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The setting is a post-apocalyptic world in the near-future (100-200 years), where remaining humans are living in a few domed cities scattered around the world. The reason for living in the domes, and why people can't survive outside, is an uncontrolled virus that has spread. There are no humans living outside of the domed cities, as they are afraid of catching the virus from infected animals. In addition, anyone that goes outside would be banned from coming back in. What I'm trying to figure out is a reason why the domed cities cannot communicate with each other. Presumably, the main way they could communicate would be through radio waves. So I'm trying to figure out what might prevent that, along with any other feasible methods of communication.

I was thinking maybe they had tried some way to eradicate the virus, which failed but had a side-effect of creating radiation or some sort of interference in the atmosphere. Other possibilities might be that the domes themselves are shielded for some reason and thus either block or interfere with communication. But I'm having trouble coming up with something that sound feasible. There is no magic or fantasy in this setting, so it needs to be fairly reasonable. Also, inside the domes they do have access to fairly advanced technology, so the solution can't be something like lack of knowledge on how to make radios or lack of resources to make one.

thieupepijn
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PrimeEagle
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  • Welcome PrimeEagle, we invite you to take our [tour] and read-up in the [help]] about our ways (as and when you have time, it's quite long). Nice first post, but could you tell us about the minimum distance between cities in this world, it would help to set that parameter. – Escaped dental patient. Mar 11 '21 at 21:25
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    The distance between them would be on the order of thousands of miles. For example, one would be in Europe, one or two in North America, one in Africa, one in Australia, etc. – PrimeEagle Mar 11 '21 at 21:28
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    While not an exact duplicate, https://worldbuilding.stackexchange.com/questions/134358/what-would-make-radio-transmission-unfeasible-on-a-planet seems to cover most of what you are looking for – KerrAvon2055 Mar 11 '21 at 21:41
  • Another question I have is, well, presumably they have technicians and mechanics to maintain the city's systems, do they also have skilled engineers/scientists on-hand? – Escaped dental patient. Mar 11 '21 at 21:50
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    Yes, they would have engineers and scientists. – PrimeEagle Mar 11 '21 at 22:00
  • How is the outside still dangerous, if it killed all the hosts except those in the domes? – JDługosz Mar 11 '21 at 22:28
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    See also If global radio communications systems are disrupted, what is the alternative? and Can radiation block all wireless communications?. This is a popular theme, apparently... I wonder if it has a name, yet. Like "fantasy arms control" for the endless attempts to neuter gunpowder. – Starfish Prime Mar 11 '21 at 22:40
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    @StarfishPrime, it's similar to the way people have their post-apocalypse without anyone having any electricity at all, even though it's hard to see how you'd stop it from being generated somewhere somehow just because of how relatively easy it is. – Keith Morrison Mar 11 '21 at 23:32
  • @JDlugosz, the outside is still dangerous because the virus doesn't affect only humans. There are still animals that carry it outside. – PrimeEagle Mar 12 '21 at 00:04
  • Therefore, there are humans who survive outside who carry the disease - Could you edit with these details also as they might be a vital basis of an answer you might like. – Escaped dental patient. Mar 12 '21 at 00:12
