Why No Roman Industrial Revolution? (2022) | Hacker News Reader

Why No Roman Industrial Revolution? (2022)

acoup.blog

Well, commenters made some decent points, but the real issue is that you need a reason, a seriously good reason, to legitimize the expense involved in building an engine.

In the case of The Industrial Revolution, this was pumping water out coal mines, and air in to them. Coal was needed as other heat sources had been largely depleted (or nearly so) in Britain. People generally like being warm. This kind of pressure required the existence of a large population, which required the agricultural revolution to have preceded it. The agricultural revolution was also required because you needed some amount of people to be free of working in food production to have the time to improve and build all of the other required things leading up to automation.

Rome had no agricultural revolution, no need for deep coal mines, rather frequent plagues to lower the population, and plenty of heating fuel.

Possibly helpful context, in case others don't know which agricultural revolution this is:

https://en.wikipedia.org/wiki/British_Agricultural_Revolutio...

Not to mention the significant amount of technical innovation that had already happened in the Middle Ages. To make a good engine, you need to be able to bore cylinders accurately, which depended on cannons having been manufactured and improved upon for centuries.

Lathes are older than recorded history. The Antikythera mechanism required a lathe for it's construction. Romans clearly had access to metalworking capabilities sophisticated enough for clock making. Engines wouldn't be a huge stretch.

> Romans clearly had access to metalworking capabilities sophisticated enough for clock making. Engines wouldn't be a huge stretch.

You're vastly underestimating the complexity of making pressure vessels.

I don't think so. Using the Antikythera mechanism as a basis for metalworking ability possible at the time, brass is a suitable material with many small brass engines of various types seen on youtube. The Antikythera mechanism demonstrates high quality bushings and axles, complex gear trains, precision flat surfaces, and soldering. Everything you'd need, just applied differently.

> with many small brass engines of various types seen on youtube

Fair enough. The problem is more that "the Romans had put functionally no effort into figuring out how to make efficient pressure-cylinders, because they had absolutely no use for them."

The author mentions the Romans couldn’t have built [a Newcomen steam engine] without developing whole new technologies for the purpose (or casting every part in bronze, which introduces its own problems)" without expanding on those problems. Presumably it would be material cost of bronze (or brass) relative to "any profitable use to put it to."

So yes, the Romans technically could have figured out pressure vessels. But they had no need to, and so didn't go through the process of refining their materials and methods for the purpose.

Yes. As the article says, they needed "a use case that could tolerate the inevitable inadequacies of the 1.0 version of the device". A Newcomen engine is a turkey. It's about 0.5% efficient. It's the size of a house with the power of a riding lawnmower. And it took most of a century to advance to a better model.

There's another direction that might have created an industrial revolution. High-quality steel swords were known in Roman times, but they were not mass-produced items. The Roman army did produce swords in quantity, and they had a modest steel-making capability. But the Romans never made it to the Bessemer converter.

The Bessemer converter is a simple, crude device. The Romans could have built one. But the metallurgy of making steel with it is hard. Early versions had serious yield problems - much of the time, the steel produced was terrible. It took over a thousand test runs by one of Bessemer's customers and some knowledge of analytical chemistry to figure out the additives that make the process work reliably.

The demand wasn't there yet. But if someone had developed gunpowder...

Coal was needed because copper was needed because tradeships were eaten by shipworms. The trade with africa, america, india, kickstarted and involuntary financed the industrial revolution.

Re agricultural revolution:

I'm not an expert in this, but there were plenty of Romans with plenty of time to innovate. And innovate they did. They had significant achievements in engineering and construction. I mean some of their constructions still stand today. They also spent lots of time on other things and got pretty sophisticated (politics, negotiations, war, poetry).

So I'm not really convinced that their agriculture practices would have been an issue...

Key thesis:

> Now we can’t cover the entire industrial revolution with all of its complex moving parts but we can briefly go over the core of it to get a sense of the key ingredients. Fundamentally this is a story about coal, steam engines, textile manufacture and above all the harnessing of a new source of energy in the economy. That’s not the whole story, by any means, but it is one of the most important through-lines and will serve to demonstrate the point.

