The enemy is approximately 100 million in number and are closing in fast from the orbit of Uranus, at a constant speed of 70 km/s (in near perfect vacuum condition). They are like clones and each one is the size of a mini Cooper made almost entirely of carbon nanotubes (displacement of 3,141Kg with full propellant). They act as a swarm, similar to a shoal of fish, but more delicate and graceful. Smaller swarms may branch off to attack high value targets like our communication facility or supply network, then merge seamlessly with the main swarm. Their propulsion appears to be some sort of advanced ablative casimir matter-antimatter warp drive hybrid(specific impulse of est. 80,000s).

It seems they only rely on their rigid structure to penetrate our defenses, they have no other weapons, no force shield, no bio signature, and strangely no known communication among themselves! At least based on our existing model of physics that is.

Their purpose is to exterminate (indiscriminately) all intelligent carbon based lifeforms in the Milky Way galaxy. Their movement is directly proportional to their surface temperature, the hotter they are up to a maximum temperature of 3500℃ their speed can clock up to a maximum of 80km/s for a couple of minutes in empty space. They never rest until their battery runs flat! aside from the flying in disciplined phalanxes thing during search and destroy, they do not seems to have any kind of strategy at all.

Using existing 21st century technology, how could we prevent our own extinction by such a mysterious and formidable foe?

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    $\begingroup$ Rezzzzzzistance is futile.... $\endgroup$ – Harry David Oct 8 '16 at 7:33
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    $\begingroup$ Does smoke put them to sleep? :-) Seriously, I love the idea of this question, but I'm really struggling to imagine what the answer would look like. I can think of a bunch of good answers, and that's a problem, unfortunately. Can you maybe edit your question to throw us a bone, in terms of a fictional weakness that your fictional scientists have come up with? Because I can't think of anything intrinsic to this type of swarm that could be used. $\endgroup$ – type_outcast Oct 8 '16 at 8:08
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    $\begingroup$ Are they intelligent or dumb? They seem to have a (presumably self-assigned) purpose, implying intelligence. If their purpose is to exterminate "all intelligent carbon-based lifeforms", then shouldn't they be trying to kill each other instead, since they fall under their own criteria? The threat might resolve itself. $\endgroup$ – code_dredd Oct 8 '16 at 11:06
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    $\begingroup$ Well, they are perfectly capable of interplanetary - or maybe even interstellar - navigation. If navigating from Uranus to Earth is no biggie for them then grabbing some asteroids along the way shouldn't be either. $\endgroup$ – Daerdemandt Oct 8 '16 at 15:05
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    $\begingroup$ Let Earth's Atmosphere do most of the work. As q beast enters our gravity and carrels into the atmosphere, they will burn up just like a small asteroid would; their invasion would creating a meteor shower of sorts. $\endgroup$ – Harry David Oct 9 '16 at 9:16

11 Answers 11


Swarm and flock members follow very simple rules that let them maneuver in concert with the others. They use the perceived rate of change in speed and orientation of their most immediate neighbors. http://www.red3d.com/cwr/boids/

If the aliens adopt such a pattern of flight, it's a strong indication that they follow similar rules, with comparable inputs. The best way of disrupting or redirecting the swarm (into the Sun?) would then be to exploit this behavior.

1) Find out how the aliens perceive their immediate neighbors (sight, electromagnetism, etc.).

2) Engineer devices that can mess with these signals (holograms, movable magnetic fields, etc.).

3) Use them to take control of the swarm or to turn it against itself.

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    $\begingroup$ Hi Stephane, unfortunately based on our state of the art radar nothing suspicious radiates between the enemy. This implies that they could be using some form of communication means not known to science! I'll repeat Harry David's comment: Rezzzistance is futile... $\endgroup$ – user6760 Oct 8 '16 at 8:37
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    $\begingroup$ This doesn't preclude them from using more conventional senses for flock control ;) Otherwise, just ask Mazer Rackham :) $\endgroup$ – Stephane Oct 8 '16 at 8:58
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    $\begingroup$ There are 100 million of them. We don't have 100 million nukes to fire at them. $\endgroup$ – Mike Scott Oct 8 '16 at 10:52
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    $\begingroup$ @Stephane: +1 for actually trying to find a solution by spotting weak links in a chain. $\endgroup$ – Nav Oct 8 '16 at 17:06
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    $\begingroup$ nothing suspicious radiates between the enemy. - heat means they can just see each other, not need to dig where is nothing, radars will not help to detect vision. Intelligence is a problem here, it they are fishes dumb it is one situation, if they are more sophisticated then another. $\endgroup$ – MolbOrg Oct 8 '16 at 20:48

All of the workable defense strategies I've read thus far assume the space bees are in a tightly packed formation. There is no particular reason for this to be the case, and since they are not idiots I am going to assume they spread themselves over the maximum volume possible. A relatively small sacrifice in delta V will result in very large fleet dispersals meaning that no nuclear weapon will be able to kill more than a single bee, and clouds of dust or sand will not be large or dense enough to materially affect the fleet during transit.

