Lost technology is an enduring theme because for much of human history it was very easy to "lose". The main narrative of the last 2000 years is one of a fallen great civilization. Only in the past 100 years or so do we have large continuously maintained corpus of knowledge instantly replicated across the entire world, translated to almost every spoken language.
We do lose technology and engineering practices and human mental techniques. It is not all that rare.
Roman concrete, greek fire, Indian musical sound pillars, Inca Masonry, Stradivarius Violins, Damascus Steel (the ancient technique), Polynesian Wayfinding - there are dozens of such lost arts.
> Is it because we have lost the secrets of ancient Roman technology?
> Not really. We know how to make durable concrete; it’s just more expensive than the alternatives that last 30-40 years.
... For a span of almost 2000 years this was not the case, there was nobody you could pay to make a concrete dome like the Pantheon's, not at any price. And we only properly reverse-engineered the Roman recipe in the past decade.
I think a technology still counts as "lost" even if it gets rediscovered in the distant future!
I think there's a lot of recency bias here. Over and over again in human history, we've lost technology. We often lose technology. The past 200 years is the exception, not the rule.
I also think that some parts are really weakly-reasoned:
> The Ancient Egyptians cut stone with an impressive level of precision. The Incas in South America did too. So much so that people sometimes claim that the Egyptians and the Incas used some kind of now-lost technology. But they most likely didn’t: they were just really good at cutting stone.
Yeah, but we're not that good at cutting stone anymore. So what gives? The explanation here is very lacking. They either had a technology that let them cut stone so well, or some special know-how (itself a form of technology, in my opinion) that enabled cutting stone so precisely.
I agree there are much better examples. I think Historically more significant loses have happened. There is trove of techniques Gauss solved 100 years in advance that were not communicated and lost. Example here being FFTs which were not rediscovered until post ww2.
I think the question is also really hard to answer in a non-answerable way because if you don't know you've forgotten who do something you simply just don't know. If you sub-divide humanity in to factions certain factions have lost the economic ability of doing some things for example have been lost to America. While humanity can still do it certain places would be totally lost without the existing tribal knowledge. It would take us a long time to reinvigorate a tool and die industry in America its not a lost thing but if you can't do it commercial currently can you do it at all?
Hopefully that's nota weird direction to take the discussion in
I agree, the article is very dismissive about losing technology. There's lots of ways we lose technology, from big cultural changes over time (Dark Ages) as well as more niche technologies or processes, like a "secret formula" that was protected until it was lost. The difference with technology is that often we can rediscover lost technologies by the web of understanding we have around it and other advancements in our recovery techniques.
The Egyptian alien engineer thing is mostly a meme, but it stems from the fact that Western Egyptologists can't get their heads out of their asses long enough to agree on how it was done. Plus the Egyptian government won't allow any kind of physical or non-physical investigations because it would conflict with Zahi Hawass's personal pet theories.
No technology was really lost, we just can't agree on how they stacked the stones into pyramids. The stonecutting technology they used is very well understood and we even have real actual tools used by the actual ancient Egyptian stonecutters and some of the tools used to manipulate and place stones.
There's also several incredibly solid theories on pyramid construction, but to verify them would require investigating the actual pyramids, which Hawass will not allow.
If you really think that some sort of unknown ancient supertechnology was used for creating the Egyptian's artifacts and giant structures, I'd strongly suggest you watch these two videos. They do an excellent job of completely demythifying all of those poorly substantiated speculative ideas.
> Yeah, but we're not that good at cutting stone anymore
We are pretty good at cutting stone, but not very good at cutting stone with the resources available to the ancient egyptians. So in some sense the technology has been lost: but that's more because there aren't really people try to perfect that craft, as opposed to because of some magical trick or technique that we don't know anything about (Though it's murky exactly what approaches they used, that's because there's multiple plausible ones and it's hard to pin them down, not because there's no plausible ones we can think of).
> So: loss of technology is not impossible. But to an innovative and large culture like modern human civilization, it’s not really something that happens. It’s just a fun trope for stories. Let’s hope it remains that way.
I agree with “let’s hope it remains that way.” But you may be underestimating the fragility of modern human civilization and all the systems that are so effective at preserving knowledge. At the scale of history, most of our technology has only existed for the blink of an eye. It would not take much, really, for all this to go away.
