ELI5: how is it possible to lose technology over time like the way Roman’s made concrete when their empire was so vast and had written word?
ELI5: how is it possible to lose technology over time like the way Roman’s made concrete when their empire was so vast and had written word?
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cost effectiveness. people will always find cheaper ways to achieve similar results.
There are some technologies like Greek Fire or Damascus Steel which were lost because they intentionally did not write down how to make them, and instead just had a group of people who knew and they would teach others. The reason being they didn’t want anyone else to know. Yes it means those recipes get lost as these did, but it also means your enemies can’t steal it and use it against you.
the papers it was written on got lost or destroyed
Guilds make it harder, because they guard their secrets from non members. Apprenticeship also means there’s no need to write it down as it is taught directly. So when the practice falls out of use, it doesn’t get passed on because it’s no longer useful or practical (builders in the north wouldn’t have had ready access to volcanic ash for example).
“Institutional knowledge” is a tricky beast. It made it harder to recreate the Saturn V rockets for a more modern example, because while there were plans and designs, the minor tweaks and things to perfect it were lost because those little things weren’t standardized, they were hand fittings as the machining wasn’t precise enough yet. So when they moved on to smaller and more common designs for satellites and more compact nuclear weapons, and didn’t need a heavy lifter rockets, the specialized knowledge was lost and had to be re-developed. And rather than trying to retool an older design it was easier to go back to the drawing board with more modern materials and manufacturing techniques.
We’ve actually rediscovered how to create Roman concrete. The reason we lost the knowledge of it is because the recipe they wrote simply said to use water, not specifying that the water needed was ocean water. The salt changes the chemical composition.
The reason knowledge in general is lost is because it isn’t written down or passed on, or key knowledge that would be obvious to the original knowledge keepers isn’t recorded, and once the obvious knowledge is forgotten and the knowledge no longer makes sense, it isn’t passed on anymore.
We’ve lost technology that was invented in the last century simply because the technical skills needed to keep it going wasn’t passed on. We don’t know how to build the Saturn Five rocket because the people with the skills needed to build it don’t exist anymore, even though we have the full schematics for it. We don’t know how to make glass springs for scientific instruments anymore because the glassmakers who made it never got apprentices who could or would learn how.
While I can’t talk about the exact example of Roman concrete, losing technology is rather simple.
Remember that the concrete mentioned is a highly specific Version of concrete. It’s more like losing the blueprints to an iPhone 9 but still beeing able to make phones.
Remember that the fall of the Roman empire took many years. Construction projects during an economic and societal collapse are usually few. You’re not building a new colliseum.
Imagine you’re one of the few specialists that knows how to make a specific good. What if that item isn’t needed for 10 years and you find another way to earn your food? Then noone will carry the Tradition?
As to why write it down? Teaching was mostly an oral passing of knowledge. Why would you write down something that was generally common knowledge.
You probably work, so just consider how rare it is for people to document how and what they do in their job, unless it’s for a very specific reason.
And then those factors all compound.
I’m not sure the Romans knew their concrete was so good. They built with what they had, which included the right ingredients. It took a long time to notice that some walls aged much better than others.
When civilization degrades then people spend more time doing basic survival tasks and a lot of people die. If someone with expertise survives, society doesn’t have the resources for major projects so the knowledge doesn’t get passed on. Maybe it was written down somewhere, but the library and major cities were looted and burned. So the text was lost.
In summary, written documents destroyed, experts die, those who survive forget and no one in the next generation learns.
Additionally, the collapse of trade may make critical components unavailable.
The loss of most knowledge is never more than a generation away. If no one learns to read starting today then almost all complex knowledge will be gone in 20-50 years.
We have lost way newer technology than Roman concrete that we had to rediscover again. Like when US government had to reinvent FOGBANK in 2000 as they started refurbishing old nuclear warheads, because they forgot how to make it and those were designed less than 30 years ago by that time.
Any sufficiently advanced civilization has supply chains with many steps with people working on individual parts without necessarily knowing how to make the individual pieces.
When those are disrupted by war, plague or just people stop making something it doesn’t take long for people to forget how to make it.
The documentation is also usually imperfect or made for people who are already familiar with the process. So there are details not mentioned as others are assumed to know it like how Roman’s didn’t bother to note that their concrete used Sea Water. Why would they? Anyone making concrete at that time would obviously know that.