The OP says the fully fueled mass of the bees is 3141kg. Using this online calculator http://www.strout.net/info/science/delta-v/ an 80,000 ISP, and 70,000 m/s delta V suggests an unfueled mass of 2870 kg. That gives me a 7E12 joule energy. (i.e. 7 terajoule or 1.6 KT)

The total energy of the fleet will be 7E20 joules or 170,000 MT. The bolide which killed off the dinosaurs is estimated to have had 130,000,000 MT of energy, so the bees would have almost 1,000 times less energy if they all get through our defenses.

This handy calculator gives you the effects of an individual impactor. http://impact.ese.ic.ac.uk/cgi-bin/crater.cgi?dist=.001&diam=2.76&pdens=261&pdens_select=0&vel=70&theta=90&tdens=2500&tdens_select=0 projectile diameter is 2.76m, density is 261 kg/m^3, velocity is 70 km/s, angle is 90 degrees. The one problem it has is that it assumes an impactor tensile strength of a natural material, whereas these impactors are made from carbon nanotubes. I don't know how to calculate how atmospheric frictional heat loadings affect the material, nor what kinds of tensile stresses result from the atmospheric traversal, but I think it is safe to say the impactors would penetrate to a lower altitude than indicated in this calculator. But since the calculator has the impactor detonating into a fireball at 121,000 meters altitude, I think it's very unlikely that it would reach a low enough altitude to markedly affect the surface before it detonated into a fireball.

The other noteworthy takewaway from this calculator is that the fireball energy is only 1/7th the kinetic energy of the impactor. (Presumably the rest is lost to friction prior to this point.)

This puts the attack in a very different light. Essentially all of the energy of a fleet attack which was well distributed across one half of the Earth would go toward heating the atmosphere, producing little or no effects on the ground other than loud noises and bright flashes of light.

In order to produce any truly dangerous effect, the attack would have to be focused. If the bees fire a dense stream of impactors at selected targets, they can produce deeper penetrations. The initial impactors would produce a partially evacuated shockwave in their wake, through which the following bees could travel with less energy lost to the atmosphere as friction, resulting in lower detonation altitudes (possibly not detonating until impacting with the surface). Also, the thermal flash effects would be concentrated in one area, resulting in arbitrarily high thermal loads in that vicinity.

Potential strategic impact sites might include the Yellowstone super volcano (possibly requiring the entire fleet to cause any likely volcanic effect here?), nuclear reactors, flash heating attacks on drought afflicted forests in order to cause massive firestorms and nuclear winter effects (nuclear winters rely entirely on sending smoke into the stratosphere via a firestorm), flash heating of crop lands in order to create famine conditions, bioweapon research labs (human diseases are pretty bad, but just as horrible would be the effects of uncontrolled release of novel crop diseases), and oil refining and storage facilities (cripples our economy and contributes smoke to stratosphere).

One problem with focused attacks is that they make it easier for the Earth to degrade the attack (with nuclear detonations in space and sand cloud attacks). The goal would be to degrade the nanotube structures to make them break up higher in the atmosphere. The higher the altitude at which the impactor breaks up in a fireball, the less the damage to the surface.

I think the bees would be smarter to invest in larger and denser but fewer impactors. Carbon nanotubes might be good material for the outer skin (I'm not sure) but the impactors should carry a payload of natural (non-explosive) uranium, tungsten, or other extremely dense material. The impactors should be shaped like arrows, not like pods. They need to lose as little energy as possible on atmospheric friction, and density is the key to this. The impactors should come in a variety of sizes. Small impactors for nuclear power plants and ICBM silos. A super large impactor for Yellowstone and other super volcanos. If I were the aliens, I would generally ignore the cities and concentrate on killing the populace via secondary effects such as climate change, famine, infrastructure collapse, radiation contamination, and disease.

But to answer your exact question: The way to protect the Earth from a dispersed attack is probably to do nothing. The way to protect from a focused attack is probably, like people have said, nuclear missiles and clouds of sand focused on points in space where the bees are converging.