> The specificity matters here because each innovation in the chain required not merely the discovery of the principle, but also the design and an economically viable use-case to all line up in order to have impact. […]

Interesting thought experiment at the end:

> Much of history ends up this way. As much as we might want to imagine that the greater currents push historical events largely on a predetermined path with but minor variations from what must always have been, in practice events are tremendously contingent on unpredictable variables. If Spain or Portugal, for instance, rather than Britain, had ended up controlling India, would the flow of cotton have been diverted to places where coal usage was not common, cheap and abundant, thereby separating the early steam-powered mine pumps both from the industry they could first revolutionize and also from the vast wealth necessary to support that process (much less if no European power had ever come to dominate the Indian subcontinent)? This question, like so many counter-factuals, is fundamentally unanswerable but useful for illustrating the deeply contingent nature of historical events in a way that data (like the charts of global GDP over centuries) can sometimes fail to capture.

Why No Roman Industrial Revolution? (2022) - https://news.ycombinator.com/item?id=39061287 - Jan 2024 (1 comment)

Why no Roman industrial revolution? - https://news.ycombinator.com/item?id=36913766 - July 2023 (different article, 79 comments)

Why no Roman industrial revolution? - https://news.ycombinator.com/item?id=32607187 - Aug 2022 (516 comments)

I'd hazard that it was the lack of a printing press and cheap paper. Why? Because that resulted in mass literacy and dissemination of knowledge, meaning a lot of people can be involved in finding solutions.

I like this line of thought. It's almost like the printing press allowed ideas to be tested at scale unlike any other time in history!

Which is why my foss metaverse is gonna rock!!

I've idly thought now and then what would I do if I was magically transported back into Roman times? Printing press and paper. Both can be constructed from what Romans had readily available.

> I'd hazard that it was the lack of a printing press and cheap paper

Britain wasn't unique in this respect.

The printing press was invented in Europe in 1440, before the industrial revolution. It quickly spread all through Europe.

Right. If the printing press were the critical variable, we'd expect to see broader progress towards the Industrial Revolution outside Britain. We don't. That implies something specifically special about Britain.

I always wondered how far technology can go without advanced metallurgy. Clearly steam engines require good metallurgy, but the spinning jenny and the flying shuttle don't, do they? How much would those advances have changed the Roman world?

you can definitely build digital computers out of wood, and probably out of yarn as well. they won't be as fast as electronic computers, but being an order of magnitude faster than hand calculation is easily achievable, and ought to be enough to give them an overwhelming advantage at calulation — if you have something to apply that calculation to

(by 'digital computers' i mean the conventional, turing-complete kind, not special-purpose machines like the pascaline)

the romans (and the lydians before them) were routinely making a silver halide in order to refine gold from electrum; they used common salt, so they got silver chloride, which is a rather poor photographic material, but adequate to the purpose if your exposure is long enough. so photography was tantalizingly close for over 2000 years before it was finally achieved

because the first record of it is from pseudo-geber, evidently the romans didn't have sulfuric acid, which would have been quite useful for many things. but they had lead, glazed pottery, and nitrates, so they could have engaged in the chamber process

screws for actuating motion were documented by heron of alexandria in the early roman empire, and the screw press dates back further, so you could have built a micrometer

i don't know if you count iron smelting as 'advanced metallurgy', but electroplating was also tantalizingly close since the opening of the iron age; wire, iron, glazed pottery, vinegar, salt water, and copper were all available in every city, so you could easily have built a voltaic pile by putting a bunch of low-voltage cells in series — as some have speculated without evidence was done with the so-called 'baghdad battery', which dates from the sassanid period. but it's not clear what you'd plate onto what; perhaps you could tin-plate some iron, and then copper-plate the tin plating? gold and silver plating would have been out of reach

to me the most interesting aspect of this question is this: what advances could we make today, which in retrospect will puzzle our successors as to why we didn't make them for such a long time?

