I have floating islands with varying levels of technology that can be allowed on them, usually based on height. One of these islands has tiny microbe/bacterium that allows for food crops to be grown at a reliable rate on these islands but at a cost. It's a green goo (alternative to grey goo in which tiny nanites attack electrical applications). It relentlessly targets electrical applications (completely ignores bio electricity). Creating a vacuum or sealing away a computer offers no resistance due to handwavium reasons. Basically, if it detects an electricity in a certain way, it's going to attack it. When attacking an electrical application, it reproduces rapidly spreading like a cancer and dissolving the wiring and metal frame of whatever its spreading on. The effects are almost immediate as well.

Yet at the same time it allows things like vehicles, tanks, aircraft, basic electromechanical computers/machines and small-scale electronics to work. Most of these are things that will utilize electricity in some way, but often through a battery. As such their use time is limited and dependent of batteries. In a sense electrical technology is grounded to that of the 1940s or even worse in some areas in terms of portability (vehicles count as portable in this sense).

What should my green goo target to disable electrical infrastructure but allow smaller scale electronics?

The goal is to have an island where power generation isn't feasible, especially for large scale devices. Things like large factories, long distance power cables, radio towers etc do not work. But something simple that can be run off a battery works. The absolute max for a battery is the size of a car or airplane battery.

There exists more modern technology on other islands, but if they bring that technology down to the island that requires electricity in any capacity more than a battery, then the system bricks and the green goo attacks the machine.

Some notes:

  1. Integrated circuits do not work on the island except for aircraft flying at reasonable height and speed. Airships mounting a modern computer will short out/be infected by default. This isn't part of the scope of the question. It's already been taken care of. So IC's and semiconductors can be ignored.
  2. The green goo dies the moment it leaves the confines of the islands. Think of the area of effect as a dome.
  3. All wireless communications on the island are jammed past a short distance due to the microbe/green goo
  4. Bio electricity is completely unharmed.
  5. Chaining multiple batteries together should cause issues/isn't allowed.

4 Answers 4


It is attracted to high voltage ELF radiation

Every individual appliance in a normal American household operates at 120v or less. A lot of light duty industrial equipment like welders, mills, etc. operate at 240v. However, the electrical lines used to distribute power operate at up to 380,000v. Lower voltage lines lose power more quickly than high voltage lines; they are also smaller and cheaper to make (for how much energy they can transfer), so if you want to have a central power plant that can distribute power to a whole city without being grossly inefficient, it needs to use high voltage power lines.

Not only is it much more expensive to use low voltage lines, but if you don't, literally all of your power will be lost to resistance after just a few km which would make getting power in remote places especially difficult.

So, if your green goo is attracted to the the EM radiation created by voltages in excess of ~240v, then you will make centralized power plants and radio towers impossible, but local generators, batteries, and a wide range of personal and industrial equipment will still be doable. If they target 120v or more, you will also disable most industrial equipment and generators. If you target 12v or more, then you also disable many household appliances like air conditioners and washing machines, and ethernet wires making both wired and wireless communication virtually impossible. If you target 5v or more, then most hand held power tools, flash lights, etc. will be disabled too leaving you with little more than pocket calculators and cellphones... though the cell phones will only work in "offline" mode because you wont have functioning radio towers; so, it is more accurate to say that you could still have tiny cellphone sized tablets, not actual cellphones.

No need to handwave this part:

Creating a vacuum or sealing away a computer offers no resistance due to handwavium reasons.

High voltage powerlines emit extremely low frequency, high energy radio waves. A general rule for radiation is that the lower the frequency and the higher the energy, the further a signal can penetrate through insulating materials. While the frequency of these radio waves is thought to be too low to be harmful, it is virtually impossible to insulate against.

What about direct current?