  • $\begingroup$ funny link about impacting. They calculate strength from material density $\lg(\text{strength in Pa}) = 2.107 + 0.0624 \sqrt{density}$ For 100GPa it should be 20310 kg/m^3 density, but it not works, but it works with 15000, with corresponds to 5.615 GPa. This density is not much a stretch, because they use spherical body to calculate drag, which easy not our case. omg I destroyed the earth. $\endgroup$ – MolbOrg Oct 8 '16 at 20:28
  • $\begingroup$ But it still tries to give some result with 27m projectiles, which is 1000 of bots sphere in worst case or some kind of arrow aligment with will make things better for them. Results they do not break until hitting the ground, and deliver 99% of their energy. Energy it shows is 6 times more then it should be, but valuable conclusion is 6GPa projectiles perfectly capable of reaching surface. So even single craft is capable of doing that with a bit more structural strength. 6GPa is 30 times more then usual rocks. $\endgroup$ – MolbOrg Oct 8 '16 at 20:28
  • $\begingroup$ Any idea how to take thermal degradation of the nanotubes into account? It looks like wikipedia is saying nanotubes break down above 750C in air (presumably burning). $\endgroup$ – hexagon Oct 8 '16 at 20:44
  • $\begingroup$ It is not a problem, count upper layers as ablation shielding. It should last for 2 seconds only, so heat penetration even with high gradient will be not significant(10-20cm), specially when u prepared for such actions. U can take 10 bots group and count one as ablation shield, or each may leak protective gas, as sort of lubricant(He, H, inert gases), it will rise max temperature significantly at least for 2000+K, which will be good for lubricant solution less gas is needed(hot gas more volume, ticker layer between atmosphere and projectile) $\endgroup$ – MolbOrg Oct 8 '16 at 21:11

What are we dealing with?

Given that there are hundreds of millions of them, and they are made of carbon nanotubes, most projectiles aren't going to work, and because they are already at Uranus we do not have much time to prepare:

at a minimum they are 2.6 billion km away, or 429.9 days away (max speed, min distance) And at a maximum they are 3.15 billion km away or 520.8 days away (min speed, max distance)

The time taken varies so much because it depends on how far Uranus is from the sun, and whether earth is on the same side or the opposite, which means we have over a year to prepare, and a year is how long it takes to build a nuke if you have the fissile materials already, so we would start building as many nukes as possible.

Problems with the swarm

These things are travelling at 70km/s and are the size of a mini cooper, which is about 1.55M high, 4.01M long and 1.79M wide, which gives a total volume of about 11.126m^3, and if that is pure carbon nanotubes, which have a density of 1.6g per cm^3, then each robot in the swarm is about 17.6 tonnes... so if one were to impact the earth, it would have 1/2 * m * v^2 = 83,300,000,000,000,000 Joules of energy... This is a ridiculous amount of energy: the most powerful nuke (tzar bomb) has about 100 mega-tonnes (built not tested), or about 418 petajoules, whereas one swarm robot has 83.3 petajoules... over a fifth of the energy of the most powerful nuke ever built and there aren't that many nukes available to have the same energy output as the swarm.

Conclusion / Tl;Dr

One swarm robot hits the earth and we all die, tsunamis and magnitude 10 earthquakes will happen, maybe some arctic researchers will live, but that is about it, this swarm is near unstoppable on kinetic energy alone and does not need any weapons of any form to be well beyond our capacity to deal with.

Maximum potential of the swarm

This is the absolutely everything goes wrong scenario, where all of the swarm is at 80km/s and all 100 million of them hit the earth at once, you have 10,880,000,000 petajoules of energy. The sun outputs 384,593,280,000 petajoules of energy... meaning our swarm's kinetic energy is greater than 2.5% of the power output of THE SUN in one second. ... I have checked these calculations many times and have made many adjustments, but I think this is finally correct, if these are wrong I no longer care, do your own research and compile your own answer.

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    $\begingroup$ Before my question is forced to close, I did warn in my comment that these foe even put powerful species in Star Trek to shame also I even throw in a otherworldly engine to allow them to deal with all carbon based lifeforms in the entire galaxy. Anyway thanks for working out the math they are beyond me. $\endgroup$ – user6760 Oct 8 '16 at 11:29
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    $\begingroup$ @user6760 I hope this question doesn't close, I love the sheer destructive potential of it, and no worries for doing the maths, give me a maths question and if its a fun question then i'll love working out the answer :) $\endgroup$ – Alex Robinson Oct 8 '16 at 11:37
  • $\begingroup$ I calculated it to take 430 days to get here, where did you get 8.6 hours from? Uranus is over 2 light hours away. 70kms isn't anywhere close to 0.25c. Your maths is terrible. $\endgroup$ – Innovine Oct 8 '16 at 13:32
  • $\begingroup$ Uranus is 3,200,000,000,000 kilometers away from eart, the swarm moves at 252000 kilometers per hour with fluctuations of 288000... that's way more than 8.6 hours $\endgroup$ – user27795 Oct 8 '16 at 13:46
  • $\begingroup$ 18 tons entering the atmosphere != 18 tons impacting the Earth. How much mass would actually survive atmospheric entry? $\endgroup$ – Daerdemandt Oct 8 '16 at 14:31

Simple. Just nuke them with everything we've got. It should be enough to destroy them.

Since they absorb energy to speed up, but have maximum speeds and temperatures, we can nuke them enough so that they are overloaded and damaged, or destroyed. Plus they might be vunerable to the EMP from nukes, causing some internal malfunction or disruption to their propulsion.