I'm a materials engineer, off the top of my head, the first thing that comes to mind when you mention access to improved metallurgy is lighter, stronger materials and the impact that would have on construction. That could have lead to larger, taller buildings, stronger city walls etc. Then then probably would be flow on effects since stronger walls means need improved artillery to siege a city etc.

But I think the article did a good job of highlighting that technology developments occur out of local circumstances and requirements. I am no history scholar but I understand the Roman empire was expansive, space wasn't necessarily a constraint so there probably wasn't a huge demand to build larger and taller buildings it would have likely been easier to expand cities outwards rather than upwards.

There was a good documentary series I watched years ago called "Engineering an Empire" they had an episode about the technology of Carthage (Rome's great rival), the series pointed out the city of Carthage had large multi-story buildings shared by several families, kind of pseduo-apartment buildings from what the documentary explained there was much more constraints on space in Carthage as it was very desirable to live inside the city walls this led to the development of this type of construction style. Because of these tall buildings there were more advances in things like plumbing, which was different to what the Romans had at the time. The show also pointed out that Carthage placed more emphasis on Naval power so they had relatively sophisticated harbor design, shipbuilding industries etc.

The Roman housing blocks (which a quick search tells me are called 'insulae') were several stories high, up to perhaps nine stories, although the higher stories would have been extremely undesirable (and almost certainly poor quality), so it's not like Rome itself lacked large multi-story buildings.

The Romans tried to build tall buildings, but they kept falling down, and a decree eventually stopped further attempts. They lacked the engineering knowledge and mathematics necessary, not the desire. Similar story with ship sizes. I think the book "Structures: Or Why Things Don't Fall Down" covers some of it...

The pantheon is a fairly tall building. I doubt the problem was the lack of engineering. Rather that those tall residential buildings were not built by wealthy emperors with access to engineers but built organically, often by the inhabitants themselves and more akin to a vertical favela.

> Clearly steam engines require good metallurgy

If we ignore the ‘minor’ issues of efficiency and longevity which would ‘only’ affect how practical the device would be I am not sure about that ‘clearly’.

So, let’s ignore all practical issues, and just try and build a steam engine that would provide some power for a decent period, ignoring efficiency.

Tensile strength to prevent pipes and the boiler getting torn apart by the steam pressure would be a main problem, I think.

There’s https://en.wikipedia.org/wiki/Wooden_cannon: “Wooden cannons have been manufactured and used in wars in many countries. The wooden parts were invariably strengthened with metal fittings or even rope.”, and (from World War One) https://en.wikipedia.org/wiki/Albrecht_mortar#Design: “The Albrecht mortars […] consisted of a muzzle loaded smooth bore barrel built from wooden staves and wound with galvanized wire for reinforcement”

Those likely didn’t work for long periods, but they did withstand fairly high pressures repeatedly.

So maybe, a boiler and pipes built with wood or bamboo, strengthened by rope could be made to ‘work’ at relatively low pressure for a while.

I would try to line the piping on the inside with clay to prevent steam from weakening the wood.

Next major problem: wood catches fire relatively easily. That’s at about 250°C, though, so there’s a range (about 520K vs 370K or 40% of room) at which steam can be created, but wood doesn’t burn yet.

Water boils at higher temperatures at higher pressure (https://www.engineeringtoolbox.com/boiling-point-water-d_926...), but that need not be a showstopper. The Newcomen engine doesn’t run on high pressure.

It also provides a ‘solution’ for another major problem, that of sealing the cylinder to prevent steam from getting out. https://en.wikipedia.org/wiki/Newcomen_atmospheric_engine#Te...: “The piston was surrounded by a seal in the form of a leather ring, but as the cylinder bore was finished by hand and not absolutely true, a layer of water had to be constantly maintained on top of the piston.”

So, I suspect you could build a steam engine without metals. It wouldn’t be efficient and would be prone to catching fire, though.

Slavery was my first guess, and the article seems to confirm this. The antebellum South was behind the North in technology-driven economy for this same reason.

But in practice it seemed to go the other way around. Once the industrial revolution came, slavery was out-competed by automation.

