Your comment seems to be about how these technologies aren't useful for us in the present. AFAICT, it doesn't dispute that the knowledge was lost.

An additional interpretation is that you're interpreting my writing as being from someone who thinks that "the Romans clearly built it better" etc.

That's not the point I'm making.

Yes, we have napalm and recipes for it. Yes, we have digital computers that are incalculably better than the Antikythera mechanism. Yes, we can trivially manufacture better concrete.

And that's amazing, for us today, but how much better would it have been if we hadn't forgotten about these technologies in the first place and had continued to improve on them? Heron of Alexandria described building steam engines, what if we had continued to experiment on them for over 2k years? Where would we be now?

The loss in knowledge doesn't matter (as much) anymore in the present, but it has held us back, measurably so. For a thousand years, between the Antikythera mechanism and a few hundred years ago, we somehow lost their equivalent of Kepler's laws, some version of calculus, precision machining, mechanical computing etc. For over a thousand years, we have no records of anyone producing devices that approached or surpassed its capabilities.

What if the knowledge behind that device hadn't been lost and we were 1k years further along into our understanding of mathematics and computing?

That's the point here.

The point is that those technologies were exceptional at their time, but were still lost, and we are poorer for it, because it took away hundreds of years of erstwhile progress that could have been made had we remembered and kept building on them.

Happy to hear how I could make the ending better though!

If you want to make the point that "what if we developed steam power sooner", then sure, that works so long you keep talking about steam power in Ancient Greece. Yes, knowledge did get lost there.

But that's not what happened with the Saturn V. The knowledge didn't really go anywhere. We still have the engines and the designs, they're just technologically obsolete. We're not making them not because it's some lost wonder-technology we forgot how to make, but because it costs a lot of $$$ and there's no profit to be made by sending another lander to the Moon and science funding is scarce. That we don't see the asbestos covers much doesn't really mean anything because the actual knowledge is in the fields of heat management and materials science, and not magazine cover photos.

Just as legacy tech isn’t automatically better than today’s technology, today’s technology isn’t always better than legacy tech. The agency has gone back to the Apollo well many many times for these “technologically obsolete” designs because they effectively solved problems that we haven’t faced in decades.

Example, the CSM’s umbilical connection was a work of art, it had to be reverse engineered from museum pieces for current gen spacecraft, https://www.nasa.gov/mission_pages/constellation/orion/umbil...

The F-1 engine’s turbopump and gas generators had to be taken apart by hand because we haven’t built anything close to their throughput for decades, https://www.nasa.gov/exploration/systems/sls/f1_sls.html

Apollo’s phenolic resin heat shield led to the Phenolic-Impregnated Carbon Ablator (PICA) that was then studied by SpaceX to develop their current PICA-X heat shield.

IIRC, there’s a fairly direct line between the Apollo parachutes and SpaceX, https://spinoff.nasa.gov/Spinoff2017/t_3.html

There are many more big and small examples that I can’t name off the top of my head. From the thermal roll to core sampling, having that knowledge allows us to learn from their experience and do better.

Hundreds of thousands of extremely smart people worked on the program and they came up with some extremely interesting ideas along the way. It’s faster/more useful to have a library of their work to draw from rather than going to the well again and redoing it from scratch.

Consider the massive costs that went into many old structures. Often you could measure them in lives lost during construction.

In the case of asbestos and leaded paint, lives and damage done by having used them.

Now, I do believe we should have people study the past. I still like reading on old programming techniques. But progress is not necessarily held back by not building on what came before.

Or the simple fact that laborers were not paid. Hard to compete against literal slave labor

Servitude labour was more of a thing for castles, Cathedrals were build in towns and cities, with free citizens. Castles were build by nobles and those had servitude populations to draw labour from.

Doesn't exactly sound like volunteering to me.

Me and my s/o, who actually studied a lot of the German cathedrals for her master's degree, went on a tour across a lot of the cathedrals this summer with the 9-euro flat train ticket... it's utterly amazing what medieval people could pull off. If you're interested in old buildings, wait until the successor of the 9-euro ticket comes next summer and go on a trip yourself, it's definitely worth it.

