was not storing fish filets for dinner or making ice for the martinis.
It was cooling down (and dehumidifying) the entire house.
The first ‘apparatus for treating air’ had been dreamed up by a young engineer named Willis Carrier in 1902.
He had been hired by a printing company in Brooklyn, New York, to devise a scheme that would help them keep the ink from smearing in the humid summer months.
His invention not only removed the humidity from the printing room - it also chilled the air.
Carrier noticed that everyone suddenly wanted to have lunch next to the printing presses, and he began to design contraptions that would be deliberately built to regulate the humidity and temperature in an interior space.
The first great test for air-conditioning came over Memorial Day weekend of 1925, when Carrier debuted an experimental AC system in Paramount Pictures’ new flagship Manhattan movie theatre, the Rivoli.
He even persuaded Adolph Zukor, the legendary chief of Paramount, that there was money to be made by investing in central air for his theatres. Zukor himself showed up for the Memorial Day weekend test.
Carrier and his team had some technical difficulties getting the AC up and running. The room was filled with hand fans waving furiously before the picture started. Carrier later recalled:
“It takes time to pull down the temperature in a quickly filled theatre on a hot day but gradually, almost imperceptibly, the fans dropped into laps as the effects of the air conditioning system became evident. We then went into the lobby and waited for Mr Zukor. When he saw us, he said tersely, ‘Yes, the people are going to like it.’”
Between 1925 and 1950, most Americans experienced air-conditioning only in large commercial spaces such as movie theatres, department stores, hotels or office buildings.
Carrier knew that AC was headed for the domestic sphere, but the machines were simply too large and expensive for a middle-class home.
By the late 1940s air-conditioning finally made its way to the home front, with the first in‑window portable units appearing on the market.
Within half a decade, Americans were installing more than a million units a year. Places that had been intolerably hot and humid were suddenly tolerable.
By 1964, the historic flow of people from South to North that had characterised the post Civil War era had been reversed.
The Sun Belt expanded with new immigrants from colder states, who could put up with the tropical humidity or blazing desert climates thanks to domestic air-conditioning.
Tucson rocketed from 45,000 people to 210,000 in just 10 years. Houston expanded from 600,000 to 940,000 in the same decade. Carrier’s invention circulated more than just molecules of oxygen and water. It ended up circulating people as well.
But the rise of the Sun Belt in the United States was just a dress rehearsal for what is now happening on a planetary scale.
All around the world, the fastest growing megacities are predominantly in tropical climates: Chennai, Bangkok, Manila, Jakarta, Karachi, Lagos, Dubai, Rio de Janeiro.
Demographers predict that these hot cities will have more than a billion new residents by 2025.
The artificial truth
The dreamers and inventors who ushered in the cold revolution didn’t have eureka moments, and their brilliant ideas rarely transformed the world immediately.
But the frozen world that Tudor and Birdseye helped conjure into being would do more than just populate the world with fish fingers.
It would also populate the globe with people, thanks to the flash freezing of human semen, eggs and embryos. Millions of human beings owe their existence to the technologies of artificial cold.
When we think about breakthrough ideas, we tend to be constrained by the scale of the original invention.
We figure out a way to make artificial cold, and we assume that will just mean that our rooms will be cooler, or there will be a reliable supply of ice cubes for our sodas.
That much is easy to understand. But if you tell the story of cold only in that way, you miss the epic scope of it.
Over the past two centuries its impact has been staggering.
From the transformed landscape of the Great Plains, to the new lives and lifestyles brought into being via frozen embryos, all the way to vast cities blooming in the desert.