  • There aren't humans outside, though. It's just that nobody is willing to risk going outside because they might catch it from an animal. And anybody going outside would be banned from coming back in, too. – PrimeEagle Mar 12 '21 at 00:27
  • Ok, you'd definitely need to edit the question with that detail - else speculations about wasteland-saboteurs will become an answer. – Escaped dental patient. Mar 12 '21 at 00:30
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    One consideration - a virus that is so specialised it can kill the entire human species outside a dome, raises its own questions. Why a doms, not just a walled or barricaded area? And after most humans outside the domes die, is there some kind of universal animal reservoir that's globally present, in all places, to reinfect from? There are Stack Exchange questions on virii killing the world and how/whether that's feasible. Worth researching. – Stilez Mar 12 '21 at 03:13
  • lack of long distance radio is far easier to achieve than no radio at all, which are you trying to achieve? – John Mar 12 '21 at 06:24
  • @PrimeEagle Long-distance radio is very easy, as long as you have the right frequency ranges and sufficiently powerful transmitters. The ionosphere makes for a natural waveguide. – Hearth Mar 12 '21 at 13:56
  • @KeithMorrison "just because of how relatively easy it is". If the machinery breaks, you need spare parts, and possibly energy to use them (for soldering, as one example), and eventually the spare parts run out in your region. Or the people who know how to fix them die. Or both. Besides, a technological society needs enough people and enough food surplus to allow people to devote themselves to tasks other than bare survival. – RonJohn Mar 12 '21 at 17:10
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    @RonJohn, as long as you have magnets and some conductive wire, you can literally make a crude generator in a cave with a box of scraps. We're talking post-apocalypse, and the number of electric motors out there, which can also be jury-rigged to function as electrical generators, or at least provide parts for dedicated generators, is mind-boggling. Household appliances, vehicles, pumps, they are everywhere. – Keith Morrison Mar 12 '21 at 18:09
  • @KeithMorrison corrosion, and the death of people who know what to do are going to make this useless faster than you think. – RonJohn Mar 13 '21 at 01:42
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    The usual explanation is that someone is deliberately jamming communications so that the dome dwellers don't find out about the other domes. – Matt Timmermans Mar 14 '21 at 01:24
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    @RonJohn, and that's because, despite how useful it's proven to be, and known to be, for several thousand years, the first thing that happens in an apocalypse is everyone forgets how to read? – Keith Morrison Mar 17 '21 at 21:22
  • @KeithMorrison how many printed copies of the Encyclopedia Britannica still exist? They used to be in every respectable and up-and-coming middle-class home. now? LOL no. Middle aged nerds might still have their nerdy college textbooks, but who else? And how many of these books survived? (Why printed books? Because you can read them by candle light.) – RonJohn Mar 18 '21 at 08:04
  • @RonJohn, there are millions of books out there that provide the basic information on a lot of things, from which more advanced things can later be derived. Quite often they are collected in locations that use the esoteric term "libraries". And also offices. Homes. Schools. Universities. Bookstores. Also, knowing how to read typically is associated with knowing how to write, which apparently post apocalyptic people also somehow forget to do. – Keith Morrison Mar 18 '21 at 17:20
  • @KeithMorrison you minimize what "apocalypse" means, and how hard the fight for survival will be by suburbanites and urbanites who have never done more than maybe plant a small backyard garden. It's going to be beyond brutal. – RonJohn Mar 18 '21 at 17:25