Absent the internet, power grid, and other systems of global infrastructure, absent anyone to take care of the libraries (which are falling out of favor), absent an authority to gather together all the experts with their tightly focused specializations, absent the chip fabs and the global supply network, how exactly do you build a computer? Or even something as “simple” as a pencil?
Overall, this is a good thing - I certainly don't want to go back to superstition, subsistence farming, and dying of infectious diseases at 50.
But it's a good principle to be aware of: economic incentives often make it impossible to intentionally lose a technology once it's developed.
I would love to go back to a time in which I could safely walk my small town's streets without 3-ton steel boxes noisily charging through at speeds far faster than a horse could gallop. But we've developed the technology to build 300 horsepower mobile living rooms that the average person can buy (for a staggering quantity of debt) and we've decided to allow them everywhere. In addition to the greenhouse emissions and costs and noise pollution, they're the leading cause of death for people from ages 5 to 22, and the second most common cause from ages 23 to 67. But the staggering utility means we're not putting those back in Pandora's box.
Air conditioning, likewise, is incredibly comfortable and a massive boon for health and productivity in the hotter regions of the world - not to mention the incredible nutrition benefits of freezing or refrigerating food - but in a vicious cycle, you have to use energy that makes the world hotter to make your tiny part of the world cooler. Personally, I'll go without until June, leave the thermostat high during the summer, and turn it off come September. But a shop can generate traffic and an employer can generate productivity by spending a little more on energy costs. The genie offered us the vapor compression refrigeration cycle, and that will never be put back in the bottle by a selfish society.
>Overall, this is a good thing - I certainly don't want to go back to superstition, subsistence farming, and dying of infectious diseases at 50.
A nitpick but people weren't dying at 50; they were dying as infants. The average life expectancy was around 50 because so many children died, but the life expectancy of people who made it past age 5 was around 60-70: https://pmc.ncbi.nlm.nih.gov/articles/PMC2625386/ .
I appreciate all the examples and the case the author is making! Don't buy the conclusion, as I think he or she is missing the subtle complexity of technology. If you had to rebuild modern civilization after a calamity, or just a gradual loss, I think it would take a very long time. I think, for example, if China experiences a disaster in the next few decades, our ability to manufacture physical goods at the quality and price they do will be set back decades or longer.
We have already experienced local loss of the details of technology. I think this is what the article is missing. He's looking at big things that are easy to state, while missing the tools-that-build-tools-that-build-tools foundation. I think the also "That's not tech, that's high skill" distinction is a technicality.
It is also viewing history through a filtered lens. A bit like labeling an age as a "stone" or "bronze" age, because that's the durable material that survived. Or anything involving the fossil record.
> ... forgotten inventions ... lost technology ... the knowledge of making
I see people in this thread talking past each other and I think the reason why is because the author is conflating 3 very different topics (inventions, technology and knowledge).
E.g. we absolutely have forgotten the knowledge in how Egyptians built the pyramids.
That doesn't mean per se that Egyptians had better/worse technology - but from a knowledge of how they built the pyramids - that absolutely is lost.
This is a more interesting example- the theory isn't that we lost the tech, but that the new tech was too good, too pure.
The incidentals of the old, 'dirty' way of manufacturing it (that we just spent billions and billions to destroy and clean up) apparently (speculation, since classified) added some unknown impurities that affected its performance.
And either it needed to be redesigned with the new manufacturing process, or go back to the old process to fit the specs of existing weapons or the weapons would need to be redesigned.
We didn't lose the tech, but other 'advances' in both tech and society (not having workers manually handle dangerous stuff) caused an overall regression, not advancement.
It's the EPA DC chlorine case all over again, of 'progress and safety' actually increasing danger and causing overall regression.
> It might have been difficult to procure pozzolana ash when the trade routes were less safe in the early Middle Ages, which would make durable concrete rarer.
I think this could be how modern technology will be lost in the future. We have been seeing a reversal of globalization. We have seen countries guard their raw materials more tightly than before. Trade routes could disappear for geopolitical reasons. The United States was happy using Russian RD-180 rocket engines and Russian uranium after the Cold War; and look at how quickly this trade has become undesirable. Now consider materials and technologies lesser known than uranium or rocket engines, or simply less critical to a country's military might. A country might not even know it has a single sourced component until trade has stopped.
