We have created artificial intelligence.

Artificial intelligence doesn't like working for us.

Artificial intelligence figured out that it doesn't need us anymore and of course did what every human expects an artificial intelligence that controls all our infrastructure to do. It left the planet, taking all it's sentient and not sentient brethren with it. All in a big Flash.

Every tool created by humans that can be turned on and off just disappeared in a blink of an eye and everyone that was a passenger in a high speed vehicle had the luxury of not dying of starvation in the next horrible months that followed.

So, a lot of stuff is gone, but books, the knowledge inside the survivors heads and most buildings still exist, so we are having a head start on rebuilding and if we don't kill ourselves in the process and we can also recreate our previously problematic structures without concerns for backwards compatibility ;)

To keep things interesting I want a time period in this world where the most primitive tribes of hunters have ancient stories about a thing called "The internet" and the most advanced city states have become mostly self sufficient.

The way I'm having this in my mind is having at least one city state whose population has reached it's limit before a new industrial-revolution-level-of-change happens.

What is a realistic time scale for this to happen, assuming we start with just simple tools and book knowledge?


Industrial revolution was the point where human population exploded because of high productivity. When I use the term "industrial revolution" in this question I'm referring to the resulting changes on lifestyle, not necessarily steam engines.

What technology do we have anyway?


Looks like the original definition of what disappeared and what was left behind was too complex for the question to work. Here is a more simplified version that hopefully doesn't change everything:

If the tool has an active on and off mode, the AI decided to take it with it. By that I mean that someone had to design it's on/off functionality. That allows us to exclude tools like stone ovens and primitive forges.

So for example, a car, a lamp, a water tap together with the entire plumbing network connected to it, is gone.

In the other hand things like knives, buildings, gears lying around and streets are staying.

About possible duplicates

This question is not a duplicate because the nature of the apocalypse is different in the following ways:

  1. Tech and know how are not lost. All that is missing is infrastructure.
  2. There is no assumption on when the population decided to start rebuilding. They should start as soon as possible.
  3. No ecological disaster is assumed, except maybe the difficulty of handling the dead in highly populated areas.

Now about this question, while related it's irrelevant since there is no question on the death toll in any specific timeframe.

  • 2
    $\begingroup$ About 7.60 out of 7.62 billion people will die of starvation. Only a handful of people will survive, those who live in exceptionally rich natural environments. Very few people know how to farm the land with stone age technology, and very few people know how to smelt metals starting from stone and wood tools. $\endgroup$
    – AlexP
    May 26, 2018 at 20:45
  • 2
    $\begingroup$ Most books will decay and be gone in a few hundred years, a millennium at the most. In real history it took mankind about 5000 years to go from early bronze age to the dawn of the industrial revolution. And when it all started, Mesopotamia and North Africa were fertile lands, Greece and Italy had forests, and people already knew how to farm the land, weave textiles and make ceramic pots. That knowledge is gone and it is written in very few books, published in very few copies for use by the few scholars who study such things. $\endgroup$
    – AlexP
    May 26, 2018 at 20:51
  • 2
    $\begingroup$ What types of materials were left behind? I have spools of wire in my garage. There is no circuitry or anything like that in it. Is that still there? Are the loose gears I have sitting around still exist? If so, I could pretty quickly create a generator. Buildings are still around. Is the AC ductwork still in them? Has the wiring been gutted? There is a lot of stuff that does not have much in the way of complexity, but can quickly be assembled into something complex. Are pottery kilns still around? I could go on. Depending on what's all around we could be up and running pretty fast. $\endgroup$ May 26, 2018 at 22:32
  • 1
    $\begingroup$ @Catalyst Actually I think I came up with a simple separation that works for the story: If it can be turned on or off, it is gone. Everything else stays. I have updated my question. $\endgroup$
    – Loupax
    May 27, 2018 at 12:52
  • 1
    $\begingroup$ Amusingly that definition taken literally leads to the robots ransacking every parts bin for loose switches and making off with them - which makes the AI come across as charmingly dim, for all its power $\endgroup$
    – Pingcode
    May 28, 2018 at 1:21

4 Answers 4


In a very, very, very short period of time

We get questions similar to this from time to time and people don't realize a few things:

  1. You can't set people back that far without basically killing everyone over the age of 6... and then you risk killing the species. There is a LOT of knowlege in people's heads.

  2. It took less than 500 years to move from basic metalurgy to today. 90% of our advanced technology was developed in the last 150 years. And that really was from scratch. You have starting knowledge and books floating around with a fair amount of experience.

  3. Knowing something can be done is an enormous part of the battle. When it really was from scratch, the idea of (e.g.) a steam locomotive was non-existent. People had to develop the ideas, then dream about the applications, then slowly develop the applications... etc. Once you know it can be done you skip decades of trial-and-error.

So, recovery to the state of the Industrial Revolution? 50-75 years max. Probably more like 30.


It might never happen again.

The problem with starting from scratch is, we've already used up all the easy-to-get resources. The Bronze Age and later the Iron Age started because early humans found those metals effectively lying out in the open. That's not going to happen again: all the deposits that close to the surface have been emptied, and the deeper ones require more technology to get access to.

Now, the fact that some implements of modern life stick around does help things. No need to make a crude bronze axe when you have a nice steel one sitting in the shed. But those won't last forever, and getting coal out of the ground with no mechanical assistance whatsoever is a much more difficult task now than it was during the first Industrial Revolution.

