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In search of ET: Fear of what’s out there causes split among space scientists (sfchronicle.com)
29 points by howrude 21 days ago | hide | past | web | favorite | 67 comments



This is not something I'm worried about. Unless FTL travel is real, the amount of resources necessary to make the trip to kill off/enslave humans makes the entire effort unprofitable. Basically, if you have the ability to travel between star systems, you already have the technology to exist effectively forever in a self contained environment. You can mine asteroids/planets forever in your own solar system for effectively unlimited materials.

Its like you are thirsty so you build an intercontinental jet plane from scratch using parts from around your house to fly to Japan to steal a single Coke from a 7-11.


Even mere humans, who've only reaped the fruits of serious scientific advancement for a few hundred years have already come up with a way to get to Alpha Centauri within 44 years.[1]

All such spacecraft would have to do to cause massive devastation is aim at Earth and not stop, though it's likely that more advanced civilizations could come up with more effective means of destruction.

Alien civilizations could have advanced scientifically for thousands, hundreds of thousands, or even millions of years. It is unlikely that we can accurately put limits on their capabilities.

[1] - https://en.wikipedia.org/wiki/Project_Orion_%28nuclear_propu...


Project Orion is a cocktail napkin estimate. The actual problem is much much harder.

But as you point out, anything that can travel between the stars can trivially wipe out all life on Earth without warning. They also know we exist already thanks to the changes in the chemical composition of our atmosphere. If they want to kill us then we're dead.


"Its like you are thirsty so you build an intercontinental jet plane from scratch using parts from around your house to fly to Japan to steal a single Coke from a 7-11."

The flaw in this analogy is that the you with these capabilities has different, and possibly incomprehensible desires, compared to the you who wants a Coke.

The natives of Central America and Mexico were not aware of how excited those Spaniards would be about Gold and Silver.


That's assuming aliens prioritize profit. Perhaps they're technologically advanced and have everything they need, but have deeply internalized the logic of using preemptive strikes to protect themselves from potential future threats.

Such a strike might not even be that expensive or need FTL technology: just send out a few one-way nuclear-armed suicide drones at 0.12 c [1], via a path that obscures their origin (e.g. via a gravitational slingshot or three).

[1] Perhaps with a design like https://en.wikipedia.org/wiki/Project_Daedalus, https://www.damninteresting.com/the-daedalus-starship/, which is probably even within our technical capabilities. We also have weapon designs that could render the a planet uninhabitable (e.g. https://en.wikipedia.org/wiki/Salted_bomb).


Or send a chunk of metal at near light speed. Things in space move very predictably for thousands of years, and as the projectile only barely trails the signal of its departure, it would come as a total surprise even for very advanced civilizations.

Let's say an advanced civilization around Sirius wants to take us out. A chunk of metal (or anything really) of about 1000 metric tonnes would be completely invisible until it were very close. Travelling at 99.99% of the speed of light, it would impact with the energy of 13 times the meteor that wiped out the dinosaurs. The light of the projectile being "fired" would reach us in 10 years, and the projectile itself would arrive just 8 hours later. There is no foreseeable way to defend ourselves against that.

An overly cautious civilization with that kind of technology might just decide to start sterilizing all the planets in its surroundings without having to leave their solar system, just in case.


This is kind of like worrying that God might just decide to kill everyone some day. There's nothing you can do about it, so it's best to just forget about it and hope that by the time a civilization is advanced enough to build such technology they also have advanced ethics enough to not use it.

This used to be a common SciFi staple, that a civilization advanced enough to travel the stars must have solved their social issues first or they would have destroyed themselves with their own technology. Basically as the cost of ending all life on the planet drops you need to advance your ethics fast enough to prevent it from happening. Eventually everybody is carrying around pocket antimatter batteries and either everybody is well adjusted or everybody is dead.


The problem with that is that targeting may be much more difficult. A passive weapon could be thrown off target over long distances due to gravitational perturbations or survey inaccuracies, and would likely have been mistargeted in the first place due to civilizational changes at the target (kinda like the problem with aiming flak, your target can move unpredictably between when you fire your gun and when your shell arrives, see https://www.youtube.com/watch?v=eRJC2mkrZks).

