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Podcast Transcript
One of the biggest problems that humanity has faced for thousands of years is heat.
Excessive heat made it difficult to work in the middle of the day. Heat was especially problematic in the tropics, where a shockingly large percentage of humanity lived.
As cities became more developed, excess heat, all year round, became a limiting factor in how tall buildings could get.
All of these problems were solved with one invention.
Learn more about air conditioning and how it helped usher in the modern world on this episode of Everything Everywhere Daily.
Heating and cooling are flip sides of the same coin, yet they are very different in how you go about doing it.
Heating is relatively simple. Take something and burn it, and you will produce heat. If that isn’t possible, then we produce heat and we can keep ourselves warm by just trapping that heat through insulation.
Cooling, however, is totally different. Cooling, or getting rid of energy, is much more difficult.
Traditionally, the options you had for keeping cool wer more limited.
People would often just shield themselves from the direct rays of the sun. They might wear long, loose clothing to keep the warmer air temperature away from their body, or they might wear wide-brim hats to keep the sun off of them.
Their buildings might made of thick walls to keep the inside cool and keep the outside heat out.
Many cultures also worked around it by avoiding the hottest times of the day. In Spain and other cultures, things shut down in the middle of the day to avoid the heat. People would leave the fields and their businesses to go home, have an extended lunch, and wait for the sun to get lower in the sky.
Most of these things involved simply avoiding the heat and keeping the sun off of you. It’s not a bad strategy, but it’s also not quite the same thing as burning wood to produce heat.
However, there is a physical process that can remove heat from a system and cool it down: evaporation.
You have probably experienced this yourself. If you get wet, the water drying on your skin will cool you down. This is why you can cool off by swimming in water, even if the water is warm.
For thousands of years, people around the world have used evaporation to cool themselves down.
In ancient Egypt, people would hang wet reeds in windows. The evaporation of water from the reeds cooled the air as it passed through the window.
In Persia, they used a system that was different but relied on the same fundamental principles. They created tall towers with openings known as wind catchers that faced the prevailing winds and captured and directed airflow into buildings. The air would then pass over a pool of water or wet surfaces, cooling down as it entered living spaces.
This technique is actually being revived in modern buildings that use passive cooling as a way to lower temperatures without any electricity.
During the Islamic golden age, many buildings featured central courtyards with fountains or pools. These water features cooled the surrounding air through evaporation, and the courtyards provided shaded, cool spaces.
Before I get any further into the discussion of air conditioning, I should explain why evaporation reduces temperatures because this ancient technique is critical to understanding how modern air conditioners work.
As you know, matter can be in different states, particularly solid, liquid, or gas. Heating or cooling something can cause it to undergo a phase change, causing it to melt, freeze, or boil.
However, it is possible for something to be a gas at the same temperature as a liquid or a solid. That is because when you measure the temperature of something, you are actually measuring an average of the kinetic velocity of the molecules that make up the system. Not all of the molecules in a glass of water, for example, have the same amount of energy.
When a water molecule evaporates, it absorbs heat energy from its surroundings. This energy is used to break the molecular bonds that hold water molecules together in the liquid state, allowing them to escape into the air as vapor.
Because energy is taken out of the air, the air gets cooler.
This principle of using the evaporation of substances to cool something down was used in the 18th and 19th centuries to conduct experiments such as liquifying gases. To reach very cold temperatures, they would often use a cascade of cooling one gas to cool another gas, and so on.
This physical phenomenon was used to create the first refrigeration systems. The very first mechanical refrigeration system was built in 1834 by an American inventor living in Britain named Jacob Perkins.
His refrigeration system and all subsequent systems use a liquid called a refrigerant, which has a low boiling point. Early refrigerants used liquids such as ammonia, sulfur dioxide, methyl chloride, or propane. When these liquids, in a closed loop, underwent a phase transition, they took heat our of the system, just like via evaporation.
This was not the first air conditioner because air conditioning isn’t just refrigeration. It also has to do with the conditioning part of air conditioning, which has to do with humidity, not temperature.
Hot weather is one thing, but hot weather with high humidity is particularly annoying.
The development of the first air conditioner is usually credited to Willis Carrier.
Carrier was working for the Buffalo Forge Company in 1902 when one of their clients had a problem. The Sackett-Wilhelms Lithographing and Publishing Company in Brooklyn, New York, had a problem. When they were doing four-color printing, they had to run paper through their presses four times and the paper had to be perfectly aligned.
The problem was that humidity caused the paper to change its width, which would ruin the printing process.
Carrier developed a system where air would be blown over coils with cooled water. Moisture in the air would condense on the cooled coils, resulting in cooled air with moisture removed.
