For plot reasons, I need to cut off a planet from all possible means of conventional electromagnetic communication with the rest of the universe. I would also like a impose a "knockback" on the local civilization's technological progress. The "problem" I've come up with is a Clarke's Law-abiding shell of "stuff" that hangs in the planet's upper troposphere, and generates a planet-wide effect very similar to an electromagnetic pulse but a) without the usual nuclear detonation, and b) the effect is constant, lasting unceasingly for at least a couple centuries.

My questions about this scenario are as follows:

  1. Does the EMP effect being constant/recurring make a difference in terms of what devices it affects/how badly those devices are affected?

  2. What is the absolute height of technology for unshielded electronic devices under such conditions?

  3. Would this have any biological effects, for example interacting/interfering with normal bioelectrical fields?

  4. Does this make the actual process of radio communication within the shell's EMP effect impossible, provided that hardened radio transmitters and receivers could be constructed? If it remains possible, does it reduce range/fidelity, and by how much? Is the effect similar for radar?

Thank you in advance!

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    $\begingroup$ There's a tv series called 'Revolution' that might share your premise $\endgroup$
    – dot_Sp0T
    Aug 21, 2020 at 7:34
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    $\begingroup$ What does open scare quotes knockback close scare quotes actually mean? This is rather important... (And do you truly mean "all" means of electromagnetic communication? Including light? I've never heard of an electromagnetic pulse having any effect on signal flags.) $\endgroup$
    – AlexP
    Aug 21, 2020 at 8:33
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    $\begingroup$ Revolution (yet another interesting series that NBC canned; they have a bad habit of that) was based on the premise of nanomachines 'eating' all electricity, not EMP's. Not quite the same thing. (Oh, and where have I seen that premise before?) $\endgroup$
    – Matthew
    Aug 21, 2020 at 12:57
  • $\begingroup$ For your question, is visible light considered a "conventional electromagnetic communication"? $\endgroup$ Aug 21, 2020 at 14:18
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    $\begingroup$ That's a lot of questions for a site that uses as its primary model one-specific-question/one-best-answer. I counted 6 total questions. The TV series Revolution used nanites to justify a world without electricity. So, other than needing to reduce this to one question, are you looking to simply justify a no-electricity world, or is the reason for the lack actually important? (If you think about it, a lot of stories use something to justify telling the story the author's actually interested in.) $\endgroup$
    – JBH
    Aug 21, 2020 at 15:19

6 Answers 6


Solar flares

Currently our atmosphere is protecting us from a lot of electromagnetic interference. This happens near constantly. Still, a huge solar flare is thought to happen once in a while, able to basically EMP most of the world. Granted, this is much worse for bigger electronics like energy grids.

If you're already inventing "stuff in the atmosphere", I'll be just as easy to imagine a much more active star of less protective atmosphere that lets a global EMP happen near constantly. Stars can have long lasting periods of increased activity, explaining the difference between the technological period before and the absence after. The more active star works even better for your reasons, as this will also cut off communication outside the atmosphere, like sattelites in space. There is only so much protection we can grant electronics before shielding fails.

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    $\begingroup$ I like this one. Coronal mass ejections from an unstable star mean technology dependent on electricity would be, at best, challenging. Even telegraphs. It wouldn't need to be permanent, just frequent enough that the development/redevelopment of the tech would be ridiculously expensive and not cost effective. en.wikipedia.org/wiki/…. $\endgroup$
    – DWKraus
    Aug 21, 2020 at 12:31
  • $\begingroup$ Solar flares do not affect wireless communication. Small pieces of technology are quite safe given reasonable shielding. $\endgroup$ Aug 21, 2020 at 14:17
  • $\begingroup$ @TomášZato-ReinstateMonica I'm confused. It might not affect wireless communication, but that communication starts in transistors and such. It's not something that stands on it's own. And yes smaller pieces aren't affected as easily, but try to make those when all big things are down. $\endgroup$
    – Trioxidane
    Aug 21, 2020 at 14:25

This might end up advancing progress

In answer to your first point (Does the EMP effect being constant/recurring make a difference in terms of what devices it affects/how badly those devices are affected):

It sure does. Under these circumstances, if you run a long wire, it will periodically pick up very strong energy surges (strong enough to damage many kinds of real-world electronic equipment).

Sounds like Free Energy to me!

Skip right past batteries, engines, and whatnot -- string up a clothesline that's long enough, and you get an unending supply of jolts. Voltage too high for your technology? Make the line shorter. Not enough current? Parallel lines.