Do you also apply such a standard to modern examples of volunteering?

That said, I think this is just a misalignment in what "volunteer" means. Historically, it was more like "volunteer trees", in that you didn't specifically recruit or hire them. It did not mean that they did not get benefit out of it.

Specifically, if there was a local market, it would have been near the cathedral. And if you didn't have a reliable farm or other plot of land to provide food, seems reasonable to assume your best bet was to be compensated in some form for manual labor.

I believe that knowledge is overrated on the long run. It is methods for knowledge creation what really matters. And incentives to apply the best known methods.

Had you read Bret Devereaux talking on an absence of Roman Industrial Revolution?[1] No practical steam engine before it's time has come. Knowledge is created when it is needed. I believe the same stands for computing. It must be some new demand for calculation that created computing. Probably the development of economics.

[1] https://acoup.blog/2022/08/26/collections-why-no-roman-indus...

You might be interested in Lucio Russo's book The Forgotten Revolution. He describes how the Hellenistic scientific and technical culture which gave us Heron's aeolipile, Greek fire, the Antikythera mechanism, Archimedes' method of exhaustion, Eratosthenes' measurement of the Earth's size, Eucid's axiomatization of geometry, etc.†, was lost. Basically what happens was that when centers of science like Syracuse and Alexandria were conquered by the pre-scientific Romans, the philosophers who weren't massacred were dispersed to the four winds, preserving their knowledge in foreign lands if at all. In later generations, Christian fanatics lynched Hypatia and threw down the Egyptian temples, extinguishing the millennia-long knowledge of hieroglyphics.

Russo reaches some conclusions that aren't generally accepted, but much of the history he reviews in the book is uncontroversial, if little-known — but starkly horrifying.

It wasn't a gradual process of forgetting, but a series of genocidal catastrophes. Similar processes obliterated the House of Wisdom in Baghdad, the Maya codices, the khipu, and in our own time most of the world's languages and folklore, much of the Timbuktu libraries, the Afghan relics of early Buddhism, and the collections of the archaeological museums in Iraq.

______

† I have omitted Roman cement and the separation of gold from silver because I don't have any reason to believe they came from the Hellenistic world.

They're about invasion, shifting power centers, economic collapse, societal decay, religious zealotry, and whatnot.

And indeed, many of the moments where massive progress was made were flukes, not the norm -- very happy coincidences that were unlikely to continue for long.

So the idea that we've lost progress due to "forgetting" makes as much sense as saying that a company shut down because the engineers forgot how to work with the codebase. No -- it was all about much larger events. The forgetting was a result, not a cause.

So thanks for that.

The act of preservation in the now, making copies etc. is kind of like a prophylaxis against an adverse event. We are doing the mundane to prepare for the insane.

Let's consider the problem of media longevity — while, as you point out, it is not by itself sufficient to preserve knowledge, it does seem to be necessary, at least as we currently understand things. (Scholars of songlines may disagree, but of course oral traditions like songlines are even more vulnerable to catastrophic forgetting; even half a century of prohibition can obliterate them.)

If you preserve data on Flash, you need to refresh it every few years before the stored electrons leak away; standard datasheet retention times are 10–20 years, though presumably that's at 80°, so maybe you'll get a few centuries at room temperature. If you can trust in continuity of institutions, this is not a big problem; you just have an endowment sufficient to support a small number of sysadmins who make sure the SSD arrays get resilvered at the right interval, replace broken devices, etc.

But if your preservation medium has to survive the PRC nuking TSMC 18 months from now — or an invasion by a military dictatorship of genocidal religious fanatics who hunt down and kill the sysadmins and burn the archives, as happened with the Maya codices — Flash looks much less appealing (though perhaps still viable; see http://canonical.org/~kragen/eotf/ and https://dercuano.github.io/notes/atmospheric-pressure-harves...).

