In Back to the Future III, there is a scene where the professor has built an ice cube maker with 'wild west' technology. I'm not actually sure if that's possible, but given a solid understanding of Boyle's law and compression stages, it's something that feels like it should be possible.

On a parallel line of thought - I attend events with re-enactors regularly - medieval era - late 1400s.

One of the things I've pondered - what things could I legitimately make using medieval techniques, but that will cause the re-enactment purists to get upset because the use of undiscovered scientific principles.

Steam power seems a reasonable line of thought - whilst Hero made a Steam Engine, the 'real thing' wasn't really used until much later. Or perhaps - as first alluded to - some refrigeration mechanism.

What else could be feasible?

For bonus points, things I could easily transport to a campsite in the back of my car.

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    $\begingroup$ It's worth looking at the automata that actually were made in that period - they are a lot more sophisticated than most people would expect, particularly towards the later part of the medieval period. aeon.co/magazine/technology/… $\endgroup$ – glenatron Aug 10 '15 at 9:49
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    $\begingroup$ Clay peasant shooting - you just need a length of rope, a couple of shields, a bow and arrow of some sort and a few peasants. Pull the peasants across the fields while getting them to flap the shields on their arms - you can even shout pull if you want - and then start shooting. You'll be a good 400 years ahead of time :) Edit - a lot of reenactors will already know that one though. $\endgroup$ – Darren Bartrup-Cook Aug 10 '15 at 16:17
  • $\begingroup$ I like the foundation idea for this question but it seems really broad to me. Could you narrow it down please? Say to weaponry? $\endgroup$ – Green Aug 13 '15 at 20:10
  • $\begingroup$ Technically, all modern inventions were developed from medieval technology... Resources and inspiration are the issue rather than the era, really. $\endgroup$ – Weckar E. Dec 29 '16 at 21:53

Lightning rods

I remember reading one of Asimov's essays trying to show the importance of them in the fight between science and religious zealots... there had been scientific advances opposed by the Church before, but even when it was stablished that science was right, most people did not care (for example, the Sun moving around Earth or the other way around has no real implication unless you study the movement of stars and planets).

Lightning was the archetypical "divine" punishment, it came from the sky and could kill one or another people almost at random; no one was safe (and of course, everyone was a sinner to begin with). It was easier to explain that, say, floods or plagues that killed saints and sinners altogether.

Now the lightning rod meant that such punishment was controlled. Even worse, if the priest kept insisting that it was an impious invention and refused to use one, then the church would be eventually struck (churches being usually tall buildings) by lightning while the "impious" buildings would be safe.


If I had only known...

Given the metallurgy of 13th century Europe, and a transfusion of scientific knowledge, what inventions could have been made?

Adding a single, large book called the Machinery's Handbook to the library of blacksmiths and armorers in Europe would have transformed industry. A tiny example, is that everyone adhered to the bolt thread counts specified in the Handbook, suddenly bolts and nuts are inter-operable. While mass production may still be a few decades away, the ability to make inter-operable parts cannot be understated.

The Handbook covers such diverse areas as:

  • Mathematics
  • Mechanics and Strength of Materials
  • Properties of Materials
  • Dimensioning
  • Gaging and Measuring
  • Machining Operations
  • Manufacturing Process
  • Fasteners
  • Threads and Threading
  • Machine Elements

Not having to reinvent all these areas gives blacksmiths and machinists a huge leg up. Part of what took so long back then was that standards had to be invented then those who were on a different standard (if any) were dragged into the new standard. Exposure to things that we take for granted, like a standard system of measurements (the metric system) would have blown their early minds.

Lots of things can be made from Iron and low quality steel if you've got a means to make accurate measurements. Many things are easy once you know they can be done.

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    $\begingroup$ Note, though, that such an approach is useless without widely disseminated standardized measuring devices. And these can't be produced without a fairly good manufacturing infrastructure in place already. Nuts and bolts at, say, 6-32 threads will NOT interchange successfully unless everybody uses the same inch within, oh, 10 mils. And machine tools in the modern sense were unknown in the 13th century, so even with consistent standards you simply couldn't get interchangeability. $\endgroup$ – WhatRoughBeast Aug 14 '15 at 0:31
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    $\begingroup$ @WhatRoughBeast I thought the same. Even with a handbook like that and no other references, there's still going to be a lot of fighting over how long an "inch" is. Sending back a rule would be helpful, I guess. :) $\endgroup$ – Green Aug 14 '15 at 2:23
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    $\begingroup$ Still, nuts and bolts made by the same blacksmith would be interchangeable. This way, you brought to your world the replacement part. Something that did not really exist then. $\endgroup$ – Burki Aug 14 '15 at 8:06
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    $\begingroup$ @Lohoris, IMPERIAL FOREVER!!!! :) $\endgroup$ – Green Aug 14 '15 at 12:41
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    $\begingroup$ (Personally, though, I like metric better. It's much easier to work with.) $\endgroup$ – Green Aug 14 '15 at 13:20

Since Green already provided one of the smartest things, i would like to humbly add a small and simple, yet extremely hady device: The lighter.
Since people relied entirely on fire for lighting and heating, and the fiddling with flint and tinger, or the constant tending of the fire, must have been quite a nuisance.
Especially when one needed a small fire fairly quickly, say somewhere out in the fields or in the forests, a lighter should be able to make a huge difference. And if you take a look at a Zippo (R), it cannot bne that hard to create something similar, once the principle is known.

