Sure, but that gets back to what we know, we have not detected anything. Is that because
aliens are not doing things that are detectable
our current technology level is not able to detect the alien signals
aliens do things which are detectable, but the signal has not yet reached us
aliens do things which are detectable, but the signal stopped before we had a chance to find it
there are no aliens
I hope that, in order, the answer is 2, 3, or 4. As I think said up thread, and originally by some famous author, scientist, or philosopher, options 1 and 5 are both scary, but for different reasons.
On another tangent…
I think from evidence on earth, that technological intelligences are rare. In the 65 million years since the dinosaur killing asteroid, an intelligence has claimed to arise. In the 170 million years or so the dinosaurs were around, no technological intelligence arose. In the 600 million years or so of multicellular life, it’s only happened once.
(I’m counting all of the advanced tool using hominids as just one event, because they’re all closely related, with a recent common ancestor. Twice to me would be something like discovering Cambrian era construction, or a cephalopod civilization on the sea floor.)
Of course, the argument could go the other way… It only took 600 million years for intelligence to appear after the first multicellular life. The 3-5 billion years to go from single cell to multicellular might be the real filter.
Yes; I like all of these.
I like to collect solutions to the Fermi Paradox, and these all work, in various ways. But if the Galaxy is full of civilisations, there could easily be exceptions to each of them, assuming that not all civilisations develop in the same way over time.
I suppose that the ‘Dark Forest’ hypothesis could beat all of them, however - if a dark civilisation emerges early enough, it could suppress the emergence of later civilisations.
Right, but I, and eburacum45’s position, does not require asserting either way.
Whereas the position that ETIs are common requires making a positive claim: that zero species want, or have the ability to, make visible long-lived megastructures.
If we’re allowed to add on ad hoc suppositions, then any claim can be defended forever.
The simple point is, that the lack of observations of megastructures, probes, beacons / communications, or direct contact is an important data point. It’s telling us something…not an absolute conclusion, of course, but not something to be handwaved and ignored.
No-one has given a reason why SR-probes should have a fixed lifespan as a population
I’ve never found the concept of “they’ll be so alien, we won’t be able to communicate” very convincing but that’s a big debate in itself. So, for the purpose of this thread, we can put aside all the too-weird-for-Homo-sapiens-to-grok technology, and the Fermi paradox still remains for why no species has ever made grokkable tech.
And bear in mind how much work the word “grok” is doing here. We don’t need to understand what an object / entity is doing to recognize it as something different to the space around it.
Also not on board with that. We’ve done Dark Forest here before, and it was a big discussion. My position is that the game theory logic doesn’t work, and even if it did, it might well mean the galaxy should be more noisy, not less.
Anyway, we were talking about SR-probes, for which the Dark Forest isn’t really relevant.
This is essentially your first argument repeated again.
If we’re talking about hope, then I hope for the same. I would love for our galaxy to be a rich system of many ETIs with all kinds of strange and wonderful cultures.
However, looking at things with my rational hat on (it’s no fun…I should throw it out), the position that ETIs are common, yet zero times has anything been done that would be detectable to us, means asserting that no species has ever had the ability or desire to do such a thing.
This is quite a big claim to make, as our understanding of physics today is that it is relatively easy for a species to be noisy, or fill the galaxy with bric-a-brac.
I like to think the encroaching grey goo is just outside of our light cone, and we’ll soon detect it. Over the next few thousand years will watch as the number of solar systems devoured slowly expands, with a several millennia long debate over when exactly it will reach us…
A philosophical way to look at it: As far as we can tell, the universe is a series of never-ending complex systems. It’s comolexity all the way down. The Earth is a complex system of organisms, each of which is a complex system made up of innumerable complex systems inside of it. And that continues all the way down to the quantum level.
So what do we know about complex systems? One thing we know is that they do not survive unless they have limiting mechanisms to keep any one group of things from taking over the entire system. Complexity requires diversity. Nothing lasts forever, there is constant competition for resources and the system has a stability due to negative and positive feedbacks. In the history of Earth billions of organisms have evolved, and not one has taken over the whole thing. There are always forces that arise to stop growth.