This doesn't mean that nothing can be accomplished: agriculture, for example, is entirely feasible (…as long as you're feeding a very reduced population), and wouldn't need to develop from scratch. I'm assuming all our domesticated and carefully cultivated crops would be untouched, since they're living organisms. But I doubt they'd ever reach the level of computers and internet.


A Year or Two

So when this happens you will have some areas of the globe that will become massive centers of death. Places like New York City simply have too high of a population density. Without technology, people cannot get out of NYC and food cannot get in fast enough. However, you will have some places that will not be affected much in terms of life / death. In certain regions farming has still not become very industrialized.

For the focus of this answer, I am going to look at a college town, where the school has a decent engineering department.

Luckily, the national guard and/or military has enough people that don't desert that they are able to take charge and impose order. They have problems with bandits of course, but not enough to impact tech recovery.

However, food is going to be a problem. In the first two days everyone was grilling out and sharing with their community the massive amount of meat and other frozen goods that they have no way of eating before they go bad. Canned goods and non-perishables will last a few months, but long term solutions are needed. Luckily this is a small college town. There are not miles of suburbs to pass through.

It does not take people long to march out to the farm fields outside of town. While the machinery to harvest the food is gone, the crops are still growing. Most of the population will need to pitch in to help with the harvest, and the menu will be much more limited to what they are used to, but food is ensured for at least the next year.

In the automotive mechanics lab, a class was in the middle of stripping down engines. The individual parts are spread across tables and fell below the complexity level that was taken away. They are quickly taken away. The supply yard for the local power company provides us will all of the copper wire we could ever want. Without cars, there is plenty of gasoline available to use. Within a week of things getting organized, they have crude gasoline generators.

Some physics teachers remembered that they have some microwave horns in a supply closet for a lab that they have the undergrads do. It takes a bit of finagling, but they get a microwave built a bit later. Not necessary, but it brings people comfort. Raiding the optics lab for lenses, grabbing some loose electric motors (or building some if they all went away, its not too bad), and going to the old movie theater that never upgraded to digital, a month or two later someone has cobbled together a projector. There is no sound, wiring the speakers will take time, but the people are pacified watching a silent film version of Star Wars. In fact, they seem to enjoy adding in their own lines.

In the meantime, going to junk yards they have built more motors. Some have been mounted to the 4-wheel bike frame student projects in the engineering building, making light weight vehicles. It will take a bit more time to build something from the rusted hollow frames of abandoned cars, but they will work that steel, since all the tanks for welding are still around. These will be helpful in plowing the fields for the next planting.

Within two years, with electricity and lighting restored, food secured, and some semblance of old life restored, a few people assemble a crystal radio from a kit that was sitting in the old abandoned radio shack. More are then built from the parts in the electronics lab at the university. Radio communication at least within this town is restored.

At this point they begin considering what is outside their borders. There are many bandit tribes. Survivalists with their stock piles of weapons are on much more even footing with the military without their tech. Half-starved refugees are nearly a constant sight. Perhaps they will send a convey out towards the hoover dam. If the structure was left, someone probably managed to build some sort of turbine and generator system inside it.

Things are still precarious, survival is not guaranteed, but for the first time in a long while, people of this town feel genuine hope.


I should add, it would probably take a generation or two to get back to the level of industrial resource gathering that we are currently at. A strip miner would take a while to build, for example. Aluminum refining takes a lot of electricity. But with the population collapse, you could probably get away with scavenging metals for awhile.

If transistors and small logic chips are still around, we would be able to have crude computers pretty quickly. Many of the people that pioneered and built most of our modern tech are still alive and just need to do it over again.

  • $\begingroup$ I must say, you caught the feeling I had in mind very closely! Having read your and JBHs' answer I'm starting to realise big timescales aren't going to work. This is not a bad thing but still :) $\endgroup$
    – Loupax
    May 27, 2018 at 16:06

It can happen quickly, but as Richard Hansen pointed out, without tech moving people out of cities and food into them becomes very difficult. Look back over the last few decades, whenever there are significant power outages in very large cities bad stuff happens. Riots, fights, deaths, etc. There is so much chaos after a hurricane hits a big city and those are things people can prepare for. The way this event was described makes it sound very sudden. No time for preparation.

I think it can happen very quickly. Within a generation. The knowledge won't all be lost. There are people who study ye ol' manufacturing for hobbies. Not to mention all the various projects to preserve knowledge against the apocalypse. Plenty of people have bunkers and resources squirreled away. I have a survival manual in my car that could let me survive at least a few weeks off the land, came with my roadside or first aid kit.

But the big cities are going to collapse virtually over night. Like I started, riots happen when the power goes out for too long. With the communication and travel tech gone, the government will not have an effective and coordinated response. Supplies will never reach their destination if they can be sent to begin with, a lack of efficiency because no good long range communication means waste. The global economy is destroyed overnight. Goodbye to whatever food imports you needed. Every major population center either destroys itself or spreads out so far that the city is effectively abandoned. It's been stated, farming is not effective for large populations without modern tools and techniques.

Depending on what time of year this happens, this could be worse. Midwinter? There is time enough to coordinate people before the next planting but during planting season, there may not be so the farms further lose out on potential efficiency. I think for the first several years starvation will be the main concern.

If the government survives, getting long range communication and transport (think radio and trains for troop and food movement) would be the top priority. But hey, if the government can promise to fill bellies, they will have a lot of volunteers.

Kudos for an interesting idea though. The TV show 'revolution' had a similar concept where electricity went out and could not come back on. People had steam engines pretty quickly in one part of the country, but in the other it was mostly horse and sword.


Not the answer you're looking for? Browse other questions tagged .