Lengthy Explanation of Why I'm Here:

TLDR; "force field" made of electromagnetic radiation.

Recently, I've decided to compile a list of possible technologies available in the 22nd and 23rd centuries, along with explanations and descriptions. I have already come up with names of some of the technologies (mechs, antimatter engines, etc), and have begun to come up with descriptions.

In this list is an entry titled Electromagnetic Shields. When I came up with the idea, it seemed really simple. Have a bunch of "nodes" connected to a quantum supercomputer. The nodes send out electromagnetic waves, and the computer controls the direction, frequency, and amplitude of the waves sent out by each node.

Now attach the nodes to a spacecraft in an irregular lattice arrangement, computationally and uniquely determined by the size and shape of the spacecraft to maximize effectiveness. From the constructive and destructive interference of each electromagnetic wave, assisted by the computer, there now exists an extremely strong (but likely blob-shaped) electromagnetic field, localized to a small region around and away from the spacecraft. Let's call this region of intense electromagnetism the Annihilation Zone (AZ). Note: the AZ exists a distance away from the spacecraft, to minimize any dangers to crew and craft.

Any solid or even liquid matter that enters the AZ will experience an electromagnetic force so strong that the intramolecular intermolecular forces (I apologize for not remembering the correct term) are overcome, and the matter is ruptured into individual molecules and atoms (small clusters where the AZ is weaker), thus removing any danger of impact. Note: this material annihilation as a method of shielding is based loosely on The Ethos Effect by LE Modesitt Jr.

My Question

When I began researching electromagnetism to see if this was in any way possible, I ran into a huge problem. Electromagnetism refers to both radiation (light) and electric and magnetic fields. If I'm emitting either waves or particles, it's light. If I exhibit a field, it's either electric or magnetic. The difference is huge.

If the nodes do emit waves, all I get is a fancy light show, with maybe a bit of radiative heat. If they exhibit fields, they could seriously mess with the spacecraft itself as well as everything inside.

Or at least, that's what I got out of the Wikipedia page. *Awkward silence*

So, does my theory hold up? Would any of it be possible, given that this is between the 22nd and 23rd centuries?

EDIT: I'm not asking about the energy involved or conservation of momentum (that's an entirely different question), only if electromagnetic forces would be radiative or electric/magnetic in this instance.

  • $\begingroup$ Welcome to Worldbuilding, The Eye! If you have a moment, please take the tour and visit the help center to learn more about the site. You may also find Worldbuilding Meta and The Sandbox (both of which require 5 rep to post on) useful. Here is a meta post on the culture and style of Worldbuilding.SE, just to help you understand our scope and methods, and how we do things here. Have fun! $\endgroup$
    – Gryphon
    Commented Aug 13, 2018 at 18:43
  • 3
    $\begingroup$ I've thought about trying to write an answer, but it keeps turning out to be an E&M shortcourse, and I haven't the stamina to try to do that briefly. One comment, though: The particle/wave issue you have is a blind alley. On the scales you're working classical electromagnetic theory is all you need to describe the effects. $\endgroup$
    – Mark Olson
    Commented Aug 13, 2018 at 18:45
  • $\begingroup$ @MarkOlson So, what is the classical electromagnetic theory? Radiation or magnetic/electric? $\endgroup$
    – The Eye
    Commented Aug 13, 2018 at 18:56
  • 2
    $\begingroup$ If you are seriously interested in studying these questions, you could pay a visit to our sister site, Physics Stack Exchange: physics.stackexchange.com/questions/142419/… $\endgroup$
    – b.Lorenz
    Commented Aug 13, 2018 at 19:05
  • 1
    $\begingroup$ @TheEye Could it be that you confuse physics with engineering? If you wish to use a real physical phenomenon in your fiction setting in a science-based way, it is physics which tells you how it works and what can it possibly be capable of. Except if you are satisfied with technobabble explanations: "The Humberman projector invented in 2201 and based on quantum-gravito-electro-pastoro unification theory creates a strong oscillating field capable of destroying all molecules in its AOE!" $\endgroup$
    – b.Lorenz
    Commented Aug 13, 2018 at 19:30

4 Answers 4


I don't think your concept will work

You can not create a "passive" electromagnetic field that makes solid or liquid matter fall apart or evaporate it. This is not how electromagnetic fields work. Most of what you would achieve is probably create problems for your ships computers.

