Hmmm. It would be cool to discover that, but also pretty worrying. Any civilization powerful enough to build a megastructure could wipe out humanity without any effort whatsoever, so we'd have to hope they are friendly enough not to do so.
People seriously underestimate how difficult it would be to travel between solar systems. The scales involved are so far beyond human experience that we can't properly visualize them. Short of discovering a practical FTL (which seems likely to be impossible thanks to the Fermi Paradox) it is unlikely that humans will ever visit a distant solar system.
Colonizing another solar system, that's massively expensive. Sending a single interstellar missile at the planet though... that could wipe us out... and definitely seems possible without a huge expenditure of resources (for a civilization with mega-structures).
Missiles being much simpler because they don't have to support life, they don't have to slow down - and therefore don't need on board propulsion past what is needed for manoeuvring (assuming some sort of "push it with lasers" style of propulsion), and apart from systems needed for manoeuvring they can really just be a hunk of metal that you accelerate really fast.
A civilization powerful enough to make mega-structures is almost certainly able of landing on one of its endemic large meteors, attach thrusters and over the course of decades accelerate it towards us in a collision path with the earth at a decent fraction of the speed of light.
By the time we'd notice it would essentially be impossible to stop.
Point being, we should hurry up and create a bunch of Bruce Willis clones before it's too late. The future of humanity depends on it!
You could try sticking various forms of interceptors on it's path, at those speeds it's probably not maneuvering so relatively easy to intercept if you have warning.
I'm not sure to what degree we could deflect it or mitigate the damage, but I wouldn't be surprised if it was a sizeable one. Any collision is going to convert a ton of energy from kinetic energy to thermal energy, which should in large part radiate away before impacting earth. We could also do various clever things like putting hydrogen targets in the way which would undergo fusion upon collision with an object moving at relativistic speeds.
Maybe my mental model for how that works is wrong, but I'm just picturing a dust/rubble cloud at 10% of c irradiating the planet with xrays or something due to whatever extreme friction interaction happens in the atmosphere.
Humans are the most aggressive species we know of capable of mass destruction. We would (and do) certainly destroy other species to get some resources in order to enrich a small but highly privileged portion of our population. However—despite our aggression—we would not destroy an alien world at the mere sight of it without any prospects for profit.
Our most destructive era was probably the era of nuclear missile testing. It certainly did an enormous needless destruction of non-human (and human) habitat. This era only lasted a couple of decades and ended with a comprehensive test ban in the 1990s. Despite our capabilities we never tested these weapons of horror in space or on alien planets, and we probably never will.
I’m afraid that is not true.
https://en.m.wikipedia.org/wiki/Starfish_Prime
“The explosion took place at an altitude of 250 miles (400 km), above a point 19 miles (31 km) southwest of Johnston Atoll.”
That’s roughly the same altitude the international space station flies at.
PTBT happened in the early 60s, so almost all surface tests were conducted within the first twenty years of developing nukes. I don't think making "craters" in desert mines really qualifies as enormous destruction of habitats.
But the fact that the PTBT was signed by most nuclear states which slowed down this pointless destruction—and later the CTBT, which almost stopped it in 1997—shows that even humans with our demonstrable aggressiveness do work to limit our destruction when said destruction doesn’t contribute to the enrichment of a subset of other members of the species.
It would still be a huge effort - and for what? Why destroy a distant civilization?
I think it's a mistake to assume that aliens will be overly similar in their thought process.
So really it could go either way: alien intelligence so advanced and vast that we don't seem meaningfully alive to it, or alien intelligence so advanced and vast that man's inhumanity to man makes us seem impossibly savage and dangerous.
Next question: Are all distant civilisations friendly because there’s no reason not to be?
Convergent evolution. As soon as you get animals you get resource competition, violence, and a food chain with a predator at the top. In more sophisticated species you also get dominance/submission hierarchies.
It's possible at some point a species might transcend that and become wholly benevolent. It's also possible that some species are cooperative colony organisms which somehow evolve intelligence, self-awareness, and technology.
But at a guess it's more likely that most species remain aggressive and competitive for a very long time, and they'll only ignore humans if we aren't complex enough to be a threat - now or in the future - and have nothing worth stealing or harvesting.
