I'm currently trying to create a separate kind of Earth, without just changing my setting to a world that fits my criteria. So I'm trying to figure out a way for Earth to have a new beginning, so that I can develop an entirely new world, while also maintaining the aspects of this one, with minor details changed. So let's say that an asteroid hit Earth. Would it be possible that it could set off a nuclear bomb, and possibly create a chain reaction of explosions that wipes off all life from this planet?

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    $\begingroup$ Although all nuclear weapons going off would be devastating to life on Earth, there's no reason to think it would wipe out all life. We've indications that life would adapt and survive in various forms. $\endgroup$ – StephenG Jun 20 '18 at 3:15
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    $\begingroup$ All military weapons, including nuclear, are carefully engineered and controlled specifically to prevent unintended, negligent, criminal, or accidental misuse. Controls include fail-safe designs and physical locks. The USA has actually dropped a real nuclear bomb by accident: The conventional explosives detonated, but good controls prevented a nuclear explosion. $\endgroup$ – user535733 Jun 20 '18 at 4:53
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    $\begingroup$ @user535733 In the 1958 incident you linked to the bombs didn't have the plutonium core installed, so there was no risk of causing a nuclear explosion. There have been other cases though, where the bombs were fully armed and yet they didn't explode because of the safety triggers: en.wikipedia.org/wiki/1966_Palomares_B-52_crash $\endgroup$ – Rekesoft Jun 20 '18 at 9:01
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    $\begingroup$ Since this is tagged as reality-check, it might be worth noting that all the nuclear weapons on Earth detonating at once would not even nearly wipe out our current infrastructure, much less most life on earth. Nuclear/radiation danger was over-hyped during the Cold War and nobody got the message to correct it. oism.org/nwss/s73p912.htm $\endgroup$ – Korthalion Jun 20 '18 at 10:53
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    $\begingroup$ The bombs going off would be the least of your problems after an object from space obliterates Earth. $\endgroup$ – Mazura Jun 21 '18 at 0:51

The meteorite started the war.

The country hit by the meteorite considered the impact an indirect attack by the nations that did not warn them.

For example; foreign space agencies collectively refused to inform Pakistan of the meteorite about to hit them. Pakistan is justifiably angry at every space faring nation, particularly India due to past conflicts. Given the chance of a nuclear war, NATO intervenes which China fears is western influence in Asia. This spirals to bring in all other nations.

Alternatively, the country hit is considered unable to retaliate and another nation takes the chance to defeat another nuclear power. Again an example featuring Pakistan and India; the meteorite destroys what is thought to be India's best protected nuke silo and Pakistan thinks it can destroy all of India's other nukes before India can strike back. This turns out to be wrong, and India retaliates with its remaining nuclear weapons. Again, the conflict brings in other nuclear armed nations leading to a general nuclear war.

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    $\begingroup$ +1 for the plausible nuclear war from a meteorite, you could also have during cold war times, that USSR and USA really don't get along, one of them performs a simple test of its launch systems, and the missile was terminated just after launch (this did happen from time to time) Russian spies witness this and then don't witness the self destruct, several minutes after reporting it, Russia gets hit with the meteorite and as far as they know, the USA just attacked, they fire back etc etc. $\endgroup$ – Blade Wraith Jun 20 '18 at 8:45
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    $\begingroup$ Robert Watson-Watts, a British radar pioneer, during the Cold War, was afraid a large meteor entering the Earth's atmosphere would be misinterpreted as an ICBM attack by one or both of the nuclear super-powers. Luckily this didn't happen. It is and was a plausible scenario for an accidental nuclear war, $\endgroup$ – a4android Jun 20 '18 at 8:51
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    $\begingroup$ This is actually a real-world problem that has been addressed several times in the past. Many nuclear-armed countries don't have the technology to distinguish a surprise nuclear strike from an asteroid collision, and in a tense situation this could very easily trigger a global nuclear war. space.com/20310-russian-meteor-missile-attack-military.html $\endgroup$ – IndigoFenix Jun 20 '18 at 11:56
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    $\begingroup$ @BladeWraith Actually you don't even need a meteorite for that. All it takes is glitch in a computer system as almost happened in 1983: theregister.co.uk/2013/09/27/… $\endgroup$ – Otto Abnormalverbraucher Jun 20 '18 at 14:33
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    $\begingroup$ @ well everyone, completely agree, it was purely if the OP wanted an asteroid to be the real blame, the computer glitch actually happened in real life, a russian officer saw the readings of a launch and decided it was a false alarm and choose not to launch, en.wikipedia.org/wiki/Stanislav_Petrov all it would take is a less level headed bloke with his finger on the button $\endgroup$ – Blade Wraith Jun 20 '18 at 14:44

Yes and no.