Knowledge is kept in a few hands. We see this today in many places. People keep knowledge private as “job security”. “They can’t fire me because I’m the only one who knows how to do this.”
Sometimes in ancient times its about not understanding the underlying cause. So as ships went out further/longer, scurvy became a thing. They eventually figured out limes stopped the scurvy. GREAT! Well, limes would eventually take up a lot of room, so they started to juice the limes and just bring lime juice instead of limes to help. Scurvy came back.Turns out its less the juice that helps against scurvy and its the pulp. So there was a period of discovery of a solution. enhancing the solution, but going away from the actual solution because they didnt have the actual understanding of the chemistry
I believe there was a town in Egypt long ago that we no longer know where it was. “Write down where it is? Why? Everyone knows where it is!”
Think of it like a recipe. Someone 1000 years from now finds a brownie recipe. It says 2 eggs. While we all know that means a chicken egg, someone from a chicken-less future would have no idea. And yeah, maybe you could make a brownie with robins eggs or turtle eggs. But it wouldn’t be the same as how we make it today.
It would be really weird to see a cake recipe that says “2 eggs from a chicken”.
Same concept. The Romans had sea water easily accessible and readily available. They wouldn’t think to specify.
If you didn’t have the internet, and needed a new battery for your flashlight, but all of the people who knew how to make flashlights were dead, would you be able to make one?
Batteries have existed for more than a hundred years, but one solar flare, and a scientist witch-hunt could send us back to the dark ages very fast.
Usually because there are details that are misunderstood that turn out to be really important.
If your recipe for a particular kind of glass indicate using a certain kind of powdered stone, it might only apply to stone from a specific quarry, the only quarry the inventor of that glass used and who didn’t understand why that stone might differ from the same kind of stone from a different quarry.
And sometimes context matters. During Covid western scientists spend 9 months insisting that Covid wasn’t airborne (in opposition to scientists in Asia) because they used a criteria for airborne biological agents from a paper written in the 1950s by US scientists. But the context for that paper was the criteria for airborne for biological weapons, where you want the biological agent hang over a city like Moscow for an extended period of time. But we weren’t worried about Covid acting like a biological weapon, we just wanted to know if it could linger in the air inside a classroom or elevator for multiple minutes such it could be contracted by someone who didn’t even see the infected person, and sure enough, it can hang in the air for that long. US scientists in other fields like kept pointing this out, but we had this definition we’d been using for 70 years…
A lot of the time we don’t pay close enough attention to WHY we do this thing in this way. Often we don’t document that. Sometimes we don’t even know it’s a choice – why would you do it any other way, but a generation later people find a better way and change it, and then it doesn’t work any longer. Part of the strength of roman concrete comes from not overprocessing the lime, which was easy for the romans doing this by hand but hard for people in the 21st century doing this by machine. We just figured that out like last year. In some cases they used volcanic ash (because they had a lot of that around) which had some critical minerals not in western substitutes. We figured that out only like a decade ago.
Because knowledge isn’t inherent or inherited. It has to be taught and or written down so that others can learn it.
The Romans pretty much lost all their knowledge in one generation.
The dark ages is named after this period.
Imagine current society hitting an apocalyptic event.
No one has time teach anything but survival. No one is going to school.
One generation all the knowledge we have could be lost and the majority of skills we would need to survive we would have to reinvent.
There is a BBC series called “connections” where the first episode talks about these very issues.
Knowledge is precious.
It’s estimated only around 10-20% of the Roman empire were literate. So it’s possible the workers that made the concrete couldn’t even read and just passed the recipe down verbally, once the empire fell there was nobody employing a bunch of concrete makers to build temples etc so the recipe was forgotten.
Its also important to note that somewhere around 99% of all written works have not been preserved to the modern era, so it may have been written down at various points, just not on something that would survive for over 1000 years. Or if it was it got lost and is waiting to be rediscovered in some ancient refuse pile.
Newer and better technology supplanted the “lost technology” or the lost tech was no longer relevant.
How many mechanics do you know who can work on a carburetor?
Can your IT department fix a dot matrix printer?
For that matter…. how many kids do you know who can write in cursive?
