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In the not-too-far-away future during a nuclear winter, one city survived by being sealed under a dome forcefield (?) protecting them from the cold weather and potentially harmful sunrays once the sky cleared up.

Robots with varying degrees of complexity exist in this world, and I don't want them to be able to enter this dome. I thought that the forcefield could be electromagnetic to prevent machines from entering.
But a group of humans that my story follows has to be able to penetrate this dome. So how could I make the field separate the inside from the outside and still allow humans to enter?

The humans that I follow are also bringing in mechanical gear that, in order to further my plot, needs to be rendered useless as they enter.

I am very much open to better scenarios if it proves too difficult to make plausible or is too far fetched. I am a bit unsure if the technology the dome uses fits with the technological level of the city it covers.

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    $\begingroup$ What do you mean by "mechanical gear"? Crowbars, block and tackle, electric winch, gas welding equipment...? $\endgroup$ Feb 8 at 0:29
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    $\begingroup$ Clarification request: (a) the shield won't permit atmosphere below a specific temperature to enter (problem: how to breathe during the winter). (b) the shield won't permit photons having a wavelength shorter than 400nm (problem: vitamin-D deficiency). (c) Nothing robotic can pass through the shield (problem: nothing metal, ceramic, rubber, or plastic can pass, how did the robots get out?). (d) Humans can pass through. (e) Their mechanized equipment is deactivated (problem: nothing electrical can pass unless it's very low-level, like human brains). $\endgroup$
    – JBH
    Feb 8 at 1:54
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    $\begingroup$ Very few cities are self-sufficient at food production. Is this dome hundreds of kilometers across to include the necessary farming areas? $\endgroup$
    – user535733
    Feb 8 at 2:41
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    $\begingroup$ Have you considered just putting metal detectors and security personnel at each entrance? Works for airports, courthouses, government buildings, etc. $\endgroup$ Feb 8 at 14:52
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    $\begingroup$ What level of complexity have the robots ? Are they an advanced AI that can came up with solutions or they are only capable to follow a (more or less complex) program ? In the first case you probably cannot keep them out as they would find a solution (an underground tunnel for example) $\endgroup$
    – Gianluca
    Feb 8 at 16:31

8 Answers 8

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CAPTCHA Palisade

enter image description here

The dome itself does nothing. Only it is hard to find. The directions to get to the dome are based on identifying bridges, cars, traffic, lights. For example "turn left at the traffic lights, go straight ahead until you pass

enter image description here

parked cars, then left under the bridge. . . "

Robots are notoriously bad at following this sort of directions. They always get lost.

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    $\begingroup$ On an ...unrelated note, what is "1 + 3"? $\endgroup$
    – Joachim
    Feb 8 at 16:30
  • $\begingroup$ Smart. But this doesn't solve to electrical gear problem. $\endgroup$ Feb 8 at 17:58
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    $\begingroup$ I have just joined this community from core stack overflow just to give you +1 for this ridiculous answer $\endgroup$
    – Asmoox
    Feb 9 at 10:25
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The forcefield can already solve this

The forcefield is much like what is used in Star Wars by the Gungangs in the movie 'the phantom menace'. It holds anything at bay over a certain speed/pressure, but slower less high pressure like a human or air can still go through.

This forcefield however has an electromagnetic effect against anything that passes through. Anyone with experience with Magnetic Resonance Imaging (MRI) machines can tell you it can be disorientating, nauseating or just plain weird, but it isn't dangerous. However, for anything electronic it is incredibly dangerous. Humans pass through, robots aren't as lucky.

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  • $\begingroup$ Having never seen the phantom menace, that description sounds quite a lot like the way shields work in the Dune universe. Would that be a good comparison? $\endgroup$
    – Hearth
    Feb 9 at 5:31
  • $\begingroup$ I already feel bad for cyborgs of your universe, which includes people with cardiostimulators. $\endgroup$ Feb 9 at 14:19
  • $\begingroup$ @Hearth I'm not familiar with Dune shields, but a quick read shows that this can be how they work. The details can still be done by the author, but something like this seems suitable. $\endgroup$
    – Trioxidane
    Feb 9 at 16:46
  • $\begingroup$ @valisstillwithMonica don't be. They are either happy to be alive or happy to be an awesome cyborg. We all have some limitations that are difficult to overcome. $\endgroup$
    – Trioxidane
    Feb 9 at 16:47
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loki

"The machine would melt you from the inside out. Please move along, sir."


There are robots. The people who built the dome don't want robots getting in. There is a robot Guardianoutside the dome that guards the entrance (which is a bridge, because). The robot Guardian does not let robots through. It does not let anything that might be a robot through. Mechanical gear might be a robot.