15 Answers15

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If you want a more haunting reason, perhaps during the final days countless people all over the world set off repeat distress signals, and ever more computers did the same, those computer cycling through frequencies in an attempt to get an emergency response that will never come — and still are to this day. Being the near future, their power is renewable or has enough fuel to keep going for many decades or more and is still going today, especially since being a emergency situation they're likely running in low power mode.

The sheer amount of interference leaves all radio channels garbled with noise. Because the domes never agreed on frequencies, they can't isolate attempts at actual communication between all the automated signals requesting assistance.

But perhaps if they could ever agree on an exact frequency they could find a way filter out all the background noise. Or if they had a big enough receiver outside of a dome — both of which could be a plot point.

JDługosz
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Riley
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The virus is not biological

The virus is actually many tiny machines (nanites) that are constantly communicating with one another causing a great deal of static across all useful RF bands. This would also help explain how animals can be infected and how the virus had near 100% lethality to people outside the domes when the apocalypse happened.

Additionally if the virus is made of tiny machines it would make sense that the domes may generate interference themselves so the virus can't communicate near the domes

SilverShadow
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    I believe nanites is the term you’re looking for. – Wes Sayeed Mar 12 '21 at 07:35
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    This is the premice of the TV show Revolution (https://www.imdb.com/title/tt2070791/) – bizzehdee Mar 12 '21 at 11:55
  • viruses are basically just very tiny biological machines, the only difference is they don't communicate because they never need to – zackit Mar 12 '21 at 13:59
  • This is actually a really clever idea and may solve all my issues! – PrimeEagle Mar 12 '21 at 14:43
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    @WesSayeed NANOMACHINES, SON! – Captain Man Mar 12 '21 at 16:00
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    Problem: radio signals produced and received by an antenna are related to the length of the antenna. For a given size of antenna, there are frequencies it is utterly unable to generate simply because it's not big or small enough. So there can't be any way for your nanites to cause static across the entire RF spectrum. – Keith Morrison Mar 12 '21 at 16:02
  • As an example, a VLF transmitting antenna may need a wire antenna several kilometers long and requires a large amount of power. The smaller the device, the higher the frequency it has to operate at for the antenna to work; conversely, the longer the wavelength, the larger the transmitter and receiver have to be. – Keith Morrison Mar 12 '21 at 17:05
  • The nanites could build larger structures for longer range communication. – SilverShadow Mar 12 '21 at 17:11
  • @SilverShadow, and what's the magical power source? If you keep adding capabilities, then you've gone from science fiction to fantasy, the only difference being that instead of calling it "magic" you're calling it "nanotechnology". And in any event, that doesn't solve the reception issue. – Keith Morrison Mar 12 '21 at 18:03
  • @KeithMorrison By larger structures I mean buildings that could have independent power sources and be of arbitrary scale. Also to my knowledge right now nanites are effectively science fantasy as is. Or at least self powering self replicating ones. So to use nanites seriously in a setting there is some handwavium that needs to be in place to begin with – SilverShadow Mar 12 '21 at 18:51
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    @KeithMorrison Maybe the nanites could band together to form giant antennas. That'd be pretty cool, and it could establish an ability of them to form bigger structures that might be useful for other things. – Radvylf Programs Mar 12 '21 at 19:04
  • Related: Star Trek: Evolution. https://memory-alpha.fandom.com/wiki/Evolution_(episode) - nanites evolve and almost destroy the ship. OH NO! – WernerCD Mar 12 '21 at 21:39
  • The amount of EM noise it would have to create to actually jam modern DSSS/FHSS/OFDM radio communications would be utterly prohibitive. Jam AM radio? Maybe. Make radio communication itself entirely impractical? No way. Not unless they change our ionosphere. – forest Mar 14 '21 at 00:41
  • @forest : The nanobots could be powered by solar energy, which gives them up to roughly 300 PW of potential jamming power to play with. And they don't need to jam communications at arbitrarily short distances. If the cities are suitably few and far between, then all you need may be to create just enough noise that within a few tens or hundreds of km, it would work okay, but past that point, it becomes garbled to the point of uselessness. – The_Sympathizer Mar 15 '21 at 03:41
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If there's no feasible natural reason, look toward deliberate engineered reasons.

In the time when the domes were being established, existing city states were failing and there would be essentially a big free-for-all war. Someone decided that jamming communications would be a good idea for them, and that system is still going on, or they did something like bomb the ionosphere that's still not cleared up yet.

JDługosz
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    I kind of like the idea of bombing the ionosphere. What kind of bomb would have the desired effect? – PrimeEagle Mar 11 '21 at 23:16
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    @PrimeEagle, an imaginary one. The ionosphere is formed by solar radiation ionizing gasses in the atmosphere, where there are enough electrons briefly knocked free to allow the propagation of radio waves. Increasing the amount of ionized material won't last because ionized gas will neutralize itself quickly. Decreasing it won't work because it's constantly being created by the sun. – Keith Morrison Mar 11 '21 at 23:26
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    What does destroying the ionosphere do to hinder the propagation of longwave radio? The reach of longwave trasmitters depends solely on their power, as longwave signals go around the curvature of the Earth as if it wasn't there. – AlexP Mar 11 '21 at 23:51
  • Longwave radio does seem to make this idea not work as well, unfortunately. – PrimeEagle Mar 12 '21 at 00:29
  • maybe they use some kind of new weapon, radioactive one with hope to eradicate the virus but ended up in failure and making more toxic environment and the radioactive waste makes radio wave kind of distorted and hard to manipulate like now. – encryptoferia Mar 12 '21 at 07:47
  • @encryptoferia "magic" – Starfish Prime Mar 12 '21 at 08:32
  • @encryptoferia and of course, the weapon doesn't even need to have had a passing chance at actually doing something about the virus, just that appear to to someone with enough money to spread it everywhere. – John Dvorak Mar 12 '21 at 08:32
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    @JohnDvorak maybe the virus does not even exist in the first place , the reason people that go out can not come back not because of the virus but the fear that the secret will be spilled. the big bad behind the shadow plot. – encryptoferia Mar 12 '21 at 09:16
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Look to social reasons.

