From the TV series Stargate: Atlantis, the title city uses an enormous force field to protect itself from a tsunami. Image copyright MGM.

Absorptive Force Fields
Tech Level: 17
Deflective Force Fields
Tech Level: 17
Structural Support Force Fields
Tech level: 18
Specialty Force Fields
Tech Level: 19

Force fields are one of the most commonplace speculative technologies in modern science fiction, seen on screen in properties like Star Trek, Star Wars, Independence Day, War of the Worlds, Stargate, in novels such as The Mote In God’s Eye by Larry Niven and Jeremy Pournelle and Startide Rising by David Brin, and in video games like Starcraft and Homeworld. However, they are also one of the more unlikely innovations that may emerge from real-world science, at least in the form as they’re usually depicted on screen and elsewhere.

A ‘field of force’ is a term used in real world science to describe how particles act near electromagnetically charged objects. Early writers in the science fiction field, as well as many scriptwriters and directors since, apparently misunderstood these fields of particle influence to be actual physical barriers made up of some conveniently obscure type of energy. This interpretation has become so commonplace that it has supplanted the original definition of the term in popular use.

In most sources, the explanation of how force fields function is usually hand-waved away as being "energy barriers." However, there is the serious question of how energy that acts as a solid wall could work, or would even be possible. There are real-world technologies currently being researched (Electromagnetic Defense Fields and Plasma Shields; links at the end of the article) that share some characteristics of fictional force fields, but come no where near the science fiction staple’s apparent versatility, potency, or ease of use. Powerful and currently unguessed-at ways of manipulating subatomic particles would have to be developed in order to make these technologies comply with the visions seen in science fiction.

For all intents and purposes, science fiction force fields are similar to FTL drives and time travel--they can only exist if the workings of the universe turn out a certain specific way. Because of this, their position on the Tech Level scale is relatively arbitrary. Their starting point (the theoretical breakthroughs that could lead to their development) is placed at Level 16 in order to coincide with their use in space opera civilizations, where they are most frequently seen. Truthfully, though, for all we know the scientific understanding needed to create them could come tomorrow as easily as thousands of years from now, if they’re even possible at all.


Because Force Fields are in large part pure speculation with only a tenuous connection to real-life science, they come in a wild variety of fictional characteristics and effects, dependant much more on the imaginations of writers and special effects engineers than any real physical restraints. However, because certain motifs carry over among many of the scifi books, movies, and TV series, we can infer some things about their operation in general. By employing energy, we know the force fields are made up of particles of some kind, which are somehow held or cycled in place by some unknown means of quantum manipulation. But which particles?

Electron Force Fields: Some sources have particle barriers that seem to carry an electrical charge. This is a popular motif in the force fields used in scifi’s jail cell doors; a character will invariable touch the field, and get a shock which causes him to quickly pull his hand away. This would seem to indicate that electrons might be a good candidate particle. In fact, at least one source, the Traveller RPG, describes their force fields (known in the source material as black globes) as dedicated electron screens. Real-life experiments in using electromagnetic fields and cold plasmas as protective barriers are ongoing; the far-future force fields we see on screen might just be a highly advanced versions of these technologies, augmented by quantum technology we can’t yet guess at.

Photonic Force Fields: A few older mentions of force fields in the Star Wars universe quoted them of being made of photons; the holo-decks of Star Trek fame also seem to create their force-field ‘holograms’ at least partially out of heavily-manipulated photons. There are a number of techniques for manipulating and even slowing down a beam of light; the idea of a free-standing three-dimensional hologram goes back to this idea that large populations of photons can be tamed and sculpted at will. A force field in these sources could in essence be nodes of overlapping and intersecting photons, herded by immensely sophisticated quantum manipulators. How even heavily-concentrated photons could act as a wall-like physical barrier remains unknown.

Graviton Force Fields: The defensive force fields in Star Trek may be created through the manipulation of gravity ("coherent graviton emissions" one character was quoted as saying in one episode when explaining the workings of force fields.) Because gravitons can theoretically bend the fabric of space itself, force fields of this type might be minor discontinuities in space/time. One way to visualize this would be to think of space as water on the surface of a pond, with the force field as a permanent ripple around the ship that holds at a steady distance. The more powerful the force field, the deeper and wider the ripple, and the more effective it would be at deflecting the trajectories of incoming attacks on the pond surface.

This would be keeping with Star Trek’s technological motif of creating warp bubbles and working subspace, both of which also require manipulating space/time as a whole with a high degree of sophistication.


No matter their actual particle make-up, science fiction force fields have some basic characteristics in common.

Units: The device that actually creates the barrier is called either a force field generator, projector, or emitter. It usually (but not always) needs to be free of obstructions between it and where the force field is to be created. Multiple projectors can also apparently be networked together to merge and/or overlap the fields they create, allowing them to protect an object that might be too large for a single generator, such as a spaceship.

