No Stupid Questions

I would teach London children the most obnoxious brain rot slang from today as a laugh.

I would warn the Native Americans about the Europeans

probably die

This is something I often wonder about, what could one person even do with all of today's common knowledge? You can't very well just invent the printing press and have the same impact as Gutenberg - you need something what the few people who can read would, and most people can't translate the bible from Latin into renaissance German and/or don't know enough about the catholic church to write scathing remarks on it like Luther.

You can write and read - that's something. Maybe more importantly, you can do math with arabic numerals - boom, easy accounting job. With a bit higher education, you may even just invent calculus once more. You know how long it took for people to figure out you can put pi on the number line? Proving all the formulas in your head is the hard stuff, but you have a head start just by knowing them. We all clown on the wormhole explanation with the paper, but it does prove Euclid wrong 400 years early.

Ah, and you can just become a medical genius by using soap and bandages - "do no harm" is better than most.

Fuck you buddy, I'm barely getting by with modern medicine, you just ended me.

I’d be dead in the vacuum of space. You never mentioned that I’d just go back in time, you forgot the coordinates. Now I’m floating, dead. Thanks man.

I'd make some fucking soap.

Die as you forgot to teleport me to where the earth was at the time.

Otherwise I guess my main knowledge that could be useful is some basic first aid. Secondary to that, a little bit of electrical stuff.

Nobody would be able to understand me because English has diverged so far from 12th century English that it's a different language. Also I'd be in north America where nobody had even seen a white person. Additionally, I'm 20 ft above the ground right now in a building that didn't exist back then. Finally, I'd be rightfully blamed for bringing plague to the native tribes of the area and likely killed.

Assuming those hurdles were all cleared: I'm a mechanical engineer. So, I'd tell the natives where iron ore, coal, and oil was buried and how to extract and refine it. Tell them how to make gunpowder. Speed run making steam engines and lathes. Get north american natives armed, industrialized, and organized against the external European threat.

Die a slow death from hyperglycemia once my pump runs out of insulin.

Infect the indigenous population with some god awful pathogen they have no defense against.

Die to a pathogen I have no defense against.

Die to the indigenous population due to being a white dude in pre-contact North America.

It uh... wouldn't be pretty.

Wouldn't I be in like empty space?

Unfortunately in that circumstance, I'd likely be a horrible vector for disease. Not much chance of survival if I spread devastation wherever I go.

England is in the midst of the Hundred Years war with France and considering I'm ~193cm and the average height of a man in England in the 14th century is about 171cm... looks like in getting my arse drafted and shipped off to France, to act as some kind of intimidating presence. That is until I have to swing a sword, which my body, that's used to sitting in an office looking over excel spreadsheets, absolutely can't do, so I get bum rushed/hit in the face with an arrow and die.

That's the most likely scenario.

Worst case scenario, considering I don't speak middle English or Latin, I'm treated as an enemy and locked up in a dungeon somewhere.

I don't think there is realistically a best case scenario

Well, I'm in Australia so I would try and communicate with the indigenous population and teach them how to defend themselves against the upcoming colonist invasion and take advantage of what they have to offer, starting with forcing a signed treaty.

I would fall from a very high place

Many years ago when I thought about this, I realised I wouldn't be able to put much of my modern knowledge and skills to use. I decided I'd learn to make basic matches by distilling urine into phosphate, which wasn't invented until the 19th century, but I've forgotten the process. Collect lots of urine and boil it? Also, if you make white phosphate it can cause horrific toothache and they have to remove your jaw... So, I'm hoping another commentor will suggest a safer skill I can brush up to be ready for travel.

Probably die

Basic geography could go a long ways, if people believe you. At this point people were exploring the world trying to find the spice Islands, but didn't know WTF they were doing. Magellan navigating the strait that would be named after him was impressive at its time, but now we know the best way from Europe to Asia (and spices and stuff) by sea without any modern canals is by going around Africa. Like, it still sucks and it's a long trip but it's doable compared to going to damn near Antarctica.

This assumes I don't die, can communicate, and am not in the then-unpopulated (and quite landlocked) current location of Denver, Colorado.

Edit: bonus fact: if a sailor managed to smuggle a knapsack full of cloves back, it was worth about as much a house

I don't think I know a single language from the time, so I'm probably getting murdered because I'm a strange foreigner who can't defend themselves with words.

Hope that I don't start the early spread of New World diseases to indigenous Americans

And I'd be dead by the end of the week

I would die quickly because I don't have any wilderness survival skills and the land I live in (USA) was inhabited by hunter gatherer tribes whose language is completely unrelated to anything I know and whose customs are completely unknown to me as well. But beyond that, even if I got teleported to England where I at least know a similar enough language to where I could figure out middle English decently quickly, I think people seriously overestimate how useful just having modern knowledge is.