The only parts of agriculture still done by hand are the parts nobody has invented a machine that can do better. Nobody is out there planting seeds by hand or watering the fields with a garden hose anymore. Whereas the modern replacement (immigrant labor) is still used, but only for the things machines can't do (yet).

I think the person you're replying to implied what you are saying. Technology was a substitute for slavery so it's meant to replicate it at first but unlike human machines, industrial machines can constantly improve

>But in practice it seemed to go the other way around. Once the industrial revolution came, slavery was out-competed by automation.

Only after it was invented and successfully deployed. To get to that point, someone needed a reason to go to the expense and trouble of inventing that stuff. The slavery-dependent economies weren't going to do it: why would they need to?

Rather famously, the cotton gin really jumpstarted slavery in the US south when it had been in a slow decline.

I don't think that slavery is as much a barrier to automation as people think it is. We're biased by the main exposure to slavery being the US experience, where there's a noticeable difference between (free) mercantile north and (slave) agrarian south. Agriculture isn't particularly amenable to automation--not in the early 19th century at any rate--and it's not like the postbellum south suddenly found a renaissance in manufacturing.

There is a ton of stagnant societies out there were slavery is still around. Once the "make somebody else make it go away" bizarr results appear. Dhubais medieval cannalisation comes to mind..

I agree with you, plus if you notice, after slavery in the UK pretty much ended before their Industrial Revolution started.

In the US North, around the time of independence is when slavery there was banned.

In both places the "IR" started not long afterwards, with the UK starting first.

Probably because labor was not cheap anymore, people had to find a new way of production.

Slavery has been banned in the UK since at least the Middle Ages.

With the loophole | caveat that in 1832 there were 46,000 documented British slave owners, most living within the UK, including relatives of Gladstone and Orwell.

    The Slavery Abolition Act of 1833 formally freed 800,000 Africans who were then the legal property of Britain’s slave owners. What is less well known is that the same act contained a provision for the financial compensation of the owners of those slaves, by the British taxpayer, for the loss of their “property”. The compensation commission was the government body established to evaluate the claims of the slave owners and administer the distribution of the £20m the government had set aside to pay them off. That sum represented 40% of the total government expenditure for 1834. It is the modern equivalent of between £16bn and £17bn.

    The compensation of Britain’s 46,000 slave owners was the largest bailout in British history until the bailout of the banks in 2009. Not only did the slaves receive nothing, under another clause of the act they were compelled to provide 45 hours of unpaid labour each week for their former masters, for a further four years after their supposed liberation. In effect, the enslaved paid part of the bill for their own manumission.

https://www.theguardian.com/world/2015/jul/12/british-histor...

Yes, but no slaves allowed in the UK is the key point.

Just slave owners, including the Church of England, and effective slaves via parishes and otherwise geographically and class bound people with near zero options outside the local manor.

Yes, they offshored it to Ireland.

I read an essay long ago that suggested the Egyptians could have built gliders in the fashion of Otto Lilienthal out of papyrus. And that could have stimulated the idea of propulsion in them or in other subsequent societies.

EDIT: I wonder if a Rogallo wing could be made out of papyrus...I'm having a Thor Heyerdahl moment.

May be apocryphal, but I thought I remembered reading that Rome never implemented a real census. Curious about the relationship between statistical management of logistics and industrial development

Funnily, the blog author has an article all about how demography of ancient Rome was determined - https://acoup.blog/2023/12/22/collections-how-many-people-an... By our standards they did not conduct a true census, where you counted everyone, but varied if counting heads of households, or men of military age, or men, women, and children.

What is spooky is that not just one but two of the necessary conditions outlined by the article are straight up resource depletion - the unsustainable harvesting of timber resulting in complete ecosystem destruction, and then the subsequent depletion of the shallower coal deposits. There has been plenty written about the general dynamics of collapse and how when things get more expensive, all the built up complexity starts to fail under its own weight. Here, the need for heating (and specifically heating with coal) provided enough of a demand to motivate the harder work of technology development and deeper mining, but not too much of a demand that would have squeezed society. If no coal deposits had existed, or the technology had not been developed, or the technology wasn't productive enough to keep up as the difficulty of mining went up, or enough deeper deposits didn't exist until the next energy source (oil?) was found we'd be reading a tale about a once great society collapsing, cities being abandoned, or perhaps even another Easter Island.

