Why Aliens Wouldn’t Be Hostile

Many people think we should avoid contacting aliens because they’ll be hostile to us. I hear this everywhere, from folks in my roleplaying group all the way up to geniuses like Stephen Hawking.

For the moment, this is a purely theoretical question. If there isn’t intelligent life in our corner of the universe, then it won’t matter if we think contact is a good idea. But it’s entirely plausible that we might receive a signal someday, and it’s disheartening that so many people think we shouldn’t answer. We have every reason to think aliens would be peaceful.

Reaching the Stars Requires a Peaceful Society

When discussing what aliens would or wouldn’t be like, we have little choice but to use humanity as a model. Flawed as this approach is, it’s the only one we’ve got right now. From looking at humanity’s bloody history, many have assumed aliens would be inherently violent. This position is understandable; humans often do terrible things to each other, and we have plenty of evidence that competition is needed for advancement.

But if we assume that aliens will follow a similar path to humans, that actually makes them less likely to be violent. Violence among humans has been on a steady decline for at least a century, both in war and at the individual level. That may not feel true from watching the news, which seems more violent every day, but that’s an issue of reporting bias. We’re getting better at reporting violence, and so it seems like there’s more. At the same time, headlines about violence are more attention grabbing than headlines about people living peacefully. This is probably why Americans are afraid of terrorism but not traffic accidents.

The reasons for our decline in violence are myriad, but a major factor has been the increase in our destructive capability. As our weapons become more and more powerful, war stops being a valid option for material gain, because whatever you’re trying to get will be destroyed in the process. Humans have barely dipped a toe into space, but we’ve already reached a point where most of our powerful nations simply cannot risk going to war with each other.*

Aliens capable of reaching us would be far more powerful. They might not all be fun-loving party animals, but they would never have survived to leave their solar system if they didn’t know how to solve problems without violence. It’ll be interesting to see if we humans are capable of making that leap.

All Resources on Earth Exist Elsewhere

Another common fear is that aliens would want to crush us, not because sapient creatures are inherently warlike, but because the aliens will want our stuff. This fear also seems reasonable at first glance. Most conflicts in human history have been about resources, with moral justifications added afterwards. Aliens could easily do the same thing.

Or they would, if there was anything remotely special about Earth. This might be a blow to our human egos, but nearly anything found on our planet can be found elsewhere. Iron, water, diamonds, the list goes on. Extra terrestrial bodies are teaming with resources, many of them much easier to extract than what we have here. Our synthetic materials are even less likely to interest spacefaring aliens, for the same reason modern humans aren’t in a hurry to replace their smart phones with telegraph stations.

Even if a hypothetical race of aliens were so into mega-projects that they managed to use up the resources in their home system, there are countless star systems in our galaxy alone that don’t have a human infestation. Unless the aliens are coming from Alpha Centauri, it would be far easier to visit an uninhabited system than to come here.

Think about it: if you were presented with two soda cans, one of them covered in ants, you’d take the one without ants right? You could brush the ants off, but why bother when there’s an ant-free can right in front of you?

Crossing Space Means You Can Live in Space

While none of the Earth’s resources are unique in the cosmos, or even rare, there is one quality that makes our planet special: it supports life. It’s the only planet we know of that does. So maybe aliens would want to conquer our planet so they can have more living space for their growing population? That’s certainly the plot of more than a few scifi stories.

This concern requires that any aliens we meet can actually live on Earth, but that’s certainly plausible. For all we know, only planets with conditions similar to ours can support life. Even if the aliens can’t live here, Earth might be more like their homeworld than lifeless bodies like Venus or Mars,* and so it would be easier to terraform.

That sounds pretty grim, until we consider that before any aliens try to move in next door, they have to get here. If they can travel quickly between the stars, that means they have faster than light (FTL) technology. Modern physicists are divided about whether FTL is possible at all, but if it is, it will require energy expenditures on a level that is difficult for humans to conceptualize. Any civilization advanced enough to produce those levels of energy could just live in space.

Space habitats aren’t that hard to build. We can make them right now, it’s just expensive to send so much mass into orbit. If we could harness the energy needed to travel faster than light, we’d be building Dyson Spheres in a second. FTL capable aliens would have so much orbital real estate, the idea of flying all the way to Earth would be laughable.

Alternatively, aliens might take the slow way, crossing the interstellar void in huge generation ships. That’s an unwieldy way to launch an invasion, but it’s possible. But if they can survive for centuries in space, what reason do they even have to land on Earth? They’ve clearly mastered the art of living in the vacuum, even without the god-like technology of FTL.

We’d Be Terrible Slaves

There’s one thing we know for sure that only Earth has: humans.* Perhaps inspired by the human predilection for enslaving each other, some people think aliens would see humans themselves as a resource. Isn’t that a good reason to be scared of aliens? No one wants to get sent to the spice mines of Kessel after all.*

I’m afraid that once again, I must chip away at our sense of specialness. You see, humans just aren’t that good at working, at least not compared to robots. We’re close to automating all human labor ourselves, and that’s with puny homo-sapien tech. Compared to sleek, sexy robots, we humans are weak, fragile little monkeys that require constant food and access to toilets just to stay alive. Plus, any alien who kept a stable of humans would have to deal with constant escape attempts. Not worth the effort.