Carrying that out to the next level above us, some sort of galactic ecosystem, we would expect to find forces that would prevent one species from dominating everything. Maybe our equilibrium force is distance - we just can’t get to each other. Maybe it’s the ‘dark forest’. Maybe it’s another principle of complex systems that prevents a species from expanding to many other star systems. Maybe, like other complex systems there are millions of factors which add up to a stable point where surviving civilizations can’t interact, because in the far past the ones that weren’t in that situation (say, they were crowded together in a cluster) wiped each other out. Maybe multiple galactic civilizations have risen and fallen until they were incapable of becoming galactic anymore, and we’re in that period of stability. Maybe the galaxy is a graveyard of dead civilizations, and the few that survived are the ones that were isolated from the rest - like us. Or we came along after everyone else was gone.
But the main point I want to make is that this issue is currently dominated by unknown unknowns. Recency bias makes us think that we must be near the pinnacle of knowledge and therefore should be able to understand why aliens are not here, but peoole have thought they were near complete understanding of science many, many times in the past. It would be silly to believe that there isn’t a whole lot about the universe waiting for us to discover - maybe we’re just getting started, and our Fermi debate is the kind of thing children talk about before they grow up and learn how the world really works.
One hundred years from now the debates over this may look imcredibly quaint and misguided, because we will have discovered new things about the universe that make our current understanding pale into near insignificance.
For example, when the Bussard Ramjet was first proposed, some people thought that not only would we be building them in the near future, but that the universe is probably full of them. Some people worked on methods to detect them. Then we discovered that the math didn’t work and you couldn’t get enough ‘fuel’ to counterpact the drag of collecting it.
There could be mathematical or physical reasons why self-replicating probes won’t work, and we just haven’t discovered them. What does the Fermi Paradox look like if we start with the assumption that self-replicating probes aren’t a thing? Is it still intractable?
I don’t think nature works as a good analogy here.
In nature, successful organisms’ populations increase rapidly until there is some limiting factor (e.g. predator adaptation, lack of food, limits of a landmass etc). The limiting factor was not the thing that made them successful though, it was the thing that ultimately prevented that species filling the observable universe.
And importantly, nature doesn’t think ahead. For example, the great oxygenation event made many species extinct, many oxygen-producing species. The price of success.
Organisms reproduce like crazy until they can’t any more…if the galaxy was in that kind of equilibrium we should see a whole menagerie of competing probes.
Now, of course, sentient species are not just mindless animals following instinct, by definition. I’m just saying, I don’t think this analogy works at all.
[quote=“Sam_Stone, post:275, topic:969972”]
And what’s the self-replicating probe FOR? What does it do once it’s spawned a copy of itself? Why would you even build such a thing? So you can die happy knowing that you’ve set a course for machines to eat the galaxy? Just because we can imagine something doesn’t mean someone out there will do it. [/quote]
Good point. You did a great job pointing out the incredible complexities of having one probe replicate planetary supply chains. One possibility is that we are the self-replicating probe. Or rather, some kind of proto-RNA that landed here long ago, with a very vague “instruction” of “protect and nurture increasing levels of complexity” or “fight entropy”. That means protecting life over dumb dock, protecting multicellular life over unicellular life, more intelligent life over less intelligent life, mice over beetles, dolphins over tunas, dogs over mice, (imaginary) super-intelligent hive-minds over single human minds, etc.
The drawback of such a probe is that It’s an extremely low “resolution” message “fight entropy” is very vague. The advantage is that it’s cheaper to send a rock with some frozen RNA in it than anything else I can think of.
The other thing I was thinking about is that, If there is to be omni-directional interstellar communication, the only way I can think of is by using the local star like morse code by causing small dips in luminosity at clearly artificial intervals, or using color encoded messaging (someone mentioned crashing different elements into the star to encode msges in its spectrograph changes earlier in the thread). The result would be extremely laggy, likely unidirectional communication with all the caveats related to the speed of lights and vastness of the universe. It sounds like a fruitless endeavor requiring a lot of effort with no payoff unless you’re a species that lives for millions of years.
