That would be funny! It would mean they emerged right after the Huronian icehouse period ended, in the same way the Cambrian Explosion happened right after the Cryogenian period ended.
IIRC this was associated to an early, brief spike in atmospheric oxygen. It went up, fell, and then took about one gigayear to increase again to large sustained levels closer to what we have today. Large organisms have low area to volume ratios, and require a high level of oxygen to scale up while producing enough energy. See https://ars.els-cdn.com/content/image/1-s2.0-S16749871120008...
If true, and complex life evolved more than once on the same planet, then it is much less likely as a strong candidate for the great filter [1].
So, very roughly, either life is hard to get started at all (but life started about as soon as possible on earth), intelligence is hard to evolve (although we see many species with intelligent behaviour, if not at human level), or it's in our future (that intelligent life tends to destroy itself).
No, the argument here is specifically about the great filter. I know there are other possible resolutions to the Fermi paradox, although I haven't found most of them very convincing.
I mean the most obvious solution to the fermi paradox is just that aliens are hard to see. If we put an equivalent human civilization even on one of the explanets we've identified, we'd never know it. Our signals are simply too weak and disorganized, and the switch to digital has made them even harder to identify from the background. Planets are located right next to huge sources of radio noise: stars.
Until we can reliably detect a species like ourselves on another planet, it seems very silly to assume they aren't there.
The assumptions on detection all kind of assume that aliens that are much more advanced will have much more obvious signals of emery usage or other detectable signals, but I've never been convinced by these assumptions. Energy usage is likely a logistic curve rather than an ever expanding exponential. There so much room at the bottom for greater efficiency. It also seems quite sensible that a species either eventually copes with equilibrium or dies out due to issues with unchecked growth.
There's SO MUCH energy available here on the earth that we could go for millenia of computational/energy growth while pursuing more efficient systems. The assumptions that lead to conclusions about megastructures are pretty dubious. I could go on at length about that, but I will just leave it at that.
It only takes one life form to achieve interstellar capability, and they would spread across the galaxy in only a few million years. That doesn't seem to have occurred (although, maybe it has and as you say, we just can't detect them, and they're leaving us alone).
Yeah but IMO expansion via "interstellar capability" is just not compatible with a civilization.
As our species has developed, the time scales that matter to us have shrunk, not grown. I just don't think you can have a single coherent civilization work when relativity places such stringent limitations on communication speed. A super advanced civilization likely evolves and changes on much smaller time scales than ours does currently. It doesn't seem possible for such a civilization to not totally fracture at interstellar scales.
Unless there's physics we don't know about, interstellar distances are probably just not really compatible with a civilization. So, if one exists, its probably a serious rarity within a rarity. i.e. the lack of observable existence of such a noticeable civilization does not make a good argument against aliens in my opinion.
It's a good point, but there is no reason to suppose they have to be a unified civilization. Just that they can spread in the first place and their descendants can do the same.
I'm not so sure I agree. There is nothing stopping a species that experiences years as we do minutes. Such a species would have no problem with the time scales needed for interstellar travel.
A fun problem with this is that there are 500k minutes in a year, so the critical free minutes needed to get into orbit quickly would be like working at nanosecond scale... Our slow friends would presumably need 100% automation to survive just about any kind of launch. (Nevermind landing.)
(This also raises for me a fun way to continue Moore's law by making lived experience slower...)
> time scales that matter to us have shrunk, not grown
I don’t think this seems right. More realistically, the further back into the past we look, the more we notice people, institutions, and changes operating on longer time scales, partly because our knowledge becomes much less granular the further back we look and partly because slower changes are less noticeable or impressive when examined from partway through without the benefit of hindsight.
Unless you just mean that with improved technology we can now do a better job inspecting and sequencing things that happen very quickly. That’s clearly true, but is substantially unrelated to human-scale goals or the behaviors of larger organizations.
Or maybe any number of things can go wrong within a million years that prevents the few species capable of interstellar travel from unbounded exponential expansion, including but not limited to said species not wanting to engage in unbounded exponential expansion.
Mathematicians always seem to assume that reality is as simple as a plot on graph paper, but if that were the case we would have had hotels on Mars by now.
Perhaps there is some obvious direction in which to engage in unbounded exponential expansion, more attractive than exploring the galaxy - not full of vacuum and vast distances and cold rocks. Everybody else is exploring that space instead, and we haven't found it yet.
