# How would humanity enter a Dark Age?

Humans have grown fat, complacent and cock-sure of the certainty of future progress, arrogantly expecting to build minds in their own image. They even dream of building themselves a city, with a tower that reaches to the heavens, so that they may make a name for themselves in space, where they wish to blacken the skies with their footsteps and besmirch it with their greedy mining robots.

Too bad for them and their silly dreams. They won't get the chance to return to the Moon, not for centuries. Why? Because a new dark age is coming.

What are the omens, the dark messages that foretell the coming of this black age? What is to bring this dark age about?

If that was too poetic, imagine a 90% drop in GDP/cap, a 60-70% drop in life expectancy, general loss of culture and knowledge, as well as a drastic drop in public and private safety and security. What matrix of factors could lead to such an outcome?

In order to objectively judge a "good" dark age entry point the following criteria have to be met:

1. No Daemon-ex-machina to save us from the relentless march of Progress. So out go aliens, asteroids and supernovas. The cause must start here on Earth and be the logical (dialectical, to borrow Marxist terms) conclusion of our own progress (or was it hubris?). While those are possible (and thank you for the pre-edit answers) they are now outside of the current scope.

2. A clear and plausible mechanism to get us there from here. If a doom-bringer is visible from a mile away, presumably people would not go there unless severely pressed from all other directions. (i.e. the Singaporeans knew the dangers of unshackled AI, but the desperate circumstances of a 3-front war while outnumbered 1000:1 forced their hand)

3. The disruption must be unstoppable once started, persistent (what's left of humanity can't simply go back to normal in 3 years) and widespread (i.e. Switzerland can't simply sit this one out). Pockets of relative high-tech might persist, such as the Massachusetts Institute of Theology's department of Applied Philosophy, but progress in any scientific field must be severely curtailed and even reversed.

• We wait a few years... – PlasmaHH Jan 27 '15 at 10:31
• Not really an answer, just food for thought, but I'd ask whether the so-called "Dark Ages" were really that dark to people living in them. I've never really understood why Rome being conquered by 'barbarians' was all that much worse than the rest of the world being conquered by the Roman army. Of course, you were a Roman, you might understandably have a personal preference :-) – jamesqf Jan 27 '15 at 20:22
• – a CVn Jan 27 '15 at 21:15
• Isn't this the end game of the anti-vaccination crowd? – Geobits Jan 28 '15 at 20:50
• Install a TVTropes app on every smartphone. – Darth Wedgius Jun 29 '15 at 6:09

I haven't read through all the answers in detail, but there is one obvious possibility that I don't see anyone else having really mentioned so far: peak oil. Or more generally, peak available resources.

First a bit of background. "Peak oil" refers to the moment in time when oil production (or extraction, rather) reaches its maximum rate, or "peak". This can be on the level of a single oil well, or on the level of the entire world. I'm going to talk about peak oil here, but the same concept applies to any resource which is non-renewable within human timeframes and which the society depends on.

A very large fraction of our world's current energy mix comes from fossil fuels, and a large fraction of that is oil and gas, which are both for all intents and purposes non-renewable in time spans relevant to humans. If you (for some value of "you") are consuming a resource at a greater pace than it is renewed, it follows logically that at some point you will run out. (I'm sure there's a way to prove that using MathJax, but I don't think I need to.) Peak oil isn't about running out of oil, per se, but it does have the consequence of running out of a stable supply of cheap oil. When all that is left is deep water oil, oil from tar sands, and so on, you may very well technically still have lots of oil left, but you won't be able to get it out of the ground for cheap, and you might not be able to get it out of the ground at the rate needed. So the price goes up, causing a much greater fraction of the world's total economic output to go to energy extraction just to maintain the amount of energy required to maintain the status quo. If you normally pay 2% of your income for electricity and suddenly that figure jumps to 10%, something has to give. Now scale that up seven billion or so times. Our current oil extraction rate is on the order of 80 million barrels per day; one barrel is about 160 liters; that means we currently go through some 13 billion liters of oil every day. When the price goes up, demand eventually goes down, which is likely to cause the price to go down; rinse and repeat a few times with violent fluctuations in price both up and down as the world society at large struggles to recover. Alternative energy projects are likely to get scrapped during low price periods, and funding is likely to be scarce during high price periods.

Experts debate when peak oil will happen, but I have yet to see a credible argument that a finite resource will not eventually peak and start to decline. If a society has grown used to, or even depends upon, that resource, then the decline in the production rate of that resource is going to have an impact on the society.

The western world today is largely in such a situation with regards to oil. We use it to manufacture things, we use it to transport things, we use it to provide heat and light (by way of electricity), we use it to grow food (by way of farm machinery, which itself is constructed using oil and petroleum products), we use it to make toys and kitchenware (plastic!), we use it to mine other primary resources, we even use it to construct and maintain "renewable energy" sources such as wind power plants or solar cells.

We know for a fact that on a human time scale, oil is finite and thus if we keep consuming it at a fixed rate we will eventually run out; a plausible argument can even be made for that we are about to hit the extraction rate decline now to soon. This satisfies your first two criteria: it starts here on Earth, is a logical extension on our current situation, and there is a clear and plausible mechanism to get us from where we are to this situation.

That leaves your final criteria, that the process is unstoppable, persistent and widespread. Let's take those in turn.

Unstoppable: Once you've burned the oil, or made plastic, or whatever else you do with it, you really can't put the genie back in the bottle. Reuse of materials can go some of the way, but not all, and eventually entropy wins out. We have yet to perfect the perpetual motion machine. You can invent new technologies like cold fusion power plants, but our past results in such endeavours are not promising and it almost certainly won't get easier in an energy-constrained environment, as I alluded to above. As we require energy to even extract oil from the ground, read up on the concept of EROEI ("energy returned on energy invested"). By the time you only get a few times more energy out of the oil compared to the energy investment to get it out of the ground, extracting the oil for the energy doesn't make sense any longer. And if you do still extract it, you leave even less than you used to have for the future.

Persistent: Same as above; if by "normal" you mean our current western lifestyle, that is heavily dependent on oil (and other fossil materials) and if those aren't there, there's no going back. You can make various changes to draw out the process of change, but you can't at time $T_{n}$ go back to the state that you had at time $T_{n-1}$ in any plausible manner when going from $T_{n-1}$ to $T_{n}$ involved some irreversible process such as running an engine on some of the energy you used to have, and the energy used to go from the state at $T_{n-1}$ to the state at $T_{n}$ was greater than the total energy added to the system during that specific time period (whether that time period is on the order of microseconds or centuries).

Widespread: A fairly small number of contries are net oil producers these days and thus are capable of being net oil exporters. Everyone else must import some or all of their oil. If, say, Saudi Arabia were to hit peak oil and face a serious decline in oil extraction rates, it would have a widespread impact because of Saudi Arabia's large share of the oil export market. And sooner or later, that will happen. It already has happened to Norway, as well as a number of other countries.