I don’t necessarily disagree with the specific points made about SR-probes here (by Gozu, and Sam_Stone), but let’s not lose track of why we’re even talking about them in the first place.
The post that re-opened this semi-zombie thread, was one suggesting that there has not been enough time for ETIs to reach earth or contact us.
SR-probes are an example of a means by which a species’ influence could spread very far in a short time (cosmologically-speaking).
So, no, in fact there has been ample time.
If we wish to argue that species will choose not to make SR-probes, or any other detectable technology, then fine, but that’s a different argument to “not enough time”.
Well I say “fine” but, like I say, the issue with all psychological solutions to the Fermi paradox is they require universal consensus, in a quite literal sense (Ok, “galactic consensus”). They need all civilizations, everywhere and always, to come to the same conclusion.
Whereas, simply asking why we don’t see such technology does not require making any assertion about how all aliens think.
I’m not sure it’s clear that the “no SR probes” option is a choice or an inevitable result of the massive resources necessary to make them a reality.
Some of the posts in the thread suggest that such things are just around the corner, when we have spent a decade trying to get a self driving car that won’t run over a toddler, and aren’t even there yet. SR probes have to fly through space for 10,000 years, land on a planet, and still function well enough to find the resources and energy necessary to build and launch multiple interstellar SR probes.
That may be a level of resource manipulation that just isn’t attainable for a civilization that is restricted to the resources available on a single planet or solar system.
Round the corner cosmologically-speaking.
If it takes 10,000 years to implement then that’s the relative blink of an eye.
In the context of the Fermi paradox, we need hard to problems to be “hard” on a scale well beyond that which we typically consider. We need problems that are unsolvable for millions of years i.e. thousands of times all of human history.
That’s why, in my opinion, it’s not even worth talking about engineering challenges in this context. We’re unlikely to even be aware of the problems that present engineering challenges to advanced ETIs. The only objection should be belief that something is physically impossible.
Right, but you are talking about decades, and we are talking about millenia or more. Do you think that we will have the self driving thing licked by the year 22022, or that it will still be beyond our grasp?
No, they don’t actually have to do any of that. They may fly for decades at most, then land on an asteroid, not a planet. The resources and energy they would need at that point are right there.
Once again, an argument that it seems hard to us now, so no one will ever do it, no matter how many billions of years they are given the opportunity to do so. I just don’t buy how you can know the absolute limitations of every single form of life in the universe.
And that’s just one of many ways that a sentient space faring society would make itself visible to the rest of the universe. Others have been discussed in this thread, and have been dismissed with the same form of argument from incredulity.
But, this goes in circles, one of the reasons that I don’t check in on this thread often is that there is no progress. Obviously, part of the reason is that neither side has any evidence to present, so it’s just about logical arguments based on what little we do know.
When arguments are made that invoke what seems hard to us now, and imply that makes them impossible for all time, I don’t consider those to be valid conclusions. Demonstrate the hard cap on technology that makes it impossible for us to ever colonize another orbiting body with technology or people, or provide evidence for the wall that surrounds the solar system that prevents passage. Something that doesn’t make it hard or unlikely, but utterly impossible for us to ever leave the solar system.
Don’t try to explain from a psychological perspective some reason as to why they may not expand. Explain why not only that we humans, not a single one of us, will ever choose to expand, but why that binds every single other species in the universe as well.
People have used the cup of water from the ocean analogy incorrectly. We don’t look at a cup of water from the ocean, see no whales, and determine that there is no life. There is a lot of life in a cup of ocean water. No whales, but you can certainly tell the difference between a dead body of water and a living one by a single cup. It seems then the argument becomes that we should assume that there are whales out there, and even though the evidence indicates that there is no life at all, that is handwaved away by the argument that the ocean is so big, it must contain whales.