The ELF radiation I am describing is caused by alternating currents at ~60 Hz meaning that your green goo could be made to attack any AC circuit if the amplitude of radiation (derived from your voltage) is high enough. But stable DC currents do not generate ELF radiation; so, you could in theory have a higher voltage DC current that the green goo will ignore. So, if you cap it at 12v AC currents, then you may still in theory have a 120v DC powerline somewhere. But it has its limits:

  • Generators create AC power as a function of how they work. So, the green goo would still attack a high voltage generator, even if you are transporting the power via DC. So, high voltage batteries would work fine, for select purposes, but this is a huge logistical limitation.
  • DC is much less efficient to convert between high and low voltages meaning even if you produce power offsite, and tried running it in over long distances at higher voltages, a lot of inefficiency would happen trying to drop it to usably low voltages.
  • Changing the voltage of a DC current produces ELF radiation; so, the powerlines may work fine, but step down transformers will still be attacked by the green goo. So you can only transfer power onto the island using low-voltage power lines. Depending on how far the exclusion zone is, this will make this somewhere between very expensive and only accessible near shorelines and completely impossible.
  • A lot of high powered equipment by its very nature creates ELF radiation so, just because you can power a high energy radio tower or arc welder does not mean that the thing itself wont be attacked.

In short, DC power will probably let you sneak above the threshold here and there for minor things, but not completely give you free reign to go over it.

  • 3
    $\begingroup$ Everything in a normal household operates at 120v or less Wrong! First of all Europe, Asia, etc. are (varies by country) mostly in the 220V - 250V range for household electricity. But the US is actually a 240V country too! Just split in most homes and offices into two 120V branches - which add up to 240V for clothes dryers, water heaters, HVAC equipment, ovens, cooktops, etc. See this video for an explanation. But everything else is good - use 300V as a cutoff and you eliminate transmission (including most neighborhood lines) and industrial $\endgroup$ Dec 7, 2022 at 23:01
  • $\begingroup$ equipment and other big stuff while still allowing individuals to set up a small generator and use their stuff. $\endgroup$ Dec 7, 2022 at 23:02
  • 1
    $\begingroup$ @manassehkatz-Moving2Codidact Good point on European vs American outlets. That said, your second point is the reason I said that 120v cap would disable most generators. My point is that no individual household appliance requires >120v so with minimal adaptation of power sources, (like separate solar/battery power for each appliance), you could keep everything under 120v. $\endgroup$
    – Nosajimiki
    Dec 7, 2022 at 23:13
  • $\begingroup$ @Nosajimiki This kind of depends on what you mean by a household appliance. It’s not unusual even in the US for an electric range or a clothes-dryer to be a 240V appliance (and often use a NEMA 14 or older NEMA 10 outlet as a result), and there are quite a few luxury items (such as hot-tubs or some tanning beds) that are as well (though those typically get hard-wired in). $\endgroup$ Dec 7, 2022 at 23:29
  • 2
    $\begingroup$ Your claim that DC doesn't travel as far as AC is just flat-out wrong, to the point that I'm not even sure how to explain why it's wrong because I can't see how you arrived at that conclusion. What gave you the impression that DC is somehow range-limited? $\endgroup$
    – Hearth
    Dec 8, 2022 at 4:38

Your creature isn't making a decision per-se to leave cars and small electronics alone (etc.), it simply doesn't notice them any more than we notice moderate humidity

I want to expand on @Nosajimiki's answer. I upvoted it and you should too! His answer focuses on how the creature might detect electricity. His answer gave me an idea, the result is a Frame Challenge.

You don't mention the intelligence of the goo. My challenge is that if the goo has animal intelligence, then it won't be attracted to electrical production that doesn't feed or threaten it. Too much work! Not enough benefit! If it has human or better intelligence, it still won't be wasting its time on the small stuff (unless it's a bit psychopathic...). Too much work! Not enough benefit! Humans notice rain, but we don't notice moderate or lower humidity. Both are "water in the atmosphere," but one is too much work to notice while the other is pretty much impossible not to notice. I challenge that your creature is no different when it comes to noticing electricity. It might notice an operating computer or car, but it won't care.