Or, quite reasonably, human-like intelligence is special and galactic-scale rare. Do we think every other kind of unlikely life exists elsewhere in the galaxy? If there are definitely other human-like intelligent life forms in the galaxy, then there are even more definitely flying pigs with nineteen legs and wheels on the ends. Does it feel so intuitively correct, considering that? The argument here is "but orangutans ... and crows and parrots ... and dolphins ... and octopuses ... and elephants ... they all abound with the potential to build rockets and electronics and self-replicating space probes. Any million years now, any one of those species could flip into producing lots of ideas and constructions and exploring everywhere." But, really? Sure, they do stuff with sticks and half-coconuts, but is "the parrot/octopus/elephant space program is just around the corner" really a parsimonious extrapolation from observed animal stick-handling?
Besides, nerve cells only evolved once, maybe that was a freakish event. Maybe every other animal in the galaxy is a sponge.
I think the simple answer to that is that the distances are simply too vast (and they are expanding). FTL is impossible and even approaching light speed is not economically feasible. That limits any spacefaring beings to their local planets, pretty much, and if our solar system is at all representative, the majority of the planets are uninhabitable.
We are already planning interstellar probes that appear feasible with only modest advances [1].
Imagine what we will be able to do with another 1000, or 10000 years of development. Can't see any fundamental reason why we could not ultimately build infrastructure and print up some lifeforms at their destinations.
Orders of magnitude are unusually easy in our industry. These are absolutely mindboggling numbers beyond comprehension.
You need to move 500K hiroshimas a second for 80 kg (175 pounds). You'd also need some pretty fast brakes lest you run into some pretty small things. You also have a really bad recursive problem, at 100% E=MC^2 efficiency, you need to turn 100 kg of mass to pure energy, per second, to move 80 kg. So actually you need to move 180 kg, which requires...etc. etc.
This is the base of this thread, the Fermi Paradox: if it was a relatively quick scaling away, where is everybody? It's "turtles all the way down" to respond that there is no paradox, just imagine us in 10K years, even if we knew for 100% certainty we'll be there in 10K years.
Note the wikipedia article you linked uses "concept" 10 times, the roadshadow was in 2016, and has no updates after November 2017, 6.75 years ago.
At the same time it only takes one civilization making Von Neumann probes change the equation from soft fragile biological life to things like spreading probes that don't care quite as much about the conditions.
Technological feasibility is not economic feasibility. We spend a minuscule amount of our resource budget on science without short term profit .
There are orders of magnitude of things we can achieve as a species with current technology if we all work together efficiently but we don’t .
We ascribe to aliens a singular purpose that we have never achieved in our history as a species.
Our competitive, acrimonious past is fundamental to our scientific progress (we research more during war than peace) . A peaceful civilization may not reach technologically maturity.
It could also be just that Interstellar travel is not simply be economically viable in time frames that those civilizations optimize for. Ours can barely look beyond a quarter, why do we think any other civilization would plan for hundreds if not thousands of years .
It takes both technology and motivation. Why populate the next star system? Why the next? And the next few million? You need technology developed by a civilization with the need or desire to expand infinitely. Humanity's only motivation to send people out to suffer the deprivations of frontier life and colonize another star system is essentially religious, either owing it to the universe to spread life and preserve humanity, or the belief that life for our decedents would be better off if we cast off the old society and built a new one. Would this really drive us to millions of stars?
> If true, and complex life evolved more than once on the same planet, then it is much less likely as a strong candidate for the great filter [1].
The hard step was not complexification of life. It was long-term atmospheric oxygenation. It took two attempts, the first one short-lived, and between 3-4 billion years to finally succeed for good.
It's not necessary to assume a single hard step to explain the rarity of intelligent life. Considerations about the late appearance of a technological civilization on Earth point to between five and six hard steps from origin of life to us. Abiogenesis can account for one, oxygenation for another, and we still need to find another three or four more. See https://arxiv.org/pdf/0711.1985
That that paper is one (very good) explanation for the early and sudden appearance of life on Earth, despite it being presumed a rare phenomenon.
But there are other possible explanations.
About the Great Filter, in principle we can expect the probability of those things to vary by several orders of magnitude, so only one would qualify. All of them being equally unlikely is actually harder to explain than the alternative.
Well true, the great filter may not be the entire explanation for the Fermi paradox. It seems uncontroversial though that the probability of each of the steps to get from lifeless to intelligent life will be a factor.