An active weapon could be targeted at a solar system too far away for an accurate preparatory survey, then identify and target rocky planets and large artificial structures once it arrives. It could also perform course-corrections in transit, and remain substantially dormant for much of the trip for stealth and surprise.


This is the wrong way to look at it. You're not thirsty for resources. You're protective of them. Imagine if you were aware of giant, angry Americans who were flying to Japan to steal all of your coke and convert all your land and resources into coke manufacturing plants.

Do you let the plane in? Do you stop it from traveling at all? Do you glass the surface of America with nuclear weapons? How do you know they won't do it to you?


But that makes no sense. You're spending resources protecting against a scenario that is effectively impossible. The term for that is paranoia.

Plus, it doesn't even make sense to try to "protect" yourself because their first move if they even thought like this would be to nuke everything flat with no warning. There's no defense against it. You can't hide either, the signals are already out there, they know where you are.


> But that makes no sense. You're spending resources protecting against a scenario that is effectively impossible. The term for that is paranoia.

It makes no sense to insist that aliens would think as you think they should. That doesn't even make sense for humans in most cases.

> You can't hide either, the signals are already out there, they know where you are.

That's arguably not true.


Even if they don't think the same way we do they are (probably) bound by the same laws of physics. Obviously this argument doesn't work if they have developed warp drives or infinite energy sources and reactionless engines, but if they're bound by the rocket equation as we are then there are truths that can't be avoided.

We are on the cusp of being able to detect the biological markers of life on distant worlds by spectroscopy. An alien civilization that can traverse the enormous gulf between solar systems can very easily build widely spaced telescopes that can monitor all nearby solar systems for changes to atmospheric composition. Anybody who is paranoid enough to need to kill any life around them would obviously build such an array. There is no hiding from them, the technology is much too simple compared to what you need to travel between solar systems.


> An alien civilization that can traverse the enormous gulf between solar systems can very easily build widely spaced telescopes that can monitor all nearby solar systems for changes to atmospheric composition.

Maybe they can't themselves, but don't like the idea that someone else eventually may be able to.

I think you're overconfident of the safety of actively advertising our presence to the universe because you're making a lot of assumptions and only considering a small number of possibilities. The problem is that there are so many unknowns and so many shades between different possibilities that no one can really be confident about anything, except that the risk could be anywhere between zero and the maximum.


But you’re thinking of it as intentional and directed attack. It can simply be collateral damage. “Oh, what’s there, let’s send a one way selfdestroying probe (don’t take this literally).

But you can imagine a situation where like we’re looking for life on Mars and in doing so inadvertently destroy unknown life.


"Any predatory civilization would probably have detected us by now simply by analyzing our atmosphere, they reason. Humans, Vakoch said, have been using radar, which can purportedly be detected 70 light-years away, since World War II. Television and radio signals would long ago have signaled our presence to malevolent space ruffians, he said."

That's how he justifies the broadcasting of signals, but take the next logical step: It also indicates either that nobody is listening, or that they're unable or unwilling to contact us, or that they're already in the process of trying. In any case, it's hard to imagine the METI messages would change anything. By that same argument. And I mean why would the intentional/contrived message be any more persuasive than all our "honest" and un-self-conscious messages to each other over the years? Anybody who was curious could have learned everything by now.

I also would like to call out the typical assumption of a "technically-advanced race of aliens" and whatnot. The aliens always seem to be technically advanced, don't they? In other words, like us, but more so. That's a mirror you're looking at, and it's how you recognize something man-made. Homo sapiens is the one with the fetish for techne. It seems the aliens we imagine are always either similar to us (which we like) but better, or else they're dissimilar, and predictably worse/more evil (and tend to look like combinations of creatures from THIS planet that we don't like... insects and reptiles figuring prominently). That's more a mirror of our dislikes, but still a mirror. Aliens are always created in our image, and that shows an embarrassing narcissism & lack of imagination. We're just projecting our hopes & fears. Keep your mind open.

One more nitpick: "We won’t know for about 25 years, assuming the communique is sent at the speed of light." Pretty good assumption, given that it's not possible to send EM waves at any other speed!


I haven't seen any anti-METI argument which counters this:

"Humans, Vakoch said, have been using radar, which can purportedly be detected 70 light-years away, since World War II. Television and radio signals would long ago have signaled our presence to malevolent space ruffians, he said."


