We’re not just talking about life, we’re talking about intelligent life. Which, even so far as we know it exists on Earth (allegedly, anyway), we know for a fact has existed only for a very narrow sliver of time relative to the history of the universe, the history, of the solar system, the history of Earth, and indeed even the history of life on Earth. So narrow as to be vanishingly small on just this one planet that we know about with actual life.
And I feel that my very specific house/garage/car metaphor is absolutely analogous. I might expand it to include, say, a neighborhood, but then we’d risk deviating into the realm of actual statistics and probabilities particularly if I name the neighborhood), based on the data we have for the existence of cars in homes with garages, but which we do not have (data) for intelligent life in the universe.
Consider my house the entire universe beyond Earth: intelligent life either exists in it, or it does not. But we have zero evidence that it actually exists, and no data at all on what the actual probability of its existence may be in any given sliver of the universe we might select.
I have not foreclosed, for myself, the possibility of intelligent life existing elsewhere, but neither do I feel compelled to accept it. The time to accept such a proposition is some time after evidence of its truth exists. Which we simply do not have, only conjecture.
That’s fair. What I’m pushing back against is the argument that, since we don’t have any affirmative evidence of intelligent life elsewhere, than it must not exist.
My whole position is that there could be reasons we don’t see it other than the fact that it doesn’t exist. To me, the most obvious one is the sheer size of space.
But I do agree that this does not mean that a person should feel especially compelled to believe in intelligent extraterrestrial life.
My own belief is, admittedly, taken on some degree of faith - I don’t want to contemplate that, out of trillions of stars, ours is the only one that developed the ability to banter like we are doing now.
It is an argument against people who use the Fermi Paradox to posit that there must be some kind of 'great filter ', and that we are completely alone in our galaxy. I’m simply pointing out that there are many, many possible explanations for how there could be lots of civilizations in our galaxy that we have yet to discover.
Stop being condescending, I said GREAT filter. This is a notion popularized by Robin Hanson and extensively written about. A Great Filter is some big event that comes along and hits every planet before it can develop galaxy-colonizing civilizations. People have taken that to say, “If the Great Filter is behind us, we’re the lucky ones. But if it’s ahead of us, then we are doomed soon, because we are not far from spreading out into the galaxy, compared to the lifespan of the species.”
I’m simply pointing out that there is no reason to believe in a ‘Great Filter’ as opposed to any other distribution of smaller filters. In fact, because we can see so many potential filters, it lessens the likelihood of a single ‘great filter’ that every planet must pass through to have a civilization that can get to the stars.
Since we have no evidence for or against the existence of other civilizations like ours, I would use the Copernican Principle as a first step - assume we aren’t special, because every time we learn something new about the universe it emphasizes how un-special we are. I’m not sure why life on Earth should be held as something unique.
The fact that we haven’t found any others is almost irrelevant, because we have very little capacity to find other civilizations. We greatly overestimate our ability to spot other civilizations. JWST gives us some of that capability for close exoplanets, but even it can’t see atmospheres of Earth-like planets around Sun-like stars, and we’ve only measured the spectra of a handful so far.
Remember Tabby’s star? There was a lot of excitement that we might have found a techno-signature of a civilization. The star slowly dimmed over a century, and had periodic dimming just like a Dyson Swarm being constructed might. It turned out to be dust clouds. But the point is that this is the first time we found a star with a light curve like that, even though there are probably millions like it. It was only about 1100 light years from us - almost in our backyard, galactically speaking.
What is there about that event that makes you conclude that if there were civilizations in the galaxy making Dyson swarms we should have found them by now? We found Tabby’s star by fluke. There could be a hundred more of them just in our little corner of the galaxy, and we wouldn’t know it. A Dyson swarm on the other side of the galaxy? We might never know.