I consider there to be three valid answers to the Fermi Paradox.
Oh, there they are, problem solved.
Why it is impossible for us or anyone to ever leave their home planetary system, or to affect that system in a way detectable from far away. (Keep in mind that Tabby’s Star tells us that we can readily detect the building or destruction of a Dyson Sphere within 1200 light years.)
We are the first, maybe only, technological society within several billion light years. Someone has to be, and they would see a universe devoid of life, just as we do.
As of yet, while there are many who seem to be arguing for #2 on the list, no one has presented any form of evidence or logic to actually back that up, just arguments based in incredulity.
At the moment, we can dispense with #1, because if there were many technological societies and technology can straightforwardly bridge interstellar distances, we would see them right now and we do not.
#3 is the “humanity is super special” theory, that in 13 billion years, and billions of stars and planets in the Milky Way, we’re the only form of life that developed technology. This seems to be quite the claim.
#2 is, essentially, “there are limits to engineering”. This concept should not be thought of as magical thinking. It might be wrong WRT interstellar activity, but it isn’t ridiculous.
Things like Dyson Spheres, Self Replicating Interstellar Probes, and FTL travel are stories written by imaginative writers. There is no apparent engineering path to any of these things, people made them up. I once read a story about an alien artifact that was billions of years old, never needs fuel or repairs, and could function while resting comfortably on the surface of a neutron star. Imagination is limitless, engineering isn’t.
I mean, there seem to be several other possible explanations (maybe not necessarily “solutions” to the Fermi Paradox):
The signs of intelligent life are out there, we have just failed to recognize or detect them. If a Dyson sphere takes 100,000 years to build, would we be able to detect the construction of one? We might be getting bombarded by a thousand messages continuously from other civilizations and we are are just oblivious to them.
Interstellar travel technology is feasible, but technological societies are inherently unstable and will eventually collapse (eg. the “L” term in the Drake equation is small) - Earth could have been visited by 100 self-replicating probes from 100 different alien societies, but if they all happened hundreds of millions or billions of years ago we would never know unless they were designed to last indefinitely. If the average interstellar society lasts, say, 1 million years, even if there have been 100,000 interstellar civilizations in our galaxy over its history, it’s possible that none of them will overlap us temporally.
The Wikipedia page on the Fermi Paradox lists all sorts of other arguments, such as economic explanations (eg. there are models that exist that show that colonization could be constrained to clusters, based on percolation theory - perhaps Earth happens to be in a dead zone).
Agreed, I’m just saying that the debate stops if we find them out there, or here, or anywhere. We, at that point, will know the answer, and no longer have any need for speculation.
Why is it quite the claim? Someone has to be first. The odds that someone is first is 100%. If the odds against anyone developing are huge, then, in a large enough or infinite universe, there would be some who develop, but not anywhere near others. And by not anywhere near, I don’t mean thousands of lightyears on the other side of the galaxy, I mean many billions of lightyears outside the observable universe.
Okay, explain those limits then.
I’m not sure why you chose to throw that last one in there. I never said anything about FTL.
And the other two are plenty plausible. We are slowly building a Dyson Sphere right now. Every satellite or planetary probe is one more part of it. Explain what will make us stop adding to it.
As far as Self Replicating probes, those are the lowest on my list of ways to see other intelligences, but I’ve yet to see anyone explain why we can’t make them. We can make a probe out of the raw materials we find on Earth, but for some reason, it is utterly impossible to make a factory that will make a probe anywhere else in the universe. I don’t see why that is the case.
And no one is saying anything about anything like that. Everything is grounded in the physics that we know and understand.
Right, but I’m not saying anything about limitless, I am talking about specific things, things that there is a well defined, if long, path to.
It is entirely those who claim that we can never do these things that invoke stories of science fiction as a strawman to argue against, rather than against the actual arguments made here. You have to posit all sorts of new laws of physics and impose specific psychologies on all the aliens that you believe are out there in order to create your fine tuned universe. I am not making any of those assertions or assumptions, nor relying on science fiction stories to make my case.
