I think about this all the time. What benefits could I bring to an old civilization, like the Romans? Something that would make me valuable to them. I only have two things I could think of. I could run a school for kids. Teach them about places value. But in a few months those with mathematical minds would overtake my knowledge of math. I could tell them to wash their hands, but i don't know how to make soap. Besides, that just a bit of information. The only thing i can think of would to be a playwright. I'd just rip off TV shows and movies. How could you be of value?
Build a steam engine and boiler, make gun powder, make strong acids and with them chemical fertilizer, bring modern farming technologies, the magnetic compass, how to make steel, hot air bolos, gliders, electrical generation, electric motors, batteries, etc. I could with the knowledge in my brain rewrite history or be burned as a witch.
I think teaching them about germs and hygiene and that rats and mosquitoes carry disease ( plague) would be helpful even if you couldn’t make the necessary medicines. Probably just telling people that these things were possible would be enough to get the ball rolling. I know the first anti biotic was found in bread mold and I know that insulin can be excreted by the pancreas. I have all kinds of knowledge that will get me burned at the stake as a heretic or witch!
Well I think gun powder could be very useful and I know how to make that, perhaps I could only show them the useful parts that didn't involve guns. (charcoal, potassium nitrate and sulfur for the curious but it's getting the ratios that is important)
I'm an executive chef --for over 3 decades now.
I would offer advanced food preservation techniques as well as cooking innovations and sanitation knowledge.
I also know how to make soap.
...and I'm a master gardener and can make beer, wine, and kombucha.
They would love me.
Basic germ theory would be incredibly valuable. I could build a crude steam engine and pump to pull water out of mines, that's what basically jump started the industrial revolution. Or if I was feeling particularly generous I'm sure the Romans could find a use for gun powder and bronze cannons.
Herbology - various herbs , were the forerunner of today's pharmacuitical medications . Asprin , for instance comes from the underbark of the white willow tree , a heart medication, digitalis , comes from the foxglove flowers , valerine , econazia , and multiple others have known benefits to the human body .