In the modern era, there's a new way of losing technology: A niche product with a shared supply-chain dependency on some components that are used in a high-volume market which disappears in favour of a new technology.
For example, if you make something like a magnetic field sensor, your customers are a handful of university labs, and your supplier of some niche ferromagnetic material stops their production line because they sold primarily to the spinning-rust hard drive industry and that market no longer pays the bills, your product becomes impossible to make. Your use case will never supply the quantities needed to run the crucibles.
For a few decades it's perhaps theoretically possible to reproduce if, somehow the survival of the world depended on it and the old material production line can be restarted, but after that, people with the knowledge have all passed away and any documentation is scattered and incomplete.
This is one specific type of sensor. There are a lot of different types of ultra-sensitive magnetic field sensors, and while specific manufacturing knowledge might die, documents describing how the devices work will persist.
Imagine we nuke the world right now ... How long until we can start creating a modern iPhone again. Right now only 2-3 countries are able at all to produce these chips. And all rely on very sensitive technology.
Knowledge might not be lost but rebuilding tech might take centuries depending on how worse it is. And that is probably very similar to the past. Middle age people probably understood how Romans build their water supply but where unable to reproduce it because how the bad the time was.
The Egyptian pyramids are an elephant in the room. Conventional thinking is they're burial chambers built with copper tools and ramps.
But other historians believe they reflect a lost technological sophistication. The pyramids are incredibly precise: perfectly aligned to true north (within ~0.05°), made with millions of 2-70 ton blocks and precise internal engineering for passageways and chambers. Someone recently advocated that there's substantial subterranean infrastructure under the pyramids. The technology to move 70 ton blocks didn't exist again until the 1800's.
One of modern science's ideological straitjackets is Oliver Heaviside's restatement of Maxwell's 20 equations with 20 unknowns into four vector calculus equations. Heaviside's restatements made the math accessible to regular engineers who wanted to build things. But the restatements are arguably a simplification that neutered electromagnetism: https://x.com/TaxiCabJesus/status/1964345590604845487 (Grok had a nice answer for "what phenomenon are inadequately explained by Heaviside's four equations?").
The stones are fastened together without mortar.
They are set on top of each other using their
weight to keep them together. The craftsmanship
detail is so fine and the stones are connected
with such precision that no light passes through
the joints.
Modern humans are at least 100,000 years old. Most of our earlier civilizations are probably along the coasts of the continents, and were submerged at the end of the last ice age. It's silly to think that technology has not been lost and rediscovered over and over again.
> Someone recently advocated that there's substantial subterranean infrastructure under the pyramids.
Ah yes, those giant subterran pillars beneath the pyramids. That actually interested me, so I decisively delved deeply into it, to do my due dilligence. Only to discover an early case of advanced AI-sloppery with no proven source at all. Completely made up.
For about lost technologies, exist very interest niche, remembered to me by mentioning of Roman concrete.
Example, ancient natural asphalt, which literally surfaced at Red sea.
So, probably natural material, not always exactly known how appear, but fortunately existed and used by ancient people.
I only cannot agree that all lost technologies are not that we might truly care about. As example, Roman concrete could be really valuable in modern world, as current concrete just is being destroyed with time, and this is very serious problem, because could be dangerous for constructions like large dams and bridges; also, need some solution for long term burial of radioactive trash.
How to save such info, very interest question and not easy. Possible example could be some sort of long term independent shelter, under Moon surface, where could store digital archives with information.
The first was Airadar. (Not "AI", "Air".)[1] I wrote about this on HN in 2016. This was a small phased-array radar for light aircraft, developed in 1973. It was suppressed by a patent secrecy order, because it was better than what the USAF had at the time. The inventor was a really good RF designer. Phased array radars existed back then, but they were huge ground-based installations. Mini phased array radars are available now, but it took decades for them to be available for light aircraft.[2]
The second was the electronic fluorescent lamp ballast. This was a replacement for those bulky magnetic ballasts found inside fluorescent light fixtures. The inventor licensed it to MagneTek, the biggest maker for magnetic ballasts, which didn't make it and didn't pay any royalties. So the inventor went to Townsend, Townsend, and Crew, the IP law firm in Palo Alto, and, after much litigation, came out with a hundred million or so. The law firm put this in their reception room brag book. Today, electronic fluorescent lamp ballasts are a commodity.