Then we get into the more exotic uses for humans. Maybe the aliens are mind-worms who need a host body to live. Or maybe they’ve just developed a taste for our succulent livers.* Either option is possible, anything’s possible with aliens, but why bother coming all the way to Earth when hungry aliens could grow their own humans at home?

In recent years, we’ve taken huge steps in the development of artificial wombs. It’s likely that some time soon, we’ll be able to create humans in a laboratory, no pregnancy required. Spacefaring aliens are almost certain to have far superior biotech, and any human-related needs could easily be satiated at home. Certainly it would be easier than crossing the vast distances to Earth.

Aliens Would Know We’re No Threat

A final reason people often give to support fear of aliens is the idea that they would want to preemptively destroy us. Better to take us out now while we’re helpless than risk humans growing in power to rival them. That certainly sounds like a reason to be afraid. If aliens decided to launch a preemptive strike, there’s little we could do.

Except everything I’ve been saying about aliens applies to humans too. By the time we’re able to travel the stars, we’ll no longer have any need for conquest. Advanced aliens would figure that out. They’d have no reason to launch a first strike. They’d know that in time, humans will either self-destruct or figure out our problems and become less terrible.

Assuming aliens would launch a first strike is a paradox. It requires that aliens be intelligent enough to build interstellar weapons, but not intelligent enough to realize humans are no threat to them. We should give ET a little more credit.

I can’t say with absolute certainty that aliens wouldn’t be hostile. No one can say anything about aliens with absolute certainty. The universe is a strange and wondrous place, and clever scifi writers are very good at finding unlikely edge cases to make their evil aliens seem realistic. But by the same token, I can’t be absolutely certain that the grocery store clerk won’t stab me next time I buy food. I go anyway, because the benefits far outweigh the risks. The same is true for aliens. Just finding out that we aren’t alone would completely change how we view the universe. And imagine if they decided to tell us stuff. Technology that seems trivial to advanced aliens could completely revolutionize life on Earth. We need to get over our fears now, so that we don’t miss the opportunity, if it ever comes.

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  1. SunlessNick

    Unless the aliens are coming from Alpha Centauri, it would be far easier to visit an uninhabited system than to come here.

    And even then, it would be easier to mine asteroids, comets, and the moons of gas giants than Earth.

    For all we know, only planets with conditions similar to ours can support life.

    There are good reasons to think so, at least when it comes to life as complex as ours.

    But if they can survive for centuries in space, what reason do they even have to land on Earth?

    By the time they get here – especially if it is a journey of literal generations for them – living on a planet may seem positively weird to them. The novel Footfall referred to this (though it didn’t explore it in a *lot* of depth) – the invaders came in a ship that was mostly sleeper, but with a small generational crew to maintain it – but by the time it reached Earth, the latter didn’t care about invading it at all, and only went along with it because they were outranked.

    Spacefaring aliens are almost certain to have far superior biotech, and any human-related needs could easily be satiated at home.

    From a technological standpoint, yes, though understanding of human biology is likely to be the one thing we have a good chance of being better at than them – cf one of the common tropes of benevolent aliens offering us awesome medicines rather than, say, awesome battery technology. On the other hand, it’s hard to imagine a human-related not that’s not better met by something that evolved on the same planet as them.

    Aliens Would Know We’re No Threat

    There’s a brief arc in Farscape where the characters find their way to Earth, and Aeryn Sun (a soldier from an interstellar power) is interviewed on TV about the danger of alien invasion.
    And her thesis was essentially that neither Earth nor humanity offers anything anyone don’t already have, and Earth is too primitive to be regarded as a threat or worth cultivating as an ally. So *could* any of the various galactic powers destroy or enslave humanity? Yeah. But it’s not worth it.

    (The talking heads really didn’t appreciate her perspective).

    • Michael

      On the last, in a perverse way it makes us feel important to think aliens would invade Earth. Aren’t we special?

      • Grey

        In one webcomic, Earth’s value on an interstellar level lies in being a tourism destination, and their most valuable export being their media. (And around the Age of Sail, they did recruit humans for crews like how people were recruited as sailors).

  2. Cay Reet

    This reminds me a little of the ‘we are space Australia’ thing on Tumblr.

    • SunlessNick

      You mean aliens don’t come here because a ridiculous number of things on our planet are poisonous?

      (This reminds me of a theory about the invaders in Signs. Taking their apparent plan of “The surface of this planet it 70-ish% deadly acid – but don’t worry, deadly acid flows and pools around on the rest of it too – and sometimes deadly acid falls from the sky. The local creatures need deadly acid to live – and usually keep supplies of it close at hand – their bodies are lagely composed of it. Let’s invade unarmed and naked!” and concluding that they’re obviously that civilisation’s equivalent of drunk fratboys saying Hold my beer and watch this)

      • Cay Reet

        I personally think that they see us kill each other off in high numbers and think ‘we don’t need to run that risk.’

  3. Thane Bonnett

    I agree that peace is the most stable and likely situation. As you said in your article on empires, modern civilization has learned that it is cheaper and easier to purchase resources than to seize them.
    However, for peace to end wouldn’t require everyone to suddenly forget the lessons of history. It might only require a single rouge actor.
    “The Parable of the Tribes” explores how in a system of peaceful actors, aggression on the part of a single rouge actor can force all peaceful actors to take steps to prepare for conflict; inducing a positive feedback cycle of suspicion and hostility: “force can only resisted with greater force.” .