For example, say you want to build a gun. Do you know how to forge a gun barrel with medieval steel and make gunpowder out of bat shit and sulfur? Because I sure as hell don't. I could probably make gunpowder but how the hell would you get the money to pay someone to make a gun barrel for you? And further, even if you had the skills yourself, basically nobody today deals with raw materials as inconsistent as what they were working with back then and therefore don't have practice working with them. Even if you introduced something like germ theory to them why would anyone believe you? You'd probably get just as sick as everyone else even with following modern sanitation standards for yourself because nobody else would be. Same with math. Want to speedrun introducing calculus to the world? Good luck trying to prove it to medieval mathematicians without having deep knowledge of euclidean constructive proofs and philosophy to even allow for something like an infinitesimal to exist. There's very little one person can realistically do to change the world on their own.

Edit: I’m taking the middle road here and assuming something around year 1250 or so, not 1100 or 1400 as confusingly set in OP.

Okay, so unlike most other scenarios, I think I would be fine for a while at least. The peoples living where I live would have made and kept more or less regular contact with the sons of bitches from the south that would later crusade us (or I think maybe one of the crusades is presently ongoing at the time…) so while I would both introduce and be hit with diseases or more likely strains of familiar ones new to my body/their bodies, I think it wouldn’t be as destructive as entirely separated landmasses like America vs Europe.

So if I survive the shock my body gets hit with, and I don’t kill everyone around me, I think I would be fairly well received. As far as I’ve read, the languages and dialects were different than after the formalization of the written form, and at this time these lands were just starting to get forced under Swedish rule, so with my basic understanding of Swedish and of course my native language, I think I would be able to communicate well enough to not get instantly killed as a demon or something.

I think my best bet would be to introduce myself as some sort of demi-god, a bastard son of the god of forests and the hunt probably, which would hopefully explain my alien attire and materials used to make them. And the alien accent/dialect of both the local language or Swedish, depending on where I’d land. If the first contact I make aren’t local but crusaders, I suppose I’d have to try and push myself as a wandering preacher of Christ or something. I’d have to hope they’d speak Swedish, since I do not know German well enough to form two words together, and they’d likely be the next likely encounters. Novgorodians I think were fine with the Swedish language in general, so if our current knowledge of history was off enough that I’d meet them here, I’d still be fine. No idea what I’d pretend to be to them though. My limited knowledge of history doesn’t help there. But as far as I understand, they were sort of a melting pot of close-by cultures, and not so focused on these lands at this time, they’d just take me for a local hermit and let me run off clumsily.

If I was able to survive the first encounters and get myself to a village or a hillfort, I’d try and establish myself as a wise one, helping with calculations and engineering and whatnot to the best of my capabilities, which I would think honestly should far exceed those of the locals at the time. So maybe I’d get by just for being useful and knowledgeable.

But I don’t think I’d live a long life. These were a turbulent and violent time and one village elder or the other, fancying themself a king or whatever, would just send assassins to off me for being an asset for the local leader where I’d end up in.

Even if I’d travel to avoid this problem, it probably wouldn’t take until my old ages to have someone or something off me just by happenstance. And I wouldn’t want to live a hermit in a time where internet or computers aren’t a thing. I think the only way to cope would be to focus on a family, try and bring up children and have that fulfill my life as best it can, as long as it can.

Honestly, I consider myself lucky in this scenario. We still have our language alive and in use, the same the locals would speak at that time. This together with the general superstitious nature of the local tribes — which the crusades and Christianity, with overt blood and sadistic violence, would (thankfully later, I hope for my sake here, at least according to our current knowledge) succeed in some amount to water down and turn them to its specific flavor of lame ass superstition — would make it probably at least somewhat likely I wouldn’t be killed on sight or something to that effect.

Do my best to warn the locals of the coming invasion. Learn their language and teach them English and tell them not to trust any group of strangers who speak it.

Help improve their technology as best I can. I’m not sure how much I’d be able to improve it. At least, teach them to wear masks and wash their hands when around sick people.

I'd try and hold my breath to not set off the European diseases into America early.

I would use the superstitions of the people of the area to scare them away from me and my space. I would build a Catalan forge and a smelter that is powered by falling water. I would make gunpowder but not share the recipe. I would also distill alcohol for sale and for hygiene. I would use Leedskalnins PMH to create permanent magnets and use them to make electricity. Electric fences also help keep the superstitious barbarians away. I would also be a beekeeper.

650 years ago, the place I live was inhabited mostly by the Ojibwe (a Native American people), so I suppose I'd try to find some of them and try to convince them to not kill me and let me stick around long enough to learn their language. Then I could teach them some of my knowledge. Maybe by the time the Europeans come along they'll be a bit more prepared.

If I can't find anyone, I don't like my chances of surviving for any significant amount of time. Maybe I could make it a few weeks foraging for food and fishing or something, but realistically I'll probably end up starving.