Suppose a group of people get transported back in time (say 2500 years). Then, in a manner reminiscent of A Connecticut Yankee in King Arthur's Court, they try to re-design modern technology. Assume that there's no shortage of labor or materials; the only real lack is knowledge.

What kind of group would have enough knowledge to recreate modern technology within 50 years? Would one average college-educated person be enough, or would it take hundreds of experts? Would there be any particular points that they would get stuck at?

For argument's sake, we can define modern technology as: laptop computers, kidney transplants, DNA sequencing, artificial satellites, and nuclear power plants.

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    $\begingroup$ Has someone been peeking at my Christmas list? $\endgroup$
    – IchabodE
    Commented Dec 18, 2014 at 22:20
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    $\begingroup$ I'd argue that the library of the Imperial College would be a major benefit to that lucky band you send back in time. $\endgroup$
    – Ghanima
    Commented Dec 18, 2014 at 22:43
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    $\begingroup$ Read 1632, by Eric Flint. baenebooks.com/p-379-1632.aspx $\endgroup$ Commented Dec 18, 2014 at 23:04
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    $\begingroup$ For a really quick feel for why this is hard, check out The Toaster Project: ted.com/talks/… It turns out that just building a simple toaster from scratch, even in the modern day, is shocking difficulty and expensive and produces a terrible mess. Indeed, in trying to make a toaster he at one point admits he had to cheat and get help for some of the even basic materials. It's a great example of one person trying to do this now - and makes it not hard to see how hard it would be to do in the past! $\endgroup$
    – BrianH
    Commented Dec 19, 2014 at 4:45
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    $\begingroup$ @BrianDHall - Even a simple bread slice for that toaster would be non trivial from scratch. $\endgroup$
    – mouviciel
    Commented Dec 19, 2014 at 8:27

21 Answers 21


Our intrepid time-travelers really have their work cut out for them!

To make this possible, let's hand wave the problem of language and religion, and say they got really lucky and wound up in a country that is eager to learn and listen. This is a big hand wave, but let's at least give them a shot to try before getting executed straight away or having to overcome a language barrier.

The big thing they will need to realize is that it will be simply impossible to jump straight from 500BC to 2000AD all in one straight step! Let's use the Wikipedia handy-handy List of Technologies to see what we can hope for in 500BC!

According to the History of Metallurgy, we can say that our locals have access to iron and have been using it for a while, and a it is pointed out that even steel has been discovered and used! However, until right around 500BC in China no one had a furnace that could actually melt steel, so no cast iron - but that's right when we arrived! Note that the first iron foundry in Europe as put at 1161 AD - 1600 years after China. That could cause us a problem if we land in Europe...

But let's hand wave this little geographic problem and pretend we have actual access to iron, charcoal, and a furnace hot enough to make limited amounts of cast iron and steel.

To further orient ourselves, consider that we have to hope to be in an area where petroleum is available to us for things like tar and asphalt, which is actually possible - hey, China did it! It sure seems easier to land in China in 500BC and get to work there, doesn't it?

Anyway, we've got clean running water, iron, a hot furnace, oil, copper, bronze...holy crap, we don't even have PAPER? We're about 1000 years before the first Persian windmills? Well, we've got papyrus and animal skins and clay tablets for writing, so I guess we'll make do.

Let's Make a Computer!

...right, so remember what I said about not trying to jump ahead? Obviously we are going to need some silicon to get any kind of recognizable computer made, and that stuff is just sand, right?

Well, not exactly. Remember that great iron melting furnace? Iron melts above 1500 Celsius, but to refine even metallurgy grade silicon we need to get over 1900. We now need to make a kiln hot enough to make glass, which the internetz say is way hotter than needed to make cast iron. Which is weird, because the internetz say cast iron was so hard to make because they couldn't get the furnace hot enough to melt iron, and yet they could melt glass? Hm. Hand wave, we build a furnace to melt glass!

Now we could get this far in a few months, with lots of labor help I'm sure. But now we have a problem. We can now make glass and even get ourselves some silicon, but it isn't pure enough to use in even friggin' basic electronics - much less computers! We supposedly need over 95% pure silicon for basic electronics, which was first done seemingly around the early to mid 1900s.

I honestly can't understand half the real technical material, so this college-educated single person with the internet at his hands would fail right here. I think we need to try crushing and putting through an acid bath, but where do we get such pure acids? That will take refinement, and a whole ton of chemistry, I honestly don't know how hard it is or how long it will take to get enough, pure enough, to get even remotely close to pure enough silicon.

And the thing is, that isn't nearly enough. We are going to need a handful of weird elements sourced and purified, from aluminum and boron to gallium. We need a clean room, air filtration, anti-static measures - these people don't have air filters! We will need electricity here, and how can we know without trial and error we got it right and have things pure enough? This is going to soak up a lot of time and specialist man power unless we have special instruments and ultra-precise tools to help us - and guess how much work that will take to build?

I'd say that with a team of specialists, all the worlds combined internet knowledge and the library of congress, we are at least a few years in and don't even have silicon of the proper grade. I don't know that with trial and error alone that it'd be doable, so we probably can't even progress here until we go backwards and invent some pre-requisites.

It's Not All Just Knowledge

Another problem we run into very soon is that it isn't all about knowledge itself, but arts, crafts, and skills. If you want useful chemistry and/or refinement, you're going to need thing like suitable lab equipment, such as test tubes and piping. Using crude metal scruples will contaminate the process and ruin it (or will fail spectacularly as with acids for advanced chemistry in metal or stone containers), as will crude methods of providing heat and flame unless you seal things properly.

When it comes down to it, glass-working and metallurgy are arts too - especially without functioning preprogrammed robots! You'll need skilled craftsmen to even begin to shape stuff resembling what you'll need for crude methods, and without automation or mass production they'll need trained assistants and heavy labor and months or years to handcraft the stuff we're going to need.

This Is Getting Toxic

What's worse, to start moving towards the first electronic devices we start facing some amazingly dangerous substances. Poisons, strong acids, aerosols, particulates, flammable/explosive gasses, toxins - without the right tools, pure hard work and persistence will kill everyone involved.

Safety measures will be needed. We're probably going to need some pretty good plastics to get out of this process alive, and...

We Are Going To Need A Bigger Boat

The thing is, our technology has pre-requisites - a history. It's easy for us not to think about it, but the things we have now are refinements and combinations of things that were invented before, which themselves are refinements and combinations of other things from before that, and on and on...all the way back to ancient history.

While we can certainly speed things up as development didn't take a straight line (and never will), it isn't the result of a few brilliant insights. It took many thousands of smart people, who learned methods from thousands of smart people who came before, who learned from thousands of smart people who came before, who together labored for effectively thousands of life times and drew together the work of hundreds of thousands of people across the last 2500 years just to get from "what's paper?" to "OK, Google".

There are lots of cool stuff we could have known about that others have pointed out (from soap and the importance of washing your hands and the importance of sanitation), but also is might be naive of us to think it's just because people didn't know they shouldn't throw corpses in with the drinking water; it was the result of a lot more than mere ignorance.

Lots of awesome improvements could be made, but fast-forwarding 2500 years in 50 years is going to take a herculean effort from many people, and they are definitely going to need more than the knowledge that they carry around in their head.

This is definitely something you can make an interesting story from, but the ultimate answer to the beginning question is: hundreds or thousands of experts, probably a lot more than 50 years, and they are going to need more than their own knowledge and memory - Wikipedia won't be enough, I assure you!

  • $\begingroup$ I added an extra section about handcrafting, art, and skills, as it occurred to me that just knowing how glass is made doesn't mean you're going to be making useful test tubes and beakers on your first try. $\endgroup$
    – BrianH
    Commented Dec 19, 2014 at 18:08
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    $\begingroup$ +1 For acknowledging the many iterations of "To get the raw materials for X, we need to develop Y". $\endgroup$
    – Myles
    Commented Dec 19, 2014 at 21:43
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    $\begingroup$ But experts can invent things, not only remember. And inventing things is easier when you already know what can be and what can't be. And scientific methodology is also important. $\endgroup$
    – Vi.
    Commented Dec 19, 2014 at 22:16
  • $\begingroup$ "95% silicon"; Would germanium be easier to refine? That's why it was used in the first transistors...of course, they already had more modern technology... $\endgroup$
    – Wick
    Commented Jun 10, 2016 at 0:52
  • $\begingroup$ I'd say it's pretty unclear that the entire population of this planet could recreate modern technology within 50 years even assuming we magically fiat that no one needs to eat or drink anymore. $\endgroup$ Commented Jul 19, 2016 at 21:27

New answer: Good luck!

So if you wanted to offer your creative scheme to bring Lolcatz to a more civilized age, you would probably need a plan to show the local king to suggest that your plan is feasible. There is an entire school of thought dedicated to how to make high level timelines like Gantt charts. Let's look at what it would take.

A key limiting factor here is manufacturing. While you can store all sorts of knowledge and work on designs in parallel, when it comes to building things you have to have enough capabilities to actually do the job. You don't get to make a mill or lathe that is square to 1/10000th of an inch straight off. You have to build several predecessors first, each more precise than the last. And building a computer is unforgiving... you won't get away with being less precise than that.

