Why Weren't Hot Air Balloons Invented Sooner?
TL;DR
Hot air balloons certainly could have arrived at least decades earlier and there's a high chance they could have arrived centuries, possibly even millennia earlier.
Jason Crawford asks, "Why did it take so long to invent X?" The post is an invitation. It asks the reader to identify low-hanging fruit, inventions that could have been invented far earlier but weren't. Now, most technologies don't fit the bill. Not everything could have been invented long before it was. Many relied on recent advancements. The airplane only became possible once engines became powerful enough to lift them into the sky. But for other inventions, such as the cotton gin or flying shuttle, neither scientific nor technological barriers seem present. To this list of mysteriously absent inventions, I'd like to propose an addition: The hot air balloon.
Ancient Balloons?
The notion of the ancient or medieval world having hot air balloons makes for exciting counterfactual history. Floating Roman military lookouts, ornate balloons arriving with Zheng He’s fleet in South Asia, balloon cartographers in the age of exploration… It’s all very eye-catching, but is it realistic?
In actual history, there were no Roman, Umayyadan, or Imperial Chinese hot air balloons. In fact, highly dubious claims of ancient South American balloons aside, no one in the classical or medieval world is known to have constructed a manned balloon. The first verified flight occurred in 1783, amid the industrial revolution. This early balloon was created by the Montgolfier brothers, French industrialists in the paper industry.
Why Manned Balloons Could Have Been Invented Sooner
Previous Inventions/Historical Precedent
Mini Hot Air Balloons
The sky lantern was invented by the Chinese by at least the 3rd century AD. Constructed from paper and a small fuel source, sky lanterns operated using the same principles as manned hot air balloons, well over a thousand years prior to the invention of the latter.
Human Flight Before Balloons
Beyond this, the concept of human flight was by no means novel to Dynastic China. Man-lifting kites were likely developed shortly before the time of the Sui Dynasty (581–618). Such kites became widespread enough throughout East Asia for the Japanese government to have prohibited them at a time.
The First Hot Air Balloon Didn’t Take Long To Invent
While Joseph-Michel Montgolfier, having created parachutes in the past, possessed preexisting knowledge of aeronautics, the brothers did not begin experimenting with balloons until the winter of 1782. By the end of the year, the duo had successfully built two prototypes, the second of which had so much lifting force they lost control of it. The prototype would proceed to float for nearly two kilometers (1.2 miles) before landing. Upon touchdown, it was ripped apart by frightened passersby. By October 1783, the first manned flight occurred, and a month later on November 21, 1783, the first untethered manned balloon flight was performed.
The Montgolfiers' Balloon Was Inefficient
The Montgolfier brothers didn’t quite understand the physics involved– they believed thick smoke was the key to keeping the bag aloft, so they burned things like straw, wool, and even old shoes to produce the densest possible smoke. Not recognizing that the heat had made the bag rise, the brothers also seem to have believed at the time that they had produced a new, previously undiscovered gas that was lighter than air.
Interestingly enough, the Montgolfier brothers created a functional hot air balloon without understanding the underlying physics. They believed that it was the smoke rather than hot air that caused the balloon to rise. Because of this, they burned materials that would produce thick smoke such as wool, straw, and even old shoes. Hardly optimal. A functional hot air balloon could be constructed without relying on the most efficient fuel sources available to late 18th-century engineers or a rigorous understanding of the science behind its operation.
Additionally, the first manned Montgolfier balloon was covered in an ornate gilded finish and lavish drapery, adding unnecessary weight to the craft. Yet, in spite of this, the balloon had no problem ascending the full height its tether would permit (around 80ft). Within a few months, an untethered flight would reach an altitude of some 3,000ft! This suggests their balloon could have been even less optimized and still successfully flown.
Fast Dissemination
The Montgolfier balloon experiments were no Apollo Program. The barrier to entry for building a hot air balloon was low. After its invention, news quickly spread of this new and exciting technology. Balloonomania gripped the public. Throughout Europe, hot air balloons were being built left and right. Within twenty years, a hot air balloon was built in Japan out of washi (a kind of Japanese paper). The quick dissemination and seemingly wide variety of materials used indicate the materials needed to build a hot air balloon were already plentiful and common throughout the world by the late 18th century.
Arguments Against The Hot Air Balloon Being Invented Earlier
It was Invented During The Industrial Revolution
This evidence is purely circumstantial, but it is admittedly suspicious. The industrial revolution and the century before it did comprise a revolution in thought. It heralded the birth of a new profession, the mechanical philosopher. Empowered by the idea of progress and the promises of improvement, these individuals eagerly began to tinker and experiment. Maybe the answer is as simple as the fact that few people before the Montgolfiers seriously worked on developing a manned balloon, despite it being possible.
However, at the same time, the industrial revolution marks an era in which scientific knowledge and industrial technology began advancing steadily. Perhaps we've overlooked a key detail. A seemingly trivial technological advancement that turned out critical to the hot air balloon's invention. Maybe unseen technological barriers previously prevented a practical hot air balloon from being developed. Textile production certainly did progress substantially in the 18th century. The quality and price of cloth available to the Montgolfier brothers were likely better than what would have been available to inventors centuries prior. This leads to a second counterpoint.
