# The perfect weapon against humanity? [closed]

So, there are these fantastic creatures (dragons, unicorns and whatnot) they have the advantage in individual strength, but they're massively outclassed in terms of numbers, plus humans can achieve much more together.

God doesn't like the humans' plans to exterminate his fantastic creatures, so he decides to preemptively annihilate humanity, not just the men but the women and the children too.

There is a rule, however: God can only create, and only 1 kg of something, that adheres to the rules of physics and can only create once every thousand years. He can create that thing anywhere, though.

What would be the most surefire way for God to kill off humanity, and only humanity, before they could kill of the fantastic creatures? Note: Despite their impressive death toll, many plagues failed to completely eradicate humans. Tech level is late medieval.

• Try sand, it's coarse and rough and irritating and it gets everywhere. Humanity stand no chance. – Guy with jewels' names Jan 2 at 14:41
• Plagues had "low" deathcount because they weren't deployed in an intelligent manner. God can deploy 10dkg of his virus in 10 hubs all at once. – SZCZERZO KŁY Jan 2 at 14:43
• Isn't your setting just jam-packed with utility fog? Just tell the foglets to dismantle the humans. – Starfish Prime Jan 2 at 15:08
• Instead of all this killing non-sense, how about we domesticate the dragons, unicorns, and whatnot then nobody has to die. Pet dragon ... heck yes – cybernard Jan 2 at 16:07
• Let me point out a minor contradiction in your world. A God that can create 1 kg per millennium somehow also created dragons, unicorns & whatnot. All of which weigh more than 1 kg. Guided evolution over megayears might be possible, but really. If your God uses super technology too, then It might more directly intervene, thus bypassing the 1 kg limit. – a4android Jan 3 at 0:14

Does the 1kg have to be all in one place? If not, a plague could be still the way to go - He can infect every person in the world with just enough of the plague to kill them, or enough to get a foothold in their body that it can multiply spread throughout the body? Or even 1/population kg of anti-matter placed in the brain of every human alive?

• Ok, and what's the fastest possible route to total genocide for a plague, more precisely, how should it kill? Just curious. – Mephistopheles Jan 2 at 15:12
• Not really sure what you mean... I'm not really up on how exactly plagues kill, but I happen to know they do. I'm sure God could come up with a 100% effective one. – colmde Jan 2 at 16:01
• @JoeBloggs - Well just enough to toast x billion human brains then... assuming it's a max of 1kg – colmde Jan 2 at 17:06
• Plus, you don't need to infect all of humanity, you can just kill (or make sterile) one gender. – alexgbelov Jan 2 at 23:55
• Thanks @alexgbelov - I really do love days like this when I come to Stack Exchange to look up some Linux command, and leave pondering exactly how many grams of antimatter an omnipotent being would have to create in order to explode every penis on the planet. – A C Jan 3 at 4:24

Basing on this article, lets assume one virus weight 10^-18 grams, also lets assume the world population is 10^9, its roughly same like XIX century our world. This give us way more then billion viruses for one person. If only god could place them all in humans, well, humanity is doomed.

• If only god could place them all in humans, well, humanity is doomed. Doesn't really need to: make it airborne, drop it in a few of the world's busiest airports and/or make it resistant to heat, enough to withstand a few seconds in a jet engine. Some will be distributed by the passengers, some will enter the fuel tanks and be dispersed in contrails, and the rest is human history – nzaman Jan 2 at 17:54
• @nzaman : "Tech level is late medieval." I don't know what the late medieval was like in your world, but around here, there were no airports. – Eric Towers Jan 3 at 5:59
• @EricTowers: Missed that! – nzaman Jan 3 at 7:45

Botulinum toxin is regarded as the most lethal substance known to man, and has an LD50 (the concentration required to kill half the exposed population) of just 1 nanogram per kilogram in humans. 1kg of botulinum toxin is enough to give every single one of the 7 billion people on the planet more than double the LD50 dose. For planets with a smaller population, you could give a commensurately higher dose, to levels approaching near-complete mortality.

This will kill well over half the people on the planet, and although we don't know the LD100 of the toxin (dose required to kill everyone), it's possible you might wipe out everyone. At any rate, the stragglers will be very sick and geographically distributed, so society might just peter out after such a sudden and severe blow.

• The world population in the late medieval period was only 350-400 million. So you can take that 2x lethal dose and multiply it another 20 fold. Other than a small handful of people who may have a natural resistance to the stuff, you're probably killing everyone. And if your god is omniscient, he will know who will be resistant and be able to plan alternate deaths for them. – Nosajimiki - Reinstate Monica Jan 2 at 22:11

A cup of ambrosia to give the drinker immortality. But there's enough for just one person...