    This is how the European peace established at the Congress of Vienna eventually eroded, and it all blew up as the result of nonstate rouge actors and poor communication among mutually suspicious states.

  4. American Charioteer

    Before WWI, military planners believed that the next war would be won by whoever mobilized the fastest. Thus, even mobilizing was seen as akin to an act of war, and something as benign as building railroads was a threatening action. Unfortunately, this may parallel the situation that would exist between alien actors, as the technology that processes resources for peaceful purposes will look identical to technology that processes resources to produce war material. The biggest step of mobilization (recruiting soldiers) can be entirely skipped if wars are fought by unmanned craft, and so any expansion may be seen as military expansion.

    Cixin Liu’s “The Dark Forest” trilogy explores this exact idea; proposing that aliens live in constant fear of each other because they never know who will experience an unexpected leap of technology and decide to become a rouge actor.

  5. American Charioteer

    Interestingly, Harary’s proof shows that in any in a system of actors that contains aggression; every Nash Equillibrium state (state where no one can unilaterally improve their position) is a division of the actors into exactly two factions. (This video provides an excellent explanation: ). This is a rather intuitive result and explains why stable tripolar systems of states or wars with three groups of combatants are rare. Though it doesn’t preclude an equilibrium with no hostility at all, again we see that only a single rouge actor is required to disrupt the equilibrium.
    A powerful alien civilization is likely to know this and thus may attack weak civilizations preemptively to prevent them from allying or sharing technology.

  6. Deus Ex Anthropos

    If a single actor disrupted the zero-hostility Nash Equillibrium state, wouldn’t the others states unite to stop it? The two factions would be all-previously-peaceful-states vs the single rogue player.

    • Thane Bonnett

      In a human system, yes. In fact, that is the point of international law and international organizations: to serve as a force of negative feedback in the zero-hostility equilibrium state.

      However, this requires pre-existing friendly relations between all actors (to get to the zero-hostility state in the first place), and that requires both communication and cultural understanding. Both of those things are difficult from lightyears away, between beings who may have completely different biology and psychology.

      • American Charioteer

        Oh, you reminded me of something: laser light meant to interfere with communication or cause direct damage travels through space at the exact same speed as laser light used to communicate. The cosmic speed limit puts us back in the days when messengers couldn’t move much faster than armies.

        • Deus Ex Anthropos

          I guess the existence of lasers and the fragility of our ecosystem makes flying saucers a bit ridiculous.

          • American Charioteer

            If you mean that combat in space would likely mostly occur from extremely long distances with lasers and AI-guided missiles, then I agree. It also means that space dogfights would be boring to watch.

  7. JXMcKie

    You forgot the most important argument for alien hostility…they would want to carry away our womenfolk, so the alien scum must be taught a lesson by the muscle-bulging hero with his trusted blaster Joking aside, yes it is really bad news for dramatic Space-Opera´s, (but good news in the real world) that it is so difficult, to find a logical reason for conflict between teoretical alien civilzations and us. As a Sci-fi author, one has to cook up some good explanation for such a conflict. That being said, it doesn´t mean conflict is totally unthinkable…some of the better explanations are presented in Babylon 5 two “elder” species, Vorlons and Shadows, using their younger “client” species to settle a philosophical arguments, by slugging it out. Or even more scarry : The Reapers from the Mass Effect trilogy ! The endings might divide fans of Mass Effect and there is certainly a problem with logic of those endings, but the premise of the Reapers cyclic annihilation of all highly developed sentient life, was perhaps not so farfetched after all…
    …and let´s hope that it is not the case, but conflict makes for more dramatic story !

  8. actualethere

    “No one can say anything about aliens with absolute certainty.”

    I can say this with absolute certainty. Both hostile, benevolent and ambivalent ET civilizations exist and have been interacting with Earth and or Earth humans from the get-go.

    Additionally, the variety of species hang on a spectrum of what we would call ESP and communicate telepathically. Some are powerfully psychic and some seemingly not at all. Add this spectrum crossing the “benevolent-malevolent” axis and things start to get interesting, if also confusing.

    here is an important question: Are earth humans benevolent? or malevolent?

    The answer should stop short with some obvious needs for clarification, definition of terms and a epistemological “conversation about the conversation. ”

    The answer, as almost always, is “it depends”.

    Even when benevolent, we know what the road to hell is paved with and sometimes a summer feast can lead to famine if birthrates exceeds a species ability to remain sustainable.

    likewise malevolent intentions or negative circumstances can produce unexpected consequences that turn out to be positive or strengthening.

    all that said, we don’t make terrible slaves and in spite of use of clones as biological machines, often times humans are used as technicians, inventors, engineers, ect throughout the galaxy.

    AI machines, as Frank Herbert and others suggest, turn to be more problematic than anything.

    So are we a threat? Well, the small but powerfully equipped minority that exists in compartmentalized secret space programs certainly can be seen that way, depending on the ET civilization that is looking at us.

    Some would see a threat, others not. Depends on how you define “we” when these compartmentalized top-tiers of the deep-state aren’t exactly regular, rolly-polly humans we would define the term.