Possibly, but there's almost no way to meaningfully weigh any of the factors -- we still can't say to any degree of certainty whether the emergence of unicellular life in the cosmos is common or exceptionally rare -- so it's useless as a predictive tool, and highly constraining as a thought experiment.
You say there's no way to weigh any of the factors, but the point of my original post was that the emergence of complex life more than once means that step is not as hard as it could have been.
We also now know that the creation of organic molecules is commonplace in the cosmos.
True, we don't get any predictive power from this. We're just exploring the space of possibilities, and there's still a lot of unknowns. I still see value in a thought framework like this to guide that exploration, but maybe there's a better approach?
The evolutionary transition from single-celled to multicellular life has actually been repeatedly accomplished in vitro [1]. So highly unlikely to be a Great Filter.
The study in the article suggests that these early multicellular organisms failed to take hold. So there was probably something needed that was missing. And it still took billions of years for complex live to emerge, whereas single celled life appeared almost immediately once the earth cooled down enough to have liquid water. Whether it took two billion years or 3.5 doesn't matter so much when you think of it as a potential filter.
There are so many more possibilities. The entire topic of the Fermi paradox is a massive tower of assumptions and hidden variables for which we have no information.
We don’t even know the paradox is real since we haven’t explored our own solar system enough to rule out aliens or artifacts of their visits in our back yard, nor can we rule out advanced observers intentionally not revealing themselves for any number of rational reasons. There could be an abandoned underground alien base on the Moon and we’d have no clue. We have barely gone anywhere.
If we hit, say, the level of development in The Expanse and still find nothing (no protomolecule haha) then maybe we can say there is definitely a paradox.
There’s also the assumption that there is a single discrete big and dramatic great filter. That’s the Hollywood version. In reality there could just be a continuous probability of failure due to any number of events whether endogenous or external spread across billions of years that amounts to a great filter. The probability per day of “biosphere failure” or some other condition that dooms a potential spacefaring intelligence doesn’t need to be high to amount to a probability near 1.0 over geological time scales.
Let’s say given we are sending our probes and capsules we are probably at least 50% of the way there. If the cumulative great filter were near 1.0 probability of failure this would imply a 50/50 probability of our success. Those are of course made up round numbers just to illustrate how that would work. We have no way to know what the actual numbers are because we have a sample size of one.
The whole thing is just speculation until we have more actual data.
Well, the Fermi Paradox is misnamed because it isn't a paradox at all. It's just the observation that we don't see evidence of other life out there, and wondering why not - for which there are lots of possible explanations.
As you say, we don't have enough data to know one way or another, but even when we do, there will still be no paradox.
The sheer number of stars in the galaxy and the absence of evidence of other life are in apparent contradiction — hence a paradox. A paradox doesn’t necessarily mean a hard logical contradiction.
But this is not even a soft contradiction, or even an apparent contradiction. It's a problem with too many possible solutions so we don't know which one to pick. A paradox appears to have no solutions (until it's solved).
Given the number of stars, you would expect evidence of other life if life isn’t exceedingly rare. But we have no particular explanation why it would be exceedingly rare, and given the abundance of life on Earth one wouldn’t expect it. So the fact that we see no evidence runs against our expectations. Nonintuitive observations, where the observation doesn’t provide any explanation, already counts as a paradox.
A better term would just be “mystery.” If you assume life is at least somewhat likely and do some simple math we should see evidence of aliens. We don’t so something is either wrong in the assumed probabilities or there are unknown unknowns.
My favorite hypothesis is that we are early. Due to low metallicity in the early universe it’s possible that advanced life only became likely “recently” (as in the last few billion years) and we are part of the first crop. We may be an early example in the first crop because our planet is particularly friendly to advanced stable life, so maybe a bit of rare Earth mixed in. Most other biospheres might be more hostile and take longer to produce anything capable of space flight.
We don’t see star travelers all over the place because for the most part it’s too soon. There might be a few early birds out there but few intelligences are that advanced yet.
It's popular to suggest we don't hear aliens because they all destroyed themselves. But a basic RF link budget calculation shows that even an Arecibo sized antenna pointed perfectly at another Arecibo telescope on an alien planet, and listening/transmitting at the exact right times, could only barely contact one or two of the nearest stars.