Nope. The Great Filter hypothesis was presented as an answer to the Fermi Paradox. It doesn’t even say the GF is ahead of us. Perhaps the Cambrian Explosion was it, or the Great Oxygenation Event, or the development of life itself. In which case, we already passed through it, so it would not have anything to do with what we do from this point on. The risks we face are our own, and the great filter theory says nothing about them, because it makes no claim as to whether the filter is ahead of us or behind. It’s useful for fear-mongering, I guess.
Without the Fermi Paradox, there’s no reason to even talk about filters, because maybe there’s no filtering going on. It was always proposed as an answer to the Paradox.
I’ve forgotten more about poker than you know. I don’t need a lecture on how poker works. I simply brought it up as an example of how you can get from a large group down to one person without a ‘great filter’.
If you’d like a different analogy, imagine a line of soldiers walking at another line while shooting at each other. You can start with 100,000 men, and slowly with each step some will fall until there’s only one standing. No ‘great filter’ came for them. Just a lot of little ones.
A ‘Great Filter’ would look like this: The soldiers start walking towards a destination, knowing that no soldiers have ever made it. They know that somewhere out there is a tripwire which releases nerve gas that kills them all. The soldiers are all hoping they’ve passed the tripwire, in which case they got really, really lucky and will be the first to make it. But as they get closer to their destination they get more nervous because if they hadn’t passed the tripwire it must be coming up very soon…
I’m saying there is no reason to believe in one big killer of civilizations that all must pass through, as opposed to civilization being very, very unlikely for a host of reasons big or small. Maybe there are lots of bullets, and not one big bomb.
Colonize? I’m not sure, if we are talking about self-sustaining worlds. Live on? Probably. If we don’t destroy ourselves or crater our economies with foolishness nd set ourselves back a hundred years.
It don’t know what will happen. But you are talking as if going from colonizing the solar system to colonizing another star system is just a logical progression. In fact, the distances are so huge, the energy requirements so vast, and the time required so long that it’s a problem of a completely different order.
I think it’s entirely possible that a civilization could spread to multiple planets and moons and asteroids in its own system, and never reach the point where it could do anything but send tiny probes to other star systems.
And if civilizations become so amazing at manipulating mass and energy that they can colonize asteroids, why go to another star? Thaere may be more rogue planets than stars in our galaxy. Why not just move onto one as it’s passing by and burrow into it? Many would be full of heat energy, radioactives, etc. Maybe the universe is full of populated rogue planets. And we’d never know, because they are using internal energy and not radiating away much heat, or any more than such a planet would radiate anyway.
It is a slightly tricky one. But basically, if conditions are the same across time, then if you grow 10% today, then you grow 10% tomorrow as well. And if they’re the same spatially, then your neighbor must grow 10%, and so must any newly created things. Finally, as long as there are enough of you, then it doesn’t matter if you grow by 10% or have a 10% chance of growing by 100%, or have a 1% chance of growing 1000%. The numbers work out the same.
Atoms decay exponentially because they don’t have a little “timer” inside telling them when to go. Instead, for each time unit, there’s some probability that they’ll decay. All atoms of a given type are absolutely identical, and nothing changes over time. So the decay curve looks something like 0.999*0.999*0.999…, for each timestep.
Of course, a galactic civilization will encounter different conditions as it grows too large. But in the short term, where there are many empty worlds to colonize, all statistically similar, the growth is almost inevitably exponential. Or the decay: it’s also entirely possible that a random spurt of activity–just a small fluctuation–drives some early growth, but that it almost immediately peters out. That might be the most common case, given the expected costs of interstellar colonization.
I find the central conceit of this one argument (that an intelligent species will expand) to be based on a very flawed sample of one absolutely insane species. What if all the other intelligent species are not like us and instead are sane, and are all “We decided 1 billion of us is enough. Leaves plenty of carrying capacity on our homeworld, for us all to live long lives of plenty. Now, you mentioned this word, war - what’s that?”
The species that don’t desire expansion don’t send out ships. Eventually a comet hits their planet and their population exponentially decays to zero. The end.