By the time people are struggling to put food on the table for themselves and their loved ones, or keep warm in the winter, and that goes on for year after year, I wouldn't really expect back issues of Nature or the Astrophysics Journal to carry much value other than in terms of how much warmth you can get by burning them, nor would I expect people to spend a lot of energy on keeping Wikipedia running or accessible. At that point, while some knowledge would almost certainly be retained, a lot of knowledge that doesn't have day-to-day practical uses in such a situation would likely be lost. With how many rely on online services already, it is far from impossible that some amount of knowledge could essentially be considered lost immediately once those services shut down.

For some further discussion on this, one might consider the words written by John Michael Greer; for example, back in April 2007, in Cycles of Sustainability,

Does this mean that peak oil can be ignored, because it poses no threat to industrial society? Hardly. As oil production worldwide continues to contract, and conservation and alternative energy reach the point of diminishing returns, oil prices will spike upward in turn, rising even higher than before and unleashing another wave of economic and social disruption. Just as the economic contractions of the 1970s and 1980s spawned intractable unemployment in most industrial societies and launched a process of downward mobility from which many families never recovered, each wave of economic contraction will likely force more and more of the population into a permanent underclass for whom the abstract phrase “demand destruction” plays out in a downward spiral of impoverishment and misery.

In such a future, the periods of apparent recovery that will likely follow each round of energy shortages and demand destruction will provide little room to rebuild what has been lost. Those periods will, however, make it exceptionally difficult for any response to fossil fuel depletion to stay on course, so long as that response depends on market forces or politics. Each time oil prices slump, the market forces that support investment in a sustainable future will slump as well, while governments facing many calls for limited resources will face real challenges in maintaining a commitment to sustainability which, for the moment, no longer seems necessary. Thus the collapse of public and private funding for the alternative energy sector in the aftermath of the 1970s will likely be repeated over and over again as we stumble down the long downhill side of Hubbert’s peak.

and in the followup Where are the Lifeboat Communities? a week later,

If the industrial world faced the sort of quick linear decline imagined by so many pundits of the Seventies and the present day, the transition from a modern lifestyle to a sustainable one would be much easier. Faced with the certain loss of familiar comforts and a future getting steadily worse than the present, many people could come to terms with the difficulties of subsistence farming and learn to enjoy the acquired taste of its pleasures. As I suggested in last week’s post and elsewhere, though, this luxury isn’t one we can count on.

Instead, the most likely course for the decline and fall of industrial civilization is a cyclic process, in which periods of respite and partial recovery punctuate the downward curve that leads into the dark ages of the deindustrial future. [...]

• Bonus: We can see this coming and we still aren't managing to change it. – Bobson Jan 27 '15 at 21:01
• It's also worth noting this would not under any circumstances be a quick, cataclysmic event. It would take a decade, and more to the effect, the price of said all-important commodity would gradually rise over that time as it becomes more and more scarce. And it's not like there's absolutely no substitute, either. It's just that the other substitutes are a bit more inconvenient. – Ernie Jan 28 '15 at 18:19
• @Ernie I didn't mean to imply that this would be a cataclysmic event, but I got the impression that the OP wasn't necessarily looking for one either. As for substitutes, I mentioned several in my answer (wind, solar, fusion are the ones I recall mentioning without reading through my answer again) and also touched on why they wouldn't necessarily work out. If you would like to delve more deeply into how those might work out in a resource-constrained world otherwise similar to ours, I think there are a few potentially pretty good worldbuilding questions in there. – a CVn Jan 28 '15 at 18:23
• Peak oil is a poor example as we have a veritable smorgasboard of technologies ready to replace it. Once the economics of diminished supply kick in, fracking, nuclear, hydro, renewables, will all take up the slack. Almost all mined minerals and the like have thousands of years worth left, and most are substitutable to boot. – Grimm The Opiner Jan 26 '17 at 11:53
• @MichaelKjörling our chosen source of energy is driven primarily by the economics. Oil is still relatively cheap, so we use oil. Nuclear's cost (outside of France) is artificially inflated by excessive regulation, so is underutilised - when oil gets expensive that regulation will fall away. The amount of fracking being done maps directly to the cost of oil, hydro is CO2 free but requires flooding huge areas of land - land can be expensive. As for renewables, well, I admit I think they're a bit of a red herring. – Grimm The Opiner Jan 26 '17 at 14:54

It all begins in a craft brewery in Central Florida. A single batch of yeast mutates, becoming extremely resilient and prolific. It survives the fermentation process, the bottling process and even its own consumption by thirsty humans throughout the state. Swimming unharmed in the acidic stomach juices of contented beer connoisseurs, the super yeast feasts upon whatever its new hosts eat, dutifully turning all sugars into alcohol.

As a result of these hearty little beer makers, everyone who drinks even one bottle of this special brew stays drunk forever.

The customers are happy and the brewery owners are ecstatic! Blind to the impending apocalypse, they scale up production and start distributing the superbrew worldwide. To make matters worse, the mighty yeast is contagious. Sober people can contract eternal inebriation from a single french kiss. Even the teetotalers aren't safe.

Que the planetary funeral dirge.

Truck drivers lose their sense of balance; they can no longer drive in straight lines. Nuclear power plant workers' eyes go blurry; they can no longer read the gauges. Food and power distribution, along with every other symptom of modern civilization collapses in a drunken stupor.

Weeks pass, with the wonder yeast consuming everything its hosts eat, flooding their systems with alcohol. They grow thin and their skin turns grey; starvation concealed by sedation. A mellow buzz transcends the world for as long as the sugar supply holds up.

Then the food runs out. The yeast stops and its victims sober up after a month long binge. They are tired and their heads ache mercilessly, but more important to them in this moment is, they are starving. Running through the streets in a ravenous rage, they begin to eat each other along with the few remaining survivors who have somehow remained uninfected and sane.

Welcome to the drunken zombie apocalypse. The sloppy staggering dead.

• I actually like this answer better than my own haha! – Feaurie Vladskovitz Jan 27 '15 at 6:34
• A version of this has happened: edition.cnn.com/2013/09/19/health/gut-fermentation-syndrome – mskfisher Jan 27 '15 at 13:20
• ...stranger than fiction. I should probably change my answers locale to Texas in honor of real life. Thx – Henry Taylor Jan 27 '15 at 13:38
• Rats! I've accidentally saved the world again. – Henry Taylor Jan 29 '15 at 6:02
• @ChrisCirefice, feel free to offer it to any of your hollywood friends. It is in the public domain now. Note to Stack Exchange members in Hollywood, if you do make a movie out of this, at least put my SE handle in the credits and send me some free tickets. – Henry Taylor Jan 9 '16 at 17:57

This scenario exaggerates current trends. I think mankind will come to their senses before it gets that bad, but you never know ...