Each dome is isolated, but before isolation the populations will have heard news from primarily, their government. And we know from 2020-21 what governments do in the face of a global infection - they blame each other and claim it's deliberate, or a covert plot of some kind, and shut the borders.

(If they don't, its not implausible that the anarchic mob forces it anyway, either by overwhelming public pressure or by taking control, we saw that, too. That's also much easier to achieve in a smaller and less settled/less stabilised populus as this would be. After that, its fair game for almost any arbitrary rules felt needed for "our protection" or to prevent supposed "spies" reporting.)

Xenophobia is sadly never far away.

Who is likely to control the domes, and what kind of governance will exist? Probably quite strict, and tightly controlled, after all these few domes are all that remains of England. Or Scotland. Or the USA. Or Russia. Or China. Or whatever places existed in your world.

What do people in the domes believe? Others are on a global rampage and plot, and destroyed the world to win. And, apparently they did. Our country is reduced to 4 domes. Theirs... well, they created the virus, they are probably waiting for it to die, to finish the job. (And if it's a unified world, then aliens)

Why on earth would anyone want or even allow radio? It can only contact the enemy who killed the world, and at worst misleads us to believe we are safe when we aren't, or tells them exactly where we are so they can finish the job. Xenophobia is probably also why domes not barricades too.

Give it a few years and some populist leadership, and that will be if not believed then followed rigidly by almost everyone, and not really questioned. Building radios inside is fine, but we dont do anything outside that draws attention. Not even passive listening.

Stilez
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    This is actually a pretty good idea, making it due to political and/or social pressure rather than some scientific reason. This could work. – PrimeEagle Mar 12 '21 at 04:36
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    Societal forces also make a richer basis for a story – Stilez Mar 12 '21 at 06:50
  • Spoiler for Metro: Exodus (for the first 20 minutes only tho)!!!! That's exactly what they do there. A secret cabal of the most powerful faction with aid from several others are purposely jamming the radiowaves around Moscow to not attract any remaining enemies (that's what they tell their few people who know), but more realistically to just keep their people undre control and in the subway ruins. Maybe in OPs world, outside like 200km of their one dome, a cure has been researched, but secret ops from that one dome kill anyone coming close and they keep up the lie – Hobbamok Mar 12 '21 at 08:47
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    @PrimeEagle - Updated, see 2nd paragraph – Stilez Mar 12 '21 at 10:00
  • I thought governments didn't shut the borders in case of a global infection which is why we're still here today. – user253751 Mar 12 '21 at 22:54
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Because every city they thinks it is the last city left

The cities are far apart and, as the OP said, nobody from outside is allowed in. So, in every city the people have no clue that other cities could still exist.

In such situation it is safe to assume that people have much more compelling things to do, rather than "wasting" rare and precious time, resources and energy to build a powerful enough antenna to contact other potential survivors.

Many (short-sighted, but probably the majority) people would think that, even if another city existed, it would be no use for their survival, since it would be impossible to cross the land to trade resources.
Other people would not rule out the possibility of other cities, but (as already stated in other answers) they would fear that the other cities, rather than helpful, would try to attack them and steal their resources.
Add to the mix that the very first city to try to contact other cities through radio would find only silence and soon turn it off (in order to avoid waste of energy and resources for maintenance).

In the end, in every city the cost-benefit of an antenna would be considered disadvantageous (particularly since I think that those cities wouldn't be aisles of plenty), so no city still has tried to contact other cities.

McTroopers
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  • This sounds similar to how today, if given a vote on it most people would probably not want money spent toward SETI. I like it. – PrimeEagle Mar 12 '21 at 22:07
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It's setting you up to be a target.

There are still weapons that will home in on any active radio transmitter. While some hypothesize that there are safety precautions to prevent their attacking their own, no one knows what it is, and besides, it's known that several powers used them so you would need many such unknown precautions.

Safer to not use them. Vastly safer.

Mary
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Failure of repeaters

Satellites and land based repeaters will fail. Some signals will be able to be passively reflected off satellites, but this is sub par compared to using active repeater. This will of course depend on where the satellites are.

Long wave has costs

While lower frequencies/ long wave as 'ground waves' that follow earth curvature will get signal thousands of km. But then the amount of information per unit time is low. A 30 kHz signal is approximately 1.5 kB/sec at best. 4 kB/s is plain telephone voice nominal allocated bandwidth. So one voice transmission per transmitter.