The people of your world can take advantage of this aspect of the goo's nature by keeping electrical generation distributed and electrical consumption separated. For example, a single desktop computer is operated with a solar panel. No more than X number of computers are allowed to operate in the same room or building at one time (each with their own solar panel). Thus, there is no single point of power generation that will draw the goo's notice and not a large enough nexus of consumption that can do the same (call such a nexus a "blood trail" that the goo might follow to find its source).

In other words, what your people discover is that if they spread out electrical generation and consumption, its use becomes small increases over the general background hum of life that the goo simply doesn't notice.

Unless there's a bolt of lightni... Squirrel!

And that's when Lieutenant Rosario had a brilliant idea! The goo could be distracted by lightning in a jar! Enough energy to distract the creature from all surrounding use while it's packed up and moved away but not enough to drain the government's coffers. The glass thickness is rated to give thirty minutes' time to haul butt somewhere else. Lieutenant Rosario, now Major Rosario, now leads the government's efforts to improve the grenade by souring the electricity to sicken the goo.


It Won't Work That Way

Large scale electrical supply is actually more robust, not less. If you can have a battery of any size and not have it eaten by your green goo, then you can have a generator. A generator is basically just a bunch of copper wires wrapped around a magnet. The transmission lines are just copper wires. A motor is similar. There is nothing in the large-scale infrastructure that could be susceptible while small stuff like batteries and electronic devices would survive.

The very worst one could imagine is that certain types of insulator or transformer oil might need replacement. You could make the insulators out of whatever works for the outside of batteries. You could make the transformer oil out of something else, since there are a huge variety of substances that are possible for such use.

So there might be a period of disruption when the goo first shows up. House wiring insulation might all degrade producing a massive number of house fires. But that is easy to retrofit, since there are huge numbers of materials that will function as insulation for house wires. It happens to mostly be PVC and similar right now, but that's down to it being cheap and convenient and long-lasting. Materials like shellac and paper have been used.

  • $\begingroup$ @JBH How many times in your life have you replaced a battery? How many times has there been a power failure over the entirety of the Eastern seaboard? And did it require replacing the infrastructure or just a re-start? $\endgroup$
    – Boba Fit
    Dec 7, 2022 at 16:10
  • $\begingroup$ There is one issue you should consider... while it's true that there is nothing fundamentally different about high voltage devices, they're often expensive and with absurdly long lead times. If someone blows up one of the big transformers and the one spare they have on hand, it can be as long as 24 months before a new one can be manufactured and delivered. And those are pre-pandemic-supply-chain-issues times. If the green goo is endemic and pervasive, then it can easily ruin substations as quickly as they can come back online. This of course wouldn't threaten battery-powered ICs though. $\endgroup$
    – John O
    Dec 7, 2022 at 16:53

It should target electrical infrastructure, but leave smaller scale electronics.

If you have some sort of mega advanced bug that is intentionally destroying a tech level, just have it be smart enough to destroy that tech level. It doesn't need to target anything tech wise, which could be replaced. It can just target size.

  • 1
    $\begingroup$ So it will eat cars but not car batteries? Pole transformers outside houses but not battery chargers? That's a big ask for a goo. $\endgroup$
    – Boba Fit
    Dec 7, 2022 at 15:27
  • $\begingroup$ If it has enough mass, it can have a brain bigger than a human's. It's a living nanite variant, it can be smart. $\endgroup$
    – Nepene Nep
    Dec 7, 2022 at 17:34
  • $\begingroup$ The premise seems to be that it's an accidental side effect, not intentional, though. Unless maybe it was intentionally engineered to do this by some aliens and the humans know this but it's too useful to turn down. $\endgroup$
    – A. B.
    Dec 8, 2022 at 4:05
  • $\begingroup$ It was said certain levels of technology were allowed on each island, so I would assume it was designed. $\endgroup$
    – Nepene Nep
    Dec 8, 2022 at 9:26

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