Would they be able to even destroy the nanoscopic machines, or would something like an EMP be much more efficient?

The nanites in my setting are programmed to tear apart the human genome of enemy troops. This effectively would mean instant death to anyone they managed to infest.

They have mannerisms similar to a swarm of locusts, like a black cloud of death.

Lots of the technology in my setting uses benevolent nanotech, which would also be affected by an EMP if it was in range of the explosion. Self building skyscrapers, and roadways are just the tip of the iceberg.

The best real-life comparison to the way the nanites affect human DNA is similar to how the amanita bisporegia mushroom affects anything that consumes it. It produces an amatoxin that inhibits the effects of RNA polymerase, essentially stopping transcription of DNA to the various RNAs that are essential for life. Essentially if the DNA simply disappeared from the body, the person would immediately feel the effects such as dizziness, followed by a period of a false recovery. In reality, this false recovery is just the cells accumulating irreparable damage.

After that, tons of horrible symptoms would take place, starting with symptoms like diarrhea, (Since the intestines have ceased to function) nausea, vomiting, and eventually massive organ failure as the vast majority of your cells die almost simultaneously. No amount of medical care could save you from this, unless it was of a magical or divine nature.

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    $\begingroup$ Depends on your nanites, tell us more about them. $\endgroup$ – Separatrix Nov 7 '19 at 14:27
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    $\begingroup$ Where are the nanites with respect to the bomb? My whole city survived unharmed and unaffected the Tzar bomb, just being few thousands kilometers away from its explosion. $\endgroup$ – L.Dutch - Reinstate Monica Nov 7 '19 at 14:34
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    $\begingroup$ is it instant death to have your genome destroyed? People totter around for quite a while after a serious dose of radiation, after all. It also takes time to really burrow through a person and get to the sort of bits of them associated with "instant death". $\endgroup$ – Starfish Prime Nov 7 '19 at 15:09
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    $\begingroup$ In Portuguese there is an idiom, "a cannon shot to kill a fly". You just took it up a notch or a billion. $\endgroup$ – Renan Nov 7 '19 at 15:27
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    $\begingroup$ @StarfishPrime agreed: this isn't 'instant death', it's "Virtually assured, long agonizing death". Gray Goo nanites would be quicker. $\endgroup$ – RonLugge Nov 8 '19 at 0:00

Would they be able to even destroy the nanoscopic machines

Are they nanoscopic? teeny tiny things have a real problem getting around. They certainly won't swarm and fly like locusts; air viscosity at that scale is too high. They'd be blown around, and work more like fatal hay fever than a homing cloud of doom.


Yes, the nuke would work jolly well, if it was close enough. Nanoscale systems have problems shedding heat, so a nuke going off close enough will thoroughly toast them. Without knowing more about your nanomechanisms, I can't tell you how much heat is needed to kill them.

You can have a play with NUKEMAP, a handy tool, which has useful things under its "advanced options" like "Thermal radiation radius (1st degree burns (50%))" which corresponds to a thermal irradiation of 10.46 joules per cm2. That's enough heat to toast the nanoscale replicators that make up the outside layer of your body, at least. For the example 20kt blast I linked, everything within about 4.16km of ground zero will receive at least this much heat.

Nuclear radiation (mostly gamma rays, I suspect, and maybe some neutrons) will also be highly effective, but its range is a) shorter and b) harder to work out the effects of. Neutron bombs will produce less thermal radiation, but at close ranges the intense neutron flux should effectively neutralise nanomechanisms even behind cover that would protect them from merely thermal effects. A 1kt neutron bomb should be effective out to 900m or so, with range sharply reducing against targets in harder cover (like thick concrete walls, though the blast would potentially flatten those).

UV radiation is probably also effective, but I don't know anything about short wavelength EM emitted by a nuclear fireball, so I won't consider that here. You might want to look it up, though.

In any case, thermal, UV or direct exposure to nuclear radiation requires line of sight to the blast. Sheltered nanothingies will be largely safe. If they're engulfed in fire that will probably sort them out though, but you need to be a lot closer to ground zero to have everything catch fire (more like 1.2km) as a lot more energy is required (more like 147J/cm2). In the absense of combustible materials (eg, a very concretey modern city or dry desert) a fire will likely not start and again, sheltered nanomechanisms will likely survive. A strike with multiple warheads with overlapping areas of destruction is probably the best way to ensure that the number of survivors is minimised.

Burying the little things in debris is probably highly effective. They can't hold much power, so they'll become inert before they can escape. On the other hand, those far enough from a nuclear explosion may be distributed more widely by the air blast, making the outbreak harder to deal with.

or would something like an EMP be much more efficient?

EMP will be fairly ineffective, because you need long-ish conductive structures to pick up the electrical fields. Nanomechanisms are so tiny that the voltage difference across them is just too low to do any kind of meaningful damage. Larger devices (microchip sized) can be affected, but generally only because of the metal interconnects they are attached to.