The income disparity between managers and skilled workers/engineers continues to grow. Over several decades, the middle class shrinks. Using global trade agreements, the "one percent" minimize their tax burden. Infrastructure crumbles. A generation grows up where the children of the "one percent" go to expensive boarding schools and then to university to study law or business administration instead of STEM (Science, Technology, Engineering, Mathematics). The "skilled professional middle class" cannot afford to raise and educate more than one child per family, with both parents working full time to cling to a semblance of affluence. The masses go to the underfunded public schools and learn nothing much.

In the 2040s the last of the pre-crisis professionals retire and the house of cards falls down.

Look at this: http://en.wikipedia.org/wiki/DINKY

Or consider the European standardization of university systems, which "optimized" critical thinking away: http://en.wikipedia.org/wiki/Bologna_Process

Consider the German system of vocational training, which is "under attack" by global standardization on the American model of education: http://en.wikipedia.org/wiki/Dual_education_system

Follow-Up regarding the "critical thinking" comment -- I mentioned that I was exaggerating trends, but I don't think I'm completely off the mark.

In much of continental Europe, Bologna and related reforms at the same time took choices away from the students. The theory that a completed bachelor's degree qualifies for at least some jobs in the field within three years turned those years into a rat race with little chance to take supplemental courses beyond the minimum required, especially once realistic times for an ECTS point are taken into account. The two years for a master's degree are not enough to make up for this and take exams and write the thesis.

The previous system of Universities of Applied Sciences for the short/practical course and Universities for the long/research course gave students aiming for a career in academia more time to think for themselves and select their focus before the thesis.

But Bologna is just one detail.

• +1 for basing our demise on present day trends in education. Excellent idea which draws a terrifying conclusion. – Henry Taylor Jan 27 '15 at 19:12

All right, by the terms stated in Serban's question (which I like a lot), there's no better answer than Michael Kjörling's Peak Oil scenario. Bobson noted, "We can see this coming and we still aren't managing to change it." In other words, it's not just a hypothetical - it's something that we are actually doing to ourselves and to the planet, now.

If you look at serious studies of societal and civilizational collapse in history, such as the works of Joseph Tainter and Jared Diamond, it becomes achingly obvious that we're not a different species than the Romans, or the Mayans, or the Easter Islanders, or the Anasazi, or the Achean Greeks, or the Greenland Norse, or... well. Michael has answered the question, as posed, authoritatively.

Nonetheless, I'm going to throw another answer out there.

I'm going with a pandemic. Not an exotic one - a new strain of SARS, say. Not genetically engineered, not introduced by aliens or military research labs. Just a bad strain of comparatively natural virus. It's not even particularly bad compared to some of the doom plagues already suggested. It kills several million people worldwide, but on a planet of 7 billion that's not much more than a rounding error. Captain Trips it ain't. (I'm not being callous here - the immensity of that number, seven billion, is important to this narrative.)

No, the reason our BADASSARS is so destructive is that it mutates pretty quickly, so vaccinations and survivor immunity don't provide much protection. It also has a long latency in the human organism and is exceptionally contagious via many vectors, including the dreaded airborne vector. (It gets through filters pretty readily too.) In short, the only way to stay safe is to stay the hell away from, well, everybody.

As a kicker, let's postulate that the terminal symptoms are insanely hideous, like a Krokodil addict with Ebola. The risk of contracting the disease is intolerable, even if intellectually you know your odds of survival are good.

In other words, it's pretty carefully crafted to disrupt human contact and society. (I know this because, well, I designed it that way for your reading pleasure.)

And here's where that seven billion number comes in.

BADASSARS only directly kills several million people, as mentioned. But indirectly it kills hundreds of times times as many.

We are seven billion people on a planet that, without modern agricultural technology and transportation/distribution networks, could feed maybe one billion. When the people of the world begin to understand the implications of BADASSARS, the networks unravel. Technological agriculture grinds to a halt. Oilfield workers won't even come to their jobs anymore. Nobody can risk going to stores. Ships won't sail. Soldiers and cops desert. Nobody tends the electrical generating stations (which are running out of fuel anyway.) Why? because people are terrified of each other, because everyone is a monster in each other's eyes. They shoot each other but are afraid to loot the bodies. Civil order is lost.

Doomed citizens, in their hundreds of millions, flee the cities, because (to coin a phrase) Hell is other people.

After a few years, BADASSARS subsides. It has mutated out of its virulent phase. Still, the world we know - the world of medicine and cars, of electric power distribution networks, of hot clean water for washing up and cold clean water for drinking, of enough food that won't make you sick, of shoes you can afford, of music you don't have to play yourself (and let's face it, you suck at trying to pick out that Richard Thompson song on that guitar you can't tune), of a safe home and a safe community - lies in ruins. It's an unprecedented loss of human life, and the survivors, except for a few sociopaths - oh goody - are likely to be traumatized.

Hey, did somebody order a Dark Age?

• Delightful little plague, me gusta. – Serban Tanasa Jan 28 '15 at 2:35
• Margaret Atwood "The Year of the Flood" describes the aftermath of a man-made plague deliberately let loose by its creators. Not a dark age, actually, they hang on in there. – RedSonja Feb 4 '15 at 9:15
• I think you underestimate the fact that a decent Hazmat suit can protect you from such a disease. Sure there would be some massive disruption and economic slowdown but governments would react by heavily investing in cheap Hazmat suits for everyone. It ll never come to the point where people don't won't to go out. – Fred Nov 28 '16 at 6:54

Environmentalist scientists working on oil-spill cleanup technology design a new bacteria that eats oil. The bacteria releases the hydrogen as helium to prevent combustion, and turns the carbon into ash. It then dies when it runs out of food.

The product is hailed as a huge commercial and environmental success and is rapidly used across the globe. Because it would be bad if the bacteria contaminated oil fields, it's rigorously controlled by the original company. They provide fresh copies from the original batch every time, and police it to make sure all the bacteria dies each time.

Unfortunately that control comes at a great expense, and not everyone wants to pay for it. Bootleg copies are acquired and spread, and are allowed to continuously mutate. Eventually one batch mutates into a form that will also eat many common forms of plastic. Because it's inefficient at first, it's not obvious that it's contaminated something and spreads rapidly throughout the world, and eventually makes it into 99% of the world's oil supply.

Now the bad stuff starts to happen. Oil fields and reserves are eaten away, driving prices up sharply and heavily disrupting the economy. In the long term oil is removed as an energy driver entirely as the supply is entirely eaten away. The effect of eating plastic is nearly as bad. Many clothing options literally start falling apart as they're consumed. Insulated wires become un-insulated, disrupting power transmission, computers, and phones. Plumbing fails, leading to widespread sanitation issues. City infrastructures that depend on plastic fail as well, causing areas to go without water or to flood. Food packaging fails, leading to spoilage and mass starvation.

The economy is destroyed, and is unlikely to restart without cheap energy to drive it. Scientific investigation is stalled by the need to focus on survival, and without a robust, efficient economy it's unlikely to start again except in isolated enclaves. Entire disciplines that were largely dependent on plastics are lost - others are possible but need to be re-thought from the ground up.