— ⁂ —

I think this also bears on the question you're focusing on in the post, which as I understand it is more a question of curriculum design than of preserving physical storage media. If the target audience for the curriculum is the next generation, or three generations down the line, you can assume a lot of shared cultural background: shared celebrities, shared neologisms and modisms, shared values in a lot of ways. Hipparchos, by contrast, was writing for Ptolemaios, though he didn't know it. He died in 0120 BCE, and Ptolemaios was born in 0100 CE, 220 years later. Hipparchos was the most recent astronomer he could find to cite in the Almagest.

Amongst the civil warfare of the late Ptolemaic dynasty, none of the succeeding eleven generations had produced new astronomical observations, and the line of philosophical mentorship was broken, at least within the Hellenistic world. This bears quite directly on the problem of lost tacit knowledge you focus on in your post. Even Hipparchos was only able to do his work because he lived in Rhodos, on the periphery of the Alexandrian scientific world, which was sacked by Cassius in 043 BCE after a century of gradual reduction to servitude by Rome.

How do you design a curriculum so that it is still intelligible after eleven generations of cataclysmic cultural collapse, largely under a prescientific genocidal military dictatorship like that installed by the Roman invasion? The solution might look more like the Rosetta Project or the Cult of the Bound Variable and less like Surely You're Joking, Mr. Feynman. If Hipparchos had done a better job, maybe Ptolemaios (and consequently Colombo) wouldn't have gotten the size of the Earth so badly wrong. Maybe Ptolemaios, like Archimedes before the Romans killed him, would have followed the heliocentric model Aristarchos had developed 500 years before him (though Hipparchos did not.)

One of the things I really like about the work that the Long Now Foundation has done and does is that they've defined their threat model and retrieval requirements with precision. They're okay with things being inconvenient to retrieve in the short term as long as they can be retrieved by beings with extremely different tooling in the long-term.

I think depending on the model, the threat form can change. The implicit assumption that I was thinking about while trying to come up with a "solution" (I did emphasize that it's a solution, and not even a good one at that, just my stab at it) was that the information would be for the world of 2070. Or, 2080.

I chose that for two reasons, one was that a lot of people have done long-term things, and depending on how long-term you go, you start getting into really interesting territory. And the second is that there's a need to start from a positive place/assumption (i.e. it's implicitly baked in that our civilization will still be around and kicking at said time without a catastrophic collapse) to make it more relatable for the reader so that they're likely to do something. Even if that something is a half-hearted attempt at documenting their personal projects with a higher degree of fidelity.

Depending on the threat model, the following would change,

    - the information encoded/form of encoding

    - how many copies would be necessary

    - maintenance specs 

I don't have the answer to the fascinating question that you've mentioned. I need to think about it more and we should continue this conversation. Lemme know how I can connect. I'm available via twitter etc. (see profile)

And will do :)

I agree with you point. On the other hand I think if we did not forget anything and kept improving while still having medieval views we might have had exterminated ourselves already.

Dead from climate change most likely.

I don't think this is a possible world in the first place. The knowledge of steam engines and intricate mechanical machines wasn't "lost" by accident: it was lost because there was no good reason to develop it further. The Greek steam engine was a cool demo, neat little piece of stage magic for the temple whose doors it powered, but there weren't any practical applications in sight. I bet it also was a hell of a maintenance burden.

The unfortunate reality of our lives seems to be that technology only propagates as long as there's enough funding for it. That means at least several people have to need it very much to support a single inventor. Many more people if there's a need for extra labor, or expensive resources (such as metals). That's as true today as it was 2000 years ago.

What I'm saying is: the reason the Greek steam engine was forgotten is that there was no demand for it back then, and that's because of a combination of factors, such as:

- It could do only so much, because other important technologies - such as precision manufacturing - weren't in place;

- The things it could do could be served better and cheaper by other means - such as hired, slave[0] or animal labor;

Learning history on my own[1], past the school curriculum, I was surprised to discover that a lot of technology was always there in the background. Medieval times weren't just a long period of stagnation - it's when the building blocks for industrial evolution were slowly invented. A lot of important developments happened in mining, where increasingly powerful and reliable pumps allowed people to dig deeper. The progress here was sustained, because it was paying for itself.