> I haven't seen any anti-METI argument which counters this:

> "Humans, Vakoch said, have been using radar, which can purportedly be detected 70 light-years away, since World War II. Television and radio signals would long ago have signaled our presence to malevolent space ruffians, he said."

I think the key word there is "purportedly." Has anyone done an analysis about what kind of equipment would be required to detect those old signals at 70 light years? Has there been any analysis of how for out they could propagate until they were totally overwhelmed by noise?

Personally, I'm skeptical that those signals were transmitted powerfully enough or focused narrowly enough to likely be detected. This article (https://www.nature.com/articles/461316a) makes it sound that way:

> Indeed, SETI is marked by a hope, bordering on faith, that not only are there civilizations broadcasting out there, but that they are somehow intent on beaming their signals at Earth. An alien SETI project relying on a similar faith in Earth would be sorely disappointed. It's true that a random mix of radar and television signals has been expanding outwards from Earth at the speed of light for the past 70 years. But there have been only a few short-lived attempts to target radio messages at other stars — with each attempt arousing concerns over alien reprisals.


The atmosphere point is even more compelling. Earth has been broadcasting with quite non-trivial power "I HAVE LIFE" for about two and a half billion years. Most of the "hostile alien" hypothesis work out to the hostile aliens needing to exterminate all life, not just life that already seems to be intelligent, because you don't know how fast something might become intelligent when you're not looking, so if Earth was going to be wiped out, it should have been a very, very long time ago.

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

(Since someone will probably bring it up, no, I do not believe extinction events are aliens trying to wipe out life, on the grounds that if intelligent, hostile aliens intended to wipe out life on Earth, I'd expect them to succeed, and not merely inconvenience life briefly, but actually totally and permanently sterilize Earth. Any culture that can fling either mass or energy at early Earth in any reasonable period of time is already very near the necessary energies to do that. Across billions of years I'd expect someone to have managed.)

Another reason why I tend towards the "yeah, we are non-trivially alone" myself. Maybe the entire universe isn't empty, but I don't think there's any reason to believe there's anything nearby.


"The atmosphere point is even more compelling. Earth has been broadcasting with quite non-trivial power "I HAVE LIFE" for about two and a half billion years. Most of the "hostile alien" hypothesis work out to the hostile aliens needing to exterminate all life, not just life that already seems to be intelligent, because you don't know how fast something might become intelligent when you're not looking, so if Earth was going to be wiped out, it should have been a very, very long time ago."

Even if they're out to destroy all life, they might prioritize killing intelligent life first, as it could be a threat (or for some other reason).


Obviously known-intelligent life would be a priority, but if they can't get around to the lower priority stuff in 2.5 billion years, well, why should we take the Dark Forest argument any more seriously than any of the other civilizations we've cruised by in the past 2.5 billion years?

The amount of energy available to even a single solar system, let alone all the advanced galactic civilizations that are supposed to be out there, dwarfs what it would take to sterilize Earth. And don't think I'm underestimating that quantity; it's larger than any impact real Earth ever sustained, and it has sustained some doozies. But what's in even a small star, even in a small star's yearly output, is orders of magnitude larger. And this is with the relatively expensive brute force method too; if you're willing to roll the dice on the target not having intelligent life a few steps above where we are now, you could probably put together a gray-goo-esque replicator that would conclusively eliminate any civilizational threat from a given planet permanently, for the cost of delivering a few kilograms of payload to the target system, which is presumably trivial for our advanced civilizations.

As I said, I'm still pretty much on the "yeah, we're probably effectively alone" side, because when you really treat the "the universe is full of advanced intelligent life" idea seriously, you just don't get what we see in our sky. Not least of which is the wide variety of ways in which we simply shouldn't exist, because our ecosystem should have been wiped out one way or another, be it by raw destruction, or simply interaction with some other much more advanced ecosystem that simply steamrolled Earth's primitive life the same way we steamroll an ant hill, a billion years ago. Just about the only way to save the hypothesis is that we are the "Progenitors" and the universe is full of intelligent life if you look at a random place and time, it's just that the "full of intelligent life" hasn't happened yet. If the universe as a whole is full of intelligent life, there still has to be a first set of civilizations, and while every individual in those civilizations may rationally say "the odds of me being here when the universe is empty are as good as zero", there still have to be some "lottery winners".