Best case: you save some marginal resources.
Worst case: that civilization “grows up” and develops the means to destroy you.
The dynamics of "generation ships" change drastically with changes in human lifetime, including both the dynamics on board such a ship, but also the motivation to pursue it.
One can dream, eh?
Anybody not in a hurry would have little more difficulty than we did launching Voyager or New Horizons. They would, of course, need to build it such that it would operate for long enough to get here, which would be harder.
Or, anyway, start operating again once it got near here. It ought not to be very difficult to preserve equipment cooled to 2.7 degrees above absolute zero, which is, notably, below the temperature where helium condenses. Maybe the boiling helium could be used to wake it up.
Why would it need to be a good reason? Especially why would it need to be a good reason, from our perspective?
Hardly an original thought but it's entirely possible that an alien civilization pro-forma sends out an unmanned planet-killer-scale weapon at every alien civilization they detect, simply to avoid the possibility that we might grow up to be hostile to them, or even compete with them for resources.
An unmanned bomb like that wouldn't take many resources and it's possible they would view us as primitively as we view stomping on an ant hill in africa.
Now that's a depressing thought.
Chimpanzees 'go to war', and so do some non-great ape species like ants and termites. Interestingly, some ant species conquer other colonies and essentially 'enslave' the defeated worker ants using pheromones. It stands to reason that belligerence would arise elsewhere in the universe because it has on Earth several times.
It is unreasonable to assume aliens are anything like us.
Imagine you didn't care about the pristine land- let's ignore aesthetic reasons to hold back for a moment.
As technology improves, it becomes easier to exploit resources. You can dig deeper with automated robots etc. Now imagine a technologically mature civilization: one whose tech is pushing the limits of physics.
If our current ideas of physics are about right, you have to build things out of matter, and there's a finite amount of matter and negentropy out there. Conversely, right now, replication is cheap. Interstellar travel times are longer than civilisational lifetimes: ergo, most entities that arrive at other stars will have relatively mature technology.
If I'm a super-civilisation/large-scale AI digging in for the long haul (till the end of the universe), what do I do? I put out all the stars, if I can, because they're wasteful. Negentropy is finite: we want to eke out every tiny bit of use there, not let hydrogen atoms fuse randomly out of our control.
Large corporations viciously purse 0.1% efficiency gains because that amounts to millions of dollars at their scale. At the scale of the galaxy, 0.1% efficiency gains in your conversion of stars, planets, rocks and dust into things you care about is quadrillions of lives.
The high travel time means the dynamics are different. You don't have to move from star to star: you can just build (number of solar systems)*(safe number of sentient self-replicating factory probes per system) probes in your home system, and send them out all at once (or as they roll off the line). Every solar system is a massive prize, every star left burning a travesty. If I'm turning the galaxy into stockpiled resources, I'm not going to leave any out that are profitable- and with mature tech, it's all profitable. There's no labor cost, after all.
Yes, but it is quite likely human technology will some day.
Not many resources really. They can simply use their abundance of energy to hurl, propel, or divert some rock at us at some non-negligible fraction of light speed, and we would be powerless to stop it. Likely we wouldn't even see it coming. Make it two or a dozen to be sure.
It doesn't even take a very advanced civilization to pull off such a thing. Give it maybe a hundred years and humanity might be able to do it too.
Since it is a rather easy to end a civilization in such a way and it is near impossible to defend against, you arrive at a very... interesting game-theoretic problem: Did they already send kinetic weapons our way? Should we destroy them before they decide to destroy us? If we're about to die anyways, does it even matter if we fire back?
It's like the cold war except nobody is able to talk to another and you don't see the nukes coming.
Wouldn't you need to solve the n-body problem to hit a planet (earth) from many light years away with a rock? And to do this without exact knowledge of planetary bodies in our star system. And even if you could, a stray hydrogen atom hitting your rock early on would make it miss its target by some light hours. So you better account for every speck of dust on the way and everything with gravitational pull on your rock. An all the quantum fluctuations..
I would even wonder whether the space itself is fine grained enought to precisely target stuff light years away.