An asteroid, or any impact really, cannot set off thermonuclear warheads, in the sense of causing a nuclear blast. These warheads are composed of disks of conventional explosives that have to go off in an extremely precise manner in order to achieve a proper nuclear detonation. If that doesn't occur - if they go off in any other configuration - all that happens is a modest conventional explosion. (It's fairly radioactive, similar to a "dirty bomb", but more importantly it's fairly small.)

However, an asteroid is totally capable of wiping out life on earth all on its lonesome. You might look up the Chicxulub impact, which caused extinctions on a massive scale although, obviously, it didn't totally destroy life on earth. But the next one could be bigger, if you want.


Not With An Asteroid

Nuclear bombs are not giant snap-caps just waiting to be jostled wrong to detonate. Outside of human error or intentional warfare a majority of nukes will not detonate.

Quantum Effects

It has been observed that some quantum particles can induce fission in fissile materials on at least a small scale. Years ago I spoke with a nuclear physicist about some sort of muon or gluon gun that could fire through the earth. Such particles have very very little interaction with most matter, but could, at high energy levels and in massive concentrations, be used to induce a fission reaction in the fissile material of a nuclear weapon.

In nature gluons and muons do not exist freely, but are found in the substance of an atom's structure. It would be massive handwaving here, but some sort of crazy powerful gluon pulse could induce nuclear warheads to begin fission and generate at least a low yield detonation. But we're talking a LOT of handwaving.

Why Bother With Nukes Though?

The gamma ray burst from a supernova could scour life off the planet down to a molecular level and occur naturally in space all the time. Why not just use one of those in your story?

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    $\begingroup$ +1 for Gamma Ray burst, could be devastating for Earth and is actually the simplest "No terrestrial" answer to the OPs problem $\endgroup$ – Blade Wraith Jun 20 '18 at 8:47
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    $\begingroup$ Would a gamma ray burst from a supernova actually be strong enough? I'd have thought the distance of most stars from us would mean that any radiation burst would be pretty weak by the time it got to us - or do they send out pretty focused bursts? $\endgroup$ – Chris Jun 21 '18 at 8:24
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    $\begingroup$ Gamma ray bursts are directed cones of radiation fired from the poles of the star as it collapses and then explodes. Instead of a typical nova that scatters the energy everywhere in a sphere think of it like a shotgun blast that directs a cone containing a significant amount of said energy in a specific direction. They can be hundreds of light years long. You are correct, MOST stars don't ever even create a directed gamma burst, but it only takes one within several hundred light years to be pointed in the right direction when it goes to reduce life on earth down to prions. $\endgroup$ – TCAT117 Jun 21 '18 at 13:59


Nuclear weapons are designed so that they cannot detonate by accident. Even if you had one inside a briefcase and dropped the 'case from a building, it wouldn't go off.

And if you want terminate life on Earth, worry not: just take an asteroid of pure iron, twice the size of the dinosaur-killer, and you'll make sure to have a long-lasting nuclear winter. The food chain will completely collapse, save for extremophiles, insects, some marine life form at the bottom of the oceans. With some luck, rats could thrive enough on the many cadavers left until they become the start of the new dominant life form in a million-years long future...

  • $\begingroup$ Most of the lasting climatic damage from Chicxulub was from the vapourised gypsum and limestone pumping sulfur aerosols and carbon dioxide respectively into the atmosphere more than the meteorite impact itself, something twice the size wouldn't necessarily do that much more damage. $\endgroup$ – Ash Jun 10 '19 at 12:13

Not with current nukes because of physical shock, modern nukes are way too complex and stable. There are two ways something could happen though:

  • the asteroid is a source of unimaginable levels of neutron flux. This would lower the effective critical mass for the radioisotopes in the core of nuclear weapons and cause them to detonate without being triggered. Before it did so it would also kill all life on at least half the planet without ever touching down.

  • if Implosion Core weapons were never invented, and/or if nukes used more volatile conventional explosives in their triggers. That would leave you with Gun style nukes which could feasibly be dangerously shock sensitive, and go off during large earthquakes, or bombing raids, etc...

Neither of these solutions give you any kind of worldwide chain reaction but do open the door for localised unforeseen detonations because of a celestial impact event.