The Flying Shuttle
By the time of the Montgolfier balloon, the flying shuttle had fully disseminated into the wider French economy, having been introduced to the country decades prior by John Kay. This invention not only significantly increased the output of weavers and lowered textile prices, but also allowed for larger pieces of continuous cloth to be woven. A balloon constructed during an earlier time would have to likely contend with higher textile prices as well as more stitching of smaller pieces. If this stitching proves too “leaky”, then additional patching cloth will add additional weight. However, the flying shuttle widely permeated British industry by the 1750s, meaning that despite our medieval balloon fantasies being dashed, the invention was still twenty years late.
Textile Quality
The Montgolfier balloon was constructed out of a skin made of the very lightweight textile taffeta (a form of silk) while paper was applied to the inside, providing the envelope with greater rigidity. The history of taffeta dates back to the middle ages in the Islamic world. It’s hard to find information on whether another textile available earlier could have served as a suitable alternative. In case there wasn’t, then the hot air balloon did arrive centuries later than it could have, but not a thousand years or more.
Ultimately, both of these arguments are plausible but must contend with the countering evidence. Montgolfier's balloon was inefficient, cheap, slapped together in a matter of months, and relied on faulty scientific premises. That said, I do not have the necessary knowledge of textile history to give a definitive answer.
So if the hot air balloon could have been invented sooner, what does this mean? Two questions come to mind:
How different would premodern societies look with hot air balloons?
Why does it matter that the hot air balloon was invented late?
To answer the first question, slightly different but not radically. The invention of the hot air balloon was not nearly as important as Newcomen's steam engine or Gutenberg's printing press. It did not revolutionize any industry in particular and mostly remained a curious novelty. (A niche it continues to occupy today.) That said, hot air balloons did have some practical applications:
Military Ballooning—Hot air balloons can be used for reconnaissance
Cartography—By providing an aerial view, balloons are useful for more accurate mapmaking
Weather Observation—Balloons can be used to gain knowledge about parts of the atmosphere inaccessible from the ground
Developed during an earlier age, other possible uses come to mind:
Prestige—The invention of the hot air balloon had tremendous psychological repercussions across the world. In an earlier time with slower technological diffusion, the first state to develop the hot air balloon could use it to boost prestige for decades or longer.
Signaling—This is more hypothetical but rooted in history. The Chinese used sky lanterns for battlefield signaling. But a string of hot air balloons could be used like a Byzantine beacon system. Large and high in the sky, tethered balloons could make for a creative optical telegraph.
As for the second question, that's harder to answer. One could be dismissive and write off the nonexistence of the medieval balloon as a curious but trivial observation. However, careful observation through the Progress Studies lens uncovers hidden specks of practical knowledge for our own times. To understand technological progress, we must not only understand why, when, and how innovation happens, but also why sometimes it doesn't happen. Our modern economy is much more efficient and complex than its medieval counterpart. It isn't likely many inventions with low capital intensiveness like the hot air balloon have been ready for decades, but simply not created yet. (If anyone has any counterexamples in the past 30 years I'd love to hear them!) But could there be other gaps? Could there be structural barriers preventing inventions feasible decades ago from appearing? Probably. It's easy to find contenders. If a partially reusable and affordable rocket like the Falcon 9 was feasible in the 90s, then the answer is surely yes.
It's interesting that the hot air balloon was invented in France rather than Britain, the industrial epicenter at the time
Anton Howes concluded the flying shuttle itself could have been invented centuries prior to its actual appearance
SF writer Gene Wolfe wrote an alternate history short story, "Straw", where the hot air balloon was invented shortly after the fall of Rome. It's in THE BEST OF GENE WOLFE, and it's also in STOREYS FROM THE OLD HOTEL, where he writes;
"Every so often I like to think of things that could have been invented a long time before they actually were - or that might easily have been invented but weren't. For example, for hundreds of years, wars among the Greeks (possibly the most briliantly creative people in history) were fought by heavy infantrymen armed with long spears and circular shields. Most of them were won by the Spartans, the ackowledged masters of holplite warfare. Then, around 379 BC, Thebes produced a general of real genius named Epaminondas. And Epaminondas came up with the simplest great military innovation I know of: he cut a notch out of each round shield. That was all it was. Instead of looking like a whole cracker, the shield looked like a cracker from which a tiny bite had been taken. But that bite permitteed the soldier to use his left hand to assist his right in managing his long spear, and the Thebans crushed the Spartans at Leuctra.
"The point is that Epaminondas' notch could have been cut a thousand years sooner -- in Homer's day, for example. In the same way, it seems obvious that the hot-air balloon could have been invented well before the end of the ancient world. You need a little rope (it's been around for a long time), a lot of silk (which by then was coming steadily along the spice routes), some straw, and an iron basket to burn it in. There are no moving parts, and the design is simplicity itself -- a bag held over a fire. But if the hot-air balloon had been invented in 500 AD, what would have been done with it?"
I enjoyed this investigation a lot; it's fascinating to think of the uses to which this could have been put.
You may be interested in a related (ongoing) project I've been working on, to survey ‘paths untaken’--cases of historical technological delay, restraint, or post-development abandonment, and to try and assess their rationales or contributing factors. So far, it includes about 160 candidate cases. Many of these need much further analysis and investigation, but you can find the preliminary longlist of cases at https://airtable.com/shrVHVYqGnmAyEGsz/tbl7LczhShIesRi0j , and an initial writeup and pitch of the project at: https://forum.effectivealtruism.org/posts/pJuS5iGbazDDzXwJN/the-history-epistemology-and-strategy-of-technological -- I'd be interested to hear any thoughts or comments.