If humanity was doing this, we'd likely attach propulsion and accelerate the entire way anyways. Unless there's some new drive technology discovered by then or we hijack something natural/environs to do it for us.
You could colonize the galaxy in few hundred million years at most without FTL. Replicating machines which can build and launch many more of themselves after reaching each new resource rich system is all that is needed.
Humanity may not reach other systems, but either descendants of humanity or human derived machines improved over many generations during transit by AI(doesn’t have to be AGI) is likely to visit.
What use to them is confirmation from an entity they don't even trust?
. Religious Cults. If you look at the religiously inspired insanity in US Laws and Politics recently, coupled with what's going on in, say, Afganistan, I'd say "check".
. Doomsday preppers. Check.
. All sorts of irrational behaviors. Well, if you include enabling destructive climate change in the face of overwhelming evidence, I'd say Check.
It's almost like we read all those stories and said "Hold my Beer".
Most people will say “meh” unless it affects their daily lives.
Tbh, churches funding an interstellar mission (to convert the heathens) would be a mostly good thing
Little bits add up. I like this one.
( scroll right on by, as this is one of those things we might say for the benefit in saying it, not so much value otherwise)
If you define sound as a wave of air (or any other medium) particles then yes.
If you define sound as something a person had heard then no.
Or, you realize that your usual level or worry is totally inadequate and that you should have been worrying much more in the past.
Unless they are quantum beings.
But more seriously, at cosmic scales it is possible we observe something/some civilization in our present that actually no longer exists. There should be something like the Drake Equation to determine the likelihood of a civilization we observe actually currently existing based on the observed distance.
To your point the oldest radio broadcasts are just over 100 years old, since they travel at the speed of light they will need 100,000 years to travel the length of the Milky Way, so if a civilization as advanced as ours were on the other side of the galaxy in the future to receive them, what are the odds humans will still be around? Assuming we are around, then it would be about another 100,000 years for them to send a directed communication at the speed of light, so I think you are correct it’s not worth the effort to worry.
A reasonably strong belief that a species building megastructures will be fairly magnanimous. I believe that warlike, short-sighted species will destroy themselves and/or their planets before reaching the point where they are able to build such megastructures.
What worries me:
They may not stay that way once reaching that level of achievement. Alternately, they may remain magnanimous amongst themselves and yet be deeply xenophobic when it comes to alien species such as humans.
So far, the comforting thoughts outweigh the worrying ones in my mind.
Exploring the stars would require a general-purpose intelligence that can span multiple eras: simple tool building, figuring out how to harness and store energy sources, science and math, etc.
Is emotion required to achieve any of that, though? Probably, at least at first. I believe emotion is widely regarded as a valuable evolutionary aid, a crucial cognitive shortcut - at least at first, simply feeling that "predator is scary" and "sex is fun" is a hell of an evolutionary accelerant. You don't evolve to the point where you can understand predators (something that takes a lot of biologically expensive brain matter) unless you have a gut-level fear of them first (something that is biologically cheap).
But at some point those emotions do more harm than good, I guess, if you're trying to build an interplanetary society. Our good old emotions are good for reproducing and being scared of predators, but aren't super helpful for managing Earth's resources across long time spans.
Maybe the only way to make it past the great filters of nuclear war and environmental collapse is to discard those emotions somehow. Even if it's not the only way, seems like a valid way.
Wouldn't it be interesting if all the intelligent species in the galaxy got filtered, except humanity b/c we're relative latecomers to evolution and development.
Assume on most or all other habitable planets in the galaxy, the first species to develop was intelligent and capable of technology. But, all hit the Great Filter at the roughly same time and got wiped out. There was no chance for any of them to learn from the mistakes of the others, because they all got wiped out before they were able to detect and observe each other.
But on Earth, the dinosaurs came first, and roamed the planet for millions of years while all these other species were developing and then getting great filtered.
Then the dinosaurs went extinct, and humanity eventually evolves into a technological civilization, and is able to detect, study, and learn from the ancient ruins of the other civilizations. We get curious about why they went extinct, and then discover evidence of the Great Filter from their ruins, and thus avoid it ourselves.