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    $\begingroup$ If a nuke used conventional explosives, it wouldn't be a nuke. $\endgroup$ – user39548 Jun 20 '18 at 15:17
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    $\begingroup$ @Hosch250 All nukes use conventional explosives, they wouldn't go off otherwise. $\endgroup$ – Ash Jun 20 '18 at 15:18
  • $\begingroup$ Oh, I misread the post. I thought you meant the core was replaced with conventional explosions. Hmmm, you could replace the conventional explosion with one that explodes on impact to ensure it goes off when it hits the ground if it fails to go off in the air. $\endgroup$ – user39548 Jun 20 '18 at 15:21
  • $\begingroup$ @Hosch250 Having read it back I can see that, I've edited my answer to hopefully be a little clearer. Yeah I was thinking something like using a nitro based propellant in place of the modern electrically detonated HE in current warheads. It's a really bad idea but you would necessarily know that until the impact since missile silos have to be in tectonically stable areas anyway. $\endgroup$ – Ash Jun 20 '18 at 15:27
  • $\begingroup$ +1. I could definitely see someone wanting to do this in the past--perhaps they did it to ensure nobody could get the tech, then someone else got it anyway. But at that point, nobody questioned why use nitro-based... $\endgroup$ – user39548 Jun 20 '18 at 15:31

You might consider if the following scenario fits your needs:

A huge asteroid is coming towards Earth. Because people are scared, they decide to attack it with nuclear missiles. Some scientists/engineers say it will be enough to attack it at one particular point. Others say that that's entirely wrong. Attacking it in that way, at that time, will just create a giant cloud of radioactive (from the nukes) debris. It turns out that the latter scientists were correct.

This gives you the radioactive fallout problems of a complete nuclear launch while avoiding the problems associated with accidental triggering or a nuclear war.

It really depends on what is important to your story. There are any number of ways of killing off everyone with an asteroid. You don't need a nuclear launch. There's also any number of ways to have a nuclear war. You don't need an asteroid. If for some reason, you need both nukes and an asteroid, this should give the result you want.

  • $\begingroup$ Guess what? Nukes don't have a blast in space. You don't get a shockwave without a medium to create a wave in... Of course, with that amount of energy, you might just vaporize the asteroid. $\endgroup$ – user39548 Jun 20 '18 at 15:16
  • $\begingroup$ @Hosch250 who said anything about a shockwave? besides, would not particles of a high velocity asteroid be a sufficient medium? $\endgroup$ – Richie Frame Jun 20 '18 at 23:26
  • $\begingroup$ Depends if the asteroid exploded without the shockwave. From my understanding, a nuke wouldn't be very effective in space at anything except EMPs and vaporization, but I may well be wrong. $\endgroup$ – user39548 Jun 21 '18 at 2:17

There are two main pathways by which the asteroid could detonate the nuclear weapons: either through a chain reaction or by simultaneously triggering all of them.

Chain reaction

This variant assumes that at least a couple nuclear weapons are set off by the impact, and these in turn trigger the others. This is unlikely; the Tsar Bomba, the most powerful nuclear weapon detonated to date, had a yield of 50 megatons of TNT - much, much greater than any weapon we have today - and caused damage hundreds of miles away. For comparison, if we look at the current arsenal of the United States, we see that the common W87 and W78 have yields of about 1% that of the Tsar Bomba. The W76 and W88 are even smaller; to replicate the Tsar Bomba's effects, you would need to detonate many of them together in a small space.

If you could do this, then you could impact structures and weapons for hundreds of miles around. But if warheads were only triggered in a couple of silos, the damage would be minimal, and limited to small areas; other launch sites would probably not be detected. If we look at where the weapons are distributed, we see that the operational storage sites (in red) are far apart in the United States.

Map of nuclear weapon distribution
Map from the Federation of American Scientists.

Granted, each site then has a large yield, but you'd need all of the weapons at the site to be detonated at the same time to have any effect on the other sites. The same is true around the globe, although western Russia does have a higher density.

Simultaneous detonation

Now, alternatively, you could try to set off all the weapons at once. Here's the problem, though: you'd need a heck of a big impact to do this. Neither the US nor Russia has a majority of the world's deployed nuclear weapons, so you'd need to set off weapons across at least one country and then some. This would require an impact of colossal size to even reach, by some means, warheads thousands of miles away. Again, see the map above.

Of course, you could go for some sort of seismic activity. After all, the Fukushima disaster began when a tsunami disabled critical parts of the reactor, and the seismic waves generated by a large impact would be severe. Nonetheless, this would still require a massive impact, and given that nuclear weapons systems can withstand some pretty strong earthquakes - there have been no seismic-triggered detonations to date - this seems unlikely. The farther from the point of impact, the weaker the seismic waves.

Human error

Now, there is a third possibility, which is that a nuclear weapon would be triggered on a nation's soil. If the weapon wasn't detonated but was somehow launched - and I'll be honest, this is a really improbable scenario - that it's possible that the target nation would see this and consider whether the launch was an accident or a deliberate assault, with the impact as cover. At that point, you do have the risk of intentional, manual nuclear retaliation, and that could maybe achieve your goals. But that's a pretty far-fetched scenario.