There are sometimes when technology becomes so common place no one thinks it’s worth recording, and it’s such common knowledge. For example we use salt and pepper as seasonings, but in 1000 years time someone will look at salt and pepper in a table and have to guess what those powders are.
Then you have technology that is kept by an inner circle, who didn’t want it to spread, for example weapons technology like Greek fire, would be a strictly controlled recipe, but then if an enemy invaded the city and killed everyone there, the ones who knew the recipe would take their secret recipe with them to the grave, even if it was written down, that scrap.if parchment may be in a foreign language, and some Persian looked at the scribbles of Greek and figured it was trash.
Then you have information that’s protected like a corporations trade secret. Let’s say you invent a new way to make waterproof paper, you sell it to everyone but no one knows how you make it, and then you retire and it’s impossible to find.
Then you have accidental discoveries, like a blacksmith working a firge can make really strong swords because the iron mined from the quarry near his village has a certain composition, and the Smith down the road gets his iron from somewhere else, and they both use iron to make swords but that other smith’s swords don’t break even though they’re using the same techniques and technology. No one eve figures out the iron is different, and then the mine dries up and they’re iron from somewhere else and suddenly that Smith has “goegotten” how to make invulnerable swords.
Mostly the “lost technologies” thing is a myth. We may not know their methods but the often cited examples like wootz steel being legendarily superior isn’t supported. We have examples form the time discussed, as well as continuously produced examples showing it was never lost nor was it ever a particularly amazing product to begin with. For its time, maybe, but as with Roman Concrete these aren’t examples of futuristic metamaterials exceeding what we can do today.
The methods being lost may be real, and there may be real setbacks in terms of comparable local alternatives. Exaggerating these examples is too common though.
It’s not only possible, it’s likely, especially as more and more stuff goes onto digital media.
In recent history, NASA already lost specs for heat tiles and DOE lost some nuclear weapon designs for a while there.
Don’t forget humans’ favorite pastime of war and destruction. As new management takes over, intelligentsia is the first to go and then the books.
Part of it was that they assumed everyone knew what to use.
So, imagine you go forward a few hundred years give someone a recipe that calls for eggs, and milk. You might get a question about “which type of eggs?” Because you’re assuming they know you mean chicken eggs. But maybe you mean ostrich eggs? Or something else? That’ll throw it off and possibly ruin it. Same thing for some things, like “use this ingredient” that now no longer exists because it’s extinct, all used up, or just… vague to the point that we don’t know and don’t know the exact ratio.
The next part is also stuff that was intentionally never written down and widespread. A good example is Greek fire. They didn’t want people using it against them so not many copies of the recipe were made.
And part of it you can see in modern times, we know the exact methods… but the skill to make something no longer exists because it requires precise timing, and expertise to do it. And infrastructure that no longer exists as well.
It’s kind of wild, right? You’d think something as important as Roman concrete wouldn’t just disappear. But losing technology over time actually happens more easily than you’d expect.
Back then, a lot of knowledge wasn’t written down in full detail—it was passed down through hands-on experience. Think of it like your grandma’s amazing recipe that no one measured exactly, they just knew how to do it. When the Roman Empire collapsed, so did the systems that kept that knowledge alive—like skilled workers, libraries, and trade routes. And with no internet or backups, once a scroll was lost or a city was destroyed, that info was gone for good.
Add to that the fact that later civilizations didn’t use Roman concrete much, and over time, people just kind of… forgot how it worked. So even with a vast empire and the written word, it’s totally possible to lose technology if it stops being passed on or used.
Or how the Hindus lost the recipe for Soma (their religious hallucinogenic drink)
I work in IT. No one documents shit, orgs are just smaller civilizations, they lose knowledge all the time.
Ever forget to write something down because it’s so simple you’d never forget? Sometimes that happens and times change and people do forget.
Another cause of lost history are wars. If everyone that knows is killed or dispersed they may not have the ability or desire to pass on everything they know, especially if they are no longer dealing with it on a daily basis in their new life. Libraries and such get destroyed, further limiting future generations from carrying on specific knowledge.
A lot of good responses but there is another thing to consider: cost cutting. Many technologies get lost because the culture can no longer sustain making them in that way, either because they no longer have access to the same raw materials or because they can no longer afford to and over time they lose the knowledge of how to do so.