We are among, or perhaps the first of a post filter generation. We do avoid the thing, as do others and eventually arrive at a mode of existence and thought making more possible, friends possible.
> The universe is a dark forest. Every civilization is an armed hunter stalking through the trees like a ghost, gently pushing aside branches that block the path and trying to tread without sound. Even breathing is done with care. The hunter has to be careful, because everywhere in the forest are stealthy hunters like him. If he finds other life—another hunter, an angel or a demon, a delicate infant or a tottering old man, a fairy or a demigod—there’s only one thing he can do: open fire and eliminate them.
If we posit that beings must kill each other, then we must also kill others, lest they kill us first. It may not even be the case that anyone wants to kill another, but simply because the possibility is there, this then becomes a tragedy of the commons, a self-fulfilling prophecy.
The rational course of action, then, is to hide as much as possible, and if you notice anyone, eliminate them before they do you.
On one hand it would suggest that our neighbors are either benevolent or at least indifferent, but on the other hand we might find it depressing to realize that we might be more or less insects at cosmic scale. It would have interesting existential implications.
IMHO the Fermi paradox suggests that we are either early or late. This would be the "late" option.
I have long doubted the dark forest hypothesis. Earth's atmospheric absorption spectra have been advertising the presence of a biosphere for almost a billion years at least. If there were any paranoid "reaper" intelligences around why would they even bother to wait for the evolution of something intelligent enough to leave the nest? Just whack candidate biospheres at first detection. It would even be a way to avoid some of the moral concerns that might arise from whacking fully sentient intelligences. Don't even let life get that far. If this were the nature of the universe I doubt we'd be here right now.
Edit:
I think the most disturbing thing to find would be apparently dead alien megastructures. That suggests ugly things like periodic cosmic scale catastrophes like... I dunno... maybe the black hole at the center of the galaxy deciding every now and then to emit enough gamma rays to destroy anything more complex than microbes living deep underground. That would suck.
Edit #2:
Now that I think of it, this makes me remember yet another Fermi paradox idea I heard once. Maybe there is some periodic catastrophe like this and the reason we don't see aliens everywhere is that anywhere near a galaxy is actually a dangerous place. Once intelligences reach a certain level they figure this out and then pack up and head out into intergalactic space where they try to set up shop around rogue planets and stars and similar objects. Abandoned megastructures might be leftovers from the previous crop with the smart ones having left before the "event" got them. It would be an interesting thing to discover, because it would imply that there is a clock ticking.
Fun sci-fi plot: there is such a clock, and we discover that the event is random. We could have anywhere from zero to a billion years left. Our first interstellar probes find two things: megastructures that are abandoned, and dead worlds and megastructures full of alien space mummies. The intentionally abandoned ones seem to be more or less launch support facilities built to harness and beam exawatts of power for as long as possible in the direction of intergalactic space, following what seems to be a trajectory toward a distant tiny extragalactic star cluster...
I'd still take the discovering of an advanced civilization any day.
If it was no effort, why do it?
Its like, we could hunt don't people on some of the last unconnected islands and murder them. But why?
The aliens don't hate you, they don't love you, it's just that you (and the planet you're standing on, and the star it's orbiting) are made of atoms that can be used to build computers/more aliens.
Human intelligence seems as though it is fundamentally different, in that we can preserve and build on previous knowledge. So I'm pretty sure that aliens, detecting intelligent life, wouldn't just be like "oh, just some ants." Or if they are, we better hope we don't find ourselves in their pantry.
For all we know there is a space buoy of some kind out there some big units away...
"Non Contact Status: Toxic
Species shits where it eats, is actively killing one another, and has a basic nature of aggression and domination, and reproduce like weeds.
Planned status reevaluation + 100k yearly time type units"
Such a discovery could unify us in a way not possible right now.
As far as we know there currently is no higher entity in play. The moment there is... hoo boy!
That said, it seems reasonable to expect any civilization that gets interplanetary technology would also develop ICBM's along the way if they wanted.
Perhaps a certain amount of cooperation and kindness could be expected by anyone who makes it out into deep space. There's good reason to hope they'd be kinder than us I think.