This fact is buried in all the Fermi Paradox discussions because Fermi's point was the implications of his work on nuclear weapons when he brought up alien contact.
It has since been used to make the case for Reagan's Strategic Defense Initiative. Which apparently Elon Musk is now continuing... https://ioc.exchange/@muskfiles
I think people, for both good and bad faith reasons, vastly underestimate how unlikely it would be for any sort of artificial signal to reach us.
It would need to be so powerful and so precisely aimed at us that firing randomly into the void would be pointless. We can barely detect the most energetic events in the universe like quasars and gamma ray bursts as it is.
And that assumes we could even decode it -- advanced coding uses scrambling techniques that deliberately make the signal look like noise to the uninformed receiver...
presumably nowadays we would only aim at stars with a planet with an atmosphere we might at least suspect to be influenced by biology (i.e. contains some gas that couldn't be formed and maintained by known geological processes). so maybe aliens would see oxygen in our atmosphere and aim at us - but you'd still have to get the timing right: we might have been burning witches the last time one message came by and next time we might be in the midst of some other social disturbance.
The Fermi paradox does not merely concern the lack of alien signals - it also notes the peculiarity of the absence of alien spacecraft / visitors. The Milky Way is big, but not so big that it's impossible to traverse generationally. If interstellar spaceflight capable aliens evolved at any time in the galaxy's 13 billion year history other than within the past, say, few million years - a fraction of a percent of the total - then we should expect them to have colonized the galaxy by now. There is 0 evidence that this has happened - no monoliths on the moon, no Dyson sphere signatures visible in our telescopes. Either they're very quiet for some reason, or nobody cracked interstellar travel. That's concerning when it seems perfectly possible and desirable to do. The Milky Way is big, indeed - big enough and old enough that someone should be here.
> The Milky Way is big, but not so big that it's impossible to traverse generationally.
Creating a self-sustained ship is not so easy. And there are tons of failures that can happen, especially over the course of multiple generations. And you won't be able to just "beam down" to some random planet once your interflux quantum capacitor and its two backups fail. Unlikely things happen given enough time.
And why would you want to do this in the first place? Would life on such a ship really be all that great? Sounds like the stuff of a depressing dystopian sci-fi novel more than anything else.
Dyson spheres seem completely impractical. Just the sheer amount of materials needed alone, never mind the construction effort and maintenance effort. Dyson himself didn't take it very seriously, and I have no idea why anyone else does either.
All very relevant points to why human generation ships are unlikely. Totally irrelevant points as to why, out of the hundreds of billions of planets in the Milky Way, it would appear that not one has evolved an organism capable of spreading out of its gravity well. In general, Life Finds A Way. Life on a ship is depressing? You may as well argue that life in hydrothermal vents would be boring.
As for Dyson spheres, don't take the remark so literally. I simply meant that a galaxy-spanning slime mould would probably be visible to our physics, somehow. Life is an entropy engine. Once it gets going, it really gets going. But we appear to live in an improbable oasis in a vast desert.
Most of those "billions of planets" cannot support life (the exact number of which can is currently unknown). And who says no life evolved "capable of spreading out of its gravity well"?
> As for Dyson spheres, don't take the remark so literally.
Of course it should be taken literally, because all of this is all about what the laws of nature do and don't allow and the practicalities surrounding that. This isn't an class or discussion about what does and doesn't make a good sci-fi story. And what is a "galaxy-spanning slime mould" even?
> Life on a ship is depressing? You may as well argue that life in hydrothermal vents would be boring.
Yes, it would be. There is no intelligent life living near thermal vents. What an odd thing to say.
Maybe aliens just aren’t interested in exploring or traveling.
Maybe they reached space but upon finding it inhospitable, decided it’s not worth the trouble. Doing things because they are hard could be a uniquely human trait.
On the other hand, I’ve seen a UAP with amazing abilities. Maybe they are here already but aren’t in a hurry to say hello. Maybe they think we are too primitive to warrant communication.
Maybe their signals are all around us but we don’t have the means to detect or interpret them.
Maybe they only use lasers and fiber optics to communicate.
*The Golden Age" trilogy by John C. Wright explores a future humanity where we have tamed the solar system, become as gods, and really can't be bothered with populating the galaxy because it isn't all that interesting compared to the awe inspiring realities of home. Apart from that one time required for an interesting plot. The solar system is pretty big.