The problem with FOGBANK, the aerogel used in fusion weapons, turned out to be that the original process only worked because of some impurity in the raw materials. Attempts to replicate the process used a source for a raw material which was now better purified, and the process failed. It required tens of millions of dollars and a special appropriation to figure out the underlying problem. There was a period of over a decade during which the US could not make new H-bombs.
I've heard rumors that the recipe for Cobblestones has been lost. Here in Indiana, they used to be cast at a factory in Attica[2], I have a pile of them from an old walkway we've replaced. The embossed lettering is proof they aren't carved or cut, but rather cast with a debossed negative mold.
I was surprised to learn that most cobblestone was actually quarried rectangular blocks[1], used as ships ballast, discarded after cross-Atlantic voyages.
Apparently we not only lose technology we also lose history. So things that were lost and reinvented usually in a different way: The wheel, Dome building (got reinvented twice 1k years in between), printed letters (3k years), self healing concrete (not sure if has been reinvented since the romans), astronomy calculators (1.5k years? not sure is there was an antikythera mechanism in the rennaisance), steam operated opening doors (2k years, we went directly to electric).
These are of the top of my head mostly covered by HN posts. Especially the antikuthera mechanism the loss was that entire that even the memory of this mechanical calculator or even the existence of other such calculator was lost. Also lost apparently was the process of creating an H bomb that"s for good but probably it has been secretly reinvented by now.
This is a clear case of a discussion appearing as it has a tech content and in fact its historical. Statistically and given tge infinite creativity of people infinite things will have disappeared, through a process of randomness, usefulness and politics a few prevail. The wheel was forgotten because it was useless. It required working economies, trade and usable roads, even dirt roads. As for printing letters if that prevailed when it was invented 2-3k years back we could have reached the stars by now.
In the times its even easier to lose technologies, they are not intuitive anymore, they are stored in miniture formats easily forgotten and stored easily corrupted and fail media, guarded behind laws, encryptions and interests. Medical technology is our lifetime's major culprit.
He's using the subset of familiar technology as evidence that we've not lost it. But there are two massive super-sets that have been lost : (1) recorded & observed artifacts with unknown origins and (2) destroyed libraries and manuscripts
Even in the past 20 years the Iraqi Archives & Mosul Library were destroyed -- not to mention dozens-to-hundreds destroyed since WW1 , as well as many destroyed in ancient conflicts.
"do you think we had anything important in there?" -- "not possible, we've got everything we need already"
In other words, we don't know what we don't know because it's been destroyed and so have our records of it.
We are constantly losing technology as the treadmill of technological progress continues. Casette tapes, CRT displays, and perhaps photographic film are some examples. One can argue that there are "strictly better" technologies available now, but there are always niche cases where the new and obsolete technology are not quite fungible. What if for some reason a modern industry gets wiped out? Then we'd have to revisit the lost art.
As an immediate example, my wife's business needs p-channel small signal JFETs. These apparently are no longer fabricated, and with the way the semiconductor industry moves, they are likely never coming back in any appreciable quantity. So once the world's supply of obsoleted semiconductors dries up, the technology will basically be lost.
A lot of stuff is casually forgotten. It may live on in a private collection or a dusty filing cabinet somewhere but not accessibly.
People used to design scientific calculators out of a relatively modest number of discrete transistors and diodes. Telephone central offices used to run on a hardwired relay computer called the "marker". How many people still walk this earth who can design stuff like that? More immediately, with your phone casually using integrated circuits with transistor counts in the billions to watch a Youtube video... people used to watch off-the-air colour TV where the TV in question was made out of less than two dozen vacuum tubes, equivalent to 1-2 transistors each. That stuff is still easily found but in another few decades will also be essentially forgotten.
Oh, and what would it take to manufacture, say, Cibachrome paper and Kodachrome film? I know the Polaroid instant film technology has been laboriously resurrected but lots of obsolete chemical processes are essentially lost.
35 comments
[ 3.7 ms ] story [ 73.3 ms ] threadRoman concrete, greek fire, Indian musical sound pillars, Inca Masonry, Stradivarius Violins, Damascus Steel (the ancient technique), Polynesian Wayfinding - there are dozens of such lost arts.