    At some point the breakaway civilization is the fork in a bifurcation of a species and our definitions of who We are start to get fuzzy.

    Could earth humans themselves be an “alien threat”?

    anyway, your conception of what ET life is like, what they would or wouldn’t do/make/say/think is restricted by the aperture of your worldview, to say nothing of your level of consciousness. It doesn’t matter how smart you are, if your frame of reference is being manipulated and crucial information is being withheld, you won’t see much beyond what you are allowed.

    A tiny peephole into a titanic hall, full of dangerous treasures and their guardians.

    To open that worldview that has been artificially narrowed, forget anon comments in a fiction thread and go listen to NASA astronauts speak about the issue. They are fairly plainspoken about what they know regarding intelligent non-human life interacting with earth and their people.

    The truth is not “out there” it’s right here. Buried just beneath your fear of looking like a fool.

    • Leon

      Love it. Makes me think, Mulder and Skully vs Cthulhu.

  9. carl

    ‘violence has been declining for at least a hundred years’

    A quarter million years of history, and a 100 years of peace- that includes two world wars. That doesn’t seem like good data to use in projecting a trend. I actually buy most of the logic in that section entirely. While isolated to this planet, it makes no sense to engage in destructive behavior that would destroy anything worth fighting over. But how many nuclear powers have committed troops to wars since WWII? I”m guessing it’s a large percentage of the total number, and I know the US and Britain, and France, ect ect have done so multiple times.

    In short, the restraint required for survival doesn’t seem to requires anything resembling perfect peace.

    • Cay Reet

      Day to day violence might have decreased over time, the more our society (whichever one that might be) frowns on it and punishes it. As a species, we will always be violent, because we’re omnivores and prepared to hunt and kill to survive. The question is which outlets we have. War with our neighbours is an outlet. So is a football match. So is a violent video game. So is a violent movie. All those other outlets than war allow us to project our aggression on something or someone and get rid of it. Watching an execution in the middle ages was just as much an outlet as really hitting or killing someone.

      Wars are not fought for violence as a such, they are fought because at least one side wants something and at least one side doesn’t want to give that something up. It might be influence, it might be land, it might be a person (Helena of Troy, anyone?). Wars are the last tool in the toolbox of diplomacy and always were and always will be.

  10. Guy Srinivasan

    > When discussing what aliens would or wouldn’t be like, we have little choice but to use humanity as a model. Flawed as this approach is, it’s the only one we’ve got right now.

    This is not just false but obviously false. Also, a very dangerous mistake. Good thing geniuses like Hawking aren’t making it!

    • Oren Ashkenazi

      For the record, Hawking specifically uses the parallel of Europeans and Native Americans to make his point about why humans shouldn’t contact aliens.

    • Guy Srinivasan

      To clarify: I do not object to using humanity as a model. I object to saying it’s the only approach we have, and even worse drawing conclusions from the premise “somehow I know there is only one way to approach this problem”.

  11. Deana

    Sorry, but your premise is flawed from the get go. Violence at the Intersocietal level has never been greater than in the last 125 years. Just a very incomplete list will demonstrate the fallacy of comparing intrasocietal declines in violence to international and intercultural increases. Boer War (first use of concentration camps), World War 1 (including Armenian Genocide), Ukrainians Famine/Genocide, World War 2, Korean War, Vietnam, the Killing Fields, Guatemala, Nicaragua, Rwanda, Eritrea, South Sudan, East Timur, South Africa, Nigeria, Iran-Iraq War, Somalia, Gulf1,Balkans, Gulf 2, Afghanistan, the Rohingya, and that is just a representative list. Since 1850 there has been a major war, usually including genocide, or religiocide, somewhere on the planet, every day. Violence is not decreasing. Our lack of empathy with the other has.

    • Cay Reet

      It is impossible to list all wars in Europe during the middle ages, because quite some were over in a battle or two and because there were too many. As far as religiocide goes, have you heard about the early inquisition? When they were only going for herectics and before they went for witches? Or about the witch hunts? Genocide has happened in the past as well, in more cases than we know of for sure these days, because we have no traces left of them.

      It’s not known how many wars were fought in both Americas, because all written data the Native Americans in north and south might have had were destroyed or are simply no longer readable, because the knowledge of the languages used has been destroyed. Not to mention the cultures and their spoken memory have been destroyed – by the European conquerors starting around 1490 AD. Same goes for Africa, another continent ‘conquered’ by the supposed ‘better’ races and used up for resources long before the last 125 years.

      Wars have happened among humans for a long time, but modern times have heightened the amount of deaths in a single war, due to the weapons used (especially all kinds of weapons of mass destruction). We do not know whether concentration camps of a sort have been used in ancient times, because we have no reports of them. That doesn’t mean they didn’t exist. As a matter of fact, knowing humans, it’s quite likely members of a people someone was at war with were most likely locked away (concentration camp style) or outright killed.