Counter argument:

So if we've been using radar since WWII, and radar has been capable of signalling our presence to alien civilizations, then we don't need METI. Alternatively, if METI is proposing a signal that can reach alien civilizations in a way that TV and radio signals cannot, then the original objections to METI still stand, and the TV/radio signal argument is a red herring.

But really, it's just common sense. Everything we know about the universe tells us that complex organisms exist at the expense of simpler organisms. As a nascent space-faring civilization, we are the minnows in the ocean, and signalling our presence to the bigger fish is the kind of mistake that a minnow only makes once. What exactly is the perceived positive outcome of making contact with a more advanced civilization?


This, exactly. What METI is proposing, as I understand, is a stronger, more unmistakable signal of intelligence which carries higher risks.

Also, this is 70 years of noise, a blip on the galactic timescale, getting weaker the farther it goes. We can't stop what's gone out already but that doesn't make us obligated to keep advertising our presence forever.


Is there a proposal from METI more capable of reaching out than this 32MW transmitter with a 1.4° beamwidth which has been operating continuously for decades?

https://en.wikipedia.org/wiki/Eglin_AFB_Site_C-6#How_the_rad...


A counter to that might be that these signals aren't strong enough to accurately detect our exact location at interstellar distances. Parallax is hard at those distances - if we were to get a signal from a point in the sky, whats to say its coming from one star, or another one "behind" it? Not possible to determine from the signal strength alone, since you don't know the signal's original strength.

In Carl Sagan's Contact, we were only able to determine the signal came from the star Vega because it was the only star that would have been at the right distance to receive our earliest radio signal and transmit it back to us - also Vega is relatively close by compared to other stars, close enough that our parallax created by our orbit around Sol was sufficient to get a read on signal source.

A deliberate attempt at active signaling would remove all doubt for an extrasolar observer.

Liu Cixin's The Dark Forest explores this scenario in depth. I would explain more but don't want to reveal some important spoilers.


It might be hard for us to figure out where the signal is coming from, but an alien race that is capable of traveling between star systems shouldn't have any problem figuring it out. Frankly if such an alien race exists they already know there is life on Earth just from the changes in chemical composition of our atmosphere. They can even figure out when we discovered agriculture. In a few decades they will even know that we discovered radio communication.


Here is one:

Absent any form of antenna technology we don't know about, all of these signals are going to be extremely dispersed and very near to the rate of noise, for any receiver that is even moderately far away. It is still possible to detect these signals, but only you know exactly what you are looking for. Not only the direction and frequency of the signal are needed to know, also amplitude, polarization and any form of modulation pattern. Otherwise, the signal might just be interpreted as noise.

Also 70 ly are "not even beyond our backyard" so to speak. 70 ly is such a small distance, compared to other possible distances in our galaxy. It is a far too small patch to be taken as a basis and extrapolate to the rest of the 27000 ly of galaxy ahead of the signal. Maybe the space ruffians are 80 ly away from us, or 800...


Really? How many habitable exoplanets are within 70 light years, and what are the odds of life (let alone super-advanced space pirates) existing on them? Also a little known fact: only energy travels at light speed. So even in the worst case scenario, they won't be here for a few hundred years.


At best, that says “any badness within 70 LY has already been tipped off.”

The METI guys are working on more powerful emitters specifically so as to send additional data that will be coherent over larger distances.


I think the fears of some ET empire with Darth Vader (or similar) at the head is very misplaced. Just think of the economics... "let's go exploit that world 10 LY away from us that we don't fully understand and which will still takes us an insane amount of time to enslave and milk resources from!" What a scalable strategy given the size of space... one might even say it's astronomically large! The resource consumption alone would be a very speculative bet by any would-be invaders... unless they were already close at hand, but we're probably already too late to prevent that....

Naw... if there is any alien apocalypse to worry about it's that some advanced civilization saw a life friendly Earth through their telescopes, perhaps millions of years ago, and decided to seed the place with their own bio-material and without any regard to what life might be there. It won't be a marching army, but a "Terra forming" project that may well already be underway if its happening at all, I would expect.