There is an infinite amount of specific energies needed to break certain chemical bonds. While gamma radiation (high energy photons) can break up almost anything they mostly just pass through matter. Interaction is quite unlikely. You need several meters of lead in thickness if you want to make sure that none of the radiation passes through. So simply "more energy" is not really helpful, either.

Also, if you would radiate enough photons to evaporate anything coming towards you would shine like a sun. Unless you are fueled by a sun, I see a problem with this idea.

  • $\begingroup$ I'm not sure what you mean by "passive". Could you explain that? Also, I corrected a mistake in my question: the field ruptures intermolecular, NOT intramolecular bonds. Also, the forces in question are electric/magnetic, not radiative. $\endgroup$
    – The Eye
    Commented Aug 13, 2018 at 19:33
  • 2
    $\begingroup$ You can choose between a static field or an alternating field. A static field will either make your ship an electrical charge or a magnet - not helpful. An alternating field basically means that you radiate electromagnetic waves. That is what photons are. You can have waves of all types of energies, but to be sure to break up all bonds you need a huge spectrum and a huge energy output. You will shine like a sun - even if not in the visual spectrum. The energy required might be xray or gamma radiation, but it is still electromagnetic waves. $\endgroup$ Commented Aug 14, 2018 at 6:37
  • $\begingroup$ That's very helpful. In fact, it's the most helpful thing I've heard yet. Might as well call your answer the best. $\endgroup$
    – The Eye
    Commented Aug 15, 2018 at 1:02

I think the main issue you've failed to consider is momentum. Let's say you have a very fast projectile headed towards your spacecraft. Handwaving away all the physics of this Annihilation Zone, what you've said is that the target dissociates into its component molecules. Great! Except, now you have a very fast cloud of matter headed for your spacecraft. It probably wouldn't have quite the same impact as the solid projectile, but if the forces involved are high enough, the end result for your ship is the same. It's similar to the issue of using nukes to blow up an asteroid headed for Earth- now there's just a bunch of smaller, somewhat more radioactive asteroids headed for Earth.

What you really want to do is deflect these projectiles, and that can be done with EM radiation in a much simpler way- point a laser at it. If you can get a spot on the target hot enough that it starts offgassing into space, that produces thrust, and (assuming that the thrust is not parallel to its velocity vector), the trajectory will change and the projectile will miss.

Of course, then you have to deal with issues of focusing a laser over what may be arbitrarily large distances, but that's outside of my expertise. But compared to the difficulties of using interfering light waves to annihilate molecules, I would think "they invented a gamma ray laser" is pretty low on the handwaving scale.

  • 1
    $\begingroup$ I don't think that this is at all helpful. I'm not asking for a solution to what happens after the matter is turned to dust, only if it CAN be turned to dust in the first place, ignoring energy costs and such since this is a century or two in the future, and we really should have solved that sort of thing already. $\endgroup$
    – The Eye
    Commented Aug 13, 2018 at 19:35
  • $\begingroup$ Fair enough. I was thinking in terms of alternatives that maintain some of the premise, but it certainly doesn't solve your initial problem. $\endgroup$
    – Patrick N
    Commented Aug 13, 2018 at 19:42

To make it work, you should probably have it light-like

I suggest to use a phased array laser weapon.

You clothe the ship in a dense array of laser emitters, and you can direct the beam by adjusting the phase of the emitters, and use the interference of the many emitters to direct the greater part of your power into the incoming projectile.

Surely, you would not see such a clean and full disintegration you have envisioned, but the ionized matter erupting from the nose of te projectile would slow it down. If your laser is strong enough and your targeting systems keen, you might even be able to burn it fully away or cause it to miss.

Surely, in traditional sci-fi terms it would be more a "point-defense cannon" than a "force field", but the net effect is the same: you use computer controlled dynamic EM field to neutralize kinetic threats. And of course you could use invisible wavelengths, so it has a spooky "desintegrating field" effect on the uninitiated.

EDIT: It can work against multiple targets too. As there is no barrel, but a large surface covered in emitters, you can easily have great (and variing) number of independently aimed beams, or have beams switch targets in microsecond.