At this point, depending on how frequent and predictable the pulses are, you're driven toward the development of capacitors, rectifiers (maybe), and possibly flywheels or other mechanical energy-storage techniques. (How do you discover the relationship between electricity and magnetism? Someone leaves a few loops in a long wire, and notices that they jump when a pulse occurs, or a ferrous object under the loop leaps through it.)

This could be an interesting "backfire" story, where an advanced civilization trying to suppress a planet-bound race's progress gets a nasty surprise...

  • $\begingroup$ My thought exactly $\endgroup$ Aug 21, 2020 at 17:18

An EMP is, roughly speaking, a extremely powerful, short lived radio. Where the pulse is strong enough, to induce an electrical current in whatever wiring etc that exists in electrical equipment. (resulting in interference at best, and burning it out at worst)


  1. An EMP can't be continuous, but it can be recurring, set it off every couple minutes, and it's close enough. Other than that, there are no difference between the first or the 100th pulse on how it affects anything.

  2. The impact an EMP has, is dependent on how "fragile" an affected system is. A diesel generator or electric motor already deals with currents at a level that makes it unlikely for an EMP to be powerful enough to have any noticeable effect. However, the same can't be said about any computers/electronics that are used to monitor/run such machinery. This is where the classic trope of old muscle cars being impervious to EMPs, because their all analogue, as opposed to the japanese "Rice-cooker" (It's a Trope, i'll leave it's validity for people to decide on their own)

  3. This is a difficult question, there are no immediate effect on biological matter, however there exist data indicating people people living near high-voltage power lines might be more susceptible to cancer, though no clear evidence, and it might have nothing to do with that at all. So at least no effect in the short run, but maybe over years and decades, though only as statistical data and not that people mutate into zombies or anything like that :)

  4. As stated earlier, an EMP is essentially a radio, so antennae for transmitting and receiving can't be shielded (as that would shield them from the signals they are supposed to get). They can however be made robust enough to endure the EMP waves, with the effect of interference or noise on the line.

  5. Such a system would not really be long term effective, as shielding is essentially just building a Faraday cage around any electronics and then your safe. We don't do that today, because it's extremely unlikely that consumer electronics will be exposed to an EMP, and any such shielding would increase the price, even if just a little.

Any world exposed to frequent EMPs would not be vulnerable to it for very long, rendering the "permanence" of the solution irrelevant.

Sorry about the Wall of Text

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    $\begingroup$ This is exactly backwards. A generator is usually connected to a loooong power distribution line, which will couple strongly with the EMP and induce a powerful surge in the windings of the generator. On the other hand, a small mobile phone does not have any long wires inside, and will couple very weakly with the EMP. Actually a 2 meters long conductor, such as a human, will couple with the EMP much more strongly than a mobile phone; but indeed, too weakly to have any noticeable effect -- unless the EMP is insanely strong, comparable with a military radar a few meters away. $\endgroup$
    – AlexP
    Aug 21, 2020 at 11:29
  • $\begingroup$ @AlexP Note that the phone is also a lot more sensitive. $\endgroup$
    – user253751
    Aug 21, 2020 at 16:06

The effects of EMPs fall off over time. But for your purposes a new pulse every few minutes would be enough - possibly solar powered.

Imagine a world spanning network of alien orbital solar panels soaking up 20% of the sunlight. This reduces the incoming radiation to a tolerable level... But the things maintain their orbital position with some form of very high energy EMP. Each panel only does it every few months - but there are tens of thousands of panels. No two panels fire at the same moment, but it's a constant barrage of EMP.

Edit to add: No impact on biological matter. Tech limit is up to you, steam being trivial, what you won't be able to do is long distance power transmission. Local power generation (say, car alternator) and usage would probably work.


So, if we're just talking about the wavelengths far lower than infrared, then that's easy and does not require EMP:

Volcanic activity fills the upper atmosphere with metal dust

This does not necessary need to suffocate life on the surface. Imagine, for example, that the dust is then taken tu surface via heavy rainfall, thus the air on the surface is clear. This also gives you excuse for huge storms which are related to volcanic activity.

The clouding will prevent messages to be sent via visible light too. What we have is a greyish planet from the outside, that can have livable conditions on the surface. The planet's live may be oriented on taking energy from ion or unreacted particles in the rain rather than sun as we're used to.


Definition of pulse:

a transient variation of a quantity (such as electric current or voltage) whose value is normally constant

From the definition an ElectroMagneticPulse cannot be constant, because if it is constant it is no longer a pulse.

Not being a pulse most of its effects fade away: induced currents and magnetic fields are a consequence of the temporal variation of the fields, according to Maxwell equations. With temporal variation being null, all the derivatives in the equations go to 0.


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