In my story, there is a man who has an incredible memory. He lives on Earth for the first seventy years of his life, during which time he can recall everything he reads. Through a complicated series of events, he is transported to a medieval setting not unlike Earth during the 11th century. Within about ten years he installs himself as supreme leader over all the land. How many years would it take for humanity (with his guidance) to reach 21st century technology (i.e. computers, rocket ships, the internet, etc.)

There are several considerations:

  • This man has discovered that he cannot die of old age. He will live, in essence, forever unless someone kills him. He is not in a particular rush, but he wants things to move as fast as they reasonably can.

  • He is regarded as a king, and though he rules as a tyrant, he is not worried about a revolt overthrowing him or about anyone setting back his plans via sabotage.

  • He does not care to supply the general public with the technological advancements that are created under his supervision.

  • He is able to gather all the wise people in the land to him to help him.

  • While on Earth, he has not read an incredible amount of engineering books, but he still knows a good deal about technology and engineering.

How many years might it take for him to propel society to his end goal?

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    $\begingroup$ This seems like a story based question rather than a worldbuilding one. You have clearly established your world and it's rules and are asking us how events will play out within it. Such questions aren't a good fit for this site. Of particular note is that you're asking about a character withing your world and the actions they will take to accomplish a particular goal. $\endgroup$
    – sphennings
    Commented Jul 14, 2022 at 20:12
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    $\begingroup$ "Within about ten years he installs himself as supreme leader over all the land" - Old World, including China and New World? In 11th century Earth? $\endgroup$
    – Alexander
    Commented Jul 14, 2022 at 20:59
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    $\begingroup$ (1) All over the land . . . what land? King of England is one thing, voyvode of Wallachia is another. (2) In real history, science and technology progressed as fast as realistically possible from about 1700 to the present. So you only have about 700 years to play with. Of those, about 300 are strictly necessary -- 11th century people have a lot to learn to reach the level of the 18th century. So that overall he might do it about 400 years earlier, i.e., around 1850, but definitely not sooner. (3) VTC as duplicate. $\endgroup$
    – AlexP
    Commented Jul 14, 2022 at 21:04
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    $\begingroup$ Does this answer your question? How Might an Ancient/Classical-Type Civilization Rapidly Discover Advanced Technology? $\endgroup$
    – AlexP
    Commented Jul 14, 2022 at 21:10
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    $\begingroup$ In order to have the skills necessary to raise the technology, he must give it to the people. Then there will be people running the steam engines. Some of these people will dream of something better. One of the main things hod back technical change during that period was expert hoarding knowledge. $\endgroup$
    – NomadMaker
    Commented Jul 20, 2022 at 7:24

7 Answers 7


"He has not read an incredible amount of engineering books, but he still knows a good deal about technology and engineering."

That is not very helpful, at all. There is a vast chasm between "general knowledge" of science and engineering and actually knowing how to make the millions of things which make up the modern scientific and industrial base.

Let me give you a practical example. A trivial example. Something we take for granted in any kind of semi-modern factory.

How does one make a perfectly flat table?

This is called a surface plate; do no cheat! Don't look in Wikipedia! Try to come up with your idea from your general knowledge of science and engineering. It is incredibly important for any kind of precision measurement or precision assembly.

(That was a trick. Knowledge of science and engineering won't help. One needs to know geometry: a plane is the only stable, mutually conjugate surface.)

In real history it was only around 1800 that Henry Maudsley came up with a workable process of "automatic generation of gages". And he did not publish it. Joseph Whitworth learned the process as an apprentice and published it in 1840.

Speaking of Whitworth. He is famous for devising the first practicable standard for screw treads. You know -- making sure that you can take any nut and it will work with any screw of the same spec. We take it for granted. But how exactly does one go about making a standard screw cutter? "General knowledge" won't help.

And there are myriad such examples. How does one specifically make a flat pane of glass? What exactly is optical glass? How specifically is textile or lacquer insulation applied to wire?