      And if you think modern humans are less emphatic than those who thought a different skin colour meant you could kill and torture others at will… Slavery is still around today and it’s important not to forget or ignore that, but it was going on at much higher rates in the past. And it was considered much more normal. In most countries of this planet (yes, even in Europe and North America), slavery today happens in the underworld, in criminal surroundings. They call it trafficking, but it’s the same thing. However, you can’t just walk onto a marketplace and compare the twenty female slaves on sale for their uses in your household or on your fields, as if they were working horses. If you ask me, that’s actually a big step forward for our empathy with other humans outside of our society.

      Humans have always been aggressive, but that doesn’t necessarily mean alien races are as well. Given we are too much at each other’s throats to actually get some kind of manned space travel beyond the reach of our own moon going, I dare say no alien race as aggressive as us will have had a decent chance at mastering space travel, either, before they destroyed themselves. That means any race which has has either never had that level of aggression or they have learned to control/conquer it. In both cases, they would not come as conquerors.

      • Leon

        I agree with you. But, what if interstellar travel turns out to be unexpectidly easy and an unplesent alien species (like us) manages to achieve it before they become civilised? Just look at everything weve managed to achieve. and were horrible.

        • Cay Reet

          Well, humans are clearly space orcs.

          Therefore, I dare say we’d actually stand a better chance to get along with them than possible other alien species, because we’d ‘get’ them.

          • Leon

            Thanks for the link.
            Years before I read Ring World (though I was probably “inspired” by something else), I had the idea of aliens agonizing over recruiting humans as a foreign legion. But I couldn’t come up with a threat that would drive them to such madness.

          • SunlessNick

            A couple of those articles make us sound more like space-hobbits.

      • Sedivak

        I disagree with the notion that only (relatively) peacefull civilizations can develop serious space travel. I’d say that space travel would be an excelent tool for expansion and military dominance. Thusly motivated civilizations may make great technological strides while still remaining warlike – think Expanse or Revelation Space.

  12. Mitchell McDonald


    It is overwhelmingly likely that an alien species that can travel the stars AS A WHOLE would be fairly peaceful if not at least neutral to any primitive species they may meet (namely us)…


    If a group of alien CRIMINALS or aliens with vastly different morals or goals than their species as a whole were to get lost and land or crash on Earth or come here on purpose for some reason, who knows what their intentions for us might be? Wonder if they are low on supplies from running away from alien authorities or the crash destroyed most of their means of survival?

    Plus, wonder if the aliens that landed WERE peaceful BUT they crashed or ran out of supplies on their way here? They probably wouldn’t be any threat to humanity as a whole or WISH any harm to us, but if they were DESPERATE ENOUGH I would sure not want to test if they would or wouldn’t value THEIR SURVIVAL over a “primitive” human family in a house nearby with plenty of food and supplies for the taking, especially if some of them are hurt or some humans see the crash and attack the aliens out of fear. Consider this: If you survived a plane crash out in the middle of the wild and saw a pack of animals with a hoard of food they were protecting or if they attacked you, would you think twice about killing them for you or others’ survival?

    • Oren Ashkenazi

      Editor’s note: I’ve removed a small section of this comment to avoid unfortunate racial implications. The rest of the comment is fine, but I urge everyone to consider the possible meanings when comparing real humans to hypothetical aliens.

      • Mitchell McDonald

        I simply was using the unfortunate constant terror attacks and danger in the area of the Middle East as a comparison to the rest of the world as an example that although we may be a very peaceful race as a whole, there are people out there who are anything but. The majority of people in the Middle East aren’t violent, let me make that clear.

    • Mitchell McDonald

      ALSO, wonder if the alien society’s technology gets so advanced that a space travelling vessel capable of reaching our planet becomes as cheap as a used car and practically ANY OF THEM (criminals, individuals or groups with more sinister morals than the majority, or an inexperienced or lost alien (think teenage driver)) can easily land or crash here with little effort?

      • Cay Reet

        I dare say that’s unlikely. Distances in space are huge and even if the vessel were relatively cheap, there would be a lot of fuel of whatever kind needed to get to us. It would basically be as if you drove your car from east to west coast (or the other way around) just for a bagel. Some might consider that, but it would still be expensive and would probably take rather long. There are probably more interesting worlds to crash on closer to those aliens.

  13. Joe

    The trouble with the “all resources are found in space” is that, from the aliens perspective, we might as well be a lifeless world anyway. We don’t have antimatter cannons or relativistic kill weapons or whatever uber-weapons aliens have, so there’s no chance of MAD. If they have FTL travel, we have no chance of meaningful resistance at all.
    The energy and labour difference between strip-mining earth and strip-mining mars is effectively non-existent- a few barrages to level our cities and vaporise our missiles, maybe. Negligible energy costs to a species capable of breaking light speed.

    To extend your analogy, if a logging company has a choice between cutting down the tree with ants on it or the tree without ants on it- well, they don’t care either way which one they go for, as long as a tree gets cut down. It’s not like the chainsaw can’t go through ants.

    • Oren Ashkenazi

      For one thing, sterilizing Earth, or any planet, is likely to have a resource cost greater than zero, so that’s a reason to go for uninhabited planets instead (assuming it even works out to mine planets rather than asteroids, which are much easier to retrieve resources from since you don’t have to fight gravity to lift off).

      Even so, it’s certainly possible for there to be an alien species that is consuming resources at such a prodigious rate that Earth still makes sense as a target, anything’s possible with aliens (though if such a species were anywhere nearby we’d likely have seen it by now)! But in that scenario it doesn’t really matter what humans do since the entire premise is based on forces completely out of our control.