You can't know or understand possible ET motivations or capabilities.

Humans routinely drive other species on Earth to extinction, our own cousins. We also damage our own planet's environment.

It may be logical for an ET to just destroy us the way you might destroy a harmful bacteria, which might otherwise spread unpredictably. It wouldn't be about wanting slaves or raw resources (although as someone said, Earth itself might be considered somewhat valuable).


"You can't know or understand possible ET motivations or capabilities."

True, but my argument is that their intentions fundamentally don't matter. The real costs of acting on ill-intentions through interstellar space would probably give any real life Klingons or Romulans pause.

Meanwhile we fly, sometimes even into space, drive, walk outside, stay inside, eat/drink things that we shouldn't (but enjoy), and a thousand other risks which are substantially more real on an everyday basis... and many of those risks also come with rewards that can make life much more full and rich.

I think making contact with aliens would most likely just 1) confirm we weren't alone or 2) might actually be of benefit as we exchange knowledge and ideas, and/or 3) tell us that evolution tends to creates fearful, xenophobic entities where it also develops intelligence... in that order and with no further consequence than the knowledge.


The motivation isn't exploiting Earth resources, but killing us before we can kill them. Most humans don't believe non-human species have any right to life, so why would sapient aliens believe humans have any right to life? Humans have a non-zero probability of growing powerful enough to be an existential threat to the aliens, so the safest option is to preemptively eliminate them.

And even if the aliens are convinced that humans are 100% alien-friendly, it would still make sense to kill us all because there's a chance we'll develop uncontrolled recursively self-improving AI ("intelligence explosion"), which would be a threat to the aliens without us intending it.


"so why would sapient aliens believe humans have any right to life?"

I'm suggesting that it doesn't matter and that there are other, more significant factors that render this concern moot.

"Humans have a non-zero probability of growing powerful enough to be an existential threat to the aliens, so the safest option is to preemptively eliminate them."

Non-zero, but near zero. The same sorts of constraints on resource coordination and how much one can likely play with the physics involved not only constrain our would be destroyers, but constrains us as well. Any aliens advanced enough to hear our signals and have the realistic ability to contemplate a move against us can probably do the math: the likely threat of any alien civilization is from a practical perspective, zero, to them or us. The costs are too high, the barriers are too high, the risks are too remote, the rewards are too low.

But here's a different perspective. While hand-wringing about the risks, we completely ignore the possible rewards of actually making contact.

Given that the benefits for all involved in knowledge transfer could well be non-zero and is much more likely to be accomplished. The only issue there is that it's likely to be very, very slow. So maybe they have knowledge about achieving commercial scale fusion energy production. Maybe they help us to understand the dangers of recursive AI (which I also think are overblown). Maybe they can help us understand how to colonize our own solar system (much more realistic than interstellar colonization). Maybe they can help us escape our tendency to indulge in distinctly emotional responses, especially when confronted with the unknown, and rely a little more on reason and rationality...

If I were to gamble on this topic, I'd bet on the more possible, optimistic outcome than on the less likely doomsday scenario. And in the meantime, I'm going to hop into my car (and thereby taking a real risk) and pick up my son from school. Cheers!


"Any aliens advanced enough to hear our signals and have the realistic ability to contemplate a move against us can probably do the math: the likely threat of any alien civilization is from a practical perspective, zero, to them or us. The costs are too high, the barriers are too high, the risks are too remote, the rewards are too low."

This argument reminds me of economic theories that assume all humans are so-called "rational actors".

Even humans, which are in most ways like us and who we have some hope of understanding, do all sorts of things which most of use would consider "irrational", insane, self-destructive, and otherwise incomprehensible.

What justification could there be for assuming alien intelligences think in terms of costs, risks, or rewards? Or that they are in any way "practical" from some human's point of view?

Your argument also ignores the possibility that they have technologies or capabilities that might seem impossible (or even unimaginable) to humans of today (or perhaps of any time). Something that seems undoable to us, like FTL travel, might be possible or even easy for them. We don't know what we don't know.