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    $\begingroup$ Just saying that nanocircuitry uses very low voltages as well, and nanowires which can be fried or gapped by 1.5 volts. I wouldn't write off EMP just yet. The semiconductors can be one atom thin. The E1 phase of the nuclear EMP would kill a nanite because it travels slowly (0.9c). $\endgroup$ – Vogon Poet Nov 7 '19 at 22:15
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    $\begingroup$ @VogonPoet, nuclear EMP typically produces electric fields on the order of tens of kilovolts per meter. In order to experience a 1.5 volt induced current from a 50 kV/m pulse, a "nanomachine" would need to be at least 30 micrometers long. $\endgroup$ – Mark Nov 7 '19 at 23:57
  • $\begingroup$ @Mark There are three phases to a nuclear EMP. I am referring to the E1 phase generated by gamma radiation exciting electrons in the atmosphere. $\endgroup$ – Vogon Poet Nov 8 '19 at 0:03
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    $\begingroup$ @VogonPoet, yes, and the E1 phase can't produce a strong enough electric field to do the job, unless the nanomachines are rather large. $\endgroup$ – Mark Nov 8 '19 at 0:21
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    $\begingroup$ Makes me wonder if an effective counter to a nanobot swarm would actually just be militarized versions of those IR heatlamps that restaurants like to use on outdoor patios. Feels nice and toasty for us meatbags. Ramp it up and you'd probably overheat nanobots easily. $\endgroup$ – JamieB Nov 8 '19 at 17:53

I would not hold high hopes on nukes being any good or effective about nanoscale machinery, despite Starfish providing good enough answer as general assumptions.

The reason for that is a possible multitude of deployment tactics. Even with your chosen one "swarm of locusts, like a black cloud of death" there is plenty of options.

Best countermeasures are similar machines, and if another side does not have one - they pretty much are toast.

as a model to think about, a modeling example which may have similar properties as named nanomachines and on the topic of the effectiveness of nukes in the case - it possible to take viral infections(which not exactly visible, but still effective enough) or microorganisms which exists in soil, or general dust present in atmosphere.

To get visible effects of the presence - the nanomachines may be indeed like dust particles - dust like a shell for few nanomachines which they are using as a carrier(like those or similar to particles which are suggested to counter global warming in some studies - those flying high for a long time, and with changing properties introduced by nanite structures in them they can fly as they wish). Then the most of the mass of the stuff will be quite robust and inert material - thus it pointless to imagine them being easily vulnerable by UV, EMP, certain levels of radiation, light burns or air pressure.

They can clump in something bigger - like mosquito size and indeed fly as a cloud of insects instead being delivered by missile or airplane or crawl underground or other less detectable ways of deploying them. But even with mosquito size carriers - which they may collect for the means of keeping communications with base or other necessities - they probably do not have to be a super-dense cloud of the stuff and even if they have for some reason to gather in a visible cloud it not likely to be one super big but many small ones on a distance from each other - so it can be spread of many smaller clouds - which will make certain average density of the machinery in the area which does not have to be high - thus making nukes not so effective as it would be against buildings and humans.

Dust particles of 10um size, in a concentration of around 10mg per cubic meter, are enough to form visibility problems like that Fire smog comparison, Moscow 2010

And if we take 2Mt airburst from nuke map, we can hope for 2.3 km radius cleanup(most likely, but not fully) to 10.3 km radius cleanup(less likely, not fully) 2.3km radius is:

500 rem radiation dose; without medical treatment, there can be expected between 50% and 90% mortality from acute effects alone.

So it is not an immediate hell of fire cleanup, it just some percentage of cells in a big body are destroyed enough to malfunction - but it does not mean all of them are destroyed - soo the same for the nanomachines - it won't be 100% cleanup of a territory.

50m height and that smog density of 10mg/m3, and 2.3 radus (4.6km diameter) of those nanites loss will be about 8 ton of them being destroyed(if we assume 100% destruction at 500 rem level). Considering you have developed a nanotech situation(with those buildings and such) it does not seem like it will be big loss for the stuff.

In general, having a developed nanotech situation, if the other side does not deploy countermeasures of similar nature - it stands no chances. And nuke deployment agony won't help them that much. Countermeasures of a similar nature do not mean a battle of clouds - it can be up to level individual nanohazard suits - which form some penetration barrier. If those are dummer version nanites - then suitable antibodies or something. Or a shell of nanites of a different kind that consumes attacking dust nanites as fast as they land on the skin/cloth. etc.

To conclude

Using nukes as countermeasures won't be effective and more so it will be more self-destructive. And if you have to use nukes - best you can do is to target those who are benefiting and controlling that nanite deployment.