Energy Consumption: Force fields require a steady supply of power, usually at what would be considered very high levels for us in the twenty-first century. Unlike a physical barrier that a force field imitates, it must be continually bleeding away particles from its surface and losing energy, which needs to be constantly replenished.

Instant Activation, Deactivation: A force field usually pops into existence within milliseconds of activation. If the power is cut off, the force field almost instantly dissipates. There are some exceptions to this, such as in Stargate: Atlantis, where the city-englobing force field can take up to a minute to erect. Also, in Independence Day, the alien force fields flickered for a few seconds before finally disappearing. But for the most part, force fields are seen as instant-access devices.

Particle Frequency: According to superstring theory, all particles, matter and energy both, have quantum vibrational frequencies. If an accurate physical model, that would mean that all force fields would feature the quantum wavelength and frequency of their component particles. Star Trek in its later incarnations got a lot of tech babble mileage out of this, as battles between ships often became duels of which ship’s weapons frequencies could match their opponent’s shield attenuation first.

Cycle Frequency: In some scifi universes, force fields "cycle," or rotate their component particles through their volume, at very high rates. Even though the fields seem to be static glowing walls, in these sources they are more akin to rapidly flowing rivers of energy particles, constantly looping back on themselves. The force fields used by the Gua’uld in the Stargate universe have been established to have this feature.

Non-Interaction With Matter: Most force fields in scifi, when formed, will be stopped by a physical barrier. It may conform around the barrier, but it won't slice into it or permeate it. For example, if a force field is projected into a ship’s corridor, it will conform to the dimensions of the hallway, but won’t penetrate its walls. Why they would do this is unknown; most force fields wield so much energy that they should be able to easily slice through most matter.

Regeneration Time: If a force field is overwhelmed or dissipated by an outside force, it takes a certain amount of time for it to be able to be used again, at least at its full capacity. For instance, in space combat in Star Trek, Stargate, and other sources, the shields will degrade as they’re repeatedly hit ("70%, 40%, 20%...the aft shield is down!" is a typical character quote) but for some reason, once its down, it can’t just be turned immediately back on again, despite the force field generator itself apparently suffering no damage.

This may be caused by a number of reasons. Force fields may need a minimum amount of power to operate, and need to build up a certain level of charge before it can project again. Or, in the case of absorptive force fields described below, the onboard capacitors which absorb energy from attacks become full and need to discharge, which can take a certain amount of time.

Selective Permeability: Except for the absorptive force fields detailed below, most force fields in science fiction seem to be permeable to certain select phenomena. For example, most force fields in on-screen science fiction allow both visible light and sound to pass through fairly effortlessly. Its acknowledged here that this is done mostly for storytelling purposes; a pure black, silent sphere surrounding a spaceship or base can advance the plot only so far.

Yet, if an actual built-in feature of the field, this does raise some interesting possibilities. Fields might indeed be designed to have selective permeability to certain frequencies of electromagnetic radiation, for example, for the simple reason of the ship being able to use its sensors and communication equipment effectively. Being blind during a battle or other crisis can prove just as dangerous to a vessel as not having a force field at all.

However, if a force field allows visible light to pass through, for example, what is to stop an enemy from using a visible-light laser to attack them? Or an a planet surface, if the characters can talk back and forth through a force field easily, doesn’t that mean that hypersonic weapons could also pass through unimpeded?

Force fields might also have other types of designed vulnerabilities. For example, in the Stargate universe, the personal force shields of the Gua’uld lords had a permeability window based on velocity. They would stop high-velocity projectiles hitting the field, such as a bullet, but would allow low-velocity objects, such as air, food, and the occasional thrown knife, to pass unimpeded.

However, there is one force all energy fields in science fiction seem helpless to block, and that is gravity, either from a natural source or artificially created. The reason for this is unclear, but it seems to be a feature in almost all types of force fields from across the science fiction spectrum, in films, TV series, novels, and video games alike.

Tech Level: 17

Absorptive force fields completely absorb and retain all energy that hits them. The two major examples of this type of force shield are the black globes from the Traveller RPG and the Langston Field from the novel The Mote In God’s Eye by Larry Niven and Jerry Pournelle. Whether a scifi source will have absorptive or deflective force fields (or any force fields at all, for that matter) will depend greatly on how the physical laws of its universe work.

Traveller’s black globes get their name from what they look like in operation. Because they absorb all energy they encounter, including light, any ship using one will appear as a sphere of utter darkness.

All energy absorbed is routed to an array of high-energy capacitors attached to the black globe generator within the ship. With the advanced capacitor and energy-storage technology the Traveller universe has access to, this meant that black-globe-equipped vessels could absorb a truly impressive amount of punishment during battle. However, even they had limits, and when exceeded the capacitors would explode or melt down, often taking the entire ship with them. The system also had the downside of completely blinding all sensors and blocking all communication when on.