For the fun of it, think about a really simple device. A mercury thermometer. The essential piece is a capillary tube of glass with constant inner diameter. They could make those in the early 17th century. How does one actually make such a tube of glass? How would having "general knowledge" help with this pre-modern manufacturing problem?

For a gentle introduction to the intractable problem of knowing it all in sufficient detail to actually make it, I highly recommend Leonard Read's 1958 essay I, Pencil. It describes the vast number of people, each with their own specialized knowledge and skill, who contribute to the manufacture of a simple, humble wood-clad graphite pencil; and pencils are but one tiny little step on the journey from the world of William the Conqueror to the world of Stack Exchange.

All in all, avoiding historical traps and guiding the development of science and technology away from silly medieval ideas might save some 400 years, mostly reducing the time needed to uplift 11th century tech to 18th century level; so that instead of 1000 years they may make it in 600, provided that the oh so wise emperor king does not get bored and stays focused for six centuries.

Oh, and he absolutely must "supply the general public with the technological advancements that are created under his supervision". Science and technology are pyramids; you need all the layers to sustain the smart phones at the apex. The general public has to have access to the applications of the technology, because you cannot really make smart phones if you don't have running water and electric power and air conditioning and electric lamps and stupendous optical devices and so on. And all these need large armies of people to build and maintain.

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    $\begingroup$ In my opinion, 600 years is a "slow road". The benefit here is that the emperor does not need to stay focused specifically on the project. He just needs to lay out the foundation (laws favoring commercial development, new universities etc.) and wait for results. $\endgroup$
    – Alexander
    Commented Jul 15, 2022 at 17:10
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    $\begingroup$ But modern, peaceful co-existence among mass amounts of people is NOT the expected behavior. Life expectancy is also in the 30s during medieval times. Scientific discovery doesn't process very quickly if you expect to die by your 30s. It's only when society specialized and people stop having to farm for survival that you have the freedom to think about science. $\endgroup$
    – Nelson
    Commented Jul 20, 2022 at 2:49
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    $\begingroup$ @Nelson: Life expectancy at birth was very low in the Middle Ages. If you made it to ten years of age then you expected to die in your sixties or seventies. It's just that most children didn't make it to see their tenth birthday. $\endgroup$
    – AlexP
    Commented Jul 20, 2022 at 5:21
  • $\begingroup$ I think you are putting too much emphasis on knowing exact things. Henry Maudsley was not just the guy who invented surface plates, but he was the 1st guy to figure out that they were important to invent. Once you know they are important and doable, you can task a few craftsmen from pretty much any era with figuring it out and they will not take long to do it. $\endgroup$
    – Nosajimiki
    Commented Jul 25, 2022 at 20:54

Not that fast.

It wouldn't take terribly long to get from the Dark Ages to the Renaissance, since low population and constant wars and setbacks, plus the general flaws of feudalism, resulted in progress being quite slow. So, to get to the 16th century wouldn't take terribly long, maybe a few decades.

But, past that point the rate of advancement increased dramatically, and most new inventions were made within a decade or so of them becoming technologically possible. You can't make a steamboat until you have steam engines, you can't make a steam engine until you understand thermodynamics and have precision metallurgy. You can't make a rudimentary computing machine until you have vacuum tubes, you can't make vacuum tubes until you have very precise manufacturing and generators and filaments, which require you to have a good understanding of electricity, etc. This is especially problematic when you consider the infrastructure required to make such advancements. It would likely take at least a century to make it from the Renaissance to the early 1900s.

Then, you get into the problem of the modern age, where no one knows anything because there's too much information to know. Even if this dude has picture-perfect memory, he's not gonna know a damn thing about the vast majority of modern technology. The typical person today doesn't know how to make car, plane, missile, gun, radio, computer, power grid, oil refinery, nuclear plant, or hydroelectric dam. Nor do they know how to make the materials required to do any of those things. So, past the turn of the 20th century you aren't going to gain any time.

All in all, your bare minimum is 200 to 300 years.

