Who hasn't sung the praises of air conditioning on a sweltering summer day? But who do you have to thank for this refreshing convenience?
The short answer to that question is Willis Carrier, an American engineer credited with inventing the first modern air conditioner. However, the idea of using evaporated water — or other liquids — to cool off a muggy space far precedes Carrier's 1902 invention.
The first known systems that used water to cool indoor spaces were created by the ancient Egyptians, who lowered the temperature in their homes by hanging wet mats over their doorways. The evaporated water from the wet mats reduced indoor air temperatures and added refreshing moisture to the dry desert air.
Not long after the Egyptians beat the heat with their doorway mats, the Romans developed a primitive air conditioning system by utilizing their famous aqueducts to circulate fresh water through indoor pipes, a method that significantly reduced the air temperature inside stuffy villas.
Of course, it wasn't until long after the Romans had their time in the sun that the principles of modern air conditioning were developed. In 1758, American statesman and inventor Benjamin Franklin, along with John Hadley, a professor at Cambridge University, began experimenting with the refrigerating effects of certain liquids.
In previous studies, Franklin had determined that the refrigerating effects of a liquid are related to how quickly it evaporates. He and Hadley expanded on this finding by using ether and a bellows to cool down a mercury thermometer to 25 degrees below freezing. This experiment prompted Franklin to remark in his journal about the possibility of freezing to death, even on a warm summer's day.
This observation by Franklin was a foreshadowing of things to come. In 1820, British inventor Michael Faraday was also experimenting with the refrigeration properties of gases when he discovered that, by compressing and liquidizing ammonia and then allowing it to evaporate, he could cool the air inside his laboratory.
Modern air conditioning is born
Several decades after Faraday made his discovery with ammonia, a Florida physician named John Gorrie developed a machine to keep yellow fever patients cool. Gorrie's machine used compressed air and water to create an open cooling system. Patented in 1851, Gorrie's "cold air machine" was the first patented invention that facilitated mechanical refrigeration, as well as the first to resemble a modern air conditioner.
But it wasn't until 1902 that the history of air conditioning really began to heat up. In that year, a young engineer named Willis Carrier was tasked with the chore of creating a system for treating the air at the Sackett-Wilhelms Lithographing and Publishing Company in Brooklyn, N.Y. Printing company executives found that excessive humidity at its printing plant wreaked havoc on the color register used for fine, multi-color printing.
By 1903, Carrier had designed a system of chilled coils that maintained a constant, and comfortable, humidity of 55 percent inside the Sackett-Wilhelms printing plant — the equivalent of using 108,000 pounds of ice daily to cool the plant. The modern air conditioner was born. [See also: Science of Summer: How Does Air Conditioning Work?]
Not long after Carrier invented his game-changing air conditioning machine, a mill engineer named Stuart Cramer created a similar ventilating device to add water vapor to the stifling air inside of textile plants. While Cramer was the second person to develop such a device, he was the first to coin the term "air conditioning" to describe the purpose of his invention.
Air conditioning continued to be used in plants and mills throughout the early 1900s, but it wasn't until 1914 that this modern convenience was installed for the first time in a private home. In that year, a Minneapolis millionaire named Charles Gates hired Carrier to install an air conditioner in his mansion.
Carrier went on to invent a more efficient air conditioning unit — the centrifugal refrigeration machine, or "chiller." His invention debuted on Memorial Day weekend in 1925 at the grand opening of the Rivoli Theater in Times Square, treating many movie theater patrons to their first taste of indoor "cool comfort," as advertised by the theater managers. It was wildly successful. During the next five years, Carrier installed his cooling units in 300 movie theaters across America.
For years to come — before air conditioning was a regular fixture in homes across America — people flocked to the cool and comfortable movie theaters in the heat of summer, essentially starting the "summer blockbuster" trend.
Throughout the next decade, scores of commercial businesses jumped on the air conditioning bandwagon, installing huge (by modern standards) and toxic (they used ammonia as a coolant) air conditioning devices in their stores. The addition of air conditioning allowed employee productivity to soar in the summer months, a time when workers frequently began losing their motivation due to sweltering temperatures. The expansion of air conditioning into American homes was stalled during the Great Depression and World War II, but by the 1950s, those who could afford it began adopting this modern convenience by the thousands.
And while only 10 percent of American homes had air conditioning units in 1965, this number continued to climb slowly and steadily as the decades rolled by. By the year 2007, 86 percent of homes had AC systems, according to the Carrier Corporation. Today, air conditioning units are considered standard equipment in U.S. homes. The type of AC equipment varies across regions, however. Central air systems are most common in the South, Midwest and West, while room conditioners are most common in the Northeast, according to the U.S. Energy Information Administration (EIA).
Widespread use of air conditioning eventually facilitated a long-term shift in the U.S. population. Prior to home AC units, cities in the desert, the Deep South and Florida had very little growth as most people couldn't handle the oppressive weather. With the advent of home air conditioning, however, people were able to spread out and migrate to these formerly avoided areas. Today, some of the hottest cities in America — such as Phoenix, Arizona; Las Vegas, Nevada; and Dallas, Texas — continue to see population growth, thanks to air conditioning.
Additional reporting by Traci Pederson, Live Science Contributor.
Live Science newsletter
Stay up to date on the latest science news by signing up for our Essentials newsletter.
Elizabeth is a former Live Science associate editor and current director of audience development at the Chamber of Commerce. She graduated with a bachelor of arts degree from George Washington University. Elizabeth has traveled throughout the Americas, studying political systems and indigenous cultures and teaching English to students of all ages.