Once upon a time there was an interstellar kingdom with access to hundreds of planets through wormholes. Geniuses or luck gave them magnetic monopoles. They exist!!! The next bit is somewhat magical so I will handwave it. Purportedly every 110 years on each of the hundreds of planets at X locations a dozen magnetic monopoles are captured. Something tells me X has to be huge. So I want to determine X given a harvest period of nine centuries.

From https://www.orionsarm.com/eg-article/48572566653b6 a bit more fiction on the subject:

Powerful military forces can use this technology to create compact and powerful monopole-catalysis "total conversion" bombs, which is essentially a fusion-total conversion explosive device with more controllability, lethality, and shelf-life than similar antimatter weapons. (Increased lethality comes from much lower production of muons than antimatter devices; which concentrates the energy density of the monopole bomb compared to the "fizzle" of an antimatter device. Controllability comes from doping the fusing plasma with other exotic particles to generate reactions with other side effects, such as axion or Higgs production.)

Related to the above somewhere in https://physics.stackexchange.com/questions/446938/runaway-monopole-catalyzed-baryon-decay#446971 an answer says that a monopole needs to travel through 11 meters of copper to induce proton decay for antimatter and annihilation.

The goal is to disable a starship. As a proxy I am using an aircraft carrier. Since the specs of those are not open to the public, any vessel of similar dimensions will do. According to Wikipedia the existence of magnetic monopoles would mean updating the Maxwell equations. A book of Michio Kaku and other sources say that magnetic monopoles are useful to generate energy. The kingdom is less interested in this. How many magnetic monopoles are needed to disable a decent ship/aircraft carrier? Disable defined as unable to move and otherwise damaged.

Extra comments for Vesper: starships move through plasma engine, propulsion. A monopole would be half of a magnet. https://simple.wikipedia.org/wiki/Magnetic_monopole As I said Maxwell equations would apply with modifications. If you want to get close to ships they are bound to shoot, so some distance is required. Assume range of modern navy ships for sake of argument.

Extra comments: I base the handwave part on https://www.nature.com/articles/305673a0 about capture. I am saying for the sake of argument that the Stanford event gave a dozen magnetic monopoles. And https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.48.1378

About mass: since particle physicists have been looking for magnetic monopoles at higher and higher energies monopoles must be heavier than protons by a large factor. But not enough for a black hole, I hope. Also apparently if you have them, you can create more monopoles by smashing them together which is a high energy event. This is all conjecture of course. According to https://physics.aps.org/articles/v10/s137 magnetic monopoles can be made through heavy ion collisions and in neutron stars. From https://physicstoday.scitation.org/do/10.1063/PT.6.1.20220222a/full/

They’re the hypothetical analogues to electric charges in Maxwell’s equations. In fact, their existence would make the equations more symmetrical:


Most experiments have focused on elementary-particle collisions that could produce monopoles that are point-like particles.


In November 2018 a lead–lead collision experiment at the LHC succeeded in producing a magnetic field with a strength of 1016 T, the strongest ever observed in the universe. MoEDAL has now published its results, and although no magnetic monopoles were observed, the team did exclude the possibility of monopoles with masses smaller than 75 GeV, which is roughly 80 times as large as the mass of the proton.


But point-like and composite monopoles are expected to strongly couple to photons.