The industrial revolution happened when things aligned just right. The steam engines could be manufactured cheaply and robustly enough, and put to important enough work, that they paid for themselves - which financed their improvements, which opened more net-profitable applications, and so on - creating a positive feedback loop that run so long, it triggered more feedback loops, and turned humanity into proper technological civilization.

Note that there's a lot hiding in the "put to important enough work". The overall political and economic situation of the era was what created the "jobs" for steam engines, and that situation is downstream from technologies developed for sailing (progress in astronomy, healthcare and shipbuilding), communications (the printing press), and many others.

Point being: inventions aren't islands; they can't sustain their existence if there isn't a need for them. The question "where would we be if we didn't forget ${technology that we 'forgot' and 'rediscovered' centuries later}" doesn't seem valid to me.

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[0] - There's an argument I see raised every now and then that historically, technology made jumps when labor was expensive; conversely, cheap labor meant it was cheaper to just throw more bodies at any problem.

[1] - I'd like to say "studying history", but what I really mean is just occasionally watching some high-quality documentaries and reading blog posts by people who (claim to) know this stuff.

I'm not personally convinced of the specific proposed solution, since it's "Just Another Technology", but I wholly agree that the problem exists, and I think you argue effectively for some of the reasons why.

In more ancient times, the process control instead basically relied on "get your ingredients from this well/mine/whatever". So while we actually have a decent idea of what Greek fire is (it's a kind of napalm), we don't have any way of knowing what their actual source of naphtha was, so we don't know what the precise impurities that gave it its best kick were. (I'll also opine that there were probably several different formulas in use, and we may be ascribing properties of different kinds of Greek fire to the same one, which would mean that the search for "the" formula for Greek fire could only ever be a failure.)

This ship-borne version only worked in calm conditions, otherwise fireships were just as likely to set themselves on fire. However, it did do pretty well in the sheltered Sea of Marmara around Constantinople. The fireships probably saved the empire from the Caliphate during the 719 siege of Constantinople by destroying the much large Muslim fleet. That occurred at a nadir of Byzantine power and the height of Caliphate power. Western Eurasian history would have looked very different if the Caliphate got control of the Bosporus then, as opposed to the Turks 700 years later.

That is, it is an odd blind spot to not realize that "barely exceeding the goal" is often far far harder than over building.

Grossly overbuild the structure, so that it is lightly stressed. Don't use any reinforcing material within the concrete (much of the damage that happens to a modern reinforced concrete structure is the result of the internal reinforcement swelling due to corrosion). Ensure that the structure doesn't freeze (water that penetrates the concrete and freezes will cause cracking).

Note that following these limitations would rule out the vast majority of modern concrete structures.

Part of the problem is "ancient Roman concrete" is the epitome of selection bias. We basically know why it's strong, and can basically recreate it, but it would take a very long period of process optimization and corrosion testing to get a consistent product we're sure has a long lifespan.

If you want something to last 1000 years, you may be better off cutting it out of a hard, stable stone (like granite).

How long? 1 year? 10 years? 100? 1000?

If it's not the last option, isn't it worth figuring out?

Actually, you don't have to imagine it. Go watch the show, "Peripheral". This idea of long-lasting concrete was actually what I found myself thinking about just last night watching it, in the scenes of future London.

Or is the tailoring of the mix to the environmental conditions going to be a more significant factor than the components?

There are actually lots of artificial materials that weather more slowly than rebar-reinforced portland-cement concrete. But buildings are huge — a small house commonly contains many tons of building materials, and a large building contains thousands of tons — so the overriding consideration for building materials is that they be cheap as dirt.