• And all the extra helium makes everyone's voice super high :) – Myles Jan 27 '15 at 20:30
• Hydrogen to helium? I believe that would produce far more energy than simply allowing the hydrogen to burn. – Rob Watts Jan 28 '15 at 17:52
• Hydrogen fusion would also consume far more energy than bacteria could ever produce. :) Also, power transmission lines aren't coated in plastic. They're insulated from the ground by glass and fiberglass insulators - you see them on top of power poles everywhere. – Ernie Jan 28 '15 at 18:24
• Bacteria eating the plastic coating of wires would "only" have the effect of setting your house on fire. :) – Ernie Jan 28 '15 at 19:02
• Hydrogen to helium is extremely implausible unless the bacteria is extremely radioactive. And even then, only a very small percentage of hydrogen will convert to helium. 99% would still be released as hydrogen. The more common way biological organisms release hydrogen is as water. – slebetman Mar 22 '15 at 12:50

Multi-national corporations get to the point where their income rivals the GDP of 90% of the worlds countries, while at the same time because of greed in the financial and banking markets world currencies go into a recession.

For the first time, a corporation purchases an entire bankrupt country, taking over the government infrastructure and turns it into a private kingdom.
Other multi-nationals follow suit until a large part of the developing and developed world is privately held. Corporate branding is everywhere, few people bother to create anything without corporate funding.

A new type of serf is born: the happy consumer. Content to work the jobs that the corporation provides and consume what the corporation sponsors, most people stop trying to improve their own lives. Knowledge and skills that don't directly help the corporation are not encouraged and over time are lost.

Without any reason to strive, humanity withers. Birth rates decrease, civilization fades.

• There is a more accurate version of this already happening. One group of corporations already owns most of the wealth of the planet, and effectively controls the decisions of most world politicians, news media, corporations and banks. – Dronz Feb 4 '15 at 6:34
• @Dronz - He did ask for something that was plausible, caused by us, and unstoppable by us. I'm just projecting forward a few years. In a worse case scenario like this, a global natural disaster or giant asteroid might be one of the few things that could save us. Reset the clock in a matter of speaking. – AndyD273 Feb 4 '15 at 19:00
• It's true that some disaster could shake things up and ultimately be for the better. Such things tend to naturally occur when things get out of balance, in nature and to humans. Industrial farming and over-use of antibiotics leads to particularly nasty disease. Abuse of fossil fuels leads to catastrophic climate change. Extinction of other species leads to extinction of most species, including probably our own. I don't see the correction being that people become unhappy and reduce their population through reduced birth rate, unless it's industrial food making us sterile. – Dronz Feb 4 '15 at 22:00

Religious whackjobs invest vast amounts of money to subvert governments. They force destruction of all technology above (whatever level you want to use), dismantle human rights and install themselves as theocrats. How long would it take to destroy civilisation in this manner? Add a big war and a plague to speed things up a bit.

• Plague being the result of a decline in vaccinations in favor of divine protection or a form of purism. – corsiKa Jan 27 '15 at 17:38
• Theocracy often indulges in war too, to take people's minds off conditions at home. – RedSonja Jan 28 '15 at 6:15
• Why does it have to be religious whackjobs? What about political correctness carried to its logical conclusion? You can already see its affects. People are punished for expressing their opinions. Criticized for being ambitious and innovative. People are punished more harshly based on their "thoughts" when committing crimes. This is happening while the political correctness crowd is really but a small percentage of the population. What happens when they become the majority? What about a significant majority? No free speech, no incentive to excel, fear of thinking outside "approved" thought. – Dunk Jan 28 '15 at 18:22
• I disagree; the PC brigade are a small minority, mainly confined to the kind of newspapers read by people who studied sociology. When it gets down to it, they don't care enough to bomb schools and machine-gun civilians. Religious nuts, on the other hand, would sacrifice the whole world to get their 15 minutes of paradise. There are enough real-life examples going on right now. – RedSonja Jan 29 '15 at 11:31
• Simplicity itself. – Ernie Feb 3 '15 at 0:49

There's a very nice scenario descibed in Lars Wilderängs book "Stjärnklart". Unfortunately it's not translated to english yet. I added some of my own parts to the story.

Suddenly, in Sweden and elsewhere around the globe, electronic equipment starts to fail, the car repair shops experience a large influx of customers, cell phones go black and payment systems stop working. Modern day society which is largely optimized for high efficiency rather than robustness, rapidly falls apart as payment system, transport vehicles and other infrastructure become unusuable.

Eventually, scientists discover that the dead electronic equpiment is covered in gray dust, which turns out to be caused by nano bots operating on and through electronic conductors, multiplying by consuming the electronics itself. Maybe it's a renegade government project? Maybe it's just an evil scientist who likes to watch the world burn.

In a few weeks, faced with starvation, dehydration and lack of sanitation, civilised people realise that to survive, it's every man for himself, or at best, every town for itself. In the power vacuum created by striking police officers who have no reason to do their job, local warlords are born.

Since most food production today is completely dependent on both electricity and oil, which must be transported, the wast majority of people starve to death within a few months. The nano bots eventually face the same fate as they run out of electronics to consume, but the world they leave behind is almost completely void of any working modern day technology, and all that remains of humanity is a few million savages.

• In all fairness, if I recall correctly, Stjärnklart doesn't describe the post-event situation outside of a quite limited geographical area. There are indications, but nothing is stated explicitly, about what happens outside of that area. This is in line with Wilderäng's authorship style of focusing on each of a small cast of characters. – a CVn Jan 27 '15 at 12:11
• True, I added a comment about the fact that some of this is my own imagination. – Mårten Jan 27 '15 at 12:12
• I propose it's entirely possible to survive without electronics. – Ernie Feb 3 '15 at 0:49
• Depends on what you mean, there could certainly exist a society with a very high population without electricity. But the way society and technology is constructed today, removing electronics and electricity would kill billions. – Mårten Feb 3 '15 at 5:06

Nuclear war, brought on by misunderstandings and accidents after several decades of self-serving aggressive posturing by politicians in countries who have them, would utterly devastate the economy and human environment. I am not sure we were so far away from that in the 1960s-1980s, and it is not inconceivable the danger could rise again.

Then, see the Dark Ages of Europe. Superstition and belligerent ignorance can go a long way towards driving out and keeping away progress: combine "technology did this to us" with any of the more aggressive forms of fundmentalism (religious or not), and you won't be out any time soon.

Extreme but effective , a bunch of ridiculously powerful aliens notices we are on the edge of extinction (and unaware of it) as 2% of us are consuming most of the resources and the others are starving, and the planet cannot sustain us anymore, and more boring stuff nobody really cares about.
Well, they decide it's time to reset Earth to factory standards to give us another chance. For example they could freeze us (teleport plus suspension, see Star Trek TNG episodes "Relics" and "Second chances") for a couple millions years while the planet heals from our damage.
It would be very hard at first, but in a few decades I think we would be able to face the situation quite well.

