Suppose a person from our time is somehow (unintentionally) transferred to Western Europe during the late Middle Ages (circa 1300-1400). In a universe that allows multiple timelines, natural or physical reasons do not prevent him from making any actions.

He doesn't know how he got there (or when/where is he, at least in the beginning), nor does he have anything from the future with him (wakes up in local clothes).

For the sake of story, let's assume this man is educated, talented and relatively young & healthy (i.e. has time to do things). Moreover, suppose that he is ambitious and really wants to change the world, yet accepts his fate and does not search for a way to go back.

Finally, this person is lucky, so he won't be killed/enslaved/whatever immediately, but rather get the chance to learn the local customs and rise to a position of (relative) power quickly.

Now, the question is - can this person significantly impact the technological progress of the civilization (and with it the history, of course)? Or would his knowledge largely die with him?

After all, late Middle Ages Western Europe has, in theory, the resources and tools to create quite a few technical innovations (a steam engine comes to mind). But, on the other hand, he would probably find very few people who understand his line of thought.

Again, let's assume that he has a great starting position and that most things go in his favor (within realistic boundaries).

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    $\begingroup$ There are (AFAIK) three very different "schools" about time travel: "no paradoxes"(try as you may, but nothing visible will change, for one reason or another); "forking"(each time a time travel in the past happens a complete new universe is created, actually making a clone of the universe in the instant of arrive of the time displacement); "resilient universe"(time travel actually changes the past and thus there's a quick adaptation where the universe finds a stable path that include the time travel and actions done in it). You should, at least, tell us which is your universe. $\endgroup$
    – ZioByte
    Sep 25, 2017 at 16:04
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    $\begingroup$ Most people today have a very limited understanding of any technology. Your character must actually know how a steam engine works if he even has a chance to make it in the middle ages. Chances are, if you went to the middle ages, you will have very limited resources to make any advances in technology because of your limited understanding of how to make the technology and the limited resources you'd have. $\endgroup$ Sep 25, 2017 at 16:07
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    $\begingroup$ Have you ever heard of The Butterfly Effect? Just going and talking to somebody could drastically alter the course of history, let alone introducing the steam engine a few centuries early. $\endgroup$ Sep 25, 2017 at 16:08
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    $\begingroup$ Welcome to the site, Alexander. This question cannot be definitively answered unless we know how time travel functions in your world. If your question is simply, "Can a person magically gifted with advanced knowledge affect technological development?" then the answer is trivial: yes. You may want to edit this to indicate how time travel functions; otherwise, this is likely to be put on hold until a clarifying edit is made. Feel free to take the tour to get a better understanding of the site. $\endgroup$
    – Frostfyre
    Sep 25, 2017 at 16:23
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    $\begingroup$ I think your guy will have more chances to succeed if he is a handyman from a small town with a hobby related to electricity or mechanics. He needs to be able to build prototypes for very practical things. Just dropping scientific ideas here and there will probably not work since science advances one funeral at a time. Practical solutions for local problems (especially military technologies) might be more effective in starting scientific and industrial revolutions. $\endgroup$
    – Olga
    Sep 25, 2017 at 21:58

6 Answers 6


I think the answer to that would be made up of these parts:

  1. how educated that man is in science, since that the raw scientific knowledge he can implant in that time period

  2. how skilled is that man in persuasion, diplomacy and cunning. since that would allow him to rise to a position of power and not get overthrown over his radical ideas. We must remember how superstitious people were at that time.

  3. how rich are his surroundings, for him to be successful in changing the world, he has to be able to provide for the people working for him AND to have enough funds to fund his ideas and "inventions"

Assuming he has all three and also luck on his side we could assume he would be able to rise to a position of power (either by economical gains or militaristic excellence, easiest way is probably to commission air balloons and demolish enemy moral and forces) and gain lands and serfs, or workers... now he has a workforce and he could begin the technological improvement

First he would tackle the metal industry - steel was already invented so all is left to do is shape it, into coal engines and rails, now he has trains to move stuff and further his economical power. Also mining and electricity production, really just open the first factories. Second agriculture - reusing feces on fields is easy, and the metal industry would ease manpower on the fields. He could also begin selective breeding in plants as well as in animals. Health - on any territory under his control a sewer system would be built, soap is easy to make and would be the first step in stopping disease, extending lives. Military - even if this man would make enemies - once he rises to power he would be able to defend himself, as even a small army could bomb a larger one from above, or with mines from below. With steam engines even primitive tanks are possible, so even conquest would be a breeze. Trade - with a train that could be made to reach pretty far the man could establish merchant guilds, as profit seekers would seize an opportunity. Other kingdom around would grow dependent on him, and thus his power would grow.