A quick google showed me an estimate of 23,000 warheads in the Earths nuclear arsenal, with an estimated yield of 6400MT, in 2009. That's a yield of 64 tons of TNT per alien, less due to losses of course but if the bombs can all be detonated at the center of the swarm (and remember they may ignore our silicon-based warheads since they are out to destroy carbon-based life forms), then quite a lot of that energy will hit aliens (no estimate on swarm density was provided). Any amount of tons of TNT is still quite a lot of energy to dump on a device the size of a mini cooper, even if its made out of high tech materials.

Each alien device can suck in energy to accelerate to a maximum of 80kms (why this, there are no arbitrary limits on speed in space, nor constant speeds either for that matter). The term "ablative" and the maximum temperature stated suggests to me that the engine will take damage when pushed beyond its max capacity. Lets look at the energy needed to do that. Assuming an alien bee is made up of solid carbon nanotubes, this'll give it a mass of approx 11tons (based on 1.6g per cm^3) from the comments. To accelerate that by 10kms requires 131tons of tnt per alien, about double the yield of our nuclear detonations, so the aliens should be able to suck it all up and accelerate without incurring damage. However, if an alien is half hollow, this explosion will push it to its max acceleration. If the alien is a hollow shell of nanotubes around some small core, like a carbon fiber mini cooper chassis with an engine, then it will have a gigantic surplus of energy to deal with. Perhaps it has heatsinks to deal with some overload, but we can see from these numbers that todays nuclear arsenal is powerful enough to provide a major issue for the aliens.

Now, assume that this scenario is set a few decades in the future, and our nuclear arsenal has doubled in strength. This is enough to impose damage on the whole alien swarm. Should we have developed even more powerful weapons in the next few decades then the potential to overload the aliens starts to look quite likely.

With Uranus being about 2.6billion kilometers away and the aliens traveling at a constant 70kms in a straight line towards us (despite space travel not working remotely like this), that's still a minimum of 14 months for us to prepare. Real orbital mechanics would only add to this figure. I'm pretty sure we could increase the size of our nuclear arsenal several times over in that time if our survival as a species depended on it, bringing vaporization of the alien fleet well within our capability.

And this is ignoring any kinds of secondary explosions or effects due to dying aliens. A chain reaction of explosions may develop.

edit: as rightly pointed out, many nuclear missles are not capable of getting to orbit. But orbit is nor required here. Most missiles are intercontinental, which is a range of thousands of kilometers. Shooting them straight up to intercept the swarm is still possible.

Summary: depending on the aliens density, our weapons technology development in the near future, and what happens when the alien bees are pushed to accelerating beyond their max speed, we can detonate enough nukes to destroy them.

  • $\begingroup$ Definitely just the heat alone turns their legs into jelly literally! If u can lock onto any of them. $\endgroup$ – user6760 Oct 8 '16 at 10:28
  • $\begingroup$ Just firing into the swarm should be close enough. $\endgroup$ – Innovine Oct 8 '16 at 11:20
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    $\begingroup$ You just made that up. No estimates of their mass is given in the question, and no indication of how much energy they can resist. However, I'll update the answer with some math $\endgroup$ – Innovine Oct 8 '16 at 11:48
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    $\begingroup$ @Innovine i did not make it up, they are the size of a mini cooper (approx volume 11.2m^3) and carbon nanotubes have a density of 1.6 g / cm^3 and their speed is 70,000 m/s. THEREFORE 1/2 * (11.2*1.6*1mil) * 70,000^2 (1/2 * m * v^2) = kinetic energy, or about 43,120,000 peta joules $\endgroup$ – Alex Robinson Oct 8 '16 at 12:16
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    $\begingroup$ @Cursed1701 I'm supporting your conclusion it can't work: I don't agree with Innovine's proposal. It ignores rocket lift capacity, targeting in space, likely number of bugs per unit area of the swarm, etc. $\endgroup$ – Nathaniel Ford Oct 8 '16 at 15:42

While beyond current capabilities, the only practical defense is to use their immense kinetic energy against them. Much like a satellite in Earth orbit could be disabled by impacting a small piece of space debris (even a leftover bolt or paint fleck in a different orbit), impact with space debris is going to do immense amounts of damage to the swarm.

Looking at the math in other answers, individual units of the swarm already have kinetic energy measured in Terra to Petta Joules. Even hitting a stationary grain of sand would vapourize the incoming unit of the swarm, so the answer is essentially dump buckets of sand in the path of the oncoming swarm.

Now since it takes years for current spacecraft to reach the outer Solar system, you can see that getting warheads into position (especially in the numbers needed) is far beyond any near term or even projected capabilities of Earth. Even SpaceX does not have the assembly line capabilities to build boosters to launch hundreds of thousands of interceptors into LEO, so short answer is "we're doomed".