One mega natural disaster is all it takes. A comet fragment (aka alien invasion), a massive tidal wave, the magnetic core of earth stopping and losing its magnetic field, earthquake -- nature will screw mankind in the end. In geological terms it is certainly feasible with an alarming amount of probability.

The sun will stop burning in a long - long time, I wish I would be there to witness that...but will mankind survive even that long?

To generate ideas, just look around scientific events of note and read apocalyptic science fiction.

Judging by Mai-Lai and other events where mass genocide took place - moving to dark ages is something we as humans can bring on ourselves. We do not even need nature to do that for us- its human nature and not nature that would be the culprit.

Theologically, the End of Days will terminate the world as we know it. Satan's judging hour will commence. Mankind will have breathed it's last.

TEOTWAWKI - The end of the world as we know it. The acronym among survivalist and prepper communities-they think they could survive anything.. I like the idea, but if Noah's flood starts again, I am sure you will need a boat as there will be no place to hide and nowhere to run.

Human diseases may exterminate a massive amount of human population. Sterility in future may disable the ability to procreate, and sex just becomes a way to entertain ourselves. After sometime vestigeal mechanisms kick in and we lose our ability to get orgasms. Thus reproduction becomes an act of gore. Finally mankind starts to copulate with animals and a new breed of hybrids take form, after years of experiments and failure. Somehow we become more animal than human and thus our biology adapts to our thinking pattern.

There are N number of things that can happen. The dark ages are essentially an age of lack of sanitary hygiene, disease, wars, lack of medical knowledge,no electricity, violence based politics. To get any of that visit any backward area of India or visit places like Liberia in Africa, you should get the meaning of the word Dark Ages.

• Yes, and we already have mega disasters coming our way from side-effects of our own industry: climate change, ocean acidification, overfishing, etc. – Dronz Feb 4 '15 at 6:35

Bear in mind that dark ages end with enlightenment, and when enlightenment ends we lapse into darkness.

So what you need, then, is a force conceived outside of enlightenment. Maybe a theological force; a religion with a manifest destiny to take over the world. It would have to be authoritarian to prevent escape to rival faiths, and conservative to ensure that it brutally resists efforts to advance another enlightenment.

Gee, just thinking about it that way is scary.

I'm sure glad we have no religions like that anymore!

A self-duplicating nanobot manages to escape the science lab where it was born/created due to (natural disaster or other freak accident here).

This nanobot runs off electricity and spreads across any metal surface. It was supposed to be an early prototype for self-mending armor, for military vehicles.

However, now it just uses material from the air and electricity to quietly duplicate itself across the country. It was programmed to spread first, and then fill in the holes. This goes unnoticed for so long - it manages to attach itself to nearly every metal surface in the world. Finally, the explosive growth is noticed as it starts to eat a substantial amount of electricity to continue its growth.

But its too late, they have gotten into every electrical source available and consume all of it, no more power for anybody else. It was designed to be armor, attempting to destroy it is proven impossible as it replicates too quickly. It is then proven that they are too small and widespread to prevent accidental entry into any new facility, making new constructions just as worthless as the old ones after only a few days.

The only solution is to completely abandon the energy infrastructure we have created so they run out of energy. Losing all access to electricity, society loses progress in nearly every area as the world goes dark and waits to be able to use electricity again someday - assuming these nanobots don't just "sleep" when they run out of power.

I'd say we're already heading for a new dark age or worse, from one or more potential threats.

Perhaps the worst of these is climate change. As in, we may not be able to stop it and we may not survive it at all. The omens were scientists speaking out about this for the last forty or more years. It may be inevitable because the momentum might be impossible to undo even if we stopped burning anything right away. It may wipe out life as we know it due to potential positive feedback loops which may be impossible to stop.

Here is a good TED Talk summary about how we're likely in deep deep doo doo from climate change. (positive feedback systems are mentioned at 12:00)

We'll be lucky to get off as easy as a mere dark age.

There are also a number of compounding factors, such as loss of healthy ecosystems due to natural habitat loss, extinctions, pollution, ocean acidification, over-fishing, etc.

Then there are other deadly threats which could get out of control and contribute to these problems and/or create new problems and threats. There are several very large powerful corporations doing potentially devastating things to our planet health, such as planting aggressive cross-pollinating GMO crops, hydro-fracking ruining clean groundwater, creating bio-engineered viruses, creating new pollutants such as micro-particles, polluting, etc. Also there are all of the political/economic issues and all the weapons we have, including nuclear weapons, and their potential to ruin our electronics, power, information systems.

Human thinking needs to change to avoid this. Corrupt economic, social and political thinking have lead us to unsustainable patterns of ever-increasing resource abuse which generate and sustain economic and political doctrines that tend to keep us on paths that will never be sustainable. A 90% drop in GDP isn't a catastrophic effect - it's a measure used by a system of thought that will cause us to destroy our planet (if we haven't already) and that needs to be re-understood in a way that won't have us striving for infinite "economic growth". An omen of this was the physicist who pointed out that the laws of thermodynamics also apply to economic models - basically pointing out that it's impossible to increase consumption forever within a limited system such as the earth.

Two scenarios which really scare me. Both are described far better than I can in the back-story of Vernor Vinge's a Deepness in the Sky.

Omnipresent surveillance. We are already a long way down this path. What will happen when literally every action you take is recorded forever, when advanced algorithms are deployed to comb all that data for anyone who is not fully conforming with the way that they are supposed to be living? My view is that it leads inevitably first to a tyranny worse than North Korea, and then to the complete collapse of civilisation.

Over-optimisation. In some ways this is even scarier as it is a road to hell paved with the best intentions. Society continues to automate and to deploy weak AI to manage everyday resource allocation and logistics. We appear to be entering a golden age where we can work less and play more. But the robots are creating an ever more optimised system of increasing complexity lying ever closer to the "edge of chaos". One day we slip over the edge and the entire civilisation falls apart.

Perhaps we need terrorists and nationalists to inject enough local inefficiency to stop this latter disaster. Trouble is, the push us down the path to the former.

The third possibility that scares me is that of environmental collapse. Other answers cover this so I won't expand, other than to say that slow environmental degradation could be the route to the collapse of an over-optimised global society.

Well, I don't know about historical accuracy or realism, but I'm going to go ahead and say it:

Aliens.

Imagine a scenario similar to what happened to the Aztecs. An alien race, hell bent on conquest, invades the earth with their all powerful spaceships, whose mere presence destroys all our electronics via an almost aura-like EMP field. The humans try to fight back, and actually manage to repel the overtly-arrogant aliens, who were actually here without military sanction!

And then someone catches Andromediac Flu (Or something, but you get the idea.)