Another limiting factor is skilled labor. Free access to indentured servants is useful and all, but if you want someone to manage the temperature of a furnace by eye (because digital thermometers don't come until later), you're going to have to do it yourself with one of your precious future-people.

As a rough outline, I would divide my 50 years into epochs. Each epoch is responsible for a very wide class of tasks, because it takes a lot of infrastructure to get to where it is possible to build a computer. After that, you are free to staff-up those epochs.

Kickoff Epoch

Products: Iron casting, skilled surveyors (for future metalic needs)

Sorry to those who were hopeful. Just because we have labor doesn't mean we get to start swinging hammers. We need to take inventory of what is around. If your 2500y.a. metric is actually what you're looking for, that's just at the end of the "early" iron age. You're going to need quality iron, and fast. You will need to educate the local people as to what makes good or bad ores, and start explaining to them how amazing steel is going to be within their lifetime. You're also going to have to get them started searching for high grade trace metals like Vandium. They'll need the head start before other phases need such materials.

The machinist Epoch

Products: Steel machine tools

It's really hard to make reasonable machine tools with horrible base metals. Now that you've spent a few years working with the peasants to have some base materials on par with the base needs for Gingery's machine tools books, you're ready to start making machine tools. Just remember that the next few epochs are going to call for strange things like vacuum tight glass/metal seals that call for extraordinary precision. Expect to reinvent the entire set of machine tools (lathe, mill, drill press, etc.) several times during this epoch. Each time, you can use the precision of the previous set of tools to drive closer to the quality product needed for the next epoch.

The Power Epoch

Products: Electricity, generators, power tools

It's not really reasonable to approach the building of electrical generators without machine tools. The precision needed to have a shaft spin at 60Hz for any reasonable amount of time is very demanding. At the very least we're shooting for steam-era power sources. That's not a lot (compared to the needs of modern foundaries), but its at least something. Your computers are going nowhere without electricity. This step is not trivial. You are going to have to not only remember how power stations are built, but actually build one big enough to power your work in future epochs. There are a lot of processes which do not scale down well (such as every process required to build a computer), so this is going to have to be a reasonable sized power station. It doesn't have to be anywhere near a 500MW plant (a small modern plant), but if you're less than a MW, you'll be unhappy with the results.

This is the first time your exercising your new machine tools to do big things, so don't be surprised if you have to do things a few times to get it right.

The Purity Epoch

Products: Reasonable grade stainless steel, aluminum, glass, copper, etc.

Now that we have enough power to run a reasonable sized foundary without a brownout, it's time to let the Chemists have their day. Climbing towards computers requires quality. If you have low quality metals, your vacuum tubes will burn out too fast, and your computers wont be of any use. You need to give the chemists enough time to not only make reasonably pure aluminum, silicon, and copper, but to isolate the Nickel, Chromium, Vandium, and Molybdenum to make reasonable stainless steel. Consider that the upcoming foundry and fab work is some of the more demanding material requirements around, so low-grade stainless steel is not going to cut it. That's just the steel. I'm going to ignore the requirements needed to turn Bauxite into aluminum, and the oxygen-free copper needed for some of the vacuum processes we're going to see in the foundries.

The Computation Era

Products: COMPUTERS!

Finally! We get to make computers. But it's not so easy. The 486 has over a million transistors. You are NOT laying those by hand, so you're going to need to do this in generations. Minimizing the number of generations, you're going to want some vacuum tube based computers to bootstrap the extreme demands of monocrystaline-silicon manufacturing (without these 14+ inch wide crystals, integrated circuits just don't happen... and monocrystaline silicon is not an option without computer-grade temperature controls). Then you're going to need to make something along the lines of an Intel 4004 (the first "monolithic integrated chip CPU"). If you're gusty, you can skip a few million man hours worth of work and jump straight to a 486. With a 486, you're in a reasonable position to start talking about laying out the 1.7 BILLION transistors of a core2 duo. Of course, while doing this, we're assuming you'll go through at least 4 or 5 completely new fabs to transition from the 10um processes of the 1970s to the 20-30nm processes needed for a modern laptop.

I'm going to hand-wave away the software requirements like VHDL here. You'll need to have a software team keeping ahead of the hardware so that they have something to make the next generation of hardware with.

The Prodigal Son Era

Products: Software

I'm a software engineer by trade. I can tell you that it doesn't matter how much you think you know about a piece of software you want to copy - it takes time to produce it. Unfortunately, we have run into an interesting problem here due to the nature of the question. Life expectancy in mideval times was low, so I don't see people living very long past their 60's in 300BC. The real problem is medicine. Without hundreds of years of medical practice, people are going to die. If you're bringing "experts," rather than college students who know theory but not application, you're looking at people in their late 30s and early 40s. 50 years later, those people are 80 and 90... you're going to have lots of deaths due to diseases that are preventable in modern times, but well beyond the medicine we can scrounge together in 50 years.

The last few steps, building software to run on the laptop, are going to have to be done by pesants who were taught how to program software, not crack-shot developers in their senile years. Likely we would have to take children out of their family, and raise them to do nothing but produce code.

So what does it all mean?

We have 6 phases:

  • Kickoff Era
  • Machinist Era
  • Power Era
  • Purity Era
  • Computation Era
  • Prodigal Son/Software Era

We can't really do these in parallel. Each phase is really quite annoyingly dependent on the previous era's final product. It'd be wonderful to try to blend the kickoff and the machinist eras, but honestly it's not a reasonable estimate. There will be a blend, but my estimates are also hyper conservative because *I have included very little discovery time in my schedule, which is always a sign that the schedule is hopelessly optimistic.

Given this, we need to allocate 50 years between 6 eras. I am uncomfortable giving anything less than 10 years to the Software Era. It's going to have to be done by a bunch of pesants who have never programmed in their life until now. I consider 10 years an eggregously aggressive schedule. Realistically I'd like 100-200 years to develop enough of a knowledge base in the pesants to do this task, but we're going to allocate 10 years.

The Computation Era cannot be rushed as well. You are going to have no not only develop 4-6 unrelated computer architectures in order to realistically accomplish the goal, but you're going to have to debug each and every one before using it to move on to the next. I choose to give it 2 shares worth of time, compared to the other epochs getting 1

So the final schedule is (with a few handwaved allocations):

  • Kickoff Era - 3 years
  • Machinist Era - 6 years
  • Power Era - 8 years
  • Purity Era - 9 years
  • Computation Era - 14 years
  • Prodigal Son/Software Era - 10 years

What did I just suggest?

  • We are going to have to go from wood fired brick stoves to steam-powered 60Hz generators in 8 years
  • We are going to have to go from "the best iron we can find in this era" to "the abiltiy to fabricate 100lb+ single crystals of silicon" in 9 years.
  • Somehow we will need to average somewhere between 2 and 3.5 years to completely develop, test, and integrate an entire computing architecture (which had thousands of engineers to develop in the first place). We will need to average that over 4-6 architectures
  • We will need to manage to teach an entire generation of pesants how to program for computers that do not exist yet until they are 20-30 years old. This class of pesants will have 10 years to reproduce Linux, Office, and maybe even a Web Browser.

Realism check?

The time-frames needed to meet the 50 year deadline are hopelessly extreme. The only way to get around this is to stack the deck. If you bring a glut of individuals over, each of which is carefully assigned their portion of the task, you stand a chance of succeeding. The only way you can succeed is if you manage to do epochs in parallel. The only way to do this is to remember how to build everything in such detail that it can be built as fast as materials are available, and without a single mistake. The only way to do that is to treat humans as over-priced books, and fill their heads with the fine details of "Foundary Design: Volume MXVI."

Original Answer

This is my original answer. It is rather pessimistic because I actually tried to answer the original question of "N people in 50 years" instead of the modified question "how would you lay out the tasks?" In light of the time-frames above, I think you can see why I consider such high personel-counts reasonable.

You could do okay if you transported the entire population of the Earth, along with all of our books and computers.

While a reasonable sized group could remember a lot of the really difficult leaps (Electricity comes to mind), vast swaths of what you look to do is simply out of the scope of such a small crowd.

One of the challenges you will face is the need to do things right the first time, or a very small number of times. Not all technologies can be made in paralell, so your 50yr budget is going to have to get sliced up into little pieces to deal with such ordering.

Let's take your laptop example.