Now our guy has a prospering little haven of a kingdom. It's time to take on social policies and further expend the economy First would be establishing an academy and the rules for scientific method. gathering the best minds around with lucrative work offers, next recruiting and training teachers to spread knowledge and his values into young minds so his legacy would keep on going after him

I think that at that point the trade would spread further and bring to other places the ideas that this little kingdom has to offer. thus scholars would flog to it out of curiosity, capitalizing on ideas of innovation. Grand change is almost imminent, not even A plague can erase that level of change in thought pattern (I'm talking about imperialistic view).

At least that's my bit


Germ Theory : There are few adults in our age who fail to understand that diseases come from smaller-than-visible organisms and that proper hygiene, waste disposal and boiling water can greatly reduce one's chances of catching any number of terminal diseases. Your time traveler is carrying this fundamental knowledge back to an age that has no such understanding.

The first Italian physicians to even conceive of these ideas won't be born for another 200 years. Meanwhile the Black Plague (which most people know was spread by rat-borne fleas) is due in the middle of your target century. If your time traveler could teach the local villagers the fundamentals of germ theory and then get them to exterminate the local rat population, he might create a plague free zone which would strongly support the validity of his teachings. Saving hundreds of otherwise plaque-killed villagers and advancing the start of the modern age of hygiene by 200 years would most definitely have an effect on future history.

  • $\begingroup$ It would change the course of the world though. Perhaps it will not matter to this particular story (if we never flash forward/ back to the present), but there is no telling how much of a massive impact will ripple throughout history because of this. $\endgroup$ Sep 25, 2017 at 17:05
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    $\begingroup$ Good answer, but hand washing took awhile to become commonplace after germ theory was postulated, even among the medically literate, even after compelling evidence showing marked decreases in mortality was published. It'd be more likely that you'd be laughed out of town or discredited by the establishment, much like Ignaz Semmelweis. Also, a minor typo in your answer - being killed by plaque I'm sure was pretty uncommon! $\endgroup$ Sep 25, 2017 at 17:10
  • $\begingroup$ @Nuclear Wang Maybe he doesn't have to convince them to wash their hands...just introduce natural insect repellent. He becomes a limonadier and gets everyone to realize how wonderful lemonade tastes. Pretty soon everyone is piling lemon rinds in the garbage, which the rats love, but the fleas don't, and the plague virus life cycle is shut down. bostonglobe.com/lifestyle/food-dining/2017/06/26/…. Include some interesting strategy on the city he's in for further desired butterfly effect. $\endgroup$
    – N2ition
    Sep 25, 2017 at 19:37

Hmm ... whenever I see questions like this, there seems to be a bias toward the flashy big-technology items. Let's go the other way and look into the ... softer inventions. I'm assuming you'll show up ~1350.

A lot depends on what you -- the time traveller -- know how to do. That said, a general modern education should be able to get you pretty far.

The basic advice: Look around. What do you know about that you don't see? "Invent" that!

Mathematics -- If you can handle it, it might be useful to invent infinitesimals as the approach to calculus. Failing that, publish the equations and techniques you do know and challenge people to prove them. There are geniuses in every generation; with the hints you can drop, they'll get 'er done. Every student remembers how to calculate the deriviative of a polynomial... Show people that and the slope of the secant line, and minds will be blown.

Also, introduce the unit circle and kickstart trigonometry.

Bookkeeping -- Do you know double-entry accounting? People will thank you kindly if you do.

Rifles -- Drop hints that a rifled barrel would make guns a lot nicer. If they doubt you ... invent the football. Show them that gorgeous spiral. ;D

Printing Press -- The idea behind moveable type. Try not to kick off the Reformation while you're at it, though. It kind of trashed Germany...

Copyright -- Didja know copyright wasn't invented till 1486?

Construction -- Practical hoisting gears invented in Florence in the 15th century. You might be able to get a jump on that.

Paperclips -- If you can locate the right kind of stiff wire, you may get some play out of this.

Short story ... think of yourself as the "idea man". You may or may not be able to drive all your ideas to fruition, but you can drop (or sell) hints and jumpstart the brilliant minds of the late middle ages!


As others have mentioned, a lot depends on how exactly lucky your guy is. I see a few scenarios how he would be able to achieve something significant:

  1. Favored supplier/advisor to a king. Being able to construct very unusual trinkets, your inventor can gain favors from nobility and royalty. This would provide him with funds, security and even ability to influence world politics;

  2. University professor. Providing your time traveler is a learned man and he is well versed not only in modern, but in classical studies like Latin and Greek, he can work his way into a place like Oxford or Cambridge. This position would allow him to be heard on all matters of science.

  3. Independent artificer. If your time traveler is a skilled inventor, but fails to connect with royalty, he still can create and sell his inventions, making good money. This position would not give him much security, though.

Regarding possible inventions, it is very important to distinguish low-hanging and high-hanging fruits not only in terms of tech level, but also in quickness of payoff. For example, synthetic dyes would be an instant hit in medieval times. On the other hand, the knowledge of epidemiology and germs, while requires no real tech and is extremely beneficial, would take a while to convince the contemporary folks.

