What are the requirements for such an endeavour? I am making a novel where the protagonist is reincarnated into a medieval society. His plan is to push forward technology into the modern age. He starts out as an Earl by the way

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    $\begingroup$ Why would you want a transistor in a medieval setting? I mean, what would you do with it? $\endgroup$ – nzaman May 19 '18 at 13:23
  • $\begingroup$ Whatever you can do with a transistor. Like, make a radio or a computer etc etc. $\endgroup$ – Harbinger May 19 '18 at 13:36
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    $\begingroup$ In David Weber’s Safehold series, he does this by taking 9 novels to build modern electronics up through every tech needed along the way. Takes about a century of in-book time. en.m.wikipedia.org/wiki/Safehold $\endgroup$ – SRM May 19 '18 at 13:43
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    $\begingroup$ Welcome to worldbuilding. Can you give your question some more context?As it is now it has so many open points that your problem is unclear. What's the point of a transistor if you don't have electricity, just to say one. $\endgroup$ – L.Dutch - Reinstate Monica May 19 '18 at 13:48
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    $\begingroup$ Maybe I'm missing something, but what's wrong with vacuum tubes (aka valves)? Those can easily be made by a medieval goldsmith with a bit of glass working training, provided the enterprising earl goes ahead and develops the chemistry to roughly the equivalent of the mid-19th century. $\endgroup$ – AlexP May 19 '18 at 14:41

I made a slightly snarky comment earlier on the question, but I decided it deserves a more complete answer. You aren’t just wanting the transistor. You want the tech that enabled it. The problem is that the transistor is useless without a lot of other techs around it. For “radio and computer”, you need a hell of a lot. You need mining tech, which requires advances in architecture to build tunnels deep. You need smithing. You need gears. You need an understanding on light to build a monitor. You need math advanced enough to break down a frequency wave. You need power generation. And so on. The radio, specifically, was nearly simultaneously invented independently in many spots around the world because it was the next obvious tech after everything else that came before it.

In David Weber’s Safehold series, he “builds a transistor in a medieval setting” by taking 9 novels to build modern electronics up through every tech needed along the way. Takes about a century of in-book time. https://en.m.wikipedia.org/wiki/Safehold

Even something far simpler isn’t easy... look at William Gibson’s “The Difference Engine”.

My point is that building a transistor is in theory easy with materials, but practically impossible without industrial setting to give you the tools, math, electrical generation, and motivation to build it. It isn’t plausible unless you upend your medieval setting OR embed your medevial setting inside an industrial society, like a renaissance festival scenario.

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    $\begingroup$ And of course the theory behind transistors also has a long history behind it. It is difficult to create a theory about how transistors work without knowing about electricity... $\endgroup$ – Thucydides May 19 '18 at 13:56
  • $\begingroup$ Thank you for this answer. It was what I was actually expecting. So basically the mc would first focus on mining tech. Am I right? $\endgroup$ – Harbinger May 19 '18 at 14:01
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    $\begingroup$ @harbinger there are many starting points, but I’d start with development of the printing press and the scientific method... that was the BIG kickstarter out of the medevial period. The Chinese, Egyptians, and Greeks had lots of tech and math and construction. They lacked a way to spread that knowledge and a way to coherently build on it. You have to end a lot of superstition to build a transistor. $\endgroup$ – SRM May 19 '18 at 14:10
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    $\begingroup$ Re Safehold: Are you reading advance copies of unpublished books? Because the last book I have read still had the issue with electricity being banned as heresy, with possibility of enforcement by orbital bombardment. $\endgroup$ – Ville Niemi May 19 '18 at 15:30
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    $\begingroup$ Re question: If you want a non-electronic computer, you might want to think about whether you want analog or digital computer. Analog computers are more or less special purpose with lots of gears and were used as ballistic computers in battleships. Digital mechanical computer would be made from pneumatic switches and never took off as transistors and ICs became available. But developing pneumatics might be easier than developing transistors. Never seen it done in fiction though. Probably because it never became popular enough in the real for writers to know about it. $\endgroup$ – Ville Niemi May 19 '18 at 15:37

Thinking too far Ahead

You are basically trying to invent a better flashlight battery before light bulbs were invented. Look into early wireless telegraph transmitters.

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For a power source utilize a simple wet-cell voltaic pile, a primitive sort of battery. Its just zinc, copper, and salt water soaked felt disks piled up in alternating order. It would produce enough electricity to power a primitive spark-gap transmitter.

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You will need alternating current instead of the direct current from a voltaic pile, so an inverter is needed. This is how simple a primitive inverter is.