The dome is pretty sweet. The Guardian is pretty scary. The humans in your group don't understand how either one works but it is clear that both do, well.

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    $\begingroup$ What colour is the Robot Guardian though? $\endgroup$
    – Daron
    Feb 8 at 12:56
  • $\begingroup$ @Daron - depends on the season. $\endgroup$
    – Willk
    Feb 8 at 13:13
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There's an electromagnetic pulse at each entrance.

This fries any electronics or robots, but leaves humans unharmed. Robots can enter the place physically, but are immediately fried.

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  • $\begingroup$ It's possible to shield a device against an EMP. This might take out the wimpy service droids, but a hardened battlebot would just walk right through it unperturbed. $\endgroup$ Feb 8 at 14:50
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    $\begingroup$ @DarrelHoffman That is a problem. I think a cool solution would be to say that the field passes through solid matter, and so the EMP happens continually while passing through, and originates within the robot, bypassing shielding. As with any security measure, there are likely ways to bypass it, but they may be unknown/impractical. $\endgroup$ Feb 8 at 16:49
  • $\begingroup$ Most things designed to shield against emps have a limited ability to resist it, and will be overwhelmed in time. If a giant warbot with a thick faraday cage skin comes in it'll be fine until the people inside shoot some holes in the cage, but it may well be that most robots in this world aren't build well enough to handle this emp. $\endgroup$
    – Nepene Nep
    Feb 8 at 17:11
  • $\begingroup$ Also, an EMP could damage human nuclei in cells. Just saying. $\endgroup$ Feb 9 at 4:21
  • $\begingroup$ @CarterLang If it's very, very high intensity, maybe, but I'd be more worried about human eyeballs and skin in that case. $\endgroup$
    – wizzwizz4
    Feb 9 at 11:25
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You could have running water at each entrance

i.e. Shower, waterfall. Shorts out any electric gear or bot. Water-proof robots are probably not equipped for land travel, but hey, it's your story!

Also

Long-term ionization

To take out the water-proof bots that got through. Although an electromagnetic pulse (meaning all at once) strong enough to damage electronics would potentially affect human genetics in their cells. But, if the whole inside of the dome was washed with ionized particles at regular intervals, the longer, weaker doses would affect electronics well before humans. The only problems would be

  1. Knowing when to stop,

  2. The water-proof bots would have access to the city for a short, but still substantial period of time.

Technically, whatever you say goes, but I don't know if the logistics would work out. The water would have to be externally drawn, which means it has been under the outside radiation. To draw the water from inside would require a large reservoir. It could work. Your choice.

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    $\begingroup$ Should not be an umbrella or a plastic sheet sufficient to make a robot water proof ? (Assuming they can come up with such solution of course) $\endgroup$
    – Gianluca
    Feb 8 at 16:25
  • $\begingroup$ I'm thinking more like a spray from all sides. $\endgroup$ Feb 9 at 4:19
  • $\begingroup$ A robot does not need to breath. You can wrap up in plastic and it is good. I mean, we have dry suit, water does not seems to be a great deterrent $\endgroup$
    – Gianluca
    Feb 9 at 8:27
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Perhaps all the robots and the equipment require a satellite connection to work, but the dome contains a metal plane or mesh

As long as that sky connection is needed, even a thin layer of conductive material is sufficient to act as a faraday cage, preventing successful connection to the outside world, rendering the robots inert and the gear useless

Rebar is not a tight enough grid (the communication waves must not fit through the gaps), but a tighter grid (like a microwave door) or shell could be explained away by explicit purpose

Perhaps the robots are not entrusted by a larger system with enough intelligence to go around on batteries (and thus enter the dome), require a connection to some Multivax-sized ground unit, simply have no apparent motive and go about their inscrutable tasks ignoring the dome, or were really created by the dome-dwellers, and know to avoid it.

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The shield is active - in the computational sense. There is a field around the city from which information like MRI can be extracted to determine the structure of anything passing through the region. The field can also be ramped up to the point that it destroys something by internal heating. The control over this is detailed. Most likely, by default things get fried. But, if you, a human, approach slowly enough to be identified as human, then the security system fries your equipment, but lets you through. In principle the business end of the security system might be able to supply enough power to break any material into ions.

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strong magnetic field on the ground Powerful magnetic coils powered by cold fusion could essentially repel any robot similar to how maglev rail repel the train, turning it into a brick wall for all robots. If a piece of electronic equipment does get too close, the coil would damage the CPU (Similar to how MRI supermagnets damage hard drive data) which also solves your problem of needing the field to shut down electronics.

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