When a civilization collapses, and everyone is left to fend for themselves… and invaders arrive and start taking things for themselves… and burning whatever they don’t want…
Who is going to protect the libraries that store all this information? The record keeping? The scientist journals?
Probably nobody, everyone’s looking out for themselves. There’s no government, the economy is probably trashed, people are just worried about eating and shelter.
I’ve thought about this before… how many people in the world know how to make a computer chip? How many people know how to make the machine that makes a computer chip? How many people know how to operate that machine?
How many people would have to die in a mass death event to reduce that number to zero… or at least small enough that it would be very hard to find them. Would they have time to teach someone these things before they die?
Then boom, computer chip is lost.
Fill in the blank with any modern materials or tech that we use today… especially with how specialized some of it is.
Definitely possible, consider the original CRT TVs. We know the theory, it’s well described but try making a basic black and white TV now. Almost nothing of the pre-digital TV industry exists anymore. Tons of proprietary manufacturing processes, material formulations, circuit designs, and that’s just on the receiving end. Think of everything on the broadcast side, cameras, microphones, encoders, etc.
Do you know how you go to work in a large corporation and nothing is properly documented? So when few key people leave they take all the knowledge base with them? And yet we live in a world where it’s never been as easy to document everything? Thee you go
The Soviets made a submarine using titanium primarily that was non ferromagnetic. The manufacturability is now lost to man
Doesn’t answer the question I realize, but certainly a more recent example
So, Roman concrete specifically was made with a certain type of ash from a specific volcano near Rome. This material was useful because the Roman Empire at it’s height did a lot of monumental building.
Now, remember that while they did have writing, to preserve that writing someone had to specifically hand write out everything on rather expensive manuscripts. Those had to be kept safe and dry, and probably had to be recopied regularly. So it was an effort to maintain those records and quite expensive. Some writing was done on architecture and similar, but not a huge amount and it wasn’t preserved a whole lot, since most writing that was preserved was by aristocrats for aristocrats, not by tradesmen for tradesmen.
So we wouldn’t necessarily expect this sort of information to be particularly likely to be written down and preserved anyway in some manuscript in a monastary or something. But why didn’t people just keep using it? After all, it’s not like people forgot a variety of other skills.
Since it required a certain volcanic ash from a certain volcano, and was mainly useful for large buildings, when the fall of the Empire happened there wasn’t an active communities of builders to keep the knowledge alive. There wasn’t a bunch of money for monumental construction, and even if, say, some builder in Gaul or even a distant part of Italy might have wanted a concrete castle, even if the knowledge had been maintained through the crisis times when no one was building, the sort of trade routes needed to haul large volumes of material long distances economically no longer existed.
Without a reason to build or materials to build with, and without everyday tradesmen having high levels of literacy and maintaining written records of their own, the knowledge just wasn’t maintained.
Modern civil engineers are intimately familiar with how to make Roman concrete. The Romans made concrete structures that are standing to this day, but we make concrete structures that are taller and more complex. Why? We reinforce our concrete with steel, such as rebar. The salt content in Roman concrete wouldn’t mesh with that—the steel would rust and wither after a few strong rainfalls. So our modern society decided height and strength of concrete structures is more of a priority than sheer resilience.
How Romans made concrete was not a secret at the time and was written down at the time. When the empire collapsed so much of their writings were lost over time due to just decaying away that the “less” educated middle ages did not have the specific formula and instructions and their lesser technological abilities at the time didn’t really allow them to research it as such. And people are under the impression we scientists have been baffled by Roman concrete till the present day and this is not true. But pop science articles being what they are, click bait, you will see this stated a lot. We know what is in Roman concrete and could make it if we wanted. But we have many different types of concrete today that are designed for specific qualities depending on what you are using it for. And structures we are building, such as concrete piles in bridges do not need to last 2000 years because the bridge is not designed to operate that long. It is designed to last a set period, maybe 50-100 years or whatever, then it needs to be replaced due to things like metal fatigue etc.
You know how when you go to an automotive sub and ask a question and the top answer is “read your owner’s manual” and it doesn’t answer the question? Like that. “Make concrete in the usual way, if you don’t know how then you shouldn’t be making concrete”
People have always been smug assholes.