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    $\begingroup$ Please elaborate on how do starships move, what a monopole can affect in your reality to hamper that ability, and maybe then some meaningful answer could be provided. PS there was a comment of mine saying "one" that used some also handwaved in assumptions on how do starships move, which was deleted by someone else, so maybe I have just disclosed some real mechanics of those engines-- $\endgroup$
    – Vesper
    Aug 25, 2022 at 11:01
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    $\begingroup$ A magnetic monopole is basically a magnetic charge, just like an electron or a proton is an electric charge; it can be a large magnetic charge, or it can be a minuscule magnetic charge of no importance whatsoever. For example, a small tiny itsy-bitsy electron is an electric monopole, but we are not afraid of such microscopic charges. How big are your magnetic monopoles, and what do you want to do to the hapless aircraft carrier with them? $\endgroup$
    – AlexP
    Aug 25, 2022 at 12:03
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    $\begingroup$ Since, as far as I know, a magnetic monopole could not even consist of normal matter, it would be helpful if you defined how they interact with matter/gravity/and everything else. Also, as another comment mentions, a magnetic monopole is not a defined unit, so asking "how many monopoles" does not really make sense. You would need to define what "1 magnetic monopole" is in standard units. $\endgroup$
    – user91641
    Aug 25, 2022 at 12:26
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    $\begingroup$ What makes you think they would disable them at all? You act as though monopoles just universally disable things from aircraft carriers to starships. $\endgroup$
    – DKNguyen
    Aug 25, 2022 at 13:26
  • $\begingroup$ The article you linked seems to be inaccessible without paying $32. Also, if the result has not been confirmed in almost 40 years since its publication, I dare to say it was probably an error. Both aspects mean we still need you to define the magnetic monopoles in terms that can be evaluated. Currently we know that a magnetic monopole would have a magnetic field of indeterminate strength, but everything else seems to be theoretical/open to anyone's guess. $\endgroup$
    – user91641
    Aug 25, 2022 at 13:49

4 Answers 4


Two Positive Monopoles. Two Negative Monopoles.

I will answer using the fictional magnetic monopoles described in your Orion's arm link.

These particles can be used for an antimatter explosion. The article says they are their own antiparticle which I presume means a positive monopole annihilates with a negative monopole of the same charge strength.

The articles says those guys have a mass of 10E16 $= 10^{17}$ GeV. So shoot a positive and negative monopole together and you get an explosion of $2 \times 10^{17}$ GeV (giga-electron-volt) or $2 \times 10^{26}$ electron-volts. Since one eV is about $1.6 \times 10^{-19}$ Joules, the pair of particles gives off about $3.6 \times 10^{26-19}\simeq 4 \times 10^{7}$ Joules.

This table says that's about 10 kilo of TNT equivalent.

I suspect the Orion's Arm number was chosen on purpose to make that conversion so clean.

So how much TNT do we need to disable an aircraft carrier? For this I refer to the Armor Piercing shells of the main gun of the USS Iowa. The Mark 8 shells have about 20kg of Explosive D. This is chemically related to TNT so we will assume it has the same explosion energy.

Since two monopoles give 10 kg of TNT we only need four monopoles in total. Two positive and two negative.

Remember monopoles are small so will fly straight through the hull and can be aimed to collide inside the enemy spaceship.

The strategy is to launch the 2 positive ones from one spaceship, and the other 2 from another spaceship. Of course those 2 positive monopoles don't want to get near each other, since like charges repel. And the 2 negative ones don't want to get near each other either. But the positive charges want to get near the negative ones and vice versa. The hope is that by aiming correctly you can cancel these two forces and get the particles to collide and annihilate at a single point.

  • $\begingroup$ The figure you mentioned is predicted by grand unified theories. It is not complete fiction. $\endgroup$ Aug 30, 2022 at 12:28
  • $\begingroup$ @TuskyEmonay Do you have a reference for that? I cannot find anything. $\endgroup$
    – Daron
    Aug 30, 2022 at 13:13
  • $\begingroup$ physicstoday.scitation.org/doi/10.1063/1.2337812 $\endgroup$ Aug 30, 2022 at 13:44
  • $\begingroup$ @TuskyEmonay I was off by a factor of ten. You should check my work. $\endgroup$
    – Daron
    Aug 30, 2022 at 14:50
  • $\begingroup$ Ok I will you have a typo by the way twenty where you mean 2 $\endgroup$ Aug 30, 2022 at 14:56

Just The One

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One monopole is enough to wreck any starship. Provided the monopole is large enough, fast enough, or has a strong enough magnetic charge. For example:

(-1) Monopole is launched out of a cannon at high speed. It punches a hole in the starship and space air leaks in a drowns the crew.

(0) Monopole is launched out of a cannon at SUPER high speed. It transfers some kinetic energy to the starship and turns it into particle soup.

(1) Monopole creates a big magnetic field that mucks with the plasma field of the starship engines. Plasma means free electrons so anything that interacts with electrons will give you a bad time.

(2) Monopole mucks with the electrical circuitry of the starship or the electrical circuitry of the people on the starship.

