It's reasons like this, that I really wonder if someone from today were to time travel into the past if anything they know would be useful at all. Medieval people would probably think we're all idiots.
In the same vein is CJ Cherryh's Foreigner series [2], which tells the story of human colonists who end up lost, unable to find their way home. They instead find a habitable planet with a native population that roughly has 19th century technology and build their space station above it. The station isn't sustainable though so they end up getting stranded on the planet.
So while not time travel per se, the whole subject of vast technology differentials is a rich vein of sci-fi that I personally really enjoy.
As for someone transported to a medieval era, any person with a high school education would have what is, for the time, a highly advanced knowledge of mathematics, astronomy, physics, possibly chemistry, biology, etc to the point where they would be immensely valuable in the right hands I would think.
Look at Europes "discovery" of the americas, and for that matter, look at how the nomads of the world react when they are even today being "discovered" by us civilized people. You could study anthropolgy if you are into this sort of thing, its not really sci-fi, this is the real deal.
> ...most civilisations would encounter just once, and which they tended to encounter rather in the same way a sentence encountered a full stop.
Also:
> The usual example given to illustrate an Outside Context Problem was imagining you were a tribe on a largish, fertile island; you'd tamed the land, invented the wheel or writing or whatever, the neighbours were cooperative or enslaved but at any rate peaceful and you were busy raising temples to yourself with all the excess productive capacity you had, you were in a position of near-absolute power and control which your hallowed ancestors could hardly have dreamed of and the whole situation was just running along nicely like a canoe on wet grass... when suddenly this bristling lump of iron appears sailless and trailing steam in the bay and these guys carrying long funny-looking sticks come ashore and announce you've just been discovered, you're all subjects of the Emperor now, he's keen on presents called tax and these bright-eyed holy men would like a word with your priests.
The entry also notes the similarity to black swan theory [2].
Knowing how to distill hard liquor would make you popular as well.
Paper diaphragm, wax cylinder, a needle, and viola! You're a god! ;)
For example: how do you avoid drinking alcohol if your only sources of drinking water are contaminated? You can boil the water — but you don't know a priori whether the pathogens or toxins in the water can be destroyed by boiling, or how much boiling is needed. If the toxins are things like arsenic, boiling the water will concentrate them, while various kinds of biological processing may filter them out.
And where do you get vitamin C? Tomatoes are a great source of vitamin C, but you can't just go around eating random local tomato-like plants; almost all of them are deadly. Plants like rhubarb have lots of vitamin C, but also lots of oxalic acid. Raw meat is also a good source of vitamin C, but raw meat can harbor many different pathogens. Are you going to build a microscope, synthesize some stains, and inspect a bunch of meat samples to see which ones bear pathogenic bacteria?
And once a couple of your human-subjects experiments go wrong, or just have coincidental unrelated deaths, you're a candidate for a witch-burning.
(Even in the best cases, modern hygiene is not without its drawbacks; the poliomyelitis epidemic is one example.)
- Pasta? Pasta is absolutely amazing. It is an extremely dense source of calories, which doesn't rot, is super-compact, and only requires water and heat to cook. Great for armies on the march.
- Coffee? Coffee's been around a long time, but high-pressure espresso is relatively new.
Other fairly basic staples are newer than you might think, like Potatoes (16th Cent.), Or Tomatoes (17th Cent.)
Edit: Also limes for sailors.
Also without fortifying the flour pasta is calories without nutrients. It's useful as a suplement, but dangerous to live on it long term.
I don't actually know if you can or not, I was just wondering.
http://en.wikipedia.org/wiki/Whole_wheat_flour
Grind whole wheat into flour with a coffee grinder: http://www.associatedcontent.com/article/1593906/make_lowcar... (you can also buy an expensive hand-crank version)
Whole Wheat Pasta recipe: http://www.sugarlaws.com/whole-wheat-pasta
Actually that's a terrible idea. You want lemons, not limes. Really.
See http://idlewords.com/2010/03/scott_and_scurvy.htm for a discussion of where the myth to the contrary came from, and for the complex history of how the proper prevention of scurvy was discovered, forgotten, proved false, and only later rediscovered again. It also discusses why you really don't want to use limes.
The oldest clearest example of science is alchemy. Today we know it's impossible, but back then they reacted a tremendous number of compounds and carefully recorded the results.
Come to think of it, the course of the human present would be pretty different too.
History is full of people who did all sorts of experiments to try to understand how the world works.
It is not necessary to have a goal "understand this" in order to do science, it's enough to have a goal "what happens if I do this". If I do an experiment and find an interesting result, and I publish it, that's still science - even if I have no idea why what I did works.
(Hopefully you'd remember the proofs!)
What was most interesting to me were the people who denied that they had ever come from earth, that all the fantastical technologies of the past didn't exist, etc.
Same goes for a civil engineer; would be very useful in medieval times. Software engineer not so much!
I just wanted to avoid having to qualify my answer too much to a group of people who are (probably) mostly urban. I agree with everything you say.
Just knowing it's possible, with gross engineering parameters, can be half the battle.
They can say that you need 2 wings on the side, and you need to go really fast in a straight line before you can take off. Sometimes you can see the little flaps on the edge of the wing move up and down. Though you can also do it with little planes. And if you want rotating blades then it has to be smaller than planes (helicopters).
This should help a clever person (e.g. Leonardo da Vinci) figure out how to fly.
Someone with a deep and practical (practical being the important part here) knowledge of chemistry at the right place and right time? Could be extremely useful - he should have a leg up on the local alchemist.
A doctor, again with a good practical edge. Just being aware of bacteria and it's dangers, and using cleaner techniques would have changed everything. Discover antibiotics? Pure magic.
Joe average? Computer programmer? Probably fall into the "idiot" category unless you're good at killing people or politics.