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For a transmitter You'd use a very large voltaic pile and a spark gap transmitter. It basically produces a very large band radio pulse every time an electrical ark of alternating current is jumped between two contacts which are attached to an antenna. It cannot transmit voices or audio, it simply is either transmitting or not, which can be used for wireless transmission of Morse code.

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Boom, you now have people transmitting wireless Morse code 1000 years ahead of schedule and all you need is copper, zinc, saltwater, and wood.


I think rather than transistors, you're looking for a mechanical nand gate. There's a related question here. Nand gates are a logic gate that allows you to build complete computing systems, including adders and memory.

Combine these mechanical gates with some sort of mechanical clock (water wheel?) and you've got the capability to perform real computing.

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    $\begingroup$ Not really. See “The Difference Engine” (fiction) or the non-fiction history of Charles Babbage’s steam-driven mechanical computer in the industrial revolution. He couldn’t machine the gears precise enough. At large scale, there was too much friction to do useful computations. It takes a lot of power or speed to get ahead of what a human can do in nir head! A lone nand gate doesn’t help you. And the aggregate requires tech. $\endgroup$ – SRM May 19 '18 at 14:14
  • $\begingroup$ More plausible might be “The Three-Body Problem” where massive computations are done in a medevial setting by hundreds of serfs in lines each doing a small part of the computation— in aggregate serving as a modern computer. $\endgroup$ – SRM May 19 '18 at 14:15
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    $\begingroup$ @SRM The difference engine is not even remotely what I'm suggesting. It was a bit of a near-sighted invention. You might not be able to do massively complex computation, but with enough money, I'm sure you could get good enough. Babbage didn't have the money do hire a bunch of clock makers, with Nand gates, you can take advantage of the fact that all components are identical and train people to make them quite accurately $\endgroup$ – bendl May 19 '18 at 14:19
  • $\begingroup$ Just a week ago, I was at an exhibition of a working computing device built entirely out of such mechanical switches. No aspect of it was possible with what I know of pre-Industrial Age tech. Maybe you could expand your answer to explain it to me? $\endgroup$ – SRM May 19 '18 at 22:27
  • $\begingroup$ @SRM I did some searching, but couldn't find an example of a working computer from mechanical logic gates, except for a few tiny lego versions, and Babbage's Difference Engine, which works on a very different principle. Do you have a link to the computer you're referring to? I'd be interested to see if someone has done something similar in real life. Here's an example of some wood gates. It would take a large number of these to do any computing, but it's technically turing complete $\endgroup$ – bendl May 20 '18 at 15:03

Although not a direct answer to your question, you might want to check out "Connections" by James Burke. It's a documentary on the history of science and technology connecting the beginnings of science and technology to what was the "modern" world when it was produced in 1978. Key points to the series surround the connections between discoveries and developments and how one leads to or depends on another.

More directly in answer to your question:

As already stated in other answers, a transistor by itself is useless; you need all sorts of other things to build functional circuits, a source of good quality electrical power (stable voltage/frequency and sufficient current capacity), all sorts of theory of operation of electricity, electrical and electronic components.

You need all sorts of "modern" materials - plastics, ceramics, glass and specific metal alloys free of impurities. Depending on the type of transistor, you may need germanium (how do you identify the ore and extract the desired metal?) or silicon (pure, properly crystalized) and then you need the facilities to properly "dope" them with the correct type and amount of dopant. And then, how do you package and test the result?

Basically, you need to walk the medieval world through all the stages of science and technology that connects us to those times, pretty much in that order. I assume by medieval you mean iron age with the ability to make some steel (sword making). That means improved steelmaking, taking alchemy into modern chemistry - with the ability to isolate many if not most of the elements on the periodic table, developing math to include calculus, working with basic electricity, building steam engines and using them to power electric generators, making precision tools and instruments, building tube-based circuits first in order to make the instruments needed to measure what your semiconductors are doing.

I've surely left out countless intermediate (and essential) steps, but I hope it illustrates the point.


You can make mechanical logic gates. No? You want electric? Ok...

Considering that you say the protagonist is an Earl, I would place the history around the year 1000, taking as reference the Earls of Lade. With that in mind...

Energy Source

We have the Baghdad Battery which can be made to work as a galvanic battery (even if they weren't used like that, we know that works and that technology to make them is very old). In addition, the construction of a Voltaic Pile (which TCAT117 also mentions) is simple, if you know what you are doing. If it were not because of Luigi Galvani's discoveries, the motivation for Volta to attempt to build his Pile would not be there.

As you probably know, building coils and electromagnet is simple too. As long, as you have copper wires and iron rods. Casting iron is old technology for a medieval setting. The ancient knew copper, and the technology to create chain mails - which exist since the fourth or fifth century - can be adapted to create copper wires.