However, handwaving the problem for a moment, or assuming some friendly alien gave us a heads up with a few decades to prepare, our space armada could meet them with the following items:

Using fuelling depots in orbits around Mars and Jupiter, even conventionally chemical fuelled spacecraft could reach deep space in reasonable (months to years, rather than decades) amounts of time. This is the ITS proposal that Elon Musk has raised, although in this case, we are sending missile busses.

Each warhead is fitted out with a nuclear "shotgun" shell, based on the SDI "Prometheus" project. Using a clever arrangement to direct the explosive energy of a nuclear device against a pre scored plate (much like a hand grenade), pellets can be accelerated to a velocity of up to 100 km/sec.

Up to 5 percent of the energy of a small nuclear device reportedly can be converted into kinetic energy of a plate, presumably by employing some combination of explosive wave-shaping and "gun-barrel" design, and produce velocities of 100 kilometers per second and beam angles of 10-3 radians*. (The Chamita test of 17 August 1985, reportedly accelerated a 1-kilogram tungsten/molybdenum plate to 70 kilometers per second.† ) If one chooses to power 10 beams by a single explosion, engaging targets at a range of 2,000 kilometers with a kill energy of 40 kilojoules per pellet (one pellet per square meter), then such a device would require an 8-kiloton explosive and could tolerate random accelerations in the target, such as a maneuvering RV or satellite, of up to 0.5 g (5 m/s2)

The initial plate for each beam in this Casaba-like device would weigh only 32 kilograms but would have to fractionate into tiny particles to be an effective weapon—4 million evenly spaced pellets to produce one per square meter at 2,000 kilometers range. If such pellets could be created uniformly, which is highly questionable, then, at a velocity of 100 kilometers per second, they would each weigh 8 milligrams, carry 40 kilojoules of energy (the amount of energy in 10 grams of high explosive), and travel 2,000 kilometers in 20 seconds. Such hypervelocity fragments could easily punch through and vaporize a thin metal plate and could cause structural damage in large soft targets such as satellites and space-based sensors, but they would have little probability of striking a smaller RV, or even disabling it if a collision did occur.

While pretty impressive against Earthly technology, the real purpose here is to ensure a rapid spread of pellets into the path of the swarm. Since the swarm units are moving so much faster than the pellets, they provide the kinetic energy and on impact there should be enough Ke to vapourize the unit, and indeed any units nearby in a rapidly expanding fireball.

Earth is saved! ....or is it?

The huge calculated energy of the incoming swarm is being released into high energy fireballs by the collisions with the pellets of the "Prometheus" warheads. Carbon atoms are being accelerated to incredible velocities (at the energies being discussed, we are possibly talking about nucleons and electrons moving at near light speed), and the effect of these carbon atoms moving at such high velocities is discussed in the obligatory XKCD comics here and here. The entire Solar system could be swept clean of life by the wave of high energy radiation being released by the stopping of the swarm.

Perhaps the best bet is to get out the thumb and hitch a ride out of here instead

  • $\begingroup$ Hi actually some answers incorrectly assumed that my "Bumble Bee" is made of pure graphere! which is a terrible mistake just like a submarine is made of mostly steel doesn't warrant it solid through and though. $\endgroup$ – user6760 Oct 8 '16 at 15:06
  • $\begingroup$ I do not think hitting a grain of sand would do much. The grain of sand would be converted into energy, which the bee would absorb. Even if not, and the grain of sand punched a hole clean through the bee, you now have 11 tons of dead bee heading at 70kms. $\endgroup$ – Innovine Oct 8 '16 at 17:26
  • $\begingroup$ You do not need to have the nukes in orbit, you just need to shoot them straight up. SInce most of them are intercontinental that's a range of thousands of kilometers, which is a goodly distance out into space. $\endgroup$ – Innovine Oct 8 '16 at 17:28
  • $\begingroup$ problem with grains is, swarm do not need to be compact actually, OP's do not states. Also they can form sort of protective shell from some of them etc. But at least it is answer in right direction. Problem with OP's swarm is OP, he is not aware what they capable for, solution will not work, so call me if such swarm appears, I do not know what to do against it, but I can tell which solutions will not work. $\endgroup$ – MolbOrg Oct 8 '16 at 17:57

The only solution to an improbably dangerous superior threat is improbable odds. Secondary requirements to their mission might limit them in ways that give us a chance. Ok, the aliens are here to kill intelligent carbon based lifeforms. So we know that counts as humans, and possibly a few other species on our planet.

If they care about not completely destroying the ecosystem

...that reduces some of their attack options - they can't send too many crash-bombers into the planet or everything gets wrecked from ensuing dustcloud winter. Likewise, they can't just swarm above the planet to reduce sunlight until we all freeze to death (if they don't care about taking a bit of time to do the job). Which are basically the two overwhelming options they have.

