The setting I'm working on has a parallel world alongside modern-day Earth. This world is Earth-like, though there is somewhat limited magic as well (e.g. people can be transformed into animals and vice-versa), and the overall technology level in the parallel world is Middle-ages (castles, horse-drawn wagons, the usual stereotypical-fantasy setting. ^_~ )

Travel to/from this world is rare, and is through portals which, among other things, transform items being brought through them to the appropriate tech level. So, for example, a shotgun going through comes out as a crossbow, and a chemistry textbook becomes a tome discussing alchemy and potion-mixing. The portals don't affect people's knowledge the same way, though, so something else needs to happen to keep people from, say, learning how to make gunpowder or internal-combustion engines or whatnot in the modern-day world and bring that knowledge across to the lower-tech world.

My plan to keep the world at the lower tech-level despite higher-tech is that certain physical properties in the magic-active world are different enough that knowledge of Earth-side technology won't transfer. Saltpeter + charcoal + sulphur doesn't explode, the Bessemer process doesn't produce steel, spinning a wire loop inside a magnetic field doesn't produce electricity, etc. Also, no or limited coal/petroleum reserves reduces access to concentrated power sources.

So, what foundational technologies would need to work differently, and what resources would need to be limited/restricted, to prevent a Middle Ages-level society from progressing further in technology despite modern-era knowledge being brought in. As to why things work differently, I'm happy to just say "because magic" if needed, I just need to know what to break.

A few I've already thought of:

  • Metallurgy (e.g. limited/unreliable steel production)
  • Electricity & related tech
  • Power sources (limited/no coal or petroleum)
  • Chemistry, esp. plastics & composites
  • $\begingroup$ "spinning a wire loop inside a magnetic field doesn't produce electricity" - be careful when changing fundamental forces like electromagnetism. Easy to make universe impossible. $\endgroup$
    – Mołot
    Commented Oct 16, 2016 at 8:44
  • 2
    $\begingroup$ Just a point, steel was invented in 13th century BCE. $\endgroup$ Commented Oct 16, 2016 at 9:08
  • $\begingroup$ @Mołot - like I said, I'm ok with going "because magic" for things like that. $\endgroup$
    – Salda007
    Commented Oct 16, 2016 at 9:32
  • $\begingroup$ @Bellerophon - yes, and that's fine. I'm more concerned with high-rate steel production methods like puddling furnaces and Bessemer furnaces, where you see steel production on the order of tons instead of ounces or pounds. $\endgroup$
    – Salda007
    Commented Oct 16, 2016 at 9:34
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    $\begingroup$ If "saltpeter + charcoal + sulphur doesn't explode" then life as we know it cannot exist. Just saying. $\endgroup$
    – AlexP
    Commented Apr 26, 2017 at 9:48

6 Answers 6


I think the only really "reasonable" way to do this is basically to say "Magic just makes anything that seems too 'modern' arbitrarily not work".

People are creative, and technology is all based on the fundamental workings of the universe. You can reduce access to some kinds of technology by making common materials for it hard to come by, like making iron or coal rare. But then if the physics of steam expansion still apply, you can still build a steam engine by replacing many of the parts with wood. It won't work as well as a machine made mostly of iron, but it will still work as long as the laws governing pressure differentials (the same laws that allow you to pull air into your lungs) and the laws governing expansion of hot gasses (the same laws that cause hot air to rise) still apply. If you try to change those laws, you break a lot more than just modern technology.

Similarly with the Bessemer Process -- you basically blow a bunch of air through a giant container of molten iron; the oxygen burns the impurities out. AFAIK the chemistry that allows this to work is the same as in small-scale steel manufacturing. Preventing it from working by any means other than hand-waving while still allowing other medieval uses of iron/steel just isn't going to work. And even if you're ok with removing steel entirely, making the refining process not work requires changing combustion. (Or maybe adding an impurity that can't be removed by combustion, but someone could still think of a way to deal with that).

Also, the more you go into detail on why modern technology doesn't work/isn't possible, the more detail people like me will have to be able to pick apart the workings of the world. Speaking for myself, whenever I notice that kind of logical or scientific inconsistency in the workings of a fantasy world, my suspension of disbelief is instantly shattered, and I tend to put the story down for a while to stop and think through just how broken the system is.

On the other hand, if you just you just say "no technology because magic", then there's not really those cracks in the logic to pick at. There's no point where I can notice and stop reading to say something like "but wait, if heat doesn't cause gasses to expand, hot gasses won't rise, so why don't all fires just rapidly die out when the air around them has its oxygen content exhausted?"

tl;dr: There's no reasonable/plausible way to break/prevent only modern technology while still allowing a medieval world to work as you would expect. Just ban modern technology by magic and leave it at that.

  • $\begingroup$ Well put. Note that this still brings up the question of why magic is keeping technology "stuck" in Middle-ages level (and not, say renaissance, iron age or early stone age). Especially if the other reality do have a similar history of lower tech. It could be explained by some special event in either of the worlds' timeline during our Earth's Middle-ages (some cosmic/mystic event that every few millennia "copy-paste" tech level from our reality to the other and locks it? A power-hungry mage siphons all the magic from our world, allowing it to progress but locking tech in the other one?) $\endgroup$
    – G0BLiN
    Commented Nov 20, 2019 at 17:06

You don't have to invent anything, it's enough to have a ruling class on a low level world that discourages progress, search for banning the printing press in Ottoman Turkey & how China nearly went through industrial revolution until the new emperor banned it.