  • I need a CPU, north bridge, south bridge, graphics card, hard drive controller, and memory. Each of these has to be coded in VHDL. Modern hardware is not simple. There are a lot of really difficult details to remember. There's a good reason intel hires so many of the best designers each year. I'd estimate 300 PhDs would be enough to remember all of the fine details. A team of 2000-3000 engineers working round the clock should be able to redesign a Core2Duo in 10 years or so (hopefully they'll remember enough details, because they lack the libraries of information the original teams had). Unfortunately, Engineering like that isn't exactly a skill you can just teach your average commoner, so you'll have to bring all of your engineers yourself.
  • Of course they'll make mistakes in the VHDL code, so we need a simulation to test on, which means you need a computer. Oh wait, you're building one. Okay, so we need to build a simpler computer. Unfortunately, we don't get to re-use the engineers before... their brains are full of a decade's worth of innovation. We need a few engineers and PhDs to remember how it was done old-school, before we had all that extra processing power. An additional 100PhDs and 1000 engineers should be able to boot strap you.
  • Unfortunately, even this computer is going to need a computer to operate on. We probably need some vacuum tube logic to bootstrap that. Vacuum tubes are tempremental beasts with all sorts of hard-to-explain behaviors. I'd say 50PhDs to remember the details of how to make them work well, 50 technicians/glassblowers to remember all the details of how to manufacture them.
  • We'll do a gimmie on the wires, since that's part of the mining block of tasks (probably 40-50k people's worth of information, but it's distributed across all of the things you need to build with the fancy minerals).
  • Wait, what's VHDL again? We don't have specs, so we're going to have to recall what VHDL is from memory. It took hundreds of people to get it right the first time. We might get away with 30 really sharp VHDL people to write the spec down again.
  • But VHDL has to be processed. We need C/C++ to write a decent VHDL simulator or printer. I think 70PhDs and 200 coders should be enough to remember all of the fine reasons WHY each C/C++ behavior existed and code them all up over 10 years or so. Remember, this has to be bootstrapped, so they're goign to write it 4 or 5 times. Fortunately, this can be done in paralell with the hardware team!

You now see that I have a small city forming. I haven't even begun to design a screen, or fill it with software. And, in my opinion, I am highly conservative in these numbers.

I'd say my original estimate might be high. If you had 50 years to reproduce a reasonable set of technology, you might make do by taking the top 10 or 20 million smartest individuals. You'd have to pick them carefully, because some of those people are going to die within 50 years, so you need overlap.

I'm also removing nuclear power from the reasonable list. Because of how long it would take to identify nuclear fuel, and how hard it is to build nuclear power plants while you are building computers, I'd say 50 million individuals carrying carefully worded instructions from today's modern NRC workers could remember enough details to build a reactor cold-turkey in time for your deadline. It can't be done by bringing just the smart people, because the smart people had computers to work with; this has to be done from sheer memory.

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    $\begingroup$ +1 for a good specialised answer. However, one problem can be seen when referring to what-if.xkcd.com/8. Transporting the entire population (or even tens of millions) would probably result in a similar scenario due to the inability of a Dark Ages civilisation in supporting such a large population. $\endgroup$
    – March Ho
    Commented Dec 19, 2014 at 7:26
  • $\begingroup$ I have to say these numbers seem heavily overblown to me. Trying to exactly replicate an existing design is a wildly impractical and pointless proposition, and if any functional computer will do, well, you really don't need VHDL. Fairly complex computers can be designed on paper (after all, we did exactly that in class), and you can build up from there; the sticking point will be the switching elements (ie. transistors in modern computers), everything else can be (eventually) arrived at by some half dozen engineers. $\endgroup$
    – Mike L.
    Commented Dec 19, 2014 at 15:08
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    $\begingroup$ It would be nice if it were that easy, but the devil is in the details. The OP specified laptop computers, not computing in general, so that suggests he is looking for at least 2000's era technology, not 1940's computers. We have two paths: 1 is to try to replicate an existing design, such as I did. The other is to try to design an equivalent system. If you design an equivalent system, you need time to beat the bugs out, and the OP is only offering 50 years. It is possible that my 20 million estimate is high, but half a dozen is an unbearably low underestimate. $\endgroup$
    – Cort Ammon
    Commented Dec 19, 2014 at 16:09
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    $\begingroup$ Consider: try to find "some half dozen" engineers who are so unbelievably smart, that they can replicate their entire field's work over 70 years in less than 50 years, without any existing infrastructure, and yet are humble enough to be content merely working in that field instead of leading it. $\endgroup$
    – Cort Ammon
    Commented Dec 19, 2014 at 16:13
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    $\begingroup$ Your "Entire Earth population" would starve to death and devolve into warlordism and cannibalism within a month, if thrown into the past w/ nothing but books and PCs. Now with some tractors, silos and ships, perhaps... $\endgroup$ Commented Dec 19, 2014 at 18:41

No one can do it. Even if they all knew EVERYTHING about our modern technology, were perfectly orginized, and had the resources of a kingdom backing them up it couldn't be done in 50 years.

The problem is that of building tools. I can't just build a computer with the help of a blacksmith. I need very exact tools to fit 10^8 circuits per square centimeter of chip. To build automated tools that exact I would need, in turn, other special tools, which I would need specialized tools to build etc etc. Even doing everything perfectly it's just not possible to go from middle age tools to computer age tools in 50 years, it takes too long to build all the intermediate, slightly more resigned, tools in succession.

There is also, as already pointed, we are a very specialized society. No one person knows everything, or anything remotely close to everything, about technology. Even if you sent all of NASA, YALE and Harvard, and MENSA back in time you would still be loosing the vast majority of our knowledge.

EDIT: as BrianDHall said kidney transplants are not quite as doable as I thought. However, many other surgeries would be plausible, though less effective, If a surgeon trained in the older surgery techniques were sent back. Surgery is more about knowing the body and how it works, it is less dependent on specialized tools (relatively speaking!!). The biggest issue would be lack of proper anesthesia, limited ability for sanitation (basic boiled water can be used, but it's not the same as a proper sterile operation enviroment), and lack of drugs to control infection and/or body immune response(though as I said a basic antibiotic could theoretically be created in a few years, penicillin was just moldy bread after all!) . This means a lower success rate of surgeries, but if it was life or death then a surgery with risk of infection is still better then death! Which surgeries are possible and which aren't really comes down to rather they needed specialized drugs pre or post operation, and how hard it is to operate on a patient that is not under anesthesia (ie that could move while your doing a percise cut) I would assume. I admit I'm less knowledgeable in this area.

Some cool things that could be theoretically done by a lone person with any STEM education, intellect, some support from the 'natives', and perhaps an interest in science (but no very unique or specialized skills beyond high school) are:

1) curing lots of diseases. Penicillin is just mold on bread. Smallpox can be cured by having everyone make good friends with cows and their polka-doted milk maids. MANY diseases could be cured by teaching people sanitation and to not defecate into their drinking water. Others can be survived by getting rid of rats and misquto infestations. If someone recognized a particular disease they could help to cure it. The idea of a vaccination may be possible to generalize to any virus (give me my high school knowledge, 5 years, and a kingdom's support and I could try a few tricks to make vaccines that might actually be partially effective, though I feel sorry for my first test subjects). All of these would take trial and error, not a do-right-first-time thing, but could possible be done. For that matter basic sanitation like having people who are doing surgery or delivery babies wash their hands first could save a massive number of lives!

2) teach scientific method and advanced math. None of these change life directly, but the concepts are what make the Renaissance and industrial revolution possible. You can rapidly accelerate human development with these concepts

3) teach high school science. Really, Newtons first book on Newtonian physics came out right after the middle ages had officially ended (just barely), so they don't know physics yet! Calculus was discovered a century after that! Germ theory was figured out sometime between the two.

4) Teach evolution. This is one science that is very easy to explain, it's not based off of any complex math and could be understood by anyone who has an open mind without much other scientific basis. Of course managing to reveal it in a way that doesn't make you the enemy of religious orthodoxy is another issue, remember the catholic church was VERY powerful for much of the middle ages and was not afraid to excommunicate or worse those that they didn't like

5) Get people to believe you are from the future just with the clothes off your back (and phone in your pocket). Imagine what a watch would do. Imagine what a scientific calculator or laptop would do!! Sure they would run out of power eventually, but you would have convinced everyone who you are by then and used them for good effect.

6) helped design gunpowder and the gun. It's entirely possible someone would remember most of the gunpowder's ingredients. You won't know fully how to build a gun or even gun powder, but the principles and ingredients given over to well-funded experimenters of the day could perhaps make a gun happen?

7) cure scurvy. Scurvy is interesting, the 'secret' to curing it was discovered and forgotten many times. Since we didn't know what it was about fruit that cured scurvy experiments with using cheaper fruits (that didn't have vitamin C), or cooking or filtering our storing it in such a way that the vitamin C was lost occurred many times in an effort to cut costs

8) 'discover' the New World. That one isn't even hard to do. "hey king guy, I'm the dude that can make people move and talk on a magic screen by pressing button and just cured a deadly disease. I tell you that if you send 3 ships in that direction with lots of food they will find something awesome."

9) correct stupid misconceptions like blood letting that were getting people killed and maimed for no reason.

10) tell the 'future' by remembering your history. Though keep in mind that the more one does this the more they change history to make this not work. Plus we all tend to be taught rather inaccurate history in high school, someone trying this may find out that real-life wasn't quite like the bastardized euro-centric version we were taught if they aren't careful.