> Not really. We know how to make durable concrete; it’s just more expensive than the alternatives that last 30-40 years.
... For a span of almost 2000 years this was not the case, there was nobody you could pay to make a concrete dome like the Pantheon's, not at any price. And we only properly reverse-engineered the Roman recipe in the past decade.
I think a technology still counts as "lost" even if it gets rediscovered in the distant future!
I also think that some parts are really weakly-reasoned:
> The Ancient Egyptians cut stone with an impressive level of precision. The Incas in South America did too. So much so that people sometimes claim that the Egyptians and the Incas used some kind of now-lost technology. But they most likely didn’t: they were just really good at cutting stone.
Yeah, but we're not that good at cutting stone anymore. So what gives? The explanation here is very lacking. They either had a technology that let them cut stone so well, or some special know-how (itself a form of technology, in my opinion) that enabled cutting stone so precisely.
I think the question is also really hard to answer in a non-answerable way because if you don't know you've forgotten who do something you simply just don't know. If you sub-divide humanity in to factions certain factions have lost the economic ability of doing some things for example have been lost to America. While humanity can still do it certain places would be totally lost without the existing tribal knowledge. It would take us a long time to reinvigorate a tool and die industry in America its not a lost thing but if you can't do it commercial currently can you do it at all?
Hopefully that's nota weird direction to take the discussion in
For example, Roman concrete, that strengthens in sea water: https://news.mit.edu/2023/roman-concrete-durability-lime-cas...
No technology was really lost, we just can't agree on how they stacked the stones into pyramids. The stonecutting technology they used is very well understood and we even have real actual tools used by the actual ancient Egyptian stonecutters and some of the tools used to manipulate and place stones.
There's also several incredibly solid theories on pyramid construction, but to verify them would require investigating the actual pyramids, which Hawass will not allow.
https://www.youtube.com/watch?v=mysYT260dqU&list=PLuROoe7EZ3...
https://www.youtube.com/watch?v=n_NguZUDku4&t=9216s
We are pretty good at cutting stone, but not very good at cutting stone with the resources available to the ancient egyptians. So in some sense the technology has been lost: but that's more because there aren't really people try to perfect that craft, as opposed to because of some magical trick or technique that we don't know anything about (Though it's murky exactly what approaches they used, that's because there's multiple plausible ones and it's hard to pin them down, not because there's no plausible ones we can think of).
I agree with “let’s hope it remains that way.” But you may be underestimating the fragility of modern human civilization and all the systems that are so effective at preserving knowledge. At the scale of history, most of our technology has only existed for the blink of an eye. It would not take much, really, for all this to go away.
Absent the internet, power grid, and other systems of global infrastructure, absent anyone to take care of the libraries (which are falling out of favor), absent an authority to gather together all the experts with their tightly focused specializations, absent the chip fabs and the global supply network, how exactly do you build a computer? Or even something as “simple” as a pencil?
But it's a good principle to be aware of: economic incentives often make it impossible to intentionally lose a technology once it's developed.
I would love to go back to a time in which I could safely walk my small town's streets without 3-ton steel boxes noisily charging through at speeds far faster than a horse could gallop. But we've developed the technology to build 300 horsepower mobile living rooms that the average person can buy (for a staggering quantity of debt) and we've decided to allow them everywhere. In addition to the greenhouse emissions and costs and noise pollution, they're the leading cause of death for people from ages 5 to 22, and the second most common cause from ages 23 to 67. But the staggering utility means we're not putting those back in Pandora's box.
Air conditioning, likewise, is incredibly comfortable and a massive boon for health and productivity in the hotter regions of the world - not to mention the incredible nutrition benefits of freezing or refrigerating food - but in a vicious cycle, you have to use energy that makes the world hotter to make your tiny part of the world cooler. Personally, I'll go without until June, leave the thermostat high during the summer, and turn it off come September. But a shop can generate traffic and an employer can generate productivity by spending a little more on energy costs. The genie offered us the vapor compression refrigeration cycle, and that will never be put back in the bottle by a selfish society.
A nitpick but people weren't dying at 50; they were dying as infants. The average life expectancy was around 50 because so many children died, but the life expectancy of people who made it past age 5 was around 60-70: https://pmc.ncbi.nlm.nih.gov/articles/PMC2625386/ .