I've purposely shied away from an even bigger problem: How would the object even set weapons off? Cadence talked about how there are a whole bunch of things that would have to happen for a single weapon to be detonated. So this asteroid would have to somehow destroy the sensitive systems that prevent accidental (or malicious) detonations without damaging the warheads themselves.

All that said . . . NASA has space rocks monitored fairly well. If something big was coming our way - big enough to impact an entire continent (pun intended) - then we would know about it long in advance. That would give the world time to plan and, more importantly, disable nuclear devices if it seemed like there was even the risk of some accidental detonation.

  • $\begingroup$ I was mainly concerned with the clever engineering required to set them off in the first place, but you're right, there's even more clever mechanisms designed to keep them from going off when they're not supposed to. $\endgroup$ – Cadence Jun 20 '18 at 3:25
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    $\begingroup$ So if I'm reading this map correctly, the 12% or so of the world's population that live in the southern hemisphere are relatively safe, from the blasts at least. I think I've found a way to make Australia the superpower it deserves to be. $\endgroup$ – Tim B II Jun 20 '18 at 3:56
  • $\begingroup$ @TimBII Yeah, I like their odds. I mean, the fallout's possibly going to kill them at some point, but in the days and weeks after, even if everything is detonated, Australia will enjoy an age of relative prosperity. $\endgroup$ – HDE 226868 Jun 20 '18 at 3:57
  • $\begingroup$ I think we'd have time to get fallout shelters ready before the radiation reaches us. They don't call our soldiers 'diggers' for nothing... $\endgroup$ – Tim B II Jun 20 '18 at 3:59
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    $\begingroup$ @HDE226868 - Reigning in hell? en.wikipedia.org/wiki/On_the_Beach_(novel) $\endgroup$ – Tom Goodfellow Jun 20 '18 at 7:40

Yes. Though highly improbably (and highly implausible), the impact of a sufficiently large extra-planetary object with the earth at the right spot could detonate the majority of earths nuclear weapons.

Due to the precise timing required to actually detonate a nuclear weapon, all nuclear weapon designs in existence have a small vulnerability in that an energy signature (wave, fluctuation, etc.) at a specified frequency for a specified time could potentially arm the weapon.

A meteorite impact on the worlds largest quartz deposit would cause a Piezoelectric event that could very well cause this exact energy disturbance, unknown to the current world powers. The impact itself could release several different signatures as needed by the story, due to tumbling or other stage impacts from the event.

DISCLAIMER: a bunch of this is likely pseudo-science, but I tried to stray away from any hand-waving or suspension of disbelief.

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    $\begingroup$ Agree about the pseudo-science, but I don't think you strayed very far from hand-waving there. What's the basis for the 'small vulnerability' claim? The phrase "energy signature" sets off my pseudo-science alarm. $\endgroup$ – Spike0xff Jun 20 '18 at 17:23
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    $\begingroup$ @Spike0xff At a guess, it's that the explosives used to detonate a modern nuke are electrically triggered, so a sufficiently potent EMP wave at the right frequency might trigger them... I doubt the frequencies are consistent between devices, and I doubt that there'd be a big enough EMP from any meteor that didn't cause the end of human civilization just by itself though. $\endgroup$ – Perkins Jun 20 '18 at 21:32
  • $\begingroup$ "Yes." +1. However, "I doubt that there'd be a big enough EMP from any meteor that didn't cause the end of human civilization just by itself though." Also, +1. TL;DR: yes, but there's no one left who cares. $\endgroup$ – Mazura Jun 21 '18 at 0:55
  • $\begingroup$ @Spike0xff the 'small vulnerability' is the real handwave here. The 'energy signature' is just a generic reference to the Piezoelectric result of the impact in a quartz field. I've been pretty tired so the quality of my answer was not what I would have liked. $\endgroup$ – GOATNine Jun 21 '18 at 10:51

The problem is what it takes to compress a nuclear warhead to critical mass if you forego the extremely precise triggering mechanisms they use.

That said, theoretically, a sufficiently large antimatter bomb falling from orbit could create a blast powerful enough to do it... On the other hand, once you get to that point the extra explosions will likely go largely unnoticed by the expanding cloud of gas and gravel that used to be called Earth...

Now, there are a few other possibilities that might give you what you want. For example, there are some rumours that the Russians may have cracked their tectonic plate testing nuclear bunkerbusters. If multiple countries in just the wrong places did something like that, it might be possible to trigger a crust slip. That would cause tsunamis worldwide and rearrange the climates of our various land masses by moving them to other lattitudes. If nuclear isn't a requirement a set of asteroid impacts at just the wrong angles might do the same thing.

I suppose you could also have a largeish meteor land in Yellowstone ( https://en.wikipedia.org/wiki/Yellowstone_Caldera ) and set that off. That could easily cause the end of modern civilization as well.


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