(3) Monopole attracts or repels the metal parts of the starship similar to how a bar magnet works. Either the spaceship sticks to the big monopole or is destroyed when the metal parts are torn from the non metal parts.

Do magnetic monopoles attract metal like this? Well no one has ever seen a magnetic monopole so the answer is up to you!

(4) Monopole is so big and heavy it collapses into a black home and slurps up the starship.

Note all of these can happen with a big enough bar magnet too. For more detailed answers include more details in your question. Like what the heck is a monopole anyway?

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    $\begingroup$ "Space air leaks in" is the best thing I have read all week. $\endgroup$
    – Tom
    Aug 26, 2022 at 1:38
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    $\begingroup$ @benrg It's in the last paragraph. These techniques all work with a big enough bar magnet instead of a monopole. Some of them work with a big enough rock. None of them use essential properties of monopoles. This is appropriate to the question where the author does not say what is a monopole or what are its properties. $\endgroup$
    – Daron
    Aug 26, 2022 at 10:44
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    $\begingroup$ @benrg I am struggling to reconcile the meaning of the two sentences "There is not enough evidence to even be sure that magnetic monopoles exist" and "The physical laws governing magnetic monopoles are known". $\endgroup$
    – Daron
    Aug 26, 2022 at 10:46
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    $\begingroup$ @TuskyEmonay Those quotes are too abstract to be useful to answering the question. Tell us something about monopoles that suggests how or why they can disable an aircraft carrier. Saying they are "hypothetical analogues to electric charges in Maxwell’s equations" does not help. $\endgroup$
    – Daron
    Aug 27, 2022 at 8:15
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    $\begingroup$ @TuskyEmonay I have read the article. It has the same problem as the quotes. It is too abstract. $\endgroup$
    – Daron
    Aug 27, 2022 at 8:37

There Are a Few Ways of Looking at This :

As a Projectile

This use case is : accelerating the monopole at the target as a direct projectile. The mass of the monopole doesn't matter much, because you can jacket the monopole that you would accelerate with your railgun in denser material (such as osmium).

So, how much jacketing do you need to penetrate hull plating?

For projectiles, although it is not precise, Newton's Approximation of projectile penetration is a pretty good starting point. The equation is -

$D \approx L { A \over B}$

Telling that penetration depth is, by and large, dependent only on the length of the projectile, and the projectile's density compared to the target.

So how big a monopole to penetrate the hull?

Resources vary wildly on armor thickness from 1 centimeter of thickness to 7. We'll split the difference and use 3.5 centimeters for our armor plate.

Referring to above equation, and knowing that osmium is 11 grams per cubic centimeter, and steel is about 7 grams per cubic centimeter, a

$0.035 \times {7 \over 11} \approx L = 0.022$. A 2.2 centimeter long, osmium-jacketed magnetic monopole fired in a railgun to any reasonable "high" velocity (a few hundred meters per second is more than sufficient) will penetrate the ship armor.

But who cares about penetration? We want to disable the ship, not put holes in it!

According to Wikipedia, the CVN-65 Enterprise has a beam (width) of 40.5 meters. Assuming 20% of that is structural, and the rest is space; and that the structure is also steel, and also ignoring some important points about spalling, how long a osmium-jacketed monopole is required to punch completely through a broadside out to the other end?

$40.5 \times 0.2 \times {7 \over 11} \approx L = 5.1$

A 5.1 meter long (approx 15 feet long) osmium jacketed magnetic monopole "bullet" would be able to completely punch through the starship broadside.

Well, that's a good start, but we're still just poking holes in the ship, not disabling it . . .

Again referring to Wikipedia, the CVN-65 Enterprise has a broadside cross-section of 342 meters length, and 12 meters height; or 4,104 square meters of broadside.

Sticking with our assumption that 20% of this is infrastructure, and the rest is empty space, and further adding the assumption that only 10% of this infrastructure is critical (hitting it would disable the ship), the chance that any one particular railgun shot would cripple the target ship is -

$100\% \times 20\% \times 10\% = 1 \times 0.2 \times 0.1 = 0.02$. Or, 2%

You can increase your odds, though.

You have two options: you can put more holes in the ship, or put a bigger hole in the ship.