    • SunlessNick

      That doesn’t account for the difference between Earth and Mars’s gravity wells. The point of the resources being avalable in space is that they’ll also be easier to get to than those on a planetary suface, regardless of the native life. This will be less on an issue for aliens capable of crossing interstellar distances, but still represents extra work there’s no reason to bother with.

  14. Michael Campbell

    “Except everything I’ve been saying about aliens applies to humans too. By the time we’re able to travel the stars, we’ll no longer have any need for conquest.”
    Unless we get a sudden technological jump at some point!
    Did someone mention crashed spaceships???

    Oh sure, bayonet and bullet arn’t the highest tech’ they’ve seen. But for making unarmed civilians dead!?! They’ll do just fine!
    And those detestable human beings are cruel and primitive…savages! Just look at what they do to each-other.
    They just can’t be trusted with FTL drives and they’ll have to be snuffed out wholesale.
    You know, exterminated in an act of galactic public hygiene.

    In many ways the Sci Fi invasion story is “buyer’s remorse” for the colonial nations.

  15. Bubbles

    Just wondering, are you suggesting it is unlikely for aliens to ever be hostile? Or are you just referring to humans being on Earth, rather, than, say, humans becoming an interstellar civilization? Because while you’re probably correct about resources being easier to get from other places than from Earth, if humans control the resources of a significant portion of space, than it might motivate some aliens to attack to get them.

    (I’m mainly talking about resources because articles on this site have claimed that all wars are ultimately about resources. I don’t necessarily agree with that, but I’ll go along with it for the moment. Some ideas I have for potential futuristic non-resource-based conflict:
    Do you trust powerful AIs or not? They can do really good things, but they can go really, really wrong.
    Somewhat related to the above, some form of crime/hostile actions may always exist. Even if it’s not resource-based, there are a few humans, and possibly other beings, who are motivated by factors such as sadism.
    Social relations in general, such as finding friendship, romance, etc. I think this was actually mentioned elsewhere on the site as a possible conflict in a post-scarcity world.
    Should suffering be eliminated entirely? For instance, using genetic engineering to eliminate predation or to replace sad emotions with forms of joy. People such as David Pearce have actually debated this in real life, with strong feelings on both sides.
    Strong beliefs in general. There could be conflicts purely over religious, philosophical, or other beliefs.)

    Now, moving on to resources: the Milky Way really does have a lot of energy. An answer to “How much energy in Joules is present in the Milky Way”
    states the maximum value of energy is about 1.25*10^59 Joules (there is uncertainty in our knowledge of the galaxy). This is based on the mass of the Milky Way, so it is probably an overestimate of how much would be available to a future civilization (matter-antimatter annihilation is basically 100% efficient, but antimatter is very difficult to make or find. The link
    suggests that the next most efficient way is dropping matter into a rotating black hole for a 42% conversion efficiency rate. There is also the fact that a civilization needs some matter to live on, even if it’s a space habitat and not a planet. I will ignore these considerations for the moment.) Wikipedia’s “World energy consumption” article,_consumption_and_electricity
    states that in 2013, world energy consumption was about 5.67*10^20 Joules, sourced to the U.S. Energy Information Administration. At this rate of consumption, it would take about 2.20*10^38 years to use up all energy in the Milky Way! Seems like future civilizations don’t have to worry.

    But wait! I’m talking about the current rate of energy usage. Energy usage is currently increasing. Most likely future civilizations would use a lot more energy than we do now, because of advanced technology and an increased population. This article
    shows that at our current rate of exponential growth, we will need all of the energy in the galaxy a mere 2500 years from now. Mind you, this is not actually a serious proposal for what will happen but a reducto ad absurdum for the claim that current growth rates can continue forever. The author believes that growth will have to stop soon. Also, this doesn’t use the 1.25*10^59 Joules presented earlier, but the value for stellar radiation for all stars in the galaxy, apparently about 10^38 Joules. Due to the power of exponential growth, using the higher value for “energy in the Milky Way galaxy” in the calculation merely pushes the date to about 3882 years from now.

    Here is where things get much more speculative than before. Precisely how much energy will be used in the future? It is probably going to be higher than today’s usage, but we don’t know precisely how high, as it’s difficult to say which technologies we can actually use. Wormholes? Replicators? Terraforming? Something we haven’t even imagined yet? Exponential growth is probably going to have to stop in some time (or at least become far, far, far lower than it is today), or our civilization will destroy itself, but when? Also, how many (if any) energy-using alien civilizations exist in the Milky Way?

    Despite these uncertainties, I suspect there is a possibility that future civilizations will be using technologies that require far more energy than what is necessary today. I also wonder whether there could be some groups who want exponential growth even if unsustainable, such as those who don’t realize the implications or those who want to reshape the universe to their own whims. It’s unlikely that any such growth is happening near us, or we would have noticed it otherwise, as you mention in this article. This might be a solution to the Fermi Paradox: even if aliens can colonize much of the galaxy, they don’t because they know it can’t last for long. Conflict might be about resource management, with groups fighting about how to use energy.

    • Oren Ashkenazi

      At the moment my predictions are limited to a modern or near future scenario. Predicting much beyond that is difficult if not impossible because of all the leaps of reasoning one must take.