The system worked, and many people commented that it felt more comfortable around the machine. Carrier put two and two together and created the Carrier Company, one of the largest air conditioning companies in the world today.
The term air conditioning was coined in 1906 by Stuart Cramer, who ran a textile mill in North Carolina. He was trying to add humidity to the air in his factory to make the textiles easier to handle.
Carrier liked the name and adopted it for his company.
Air conditioning did not catch on right away. The early systems were expensive and bulky, and they required electricity, which was stilln’t ubiquitous in the early 20th century.
The first home to be air-conditioned was built in Minneapolis in 1914, 12 years after the invention of air conditioning. The system was massive, requiring a separate room in the house for the equipment. It isn’t even known if the system was ever used, as the owner of the home died a year before it was complete.
In 1922, Carrier developed the Centrifugal Refrigeration Compressor. It allowed for air conditioning systems that were smaller and cheaper with fewer moving parts.
The first place to adopt this new system was the Rivoli Theater in New York City in May of 1922.
Movie theaters proved to be eager early adopters of air conditioning. They could easily adapt the ductwork of their healing systems for air conditioning, and air conditioning systems could lure in customers. During hot summers, many people would buy a ticket to a movie, not because they were interested in the film, but because they wanted to spend an hour or two away from hot and humid weather.
The first air conditioner that would fit into a window was invented in 1931. This system is very similar to the window units that many people around the world use today.
These first windowed air conditioning systems were extremely expensive. A single unit cost between $10,000 and $50,000 in 1932 dollars. If that were to be converted into modern dollars, the price would somewhere between
As of the 1930s, residential air conditioning was still just for the wealthy.
In 1933, the first air conditioning system for automobiles was released, and in 1935, Chrysler was the first major auto producer to offer it in its vehicles. However, it was extremely expensive.
Home air conditioners didn’t become commonplace until after the Second World War. In 1945, Life Magazine ran a four-page spread on air conditioning titled “Air Conditioning/ After the War it Will be Cheap Enough to Put in Private Homes.”
Their prediction would turn out to be true.
In 1947, 43,000 cheap window air conditioning units were sold, which exploded over the next decade.
By the early 1960s, central air conditioning systems were being installed in homes that cooled the entire building and didn’t require bulky units sticking out of windows.
As air conditioning became affordable and commonplace in all public spaces, it began to change major societal and cultural patterns.
Communities in deserts or very hot climates usually don’t have large populations. Suddenly, it became possible for someone to live in such an area and not have to suffer living in the heat. Communities such as Phoenix, Arizona, and Las Vegas, Nevada, exploded in population after the rise of air conditioning.
Air conditioning also helped in the development of skyscrapers. In a recent episode, I covered the history of skyscrapers and the technical innovations that made them possible. One of the important developments that I didn’t mention in that episode was air conditioning.
Very tall buildings can’t allow windows to be open on higher floors for a host of reasons. That means that all of the heat created on lower floors would be trapped in the building as it rose. That is not to mention the problem of an entire wall of windows being heated by the sun.
Without air conditioning, such buildings would be very uncomfortable or uninhabitable.
It might also be the case that air conditioning has made entire countries viable. In 2010, the founder of modern Singapore, Lee Kwan Yew, was asked during an interview, “Anything else besides multicultural tolerance that enabled Singapore’s success?”
His answer was straightforward and surprising. He said:
Air conditioning. Air conditioning was a most important invention for us, perhaps one of the signal inventions of history. It changed the nature of civilization by making development possible in the tropics.
Without air conditioning you can work only in the cool early-morning hours or at dusk. The first thing I did upon becoming prime minister was to install air conditioners in buildings where the civil service worked. This was key to public efficiency.
Air conditioning has become so important worldwide that it is one of the biggest consumers of electricity.
For example, India uses 91 TWh each year just for air conditioning, and the United States uses over 600 TWh.
During the Second Iraq War, the largest number of American casualties were from improvised explosive devices on the sides of roads that detonated near trucks carrying fuel. What was all that fuel going towards? The biggest use was for air conditioning.
The importance of air conditioning might best be seen in what happens when it disappears. During heat waves that cause power outages, thousands of deaths can result from a lack of air conditioning.
Over the last 20 years, 3,142 people in the United States have died from heat-related causes. The majority of them have died in their homes when the air conditioning went out. In 2003, a heat wave in France killed an estimated 15,000 people, the vast majority of which were over the age of 75.
Air conditioning has become a vital part of the modern world. It allows people to live and work in comfort and it has allowed the habitation of cities and countries that would otherwise be unlivable.
Even though many people don’t think about it, air conditioning has become of the pillars of the modern world.