To keep power consumption down the cities would want to use directional antennas, and unless you have dedicated antenna per nearby city, (which would be worth it if they have the resources). Then they could easily miss message from city B if they are aimed at city A. Omni directional transmitters wouldn't have aiming issues but the expense of operating them would could be too high.

Distance

A city could have AM/FM radio stations blasting out music/talk etc. Stuff like FM radio only goes 100 km or so, depending on transmitter power and height. So since there is no way any other city would hear, they don't really count for intercity communications.

Gault Drakkor
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    Radioamateurs have made intercontinental links using signal reflection on the Moon, signal reflection of meteorite trails and so on literally for more than half a century... – AlexP Mar 12 '21 at 03:16
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    Radio amateurs have talked on VHF FM (144-148 MHz) from the continental US to Hawai`i, using tropospheric ducting. I regret that I never tried it myself when I was an active ham. – Codes with Hammer Mar 12 '21 at 14:47
  • In addition to moonbounce and tropospheric ducting, you've got ionospheric reflection (bounce radio signals off ionized air), meteor burst (bounce radio signals off the ion trails of meteors), secondary ionospheric transmission (hit the ionosphere with a sufficiently powerful radio beam, and it generates a copy of the signal), and probably some other methods I'm not aware of. Amateur radio operators have been quite creative in figuring out ways to communicate over long distances. – Mark Mar 12 '21 at 21:22
  • How far apart are these cities? Directional antennas are Not Expensive... unless you have to make them out of recycled farming bots and install them by robot because you can't go outside... but you could just put them inside the dome, unless the dome is made of metal (which blocks radio waves), in which case you're all starving anyway because there's no sunlight. – user253751 Mar 12 '21 at 22:56
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Faraday Cages

Whatever material the domes are made of is opaque at radio wavelengths (even if they are transparent to visible light). Basically no other form of EM radiation has a range much beyond the horizon.

On top of that landlines require maintenance, submarine cables even more so. The only form of long distance communication possible shall be global warning.

The Square-Cube Law
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    The expense in the lunar mirror array is in the placing of the mirror. As it happens, that's already been done; please look up the Lunar Laser Retroreflector kits (still in use!).

    Even with the LLRRs available, they aren't very useful for communication without precision detectors and without anybody expecting someone to bounce a signal off the LLRRs.

     – Codes with Hammer Mar 12 '21 at 14:44
  • @CodeswithHammer agreed, I've just edited to cut that out of my answer. – The Square-Cube Law Mar 12 '21 at 15:12
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I have a few ideas.

Any radio antenna outside the dome would eventually fall into disrepair with nobody going out to fix them and fail. Antennas inside the domes would be attenuated by the dome, which would presumably be built with metal parts to create a Faraday cage as well as just plenty of mass to diminish RF power. Increasing the power to break through could threaten people's health in the dome (as in turning the dome into a virtual microwave oven), interfere with vital equipment (medical equipment, internal radio networks, power distribution, etc.), and perhaps other issues.

There is such a thing as ELF radio communications through the dirt and water. This requires very large antennas, a lot of power, and even then achieves very low data rates. I would think that given the overwhelming desire people have to communicate, and that this problem is not likely to sneak up on people, that plans would be made to maintain these systems even with considerable cost. Cutting people off will be difficult as ELF communications is well documented and anyone able to maintain a city sized dome should be able to build antennas and transceivers. It would take a lot in my mind to get people to abandon this as a means to communicate, even if it was at a data rate measured in bits per hour.

After some thought on this and reading some of the other answers I believe it's just too easy to build an effective ground penetrating radio communications network. Ham radio operators are playing with this kind of equipment now. https://en.wikipedia.org/wiki/2200-meter_band

I'm thinking that people would have to be afraid to transmit anything. I believe a better answer is a combination of what others came up with. Consider a non-biological virus that is attracted to RF energy. Transmitting anything attracts the virus to the source. The early attempts to fight the virus left behind long lasting RF generators in locations far from population centers that pump out RF noise like crazy. These would be powered by solar power, wind, hydro, nuclear batteries, or anything else that they could contrive that could keep going unattended for decades or even centuries. This keeps most, but not all, of the virus around these locations but makes radio communications difficult worldwide.