  • $\begingroup$ I don't think that would work long term with people knowing what technology is available. $\endgroup$ Commented Oct 16, 2016 at 10:00
  • $\begingroup$ Knowing about something and being able to make it is completely different thing. Progress is actually an exception rather then rule, it only looks that progress is by default since by miracle it happened in the west, and west spread it , quite often by gunpoint I might add, throughout the world. Usually progress is glacial if any occurs. $\endgroup$
    – Platypus
    Commented Oct 16, 2016 at 10:07
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    $\begingroup$ Top-down control really wouldn't work for this. If a country is refusing to develop firearms and advanced manufacturing because the leader bans them, while their rival neighbor is happily industrializing and cranking out high-capacity firearms and artillery, that's going to go very, very poorly for the first nation. $\endgroup$
    – Salda007
    Commented Oct 16, 2016 at 11:25
  • $\begingroup$ My point is that if a nation sees what is available and then someone turns up offering to give them it then eventually the nation will accept the offer. $\endgroup$ Commented Oct 16, 2016 at 14:36

Technology can't magically just not work

This is in reaction to the answers suggesting that you can magically ban technology from working in your world, thus halting the technological advancement.


There is a great post on LessWrong on why you cannot change one simple reaction without it having consequences too massive to explain away. It takes as example a story where, stranded in a magical land, the protagonist is no longer able to use matchsticks, because technology just does not work there (which seems similar to what you are trying to do). However, the reason why matchsticks work is that Phosphorus is highly flammable. It's reactivity makes it also important for life-essential processes in your body. Thus, the article linked above elegantly states:

If a match stops working, so do you. You can't change just one thing.

After hinting at the underlying physical reasons for the existence of Phosphorus, the article makes the even more drastic point

If you stepped into a world where matches failed to strike, you would cease to exist as organized matter.

So if you do not want to go with "Believe me, don't ask, it's magic", I don't see how you could make it happen.


  1. Technical reasons
    Make resources needed for industrial processes extremely rare. Without combustion engines, a lot of things wouldn't have happened.
  2. Social reasons
    Maybe there is a dominant religion that massively hems technological development. Maybe there is a strict caste system that bans too many people from education to allow for real process. Maybe societal norms are build around physical attributes like strength and endurance and tasks like reading and writing are seen as unnecessary/abnormal/anti-social (depending on how strict you want it). Maybe there was some technological advancement once, but social movements successfully stopped it (on earth, we had movements like the Luddites, who tried to stop the automation of their work, but failed).

  3. Fantasy reasons
    Apart from just handwaving, you could try to come up with some plausible magical reasons. Perhaps there are gods or other mighty creatures that wage war on technology, and nobody is willing to anger them. Maybe there is oil, but getting to it is nigh impossible because of all this damned sentient and overly aggressive plants growing above it?

  4. Economic reasons
    The steam engine was successful because it was cheaper than human labor. What if in your world, magic is so prevalent that nobody would even bother with machines? After all, why would I need a telephone if I can use telepathy? Or building cranes, when I can just magically lift things?


While you cannot just stop technology from working in a magical way without breaking everything, you can still invoke magical and non-magical reasons that explain why knowledge does not get transferred, developed, or applied. I personally favor social reasons, because they explain a lot of curious things in our world, as well, and make for nice backstory.

  • $\begingroup$ I like the various suggested reasons, but the reasoning behind "Technology can't magically just not work" seems too based on scientific thinking - what if the other reality is really just a shared hallucination? or a complex simulation? or literally works according to the whims and wishes of demons and gods? In any of these examples, the logical reasoning behind "matches don't work -> phosphorus isn't flammable -> life as we know it can't exist" simply doesn't hold. $\endgroup$
    – G0BLiN
    Commented Nov 20, 2019 at 17:25
  • $\begingroup$ You are right, it is very much based on scientific thinking. I do not think that framing the AU as hallucination or simulation would get us around that problem, per se, but it might be worth a try. Could even become a huge plot element, when people discover that the portals do not actually teleport across space, but instead just link your consciousness to a simulation. This would also explain the transformation of hardware to the "appropriate" tech level. Might be an interesting answer on its own, if you feel up for it $\endgroup$ Commented Nov 26, 2019 at 12:51

First you need to eliminate high density power sources which really powered the Industrial revolution and pushed us into modern technology. You could significantly reduce the amount of coal in the world which would stop small portable steam engines on things like trains. No trains means no movement of people. This stops social movement and also reduces the sharing of technology. It also stops trade between easy trade between America, with its huge mineral resources, and Europe. No steam engines also means no water pumping, no deep mining, less coal/iron. It is a vicious cycle. This lack of power prevents much electricity generation so no mass production of stuff. Overall the most technology you get it would be 16-1700s level.

  • $\begingroup$ Younr answer sounds plausible. Yet, it would not prevent the knowledge of batteries or elecrical generators. So you could still have wind and water turbines providing electrical power. Those even have the advantage of being simpler and easier to construct than steam engines (and still limit mobility) $\endgroup$
    – Burki
    Commented Sep 10, 2019 at 13:56

An easy solution to this is "cause magic" and the wizard king has banned technology that he thinks is too advanced or the public has very little use for those kinds of things, because they can create a equal quality of life with a small amount of technology and magic.


Here's the easiest solution: Low population. A high tech world requires hundreds of millions of people. People needed to build the tools needed to mine the resources needed to build the tools needed to build the factories needed to build... Supply chains in a high tech world are incredibly long and involve huge numbers of people.

So if you make your population small, and perhaps make it hard for them to trade with each other, you could give them all the engineering and science books we have today and they still couldn't build a high tech civilization.


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