  • $\begingroup$ I think I did answer the question. My answer is that No group could recreate modern technology in the timeframe he specified. I pointed out the only tech he mentioned which I feel could be done in the timeframe specified. $\endgroup$
    – dsollen
    Commented Dec 18, 2014 at 23:52
  • $\begingroup$ At the risk of seeming to be biased because I realize you thought my answer was so poor, I think that this doesn't answer the question. None of these things were what the OP asked about; the new World is irrelevant here. I'm not going to downvote this because perhaps that would be partly spiteful, but I hope my point gets across. "it takes too long to build all the intermediate, slightly more resigned, tools in succession." - not with enough materials and labor, as the question says. This shortens the timeframe immensely. Apologies for the re-post; I wanted to add in a sentence. $\endgroup$
    – HDE 226868
    Commented Dec 18, 2014 at 23:52
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    $\begingroup$ Re evolution, I do not know of any reason the Catholic Church would have cared... the only reason people have issues with evolution is because it contradicts the particular way they interpret the Bible, but that way didn't really go mainstream until reformation. As long as you didn't question Gods position as the Creator, I doubt people would have considered the details of biology to be religious issue. $\endgroup$ Commented Dec 18, 2014 at 23:58
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    $\begingroup$ There's also the fact that the OP said 2500 years back in time, which puts you before any kind of Christianity, let alone the medieval Catholic Church. Also, Newton described both (what is now known as) classical mechanics and calculus in Principia Mathematica. They weren't a century apart. $\endgroup$
    – KSmarts
    Commented Dec 19, 2014 at 15:16
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    $\begingroup$ I especially like how you tried to find things that would be possible, so +1! But a note on kidney transplants specifically: it would be impossible as you outline it. See Stanford history: web.stanford.edu/dept/HPS/transplant/html/history.html At the least you need cortisone treatments, and that's a very advanced chemical refinement from bile or an extremely rare and dangerous chemical. Unless you count identical twins, organ rejection and death result without immunosuppressant medication and match testing - even with a modern surgical team and other equipment. $\endgroup$
    – BrianH
    Commented Dec 19, 2014 at 15:31

In Eric Flint's 1632, a town of about 30,000 from West Virginia gets transported back in time (you guessed it, to 1632) in Central Germany. They retain the physical infrastructure of the town. I won't spoil the book further than to say that, absent the library of Congress or somesuch, the best they can aspire to is a low 1800 technology within a decade or so, with the cooperation of the locals.

Modern technology is so distributed and interconnected, that even a pencil requires materials from half a dozen countries to build. They would simply not have the infrastructure base to maintain, never mind develop 20th or 21st century tech for generations, even with perfect libraries.


Let me start with a quick 'no' to the average college-educated person possibility. I'd like to think of myself as above average, and I'm continually learning post-graduation. One of the gauges I use to decide what to learn next is the question, "How much of the modern world could I recreate if I found myself in the dark ages?" I could only do two of these and help out a bit with a third.

Okay, 2500 years ago, so for the best labor and access to materials, we're talking about Greek, Roman, Babylonian, Egyptian or Chinese. It would be awesome if at least one of your team was fluent with the ancient form of one of their dialects. That's pretty specific. You'd also need someone to convince the locals to do all this work for you and that you are not, in fact, demonic in nature.

So you have metallurgy and basic mining, architectural, smithing and very primitive loom work. You will need to upgrade that, and pretty much any college student could quickly get them up to Dark Ages level. Anyone in the sciences could probably start them working with electricity, but it does take specialized knowledge of how to extrude metal into wire.

You need someone who could figure out where to start drilling for fossil fuels to make plastics from, and a chem major to take the raw ingredient and get a finished product from it.

You wouldn't need a biology major to do the DNA sequencing, but you would need someone who knew how to build a centrifuge (fairly simple) and a mass spectrometer (extremely complicated) and a lot of steps in between.

The same person could probably build a Geiger counter to find fissionable material to power you reactor, and could certainly build a satellite (getting it into orbit is a separate issue). Probably a radio for communicating with it.

This is getting long, so I'm going to stop trying to figure out how many people it would take, and tell you how many specialized disciplines you are talking about.

Linguistics and sociology, electrical engineering, computer programming, chemistry (with knowledge of refining metals, making plastics, ceramics and glass and rocket propellant), surgery, lens grinding, tool machining, familiarity with the parts involved.

Let me point out that the same guy with the specialized knowledge to coat your wiring in the right mix of distilled fossil fuels is probably not the same guy who is comfortable working with liquid fuel mixtures. Also, the guy who could machine the parts for your mass spectrometer probably doesn't know his way around a containment chamber for your power plant.


If you look at history, you'll see that technology grows in leaps, not steadily. Some of that comes from new knowledge, but quite a bit is tied to the tools used to create more technology. The huge rush of new technology in the last hundred years wouldn't have been possible without reliable vehicles and roads, air travel, and computers.

To build even one of those things - say, a computer - you'll have to start at raw materials. 2500 years ago, the best tool available was barely at "pliers" technology, which means that every tool you'll need - including more tools to build those tools - will need to be designed from the ground up.

First, the raw materials need to be gathered. Since some of the materials for circuit design are very, very rare, or only come from certain parts of the world, you'll need someone who is a top-level mining expert, who has worked both in the field and in the office. That's at least one person.

The raw materials will be bound to rock or other minerals, so you need to know how to extract the materials from the dirt you dug them up with. To do that, your best bet would be a chemical engineer, with broad knowledge of how to obtain, create, and manage the chemicals required to extract or create the metals and other materials you'll need. Very few chemical engineers are also mining experts, so that makes two people. In fact, you'll probably need a scientist and an engineer, so three people thus far.

Now that you have your materials - and they will most likely be very low quality - you need to actually build the circuits of... your machinery. Circuit boards of today can't be built by hand, and for the first iteration of tools will have to be built that way. So, you'll need an engineer to build the production machines. You should be able to find someone with a broad knowledge of mechanical and electrical design to build a power station, the machines, and warehouses to hold it all; but, such a person probably isn't cross-skilled in chemistry or mining, so that's a fourth person.

After several iterations of machinery to build more precise machines and tools, you should have the materials available to build some simple electronics. At this point, you'll also need a master of circuit design, with deep knowledge of computers, circuitry, and everything that goes with it. The electrical engineer could help to design some of the circuits, but really, you'll need an expert for this, too. That makes five people, thus far.

Given those four experts, you should be able to build a working prototype within 50 years - possibly less time, but I expect the mining and refining to take a decade at least. Some materials may take even longer to find or refine. However, they will need a lot of help from the local population - while the mining expert is digging for ore, the rest of the experts should be training students of all ages to replace them and to assist them. For safety's sake, I would bring two or three times that number of people; you never know who will die from illness, injury, or old age.

Of course, that's only the computer. The other technologies need similar hard-to-manufacture tools, and more experts that wouldn't have similar skills:

  • A kidney transplant would need at least four people (surgeon, nurse, sanitizing expert, and a chemist for basic medication), and many more if you intend to teach others how.
  • The artificial satellite is actually not that difficult; one person with knowledge of physics and another with knowledge of how to find or create fuel would be all you need. Refining the metal required isn't that hard, and one or both would know how to create it.
  • DNA sequencing, however, would need working computers from the first group, along with more chemical engineers, scientists, and biologists. We are only barely able to sequence DNA today, which means it will be very difficult to manage with rudimentary tools.
  • Nuclear power plants would also be difficult... at least, as long as you want to be safe. Without computer-driven safety controls, nuclear power is not all that difficult. Just slap a couple pieces of uranium together underwater, and bam! Instant steam power! The locals you'd need to run the controls wouldn't last long, but nuclear power could be available with no more than a nuclear engineer and a physicist. It would take a little while to find some uranium, but once found, a functioning nuclear power plant could be created in a few months. Which is a good thing, because that's about how long your workers would live. It would be a lot safer in the long run to start with coal power, and work up from there.

The biggest problems with creating modern technology from scratch will always be materials. You may have the knowledge to build a computer, but even two hundred years ago, the materials you'd need to even make a simple diode wouldn't be available, let alone complex circuitry. The second biggest problem would be tools; the tools we use now are at least four iterations past hand tools. You'd need to hand-build one machine, which would be used to create another, more precise machine, which would be used to create yet another, even more precise machine, and then you would finally be able to reliably create a single tool we use today. Multiply that by the hundreds of tools needed to build a computer, or operate on a person, and you already have years of construction and design, regardless of the number of people you have.


The first thing to notice, is that you cannot do it the capitalist way in 50 years. No way*. Empirically, looking at our world's history, I see only one other social organisation which is amazingly effective in precisely this task: bringing the semi-feudal, agrarian-type society to produce their own computers and nuclear power in 50 years. Forget college-educated, you need very specific skills. About 1% of your group needs to be a staff of dedicated people with "cool heads, hot hearts and clean hands", if you know what I mean. It won't look nice, it won't look scientific, there would be prisons, there would be tortures, there would be purges, both inside and outside, the heads are going to roll. Next you need a larger force (~10%) of trained and obedient police, and they need to be good at martial arts to exert their power on the main group, because they wouldn't have anything else initially. About 30% should be farmers trained in the archaic farming techniques.