We have already experienced local loss of the details of technology. I think this is what the article is missing. He's looking at big things that are easy to state, while missing the tools-that-build-tools-that-build-tools foundation. I think the also "That's not tech, that's high skill" distinction is a technicality.
It is also viewing history through a filtered lens. A bit like labeling an age as a "stone" or "bronze" age, because that's the durable material that survived. Or anything involving the fossil record.
I see people in this thread talking past each other and I think the reason why is because the author is conflating 3 very different topics (inventions, technology and knowledge).
E.g. we absolutely have forgotten the knowledge in how Egyptians built the pyramids.
That doesn't mean per se that Egyptians had better/worse technology - but from a knowledge of how they built the pyramids - that absolutely is lost.
This is a more interesting example- the theory isn't that we lost the tech, but that the new tech was too good, too pure.
The incidentals of the old, 'dirty' way of manufacturing it (that we just spent billions and billions to destroy and clean up) apparently (speculation, since classified) added some unknown impurities that affected its performance.
And either it needed to be redesigned with the new manufacturing process, or go back to the old process to fit the specs of existing weapons or the weapons would need to be redesigned.
We didn't lose the tech, but other 'advances' in both tech and society (not having workers manually handle dangerous stuff) caused an overall regression, not advancement.
It's the EPA DC chlorine case all over again, of 'progress and safety' actually increasing danger and causing overall regression.
I think this could be how modern technology will be lost in the future. We have been seeing a reversal of globalization. We have seen countries guard their raw materials more tightly than before. Trade routes could disappear for geopolitical reasons. The United States was happy using Russian RD-180 rocket engines and Russian uranium after the Cold War; and look at how quickly this trade has become undesirable. Now consider materials and technologies lesser known than uranium or rocket engines, or simply less critical to a country's military might. A country might not even know it has a single sourced component until trade has stopped.
For example, if you make something like a magnetic field sensor, your customers are a handful of university labs, and your supplier of some niche ferromagnetic material stops their production line because they sold primarily to the spinning-rust hard drive industry and that market no longer pays the bills, your product becomes impossible to make. Your use case will never supply the quantities needed to run the crucibles.
For a few decades it's perhaps theoretically possible to reproduce if, somehow the survival of the world depended on it and the old material production line can be restarted, but after that, people with the knowledge have all passed away and any documentation is scattered and incomplete.
Example: https://pmc.ncbi.nlm.nih.gov/articles/PMC7146409/
Knowledge might not be lost but rebuilding tech might take centuries depending on how worse it is. And that is probably very similar to the past. Middle age people probably understood how Romans build their water supply but where unable to reproduce it because how the bad the time was.
But other historians believe they reflect a lost technological sophistication. The pyramids are incredibly precise: perfectly aligned to true north (within ~0.05°), made with millions of 2-70 ton blocks and precise internal engineering for passageways and chambers. Someone recently advocated that there's substantial subterranean infrastructure under the pyramids. The technology to move 70 ton blocks didn't exist again until the 1800's.
One of modern science's ideological straitjackets is Oliver Heaviside's restatement of Maxwell's 20 equations with 20 unknowns into four vector calculus equations. Heaviside's restatements made the math accessible to regular engineers who wanted to build things. But the restatements are arguably a simplification that neutered electromagnetism: https://x.com/TaxiCabJesus/status/1964345590604845487 (Grok had a nice answer for "what phenomenon are inadequately explained by Heaviside's four equations?").
The Coral Castle in Florida was a labor of love, built by a single man: https://en.wikipedia.org/wiki/Coral_Castle
Modern humans are at least 100,000 years old. Most of our earlier civilizations are probably along the coasts of the continents, and were submerged at the end of the last ice age. It's silly to think that technology has not been lost and rediscovered over and over again.Ah yes, those giant subterran pillars beneath the pyramids. That actually interested me, so I decisively delved deeply into it, to do my due dilligence. Only to discover an early case of advanced AI-sloppery with no proven source at all. Completely made up.
And everybody copy pasting the shit! GRRR! :(
Example, ancient natural asphalt, which literally surfaced at Red sea.
So, probably natural material, not always exactly known how appear, but fortunately existed and used by ancient people.