Either way, he should be steering clear of offending the church, or the monarchy, or even misguided, but well-respected academics.


A lot would depend on his “luck factor”. Although he is “smart”, how much does he understand about the culture he finds himself in and its customs? Can he speak the language or the dialect in use at the time and place of his arrival? It would be easy for him to get into a lot of trouble over sorcery and witchcraft before the enlightenment, especially as an outsider with a strange accent – if he could be understood at all. I would say the chances of him being classified as a simpleton, spy or dangerous sorcerer would be high. But he’s lucky so given some luck where might he end up?

Perhaps his best bet is to arrive in a situation where he has access to a very powerful person such as a Baron or similar nearby and can accomplish some deed to impress him and gain his trust. Perhaps he saves the Barons daughter from an attack from thieves? Once he has a trusted friend, he can start to make progress but it would need even more luck. I would say it’s a matter of opinion.


I think the success of such a man is largely the speculation of the creative writer

Education is the first big question.

-We know a great many things now days but a lot of it is specialized or relegated to hobbyist knowledge in lieu of industrial approaches. If he is a computer programmer who games in his spare time, chances are he is pretty screwed. Conversely, if he is a chemist with some survivalist hobbies he could dramatically change the course of human history.

You might could argue that having basic general knowledge of modern things would be more than enough to change the medieval world but you would be mistaken. What good is knowing about disease transmission when you have to jump through these hoops to make it impactful:

  • Fight Religion: Diseases as well as many other natural forces were justified by just about all religious groups as acts of their religion. Christianity in particular during the medieval ages argued that a disease was a punishment from god. Arguing against this notion would likely get you burned at the stake as a heretic like it did MANY other enlightened folk.

  • Life's a Pitch: Just as it is today life's a pitch. You will have to somehow flaunt your knowledge to local lords who will give you money and resources to give them something they want. Unlike today where labor laws protect people, if you failed to deliver in the old days you were likely to be decapitated as a fraud. Back to disease prevention, if you are wooing the local lords with your knowledge on disease prevention and manage to get them to fund you a medieval equivalent of a CDC and it fails...Heads will roll.

  • Language: You might think "I know English, I can easily talk to the natives". If you have ever read Chaucer or seen medieval texts you might notice spelling and verbiage is VERY different than modern English. So much so you will most likely need to re learn English. Try explaining bacteria in medieval vernacular. Worst case you get accused of speaking in tongues and burned as a witch, best case you get considered a foreigner.

  • Customs: Lastly medieval customs are much different than our modern liberal ones. Every thing from the way you dress, the subject you speak of, the way you speak them, to whom you are speaking to have all changed dramatically in the last 600 years. Speak casually to a local lord and there goes your head. Talk privately to another man's wife, hope you know how to use a sword better than him. Want to be tolerant of gays, well enjoy your personal barbecue. Freedom of speech was a radical concept as part of the Enlightenment even to this day it spawns storms. The medieval societies swiftly and efficiently dealt with such radical behaviors.

These pitfalls apply to many other technologies:

  • steam engine: tend to explode very dramatically, if you don't know what you are doing congrats you've effectively made a bomb near very unstable people.
  • Riffling: if you don't know anything about metal working you are just as likely to compromise the barrels integrity and create a bomb.

In Summation

A time travelers effect on history would be largely dependent on his educated knowledge as well as his tact in navigating those pitfalls. Technologies have been lost countless times over because of their inability to cope with those factors. For instance a form of calculus is believed to be first discovered by a Hindu monk something like a millennia ago. It never gained prominence because no one at the time could understand what the heck he was saying.

  • $\begingroup$ The idea that Christians during the Middle Ages didn't use medicine or doctors is stupid $\endgroup$ Sep 25, 2017 at 22:43
  • $\begingroup$ Even the pope consult a doctor in the during the Black Plague $\endgroup$ Sep 25, 2017 at 22:43
  • $\begingroup$ Aye but those doctors worked within the confines of religious explanation. Try telling the pope (religious leader) he and his faith are wrong diseases aren't the work of god and demons but rather scientifically the result of viruses and bacteria so you should wash your hands. Also, a great many of those doctors ended up getting burned (literally) for doing just that. $\endgroup$
    – anon
    Sep 26, 2017 at 19:14
  • $\begingroup$ of course if you phrase it like that yes. But many famous scientist were faithful members of the Catholic Church ( Rene descarte is the first that comes to mind). And contrary to popular belief most were accepted by the Catholic Church. (Capericas was exception not the rule. ) typically if a discovery or invention was practical and could be phrased in such a way that it did not violate Catholic Doctrine the Pope's typically accepted it especially if it could do things like cure diseases. Of Course this really depends on the Pope in power and his views of it subject. $\endgroup$ Sep 27, 2017 at 2:38

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