Assume that modern day Earth discovers a way to create portals to another planet. Travel between the two planets is fast, safe, and easy.

The way this works is that there are fixed points on earth that corresponds to fixed points on this other planet (dubbed alterearth) where, if one builds a stargate-like device, one will be able to create a tunnel between the two worlds (this only work between our Earth and alterearth so no galaxy spanning human empire yet). Step into the portal on one side and you come out on the other planet.

This of course created a rapid expansion of humans to the new alterearth. Each country that has one of those fixed portal points has expanded around the matching point on the alterearth. Within 10 years after the initial discovery, the alterearth borders have been set with the 39 countries that had those portal points, covering 100% of the alterearth land mass.

Life on alterearth is a lot like life on earth, it has breathable air, land that allows for plants to grow, and the local wildlife is quite similar to Earth wildlife (not 100% the same and nothing is more intelligent then a primate).

There is only really one main difference between Earth and alterearth, the alterearth has a particle dubbed "ridiculousium" by scientists, which fitting to its name acts in really weird ways:

  • ridiculousium is tiny, so tiny that in fact it's impossible for it to interact with pretty much every known material as it passes between every other material's molecules
  • ridiculousium doesn't allow for fire to burn, it's not really clear how but it's impossible for fire to burn when near any ridiculousium particles
    • same goes for explosives as it is basically a rapid ignition
  • ridiculousium is super common and doesn't move; its molecules are everywhere on the planet and they seem to stay in a constant position in regards to the rest of the planet, like floating in that exact spot
    • just to make it clear how much they don't move it's been calculated that every step a person makes he passes through billions^billions of ridiculousium particles
  • Aside from the no fire/explosion thing ridiculousium doesn't seem to affect anything else

Day to day civilian life isn't really affecting by being in a world full of ridiculousium. The only real changes are that all power is produced via clean energy, cars are all electric, and all cooking is done on electric hot plates.

While day to day life isn't that bad off due to ridiculousium being around (one could argue it even helps as it takes away multiple major sources of air pollution), the new colonies there are all still part of their original countries and they all have armies on the alterearth to protect their colonies from other countries there. As the average army pretty much relies on explosives (which don't work on the alterearth) and firearms (which just got the "fire" taken out of them as it's impossible to avoid having a ridiculousium particle in the bullet casing and thus make it a dud) which requires a major retooling in the army side.

The question (at last)

Given this world, what kind weapon will an army supply its soldiers instead of the usual rifle? Remember that, other than the discovery of this portal transport, this is RL modern tech level and the army doesn't have years to wait to develop a solider carried rail\coil gun to use... this has to be something that can be fielded to the troops in a month or two at most.


Just to clear things up if there is not fire (as in flame) ridiculousium will not affect it in any way, it will not affect burning of calories or metabolism in anyway as there is no flame involved.

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    $\begingroup$ Do materials that get hot still glow on this world? Think lightbulbs or hot steel. $\endgroup$ – Polygnome May 25 at 19:59
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    $\begingroup$ Please keep it polite & friendly in the comments everyone. $\endgroup$ – Tim B May 25 at 20:05
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    $\begingroup$ You'd have probably got less pushback if you just said "a god did it and ran away", silly as that might seem. Defining your handwavium carefully seems like a question of its own ;-) I'd have use the Giradoni answer (windarms, instead of firearms) but I see AlexP beat me to that idea... $\endgroup$ – Starfish Prime May 25 at 20:08
  • $\begingroup$ Note many explosives do not evolve ignition in any way, most high explosives and some low explosives should still work. so you still have guns. $\endgroup$ – John May 25 at 23:13
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    $\begingroup$ Out of Curiosity, how exactly do you define as a fire? If it the Oxidization reaction? Or the heat energy? or the visual part you can see? $\endgroup$ – Shadowzee May 27 at 4:44

The obvious answer is "use airguns" (something another poster already mentioned, so I'll probably pop it out of this answer if they end up using it). They scale up OK, are moderately powerful and so on, but you'd need to be pretty tricky with them in order to make things that were man portable and could penetrate modern infantry armour. Combat ranges might decrease significantly.