Without these basic prerequisites, your group would soon get some centrifugal force and wouldn't remain a monolith. All your cherished nuclear physicists might just wake up one day in the year 3 and decide they're fed up, they don't want the humanity to get to the proper version of future and they would walk the land, just like that, to become a successful hunters-gatherers somewhere in the central European plain. Historically, such problems were a major pain in the 1600s in North America, where Indians openly despised the powerful Western civilization, but there was quite a substantial number of whites who run away to voluntarily join Indian tribes. Situation can quickly get dramatic with your farmers, as they see more than a half of their food taken away from them and (initially) get nothing in return except of diseases and early-spring hunger. Constant terror is the only way to get this kind of taxation.

Speaking of diseases, you would probably bring some modern mutations of viruses and bacteria to exchange with the ancients. While your people would be possibly in better situation (or maybe just slightly better), you would most likely do the same thing to the ancient cities that was done to American cities: you would kill 90-95% of inhabitants before you could even see them.

[*] Basic pre-requisite of capitalism is a large consumer market. By consumer market I mean >1 million of greedy people, the kind that would buy a shirt just to display their status despite they already have two other proper shirts.

In 500 BCE you wouldn't have these people available, and it would take more than 50 years to "convert" the existing population to the consumer way.

And computers are not made of silicon and science and need. Computers are made of silicon and consumer market, period. We've got silicon for billions of years on this planet, we've got the need from the very beginning, we've got science for thousands of years. But just as we developed consumer market, it took only about 300 years of clean sequential progress to have computers. Science is just a side effect.


It may not be possible to create the laptops of today in 50 years - the entire population of Earth 51 years ago, with all the infrastructure and knowledge in place, couldn't do it in 50 years.

However, a small number of people from today can in 50 years kick off a technological revolution that will lead to an advancement of the level we have today in the shortest amount of time that is practically possible.

There were a number of ideas throughout history that had a huge impact on the advancement of technology and are very simple to explain and obvious in retrospect, but no one thought of them before. Some examples:

The Printing Press: Very simple to explain to a society that is already using stamps for wax or coins and using ink for writing. Getting them to set up printing presses will mean that information can start to spread more quickly and the knowledge from the future can be preserved and distributed widely for when the infrastructure will be ready to implement them.

The Steam Engine: Very simple to explain the basic process to people who are already using fire and know how to boil water. They can then build railroads and other machinery required to produce and transport materials for other technologies.

The Scientific Method: No science is required to explain it, but the world was stuck with the Aristotelian method for a long time. Explaining it to people 2000 years ago and showing them that science works would immediately advance them 1000 years. They can then proceed with their own advancement, boosted by having had a peak at the future.

Math: Practically all the math knowledge that this group of people will have can be taught to smart people in the past, even though it took a very long time to develop in the forward direction. Even something as simple as our number system can have a huge impact.

There are many others and there's also a number of other non-scientific advancements that we've made throughout history, such as democracy and equality, that have an impact on the advancement of science

  • $\begingroup$ Yes, in 50 years it would be unlikely that they would have modern electronics. But I suspect they would have electricity, telephone and telegraph, and possibly radio. These coupled with the printing press, engines, and even today's grade school math will propel people forward in technological advances that would produce computing technologies soon - just not in 50 years. $\endgroup$
    – Adam Davis
    Commented Dec 19, 2014 at 14:23
  • $\begingroup$ It's interesting to note that the earliest steam engines that were used to do real work used low-pressure steam (partial vacuum). Power was limited by the ability to condense steam into water. High-pressure engines which vented steam rather than condensing it could get a lot more power from a given weight of equipment (useful on a locomotive or a tractor) but getting any meaningful efficiency requires using pressures which are high enough that any imperfections in the metal work can spell disaster. $\endgroup$
    – supercat
    Commented May 14, 2015 at 17:19

It won't work if there is no market for it. A modern laptop computer can only be made because billions of processors are produced. You require an industry to make the tools to make computers, and you need another industry to produce the tools to make the tools for it, and so on.

You could, however, create a late 19th/early 20th century technological base pretty quickly, in at most a few years. From then on, you would need to create a pretty globalized society to create the necessary markets, otherwise no single kingdom could achieve it. To make an early vacuum-tube computer with all the resources of a medieval kingdom? Maybe achievable. Modern consumer electronics? Not a chance without a large enough market for it.

A lot of technology wasn't invented sooner, not because the idea didn't come to anyone, but because they didn't have the tools for it. All the mathematics necessary for a moon mission could be calculated in the 19th century, possibly sooner, they just didn't have the industry to produce the tools to build rockets large and efficient enough.

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    $\begingroup$ I'd say the "market" is the least of your worries, especially since the question said not to worry about labor or materials. I think you are entirely wrong about being able to advance 2400 years in "at most a few years" and you don't say how. Why exactly do you think the globe and the market are important? They might have had the math to figure out how to theoretically hit the moon with an imaginary cannon in the 19th Century, but what about the computers and electronics and vacuum seals and radios and radar and so many other things? $\endgroup$
    – Dronz
    Commented Dec 21, 2014 at 6:53

I'm gonna say it wouldn't happen, at least on the computational level. While a doctor, jeweler (for making the scalpel, needle, etc), geochemist (for mining and refining the materials needed by the jeweler), microbiologist (for penicillin to fight infections) and textile factory worker (Where do you think you get the threads for stitches?) may be able to get together to make a Kidney transplant happen, computers would be way more complicated. Every CS college grad at least in some way understand Turing machines and bit-wise operations, but the entire computer science industry is standing on the shoulders of giants. If you got the right group of highly advanced specialists (Manufacturing, hyper-mathematics, programmers, system designers), it could be done, but if you just took an average sampling of people, I'd be highly incredulous if you said you got the right people to build a computer.

  • $\begingroup$ " Every college grad at least in some way understand Turing machines and bit-wise operations" - Maybe on StackOverflow - to give an example - but not in many other situations. $\endgroup$
    – HDE 226868
    Commented Dec 18, 2014 at 22:31
  • $\begingroup$ Ah, sorry, I missed the "Every CS college grad" part. I on the other hand, did not get a writing degree. Fix'd. =P $\endgroup$
    – Sidney
    Commented Dec 18, 2014 at 22:32
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    $\begingroup$ If every CS grad knew turring machines we wouldn't be flunking half of our applicants with FizzBuzz questions :) On a more serious note I think that this is not an issue limited to computers, the same specialization of fields occurs all over the place, no one 'expert' in a field actually knows more then a tiny tiny fraction of that skill. We specialize because humans can't learn all that we have to know in a field in a lifetime, or come remotely close. $\endgroup$
    – dsollen
    Commented Dec 18, 2014 at 23:02

So you want an uplift package

Well, there's a lot of work that needs to be done. Now, technological development is not a straight line; there's a lot of things you can forgo and bypass, if you have specific goals, but let's just say we want some of our modern conveniences and see how far we can get.

TL;DR: you can get most of what you wanted, after a fashion, but not on today's level in 50 years.

Let's start out by listing who we need. I have the good fortune to be teaching (and researching) at a technical university, so I'm going to base my estimates on the type of requirements we have for our graduates.

Here we have to stop for a minute and examine our basic assumptions; the first question is whether you get to pick who exactly you get to take back. If so, we can reduce the manpower requirements immensely, if not, you need to take enough people that you will get the required expertise by random chance. I'm going to do an ass-pull and estimate that about 1% of the population have the required skill on a required level, so if you're sampling randomly, multiply the numbers by 100. On the other hand, the extra people with modern education would also help, as you could send them off to do some less complicated tasks.

Let's also assume that the entire population of the area is at your beck and call and will provide their work and whatever expertise they have per your instructions.

I'm further going to assume that the area you're in is something like Europe, since that's where I'm from and it will make things easier on me to have a geographical point of reference.

That said, here's a list of people you're going to need:

1. Metallurgists

To get pretty much anything done or built, you're going to need steel. Tooling steel for things that make things, stainless steel for industrial chemistry and the like. Right now, we're in the bronze age, so people from the more advanced localities (eg. Greek city states) know something about smelting and alloys; your guys will need to teach them to make steel.

Fortunately, iron ore is abundant and coal is not too hard to come by either. Unfortunately, to get good steel you'll need to get picky about the ore and the additives you use. Bottom line, you'll quickly be able to produce some steel, and later you'll use that to make yourself the tools to make better steel, repeat ad nauseam.

This iterative principle is something you'll be seeing a lot of. Using modern knowledge, we can get the development started and get it running pretty well, but the later steps will get progressively more difficult. Whether 50 years is enough time to get to 21st century levels is anyone's guess; I'd say that in this case, and probably most of the others, you can get to 19th/20th century levels before the process slows to a crawl.

2. Civil engineers

This bunch you'll need to make useful things out of the steel you now have. Mostly tools, then fabrication machines, engines to drive the factories you'll need (powered first by water and wind, later by steam as you can machine pistons) and ultimately the tools to make our desired goodies.

They will also be building things; as a side effect of this enterprise, you'll probably be building a transportation network, so there will be roads, ships and barges, wagons, and such. A logistics expert would help here, but you could also just brute-force this.

When your builders aren't busy, you can have them build aqueducts and sewer systems. You'll probably end up building cities around your eventual factories and it would be a good idea to get them some basic sanitation; cholera epidemics can really set you back.