There are reasons to send out ships other than expansion. I didn’t say this hypothetical sane species doesn’t have the technological capability to expand, or a complete lack of adventure or curiosity. Or that all their 1 billion were necessarily on the homeworld. A sane species could see the value of “don’t put all your eggs in one basket” without accepting the “…therefore spread exponentially like a virus” corollary.
…and they handle it well because they don’t waste resources or efforts in selfishness or infighting. And they repopulate from the few survivors + the off-world scientists and adventurers.
The reasons are irrelevant. If every new colony says to themselves, “hey, we desire exploration, let’s send out a couple of colony ships to learn about the cosmos”, and each of those eventually turns into a full fledged civilization capable of and willing to do the same, then the civilization will grow exponentially across the galaxy.
Until eventually something does them in; maybe just the progression of their star along the main sequence. Our own sun only has around 500M years left before it gets too hot for us. Life on Earth is about 90% over. Let’s make good use of the remaining 10%.
To be clear, though, I was speaking primarily at the colony level. On a single planet, communication is fast, reliable, and high-bandwidth, so we can relatively easily detect when we’re reaching internal limits and put checks on our growth. At least if we’re not idiots about it.
But that doesn’t work on a colony level; communication is going to be slow to nonexistent. Colonies are on their own and will make decisions based on their own values. But if those values are similar to those of the origin civilization, then they’ll send out more colony ships on the same basis. If they manage a little more than one ship per colony, they’ll grow.
I agree with this. Expansion throughout a galaxy is not in any meaningful way the same as expansion throughout a planet and not something a truly intelligent species would attempt or plan for, IMHO. In fact, realizing no central control is possible given the very real constraints of vast distances, they may actively avoid it. Why plan for a far future scenario that would result in sub-populations with nothing in common with you and with many, many many generations to diverge in isolation from you, possibly to the point of speciation and creating a population threatening to your existence?
What exactly would be the game-plan of a civilization wanting to fill their galaxy? What’s the goal? To harness the total energy of their galaxy? I believe anything above a Kardashev Type II civilization is pure poppycock and will remain forever in the realm of science fiction. A truly intelligent species will realize this.
Unbridled expansion and conquest is a human trait. We may be intelligent, but we’re far from supe-intelligent. Being in homeostatic existence with your [controllable] environment is the super-intelligent thing to do (I say this with super-intelligent prescience ).
A super-intelligent species will set realistic goals for expansion. Perhaps expansion into a local cluster of star systems is doable and controllable and that would be the ultimate goal of any super-intelligent civilization. They would certainly have the wherewithal to control their population to be in homeostasis with their limited star-system environment in order to live long and prosper. What more could they possibly want?
This is a good point. Besides the reasons already given, there are other negatives to colonizing a fixed planet such as being tied down to a world that could suffer any number of unavoidable disasters such as asteroid/comet strikes, an unstable star, predators, and disease. By building large ships that are, in essence, self-sustaining cities, one decentralizes the population into many components that can spread out in many different directions in the galaxy. One disaster destroys one ship but not the entire species.
One possible goal for interstellar expansion would be to relocate to a longer-lived star. Red dwarfs will still be shining a trillion years from now, whereas the Sun will collapse into a white dwarf in a mere five billion years. A civilisation that really anticipates a long duration existence would want to move to at least one red dwarf in due course.
What would a Kardashev III level civilisation want with all that energy? They would surely be content with the energy emitted from a single star, or perhaps a few stars just for insurance. Well, I’m not so sure they would be limited by our meagre imaginations. One possible fate for an advanced civilisation would be to convert all decision-making entities into processors - in other words, a Matrix of virtual realities. These virtual reality environments could encompass astronomical numbers of thinking beings and utilise all available matter in one, or many solar systems. The computers could be used for other useful purposes, like calculating pi or something. Eventually all the matter in the Galaxy could be converted into computing substrate.
One big problem with such a scenario is the signal latency of such a galactic computer; about 100,000 years from end to end. But no-one said this would be easy.