  • $\begingroup$ Is there a specific reason why electric/magnetic would not work? A phased array laser doesn't seem effective against large objects such as asteroids, or many objects, such as a barrage of space missiles. $\endgroup$
    – The Eye
    Commented Aug 13, 2018 at 20:00
  • $\begingroup$ As I tried to explain. A laser beam is nothing else than a column of electric/magnetic field. You yourself said that you want interference of em waves. There is no such thing as interference of static fields. So having your interfering waves as a directed laser beam means that instead of wasting energy in all directions, you focus it on the target. $\endgroup$
    – b.Lorenz
    Commented Aug 13, 2018 at 20:14
  • $\begingroup$ Then how can you explain wave physics? "Collisions" between peaks and valleys of multiple waves leads to constructive/destructive interference, causing the "sum wave" to be stronger or weaker than its individual waves in certain spots. I once saw a video in which magnetic fields (static waves) were able to cause a huge difference in strength on one side of the magnet vs the other, simply because of how the magnets were oriented. $\endgroup$
    – The Eye
    Commented Aug 13, 2018 at 20:57
  • $\begingroup$ Magnetic fields are not static waves. The term static wave is self-contradictory. The key point in the video is that the magnets are spinning fast. At any one location, there is an oscillating, dynamic fields (because the magnets are moving, the direction and size of the induction vector is variing as their orientation varies relative to the point we are measuring the field in) $\endgroup$
    – b.Lorenz
    Commented Aug 13, 2018 at 21:02
  • $\begingroup$ It only matters that it is spinning because they want levitation. I'm only saying that interference happens. $\endgroup$
    – The Eye
    Commented Aug 13, 2018 at 21:03

I'm going to assume that you're mostly interested in present-day physics. If you put it in the future you might want to assume a new physics that does things that fit your plot and background, and you can just wave your hands and say that it wouldn't make sense to twentieth century physicists.

Then if anybody argues that your physics is impossible and doesn't make sense, just wave your hands and say it isn't supposed to make sense to twentieth century physicists.

But OK, you want to destroy things that might hit your spaceship, or possibly use this shield as a weapon. I want to suggest that if stuff is heading your way, and you break them into tiny particles, they might be even more a problem. They won't punch through your hull the way a slug of metal would. But they are likely to stick. They will stick to your sensors, to your ports, to your hatches. They may do a lot of vacuum welding. If tiny particles get into a place with oxygen they may spontaneously burn.

It might be easier and safer to just move things out of the way. Something starts out with a path that intersects yours. You push it, and it misses you, and you go about your business. If you can do that.

Electric and magnetic fields tend to dissipate over distance more than radiation does. So radiation can be stronger at a distance.

I started to write a description of the various kinds of fields and how they work. Electric fields push or pull, but most things have their charges paired up so you push one nearby charge while you pull another and it tends to cancel out. Magnetic fields act sideways to the velocity of the target. Radiation acts sideways to the direction from you to the target. But....

If something is approaching you and you don't know what it is, you could try to shove it so it misses you, and maybe it breaks into many small dense pointy pieces that hit you anyway. You don't necessarily know how well it will hold its shape.

So maybe the first step should be to spray it with nano-size iron particles, that will tend to stick to it and form an iron shell around it. If you can aim them well enough you could make the target spin so they coat it on all sides. The iron will change the target's momentum some.

Then you hit it with a bunch of charged particles, to give it a nice big charge.

Then you hit it with a linear-polarized laser that has half of each wave blocked. So instead of pushing it sideways first in one direction and then the other, back and forth, it pushes consistently in one direction. If you can do enough of that, you can move it.

Maybe it would be better to put a layer of some insulator that attaches to the iron, so the charges on the target don't move around.

If you don't worry about the target breaking up but you want that.... Use a laser that makes ionizing radiation. X-rays. Maybe a gamma-ray laser. The radiation will knock charges off of things it reaches, and some of those charges will escape into space. So it picks up a net charge. The target gets a lot of heat. Maybe some of the material will melt and then parts of it will evaporate into space. The opposite reaction from the parts leaving will move the mass of it in the opposite direction. Etc.

I don't see anything particularly glamorous about this approach but it's probably the most effective. Maximum result for minimum energy.

Still I do like the idea of the target that's covered with an electric charge. Say it's 20 meters diameter. So you have two masers with 40 meter wavelength, and they are tuned to be 180 degrees out of phase with the same polarization. And you block half of the cycle from each of them.

So you get a mostly consistent force pushing the target sideways.

My formula-picture app is down now, but the graph would look like Force = abs(sin(phi)) where phi is time as fraction of maser frequency.


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