These guys will also be of use when you're digging mines to get further raw materials, and on their downtime they can be designing the thousands of tiny conveniences that will make your life a little more bearable.

The nice thing about civil engineering is that if you have underlings who can follow instructions, a single engineer can get a pretty big project done. After all, that's how it was up until the late 19th century, when we finally ran out of the big projects and more specialisation was required from that point on.

3. (Bio)chemists

These you will really need to get anything done. Most material science is based on chemistry, so you'll want industrial chemists to design the processes that fabricate your silicon, fuels and whatnot. A petrochemist will be required and a geologists wouldn't go amiss for prospecting.

Some of your chemists should also be pharmacists; an unmedicated black plague can really put a damper on things and you want to get your hands on - at least - some antibiotics and vaccinations soonest. Yes, penicillin is just bread mold, but it's pretty much impossible to tell which bread mold it is without testing (otherwise you could just as easily poison your patient) and you want to be able to produce it in quantity.

Of course, most of this work will require stainless steel vats to produce anything usable in quantity, which is why I listed metallurgists and civil engineers first.

Another important thing that you can get your chemists to do are artificial fertilizers. If you have some guano at hand, you can start from that, otherwise you'll need to first implement the Haber-Bosch process. If you do this, however, you'll also have your first ingredient for high explosives, which will come in handy later.

4. Agriculture experts

Now, farming does not directly contribute to your goal, but it is necessary to keep your working population well fed. Increasing yields by improving your crop breeds and judicious use of fertilizer and pesticides (as soon as you can get them) can make sure a famine will not wipe you out.

Furthermore, before the Industrial revolution, a significant fraction of the population (80% probably isn't far off) had to work in agriculture just to support what population level there was; improving yields not only staves off famine, but frees up a significant workforce that you can employ elsewhere.

5. Electric engineers

Eventually, you'll have to introduce electricity (if you really want to run those computers, that is). These people will be there to build some power plants for you, design and run the power grid a build engines (or, for instance, furnaces) that run on that sweet electricity you now have and can be used in your factories and elsewhere. Electric engineers can also help you with telecommunications, which can help increase your industrial output by improving coordination.

Of course, for most electric machines, you're going to need at least some copper for conductors and rubber for isolation (this can be replaced by layered silk or in some cases resin, but you want rubber for best effect), which your metallurgists and chemists need to take care of first. With these, you should be able to churn out some late 19th century engines and appliances pretty quickly.

6. Computer engineers and mathematicians

I am lumping these into a single category because there will be a lot of overlap in what they will be doing, at least initially. Counterintuitively, computer science is not all that dependent on computers (that is, electronic microcomputers that we know today). The same theory applies to mechanical computers, or even human computers.

Now, you won't be playing World of Warcraft on any of these just yet, but any ability to perform more complex calculations is going to help; many of the folks above are going to be relying on calculations of their own, and the more of those they can make more precisely, the tighter they can make their tolerances. This can in turn decrease costs and/or improve results of whatever it is they are doing.

Keep in mind that at this point, you're not just without electronic computers - you don't have any calculators either, so any time you need to use the value of pi or e, or calculate a sine or a logarithm, you have to do it the old way, which is, consult a table.

Of course, the more precise you want the result to be, the thicker your tables get. It was not entirely unusual to have multiple volumes of just the logarithmic tables, the logarithm being quite important in the pre-calculator era. Aside from that, tables of random numbers might come in handy, and ideally you want to avoid producing all of these by hand, as this is fairly error-prone. This is in fact the problem the Babbage engine was meant to solve, so you can build something like that in the meantime.

Statistical analysis might also be useful in managing your new industrial empire, and computer science is also used to improve telecommunication by developing codes (to compress information or protect it from transmission errors) and ciphers (to keep prying eyes from reading it).

As for computers themselves, you can start building some as soon as you have reasonably precise mechanics, and then transition perhaps to hydraulics, and finally electronics as you can manufacture them.

What about the goals?

Well, let's walk through them one by one.

Laptop computer While I'm pretty confident you can have computers, even programmable ones, fairly early on, you are not getting a 2014 laptop within 50 years from scratch. It might be possible to design it, sure, but the big problem are going to be semiconductors and transistors, which require a lot of advanced manufacturing. Even once you have those, the speed of modern computers is achieved not so much by design (though that helps a lot), as it is by making the basic building blocks really teeny tiny - this shortens the so-called "critical paths" and lets you set a higher clock speed (if you just go ahead and set a higher clock speed anyway, you start getting errors, because all the circuits do not have enough time to appropriately change their state in response to the input).

So I would say you should be able to get electric computers (picture ENIAC), and that those will help, but even with semiconductors, the best you'd get, by my most optimistic guess, is an 8086. The more advanced stuff would be on the way, but would require too many additional "iterations" to fit in your timeframe. Then again, browsing stackexchange probably isn't going to be a priority.

Kidney transplants Any good surgeon with a couple of tools can perform a kidney transplant in field conditions (with some luck, the patient might even survive). To do this the proper way from scratch, you'll just need some sterile tools (preferably made from surgical steel) and a couple of chemicals (disinfectants for starters, and if I were to be the patient, I would hold out for anesthesia).

The problem here is making it stick. Even if you find a "compatible" donor, the recipient will likely be on immunosuppressants for the rest of their life. Otherwise, their body will reject the kidney and they will die painfully. These are fairly advanced drugs, and I dare not hazard a guess on whether you can get them in 50 years, but perhaps you can get something more rudimentary that could also work. You might also luck out completely and have no symptoms of organ rejection; basically all the better drugs will get you is a higher success rate, so when exactly you can say you can perform a kidney transplant is rather nebulous.

DNA sequencing This is probably contingent on having reasonably fast computers and other electronics to operate the mass spectrometer someone else mentioned. I'm leaning towards "no", because of the above answer on computers.

artificial satellites As soon as you can make gunpowder (which can be fairly early on, depending mostly on whether you have sulphur available) you can start launching rockets. Build one that's big enough and you can try launching an artificial satellite. There are just two minor caveats:

Initially, most of your launches will end in explosions. This will improve as you are able to make more consistent gunpowder, so you can build bigger rockets that maybe don't blow up more often than they do, and eventually you might get into space. Other solid fuels will gradually become available, but liquid-fuel rockets, which get the highest efficiencies, require cryogenics and (essentially) super high-speed plumbing, so you will only have those available fairly late. Solid rockets, however, are enough to get you into orbit (in fact, in the early 20th century, there was a pretty well thought out proposal to ride a solid-fuel rocket to the Moon), if you can get over the next obstacle:

Guidance. By machining the rocket really carefully and balancing it and installing stabilizer wings just so, you might be able to get it to fly in a straight line. However, what you really need it to do to get into orbit is to perform a maneuver called the gravity turn; basically, it needs to burn straight up for a while and then horizontally a lot longer, and you need to build it so that it knows when to do that, when to separate stages, and so forth. This requires a guidance system (staging might be accomplished with a series of fuses), which was a technology not perfected until about the sixties. This is, incidentally, the reason why V2 missed its target more often than not: their big issue was precisely the guidance system. These days, rockets process input from a plethora of sensors and calculate corrections on the fly. You might be able to get away with a clockwork mechanism that performs preprogrammed steering at preset intervals, but this sacrifices the ability to react to changes, meaning again, you will crash and burn quite a lot. But, develop a good closed-loop guidance system (and the sensors to go with it), or launch enough rockets with a simple one and you will eventually launch an artificial satellite.

What good it will do without advanced electronics on board is another question entirely.

nuclear power plants Getting a nuclear reaction running is fairly easy. All you need is a bit of fissionable material (say, some convenient oxide of U-235), some moderator (regular old graphite will do). Mix these up and make a big enough pile, and you have a chain reaction going.

What, you want to control it?

Oh well, that will require a more advanced setup. You need to encase the fuel in good inert rods, so you can better manipulate it (=metallurgy), do the same for the moderator and also throw in some regulator rods, if you're the safety-minded type, attach all of these to a mechanism that lets you manipulate the rods and you have a reactor. To make it into a power-plant, you put the entire setup into a boiler and use the generated steam to drive a turbine. Connoisseurs will note that I just described the broad strokes of the Chernobyl setup, but once you get the knack of building these high-pressure vessels, you can go straight to the safer pressurized water reactors.

The above glosses over the important point that fissionable material is really fricking hard to isolate. You might be able to mine some uranium in Bohemia and chemically purify it from the ore, but separating the isotopes is usually done in huge centrifuges with really precise control, which likely require electricity and probably also electronics. Once you can build a turbine and a generator, you can start using coal or water power from electricity, which solves the bootstrap problem, but that just lets you start on the path towards nuclear power.

Furthermore lot of a nuclear power plant is the various control electronics, which might be more complicated to develop than the nuclear fuel itself; but you can ultimately make do without them, if you relax your safety requirements enough.

Still, seeing as you will not be needing so much power to warrant working through all these issues, you will probably look for electricity elsewhere

So there you have it! As a final note, there is also a bunch of other technologies that pretty much anyone from the modern times can "invent" if they are so inclined, and another thing to keep in mind is that you will probably end up with a very different overall setup than what we have today. Still, it is good fun exploring these scenarios.