I only cannot agree that all lost technologies are not that we might truly care about. As example, Roman concrete could be really valuable in modern world, as current concrete just is being destroyed with time, and this is very serious problem, because could be dangerous for constructions like large dams and bridges; also, need some solution for long term burial of radioactive trash.
How to save such info, very interest question and not easy. Possible example could be some sort of long term independent shelter, under Moon surface, where could store digital archives with information.
The first was Airadar. (Not "AI", "Air".)[1] I wrote about this on HN in 2016. This was a small phased-array radar for light aircraft, developed in 1973. It was suppressed by a patent secrecy order, because it was better than what the USAF had at the time. The inventor was a really good RF designer. Phased array radars existed back then, but they were huge ground-based installations. Mini phased array radars are available now, but it took decades for them to be available for light aircraft.[2]
The second was the electronic fluorescent lamp ballast. This was a replacement for those bulky magnetic ballasts found inside fluorescent light fixtures. The inventor licensed it to MagneTek, the biggest maker for magnetic ballasts, which didn't make it and didn't pay any royalties. So the inventor went to Townsend, Townsend, and Crew, the IP law firm in Palo Alto, and, after much litigation, came out with a hundred million or so. The law firm put this in their reception room brag book. Today, electronic fluorescent lamp ballasts are a commodity.
The problem with FOGBANK, the aerogel used in fusion weapons, turned out to be that the original process only worked because of some impurity in the raw materials. Attempts to replicate the process used a source for a raw material which was now better purified, and the process failed. It required tens of millions of dollars and a special appropriation to figure out the underlying problem. There was a period of over a decade during which the US could not make new H-bombs.
[1] https://books.google.com/books?id=NWzlTqj0gQ4C&pg=PA64#v=one...
[2] https://www.garmin.com/en-US/p/576890/
[3] https://news.ycombinator.com/item?id=11862911
I was surprised to learn that most cobblestone was actually quarried rectangular blocks[1], used as ships ballast, discarded after cross-Atlantic voyages.
[1] https://en.wikipedia.org/wiki/Sett_(paving)
[2] https://indianaalbum.pastperfectonline.com/photo/5FA11838-DE...
These are of the top of my head mostly covered by HN posts. Especially the antikuthera mechanism the loss was that entire that even the memory of this mechanical calculator or even the existence of other such calculator was lost. Also lost apparently was the process of creating an H bomb that"s for good but probably it has been secretly reinvented by now.
This is a clear case of a discussion appearing as it has a tech content and in fact its historical. Statistically and given tge infinite creativity of people infinite things will have disappeared, through a process of randomness, usefulness and politics a few prevail. The wheel was forgotten because it was useless. It required working economies, trade and usable roads, even dirt roads. As for printing letters if that prevailed when it was invented 2-3k years back we could have reached the stars by now.
In the times its even easier to lose technologies, they are not intuitive anymore, they are stored in miniture formats easily forgotten and stored easily corrupted and fail media, guarded behind laws, encryptions and interests. Medical technology is our lifetime's major culprit.
Even in the past 20 years the Iraqi Archives & Mosul Library were destroyed -- not to mention dozens-to-hundreds destroyed since WW1 , as well as many destroyed in ancient conflicts.
"do you think we had anything important in there?" -- "not possible, we've got everything we need already"
In other words, we don't know what we don't know because it's been destroyed and so have our records of it.
As an immediate example, my wife's business needs p-channel small signal JFETs. These apparently are no longer fabricated, and with the way the semiconductor industry moves, they are likely never coming back in any appreciable quantity. So once the world's supply of obsoleted semiconductors dries up, the technology will basically be lost.
People used to design scientific calculators out of a relatively modest number of discrete transistors and diodes. Telephone central offices used to run on a hardwired relay computer called the "marker". How many people still walk this earth who can design stuff like that? More immediately, with your phone casually using integrated circuits with transistor counts in the billions to watch a Youtube video... people used to watch off-the-air colour TV where the TV in question was made out of less than two dozen vacuum tubes, equivalent to 1-2 transistors each. That stuff is still easily found but in another few decades will also be essentially forgotten.
Oh, and what would it take to manufacture, say, Cibachrome paper and Kodachrome film? I know the Polaroid instant film technology has been laboriously resurrected but lots of obsolete chemical processes are essentially lost.