It puts a little different flavor on the current worries of climate change, resource depletion, and ecosystem destruction. I guess we're just leaping before we look yet again, this time with the whole planet after having used all of the easily-accessible dino juice...

Discussed at time (509 comments) https://news.ycombinator.com/item?id=32607187

Romans had slaves, so labour was cheap. Industrialization requires expensive labour as demand driver. Wasn't there just an article on HN about that?

Edit: Found it: https://rootsofprogress.org/robert-allen-british-industrial-...

> Romans had slaves

Well, so did the British.

Not natively

What do you mean by that?

Haven't read the article you linked.

Though I wouldn't think that industrialisation would require expensive labour since there could be other benefits driving it, e.g. faster production, less wasteful production, etc.

Industrialisation didn't end slavery or it's derivatives either. It just changed to tools of production.

Well, the article I posted directly tackles your hypothesis and argues, rather persuasively, that high labour costs lead those in power to consider industrialization. Therefore, high cost of labour is an input to industrialization efforts, not an output. The machine only becomes worth pursuing when the total lifecycle cost is lower than the cost of sourcing and consuming human labour.

> coal (a fuel you can run the engine on) is of course going to be very cheap and abundant directly above the mine where it is being produced and for the atmospheric engine to make sense as an investment the fuel must be very cheap indeed.

So effectively, once coal was discovered as a fuel where spending small amounts was well worth mining large amounts, steam engines were bootstrapped into product/market fit right on top of the use case.

Fun fact: Modern off-grid pump-jacks operate in a similar manner. They use the natural gas that comes from the well to power the pump that pumps the oil [1].

[1] https://en.wikipedia.org/wiki/Pumpjack

The article posits that pumping water out of mines was the only impetus. I can think of others:

1. pumping water for irrigation

2. driving a hammer forge and a forcing air into a smelter

Neither requires smooth rotation.

> Neither requires smooth rotation

Neither is in an environment "where fuel is extremely cheap so that the inefficiency of the engine didn’t make it a worse option than simply having a whole bunch of burly fellows (or draft animals) do the job."

A smith already has a lot of fuel being used. Plenty of waste heat, too.

> smith already has a lot of fuel being used

Plenty of fuel doesn't mean cheap fuel. The waste heat is more interesting, though I'm not sure any early engine designs could have done anything useful to a smith with it.

Slavery. For instance the technology for windmills already existed at the time, it just wasn't that big of a deal in world with an abundance of slaves. Fast forward to the Middle Ages and you find it everywhere.

As far as i understand the Roman warships for example even regressed during the Empire as from the Battle of Actium Romans got full control over Mediterranean and any naval competition disappeared.

Does the article answer the question why they didn't excavate coal for its superior burning energy density on an industrial scale, even without the use of engines?

The point about having an economically viable use-case is very relevant in today's times. The Romans didn't need engines because they had slaves. I have a hunch that the abundance of "VC money" and high cost of living in rich Western countries actually stifles the demand for many types of inventions and services. There is simply no need for, and no ability to run, smaller, less profitable tools and services due to the demand and existence of massive amounts of financial capital.

One of the first things I noticed when I moved to Ukraine from North America, a country much poorer in comparison, is the existence of many types of shops and services that would simply be "not worth the money" in North America. The abundance of small artisan coffee shops, mom-and-pop tool stores, custom furniture manufacturers, metal workers, etc. I was shocked to find out, when I ordered an office table on Rozetka (Ukraine's version of Amazon), that the seller reached out to me and asked me what height I would like the metal legs to be, because these tables were built-on-order, not mass-produced and stored in inventory, and so it could be custom-built to specification. And then I found out custom-built furniture is totally a thing here. And the cost was peanuts. I have friends in Kharkiv that own small mom-and-pop metal fabs that could build anything you want with a CNC machine or lathe, and it is profitable to operate these types of factories because the cost of running the entire factory with labour and machines is under $10k / month.