The disease is incredibly virulent, and does not differentiate between race or gender or sexual orientation. It is a terrifying disease that provides a slow agonizing death. The governments rush to contain it, but the alien invasion has left them undermanned and underequipped.

Eventually, the plague subsides. All the survivors are now immune to its effects, but the damage has been done. A drastic drop in life expectancy and a terrible lingering paranoia that will damage the psyche of all mankind for generations to come.

TLDR: Alien space flu.

Edit: Just got home and realized I crafted a reverse War Of The Worlds storyline. Well, it makes sense that they would've been immunized to something we weren't anyway.

Well okay, from earth then.

Presenting 'The most delicious food in the world!', a vegan-approved drug that makes everything you eat taste 10 times better! Even the humblest of fried foods will blow your mind! This drug creates a boom in the food industry, and everyone is now on their quest to find better and tastier foods!

Then it all goes downhill.

People grow fat. Not just any normal kind of fat, but too fat to go about their business as normal. Infrastructures crumble as the people who used to run it can no longer get to work on time, if at all. Even the chefs who used to cook the food that caused this problem can hardly continue. Mass diabetes afflicts everyone, and people begin to die. There is no escape.

Eventually, the last healthy man looks down upon the empty streets filled with food wrappers and abandoned fast food stores, and realizes that he has perhaps witnessed the fall of humanity as we know it.

There are a few scenarios, and you can make up more by combining any 2 highly disruptive events (disease, volcanic ashes, meteor shower). One of the events to explain the fall, the second event to make it unstoppable.

Inspired by Perry Rhodan:

A new game comes out (World of Warcraft 2) and game addiction slowly builds up. Motivation of people drops and more and more people start working only the bare minimum necessary to live and game.

Once the global number of addicts reaches 10%, a tipping point is reached. University enrollment drops, social systems like food stamps and free health care become too expensive to maintain, some companies go bankrupt due to lack of customers, tax income of nations falls significantly, national debt raises at record speed.

In that situation there's a great famine, caused by a combination of bad weather, bugs, and the lack of workers. The famine doesn't hit the 1st world as hard because they use their private purchasing power to buy food from 3rd world countries. As a result, the famine hits many 3rd world countries with death tolls comparable to those of Ireland in the 19th century. Governments fall, making these countries unavailable to purchase food from for the west for the next harvest.

With the global game addiction, the world fails to address the causes of the famine. At the next harvest, famine hits the west, which already has it's resources strained to the limit. Death tolls are in the hundreds of millions and global trade collapses, which leads to rise of religious fanatics and nationalists, who manage to eradicate the game addiction with simple yet effective means: reeducation camps and death penalties.

With global trade collapsed, many people dead, and nationalists and religious fanatics in power, universities teach the party line rather than actual knowledge, and wars start wherever ideologies clash, or opportunities arise. Communication and electric infrastructure is hit as priority target. Killer satellites disrupt global communication. The Internet ends.

Empires rise and fall. Resource rich parts of large countries declare their independence (I'm looking at you, Texas).

By the time the new world order stabilizes, many of the global oil reserves have gone up in flames, taking entire industries with them. Electricity has become unreliable, therefore old nuclear power plants are used long after their planned lifetime, leading to the occasional nuclear accident. Local branches of once worldwide corporations have been forcibly nationalized. The internet has been replaced with a series of national computer networks, containing a fraction of the original information. Scholars who dared to speak against the party lines have been cleansed.

You can look to human history and the Dark Ages after the burning of the Library of Alexandria for an answer. Religion can very easily set us back hundreds of years. The current conservative-leaning climate in America and various European nations is already successfully stripping rights from women and other minorities, and a lot of conservatives find a lot of evil in how easily we converse and live through technology (while using it themselves, of course). Religion combined with the fact that we are set to run out of fossil fuels in our lifetime could certainly be impotus enough for another dark age.

Politics.

My answer is similar to Dunk's comment to Red Sonja's answer. I think that RedSonja's answer is plausible on a national level but not on a global level. This answer also has similarities to David Fass's BLS answer and o.m.'s educational reforms would help as well.

Stagnation is generally sought by those already in power. It helps them keep what they already have. Change is always dangerous for those in power. Look at most eras of world history and you will see that the powerful generally seek to maintain the status quo.

The idea of "fairness" spreads throughout the world. No one is allowed to receive more than anyone else no matter how much they work because it isn't fair that someone has a bigger TV than his neighbor just because he worked harder.

This is implemented through several methods:

1. Orchestrated riots would prevent anyone from speaking out against the "New Idea." Look at Berkley, CA, USA for how that plays out. Hint: rioting to prevent opposing views from being spoken is "free speech."
2. Social peer pressure. Anyone with a fancier car, bigger house, etc. is ostracized. Note that this won't affect the truly wealthy since they just won't care but it will be effective against the low and middle classes.
3. Pay caps to prevent people from getting more by working smarter or being better at a job.
4. Hours worked per week caps. This is in the name of fairness to allow more people to work but prevents someone from getting more by working harder. France has something similar already implemented.
5. UN mandated "reparations" paid from wealthy nations to those who unfairly don't have the wealth. The Carbon tax is a minor example of this.

A lot of nations and groups of people already talk this way. They may even think this way too.

All of these would lead to stagnation. The wealthy would like it because it wouldn't allow anyone to pull themselves up to their level or to replace them.

For the wealthy this is ideal since the poor people will work very hard to keep everyone else poor. It would be like having a bucket of crabs. If you have multiple crabs in a bucket none of them will be able to escape since the other crabs will pull them back in once they start to climb up and out.

• The 20th century was about "What can Americans do". The 21st century has become "What can Americans refuse to do." There is a lot of "you-can't-make-me" going on today that is leading to civilization's decline. – DrSheldon Aug 20 '18 at 18:51
• @DrSheldon, I don't think that's quite it. I think it is more along the lines of "you can't do that because you will make me feel bad." The 21st century seems to be more focused on controlling other people rather than improving oneself. – ShadoCat Aug 20 '18 at 20:58
• There's definitely a lot of that. too. I think your overall premise of politics being our downfall is spot-on. We have no one to blame but ourselves. – DrSheldon Aug 20 '18 at 21:28

A massive EMP (perhaps from a supernova) fries all electronics (except some deep buried military hardware, some mines perhaps). No computers, no pre circa 1970s cars working, no working electronic locks et.c. With the entire IT sector erased and all the electronic records gone the economy collapses into a bartering economy. In hospitals all advanced machines stop working. No patient records, no possibility to make anything but the most basic medicine as the pharmaceutical factories are also computer controlled. Accept for some old phone lines and older radios communication is back to snail mail.