You speak as if there's possibly one or two alien species. But there are hundreds of billions of planets in the Milky Way. Even if life is 1 in a million, we should expect hundreds of millions of life bearing planets. The place should by rights be teeming. What are the odds that none of them want to explore and colonize? Is this an evolutionarily stable equilibrium we find ourselves in?
I think that, given the scale of time and planets that could potentially be habitable, there is a high likelihood for the existence of many alien species.
What I take issue with is the notion that it should be surprising that we haven’t detected them. There are so many reasons why they could be right in plain sight, not even trying to hide themselves, while still going undetected. Those explanations are under appreciated in my opinion.
One issue that's become clearer since Fermi's time is just how not-empty space is. There's enough rocks and dust and rogue planets between the stars that any ship traveling at even a small fraction of lightspeed could be instantly destroyed if a collision happened, even with a particle the size of a grain of sand.
And it's dark so you cannot see it coming. You'd need very high frequency radar or more likely lidar to detect it and you wouldn't have much time to dodge it. (Not to mention that you have to design that lidar with relativistic effects in mind.)
The density of this stuff is not high but it's not zero either.
Scalable interstellar space travel being infeasible for lifeforms and even robots in a way that could actually be useful (given distances, odds, 2 way communication, short time windows between extinctions etc) seems way more likely explanation than intelligent life being impossibly rare.
Is it possible to find their remnants in the genome? Since horizontal gene transfers happen other organisms that survived carried the information but perhaps it's too scrambled now.
So far no reasons to think so. The article lacks details. But for complex life to emerge in small pocket that oasis would have to exist for many millions of years. No proof of that. Then organism is not a bunch of single cellars in one place. This is another question here. Next there are intermediate forms of life which bundle together only for some time. This thing looks like single organism while it isn't.
Meta: Why are all the comment timestamps in this thread no older than 5 hours, when some comments are over a day old? You can verify this by looking at some user pages.
You will next be parroting from a book that the Russian and French revolutions were genuine uprisings by the people of those two countries. It is quite obvious both revolutions were set ups by external powers and attempts to genocide the populations of those countries. Lenin was just an actor. Lol “rejoin the struggle” you are such a brainlet
I'm not sure, but things tend to get a bit messed up when articles get reposted multiple times and then the moderators (namely dang) merge the comment threads into one. So that might be the reason.
After watching the most recent smarter every day, I'm blown away with how complex the molecular machinery of even "simple life" like bacteria are. Proteins are just nuts - the ultimate building blocks for nano machines. Proton-powered rotating motors with gears for increasing torque... simply marvelous
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[ 1.1 ms ] story [ 121 ms ] thread[] https://en.wikipedia.org/wiki/Greenhouse_and_icehouse_Earth
Source: https://www.sciencedirect.com/science/article/pii/S167498711...
“while transforming enough energy” is both more accurate but also educates the lay reader by hinting at the processes involved.
So, very roughly, either life is hard to get started at all (but life started about as soon as possible on earth), intelligence is hard to evolve (although we see many species with intelligent behaviour, if not at human level), or it's in our future (that intelligent life tends to destroy itself).
[1] https://en.m.wikipedia.org/wiki/Great_Filter
Until we can reliably detect a species like ourselves on another planet, it seems very silly to assume they aren't there.
The assumptions on detection all kind of assume that aliens that are much more advanced will have much more obvious signals of emery usage or other detectable signals, but I've never been convinced by these assumptions. Energy usage is likely a logistic curve rather than an ever expanding exponential. There so much room at the bottom for greater efficiency. It also seems quite sensible that a species either eventually copes with equilibrium or dies out due to issues with unchecked growth.
There's SO MUCH energy available here on the earth that we could go for millenia of computational/energy growth while pursuing more efficient systems. The assumptions that lead to conclusions about megastructures are pretty dubious. I could go on at length about that, but I will just leave it at that.
As our species has developed, the time scales that matter to us have shrunk, not grown. I just don't think you can have a single coherent civilization work when relativity places such stringent limitations on communication speed. A super advanced civilization likely evolves and changes on much smaller time scales than ours does currently. It doesn't seem possible for such a civilization to not totally fracture at interstellar scales.
Unless there's physics we don't know about, interstellar distances are probably just not really compatible with a civilization. So, if one exists, its probably a serious rarity within a rarity. i.e. the lack of observable existence of such a noticeable civilization does not make a good argument against aliens in my opinion.