Similarly, because of the low cost and high availability of software engineering talent, and the lack of VC money to drive up the cost of engineers, the average quality of software here in Ukraine is much higher. As a programmer, I immediately noticed that the quality and availability of small custom apps for all sorts of stores and services. Kyiv the municipality has a very well-built city-app that integrates with essential city services, including parking and traffic enforcement. If your car is towed by the city, or you get a ticket, you get a notification on your phone, and you can pay and pick up your car from the holding lot by showing a QR-code to police. The app is extremely well-built. Compare that level of technical integration and efficiency with most Western governments' apps, like the infamous CBSA scandal, or Obama's failed Healthcare.gov boondoggle. Software in Ukraine is really, really good, from my barbershop to the the bank. I have a startup in the fintech sector, and you cannot compare the quality and feature-richness of banking apps in Ukraine to Canada or the US.

Necessity is the mother of invention.

> The abundance of small artisan coffee shops, mom-and-pop tool stores, custom furniture manufacturers, metal workers, etc. I was shocked to find out, when I ordered an office table on Rozetka (Ukraine's version of Amazon), that the seller reached out to me and asked me what height I would like the metal legs to be,

But those things seem like the opposite of progress because the productivity in such an economy is very low. If anything the decreasing supply of labor and therefore increasing costs were one of the driving forces behind innovation in late Medieval Europe because investing into developing costly inventions that resulted in higher productivity became much attractive.

e.g. Romans used “classrooms” full of slaves for copying manuscripts for “publishing” in contrast while literacy was seemingly increasing at a relatively fast pace in the 1400s this approach would have been prohibitively expensive (no slaves and literate people had much better opportunities so books were extremely expensive and this created a perfect environment for a printing industry to develop).

> Necessity is the mother of invention

I’d argue high demand and availability of capital are as important while low labor costs on their own (the reason why you find Ukraine so attractive) have the opposite effect. In the case of many developing countries/mid countries being able to export goods and services to countries with higher demand while remaining to be competitive despite of much lower (initially) productivity of course had a very positive effect (however I wouldn’t necessarily consider banking apps with very good UX to be a very good example of technological innovation, almost all bleeding edge stuff is still being developed in richer/highly developed countries and brain drain is a huge issue in Ukraine and other similarly poor countries)

I don’t care whether you call it the “opposite of progress” or “less optimized” or whatever. In my experience day-to-day life is just better and everything is cheaper and more enjoyable when it is NOT highly optimized in favor of megacorps profits. Better UX apps may not be examples of bleeding edge innovation, but it is a better day to day experience. Maybe capitalism taken to the extreme is a mistake for human well being, I don’t know. I just enjoy life more here.

Well yes, I certainly agree that one can enjoy a considerably higher QoL (in certain aspects at least) while spending the same amount of money in a reasonable stable country yet economically underdeveloped country.

> I don’t care whether you call it the “opposite of progress” or “less optimized” or whatever

I just assumed the discussion was about technological progress. OTH I do think that considerably lower costs enable encourage risk taking, certain types of experimentation and other riskier ventures that would be much harder to fund/justify in countries with considerably higher labour costs (and various regulatory barriers and associated costs that probably aren’t an issue in less economically developed countries as long as their legal/bureaucratic systems are reasonable efficient and not thoroughly corrupt). I can’t really tell whether that offsets the fact that many/most capable/talented people are likely to move elsewhere when given the opportunity

> Maybe capitalism taken to the extreme is a mistake

I wouldn’t say that’s the case in much (or any, depending on how we “define” capitalism).

Also you’re certainly wrong about the overall “wellbeing” considering the migration/demographic trends (even before the war) in Ukraine and comparable countries. Certainly it doesn’t seem that a significant proportion of people living there are in a remotely as good position financially as you.

> considering the migration/demographic trends

There is a large "return to Ukraine" sentiment on Ukrainian social media, even during the war. People assumed the West is better, because that's what everyone else thinks. Most people don't think critically and just go with the flow. But many realized that home was better all along. There's even a (smaller) trend of Westerners moving to Ukraine, see for example the TikToker Ellas's Ukrainian Life, a British national who moved to Ukraine and compares all of the aspects of life in the UK versus Ukraine.