      • Bubbles

        I know. I suppose I was influenced by your article “Five Obstacles to a Realistic Interstellar Empire,” in which the last point argues that in a far-future scenario, there wouldn’t be conflicts over energy. I commented there to question certain assumptions, but I didn’t have any hard numbers. Once I found some actual data about the energy in the Milky Way, I decided to mention it. I suppose I could have commented again in the “Five Obstacles” article, but I decided to comment here instead because it seems to be a pretty similar article (although I suppose I didn’t catch the time frame difference).

        Just wondering: if you state your predictions are limited, why would you make far-future predictions in that article?

        • Oren Ashkenazi

          Because the Interstellar Empire post is specifically about a far future scenario. This post is not.

          • Bubbles

            What I meant is: when you say you won’t make predictions about the far future, do you mean in any article or just here? If you mean just here, that’s understandable if you want to keep the article focused on a specific kind of scenario. However, the reason you gave originally wasn’t specific to this article; it was “Predicting much beyond that is difficult if not impossible, because of all the leaps of reasoning one must take.”

  16. Grady Elliott

    The problem is, even if there’s only one hostile alien civilization in the galaxy, in the long run it’s the one you’re most likely to encounter, because it’ll wipe out every civilization it meets before getting to yours.

    Then it’s your turn….

    • Cay Reet

      You do have a point there. But, humans being how they are, I would bet money on us *being* that one hostile alien civilisation.

      • Bubbles

        Perhaps, but even if a civilization was hostile, that doesn’t necessarily mean it would be able to wipe out other civilizations. I would expect nearly any lifeform to want to fight in self-defense if there was such a serious threat to their existence. Now onto the more speculative ideas: Perhaps any hostile civilization would be wiped out or pacified by others before it became a significant threat. If interstellar warfare turns out to be impractical, a civilization might not be able to do something that big, even if it could pose a smaller-scale threat through other means.

        Furthermore, the original argument suggested that there would be common factors that applied to any advanced spacefaring society, and requirements that a society must meet before going into space. While I am certainly very suspicious of any absolute arguments, it is at least possible, from our current state of knowledge, that such factors exist and cause peace to be the only possible state. After all, every civilization in this universe presumably obeys the same physical laws, whatever they are.

        Nevertheless, I do have several counterarguments to some of the points presented in the article. The argument that traveling in space means you can live in space suggests that the only two possibilities are FTL and generation ships. However, what about sleeper ships or time dilation? If interstellar travel could be accomplished slowly by putting the travelers in a state of hibernation or simple relativistic time dilation, then beings could travel across space but not be able to do anything interesting in there (or not like living on a spaceship), so they would still want somewhere to live. Large megastructures may be impossible: they often require materials that are essentially unobtanium in terms of properties and which haven’t been proven to exist.

        I would make statements about resources, but I will concede that anything that can use up galactic resources (which I suspect is possible, even in cosmically short time scales. I have done some rough calculations: if you want to see them, tell me and I will post them here.) is not something modern-day humanity has any chance of defeating. (Although I suppose it might be possible if, say, there is also an advanced faction that decides to help humanity. I haven’t seen many stories like this, but it would be interesting). For reasons I will give in the next paragraph, I have thought of the possibility that a war (or at least aggressive action) might occur to control human energy consumption if it turns out that they (or a subgroup) can expand into space without having gotten resource consumption under control.

        Interestingly, I have thought of a potential explanation for the Fermi paradox somewhat based on arguments here. The idea is that aliens don’t expand throughout the whole galaxy (such as by sending self-replicating colonization probes) because that would be an unsustainable growth rate. See the “Galactic-Scale Energy” post on the Do the Math blog for an explanation, albeit one focused on humans. Advanced civilizations know what is sustainable and what isn’t (if they hadn’t figured it out in time, they would have become extinct or at least never reached space). Even if each civilization expands to a few star systems (which would help to avoid extinction from system-affecting catastrophes such as star death) and sends exploration missions to many systems, we may not have detected it yet (seriously, we have only found a few thousand extrasolar planets out of the likely billions in the Milky Way). Radio may simply be a poor way for advanced civilizations to communicate (as many scientists have theorized), explaining why we haven’t detected radio signals, and as previously stated, megastructures may be impossible, impractical, or too energy-consuming. There are, of course, other possibilities (some of which could even be true along with this one even if my idea is correct).

        • Cay Reet

          I’m not going into detail on everything, just on the point ‘how probable would it be for a hostile civilisation to eraticate others.’

          The simple answer is in technology. While every space-faring civilisation will have to develop technology for space travel, obviously, be it generation ships, cryostasis, or FTL drives (or bending space in some way), chances are high that a generally hostile (or, rather, war-like) civilisation will also spend a lot of resources into developing and building weaponry. Which will put them ahead of other civilisations when it comes to warfare.

          Every civilisation will fight for its survival, but, as examples on our own planet show clearly, they will not always succeed. Perhaps the hostile civilisation will eradicate others completely. Perhaps they’ll enslave them. Perhaps they’ll take over planets, perhaps they’ll break them up for raw resources (which is unlikely). But a hostile civilisation has a much higher chance to develop more dangerous weaponry than a peaceful one and is thus far more likely to come out on top in a fight.