Putting more holes in the ship just keeps stacking probabilities. There is a (100% - 2%) = 98% chance that your first shot will not hit critical infrastructure. But, there is only a $0.98^{100}$ = 13% chance that one hundred shots would all fail to hit something important.

By punching a bigger hole in the ship, you take out more of the silhouette with each osmium jacketed monopole bullet.

Since you are shooting at such a big target, you need a really big hole. The best way to accomplish this would be some sort of fuse-detonation that sends a cloud of expanding osmium shards in a cone, trading off penetration power for damage.

To get an idea : a shot that explodes into a 10 meter (~30 feet) diameter cloud of osmium shrapnel will be 78 square meters of bad... that is still less than 2% of the 4,104 square meter broadside area.

But only tripling that radius to 30 meters increases your chances of hitting something important to 17%

As a Particle Beam

This use case is : turning a stream of monopole particles into a sci-fi chainsaw. The monopole would be the chain, and some high-density jacketing would still be the blade. Although a better metaphor might be a fire hose.

There are specific cutting equations that will give more precise results, but I don't think that level of detail is necessary for this case.

Re-purposing our equations from above, the cutting speed is a fraction of the beam width and mass flow rate. So, a cutting beam 1 centimeters in diameter and pumping out 1,000 "shots" equivalent, from above, per second, will cut <= 1,000 centimeters per second (10 m/s) on broadside cuts.

At that speed, it would take 1.2 seconds to slice a CVN-65 dimensioned spaceship from top to bottom along an exposed broadside, or 34.2 seconds to slice it broadside from front to aft, like a deck cards.

Slices? I've asked for disabling!

Unless you are exploiting some awful design choice, like a failure to create and geographically separate backup systems, each slice still only has a 2% of hitting something important.

However, there are some systems (engines) that are challenging to design enough redundancies for. And, even if there is redundant command, cutting a ship in half while it is maneuvering at 1 gee is going to create some significant trauma. This trauma would be a little bit like disabling the ship, until the crew reorients to the changed situation.

As an Ion Beam

Along the lines of use cases that don't dump your super-exotic substance overboard, is using it as the source for a radiation beam weapon. An ion beam is a little bit like firing a firehose at a target made of screen door material.

Ion beams benefit from the property that most of their energy is deposited at a given depth inside the target material (the Bragg Curve)

Here, the assumption that 80% of the ship, past the hull, is air helps you because the stopping power of air is only 33.9 eV per meter.

I could only find data on aluminum, but at energies of only 250 MeV, your helium ions will penetrate 3.5 centimeters of armor plate.

What good is this?

As with the projectile, any single shot has a tiny (2%) chance of disabling the ship, individually. Your two options remain to pepper the target with many shots, or have a single large-area shot to increase your chances of disabling the ship.

Unlike the monopole projectile, however, you will not be tossing your precious high-energy technology off the ship.

  • $\begingroup$ But how many monopoles do you need to disable the ship? $\endgroup$
    – Daron
    Aug 29, 2022 at 23:58
  • $\begingroup$ In the last part, do you mean that monopoles would stimulate alpha decay? I did not find much about that. $\endgroup$ Aug 30, 2022 at 12:26
  • $\begingroup$ Sorry for the late response. I'm assuming you use the monopoles to accelerate helium ions towards the target. These would be generated by another source (there are plenty of options) $\endgroup$ Oct 18, 2022 at 15:50

Your real question, given in the first paragraph, is how many planets would you need to harvest magnetic monopoles from, not "how many magnetic monopoles would you need to disable a starship - no, aircraft - no, any ship".

You seem to want an answer based on fact and hard science, but your question hinges on a fictitious plot component that can be harvested in a way you made up. Nothing wrong with making things up of course, fiction is needed to make a good fiction story.

Since your question hinges on a fictional mechanic, I propose that the number of planets needed to harvest these is "exactly as large as you want". Your question is simple math: over a period of 9 centuries, harvesting every 110 years, and with a return of 12 monopoles per harvest, that works out to 98.1818 monopoles per planet over 9 centuries. If you want your story to harvest 10 planets, simply claim it takes 981 monopoles to "deactivate" your ship. If you want to harvest 100 planets, claim it takes 9,818 monopoles. In fact, you could claim it takes just 9,000 and the other 800 are being used for various purposes. Either way, you can work forward or backward from here.


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