(This also raises for me a fun way to continue Moore's law by making lived experience slower...)
I don’t think this seems right. More realistically, the further back into the past we look, the more we notice people, institutions, and changes operating on longer time scales, partly because our knowledge becomes much less granular the further back we look and partly because slower changes are less noticeable or impressive when examined from partway through without the benefit of hindsight.
Unless you just mean that with improved technology we can now do a better job inspecting and sequencing things that happen very quickly. That’s clearly true, but is substantially unrelated to human-scale goals or the behaviors of larger organizations.
Mathematicians always seem to assume that reality is as simple as a plot on graph paper, but if that were the case we would have had hotels on Mars by now.
Or, quite reasonably, human-like intelligence is special and galactic-scale rare. Do we think every other kind of unlikely life exists elsewhere in the galaxy? If there are definitely other human-like intelligent life forms in the galaxy, then there are even more definitely flying pigs with nineteen legs and wheels on the ends. Does it feel so intuitively correct, considering that? The argument here is "but orangutans ... and crows and parrots ... and dolphins ... and octopuses ... and elephants ... they all abound with the potential to build rockets and electronics and self-replicating space probes. Any million years now, any one of those species could flip into producing lots of ideas and constructions and exploring everywhere." But, really? Sure, they do stuff with sticks and half-coconuts, but is "the parrot/octopus/elephant space program is just around the corner" really a parsimonious extrapolation from observed animal stick-handling?
Besides, nerve cells only evolved once, maybe that was a freakish event. Maybe every other animal in the galaxy is a sponge.
Imagine what we will be able to do with another 1000, or 10000 years of development. Can't see any fundamental reason why we could not ultimately build infrastructure and print up some lifeforms at their destinations.
[1] https://en.m.wikipedia.org/wiki/Breakthrough_Starshot
You need to move 500K hiroshimas a second for 80 kg (175 pounds). You'd also need some pretty fast brakes lest you run into some pretty small things. You also have a really bad recursive problem, at 100% E=MC^2 efficiency, you need to turn 100 kg of mass to pure energy, per second, to move 80 kg. So actually you need to move 180 kg, which requires...etc. etc.
This is the base of this thread, the Fermi Paradox: if it was a relatively quick scaling away, where is everybody? It's "turtles all the way down" to respond that there is no paradox, just imagine us in 10K years, even if we knew for 100% certainty we'll be there in 10K years.
Note the wikipedia article you linked uses "concept" 10 times, the roadshadow was in 2016, and has no updates after November 2017, 6.75 years ago.
There are orders of magnitude of things we can achieve as a species with current technology if we all work together efficiently but we don’t .
We ascribe to aliens a singular purpose that we have never achieved in our history as a species.
Our competitive, acrimonious past is fundamental to our scientific progress (we research more during war than peace) . A peaceful civilization may not reach technologically maturity.
It could also be just that Interstellar travel is not simply be economically viable in time frames that those civilizations optimize for. Ours can barely look beyond a quarter, why do we think any other civilization would plan for hundreds if not thousands of years .
Anyway, the Fermi paradox isn't about finding life on other planets.
The hard step was not complexification of life. It was long-term atmospheric oxygenation. It took two attempts, the first one short-lived, and between 3-4 billion years to finally succeed for good.
But yeah, oxygenation is a good candidate. Anyway we don't have that much of certainty about how it happened exactly.
But there are other possible explanations.
About the Great Filter, in principle we can expect the probability of those things to vary by several orders of magnitude, so only one would qualify. All of them being equally unlikely is actually harder to explain than the alternative.
We also now know that the creation of organic molecules is commonplace in the cosmos.
True, we don't get any predictive power from this. We're just exploring the space of possibilities, and there's still a lot of unknowns. I still see value in a thought framework like this to guide that exploration, but maybe there's a better approach?
[1] https://archive.ph/1yCVn
We don’t even know the paradox is real since we haven’t explored our own solar system enough to rule out aliens or artifacts of their visits in our back yard, nor can we rule out advanced observers intentionally not revealing themselves for any number of rational reasons. There could be an abandoned underground alien base on the Moon and we’d have no clue. We have barely gone anywhere.
If we hit, say, the level of development in The Expanse and still find nothing (no protomolecule haha) then maybe we can say there is definitely a paradox.