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    $\begingroup$ yes, to get this last push to the modern age he will have to get a lot of help from the general populous. so supplying everyone with the knowledge would be a necessity. $\endgroup$ Commented Jul 14, 2022 at 21:08
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    $\begingroup$ 250 years is the time between Newton and the first programmable computers. During this time science and technology progressed as fast as possible, with each successive generation of scientists and engineers making tremendous advances. Now you have to add the time needed to uplift 11th century science and technology to the level of the early 18th century: and there is a wide chasm between them, which needs quite a bit of time to be bridged. $\endgroup$
    – AlexP
    Commented Jul 14, 2022 at 21:13
  • $\begingroup$ @AlexP Yes, this is why I left my answer as a bare minimum. It may be possible that prior knowledge would help accelerate that 250 year period, since a lot of the work done was just to discover the science before anything could be engineered out of it. Bringing back knowledge of thermodynamics, electricity, the Standard Model, etc. would probably help speed things up some, its just a question of how significant of a time save it would be. $\endgroup$ Commented Jul 14, 2022 at 21:31
  • $\begingroup$ @AlexP "science and technology progressed as fast as possible" - learning is still faster than progressing. There are some 200 years between Newton and Einstein, any yet today's 20 years old students can recite Einstein's equations without much trouble. $\endgroup$
    – Alexander
    Commented Jul 14, 2022 at 21:57
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    $\begingroup$ @DKNguyen that's why I am specifically pointing to "low hanging fruits". For those, just knowing can bring quick benefits. Just knowing that there are germs can immediately improve public health. Decades of execution can improve that knowledge, but that is not necessary to have substantial benefits. $\endgroup$
    – Alexander
    Commented Jul 15, 2022 at 23:16

I'm not sure it'll be that much faster than the thousand years it would've taken otherwise

Scientific knowledge is only a part of what you need to get 21st century technology. Take the internet, for example. You need to first mine enough raw minerals for all the cables you need to lay. Which means you need

  • to know where in the world the deposits of necessary minerals are.
  • to be able to actually get to those places. So you need to be able to manufacture ships and planes capable of reaching far away corners of the world.
  • to be able to reach an agreement with the rulers of those places for them to actually let you mine there. Unless this man literally rules over the entire world. In which case you still need to protect the mines from local bandits and so on.

Then you need to actually manufacture the cables as well as the servers, routers and so on. For this you need factories, you can't have medieval blacksmiths building computers. You need to have an educational system to produce enough engineers to run these factories, which means schools, universities. You need to have agriculture that is advanced enough to feed all the people that will be working in the factories and laying the cables and so on.

In short, you need 21st or 20th century society in order to have 21st century technology. And society is not something you can change very quickly or easily.

  • $\begingroup$ I agree with this. I remember reading a rountable discussion of experts on how long it would take to rebuild today's technological society if you landed a thousand people on a lush planet like Earth, equipped with all the tech and books they needed to recreate everything. The consensus answer was, "about as long as it took the first time." Advancement turns out tombe more a function of population size than invention. There's good evidence that things invented in the past came along almost immediately after conditions allowed for it. $\endgroup$
    – Dan Hanson
    Commented Jul 22, 2022 at 0:34
  • $\begingroup$ @DanHanson No kidding. A thousand people all dead in 50 years and busier trying to survive rather than pass on their knowledge that entire time means that in 50 years you have a bunch of books and equipment that no one understands. And that's even if those thousand people somehow each had the the knowledge and skills on the order of a hundred of thousand of people and didn't need to spend all their time studying from the books. What's missing is the ability to do the work of a 100,000 people per person. That's more important than the knowledge. $\endgroup$
    – DKNguyen
    Commented Jul 22, 2022 at 19:00

It takes about a million people with proper education and skills (trained for about 15 years - school plus uni, plus 5 years for gaining expirience)

So the guy is the only source of knowledge, not great, as he is a bottleneck and how fast the information can be written down is basically his speech speed - will take quite a time to write required things down.

Formulating knowledge like tasks also won't work as it requires them figure out things, and it is not much faster.