That assumes a Kardeshev Type III civilization is possible, which is a big assumption.
And would any civilization really embark on an engineering feat that takes thousands of years minimum to reap benefits? Why, because you share DNA with the future beneficiaries? I care about friends and family and maybe a few generations of their offspring and hope they have a viable biosphere to enjoy, but that’s about it (oh, and I do like animals…the nice, cute ones anyway). DNA-ism is over-rated and antiquated. I share more than half my DNA with a banana, but that doesn’t stop me from eating banana splits.
I would agree with eburacum45 in that we don’t really know because we are limited by our meager homo sapien-centric imaginations. We tend to imagine galactic civilizations as the fictional ones in Star Wars, Star Trek or Dune or most other sci-fi. Various Earth-like planets with recognizable human settlements connected by “magic” technology that allows one to travel between them as easily as one might travel from New York to London.
If an advanced civilization mostly exists virtually or as some advanced AI (the differences being mostly negligible at that point), they won’t be limited to human time scales. For all we know, their physical interaction with the “real” universe may consist solely of sending out automated drones to grind up planets into raw materials to build solar panels and other constructs for the megastructures that house their virtual intelligence.
I mean, gosh, if there’s even a one in a billion chance, then it almost certainly must have happened! In one of the ~200 billion galaxies estimated to exist, with innumerable planets and chances for intelligent life going on to achieve Type III in each galaxy, you’d be kooky not to believe in the existence of a Type III civilization somewhere in the universe…
[/logic of the OP and way too many people in this thread]
Of course not; I’m not trying to claim we can see exoplanets (NB: there is a proposed technique to do this though, which is just astonishing if it is something that could actually be achieved)…
However, as imperfect as our view is, it does stretch out across the observable universe, so we can rule out some classes of megaproject already (unless we add on extra suppositions about cloaking technology and whatnot).
Actually, I think it is exactly the opposite way round.
For a “psychological” explanation (i.e. “maybe aliens won’t want to do X”) to be the primary cause of us not seeing evidence of ETs, we are making a claim about how all civilizations will behave for all of time, everywhere.
Meanwhile to acknowledge the implication of the lack of data, we need make no such claim.
I don’t even know what “behave like us” is supposed to mean in this context. Are humans, like so many SciFi alien species, culturally homogenous? Do all humans seek to expand their area of influence indefinitely, absent external force? Certainly some humans here see problems in unchecked expansion and would advise against it, so I think I can fairly conclude the answer to that is no. Do all human cultures tend towards unchecked expansionism, not just at some point in their history, but indefinitely? That’s an extraordinary claim if so.
Point being, I am not even satisfied we in this thread sufficiently understand humanity as it is an has been across this one planet, let alone purely hypothetical intelligent extraterrestrial life elsewhere in the universe, to go on making pronouncements about what is or is not within the realm of expected or possible behaviors.
For all intents and purposes, we’re just considering the Milky Way galaxy, not the Universe at large. Unless theoretical megastructures are possible (and not cloaked), we will not see signs of intelligent life in other galaxies.
So, how many extra-terrestrial intelligent (or super-intelligent) civilizations do you believe exist in the Milky Way? I believe few, if any. If that’s the case, then “how all civilizations will behave for all of time, everywhere” is a low number.
But that “unless” is already conceding my point: that we can rule out certain classes of evidence (e.g. uncloaked galaxy-scale structures anywhere within a few hundred million light-years)
I have no idea, and I think that your estimate has already been pre-seeded by observation.
That is, without looking at the sky, I don’t see anything silly about guessing that a million advanced ETs exist right now in our galaxy. There are a couple hundred billion star systems after all, and nothing in our current understanding that rules out a ratio of 1 advanced ET per 100,000 star systems.
It’s only the fact that we see nothing that mean even an optimistic assessment right now is normally hundreds or fewer per galaxy.
However, the point is, if one position requires making a claim about all ETs, and the other doesn’t, we should favor the latter.
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