Considering developed nanotech situation you have - building buildings I consider a sign of mature and abundant nanotech which then probably is used everywhere(most likely) replacing at least 90% of our todays doing with that assistance - and then it pretty much all-powerful situation to control any live organisms which do not have proper countermeasures.(maybe soil bacteria may be exempt - but only for reason there are too many of them, too deep and they mine their own business and not worth attention that much. require to spend too much energy for too little gain)

a tip

you may reconsider the nature of nanites, instead of imagining them like some nano fog and abstract small things, you may try to model them, imagine them as like 1-2um thick wires(which internally consist of 1000's if smaller wires, that internal structure makes it possible to actuate and do some magic. I call it smart matter, and there are few articles about it) of 0.1-1-100cm length's(different sizes). wires which can act like worms or snakes of their size, so as fiber like wool, glass fiber etc with capabilities to form ropes, fabric, beams, whatever you may imagine carbon fiber or fiberglass to be used for etc etc.

It may make it easier for you to imagine the properties of objects made of those 2d nanites, and it is a possible direction of nanotech development(lookup for "artificial muscles"), in some sense maybe even more practical, with plenty of utilitarian use. And it can be easier mapped to the objects and stuff we have today, with additional properties which come from the flexibility of arrangement of those microwires.

It may help to imagine more interesting deployment tactics and countermeasures tactics or helplessness in the absence of those countermeasures. There are endless ways to spin stuff in those circumstances - any flying apparatus (airplane, blimp, missile) reaching the area of deployment and then disappearing in dust cloud falling on the area. Small worm-like stuff digging sub mm tunnels network under area 2-3-5km deep underground and bursting out covering everything with them in a matter of minutes when the time comes. Disguise as usual live organisms wandering around and blasting on command in small particles to glue to anything you may target etc etc.

So as it is easy to tune the situation, when both sides have the nanotech, to any outcome as it is typical "shield vs sword" situation

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  • $\begingroup$ +1 for sensibly pointing out that self-replicating nanomechanisms are one of the better ways to counter other self replicating nanomechanisms (though personally I suspect that the kind of thing that the OP envisages is almost entirely impractical and perhaps outright physically impossible). $\endgroup$ – Starfish Prime Nov 8 '19 at 14:32
  • $\begingroup$ can't remember exactly, but maybe my thoughts about nanite like systems started from something like this and combined with artificial muscles researches which are going one(basically in more wider sense better actuators for cybernetic systems) combined with a list of ways and properties of carbon nanotubes - I'm quite optimistic about practical and efficient systems which are capable to act like classically envisioned gray goo while not being one. Self-replicating aspect is possible, it a big topic, but there are a lot of misconceptions $\endgroup$ – MolbOrg Nov 9 '19 at 6:25
  • $\begingroup$ @StarfishPrime in general if OP can flow on what's physically possible, and a plot be lead by that - there is endless possibilities for interesting stuff. In general, I hold the opinion - such systems are possible and are practical, but we probably need Asimov or Clarc like persons, which have enough knowledge to guide/depict those possibilities and potencial. $\endgroup$ – MolbOrg Nov 9 '19 at 6:30

There are known human survivors that were as near as 100m from ground zero in the world war II nuke attacks. What likely saved them is their thermal mass, and that of the obstacles shading them.

Something very small does not have that luxury - if an environment of (conductive/convective) unbearable heat is created around it, it has no choice but to be very quickly heated up to that level, destroying it to the core.

Radiant heat could be dealt with up to a certain level by being reflective - however, that would put up the complex question whether anything smaller than the wavelength of IR radiation can be made an efficient enough reflector (compare an intact razor edge - it looks dark because it is actually thinner than visible light)...

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Yes, if the nanites are solar powered.

You could use nuclear bombs to throw up large dust clouds (or cause a volcanic eruption) which would darken the sky for some time and deprive the nanites of their power source. Volcanic eruptions can also cause global acid rains.

Of course the collateral damage would be significant.

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    $\begingroup$ Please don't do this. I don't want to be taking any colorful pills any time soon. $\endgroup$ – Bilkokuya Nov 8 '19 at 17:05

Following on from Starfish Primes answer, the nano-machines can be blown easily, and as a result can be compressed into a smaller, more compact, cloud. This can then be more easily destroyed with a nuke.

The procedure could be as follows; 1. Large fans are positioned to push the swarm down and inwards, the fanse could possibly be jet engines as they have a very strong backwards flow, and are easily available. 2. Drop a nuke on the cloud.

4 stage diagram

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    $\begingroup$ Fans will never be powerful enough to compress the cloud. As you won't be able to move the nanites relative to the surrounding air, you will need to instead compress the whole nanite-polluted air mass. Even with jet engines, you will get a mostly incompressible air flow, with air flowing inwards along the axis of each engine, and the same amount of air flowing outwards along the gaps between engines. $\endgroup$ – Edgar Bonet Nov 8 '19 at 9:09

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