  • $\begingroup$ Well, you do have things like char-cloth, flint and steel, so you're not too far from 'lighters'. Not so sure how you'll go about acquiring the fuel and getting it burnable though - high concentration spirits might do it I guess, but ... $\endgroup$ – Sobrique Aug 14 '15 at 8:27
  • $\begingroup$ I think one might use vegetable oil, maybe add some alcohol. But overall i am quite confident that someone with some time on their hands and an understanding of the concept should be able to find something useful, especially since only the vapors need to be flammable, and the wick helps with that. $\endgroup$ – Burki Aug 14 '15 at 8:40
  • $\begingroup$ An older reply but - I've encountered the concept of a fire-piston - air compression to ignite tinder. $\endgroup$ – Sobrique Aug 20 '18 at 9:43

Reinforced concrete. Given that iron/steel and concrete are both ancient materials, I would have thought it possible to combine them. However, the metal parts would have to be manually created by smiths and the cost of it as a construction material would probably far exceed quarried stone.

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    $\begingroup$ Infrastructure is your problem here. 13th century tech isn't up to the massive demands for steel. It wasn't until the invention of the Bessemer process that this became really economical. $\endgroup$ – WhatRoughBeast Aug 15 '15 at 2:23

I'll give two categories. First, things you can transport in your car:

Water purification systems

Disease was one of the biggest killers in medieval times. Any one of a number of simple technologies could lower that death count, at least for the wealthy. The best options would be distillation and filtration (tubes packed with sand).


Galvanic cells go back at least as far as the ancient Middle East. However, it is not known what use they might have had beyond possibly shocking people. Basically, ancient gag gifts. They could potentially be used for treating metals, but possibly not under the conditions or with the other materials available in medieval times. I am not sure what other uses medieval society might have for low-quality batteries.

Tin can telephones

Do I need to say more? Additionally, other auditory tricks might be useful, like acoustic mirrors, which could be used to send messages quickly within larger cities/fortifications or possibly detect where enemies are located.

Now, things you can't transport in your car (or might not be physical things):


The idea occasionally popped up of vaccines, but the idea failed to gain traction until after germ theory. If you could sell the idea (it seems like a bad one) to the people of the time, it would go a long way.


Gunpowder is fairly simple to make. Cannons are not that much harder to build, and quite obvious once you have an explosive. Introducing gun powder would completely change medieval, architecture, and politics.

Angled walls (star forts)

While it would not be as large of a help without the above mentioned cannons, angling the walls of castles would help to deflect projectiles. If cannons are not around and you are protecting against catapults, the angles would ideally be only horizontal - as a vertical angle could actually increase the damage done.

  • $\begingroup$ I might add more if I think of more. $\endgroup$ – William Kappler Aug 14 '15 at 23:09
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    $\begingroup$ You might want to rethink distillation as a water purification technique. It is very energy intensive. Furthermore, unless you start cranking out usable microscopes, nobody will believe that such large-scale efforts to treat water are necessary. $\endgroup$ – WhatRoughBeast Aug 15 '15 at 2:25
  • $\begingroup$ Angling the walls is not a good idea by itself, since it will make the wall more expensive (if the height is the same), more vulnerable to attacks (if the height is lowered to keep the costs affordable) and will need more troops to defend. Star forts become common not because they did not know how to build them before, but because it was the only effective defense against cannons. $\endgroup$ – SJuan76 Aug 17 '15 at 11:53

You'd be surprised. Making things like wire is harder than you might think. You actually need reasonably high purity materials to avoid occlusions, and you need decent equipment to make the wire. My suggestion would be to explore what tools and materials are needed to make such an anachronism, and make sure you've got similar tools and materials available in the world.

For a sense of just how hard it is to make things on your own, I recommend a TED talk on how to build a toaster.

  • $\begingroup$ Yes, I am thinking there are things that are difficult to make. Iron wire dates to the period in question, and there are documented find of metal pins. Hence why I suggested it. Readily available power was basically just fire though $\endgroup$ – Sobrique Aug 9 '15 at 19:27

My thought would be electricity related - extruding wire isn't too difficult (pins can be made) so creating coils of wire. Making a magnet to start generating isn't easy, but you can create them from scratch using iron - heat in a magnetic field to align the atoms. Initial current you'd have to get creative, but a chemical reaction of some kind (like the potato power source).

Then you've got a generator that you can use to do .. well, all sorts of things really. But an arc-lamp might be a good example of anachronism. Being a source of non-flame based light in an era where such things really don't exist.


I would have thought that you could build a rudimentary bicycle using treadles (chain and sprocket might require more precision engineering than was available). Without pneumatic tyres or shock absorbers it would not be a pleasant ride or particularly practical on the roads of the time.

  • $\begingroup$ There have been some very interesting tyres made from wood and coil springs, that were created during WW2, due to alck of material. The chain and sprocket could be replaced by a belt drive. And shock absorbers: bicycles have been used without them through most of their existence :-) The roads, though, will indeed be a problem, that would reduce the usefulness drastically. $\endgroup$ – Burki Aug 14 '15 at 10:57

Bear with me here, but in essence medieval technology had all the needed bits for rudimentary combustion!

  • Distilling was a practice already known, and alcohol could be made. So, fuel is available.
  • Pistons, likely the hardest part, can be achieved (like most other parts) through moulding and casting.
  • Like another answer mentioned, the principles to build a lighter already available. Mechanically lining this up based on other parts would be tricky but not impossible in order to build an igniter.

Fact is, you could likely build most of Ford's original engine or even improve on it.


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