I'm also assuming that energetic decomposition reactions (like hydrazine or hydrogen peroxide) aren't allowed for thematic reasons, but they aren't burning or oxidising in any sense. If they are allowed, your premise kinda falls over. If they aren't allowed, your explanation of ridiculons also won't fly. I'd delete the latter if I were you!


"Amateurs talk about tactics, but professionals study logistics." - Gen. Robert H. Barrow, USMC

No fire means no internal combustion engines, and no fossil-fuel driven generators. No trucks. No heavy lift aircraft. No rockets to launch your spy, communication or positioning sattelites. The lack of guns pales in comparison to the lack of communications and logistics, which will cause nightmarish headaches in any modern army trying to operate at any kind of scale. Might be a sudden interest in electric trains, with earth-side power stations and huge HVDC interconnects through your portals, and lots of electric recce drones.

On the upside, no fires an no explosions mean you can be as cavalier as you like with the design and construction of batteries and supercapacitors! Suddenly the most stupid and dangerous designs become tame. Who cares about surprise hydrogen leaks anymore! Why, you could build zeppelins... there'll be no flak or SAMs to take them down, and they certainly won't burn up.

I forsee a lot of lithium mining and nuclear power plant construction in your future, combined with laser and coilgun research. Those things will get small enough and light enough and reliable enough in short order, I'm sure.

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    $\begingroup$ the military could switch to electric ground vehicles, many large construction vehicles are electrically driven. $\endgroup$ – John May 25 at 23:17
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    $\begingroup$ +1 for great idea about fire safety becoming a non-issue - they can use all sorts of cheap materials for fabrics, cladding etc that are unsafe or prohibited IRL. $\endgroup$ – KerrAvon2055 May 26 at 0:23
  • $\begingroup$ @John I started to talk about that (see comment about lithium mining; that would be for batteries) but present-day electric vehicles are extremely limited in a number of ways. Construction, for example, is quite a specialist case, in a confined location with ready access to utilities. Electric is the way to go, but building a giant, reliable and highly capable logistics fleet is not a trivial task, even for something as large and single minded as a national miltary. $\endgroup$ – Starfish Prime May 26 at 9:24
  • $\begingroup$ I doubt it could replace everything but just have transport trucks is going to be a huge boost. Japan has electric freight trucks so you can certainly build decent range into them. The army is already trying to build an electric tank AKA the Next-Generation Combat Vehicle, so it can't be that far fetched. $\endgroup$ – John May 26 at 13:31
  • $\begingroup$ @John the current gen electric trucks have short range (<100km on road) and are often hybrids, too. They're aimed at doing short delivery routes in places where charging infrastructure is never far away. We're not going to get an electric tank any time soon unless it has an onboard nuclear reactor or a fossil fuel generator; we simply can't fit a useful enough amount of energy into batteries yet. Give it time, though... $\endgroup$ – Starfish Prime May 26 at 15:52

It is tempting to get into the weeds about ridiculousium but that is not the question. The question is about guns.

The soldiers would use the guns they had on earth.

You needed fire for a black powder musket. Modern weapons don't use black powder. The explosives driving the bullet contain their own oxidizer, and so guns would also work in a vacuum where there can obviously be no fire.

Fires can't burn in the oxygen-free vacuum of space, but guns can shoot. Modern ammunition contains its own oxidizer, a chemical that will trigger the explosion of gunpowder, and thus the firing of a bullet, wherever you are in the universe. No atmospheric oxygen required. The only difference between pulling the trigger on Earth and in space is the shape of the resulting smoke trail. In space, "it would be an expanding sphere of smoke from the tip of the barrel," said Peter Schultz an astronomer at Brown University who researches impact craters. https://www.livescience.com/18588-shoot-gun-space.html

If even having an oxidizer is prohibited, you could use something like nitroglycerin. Heat is not required to detonate nitroglycerin. It is an unstable molecule and a shock will cause it to energetically decompose into more stable forms while releasing a great volume of hot gas.