This means they have to go slower, and while they can wreck critical infrastructure as the quickest way to kill the most people (food, water, electricity, etc.), the rest takes longer as they have to find and hunt down the rest. This buys humanity some time.

If it is important that the swarm as a whole survive

...even if they sacrifice many individual units, then you have a chance to scare them off, at high cost, without necessarily having to destroy the whole swarm.

If we can develop a countermeasure in time...

So let's say we can figure out what they're made of and have time to develop something to work against them.

There's a small but dedicated worldwide group of people who keep a look out for potential objects to impact Earth - once folks see a massive swarm of small objects on an intercept course, we're going to turn a whole lot of telescopes that way (we have risky, untested plans for dealing with a large object, but not so much with a lot of small ones so it will get a lot of attention presuming we can see it in time). Even before we get good visuals, we'll probably be able to pick up that they're nearly entirely carbon by spectography.

IF we can figure out they're not natural, IF we have someone theorize they're actually carbon nano-tubes or similar materials, IF we figure out they're probably hostile, IF we start weaponizing our current technology of enzymes that break down carbon nanotubes, we might have a way of doing some damage. However, again, if the aliens care about preserving the rest of the ecosystem mostly, we get a lot more time to work with.

How to deliver these enzymes? Given that the aliens move ridiculously faster than even our newest railgun technology, it's less about targeting them than blanketing as much of the atmosphere with these enzymes - which means modifying bacteria to produce these enzymes and letting them fill as much of our airspace as we can.

Presumably these aliens survive slamming through tiny micrometeors in space, so I doubt the breakdown of general surface damage will do much, but once the enzymes hit the lower layers, the whole unit might come apart as it travels through the atmosphere. At high speeds, that's going to be messy. At lower speeds, the units might simply disassemble.

If the anti-matter sections are built of different material and fail-safe instead of fail-dangerous, humanity gets a tech boost out of the whole affair. Otherwise we get a bunch of antimatter explosions. Crud.

Now what?

Again, assuming the swarm cares to survive, here's possibilities:

  • Swarm members who haven't entered the atmosphere, will not for fear of contamination. If they have some kind of means of communicating back home, the planet is marked "contaminated" and either left alone or a different, more horrific weapon is sent (over the course of centuries or longer travel time). If they don't have a means of communicating that far, maybe they send a few to fly back, and the rest monitor the infected planet.

  • If they all have entered the atmosphere (to speed up the hunt), then they're all potentially infected with the bacteria, and may attempt to leave some kind of warning to future aliens to not come here. Perhaps some kind of massive last strike to carve up part of a continent with a symbol or sign. Or they get back to orbit and smash that sign into the far side of the moon.

However, that's a whole LOT of if's to get here. Given that the aliens don't have FTL travel, they would probably just have the drones slam the planet or sunblock it to either a) kill for the sake of destroying potential future rivals or b) by the time they come around for colonization proper the ecosystem has recovered/evolved.

  • $\begingroup$ +1 for the link, most valuable part of answer very exciting link, rest is so so, except ending $\endgroup$ – MolbOrg Oct 8 '16 at 18:04

No, Mr. Human, I expect you to die.

TLDR: you can't defend the Earth, a 'relatively' stationary, known target. In warfare this is known as 'unprepared ground': current technology does not have much defense against a single 'killer asteroid', nevermind a hundred million of them. Note that even summing all active, reserve and paramilitary forces on Earth, you don't get to a 100M number, so assuming the bees are so kind as to fight hand-to-hand, we'd still be vastly outnumbered and out-gunned (since they are the equivalent of miniature tanks).

There are alternative strategies, though, with correspondingly devastating losses.

Play Dead, Convincingly

Humans can't really nuke a swarm of asteroids: they lack the rocket lift capacity, and even with a year to develop it, lack the ability to maneuver warheads in such a way it could reliably destroy enough aliens with each precious warhead to stop an invasion cold.

On the other hand, we have plenty of capacity to nuke ourselves. And, moreover, it would only take one nuclear-capable country to kick off the party. Humans can burrow down, build bunkers and shelters and other ways of hiding - probably as distributed and as difficult to detect as possible. Once you get a sizable (5%?) of the population in such a situation you start WWIII. From the bee's point of view, this is a bit of a Seige of Masada, but they then have the choice of how much energy they're going to spend digging through a nuclear wasteland to determine if there are any survivors. (This is assuming, of course, that they don't just rain down destruction from above, in which case any defense is moot). Presumably, at some point, it will be diminishing returns for them to keep searching and they move on. (If they are never going to move on, again this is a moot point.)

You could hold off on the war until the bees were in atmo, so as to take a few with you. Also, while it would be dodgy, building deep underwater might make it difficult for the bees to come after and/or detect the bunkers, depending on specifically how they propel themselves and do detection. Or it might make it easier for them to compromise bunkers if underwater operations are no problem.