• Not particularly likely to drop GDP per capita, nor life expectancy. Did you think this answer through? It seems to just be a raw idea, with no meat on the bones. – blaizor Jan 27 '15 at 11:17
• There is a real risk of a Solar Flare causing this kind of scenario, except for a few things: 1) We would rebuild fairly quickly, we will suffer a few years of technological deprivation but that's about it. 2) Medical & government records are still filed on paper for the most part, so a total societal collapse is unlikely to occurr – Robotnik Jan 28 '15 at 9:07
• Interestingly enough, a nearby supernova wouldn't just fry all the electronics, but basically sterilize the earth of life in general. Also, we can live without electronics. Trust me on that. There'd be some issues with the economy and banking at first, but we could get it sorted out within a year, tops. – Ernie Feb 3 '15 at 23:51
• Or perhaps just high solar emissions from our own sun. Or a few high-atmosphere nuclear detonations. Or EMP devices. – Dronz Feb 4 '15 at 6:39

While not as elaborate as some of the others, How about something on the order of the Havenites from David Weber's Honorverse.

Specifically their Basic Living Stipend...

In 1700 PD, the Republic was renamed the "People's Republic of Haven" and used a kind of deceit that transformed the poor sections of society into a welfare state, in which citizens were entitled to a specified standard of living adjusted for inflation known as a Basic Living Stipend. The new head of state became the Hereditary President. A new breed of machine politicians, called Dolist Managers, emerged as kingmakers, being able to deliver the votes of millions of so-called "Dolists" to the candidates (called Legislaturists) of their choosing. Some years later, the deteriorating financial and economic condition of the Republic led to the DuQuesne Plan which expected to use conquest to make up the shortfall. The original Havenite democracy disappeared, and power came to be concentrated within the Legislaturalist families, who established a number of secret police organizations to maintain control over the renamed People's Republic of Haven. The original Havenite Constitution was replaced by a new document which enshrined >Legislaturalist rule. This constitution was the first step of the so-called "DuQuesne Plan", named after the Havenite politician who proposed it. (HH1)

In 1804 PD, the treasury was effectively empty . (HH4) Source:http://honorverse.wikia.com/wiki/Republic_of_Haven

Now, this also translated into schooling -- only, certain pre-approved texts being taught, with limited support for innovations. Additionally, add in the fact that it devolved into something like the French Revolution.

To translate Fiction into psudo-fact,some industrialized country with a large welfare state embarks on a plan similar to the Basic Living Stipend -- granting recipients a guaranteed income. Even though some politicians see the handwriting on the wall, this movement gets entrenched to the point that "The sky is falling" realists get voted out -- and, everybody if they realize it, tends to push it onto the next generation (e.g. it's not going to happen to us...its a future problem).

As this is occurring, there's no incentive to work or study -- why, we're getting our Basic Living Stipend...we don't need to expend extra effort in those areas.

Now, some brilliant mind, figures on the "DuQuesne Plan" -- invade/raid nearby solvent countries and run roughshod over their finances and use that to prop up our pyramid scheme of a government.

Now, if said government had access to modern weapons and a willingness to use them, this might pose an issue with 'removing' them. Plus, modern warfare could create economic, sociological, and economic catastrophes.

True, this might not cause immediate anarchy, but at least it is a 'possibility'...

• I would question that "no incentive to work or study" part. Money isn't the only incentive, you know. There are plenty of people (I'm one) who work even though they have more than enough to live on investment income. Then there are people who train for triathlons even though there's no financial reward. What you would get is something like "The Marching Morons" (to take another SF example), where a relatively few workers support a large population of drones. – jamesqf Jan 29 '15 at 23:02
• Why not? Because humans don't actually work that way. Weber hauls a lot of very backward thinking into his so-called future politics. – Dronz Feb 4 '15 at 6:37

Islamic Nuclear Terrorism

Well, any nuclear terrorism on a decent scale would do, but currently elements of Islam seem the most motivated.

They smuggle nukes into New York, Los Angeles, D.C., London, Paris, Berlin, Moscow, San Francisco, and Beijing, then set them off within minutes of each other.

It kills a lot of people, of course, but, more than that, first world economies are destroyed across the Earth. That cell phone you just bought? It probably depends on a lot of parts made in a lot of places. So do the trucks, ships, and planes that transport those parts. Or parts for power plants. Or food. Now some of those suppliers are gone -- dead. And even for those still alive, nobody knows who owes how much money to whom, because bank records have been destroyed. So how much money do you really have, if you can't show how much you had? Money suddenly means less. Without a basis for trade, the world-wide economy grinds to a halt.

Eventually, starvation starts in a big way. We still have plenty of farmland, but money's lost some of its shine, and you can't really feed a world with barter. And some of the technology used to run farms is dead. And some of the plants have been genetically engineered not to be able to provide the seed for next year's crop... Oh, plenty of people in the farming areas survive -- and a lot more than today do it as farmers, rather than financiers or engineers or programmers or artists.

The Dark Ages are called that because there was poor record keeping, or at least very little record keeping which survived to modern times, so we don't know what was going on in a lot of places for quite a long time. It doesn't necessarily mean that society was very primitive, although the two things will tend to go hand in hand.

It's hard to imagine there being another Dark Age like this: our society might collapse, most people might die, and we might revert to feudalism etc. But i think we'll always record stuff, in a way that future generations could read.

Humanity has collapsed before and will (unfortunately) collapse again. The symptoms before each collapse are: ignorance, superstition, religious fundamentalism, xenophobia, intolerance, and rejection of science. See the following chart which was lifted from Marc Widdowson's lost web site. http://www3.sympatico.ca/n.rieck/docs/dark_age.html

A "dark age" really means an age that is technologically, culturally, civilly, and otherwise underdeveloped relative to what came before it. The destruction of the totality of the knowledge of mankind will do the trick for this. No libraries = no knowledge of the previous scientific accomplishments = no ability to implement new technology. When all the nuclear engineers die, nuclear power ceases to be feasible.

I have an idea for causing a dark age, both literally and figuratively, but it might take a while, like 10 billion years.

For all the accomplishments of humans in your setting, FTL, effective or otherwise, is still not possible, so humans are more or less just stuck in the Sol system. The dark age comes when the sun expends and then completely dims out, causing a massive drop in power output, as I'd imagine a futuristic human race with no access to extra-solar materials would rely on the sun for 80+% of its energy needs.

As the sun dims down, power levels dip down across society, and in such an advanced society, it is sure that their power demands will be many times our current power demands, and so when the power supply goes down, their standard of living, as well as the ability to do good science will diminish greatly.

This is of course assuming, your humans have the ability to survive the sun-expansion phase of the sun dying

• If I understand correctly the sun will turn into a red giant first as it turns from burning hydrogen (which it will run out of having converted most of it into helium)... to burning helium... @ which point earth will be uninhabitable. That is it will do that BEFORE burning out... or am I missing something? – MER Jan 29 '15 at 6:58

In order to get to a dark age, were technology is virtually non-existent, and society essentially flat lines with worldwide GDP would be almost impossible coming from the context of today.