In order to avoid these pitfalls, ships with black globe generators often also came equipped with large and highly efficient radiator units on their hulls, used to bleed away the excess energy the force field would accumulate in its capacitors. However, these are useless while the globe was actually active, so in dangerous situations such as combat the crews used a strategy of flickering the globe on and off quickly, hundreds or even thousands of times a second. The ship would still be partially shielded from attacks, and could also bleed away the energy from its capacitors that could possibly destroy it as well. The amount of flicker was usually measured in percentages—30%, 50%, 90% etc, reflecting the amount of time in any given second that it was on-and usually reflected how much of an incoming attack’s energy it would absorb. Flicker strategies also allowed the ship to use sensors and communications, so the ship could still take advantage the black globe without being rendered deaf, dumb, and blind. Used in conjunction with other defensive technologies, flickering black globes proved to be a very effective means of ensuring a ship’s survival in extreme conditions.

The Langston field from Niven and Pournelle’s novel worked in many ways similar to a black globe, except in this case the field itself was the energy capacitor. As the field absorbed energy, it would work itself up the visible spectrum, first appearing a sphere of darkness like a black globe, but then turning red, orange, yellow, and so on up to violet and ultraviolet. The field re-radiates the energy it absorbs along its surface area, but sufficiently potent attacks can overwhelm its re-radiative ability and cause the field to overload. If the field overloads it just shuts down and leaves the ship vulnerable, but in some cases (such as in the Motie-modified ship in the novel) the field may become so overwhelmed that it incinerates the ship within.

Absorptive force field also have the added advantage of completely shielding the ship from most active and passive electromagnetic sensors when on.

Tech Level: 17
The weapons of humanity prove useless against the Martians' deflective force fields. From the 1953 film version of War of the Worlds. Image copyright Paramount Pictures.

These are by far the most common type of force field seen in on-screen science fiction. The force fields seen in Star Trek, Star Wars, Stargate, and many other milieus are deflective barriers, even if the exact details of their effects vary with the source material.

These are somewhat inaccurately named. Though they do act as deflective barriers, they also absorb a certain amount of the energy that they encounter. The percentage of the deflection/absorption rate is variable from source to source, but in general these fields will deflect or re-radiate away much more energy than they absorb. Energy that is not deflected away is absorbed into the system and wears away at the field and/or its generator until the field dissipates.

These fields at times seem to have different deflection/absorption rates, depending on what hits them. For example, in Star Trek, the shields are often depicted as being able to handle hits by energy weapons much more handily that physical impacts, meaning that the force fields absorb a much higher percentage of the energy from kinetic impacts than they do the heat and nuclear radiation of the energy beams that strike them.

Tech Level: 18

Also called Structural Integrity Fields. They are often mentioned on Star Trek, but are also seen in sources as diverse as Iain M. Banks Culture novels and the comic-book version of Iron Man. Basically, these are force fields designed to be integrated and work with normal matter, in order to greatly strengthen and reinforce the latter.

There is some indication that electromagnetic fields can be used to ‘stiffen’ certain metals, but the punishment taken by materials in science fiction far exceeds what that technology could realistically do, indicating that some form of true force field is required. The force field may conform itself over the surface of the object, helping it retain its shape, or it may permeate the quantum structure of the object itself, reinforcing it on a subatomic level.

Either way, it allows materials in science fiction that use such technology to withstand some truly astounding damage, such as when the USS Enterprise can survive a near-hit with a nuclear bomb without its shields, or when Tony Stark’s armor can keep its wearer alive even while being hit by the mountain-shattering blows of the Hulk.

Because of the greater skill and finesse it would take to integrate force fields with matter without seriously deforming or damaging the latter, structural support force fields are considered one tech level higher than projected force fields.

Tech Level: 19

These are force fields that have a much narrower purpose that as a general barrier against external hazards. Some might be designed against one specific type of weapon, other might be used to achieve a certain specific effect. Since this fine-tuning of the exotic particles needed usually takes more technical sophistication, the tech level for them is set higher than other types of force fields.

An example of a specialty force field would include meson screens from the Traveller RPG, which makes the particles in a meson gun decay upon first encountering the field, well away form the ship. The meson screen is a barrier of particles much like a normal force field, but only affects pi neutral mesons. It cannot, for good or ill, effect anything else, but in its source material it uses much less energy than a conventional force field and is actually much more effective against that one specific type of attack.

Cloaking devices from Star Trek and other sources also seem a type of specialty force field. They generate an ‘energy field’ that completely surrounds a ship that seems to only affect photons, bending light around it and rendering the craft invisible.


In The Media:

Star Trek, et al

Star Wars, et al

Stargate, et al

Babylon 5, et al

Independence Day

War of the Worlds (1953 film version)

Traveller RPG, et al

On The Web:

Electromagnetic Defense Fields

Plasma Shields

Article added 11/19/08