1kg worth of Von Neumann machines (assuming the mass threshold of a Von Neumann machine is < 1kg) could do the trick. Given enough time they convert all mass in the universe into more Von Neumann machines.

Of course, this isn't what you want them to do, but presumably you can program them to do whatever you do want. This effectively lets you bypass the mass limit. For example, God might create the "seed" machine on the moon and have it build some sort of human-targeting orbital weapon system. Or He could create it on Earth and it could churn out engineered insect-like robots that kill humans.

• Welcome to WorldBuilding.SE! I'm afraid this violates the OP's requirement to wipe out only humanity, and not everything else, so this doesn't answer the question as asked. – F1Krazy Jan 2 at 18:36
• @F1Krazy They could easily be programmed to do whatever task is desired and nothing else. – SurpriseDog Jan 2 at 19:15

A 1 kilo book (or maybe a stone tablet if he's keen on brevity) explaining the Will of God in a manner that causes violent religious wars to sweep through humanity, so they exterminate each other with zealous enthusiasm.

God is smart and can easily manipulate humans and foresee their reactions. Any attempt to stop the religious wars results on more claims of heresy, blasphemy and apostasy and produces even more splintered factions so even the anti-religious-war groups are far more interested in killing each other than anything else.

• You'd have to be extremely detailed and convincing with mere words to get people to kill each other regardless of their situation. Most religious wars stopped when other matters started becoming more important. Like starvation or plague. There is a certain minimum amount of resources people use before they go to war. You aren't going to start a war if you can't even feed the soldiers long enough to actually last a few battles or arm them with sufficient weapons. And you also have to convince every type of personality to join in regardless of age or sex AND spread this book enough for everyone. – Demigan Jan 2 at 17:55
• History suggests that it wouldn't work. Why else are all those people still alive? Throughout history we have seen entire people's being extinct by other groups of people, but the point was that then their lands were taken over by their agressors. Only natural disasters like global plagues have come close to exterminating large swathes of humanity, so much so that at one point less than 10.000 humans were left in the world. But we could always rebuild. Knowledge as catalyst for this war would need this knowledge and hatred to persist even if most people have died out. – Demigan Jan 2 at 18:03
• In the past none of the books were written with divine foreknowledge and the intent of causing genocide. Looks what we've done with books based on love, think what we could do with books based on hate and cleverly engineered to work on our weaknesses. – David Hambling Jan 2 at 21:01
• I would expect those books not to be of any interest to most people. While more satanic books do exist they usually don't draw a crowd. The books of "love" that have many scenes of torture, murder and mayhem at the very least have a core set of rules and ideologies that people can agree with. And again no matter how good the book is, people's mindset to war won't change. They might be more hell bend on warfare (assuming they can agree on it and not go into civil war), but every time their organization fails they'll be murdered & replaced or have time to rebuild for the next war. – Demigan Jan 3 at 8:06
• @DavidHabling I think you are overestimating the power of written words. – Demigan Jan 3 at 22:21

You create 1kg of a rather vicious form of the Gimpy plant that will spread across the world?

https://en.wikipedia.org/wiki/Dendrocnide_moroides

Modify it so that it'll actively fire it's needles when it smells humans. Even better if this isn't even a plant but a living and breathing creature that actively seeks out human populations to live nearby and attack if they get too close. Think of a few modified all-seasons Rabbit for example. Extremely hard to hunt down to extinction and if it actively targets humans with it's needles... Oh boy. Entire villages would simply relocate when they detect these critters until there is nowhere to relocate to. Even if you use traps to kill them, how is a medieval person going to get rid of the bodies? You'd need plate armors and no accidental contact with the needles and even then it's hard to find a good way to rid yourself of the needles that ineviteably fall out.

As a more humane alternative (?) God could simply sterilize the entire population with the same antimatter trick @colmde proposed, but limit it to the viable eggs (1-2 million oocytes per female).

1 kg hydrogen is 1000 moles of hydrogen, so 6.023 * 10^26 atoms (1000 x Avogadro's number). This leaves ~10^9 anti-hydrogens per egg, which seems more than sufficient, even with back-of-napkin calculations.

This does mean your beasts need to survive about 20 years to ensure that the younger humans don't finish them off, but I suspect apathy and cultural destruction will make that a non-issue unless your beasties are presented as some sort of ultimate devil-spawn in your setting.