Then somehow out of your hands, the time machine takes you to the time of ea-nasir, and you wind up learning the language just to write a strongly worded tablet.

Except you end up before the Bronze Age with people asking “what is this metal you speak of?”, in whatever language you definitely would not know.

No, but i do know the average velocity of an unladen swallow...

You also need chargeable batteries, so you need

1. The Anode - Lead Dioxide, a mineral called Plattnerite yields it, or it can be obtained by heating lead metal in open air at 600 Celsius and then turning the resulting Lead Monoxide powder into Red Lead via calcination which is just heating it again. Do your best to turn it into a plate form, perhaps by smelting some conductive material like copper onto it, idk.

2. The Cathode - Pure Lead plate

3. Sulfuric Acid - You can find Sulfur as a mineral, then mix with saltpeter, and then burn it to create sulfur oxide which if piped into water will produce the acid.

4. Glass fiber plates to place between the Anodes and cathodes so that they do not touch

5. A container, likely a ceramic.

Notes: Saltpeter can either be mined or obtained by soaking bat guano until small crystals form and then filtered out. Since this is a liquid batter it has to always be kept upright.

The Qing empire concluded steam engines were "clever, but useless" to actively harmful, and thats after seeing them in the rest of the world. Rome built a steam engine, and didn't particularly care as they had slaves for productive work. The Ottoman Empire used steam to turn kebab, and that's it. Spain (and every other empire) actively sabotaged industrial development in the colonies, since that represented competition, and production of higher-value goods means less cheap labor and resources. Today we can feed everyone, but don't because its not profitable. We could educate 10x more scientists, but choose not to.

The point is the bigger blocker isn't scientific knowledge, but social development.

The highest reward:lowest memorization ratio has got to be introducing people to Pasteur’s spontaneous generation experiments, and it’s not even close. That kick started the modern understanding of germ theory and revolutionized healthcare, and all you need to demonstrate it is someone that knows how to blow clear glass.

Pretty sure you're a witch.

- those ancient folks probably

I feel like you would be able to describe the concept of a metal that seems to stick to other metals and you would like to be able to find a magnetic material they do occur naturally

Boiling water will be involved.

They knew it existed but they didn't grasp a use for it. If I recall correctly, some cultures made primitive batteries and steam engines and just used them as a party trick/religious focus to zap people or make little toys move.

The real technology booster would be cheap paper and the printing press. Second best would be materials science tech, letting them have processes to make cheap and durable tools and instruments. That stuff took millions of man-hours of trial and error to figure out.

Don't worry. I know a guy