Even that might not stop people from trying. And succeeding.

There's no people outside the domes to pose a threat, right? So this isn't a case of a zombie apocalypse of people roaming about looking for domes that could provide clothing, shelter, and brains to eat.

We have radio modulation systems that can operate below the noise floor. This makes the radio source difficult to track for intelligent humans, a mindless virus that is attracted to RF energy could be easily fooled with RF noisemakers while radio network can still communicate. Such communication schemes and frequencies are standardized and known by militaries, ham radio operators, airlines, and so on. Someone is gong to know how they work, and for people that don't these things are written down in books.

A virus is not likely to stop people from communicating by radio. A non-biological virus attracted by RF energy isn't likely to either. Can this virus turn people into zombies? Radio wave seeking zombies? Can the RF seeking non-biological virus eat through the dome materials? That might scare people enough to stop trying. Maybe.

MacGuffin
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  • or you build the tower in top of or on the edge of the dome. – John Mar 12 '21 at 20:35
  • @John " or you build the tower in top of or on the edge of the dome. " True, but to access the antenna for maintenance without going outside still leaves the antenna inside some structure. The size of the antenna will be limited by the size of the structure that contains it. HF/SW to ELF antennas need to be big to be efficient, VHF to SHF is easily blocked by walls, EHF and up is easily blocked by air. How big is the dome and what is it made of? Again, there is a power limit due to proximity to people, the radio will be health hazard if too powerful. – MacGuffin Mar 13 '21 at 10:49
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The vast quantity of radio receivers and transmitters on the planet would be decimated by the electromagnetic pulses caused by the detenation of multiple nuclear devices in the atmosphere. Similiarly so would computing devices,networks and all their support structure would be destroyed as well. The land based power sources would be damaged by EMP effects such very high amperage direct current being sent down power transmission line melting transformers triggering massive continental wide power disruptions. Just with that alone. No power to operate the devices no electronic communication whatsoever until such time the infrastructure gets rebuilt. Time frame involved several decades minimum to a century or two. The knowledge to reconstruct radio technology and power sources may be lost. Not all the survivors would be engineers or technicians.

With regard to the ionosperic propagation of radio waves that is controlled by the Sun's radiation effect on the atmosphere and these effects vary depending on frequency and time of day. The time it would take for the infrastructure to rebuilt the radiation effects would long dissapated and as a result interference from fallout would be virtually non existant.

Old_Fossil
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There are no technical reasons that would prevent communication, so you will have to create political ones. A useful subplot might include the consequences of illegal communications between cities.

There was a book series "Silos" by Hugh Howey that included a similar theme. His cites were underground which restricted the communication possibilities in a way that might suit your needs.

Paul Smith
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Communications worked... for a while

First of all, the main communication method would be internet, not radios. After all, to this day everyone is connected to the internet via different methods (incluind radio waves) but most/all of them at some point require a large wire bewteen two points, or a huge antenna communicating with a satellite.

Now, humans had to lock themselves inside huge domes. Ok, they still have communications using all the methods they used before, after all the infrastructure is still there. But for this to keep working it requires maintenance, and after a few decades every communications installation and equipment outside the domes stopped working. Normal decay and zero preventive and corrective maintenance added to the fact of nature taking back its space outside the domes made all wires, antennas, data repeaters, etc. that were out there eventually fail. And who's gonna go to replace a cut wire if it means for them certain death in the worst-case scenario, and eternal exile in the best?

Josh Part
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Somebody stole the ionosphere!

For a few scattered domes to contact each other by radio, they need one of two things: satellite repeaters, or the ionosphere. I will assume the satellites have fallen victim to time, often being deployed low in the sky, or being cryptographically locked up with codes that are long since lost somewhere in the Contaminated Zone. That leaves the ionosphere ... where did it go?

The ionosphere can be considered a little like an immense capacitor. It is hard to say if there are any "serious" proposals for tapping the vast energy that is undoubtedly there, but there are Tesla fans out there (I mean the real Tesla) who will write long essays about Wardenclyffe Tower being some plan to capture the full energy of the entire ionosphere. Occasionally the impact of collapsing the potential on thunderstorms comes up as a separate alleged benefit. Let's not forget the fans of atmospheric heaters such as HAARP while we're at it.