          • Bubbles

            I understand what you are saying. However, there is the fact that space is big. Especially if FTL travel is impossible (or at least so difficult/expensive that it can’t be commonly used), there might be a defender’s advantage even for peaceful civilizations that prevents an attacker from overwhelming them, as it would take a lot of effort to travel. Also, things such as stealth might be difficult or impossible in space. Finally, there might be a limit to technological development that every advanced civilization that survives for long enough reaches. Now, is any of this definite? No. However, the whole topic is speculative anyway, and furthermore, it seems many people who have thought about it have concluded that space warfare is impractical.

          • Cay Reet

            *Space* warfare is, indeed, impractical, because there’s huge distances to overcome. But attacking a planet isn’t necessarily the same as space warfare, because it might be possible to drop into the atmosphere and take the war back to a world with gravity and everything which comes with it. Then we have highly advanced planetary warfare which is far more feasible.

            I agree that futures with generation ships, for instance, are highly unlikely to feature a lot of battles, because you would have to pick the place to fight generations (depending on the species something between 10 and 50 or more years) in advance. FTL or similar ways of travelling would make it more possible, because movements through space are easier then. But even if a civilisation sends generation ships to worlds they know are or might be inhabited (and inhabitable for them), they might still be hostile and ready to kill whoever is living there – again, hoping to have the further-advanced weaponry.

  17. GeneralCommentor

    I feel like you’re focusing so much on tackling the idea of aliens being actively hostile towards humanity that you overlook the idea of alien civilizations not being actively hostile but having a negative impact on humanity through either misunderstanding or negligence.

    The article itself acknowledges that alien psychology may be entirely different from what we are familiar with on Earth and I feel that that opens up the idea that, while alien intelligences may not be actively hostile towards other species, their standards of societal interaction may be entirely different from how we humans behave.

    Is the predatory wasp “evil” for injecting its offspring into a caterpillar? Is the slaver ant hostile for “enslaving” other species of ant to maintain their hives? These behaviors are ones that these species have developed in order to function and if these animals were to develop sapience akin to humanity I feel it would not be too far a stretch to think that their concept of morality would be influenced by their biological behavior. This is not to say that these species would be inherently “evil”, but that the systems of morality they develop would have a much different view on injecting their young into other creatures or using other species as labor than we, as a species that never developed these survival techniques, would have.

    Even if we assume that alien life is psychologically comparable to our own and is friendly towards us we can’t discount the danger of simple negligence. A comparison of alien contact to European colonists and the indigenous peoples of the Americas was brought up as a potential parallel in regards to conquest, but I think the more apt parallel was the effect European diseases had on indigenous populations. While the European settlers were actively hostile & colonialist in their relations with the Americas it’s important to note that the reason they were successful in oppressing and marginalizing indigenous populations less out of superior force and more because the diseases they brought with them across the Atlantic were absolutely devastating to indigenous populations.

    The same problem of disease is a potential issue to consider with alien life. We don’t really have a frame of reference as to what life that evolved completely independent of Earth would be like and how it would biologically interact with Terran lifeforms. A microscopic entity that is harmless and ignored by alien life forms could be potentially devastating to life on Earth.

  18. Brenden1k

    There is valid reasons for aliens to invade humans ideology, if they have some version of manifest destiny aka Harry turtle dove the race or religious bases such as Halo they could declare war even if it not rational.
    People are not always rational actors, so aliens can invade us for irrational reasons.

    Crysis before crysis 3 and muv luv, pointed out the possibility of paperclip maximizer style invasion in which the aliens have no grudge against us they just do not really care or notice us.

  19. Sedivak

    “All Resources on Earth Exist Elsewhere”

    It may not be so. Earth has a somewhat unique trait of having easily reachable heavy metals like gold, uranium etc. I think these are not usually found in planetary crusts but much deeper. The reason we have them in the planetary crust might have something to do with the fact that the early Earth collided with some other heavy object creating our Moon (also somewhat unique due to its size) and swirling the Earth’s planetary material so that these metals came to the surface. Strip mining Earth for heavy metals might be actually quite profitable, and much easier than deep mining or outright breaking other planets. I have read some novel where this was a source of a major conflict, but I forgot which one it was.

    Unusually for its size, composition and position in the goldilocks zone, Earth also has a pretty decent magnetosphere (read: radiation shielding) which could make it valuable real estate.

    And real estate for population expansion could be a good motivating factor for a civilization who lives in comparable planetary conditions. Exactly because space travel is prety resource expensive, you do not carry a lot of habitable space with you on your ship – that extra mass would cost you a lot of fuel/energy. If a civilization wanted/needed to live in Earth-like conditions, then conquaring Earth, even with the long travel, could be much more energy-efficient than breaking asteroids and moving asteroid-class masses around the solar system to build suitable habitats from scratch. Moving these amounts of mass would be extremely expensive.

    • Sedivak

      And to the mention of Dyson spheres: I don’t have the numbers o hand but I think I have read somewhere that moving enough mass to build a Dyson sphere would actually require more energy than a star like ours outputs in a lifetime. Large scale relativistic interstellar travell might be much cheaper, especially using something like the Bussard ramjet (see wikipedia).

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