How to make a force field

Force fields want to be two different kinds of thing at the same time. They want the physical presence, fixed location and barrier qualities of matter but somehow at the same time be energy. The nearest natural example is Earth’s own magnetic field which does not operate as a barrier per se but does effectively deflect the impact of the solar wind. Deflecting/diverting energy around an object makes more sense and interestingly that idea also points towards invisibility devices and cloaking devices.

However, the classic force field acts more as a barrier than a system of energy diversion. Not unlike a physical barrier, for dramatic purposes the more a force field is hit by weapons the weaker it gets. Other qualities of fictional force fields include:

  • Transparent but usually partly visible (either glows or glows when touched).
  • Requires power to be maintained.
  • Selectively permeable. Some energy can pass through (e.g. light) and sometimes physical objects can pass through. Sometimes it lets air through but prevents solid objects and sometimes vice-veras. Personal shields in Dune let slow things through for example, whereas shields on hanger-bays in Star Wars let space ships in but stop the air evacuating.
  • Centrally controlled.
  • Has a distinct shape and location. Unlike Earth’s magnetic field (which is everywhere on Earth and dissipates gradually) a force field occupies very defined space.

Arguably, any society that is advanced enough to control gravity has a sufficient understanding and control over fundamental forces that maybe anything is possible. I think I can break down the fictional science of force fields into two basic options.

  • The force field is built using principles of forces and energy beyond our understanding. Of course that raises all sorts of other questions about how the rest of the future technology is more limited.
    • For spherical force fields maybe it is some fundamental force that we aren’t familiar with currently. The force acts at very, very specific distances.
  • The force field is more physical than it looks.

For example, maybe the force field is actually a cloud of many tiny objects. Imagine many microscopic drones that are also computer controlled and fly about along specific routes. Quite how, I don’t know, but tiny computer controlled objects give some of the physicality and selectivity of how force fields appear in science fiction.

Come to think of it, tiny energy emitting drones flying around in fixed positions would also help explain how light sabres work. Light sabres themselves have many of the same issues as force fields to the extent that they would appear to be the same technology.

Skipping back to Star Trek, force fields also (sometimes) stop teleportation. I think that makes sense for any kind of teleportation where essentially the transportation occurs by beaming a person as energy from one place to another.

Finally, maybe the terms ‘force’ and ‘field’ are just misdirection — at least for the space ship style deflector shield style. Maybe your spaceship is just covered with tiny emitters that can fire lasers, particle beams and/or tiny bullets at any incoming objects or beams. The appearance of a distinct layer is an illusion. The force field appears that way because that is the optimal distance at which an incoming beam etc can be intercepted after detection.


9 responses to “How to make a force field”

  1. ISTR a very straightforward explanation of a force field from Isaac Asimov’s “Not Final!” – solid matter consists of atoms held in place by interatomic forces; if you take the atoms away but leave the interatomic forces behind, you’ve got a force field. (How? That detail is left as an exercise for the alert student.)

    I suppose if you’ve got artificial gravity generators, you could set up a shield by creating a zone of intense gravity, so strong that everything crossing it gets decelerated to zero speed in short order… it might even apply a substantial red-shift to any photons that happen to cross it… don’t know how you’d get it to degrade after impacts, though.

    Starships in Traveller could surround themselves with clouds of crystal particles that reflected or absorbed incoming laser or other energy weapons fire – most Traveller stuff has some basis in classic SF, but I don’t recall exactly where that one came from.

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    • a compact gravity field would leave us with a very interesting side-effect: after a while it would accumulate a lot of crap just hanging there in the field, eventually needing to shut down the field to get rid of it. Afaik this hasn’t been described in any story 🙂

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  2. A force field degrading over time would be easy enough to explain if every interaction with it removed some of the energy generating it (and it had a limited power supply). But lots of the things you can imagine wanting to do with a force field (focussing a beam of light or a laser on it, for example) would add energy (maybe not in a useful way, depending on how your force field worked). So maybe the force field doesn’t degrade, but rather overloads.

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    • That’s how Niven and Pournelle’s co-dominium shields worked. They absorbed everything thrown at them until they couldn’t anymore. They then released all the energy at once, inward and outward, with predictably devastating results.


  3. In The Culture novels I think force fields were used for a lot more, like moving and holding thinks. Even as weapons? “Effector fields” if I remember correctly. So they were all the things you describe simultaneously.

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  4. It occurred to me that, if you generated a force field at the base of an object, it might solve one of your other problems, about how to make something hover a little way off the ground.

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  5. Should there be a subcategory for “physics behaves differently for everything inside the field”? Like, the gadget in The Forever War doesn’t just prevent fast-moving things from getting in, like Dune shields do; everyone has to keep moving slowly once they’re in there. I’m sure there are other fictional variations on that theme, since it’s a pretty obvious extrapolation of real phenomena like the refraction of light (i.e. if the speed of light inside medium A is slower enough than its speed in medium B, it’ll go off to one side when crossing the boundary).

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