I think I would prefer to suggest tapping the ionosphere by some more recently invented means - using an intense laser system to create a pathway of ionized air, perhaps? If someone can do it, they have solved their full energy requirement, while causing a "sudden ionospheric disturbance" and loss of communications for everyone else. I admit, this is on the fringe of fringe, but there you have it.

Mike Serfas
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    Ionospheric disturbances would not inhibit long distance communications by "moon bounced" signals. https://en.wikipedia.org/wiki/Earth–Moon–Earth_communication People bounce radio waves off the moon quite regularly and before communication satellites were a thing militaries were considering this as a backup to HF radio communications. ELF to LF communications through the Earth would also not be inhibited. Using these means to communicate complicates things but is far from making it impossible. – MacGuffin Mar 15 '21 at 05:00
  • I forgot about that one! But it seems technically difficult with hard to find components, high power and low bandwidth. With no way to tell your listener when and how to listen, will communications ever happen? There are amateur radio buffs who can bounce a signal off a meteor, but will they? I admit, nothing about this idea is airtight. – Mike Serfas Mar 16 '21 at 01:17
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The starting event of this is a geomagnetic flip of the poles. The time for the flip to occur is measured in hundreds of years. Typical scenario is that the poles split into smaller weaker poles that wander around for a few centuries then reconsolidated. The wanderings start decades before -- time to build the domes.

population is determined by how much food can be grown. There is air exchange with the outside, but through sanitization methods. You will have a problem with domes overheating. Greenhouses run an air exchange per minute in summer to keep cool. Possible a double dome with the interior filled with soap suds to reduce heating.

During this time, the earth has no decent magnetic field. Solar wind blasts straight into the atmosphere destroying the ozone layer and radically changing the characteristics of the ionosphere. I don't know that this would make radio impossible, or just erratic.

Aurora would be world wide. Non hardened satellites would be destroyed by solar wind.

Domed cities necessary or protection from UV as well as virus. UV may have caused the virus mutation.

That said, it has to be a tough virus to withstand UV from being outside. Viruses generally don't do well outside a host. Your virus needs a non-human host in the outside world. Mice? Chickadees?

You could also use a persistent bacteria such as anthrax that is viable in the soil for over a decade.

You need a disease that has a non-trivial incubation time. Otherwise a city could have a secondary 'quarantine dome' where people would wait for X days before entering the main dome. (The word quarantine has the same roots as 40. The number of days ships had to wait in harbour in Venice before anyone could come to shore.)

Bigger cities would have staged quarantines. You come into A. After 2 weeks of no sickness you move to B. Two more weeks you move to main.

If the disease has a dormant spore form (anthrax) then people come in naked, shaved (yes there) and bleached.

Sherwood Botsford
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Electrolytic capacitors present in many circuit boards have a short life span (~15-30 years). Once they are gone, the circuit no longer works.

If you lost your industrial capacity, you will not able to build replacement parts and all your electronic devices will become useless.

Electrolytic capacitors is the only practical alternative for high capacitance requirements.

Candid Moe
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    You don't need electrolytics for radio. You can get by with just about any sort of capacitor -- for a spark-gap transmitter, even a Leyden jar will work. – Mark Mar 12 '21 at 21:34
  • But you need electrolytic capacitors for power supplies and for any application requiring high capacitance capacitors, which means almost any electronic circuit. – Candid Moe Mar 12 '21 at 22:46
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    You need electrolytic capacitors for switch-mode power supplies. Switch-mode power supplies are hardly the only way to power electronics. – Mark Mar 12 '21 at 23:13
  • Linear power supplies uses capacitor for filtering and smoothering. – Candid Moe Mar 12 '21 at 23:15
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    Batteries don't. – Mark Mar 12 '21 at 23:16
  • Well, the bottom line is: all your electronics will be dead and you need to restart technology from zero. Sure, you can reconstruct modern day electronic, but it will take a while. – Candid Moe Mar 12 '21 at 23:19
  • @CandidMoe: Propably reverting to forms of communications such as telegragh would fill the communications void on a continent. However intercontinental communications would still be a no go – Old_Fossil Mar 15 '21 at 03:57