There’s also the assumption that there is a single discrete big and dramatic great filter. That’s the Hollywood version. In reality there could just be a continuous probability of failure due to any number of events whether endogenous or external spread across billions of years that amounts to a great filter. The probability per day of “biosphere failure” or some other condition that dooms a potential spacefaring intelligence doesn’t need to be high to amount to a probability near 1.0 over geological time scales.
Let’s say given we are sending our probes and capsules we are probably at least 50% of the way there. If the cumulative great filter were near 1.0 probability of failure this would imply a 50/50 probability of our success. Those are of course made up round numbers just to illustrate how that would work. We have no way to know what the actual numbers are because we have a sample size of one.
The whole thing is just speculation until we have more actual data.
As you say, we don't have enough data to know one way or another, but even when we do, there will still be no paradox.
My favorite hypothesis is that we are early. Due to low metallicity in the early universe it’s possible that advanced life only became likely “recently” (as in the last few billion years) and we are part of the first crop. We may be an early example in the first crop because our planet is particularly friendly to advanced stable life, so maybe a bit of rare Earth mixed in. Most other biospheres might be more hostile and take longer to produce anything capable of space flight.
We don’t see star travelers all over the place because for the most part it’s too soon. There might be a few early birds out there but few intelligences are that advanced yet.
This fact is buried in all the Fermi Paradox discussions because Fermi's point was the implications of his work on nuclear weapons when he brought up alien contact.
It has since been used to make the case for Reagan's Strategic Defense Initiative. Which apparently Elon Musk is now continuing... https://ioc.exchange/@muskfiles
It would need to be so powerful and so precisely aimed at us that firing randomly into the void would be pointless. We can barely detect the most energetic events in the universe like quasars and gamma ray bursts as it is.
And that assumes we could even decode it -- advanced coding uses scrambling techniques that deliberately make the signal look like noise to the uninformed receiver...
https://www.reddit.com/r/ChatGPT/comments/1dgyujd/comment/l8...
Creating a self-sustained ship is not so easy. And there are tons of failures that can happen, especially over the course of multiple generations. And you won't be able to just "beam down" to some random planet once your interflux quantum capacitor and its two backups fail. Unlikely things happen given enough time.
And why would you want to do this in the first place? Would life on such a ship really be all that great? Sounds like the stuff of a depressing dystopian sci-fi novel more than anything else.
Dyson spheres seem completely impractical. Just the sheer amount of materials needed alone, never mind the construction effort and maintenance effort. Dyson himself didn't take it very seriously, and I have no idea why anyone else does either.
As for Dyson spheres, don't take the remark so literally. I simply meant that a galaxy-spanning slime mould would probably be visible to our physics, somehow. Life is an entropy engine. Once it gets going, it really gets going. But we appear to live in an improbable oasis in a vast desert.
> As for Dyson spheres, don't take the remark so literally.
Of course it should be taken literally, because all of this is all about what the laws of nature do and don't allow and the practicalities surrounding that. This isn't an class or discussion about what does and doesn't make a good sci-fi story. And what is a "galaxy-spanning slime mould" even?
> Life on a ship is depressing? You may as well argue that life in hydrothermal vents would be boring.
Yes, it would be. There is no intelligent life living near thermal vents. What an odd thing to say.
Is this perhaps a specific personal grudge against your hometown or a more general dislike of Icelanders?
https://en.wikipedia.org/wiki/Hjalteyri
https://xray-mag.com/content/strytan-diving-icelands-hydroth...
Maybe they reached space but upon finding it inhospitable, decided it’s not worth the trouble. Doing things because they are hard could be a uniquely human trait.
On the other hand, I’ve seen a UAP with amazing abilities. Maybe they are here already but aren’t in a hurry to say hello. Maybe they think we are too primitive to warrant communication.
Maybe their signals are all around us but we don’t have the means to detect or interpret them.
Maybe they only use lasers and fiber optics to communicate.
What I take issue with is the notion that it should be surprising that we haven’t detected them. There are so many reasons why they could be right in plain sight, not even trying to hide themselves, while still going undetected. Those explanations are under appreciated in my opinion.
And it's dark so you cannot see it coming. You'd need very high frequency radar or more likely lidar to detect it and you wouldn't have much time to dodge it. (Not to mention that you have to design that lidar with relativistic effects in mind.)
The density of this stuff is not high but it's not zero either.
I think it would be more correct to say "It's now believed that complex life forms existed 1.5B years earlier than believed earlier"