Tbf, I sincerely hope a lot of you understand the basic concept of a gearbox. Depending on how far back you go, a water wheel might be a pretty massive leap forward, and it might at least inspire other, smarter people of the time to work on theories of energy, and eventually electricity.
I would just bring an e-reader preloaded with Wikipedia and a solar charger. It would be treated as a relic for millennia long after it stopped working and would probably cause a collapse in the time-space continuum, but that’s just how I roll. 😎
I’ve seen enough isekai anime to know the way to make money is to show people clear glass, soap and the thing to pull water from a well without a manual bucket.
If you can research how to make the original microscopes, bringing an understanding of virology would be hugely impactful.
Honestly, you don’t even have to go that far. Just bringing back germ theory would massively advance the health and safety of ancient peoples. You might get a little bit of pushback trying to explain it to them though.
Germ theory was around for a long time before it was adopted because no one believed it.
Hello, it’s me from 2025. When are you from where germ theory is finally believed and acted upon by the majority?
People don’t poop in their drinking water, it’s an improvement.
Not in the 2025 I’m from! https://www.cbsnews.com/news/supreme-court-epa-san-francisco-sewage-discharge/
I’m pretty sure that’s just precision grinding glass and setting it at the right distances.
But getting the precision shape to grind in can be hard. There was something about dripping liquid glass just right, but that may have been professional espionage to throw people off.
Viewing a virus with a microscope would be quite something.
Is the study of bacteria called something else? I guess just germ theory.
Viruses are extremely small compared to bactria. They typically can’t be resolved optically. The study of micro organisms would be microbiology if you want to be broad.
Good luck making gears though.
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You might think it’s a bunch of formulas like V = W / Q and V = I × R and all that junk
But no
Erase math from your mind for only a moment
Ionic Compounds molecules have charges, you have negatively charged anions and positively charged cations. This stuff exists everywhere: NH+, O-, Ag+, etc. Best way to identify them is to first set up a periodic table, probably pretty difficult for a layman to remember the rules, and then you can test to identify materials placement on the table with flame tests (different metals burn a different color when placed in a flame). Positive materials or the positive end of a polarized material are commonly referred to as Cathodes, and negatives are Anodes.
Magnetism is important, but you don’t need to know about the specifics of electron valence or orbitals to understand electricity. Magnets are naturally occurring and you can make most ferrous metals into magnets just by heating them to their curie point or by hitting or stroking them.
Once you have some copper, a magnet, and some positively (P) and negatively (N) charged materials you can set up some simple circuits. The materials can be oriented in large PN junctions to work as batteries, in small PN junctions to work as diodes which control the direction of flow of electricity, and in small PNP junctions with a glass plate at the end to create Light Emitting Diodes. Small capacitors can also be made with metallic conductive material sheets layered with non conductive dialectic components like glass or paper.
One of the earliest and most common battery formulas would be Lead Acid batteries. By layering Lead Dioxide as a Cathode and solid metal Lead as an Anode in an Electrolyte solution, ideally 1.25 to 1.28 kg of sulfur per liter of water makes a good battery acid. You can create sulfuric acid by burning naturally occurring sulfur and directing the resulting gasses into a container of water.
Once you have your rechargeable battery, you can charge it by spinning a magnet around inside of big coil of copper wire attached to the positive and negative end of your battery. The copper has its own electromagnetic field through which electron excitation is dispersed, and by moving the magnetic field of the copper with your magnet’s magnetic field you’re inducing flow through the copper in a specific direction.
I’m not going to get into the details of Alternating vs Direct currents, but I will add the concept of a Transformer which is where you place two conductive and charged materials in close proximity allowing it to Arc and jump over on its own, which would naturally convert AC to DC, useful in current cleaning and regulation.
Congratulations, you’ve just brought turbines, lights, batteries and electric engines to Rome. Now, kindly return to your present to promptly discover the horrible eternal empire you’ve created and suffer the rest of your meaningless peasant life.
I think my go-to invention would be some kind of bicycle or something that uses a similar mechanism
The truth is, you aren’t any smarter than people of the past, you just know different things.
What I DO know, is that there’s a dude in United States army camo in awe of this time traveler. So I am quite interested in what’s going on in the plot of this picture
That’s why I wrote this:
This is awesome, thanks for putting in the effort!
Quick edit: do I credit you as /u/klear or do you prefer another handle?
Don’t credit me. TAKE THE CREDIT.
No way in hell.
Good content deserves credit.
See my reply to The Picard Maneuver above if you must then.
So credit goes to Ryan North then.
Thanks for the info, I might even get the book \o
You made this? That’s awesome!
It’s been cycling through my PC’s wallpaper folder for years. I always seem to read something new when it pops up again.
I didn’t exactly make this, but I TOOK THE CREDIT.
Edit: I had a feeling Ryan North wrote this and just managed to confirm it. He apparently also published a whole book based on this concept, which will likely be a great read.
People are linking good guides to inventing the important stuff, but you should also know that you can download wikipedia. The text-only English snapshot as of 2025-03-01 was 25 GB, so fairly reasonable to include on a flash drive, laptop, or phone. Just make sure you charge your device before time travelling.
Creepy soldiers covered in blood worshiping Jesus background.