But let's say he has ability to teach 10 people properly, and them being able to do the same (efficiency of teaching is not that high, so it is a case on faster side of things - this alone will take probably 20-25 years)

So speed of information competency growth in this system will be like - it takes 120 years (more or less) to spread the knowledge in socitiety, for a million people to know, not talking about other things.

Not an exact number, and maybe not a best approach, but him being one source of informatin is a bottleneck.

Making a crucible for iron melting, casting - from scratch - looks like a simple task, knowing some general knowledge, but it turns out, when one try to actually do that, there is plenty of science involved, which you have to read about to understand the reasons for failure and understand what you have to change or adjust, and without that knowledge or understanding - the number of combinations are just to big, and most of them are bad, useless.

  • modern crucibles for that are in section of trade secrets (ppl have their tricks and howto's)

That based on a guy expirience, who tried to do all this - quite an impressive lesson in many aspects.

And in that sense 120y it is an optimistic number in this situation, however not necessarly unreal one. But you have to understand that general knowledge and actual implementation are two huge differences, and as an example you can take microelectronics which you set as a goal - far from any country is capable to produce it today, I mean not that many countries do that, and there are examples when one company in the world holds all the expertiese to do something, and in many cases it about just few companies, etc. Bar is high, and not sure he is capable to have all the knowledge(mean reading speed alone makes it improbable, not talking about tricks part which a random guy does not have access to even for 50y old stuff).

Best he can do is to start the process of development, and he needs to free people from their regular work and switch them to that new one - expanding knowledge, test it, implement solutions.

So in that sense he needs knowledge to make equivalent to school course and few years at uni, scientific menthods, logic instead of religion etc. So as to find some set of solutions whicn allows him to free labor(10-30% of ppl) from one type of work and allocate those humans for that improving technologies work, find resources for it (ore, coal), locations where it is better to do stuff, to build things(big chunk of labor) - production places, energy generation etc.

In that sense it being 150-200 years is an optimistic enough scenario. So it almost the way it happened.

Also you have to have about 100 million of people as total population. And with 10 millions to start and average 1.5% growth rate per year it takes 150 years. 100 million is not necessaely sufficient for all we have today, but some limited version of it - may be enough. So size of population is another limiting factor.

  • aaand you can't conquer them all, or it will become a managment problem size does not match the number of people which can be managed with this level of technologies - so it has to be a growth over time, along the growth of technological capacities and infrastructure.

And remember - micromanagment is a dead end.

  • $\begingroup$ You don't need to train 10 people to know everything your main character knows, because there are already people who know a lot. You just need to train a few people in the areas they are lacking and then send them off to train others. For example: Making a crucible for iron smelting is a technology that has existed for thousands of years. Medieval smiths don't need to be taught to make crucibles at all, they just need to be taught to scorch thier ore to remove Sulphur and phosphorous impurities before putting it into a crucible, . $\endgroup$
    – Nosajimiki
    Commented Jul 25, 2022 at 20:18
  • $\begingroup$ and the finery process for reducing the carbon content after the crucible steel has been made. You could fit all the new information needed to advance metallurgy forward by 300 years on a post card. And even if your information is not exact enough to teach a novice, these guys are already master smiths. Give them the right concepts, and they can experiment and figure out a lot on thier own $\endgroup$
    – Nosajimiki
    Commented Jul 25, 2022 at 20:18

As I read the OP, my brain equated it to something like if someone with "something like" a copy of Wikipedia lived in the 11th century(without external links). I could see it may speed up quite a bit. Ex: Edison inventing the light bulb, yes it ended up being a carbon filament that was the key. But all the time and testing on other elements could be dispensed. Or Lenses invented in the 13 century, but telescopes/microscopes not until the 1600s. Penicillin accidently invented 1928, no reason it could not have been produced far earlier.

The question is however, skipping ahead like this leave gaps in knowledge. How much ancillary information was extracted from all the different filament types Edison's team tried making the light bulb will have been "lost". It takes this ancillary knowledge in many cases to implement discoveries. Yes we discovered penicillin but now we have to isolate and extract it.