We're already sending out a signal into the cosmos (and one more powerful than the radar signals others have mentioned)- the recent sharp upswing in CO2 over the last hundred or so years [0] would look markedly artificial, which combined with the presence of oxygen (which wouldn't stay in the atmosphere if it weren't continually renewed) strongly indicates at least a complex ecosystem, if not directly implicating an industrial civilization. Detecting light reflected from exoplanets is something we can already do, or nearly so, so we can count on this being detectable from large distances by alien civilizations with access to potentially megastructure-scale space telescopes. At that point, any reasonably curious or concerned ETs could send a probe to get a closer look.

Earth, as far as we know, is an unusual planet, and obviously so. Either we're wrong, and there's Earths all over the place, or we're alone, or ET has been keeping an eye on us for a long time already; that we're "hidden" is hard to imagine.

[0] https://www.co2.earth/co2-ice-core-data


If you saw a sharp change in the atmospheric composition of a planet in our solar system would you think "volcanoes" or "life"?


Most known cases of two formerly separated civilizations coming into contact have ended like the European invasion of the Americas. I think we'd do best to be cautious unless there is at least a slim hope we could ward of an invader.


Dumb statement: "Television and radio signals would long ago have signaled our presence to malevolent space ruffians, he said." There are only 11 known habitable exoplanets within 50 light years that we know of. Assume there are 1000 within 100 light years. The odds of a super predator in that small of a sample are virtually 0. Plus, even if they had their armada on standby, it takes at least 100 years to get here. Apparently there is little intelligent life on earth.


To be honest I think we are vastly more likely to be destroyed by ourselves than by aliens. Maybe we'd be better off enslaved by aliens; we could be the green mans burden.


Sounds like a lot of scientist have been reading the Three Body Problem.

I think we should worry more about AI taking over rather than aliens. Its actually much closer to home. On the other hand the only alien intelligence which has the luxury of interstellar travel is the one which has no sense of time and that would be alien AI again.


The Three Body Problem and ASI are two songs on the same instrument: value misalignment in cases of massive power differentials.

In an indifferent universe, two optimizers optimizing different things will be in conflict. Can we build machines that optimize what we want to optimize? Can we align our optimization with aliens before it becomes optimal for one of us to annihilate the other?


I figure it's all moot anyway. We are probably alone in the universe. Fermi's paradox is a thing.


I don't think we're alone. But I do think we're kind of trapped in our Solar System along with everybody else. Interstellar travel is so outrageously expensive that by the time you have the technology to do it you necessarily have the technology that makes it unnecessary.

An interstellar journey means you need a ship that can survive indefinitely in deep space, where you don't get free energy from solar panels or have easy access to comets to mine for materials. An in-system habitat has to be a solved problem before you can even consider building one. But at that point you have effectively unlimited living space, energy, and materials so why bother?

Even if your sun is turning into a red giant you can move your habitats to the optimal distance to sustain life. It's really hard to imagine a time when Humans have used up the entire mass of the other planets in the solar system and need to look outward for resources. You could build an almost unimaginable number of O'Neill cylinders using only the mass of Jupiter.


Being enslaved by evil aliens is among the worst of fears. The risk isn’t death or annhilation; it’s being denied the mercy of a short (100 years) existence, in bondage and suffering.

I fully support a careful approach to combing the cosmos.

Edit: May I ask why this is being downvoted?


I didn't downvote you, but this seems extraordinarily unlikely to me. Why would our extraterrestrial overlords want to use us as slaves? They travelled a long way to get here, surely they should have robots or a genetically engineered underclass or something. We're in the process of making human labor obsolete ourselves. The only scenario I can imagine where this makes sense is one where the aliens have interstellar travel but lack decent genetic engineering, and they're interested in exploring/building/mining in places that are inhospitable to both their own biology and robotics but not our biology (like a planet whose gravity would crush them that also has an EM field that would fry circuits without exceptional shielding). This seems like a stretch to me. I feel like wiping out a potential future threat is a much more reasonable incentive, with exploitation/study of an already existent biosphere being a runner up. Most of the things they could want humans for would be more efficiently accomplished by phytoplankton and krill. You're right that nigh-perpetual enslavement is the most horrifying possibility, it just seems implausible.


Bondage, you say? Sounds like Rocky Horror Picture show.

The point is not some specific fate, but that anything could happen. And anything includes loads of bad outcomes , most of which we are probably unable to imagine.


