So one of the (IMO rather silly) counterfactuals that comes up is the “what if a time travelling SEAL team fought a roman legion” or “what if a F-16 travelled back to WW2”? My take is it would change very little, some people would get shot, at most maybe a single battle could be turned. But then ammo and fuel would run out, and unless one of those people is really important or that battle really pivotal (which most are not,) then it doesn’t change the timeline all that much (except the story in chronicles of that time some dudes turned up and started popping caps)
But my random thought is what about the military equipment itself? How far back do you have to do before the Gulf in technology would render it useless people in that time, even as a guide to how advanced technology might work?
Assuming that, for whatever reason, the owners are not going to explain the centuries of science and technology that led to this F-16, AR-15, hang grenade,kevlar vest, etc. Also sticking to military equipment, and ignoring the medical equipment (and the instructions that go with it)
My though is anything much past the 20th century is pretty useless, WW1, WW2 they could “Terminator 2” that technology. US Civil War? Nahh. Except for vague ideas about how metallurgy, etc works it’s just junk to them.
I once asked a similar question (back in 2014 so don’t feel bad) and the answer seemed to be that your time-traveling Marines were boned once they got past the mid-late 1800s. Maybe further back for shotguns that could possibly be re-loaded with black powder based ammo provided you put the extra effort into cleaning and maintaining them.
I’m not a gun guy though so I’m sure others can pipe in here with more complete answers.
It’ll depend on the technology. The more mechanical stuff could be useful centuries back, even if they can’t properly duplicate it they’ll get all sorts of useful ideas by studying it. They can use the bits and pieces they can figure out to build their own devices. They couldn’t build an internal combustion engine in the 1400s, but they could look at the gearing and such and use that to build their own widgets of various sorts.
Electronics and such though, that’s another matter. I recall an old article from 1960s (I think) Analog magazine about a then-modern ramjet drone somehow ending up in the 1920s, and how it would be largely incomprehensible because they didn’t have either the theoretical knowledge or the instruments to understand what they are looking at. The examples that stuck in my mind where how without the theory behind them wave guides look just like empty spaces and a ramjet looks like a tube with a fuel line emptying into it.
It would be even worse with modern technology of course. Modern electronics operating at too high a frequency for their instruments to analyze, built on too small a scale for them to see them as anything other than chunks of silicon would be baffling to them. Much less for anyone pre-electricity.
What about just some books? A modern world atlas, basic textbooks on metallurgy, germ theory, medicine, world history, combat and siege tactics, the scientific method, chemistry, calculus, etc. could all give one side a significant advantage.
In terms of devices, what about some things that demonstrate relatively simple but still hard-won knowledge? A basic ground lens, maybe in a scope. A compass and sextant. A steam engine. A compound bow or repeating crossbow. A mortar. A film camera or maybe a simpler daguerrotype. A hot air balloon. A racing catamaran.
Or you could empower a small team to assassinate pretty much anyone with some suppressed rifles, night vision goggles, a GPS, and a few solar panels. Or a few handheld drones for recon or suicide missions.
It doesn’t have to be some incomprehensible nanoelectronics to still be the useful output of thousands of years of accumulated knowledge. What they could reverse engineer, they can learn from, not only making rough fascimilies using their contemporary manufacturing, but also leaping ahead by hundreds of years of R&D. Probably a good map alone would afford many ancient armies huge advantages.
Harry Turtledove made this point in one of his books, where aliens invade during WWII. At one point the British capture some of the aliens’ electronics. They have just enough technology to figure out what some of the chips are doing by treating them like black boxes, and sending in test voltages and currents. But as one person says, “Other than that, it just looks like a lump of silicon.” They couldn’t figure out the doping used to make semiconductor-based transistors and other circuits.
I suspect the key part of the OP’s premise that you’re missing is something they almost, but didn’t quite say. Which I interpret to be: “How far back can you take 2025-era military tech before it’s useless / incomprehensible to the folks back then.”
To which I think @Der_Trihs gave the best answer: It depends on the tech. IMO …
2025 bleeding edge microelectronics? Maybe 1970 but useless in 1960.
The transmission or differential from a military truck? 1900ish, but not 1800.
A simple lever-action rifle or pump-action shotgun? The 1300s, but not the 800s.
Those are my estimates of the dates the best scientists / engineers of the day could begin to learn something useful from whatever device. Not that they could replicate them in quantity. Nor that a then-current military could develop tactics to use them well even if a supply of them, and their spares, ammo, etc., could be magicked into existence.
Bringing technology into the past has a good chance of changing and advancing the technology of the past, even slightly, which could advance the technology and general knowledge of the present which means that there is a chance that time travel will come into being even sooner than it did before. Time travel comes into being perhaps fifty years before it would have before, they go back a hundred years from their past to advance technology and general knowledge instead a hundred years from our past, causing time travel to come into being perhaps a hundred years before our current time instead of just fifty years, rinse and repeat ad infinitum…and welcome to the nastiest feedback loop in history(s).
Actually, the fact that we even exist is pretty good evidence that time travel that effects the past is pretty much impossible.
Considering that the Earth and the rest of the Solar System are moving pretty fast (depending on the frame of reference you choose) through space a time traveler from the future would have to travel not only backwards, but also all the distance back we will be covering riding along on the surface of planet Earth until then. We should be pointing our best telescopes to the places Earth is going to be in the future. When something apparates there out of thin vacuum we will be able to calculate from the position of the apparition when time travel will be possible. I reckon the distance will be too great to see anything, no matter how big, the apparition will be further away than the Voyagers. We cannot even see individual celestial bodies in the Oort Cloud!
That is another way to say it, yes.
GPS does not work without satellites in the sky and atomic clocks on the ground; assuming those feels like cheating the premisses.
How much of Wikipedia could you download on a laptop? And how much gear (i.e.: electricity) do you need to keep a laptop running? How long could you expect a laptop to last anayway? Five, ten, twenty years?
The simplest of technologies can reveal secrets. Chemical combinations in forms not yet tried, aerodynamics not yet studied, even possibilities not yet considered (“That can actually be done? Thanks for the tip!”).
Even just an offline topo map app would be incredibly useful, with or without GPS.
And if it came with the ability to communicate with other nearby users, or you just included some walkie talkies, that’d also be a pretty big tactical advantage. Shortwave would be a strategic one.
All the text (25GB or so?) could easily fit on a laptop, or better yet a phone or tablet (no moving parts, lower power consumption). Images would probably be too big (4 TB for English?), unless you only loaded thumbnails. If you can pair it with a solar panel or several, probably the power / voltage conversion electronics would die before the phone or solar itself would.
But even a 90s style hardcopy of Brittanica would be invaluable.
That’s a whole different thing. I’m restricting this to just weapons of war: guns, grenades, warplanes, etc. No medical kits, laptops, instruction manuals or encyclopedias.
So I’m gonna change my estimate here, having thought about it. I recon it you give a modern assault rifle to a smart civil war era gunsmith, who’s familiar with Gattling Guns, they would work out a lot of how it works. They wouldn’t be able to reverse engineer exactly, as the engineering techniques are so far behind, but they could put a machine gun together with enough time and experimentation
ISTM the real point isn’t the tech. It’s the manufacturing capability behind the tech.
What prevented a lot of progress in firearms was the inability to manufacture dimensionally repeatable parts. Bringing a 1400’s gunsmith even 5 ordinary late 1800s Wild West era rifles would demonstrate that being able to swap parts between them was possible & beneficial.
Brain fart.