Furthermore, Theophrastus was already aware of magnetite, its attractive power, and where to mine it. If you have coils and permanent magnets, you can make a generator.

Note: With the coils you would build transformers, if you need them.

For making the generator move...


Creating springs in our world would require a few more centuries, however, if the protagonist spend some time developing metallurgy - perhaps with the help of a blacksmith - they should be viable. Once you have them, you can build relays.

While, relays are not full-blown transistors, they are electronic switches, and you can create logic gates out of them.

There is another thing you need to create a computer: a clock. At the time clock work was not fully developed. Gears already existed (Aristotle gave us the earlier description, there is the Antikythera mechanism, and there are mold for bronze Gears found in China dated to early Jin dinasty), and if you know how pendulums work, you can create a device that opens and close a circuit creating rhythmic electrical pulses... which will serve as clock for a rudimentary computer.

Note: If you think a single person can’t design a working primitive computer… go check out Building a Modern Computer from First Principles.

Ah, for the memory you can use the principle of the relays and use electromagnets to flip circuits. Do not build flip flop out of relays (I do not know if that would work in practice, but if it does, it is very inefficient), all you need is a lever that would rest to one side or the other closing a different circuit in each case, and that you can move it with electromagnets.

The technology to make electric lamps at the time would be too inneficient (stick with fossil fuels, and flamable oils, sorry). But you can use electromagnets move objects to serve as indicators. In fact, your memory is rather large; you could label some levers and read it directly.

It is also possible to open and close valves. This will be useful if you want to supply or cut the flow of water.

I suppose a rudimentary step motor is possible too, for instance using a cam (addendum: a lever should work too) and electromagnets to make it turn back and forth, and then transmit the movement via a ratchet. You could use that step motor to turn a gear. For example for a numeric display, or for moving another machine or you could even build a mechanical ALU.


You can build electromagnetic pulse transmitters and receptors as TCAT117 describe them.

Final Note

I assumed year 1000. However, for the 13th century the technology to make wires and springs would be there. If use that for your setting, then there is no need to spend extra time developing stuff.


It is not simply a matter of inventing the transistor. You must ask, "What will power it?"

If you can refine copper to make wire, have magnetite and, lacquer for insulation then you can get most of the way to repeating the work of Tesla using those things and wood. (edit: and glass for insulators)

This will get you as far as motors, generators, distributed electricity and radio - although I am sure the occasional wooden electric motor may catch fire.

This will launch the industrial age - without petroleum distillates.

To create the literal transistor, you need to refine semi-conductors like silicone, germanium, etc. but, I have often wondered after looking at the foxhole radio (the diagram is more explanatory than anything else on that page) if some rudimentary transistor would not be possible using a similar method used to create the diode and providing a charge to overcome the bias (if that would work?).

  • $\begingroup$ Um actually the world is set where magic is real. The power source will be a fictional "magic crystal" that produces lightning when magic is run through it $\endgroup$ – Harbinger May 20 '18 at 16:40
  • $\begingroup$ Bottled power solves a lot of issues — not just running the transistor but also manufacturing it. Harbinger, you should’ve mentioned this in your original question! Still a hard challenge but maybe viable. Maybe. $\endgroup$ – SRM May 20 '18 at 18:35
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    $\begingroup$ @Harbinger Since lightning will utterly destroy a transistor, you will need step-down transformers, also among Tesla's inventions. $\endgroup$ – Willtech May 20 '18 at 21:17

I noticed that a lot of people think you need high accuracy tools to build a transistor, you dont, not if you are building a type of transistor that barely saw the light of day.

The first transistors made, were designed to replace the vacuum tube, and were huge, crude, inefficient, and ugly. But much better then vacuum tubes.

You could make one by hand using blacksmithing tools, if you know what materials to use. The hard part is you would need electricity, advances in material sciences and chemical engineering, in order to understand how make these crude transistors.

But the hardest part of all? Designing the low level instruction set for your first 100 square meter computer would be a nightmare for one person to attempt. (Eniac was the brain child of two geniuses and a team of scientists)

Edit: I think some think I an referring to modern nanometer transistors made in integrated circuits and that i am claiming they are "easy" to make. I am not, as even with our practically pure silicon and germanium their are still tons of gates that fail due to impurity, hence why cpu companies sell cups that are practically identical to each other as different chips because they had to disable certain cores, due to gate failures.

But large centimeter size transistors are makeable by people in their backyard. You just need the right cookbook, a lot of time, and enough money to pay for your many, many failed attempts.