Thinking further on the mechanism of ridiculousium: its effect could be to prevent interaction of gas molecules. Gases all obey the gas laws regardless of their composition. R molecules do not obey gas laws, but interpose themselves between other gas molecules, preventing interactions and reactions.

Biology is still possible because solubility of gases is unaffected by R which is itself insoluble. Oxygen can dissolve in water, and that is the form in which our bodies use oxygen for oxidative biochemistry.

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    $\begingroup$ Own oxidizer or not it doesn't matter, ridiculousium pass right through the brass casing and stops the explosion from happening so the gun would be noting more then a club in the alterearth $\endgroup$ – cypher May 25 at 20:06
  • $\begingroup$ plenty of prollants don't involve oxygen of any kind, so there are still plenty of propellants you can use. $\endgroup$ – John May 25 at 23:15
  • $\begingroup$ Nitroglycerin ammunition is not an option - it is so sensitive that if a soldier tripped over and a magazine struck the ground then the rounds would detonate and kill them. Further, chambers of firearms are designed to take the pressure of a rapid deflagration, if the propellant is actually an explosive that detonates then the chamber will blow up. $\endgroup$ – KerrAvon2055 May 26 at 0:20
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    $\begingroup$ @KerrAvon2055 - yer killing me. Google up nitroglycerin. It is used as a propellant. You mix it with other stuff. $\endgroup$ – Willk May 26 at 0:48
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    $\begingroup$ @KerrAvon2055 there are plenty of electrically detonated explosives A primer is not necessary. $\endgroup$ – John May 26 at 22:05

You have two paths

(a) High-tech

Non-combustion high-text weapons include lasers, masers, sonic, magnetic (e.g. rail), and air. Probably some others, but those are the biggies off the top of my head. In most cases, getting them to the stopping/killing power of combustion weapons requires boatloads of energy, meaning seriously improved batteries compared to what we have today and the recharging stations that support them.

Air weapons could use springs or compressed air. Probably compressed air as you get multiple shots faster vs. the time to re-cock the whomping strong spring. I doubt these would be useful all that much as the air needed to achieve the same stopping/killing capacity of combustion would require wearing scuba tanks full of compressed air. Impractical.

Non-projectile/short-range weapons would be flame throwers or other chemistry-spewing contrivances.

(b) Low-tech

But the path most likely to be taken first would be the low-tech path. Before combustion we had spears, arrows, and bolts. They were just as effective, they simply didn't have the range of combustion firearms. They also have the advantage of being cheap and reliable.

Frankly, a modern compound short bow is a fearsome weapon - and I can easily see it replacing the rifles quite literally overnight.


Air pressure or spring powered weapons. Cannon replaced by trebuchet. Basically medieval warfare minus fire arrows.

With good electric batteries, you get rail guns, self reloading air rifles (E.g. a battery operated compressor recharges the reservoir.

With superconducting wire you get flux bombs. E.g. a million ampere current in a thousand turn coil shielded in a super conductor cover to confine the flux. Break the wire, and it all turns into heat, and an enormous electro-magnetic pulse.

Explosives store power (energy per unit time) efficiently. Your rate of fire and your range would both be reduced.

For an example of this sort of thing see S. M. Stirling's Emberverse series, starts with "Dies the Fire"

In it, while fire works, but not well, nothing that depends on rapid chemical reactions (explosives) electricity, or pressures higher than a few atmospheres works. Pay attention to how Stirling doesn't explain.

If you are going to work with a particle, you have explain why it stays around the planet, where it came from, how it fits into normal physics, why it doesn't leak back into Earth, what happens if there are flucations in the density....


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