I do not think we can come close to accurately quantifying any advancement in technology in "years", as the gaps will hinder some advancement drastically but others hardly at all. You could possibly end up in a world with plastic sailing ships, or actually, on the positive side a good pretext for a steampunk world setting.


Your character would be up against some very difficult cultural problems that are not even apparent to most people today. Forget technology, in the eleventh century there would be difficult conceptual problems. Before the 15th century there was no concept of "progress" they didn't even have a word for "discovery" in its modern sense, back then they would have used "uncover" or similar meaning re-finding something that had been covered up. Even Galileo much later had to resort to saying "I have seen something that no astronomer before me has seen" rather than "I have discovered". because he was writing in latin.

So the twenty first century king is rubbing the eleventh century people up the wrong way from the start. Despite the fact that a few things had been invented or discovered since Roman times they were not significant for people in general and happened so slowly that they did not have any impact.

Your king would have (at best) probably terrorised the populace with attempts at unnatural magic, sourcery and the devils work. Priests would have had serious difficulty explaining what was going on to worried peasants and the king would have difficulty in getting anyone to work for him. The Catholic church might well denounce him as a heretic and or a witch and there would be rampant fear and hostility.

Any peasants that were somehow forced to work for the king would be terrified, continually fearful for their souls and worried that they or their families might be turned into frogs or end up in hell. So their work would not be very productive. There was no proper concept of experimental science then, superstition was rampant and anything beyond the natural cycles of life and the seasons would be seen as suspicious.

Worse still the king would not be able to pull off much in the way of shock and awe experiments or demonstrations given his vague knowledge. As an example he might know about gunpowder and might even know the formula, but where would he get saltpetre? How would he describe what it was? Would he even know where it was found or how to extract it? Assuming somehow he could do that how pure would it be? How well would he be able to grind and mix the ingredients and would the result produce anything more than a vigorous fizzing fire and a few sparks?


The fact he is a tyrant is more important than that he is smart

While I mostly agree with Ethan Maness's answer about how much not knowing sciences himself will slow down the tyrant, I would not be surprised to see things go quicker that 200-300 year because what the protagonist lacks in exact knowledge, he makes up for with known end-goals and the authority to move towards those goals without resistance.

Getting up to mid-19th century technology is not hard. You will have a few blind spots that hold you back here and there, but by in large, if you circulate the basic principles of blast furnaces, metallurgy, chemistry, machining, sanitation, and mass-production into your general population, most early-to-mid 19th century technology becomes immediately apparent. It might take a generation or two to build up the infrastructure and quality of things, but 30-40 years is enough time for a large civilization to go from hand tools to machine shops to industrialization when they know from day 1 what industrialization looks like, and that they must change the way they live to meet their new king's demands to get there.

Things will start to slow down at this point as you main character will be able to answer fewer and fewer science and engineering questions, but it still will not slow down to the rate of our own progress specifically because your time traveler knows what goal posts to aim for.

In our world, science is incremental. Someone first invented the process for generating electricity and had to sell people on the idea that it would one day be useful. Then they figured out light bulbs and had to sell people on the idea that they would replace candles, only once people were convinced that electrical lighting was both practical and the way of things did we see any significant effort to built up the an electrical grid. Only once the wires were in place were investors interested in more trivial uses of electricity like like microwaves, air conditioning, and telephones. All of this took about 120 years in our world. But if you go in knowing for a fact that a generator, an electrical grid, a light bulb, a microwave, an air conditioner, and a phone are all doable and worth while investments, then you can set up teams of people to work on all 6 problems simultaneously such that all of these problems could be solved in 5-15 years.

Going from 1820 to 1950 will still require a lot of work, but by condensing the big discoveries into the front end through parallel development, you make the little discoveries more accessible. By 1950's level tech, your people should be discovering things faster than you can teach them anything, but using your autocratic power, you can still choose to invest your nations resources on developing things that you know will matter like personal computing. Even if you have no clue how those things are made, just letting engineers know what CAN be done and making sure they have the funding to pursue solutions is a huge step in turning ideas into realites.


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