No Stupid Questions

I'd make some fucking soap.

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

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.

I would fall from a very high place

Probably die

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.

What place do I get teleported to? If I'm teleported to the same place on Earth, then I just fell down several meters into a swamp and am probably going to die here.

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.

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

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 be fucked. I'm not succeeding in the present, I see 0 reason to believe that would be different in 1375.

Use all the science i know from school to helpfully quicken scientific progress and spread trans propaganda

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

I'm in Japan and while I can speak modern Japanese I don't know shit about classical Japanese so I'd be screwed. I'm also not Japanese so good chance I end up getting killed or some shit

I become a scribe or accountant, since I can write cursive, do math, and know some Latin.
There was a monastery within walking distance of my home at that time, so that's where I'd head first.

Prophecy some major upcoming events, subsequently market myself as a saint, grab a comfy church position, sell indulgences, profit. Works in pretty much any era.

Assuming I’m snapped back to the same part of the earth, climate-wise that’s ideal in the US PNW coming out of spring. Plenty of berries and food to forage, and I’ll probably impress the natives with my watch and well made clothes. I can probably get the native tribes to metals, and gain acceptance with my magic hand tool that will briefly shine light at night for a few weeks. I don’t know offhand where copper would be, but I know gold is in the streams, and I know how to placer mine, so I can get some electricity going with that and magnetized rocks from lava flows.

I think first contact would be the key.

Anyone else a fan of Nate Bargatze?

650 years ago this place was a sea. So I’d end up having to swim at least a couple of kilometers. Considering the current sea temperatures, I’d probably die of hypothermia before I could reach the shore.

There's a former nunnery down the road. I suppose I'd try to join. Or maybe find a farmer who's looking for someone to look after his kids because his third wife died in childbirth.

Fly under the radar as much as possible, find a cute girl and settle down and have a lot of kids.