What possible resource does Earth or human civilization possess that ETs advanced enough to pose an interstellar threat would be interested in?


I sort of agree, but to be fair a nice habitable planet could be a really rare and valuable resource in and of itself, assuming there are any life forms out there with biology similar enough to our own to find Earth desirable.


Also assumes there aren't a bunch of Earth-like worlds that are otherwise uninhabited that would be much easier to colonize than one with potentially hostile/poisonous natives.


or that the potential alien invaders are not adapted to a completely different environment than earth's


Earth is a rich, temperate, naturally life-sustaining planet with a strong protective magnetic field. Regardless of what form of life an alien species would be, that may be of interest in and of itself based on mere rarity. Why bother terraforming if you don't have to?

Besides that, our solar system is otherwise quite rich. Middle-life, medium-sized star has a lot of mileage left. Being a single-star system, the planetary orbits and climates are naturally stable. Mercury has an enormous core of iron. Venus has a tremendous amount of energy stored and is a prime terraforming target for a civilization with the right technology.

We have 4 enormous gas giants, one of which forms a whole planetary system in and of itself, and could conceivably be collapsed into its own star.

The moon Titan is a giant ocean of liquid hydrocarbons.

This doesn't even get into the rich material wealth offered by the asteroid belt, Ceres, and Saturn's rings.

I'm sure there are better systems than ours from this perspective, but we're far from the bottom of the barrel. I'd sure as hell move here.

Another point is this, perhaps the potential of humans themselves presents a threat to another spacefaring civilization. What if they've seen species like ours rise up and conquer, and they'd prefer to nip it in the bud instead of waiting around for us to become more powerful?


We might be tasty.


Not me. All gristle and bone. I taste like your used glorkin.


Not discussed by the article, but I wonder...Is it more terrible to find out that nobody's out there? Nobody's listening?


Or how about this: find out that somebody's out there, but not evolved enough to be listening? This I find likely. Fixes Fermi paradox too, since this doesn't assume high probability of random life on some planet evolving as far as we did in those billions of years.


No. It’s much better that there’s no one out there than we being the colonised.


Doing exhaustive search of the universe is pretty big task; I don't think we can anytime soon determine that nobody is out there.


brb, hiding behind Jupiter


I will never understand people who are afraid of the unknown.


I will never understand anyone who would randomly pick a mushroom from the forest floor and start nibbling on it.


Eating mushrooms in the wild is not even remotely similar to inviting contact from other sentient species.


Was that what the parent comment said?!? I thought it was something about not understanding fear of the unknown. And then like I thought, hey is there a metaphor that might show how sometimes that it would be wise to have some little bit of wariness about the unknown at least? And then I said ah hah, there is and I wrote it down. I'm pretty sure it went something like that.


You can be cautious around something without being afraid of it.


sure - and people might play semantic games about what words really mean but at some point these concepts blend into each other. hence https://thesaurus.yourdictionary.com/caution

Another word for caution noun

    Careful forethought to avoid harm or risk:
    calculation, care, carefulness, chariness, gingerliness, precaution, wariness. See fear
I guess most people would admit a relation between the concepts, caution seems to me to be admitting there might be something to be afraid of. So to clarify my earlier metaphor with a concrete meaning: I will never understand anyone that acts like there can never anything to be afraid of in the unknown.

And I mean the perfect lack of knowledge is impossible, yes if I definitely did not know anything about something I would not be afraid of possible problems with that thing - how could I?

But we always know a bit even about the 'unknown' even if the thing we know is that there might be something in that unknown thing that would be dangerous to life, as many things in the Universe are like extreme heat, cold, releases of kinetic energy, too much water, or the presence of elements of one sort or another in more abundance than is healthy for us, or life that is similar to life on this planet since much of life on this planet is focused on killing other life on this planet for various reasons. I'm walking in an unknown environment on this planet I might still be afraid because I don't know what large carnivores it has, but I do know it might have large carnivores.


I see where you're coming from. I maintain that caution and fear are different, even if they're related.

My original post was probably too broad to be useful. This topic requires nuance that I didn't express.


Fear of the unknown is what kept our smarter ancestors from getting eaten by bears without knowing what was in the cave first.


The unknown is the source of everything good and bad, useful and useless. It evokes fear and hope.




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