> I just assumed the discussion was about technological progress

As a programmer, I consider better UX apps and better finance APIs "technological progress" even if it hasn't reached world-class recognition yet.

I upvote you even though I disagree with your comment.

I have worked for US firms for a very long time. I'm not living in the US and have no family relations to the US. The cultural difference I observed is that the US if fully focused on profit maximisation to a point that can only be described as unnatural.

The examples you witnessed for me are just examples of people doing things because they enjoy doing these things. They don't optimise them for profit, they don't optimise them at all. They do them because it works for them and because it pays the bill.

The obsessive and excessive single goal optimisation of profit is, in my opinion, a cultural phenomenon linked to the US. It's worrying since it is quite an aggressive way of living....

Yes, that’s the point. Profit is more important than human well-being, beauty, culture, or anything else. It’s why I love the moderation of Europe, though even the EU is over-capitalized, hence I chose Ukraine.

I am more interested in whether the Roman Empire could have had an industrial revolution later on if it had not collpsed beforehand. And had spared us a few hundred years of the Dark and Middle Ages.

It’s not like the pace of technological progress was particularly fast in the Roman Empire and the decline had already started ~200 years before its western half was dissolved. Its collapse wasn’t exactly some straightforward event, it had more or less recovered in many ways by the time of the wars with Persia and the subsequent Muslim invasion (which w arguably the cause of the actual “collapse”). Plague and climate change were seemingly one of the primary causes and Medieval Europeans proved to be much more resilient to both compared to the Romans.

There was a gap of a couple of hundred years but Medieval Europeans had surpassed the Romans by 1000 AD both technologically (inarguably) and economically (varied by geographic area).

TLDR, it was cannons. Improvements in cannons so they wouldn't explode on you led to advanced metallurgy required for things like engines. Everything else about the right society, the right conditions, the right time seems unnecessary to me.

Give the Romans fireworks, then someone might notice that putting on bigger shows can be quite dangerous, what if we shoot it sideways at someone instead of up in the air?. You then get better cannons, as you get better cannons you can make them smaller, then you get guns and your metallurgy knowledge allows you to create things such as engines that operate at high heat and pressure.

Cannons evolved from church bell-casting technology.

Cannons were invented in 12th century China and have nothing to do with bell-casting technology. However, bell-casting technology may have contributed to later European improvements in the cannon. Maybe that's what you meant by "evolved from"?

Bells are much older than cannons.

> TLDR, it was cannons. Improvements in cannons so they wouldn't explode on you led to advanced metallurgy required for things like engines.

The improvements in cannons was about precision, accuracy, and speed of making the bore. There is a chapter on this in The Perfectionists: How Precision Engineers Created the Modern World by Simon Winchester:

* https://www.goodreads.com/book/show/35068671-the-perfectioni...

Newcomen got an early idea going, and everyone knows that James Watt improved its efficiency, but even Watt's engine wasn't very good in absolute terms. This is because his tolerances were huge and lots of steam leaked out. It was John Wilkinson's expertise that solved that issue:

> James Watt had tried unsuccessfully for several years to obtain accurately bored cylinders for his steam engines, and was forced to use hammered iron, which was out of round and caused leakage past the piston. In 1774 John Wilkinson invented a boring machine in which the shaft that held the cutting tool extended through the cylinder and was supported on both ends, unlike the cantilevered borers then in use. With this machine he was able to bore the cylinder for Boulton & Watt's first commercial engine, and was given an exclusive contract for the provision of cylinders owing to the lower tolerance between the piston and cylinder and the resulting improvement in efficiency by lowering steam losses through the gap.[9][10] Until this era, advancements in drilling and boring practice had lain only within the application field of gun barrels for firearms and cannon; Wilkinson's achievement was a milestone in the gradual development of boring technology, as its fields of application broadened into engines, pumps, and other industrial uses.

* https://en.wikipedia.org/wiki/John_Wilkinson_(industrialist)...

See Winchester's for more details.

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