My thinking is that any doomsday event that would wipe out 80-90% of the population would leave the survivors in a decent position to prosper. Resources would be relatively abundant, and knowledge of technology would also be intact. While most people would be concerned with survival, IE growing food to eat, the technology of food production would not of been forgotten and people would be moving out of food production and into other pursuits rather quickly. The dark ages would be a matter of some years or decades, but would not likely be long enough to effect anyone but the original survivors. Not long enough to be an age.

The series of events that would bring about a dark ages would have to be a catastrophe of such magnitude that society becomes disjointed enough that groups of survivors are not able to regroup for generations. The knowledge of technology of the current age would have to devolve into myth in the minds of the decedents of the survivors in order for a dark age to be. In other words the history of the world would have to be effectively wiped out for a dark age to happen.

I like the peak oil to start the disaster but not particularly to wipe out society enough to go into a dark age. Oil runs out, wars start, the planet depopulates until a point that everyone surviving has enough to eat. One billion people say, or even a few hundred million only. The technology would still be relatively intact and the remaining population would be able to get it back together enough were a long dark age does not seem likely. Add pandemic to that that wipes out 80-90% of survivors, then you have conditions for a very long dark age. A few tens of millions of people at most in isolated pockets, where technology is lost, central authority is lost and you have a dark age that could be resilient for a few centuries.

Perpetual Nuclear Wars

But not the way you think. Forget the Fallout post-apocalyptic romance, the nightmarish picture of a nuclear winter may very well be just a scary story forced upon us by a bunch of people who used their authority to discourage the leaders from using nukes. After all we've conducted more than two thousands of nuclear explosions and the world keeps spinning on without giant two headed frogs eating cancerous children in Nevada's swamps.

No, the truth is far less nightmarish, but far more scarier because of how realistic it is:

It's 2014-2026, proxy wars are back and bloodier than ever so USA and Russia go to war(or rather a small clash of interests) with each other over a dispute somewhere in Easter Europe or Middle East. Things go sour and tactical nukes hit the floor. The World takes a break for a month of heated debates whether they should stop it right here right now, however UN Security Council is such a joke by now that it fails one last time as hipocrisy and warmongering take the better of world leaders and the war escalates.

After a year of full scale conflicts raging on mostly conventionally with some tactical nuking sprinkled over the most heated areas, one of the sides starts to lose the war(most likely Russia) and has to either accept the defeat and eternal blame or go strategical.

Shit hits the fan, nukes fly across the ocean, military bases and industrial centers are ruined. But that's it.

Most of the civillian populations survive since it's not the real goal of a nuclear war to destroy enemy civillization. Both NATO and Russia/China are in ruins in terms of industrial capacities and economic stability following nuclear exchange, their populations are discontent with the former governments to the point of collapsing into a confederations of smaller independent states that represent little to no authority on the world arena.

The rest of the world is pretty unscathed except for the fact that the international trade is screwed over with the currency crisis and informational infrastructure collapsing for a time being. Slowly(several years?) the world goes back to what it was before.

Only problem is that it wasn't the best of places right before WW3 broke out and bad lessons were learnt out of it:

• turns out nukes don't represent global threat after all - it's safe to bomb your opponent.
• intergovernmental organization formed in place of UN is a faint shadow of what LoN and UN used to be without strong states to back it up sicne there're no victors.
• blatant lies and hipocrisy combined with overwhelming impudence backed by military might make right.
• the bright minds that used to work on the solution for global problems leak to the nowFirst World countries, however they're tasked with the development of less noble tech: Nuclear weapons, ICBMs and Military satelites.

This is a very nasty combo that perpetuates itself:

• Everyone is for himself since there's no international trade
• There's noone to oversee the nuclear weapon proliferation
• There's no authority to stop the kids from misbehaving

Security alliances akin NATO/Warsaw Pact are formed but there's nothing stopping them from going to war with each other over silly disputes. Eventually shit hits the fan again and nukes go tactical and then strategical. The title of First World countries shifts again to other states and the cycle repeats itself howmany times you want.

Humanity enters the 22nd century with 11 billion pops as predicted and global warming causing the desertification of most arrable lands to fee.. star.. motivate them. AK-47 and Toyota Hilux are the pinacle of human engineering thought while nuclear weapons finnaly become Lost tech with no industrial or scientific background to be built upon.

And yes hungry migrating tribes of Slavs invade Switzerland somewhere around 2089-2091 to fulfill your last requirement inspired by the myths of a land of plenty that no war has ever touched.

All states are failing

A viable way to enter a persistent global dark age is to let all states, and therefore all economies fail. This is my second answer on this site based on the book Why Nations Fail.

So, image the world economy contiues its path on political and economic extraction, i.e. political power and economic opportunities are controlled by an elite minority.

For this to lead to a dark age, all inclusive nations, especially the developed ones, need to fail. This, however, might be plausibly possible if several trends are allowed to grow unchecked:

• Unfair global trade, which impoverishes poor countries for the gain of the rich ones. This will make the world economy very vulnerable, if something was to happen to the few rich countries.
• Big money corrupts democracies, elections gradually evolve into a monetary war of attrition between the major political groups, making democratic regimes less and less inclusive and democratically functioning.
• Big money corrupts judicial systems, when the rich can buy their way out of jail, then democracies are further weakened and a path to absolutism becomes more likely. Think of the world financial crisis which started in 2007/2008, there was a lot of criminal activity involved in the build-up, yet little to no-one was put in jail.
• Autokratic and absolutist regimes become more and more isolationist to consolidate their own power, as in better to rule over beggars than to loose power. There are plenty examples of this happening in world history
• Developed countries become economically more and more interdependent. The global economy becomes more and more monopolized. If the global economy depends on a small number of very centralized hubs, taking out some of these hubs may have large implications, think of the oil price shocks, or the more recent hard disk shortage.
• Let the world economy become less and less diverse, in terms of companies/competitors. If a sector is dominated by a monopoly, then that whole sector dies, if the monopolist was to vansish.
• Let the world economy become less and less diverse, in terms of technologies. Again, with the dominance of big monopolists providing everything you need, there is little incentive for people to come up with their own solutions. However, if something was to happen to the monopolist, all is gone.
• Enter the political strongman, an economy under an autocratic regime may be ordered to grow, however, sustainable growth seldomly can be decreed, think of the Great Leap Forward

Over time, in this scenario, the world economy becomes more and more extractive. The rich elite extracts wealth from the poor, and this elite becomes smaller and smaller over time. The elite itself becomes unstable as there is astronomical wealth to gain from being this very elite. So infighting within the elite sets in over the political and economical control. If all high-tech is bundled in the few countries of the rich elite, then all high-tech goes away as soon as the rich countries tear themselves apart in internal or external wars. With a very high degree of centralization, the global economy becomes very vulnerable to crises.

tldr; Apply how colonialism impoverished, and still impoverishes, large parts of Africa and Asia to the whole world; with ruthless, monopolistic, unchecked capitalism taking the part of colonialism. Add time, and the world economy is screwed.