Assuming the swarm is staying relatively close together and immense resources were capable of being managed (which is a practical blocker to this plan - retooling the economy will not be easy), a handful of space craft could be built that might, possibly, maintain human life against the vagaries of the void. Build as many as you can, and a whole bunch of dummy or suicide life boats (with a handful of human sacrifices onboard to make it convincing). The real ones should be launched in a trajectory that puts the Earth between them and the bees, so as to best conceal the retreat. The others in all directions, including into the swarm (to see how they react, and what weapons might exist). Maybe pop off a few nukes or other distracting things in order to make it appear that Earth is going to put up a fight and draw attention from the escaping humans.

A variant on this plan include an out-and-back trip for humans to come back to Earth after, presumably, the bees have left.

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    $\begingroup$ not bad, harsh. May or may not to work - depends on their algorithms. I guess will not work. I would recommend to try to put some people to moon and venus in that type of plan. First seems not very rich with easy carbon, second have lot of carbon as disguise. If they for carbon - venus will not stand, moon may. If they for live depends which boundaries are set for live and how they detect it. $\endgroup$ – MolbOrg Oct 8 '16 at 18:18
  • $\begingroup$ I agree the chances are slim: but any direct resistance is equally slim. The odds as stated are catastrophically against humanity. And a lot does depend on the differential valuation the bees have on things. $\endgroup$ – Nathaniel Ford Oct 8 '16 at 18:21
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    $\begingroup$ direct resistance without proper tech, yeah no chances. And too little time to invent, of course if government have candy for kids in their pocet, like star gate city in antarctica which they investigate atm(may be :)). But potentially in 50y may emerge technology which may deal with that kind of threat easily, also based on carbon nanotubes. $\endgroup$ – MolbOrg Oct 8 '16 at 18:33

Each one has kinetic energy of about 2.4 terajoules. Since there are a hundred million of them, the total energy is about 240 exajoules. A megaton is 4 petajoules, so the total available energy is about 60,000 megatons. That's 300 Krakatoas or ten times the Earth's entire current nuclear arsenal. I don't think we can defend against that with 21st century technology.

  • $\begingroup$ its a lot more energy than 2.4 terajoules, E = 1/2MV^2, i got a bit over 43 million peta joules :/ $\endgroup$ – Alex Robinson Oct 8 '16 at 11:15
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    $\begingroup$ When using multiple numbers in the same portion of text which you are wanting people to compare, it is best to use exactly the same units, even if that means you need to use exponents (e.g. 10^4, superscripts are not available in commnets). Most people are generally poor at having a feel for the difference between the various (SI prefixes](en.wikipedia.org/wiki/International_System_of_Units#Prefixes), particularly when you use ones other than kilo, mega, giga and tera. $\endgroup$ – Makyen Oct 8 '16 at 15:27
  • $\begingroup$ 70000 m/s and 3141kg == 7.69545e+12J kinetic energy $\endgroup$ – MolbOrg Oct 8 '16 at 17:08

You have a little under 2 years to prepare. Get as many ships as possible spaceworthy (old shuttles, new drones, ICBMs, etc...) and load a nuke and carbon lifeforms into each. Launch them early and send them as fast as possible towards the swarm. Don't shoot them, let the swarm converge and overwhelm, and blow all nukes at once when they are in the radius.

Meanwhile on Earth, get all military on the planet to deploy as many ground to air and space based defenses (railguns, flak, missiles, etc...) as possible, and decentralize your entire control structure, so that you are not automatically KO if they disrupt satellite communications. Prepare a global ground based targeting network and plug it into the decentralized control. You can also launch a lot of dirt, sand, gravel, scrap metal, etc from space. It will form a wide, almost invisible cloud of debris slowly moving toward the fast moving swarm. A single shovel of dirt impacting a drone at 50KM/s is probably enough to destroy it and create more debris, destroying more drones, starting a chain reaction.

Then just wait. Hopefully the nukes will destroy a large portion of the swarm from the direct blast. Since carbon nanotubes will either act as a metal or semiconductor depending on nanogeometry, there is a very good chance that your "solid" CNT drones are their own brain, with the outer layer of the hull acting as a kind of nerve termination network, carrying information to the core, the protected "thinking" brain. If that is the case, a whole range of energy weapons will EASILY disrupt them, and the EMP from a nearby nuke will very likely knock them "unconscious", if not kill them instantly.

The dirt cloud will help break down more, and hopefully your ground to air and space-based defenses will be able to intercept what remains, or at least enough that you can avoid extinction. Hope for the best.

This will let you defend from an attack, but your only chance at long term survival is to figure out how to rewrite their core protocols, otherwise more drones will come. Capture a minimally damaged drone, somehow, and reverse engineer it like your life depended on it (it does).