In fact, buildings — then and now — are to a very large extent literally made of dirt. And rocks. Bricks? That's clay, which is a kind of dirt. Mortar? That's sand, which is a kind of dirt, glued together with typically a small amount of ordinary portland cement with an even smaller amount of additives. Drywall? That's gypsum, which is the kind of dirt White Sands National Monument is made out of (as well as, in its mineral form, many stunning ancient Egyptian vases) although a significant amount of modern gypsum is sourced from flue-gas desulfurization. Plaster? That's sand glued together with cooked gypsum, except when it's sand glued together with quicklime, which is made by cooking chalk. And of course adobe is sand glued together with unfired clay.

The issue is that costs that seem totally reasonable when you're dealing with gram or kilogram quantities of a material become totally unmanageable when you need a hundred tonnes of it. You can use glass, wood, or steel (the cheapest metal) in more modest amounts, but they generally can't replace OPC.

So, there's a pretty short list of materials that are both strong enough and cheap enough to use as building cements, and which can additionally be synthesized on a building site between grains of sand (as opposed to, say, in a furnace isolated for oxygen, or at 500°). You have:

· the above gypsum, quicklime, ordinary portland cement ("OPC"), and unfired clay;

· tar (asphalt);

· geopolymer cements (milled metakaolin polymerized with waterglass);

· waterglass itself;

· Sorel cement (magnesium oxychloride);

· magnesium oxysulfate;

· calcium aluminates; and

· the phosphates of aluminum, magnesium, and occasionally calcium or even zinc.

Of these, some have worse weathering properties than OPC: unfired clay, Sorel cement, magnesium oxysulfate, and (if cured improperly, in a famous nationwide disaster in Spain a few decades ago which wasn't discovered for years) calcium aluminates.

But there are all kinds of extremely stable materials that would last much, much longer than concrete in the weather, but which are just too expensive to make buildings out of, or which nobody knows how to make big enough pieces of. Soda-lime glass (though foamed glass and fiberglass have uses), aluminum, titanium, aluminum bronze, epoxy "granite", gold, silver, polytetrafluorethylene, sapphire, yttria-stabilized zirconia, yttria, carborundum, silicon, the rubber used for car tires, and so on.

Raise the bar and use diamond.

I used to be in the CVD diamond world. On my honeymoon nearly 30 years ago, my wife and I were hiking in the Himalayas, in Sikkim.

My Dad loved diamonds and used them in his work (geophysical drilling, using diamond bits). He passed a year before my marriage. I wanted to leave a rem meminisse eum a in his honor.

So I grew a 2mm thick x 2.5cm diameter diamond disc. I used some nucleation art to make his first name appear as a texture variation in the faceted growth surface. I left it on a protected ledge at ~ 19,000 feet, with a note that just said “Thanks, Dad”.

That disc, or its fragments, will be around until that mountain gets covered by a lava flow or subducted into the mantle.

Concrete? A thousand years? Let's aim higher. :-)

Structures that lasted from ancient times to today were either made out of giant slabs of stone or had maintenance done on them repeatedly over the years.

Unfortunately...

1. There's no "we". i.e. the entities choosing concrete mixtures and other construction technology do not typically share interests with the people / organizations which inhabit the buildings, except in some very abstract roundabout sense. Which is part of the reason why

2. Concrete construction is usually not engineered to last even a few centuries, let alone "forever". In fact, it is often so poorly engineered (or one might argue: misengineered) that it won't last even a single century, or less than that. Because the principle of costing less money tends to be taken all the way to the point of just barely passing regulatory constraints.

3. ... and those regulatory constraints are often quite lacking. I live in Israel, and a constructor is not even required to guarantee that their building will not-collapse beyond 7 years' time.

4. Actually, a lot of the mass-made soviet-era residential buildings are very well made and almost as good as new (well, considering how they often weren't so great when new). This depends on the specific country, region, period of construction etc.

Practical Engineering has a good video on Roman concrete

https://www.youtube.com/watch?v=qL0BB2PRY7k

Yet still better than US suburbia.