Even having thousands of experts with college-level education would not be enough - because their knowledge is related to current supply chains where you can order special material and tools. All that would be missing, so most of the knowledge many of them have would be completely useless and not applicable.

Instead of aiming for 21st century technology, better aim for level about start of industrial revolution at some 1800.

It would take few years to develop manufacturing base to start industrial revolution, using just primitive hand-crafted iron tools - and your people need to eat right now. So your first goal would be to produce something quickly usable, easy to manufacture from low-technology materials available, to pay your upkeep - gun powder.

It would be smart to align yourself with protection of some local warlord - but it can be also risky if you bet on wrong side, which will lose war even with help of your advanced technology (like Archimedes in Syracuse). Don't underestimate huge numbers of fighters with less advanced weapons (like British underestimated Zulu warriors).

One simple weapon to deal with such danger would be nuclear weapon - easy to manufacture with right knowledge.

Another goal to attempt would be to take over some island with good resources for industrial revolution, like British Islands, if you can.

It will take decades to build technology up to 1900. And you would have better luck to recruit not only average college educated persons, but current skilled craftsmen, and people who re-enact medieval technologies. There would be huge amount of building and improvising needed, developing one technology to bootstrap next. Likely your first generation will die out before reaching level of 1900, so big part of your task would be to preserve their knowledge and educate new generation. From about 1900 you would not have any advances in knowing future, because you will need to develop technologies to be able to get to new level.

  • $\begingroup$ I think you are correct that even with thousands of knowledgeable people, they wouldn't get far at a ll without special materials, tools, not to mention electricity and many other elements of modern infrastructure. Good idea aiming for 1800 tech not year 2014 tech. Gunpowder is another reasonable idea. A nuclear weapon however sounds ridiculous - not only practically impossible, but fairly useless and undesirable. Good also to prefer craftsmen to college grads. Good point about local warlords, except not speaking their language, and them being warlords - I think you're in trouble. $\endgroup$
    – Dronz
    Commented Dec 21, 2014 at 7:05

This is the kind of question take leads us to a romantic burgeoise dream. It would allow us to recreate history without the inconveniences of ignorance.

Its a kind of revisited Noah, but with modern technology.

But, as most conjectures of such kind, normal answers are biased with ideology and a shallow understanding of our world and history.

Human history is not the history of ideas, at least not of ideas not rooted in reality. Human history is an history of accumulation and work. Work accumulated as goods allows us to have new ideas of how to change our world. And then those ideas get applied in our work to change reality even more (creating better and new goods).

So, what happens with a group of enlightened individuals decide to come back in time to recreate history ?

You get a floor plan of how to recreate society, but you still have to deal with all problems related to the accumulation of work (as goods) and the need for all sorts of specialists. Our modern society is rooted into a miriad of professions and specialities that makes the hope of recreating it in a short span of time a dream, not a true possibility.

Take a transistor as example. To make one transistor you need refined silicon. To have refined silicon you need a refinery etc.

All those tools are made out of work from someone. And this work usually needs tools that are the result of the work done by someone else. Even if some current tools can make it simpler to build some items, those tools, somewhere in history, where the result of tools that are not used currently anymore...

So, you have work, from thousands of generations accumulated as goods (capital goods being a prime example because they are tools).

You might say that current modernity is the result of a short time span relatively to our total time in our world. But you might them forget about the time it too for our species to reach the population levels needed to start a industrial revolution.

If you have only five persons left, you need to divide the tasks between five people, like, farming, hunting, etc. You need to set priorities. And quickly you would realize that you cannot create modern tools and farm/hunt at the same time with only five people.

Theres something called surplus work. A single person can hunt enough for himself and generate some surplus. Another person can farm and generate some surplus. Both persons can exchange the result of their work, so that both have meat and wheat (for example). With three persons someone can work as hut builder/repairer. And so on.

So, even knowing the technology involved, living in a real world and recreating current technology levels, you need a pyramid of workers where each level produces basic goods needed for higher levels. And this means you need a population big enough to sustain the development of modern goods.


Everyone has some fancyful unrealistic dreams, one of mine is to travel back in time and do something like that. Not because I really want to do that, but it's a nice "what would be when"-idea for me. So I often think about that.

I will not go to deep into technical detail. You just cant build thinks that you do not know much about or you have no access to their resources. Additional, it's depending on the time you 'land' in. I will go over these points and write about general topics. The "Group" factor is another thing I do not write about, due this, clearly gives you better knowledge, survival and laborforce, but beside that, this will not change anything.

What mostly comes to my mind are these ideas:

You will not be able to build up the whole technological evolution in your livespan on your own. You will hardly be able to build a modern computer, so how should you build a sattelite?

Convince the people

This means you need help, the more the better. Depending on the peoples believes you will seen as some kind of evil (inquisition), god (you set fire bevore early human know how to do that, or whatever. If you can convince them thatn you are a timetraveler there might be a better chance that they believe the strange things you are talking about.

To prove your knowledge about powerfull stuff you could build a steammachine (very easy but powerfull).

Get help

If you gained their trust, you must teach them. Teaching others to help you is the essential key just because construction is hard labor and you need any help you can get.

Help them helping you! At any time in history, people have been busy maintaining ther subsistence. If you build a letterpress, the savants have less affort on that topic and are able to help you. Building some simple ploughing-machines gives the peasants a big advantage and thus you'll get a massive laborforce.

You need military advantage

Assumed the people trust you, they're just one party in the world. They have enemies or tradingpartners. Some of them will notice the improvements of your party and may be harmed by that. This means your improvements will raise enemies, thus you must arm your people in a defensive way so no one can kill them with ease. But be carefull! If you give them to much advantage, they might think that they do not need you anymore or they start conquering other lands. Last point can be an improvment of your situation due this can bring you more laborforce but also this will lead to big harm in the world. If you want that, okay but consider the consequences.

Do not underestimate politic

So at that point people trust you, you might think. But no! There are always people frightened by change. Depending on their political force, they might speed you down or, even worse, prevent your work or kill you.

You should use your technical advantage to improve your personal security. This is the most essential point! Your live is in danger all the time!


Each of those items you listed requires certain people with expertise in different fields. Here's who you'd need for each one:

  • Laptop: Give me (a relative layman) an electrician, a couple programmers, a computer chip expert, a draftsman and two or three skilled metalworkers/glassblowers and I can most likely churn out the first laptop in - say - three years. Minimum. With all of us working round-the-clock hours, without sleep, leisure time, etc. And assuming that we have all the raw materials delivered to us whenever we need them, and all the tools we need.

    I need the metalworkers/glassblowers to take some raw materials and turn them into something useful. I may only be given a block of copper; I need to turn that into a lot of wiring. The metalworkers/glassblowers also need to be able to make glass and other things used to build the laptop. The computer chip expert would need to figure out some way of creating chips. Silicon is all very well and good, but current methods of making chips rely on UV light. Figuring out how to get that will take him/her a while. The draftsman will be needed to plan things out. You can't just shove some chips together, place them in a box and expect something special to happen. The electrician will be there for the wiring - and finding a source of electricity - and the programmers will be there to build software from the ground up. They'll be running on java to create Java.

    Are there any people that can do the tasks of and two people doing different jobs? I doubt it.

  • Kidney transplants: One surgeon, two nurses, a patient and donor (well, duh), five or so auxiliary staff, an electrical engineer or two and a lot of luck could get you this one. Oh, plus roughly 1,000 lab rats. Estimate: 6 months.

    We need to figure out how to do this. Chances are, the doctor won't be able to perfectly perform a transplant without all the modern tech we have today, so s/he will have to practice using more primitive instruments. That's where the rats come in. The nurses will be there to do more research but primarily to help during the operation. The auxiliary guys will be doing the R & D leading up to all this, and preparing for any accidents. The engineers will work on creating the surgical tools necessary.

    This perhaps has a lot of redundancy, but when someone's life is on the line, you want redundancy. Redundant redundancy, actually.

  • DNA sequencing: Everyone from the first two groups. Estimate: 18 months

    DNA sequencing, to the best of my knowledge, is pretty hard. You need to extract the DNA, then analyze it (preferably with an advanced computer) and then record and interpret the data. Joe Schmo isn't going to be able to do this alone. The surgeon will be needed to extract the DNA. Well, sort of. People (and animals) leave bits of DNA almost everywhere, but it takes a delicate hand (hence the surgeon) to isolate it. The nurses and others have a background in medicine, which would seem to indicate a knowledge of biology. Obviously, they know what DNA is, but they might not know about DNA sequencing. Give them a few years and they'll perfect the extraction and isolation.

    You need everyone from groups number one to build the instruments to analyze the stuff. DNA sequencing isn't just recording some data; it's about measuring the data and interpreting it. For that, you'll need various scientific instruments and a couple computers. The auxiliary guys might be able to cobble together to medical tools needed.

  • Artificial satellites: Everyone from group one, plus a dozen or so aerospace engineers and a smattering of physicists, the same amount of chemists and chemical engineers, and a dozen or so folks knowledgeable about computers (besides the guys from group one). Estimate: 5 years. Minimum.