  • $\begingroup$ starting a chain reaction. - not happening, shovel of dirt maybe destroy one drone, roughly it will create 2 imaginary shovels of dirt with speed 2 times less then first one - this is kinda best scenario which will not happen of course. Ok all u shuttles missiles 400 tonnes of dirt, that is about 100 cubic meters of it - I think is will be significantly less then 1 million of shovels of dirt. Altrough good guess about brains, u guessed it, but it is not so easy to know them down, disrupt for sort time when close to it, may be, but programming is kinda hardware, will reset pretty fast. $\endgroup$ – MolbOrg Oct 9 '16 at 3:26
  • $\begingroup$ The point is, they are functioning on the same electronic principles as we do, they are just replacing our 2D microgeometry with a 3D nanogeometry, which is more efficient, faster, and uses less power. However that also makes them far more sensitive to perturbations in the EM field. This can be a good thing for sensors and targeting, but it is a fatal flaw that an EMP will absolutely tear through. It will physically destroy memory structures. If you want them to be protected for this, then you need to add a strong EM shield. $\endgroup$ – Drunken Code Monkey Oct 9 '16 at 3:44
  • $\begingroup$ Carbon nanotubes are also very weakly magnetic (around 22 times less than iron, and ONLY in presence of iron impurities), so in order to produce a strong enough EM field to protect your electronics, you will need some other material to form coils, reflectors, etc... $\endgroup$ – Drunken Code Monkey Oct 9 '16 at 3:55
  • $\begingroup$ The point is, they are functioning on the same electronic principles as we do, they are just replacing our 2D microgeometry with a 3D nanogeometry - I understood that, Next step to go from discrete logic to something more robust - just because they are exposed to radiation who knows for how long, and if there is live on such planets like Jupiter in artificial constructions - bet they should be able to deal with those level of high energy particles and radiation. Next step to make them more robust against solar flares, stars are different and our sun not the worse case. $\endgroup$ – MolbOrg Oct 9 '16 at 4:58
  • $\begingroup$ And u get processor that works when u cut it in half, and resets back after intensive EMP. I even do not talk that EMP from nuclear blast is not so big and more distant target is less strength/effects of EMP wave ~1/distance^2. More sensitive to EMP is also not the case(tl;tw) Faraday cage works not because of metal - but because currents induced in conductors by EMWave and that current generate own EM which cancels presence of external EM inside cage. CNT seems good for the job. and you may order 3D structure of processor itself(cage inside cage...) to help, which is not possible with 2D $\endgroup$ – MolbOrg Oct 9 '16 at 4:58

Send spaceships with sacrificial humans to divert them.

How far do swarms break off? If not astronomically far, it's plausible that the whole swarm will divert to kill a lone astronaut or a small group.

We can take advantage of that and send many suicide missions, engineered to keep them running around. Our best minds can abuse slingshot maneuvers to have the ships divert the bees from other ships multiple times.

This may well be sustainable, i.e., we may be able to do this forever, launching new ships to replace the ones taken and the ones that run out of supplies, with enough redundancy and flexibility to absorb contingencies.

And how smart is "intelligent"? We might be able to make do with monkeys and dolphins.


Short version: Simple. Send out a single nuke to one of them. Make sure that there is no direct line of sight to earth. Done.

Having no weapons means they absolutely have no defense against nukes. A nuke reaches 10^6 C. No material can withstand that temperature. Definitely no carbon nanotube can stop that explosion. Nuke will disintegrate first couple of bees, which contain antimatter which would be left without a container. This will spew extreme amounts of damage in X-ray, which would probably disintegrate even more bees. This will continue until there are no bees left in the swarm. If there is a line of sight to earth that might be enough to permanently change the life on earth. It won't be enough to make humans go extinct.

Even if previous method doesn't work, humans will survive. I don't think they can carry enough antimatter (I know how much power they hold) for the task. Rooting humans out of earth requires them to destroy earth. Nothing short of that would cut it.

  • $\begingroup$ but they are ~450 days away, they will see it coming surely? $\endgroup$ – Alex Robinson Oct 8 '16 at 17:15
  • $\begingroup$ So what? They have no weapons and they are slow. $\endgroup$ – Cem Kalyoncu Oct 8 '16 at 17:27
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    $\begingroup$ 70 kilometres per second is not "slow", 70km/s objects are difficult to hit with a nuke $\endgroup$ – Alex Robinson Oct 8 '16 at 17:28
  • $\begingroup$ There is nothing to suggest that they will pay any attention to our technology floating towards them, as long as there is no carbon based life on it. $\endgroup$ – Innovine Oct 8 '16 at 17:29
  • $\begingroup$ We have juno accelerated to 40km/s with 0.5% of US budget. Now survival of the humans depends on this, I think we can easily put 200% of US budget for this project. I think best bet is to place a railgun to space. On earth we can do 50km/s, in space it would be much better. We have enough nukes to cover a large area if they are to maneuver. $\endgroup$ – Cem Kalyoncu Oct 8 '16 at 18:06

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