This is true of a lot chemistry though, because it's the recipe that is hard to discover, one the recipe is written down it becomes simple, hence why it took a genius to realize nitro glycerine could be stabilized by mixing with powdered shell or clay and some type of sorbent, but anyone who can read can easily figure out how to do it today.

  • $\begingroup$ the first transistor was demonstrated in 1947, but the first commercial use came in the 60es. So the first transistors were not better than vacuum valves. $\endgroup$ – L.Dutch - Reinstate Monica May 19 '18 at 14:33
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    $\begingroup$ Oh really? Can you make high purity silicon or germanium without an advanced chemistry laboratory? Do you even understand how pure the materials have to be? (Those old-school huge power-hungry transistors of the 1950s and 1960s required 99.9999% purity; today we use three more nines.) Can you control doping the material with high purity boron or phosphorus to a precision of a few parts per million? BTW, doping is typically done with gas phase deposition... $\endgroup$ – AlexP May 19 '18 at 14:34
  • $\begingroup$ @L.Dutch The Regency TR-1 transistor radio was put on sale in November 1954, and was the first practical transistor radio made in any significant numbers. $\endgroup$ – Michael Harvey May 19 '18 at 14:55
  • $\begingroup$ For the materials, yes you need to purify them, which requires chemical engineering knowledge, you need to know melting points, catalysts, and the proper steps and you can make very pure subststances. Germanium is extracted from germaniferus zinc by distilling it under a non-oxidizing atmosphere (made via chemical engineering) then reacting it with clorinated water creating germanium tetrachloride, which you hydrolisuze to create germanium oxide, which can be reduced to form pure* germanium. *purity is relative, and the germanium can be further purified using another step $\endgroup$ – Garret Gang May 19 '18 at 15:50
  • $\begingroup$ We have had non oxygen atmospheres since the late renisance. Chlorinated water and hydrogen gas are both easily made by technology that was used by alchemists since the medieval ages. The transistor itself took 10 years to develop from when it was first imagined in 1925, and basically boiled down to get gold tinfoil and cut a slit in it with a razor and use that as the contact over a "pure" germanium doped silicon wafer. It's not creating the transistor that was difficult, it's the new branch of quantum mechanics that was invented to understand and predict how the transistor would act $\endgroup$ – Garret Gang May 19 '18 at 15:57

As others have mentioned, a transistor isn't much use without the context surrounding it. Aside from the physical problems (precision engineering, proper materials), there's also an issue of purpose. If you're not doing complex math or managing large numbers of things (people, dollars, livestock, etc), then a transistor won't necessarily accomplish much.

Maybe consider a Water computer? I'm not sure if one has ever been made, but the principles of transistors can be applied to fluid systems as well, with a few tweaks. As the article says, though, this would work on the order of millihertz, not megahertz, and could very well be slower than human calculation. It's also only useful for mathematics - no way to use it in a radio, for instance.

One possible benefit is the ability to perform algorithms to remote places without training mathematicians. A skilled craftsman could create the computer and the locals could do routine maintenance, with neither understanding how the system actually works. A book of designs could describe multiple requirements, so an algorithm would only need to be designed a single time before being deployed around the kingdom. If you needed to calculate something like "optimal flexibility of a catapult with length X", locals could use the computer's results without needing to learn the math behind it.

That said, I'm having a hard time coming up with an example where on-the-fly computation would be a better than a simple table of numbers, and it's almost certainly more efficient to simply grab a bunch of peasant kids and teach them math over a decade.


Building semiconductors would be pretty impossible in the era you have described.

There are a few different sorts of computers that are simple mechanical devices. https://www.kickstarter.com/projects/871405126/turing-tumble-gaming-on-a-mechanical-computer

I had one of the following computers. It was programed by moving the position of straws. You used a shuttle action to make it work. https://en.wikipedia.org/wiki/Digi-Comp_I and https://boingboing.net/2006/02/21/mechanical-computer.html

Look here https://www.google.com/search?q=homemade+mechanical+computer&newwindow=1&client=opera&sa=X&biw=1098&bih=546&tbm=isch&source=iu&ictx=1&fir=FWSssgxA0NJkRM%253A%252CCzcCkGNbCgdh-M%252C_&usg=__6zxnuLtlTQeP4HMHoV3fyll76b0%3D&ved=0ahUKEwjageL9gJbbAhWOt1MKHYxQCsYQ9QEIMzAC#imgrc=FWSssgxA0NJkRM:

You may also perform logic with relays if you want it to be electric. Steam power could flip flop valves.

  • $\begingroup$ Good idea, but expanding and formatting the post would bring more upvotes. ;) $\endgroup$ – Oleg Lobachev May 21 '18 at 14:17

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