I could possibly develop a working glider with the help of the best craftsmen and engineers available at the time within a year or two. Only problem is gliders are only useful to go from high places to low places, and it’s a one-way trip if you don’t have powered flight to tow them back into the air. I suppose maybe you could launch from a cliff and try to use thermals to bring you back up, but then you can’t really leave the cliff if you want to return to where you left. Of course, you better hope you can even be understood and that people actually take you seriously in the first place.

I could explain the mechanics of a basic steam engine, but I doubt they’d have the capability of building it unless I was also able to offer insights into a bunch of different prerequisite technologies such as machining and metallurgy, which I can’t. Then again, the first useable steam engines didn’t have perfectly honed cylinders or sophisticated metallurgy. I was thinking maybe I could set up some industrial-era machines to be powered by water and gears/belts, but without a lathe, I’m not sure all the necessary parts could be made. Maybe those parts could all be cast and then brought to a finished state, though.

I’d probably just have to settle with advancing medicine and various scientific fields by a few centuries. Not that I’m a genius or anything, just by giving basic tips like explaining germ theory and instructing everyone to frequently wash their hands with soap. Or telling farmers to rotate their crops on a 4-year cycle. Or teaching other scientists how proper science is done. Or saving countless lives from small pox by teaching doctors to inoculate people with cow pox first. Those advancements alone would land you in the annals of history and much acclaim during your lifetime, but you could do way more, too.

Anyone interested in this idea (and/or in expanding their general knowledge of the world around us) can check out The Knowledge by Lewis Dartnell and How to Invent Everything by Ryan North