Yes, if it were within 1200 light years, we would. And if it takes 100,000 years to build, then they should have finished it millions of years ago.
And then they should have done the same to their neighboring stars, and the neighboring stars to them, and their neighboring stars…
Okay, I suppose I accept that as the pessimistic option. That we will kill ourselves off before we get off this planet, and so does every single other form of technological life out there. I find it a bit implausible, as it’s making a statement that must apply to everyone, no exceptions, but it’s more reasonable than assuming that we will suddenly stop wanting to expand our resources and living space, or that there are undiscovered laws of physics that will prevent us from leaving the solar system.
When Rome fell, it didn’t take the whole world with it. It didn’t wipe out humanity, and had barely an effect outside of Europe and Western Asia. What are you thinking that would wipe out an entire species, that is separated in time and space by hundreds of more orders of magnitude than Rome was from Tenochtitlán? One that would wipe out every world, colony, ship and individual?
Yes, I’ve read that page, and as I said, I don’t find those to be plausible to explain why every single alien society stops growing. They may explain why some alien societies failed or stopped growing, but explaining all? Not really.
Of course someone has to be first, assuming there’s multiples in the offing. We have gone from inventing the wheel to sending a probe into interstellar space in .0001% of the age of the Milky Way, and the suggestion here is that in the prior 99.999% of that time no other life managed it. Certainly it’s possible, but is it likely? These are not numbers that suggest we’re the first in a string of civilizations to me, they suggest we’re the only ones that are going to happen. Which is also fine, I just don’t see that as the likely answer.
You have to build everything out of atoms.
If I told you that we have to build everything out of wood, leather, and quarried stone, we wouldn’t have skyscrapers, automobiles or rockets. Those materials have inherent limitations that preclude building, let’s say, a Saturn V rocket. Atoms are certainly more flexible, but they are physical materials with physical limitations.
Is it possible for atoms to be arranged in such a way as to form a spherical surface 1AU in radius, 1 foot thick, and be structurally sound?
It’s 100% likely that someone is first. I don’t see any reason to think that we are lucky that it’s us, as it had to be someone, and that someone would be the ones looking around wondering where everyone else is.
It’s like winning the lottery. It seems unlikely to win, but if you limit your sample size to lottery winners, then it becomes 100%
Well, I also don’t think that we are first by just a hair. I think that we are first by trillions of years, that if life becomes prevalent, that it’ll be more when the universe is middle aged rather than in its relative infancy.
I also think that, if we do do what I think we can do, then we will also prevent life from evolving on other worlds within the observable universe, either intentionally or unintentionally.
Probably not, but why would anyone do something like that?
Ah, I think I misinterpreted how we would detect the construction of Dyson spheres - I thought it was by observing the dimming of a star over time, in which case seeing a 0.001% reduction in intensity of the star per year would hardly be noticeable. How should we be able to detect the presence of an already-built Dyson sphere?
No, the premise is not necessarily that every civilization kills itself off before they leave their local system, but that they kill themselves off eventually (or at least, eventually evolve to a point where they aren’t able to or don’t wish to expand). It is not at all inevitable that if interstellar travel is possible, that therefore technologically advanced exploratory civilizations must exist in perpetuity, and are ever present in every location that they have visited in the past.
You don’t need some sort of galaxy-purging event - all that’s required is something that prevents exponential growth indefinitely. I don’t see why you can’t have localized pockets of a galaxy where intergalactic species are spreading exponentially, while other pockets that they had previously inhabited are declining exponentially. Just because some civilization has developed the tech to achieve interstellar travel and colonization doesn’t mean that all the civilizations descended from it will maintain that capability.
Well if there needs to be a certain resource density to sustain exponentially spreading intergalactic species, and our region of space doesn’t have that density, then that could explain why our area of space hasn’t become overrun with extraterrestrials while still leaving open the possibility that they could exist elsewhere.