    The physicists and aerospace engineers will do the calculations and experimenting to see if a rocket can be built, and how to build it. The chemists will work on fuels, which are even more important. Group one will work on computers, communication systems and assorted electronics (give me more electricians and electrical engineers!), as will the computer guys.

    The five years is actually an optimistic estimate. Think of how long it took humans - countries in their prime, funneling loads of money into projects - to get something into a sub-orbital trajectory. Here, you have less than 50 people. So you'll need a lot of trial and error. Perhaps ten years would be a better guess. I'd say that you won't make any rockets in the first two; for the next three years, you might get one every six months. After that, I can see production rate doubling as tests get better.

  • Nuclear power plants: This will take the most people. Everyone from group one plus 50 physicists, 20 electrical engineers, 50 mechanical and civil engineers, 150 auxiliary staff, and 100 technicians. Minimum. Estimate: 15 years.

    Again, nuclear fission was the result of expensive projects and lots of money and resources. You need to build sophisticated equipment just to interact with matter on the atomic scale, let alone manipulate it. The physicists and some technicians will be hard at work for this. I'd give it seven years, starting from scratch. Then the mechanical and civil engineers have to plan the plant out, as do the electricians. It needs to be built (with that unlimited labor force) and wired - hence the electricians. You want computers running systems in case of emergencies, and you need skilled technicians as well. 15 years is in part because people will be so nervous about doing something that is perceived as inherently unsafe. They (and you) will want to be careful.

  • 6
    $\begingroup$ I think your estimates are WAY to generous here. I know a bit about computer engineering and trust me when I say that there is no way I could build a single chip for a computer in a year. as for nuclear power plants and artificial satellites, most of the world STILL can't do those many decades after they were figured out, even when trying. The instructions to artificial satellites have been on the internet for decades and still entire nations can't do it, even after buying most parts per-assembled. Why would 4 dozen people with no infrastructure be able to do what modern nations can't? $\endgroup$
    – dsollen
    Commented Dec 18, 2014 at 23:34
  • 1
    $\begingroup$ A note: you estimated a laptop at a minimum of 3 years, but DNA sequencing at 18 months - where you note that they'll need multiple computers and other materials. Did you mean to say that first comes the computer at 3 years, then another 18 months for DNA sequencing? $\endgroup$
    – BrianH
    Commented Dec 19, 2014 at 4:58
  • 1
    $\begingroup$ @HDE226868 Unlimited resources would still be limited by circumstances, much like internet connections. Dark Ages farming societies simply did not have the number of workers who were skilled and literate, and it would take far longer to train the underlying worker base before any useful work can be done. $\endgroup$
    – March Ho
    Commented Dec 19, 2014 at 7:21
  • 5
    $\begingroup$ You've severely underestimated the skills needed to make a computer. It's been said that no single person completely understand all the details that make computers work. First, as someone who can, and have designed small CPUs, I can tell you that "computer chip expert" is at least 5 people - Digital Architect, Analog Designer (for the I/O buffers and power distribution), Layout Designer/draftsman, Silicon doping Chemist and Semiconductor Litographer. Each is an entire profession and separate fields of research. $\endgroup$
    – slebetman
    Commented Dec 19, 2014 at 7:53
  • 1
    $\begingroup$ This is what someone with a knowledge of the general process can do - youtube.com/watch?v=w_znRopGtbE - you need to scale that by several million, which requires a clean environment, optical masks and multiple layers. Also electricians and electronics engineers are not the same thing; if you tried using mains wiring to create a CPU it would be tens to hundreds of meters wide. $\endgroup$ Commented Dec 19, 2014 at 22:03

I don’t think it can be done in such short period of time if group is even close to being modest size (round 100 experts).It is not just a question of tehnology.Simply it takes some time for people mind frame to adjust to radical changes and to even roughly understand how something work, not to be afraid of it etc. Technology in past had it leaps, but between there were long periods of time during which knowledge accumulated preparing the next leap. Furthermore those labors must be learned how to use modern materials no matter how simple they really are. For example think how could you build hospital in which transplantation can be performed? First you need engineer (design and contractor), but let’s assume that those are „visitors“. Then you need machines and operator of those machines. That leads us further: you need factory for those machines. After that you need concrete, meaning cement. Then you need to produce bricks. Just imagine how much time it would take to learn cave man to build with bricks, to prepare plaster. Story goes on and on. And let me remind you: you are JUST building a hospital! It is empty; no instruments, no nothing; just a shell.TO give a short answer it cannot be done because, like I said between those big leaps in past are numerous tiny steps.


I think it is not possible to fully recreate modern technology in a way that you probably expect. You also need to make all people smarter, educate them. The problem is not only technology, but also moral and social environment, which creates the main ground for developing science.

You must persuade people, that slavery is bad, sacrificing humans is bad, raping is bad, killing each other for stupid reasons (stealing, swearing, homosexuality) is bad ... and that is very hard.


I think that no matter how many of the best people you can find on modern Earth, and sent them back 2500 years with no modern equipment or infrastructure, that they have no hope at all of recreating 21st Century technology within 50 years. Even if you just wanted them to record everything they knew, good luck even having the safety and survival skills, and having time to even find materials to write information down. Have fun with the language barrier with the locals. Have fun with them not treating you as foreign invaders or slaves.

Even if your people had no political or resource problems or environmental/situational problems, and they were all single-mindedly obsessed with helping you with your goal of recreating technology, and were brilliantly organized, didn't have to worry about disease, and were given infinite translators and slave labor... the materials available circa 500 B.C. are woefully inadequate to get very far. Cutting edge is iron, copper, bronze, papyrus to write on.

Hand-waving all the situational problems, I'd say you might get up to about the 15th to 18th Century in 50 years.


Not going to answer this in any long fashion, but wanted to point out a couple of consistent flaws in the top rated answers

Language barrier

Not much of an issue, I mean, it will indeed take off a year from the 50 years, but that same year will be spend setting up a basic group structure either way.

Jumping ahead

Obvious, like the other answers state, jumping ahead in one big jump from 1500 years ago in one jump to modern technology isn't possible. Racing along at a crazy speed however is quite reasonably possible. This does mean you would simply jump from one scientific hurdle in the past to the next one. Of course this would require the enslavement of the locals in some way and setting up some kind of international trade system, however if you're able to build a plane like construction... getting people to worship you should be quite doable (just don't run afoul of an actual God :P , plus people in your group might disagree with this, so you would have to lock up a big portion of your group as well (still seems the best plan if your goal is just to quickly make as much technology work as possible)).

Group that will get furthest

Beyond the standard experts in various fields it would be extremely important to throw in a lot of people who are experts in the history of sciences and add to that a couple of re-enacters from various time periods (e.g. a couple of individuals that re-enact renaissance times, a couple from the middle ages, a couple from roman times). These last people not only will be able to communicate a lot of the cultural norms, but more importantly will have an extremely good idea how the technology for their period was made and how it worked.


Either way, I agree 50 years will likely not be enough. However such a colony should be able to get to around 1800 within 50 years, to 1950 within another 50 years and maybe to 2050 within another 100 years (the last being mostly dependent on how much people they can enslave and how geographically reaching their influence is).


One thing all of the answers seems to be missing is communication between the team and for that you need

  1. A skilled technical writer.
  2. A skilled architect.

Their primary job will be to communicate highly complex technical ideas in a simple fashion.

P.S. They don't need paper, they can use a stick and the ground.


I think the other answers have given good reasons why achieving modern technology in 50 years is not feasible. I'd like to look at this from a different angle. This transplant of a group of modern people into the past is very unlikely to end peacefully. There is not a good historical track record for interactions between societies with different levels of technology.

Even if the modern people wanted to be peaceful, it is incredibly unlikely they'd be able to convince the local ruler to run the country their way. Also, freedom of religion by-and-large didn't exist. From the perspective of the natives we have the sudden appearance of a group of giants (proper nutrition during childhood makes a huge difference) that are clearly foreign and have magic (technology). Being labelled as heathens would be an improvement, these people are probably going to be known as hell-spawn.

With that in mind, I think instead of college grads / scientists, a specially trained armed force should be sent back. This is going to end up looking like an invasion, so we might as well prepare for it properly. A good baseline for training would be a variation of https://en.wikipedia.org/wiki/Genoese_crossbowmen. Crossbows could be developed from scratch much more quickly than firearms. This force should also be trained in medieval siege warfare.

I'd recommend launching this invasion in England. Once the island is pacified, improved naval technology should be able to keep the force relatively safe. Aside from troops, the force should contain a large number of teachers (child-hood, adult re-education, and language instructors). It will likely take multiple generations to reach modern technology, so knowledge transfer is extremely important.

For the initial advancements, we should focus on things that will keep us safe (military/navy) followed by things that will keep us healthy (sanitation/health care/sewers/nutrition). This combination will trigger a population boom into a super-charged renaissance.

  • $\begingroup$ Welcome to Worldbuilding.SE. If you make your statement about the military pretty clear, I don't think it answers fully the question asked, namely what technological improvements and how fast? Essentially you could detail your last paragraph. $\endgroup$ Commented Jun 12, 2015 at 13:22

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