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Researchers Say The Aliens Are Silent Because They Are Extinct (theconversation.com)
HughPickens.com writes: The Conversation reports that according to research by Dr. Charles Lineweaver and Dr. Aditya Chopra, a plausible solution to Fermi's paradox is near universal early extinction of life on exoplanets, which they have named the Gaian Bottleneck. "The universe is probably filled with habitable planets, so many scientists think it should be teeming with aliens," says Chopra. "The mystery of why we haven't yet found signs of aliens may have less to do with the likelihood of the origin of life or intelligence and have more to do with the rarity of the rapid emergence of biological regulation of feedback cycles on planetary surfaces." According to the researchers, most early planetary environments are unstable. To produce a habitable planet, life forms need to regulate greenhouse gases such as water and carbon dioxide to keep surface temperatures stable. About four billion years ago, Earth, Venus and Mars may have all been habitable. However, a billion years or so after formation, Venus turned into a hothouse and Mars froze into an icebox. Even if wet rocky Earth-like planets are in the "Goldilocks Zone" of their host stars, it seems that runaway freezing or heating may be their default fate. Large impactors and huge variation in the amounts of water and greenhouse gases can also induce positive feedback cycles that push planets away from habitable conditions. The difference on Earth may be that as soon as life became widespread on our planet, the earliest metabolisms began to modulate the greenhouse gas composition of the atmosphere. "The emergence of life's ability to regulate initially non-biological feedback mechanisms could be the most significant factor responsible for life's persistence on Earth, conclude Lineweaver and Chopra. "Even if life does emerge on a planet, it rarely evolves quickly enough to regulate greenhouse gases, and thereby keep surface temperatures compatible with liquid water and habitability."
A good theory I read about somewhere is that the reason we can not find evidence is simply to do with technology either other alien cultures at the point in time we are witnessing there systems have not developed the technology that we can detect or they have moved beyond the need to blast everything in the entire em spectrum out to space.
How many years have we been detectable by other races and how many years left until our technology gets efficient enough that any trace of our race gets hidden by been simply cleaner with our em pollution.
Will we cease to exist to other races out there when we become undetectable?
They can be built around any reasonably stable star (especially very long-lived red dwarfs) which has some rubble to rebuild into spacious habitations. No need to seek a proper star or habitable/terraformable planet. No need to genetically warp ourselves or live in underground tunnels like morlocks. The Colonies provide the perfect living conditions for the builder species.
Communication networks are likely via line-of-sight laser or some means we can't comprehend, so there's no transmissions for us to pick up. Hundreds of millions in number around each star, they're still too wispy to show up at distance as much more than asteroid fields or protoplanet belts. Being self-sufficient, it's no big deal when one colony decides to make the long, slow journey to the next uninhabited star. There, they get busy populating the colonies pre-built by robots sent ahead. The universe is old enough that there has been time for every star in the galaxy to be homesteaded by now.
We can get started by dismantling our own moon for material, moving on to Mercury and Mars's moons (planets are too big and unhealthy for our biology) until all of the available floating rock has been utilized. The colonies aren't made of girders and sheet steel. They're built by sintering crushed rock in the beam of focused sunlight, building up the superstructure like a gargantuan 3D printer. To simplify energy collection, the second or third generation of colonies are probably towed close to the sun, to minimize the size of PV panels needed.
I think there are two other points to consider: First, life and even intelligent life does not necessarily mean technology, or technology at an industrial scale. Maybe just THIS is very, very rare, with civilisations going this way separated by enormous gulfs of time and space. And maybe the universe is full of planets with aliens that have some sophisticated culture, but not at an technological scale that would lead to us being able to detect them.
Then there's the bottleneck of how long a species can sustain a lifestyle of full-scale industrial technology. Without forking out into space as soon as they can resources will be depleted very soon and then it's too late. Either that culture will end then or will (have to) become much more efficient and low-key, which again lowers the chances of us detecting anything.
I mean, one very useful aspect of thinking about this is thinking about what is going on here, not there. How long can we sustain this and what do we have to do to sustain it? Maybe we will learn how things tend to go with industrial-scale technological civilisations very quickly, even if too late...
Or National Enquirer ?
Global Warming (TM) killed the aliens!
Except that it ignores subsurface oceans, which seem to be quite stable over long timeperiods and quite likely to be very abundant in the universe.
Sure, a species evolved to an undersea environment faces challenges in getting to their surface and beyond... but if we can get out of this deep gravity well after such a (geologically) short period of time after our species' evolution, sentient species in subsurface oceans with hundreds of millions or billion years on their "hands" would surely deal with the technical difficulties.
And of course there's also the possibility of LNAWKI, but let's just stick with LAWKI for now.
My personal suspicion is that a wide variety of factors work together to keep complex life rather rare on a per-planet basis, great distances dilute any signals from any that do achieve sentience, and the speed of light and difficulty of propagating a civilization outward at near that limit keeps the vast majority far away. Basically, rarity + dilution. But that's just my suspicion.
Maybe, but I can barely make out what you're saying because your horse is too high.
My personal theory is that the most likely thing for any intelligent and technologically capable alien race to be doing is exactly what *we* are doing. Listen, and with a small budget - so only listening to a very small part of the spectrum from a tiny part of the sky. That golden record on voyager 1 is about the last major attempt we made at sending anything and it wasn't a very sensible one.
But if that was what economics led to here, why would we assume it would have other outcomes elsewhere ? Literally the only experimental sample of a technologically capable space-faring race we have - did this one.
So it's perfectly likely that there dozens of alien races within easy communications range of us all making a half-hearted attempt at listening and waiting for one of the others to talk first. All of them, in fact, hoping the outsource the expense of sending high-powered signals into a void where you don't know if anybody is listening, don't know if anybody who was listening would be able to understand it and don't even know in which direction to aim - to one of the others.
Exactly because sending messages is so incredibly difficult technically, and expensive, they may all have opted to just listen instead and, like us, hope that one of the others will figure out transmission first so they can justify the budget to build a transmitter to reply with.
Unicode killed the ASCII-art *
>To get a technological head start and a head start out in space an alien species would been part of an evolutionary process that skipped whatever their equivalent of dinosaurs would have been and gone directly to intelligent life capable of technology.
Firstly - why not ? We have no proof that there were NOT technologically advanced dinosaurs, at best we have strong reason to doubt there were spacefaring dinosaurs. You are underestimating just how massive an amount of deep time 65-million years was. Dinosaurs could have built cities five times bigger than New York and not a shred would have survived for us to find. If we go extinct tomorrow, it's unlikely that in 10-million years there will be any evidence whatsoever that we existed - except maybe a few primate fossils, even our best mummies can't make it that far. A hundred million ? Not a chance, by that point even our satelites would have decayed and crashed. The last evidence of our existence that may be around would be the bits of junk Apollo left on the moon and any future paleontologists (whether evolved here or elsewhere) that found that evidence would mostly wonder what the hell a Richard M. Nixon was... think about it, they would not even be sure whether it was left there by an earth-born species that reached the moon - or a long-lost lunar species that had a great council to end a war at that spot.
Secondly - your argument is flawed because that's not how time works, time is relative and doesn't happen at a constant rate. Planets that rotate their stars slower have physically existed longer than ones that move slower. So two planets around the same star, in different orbits, which orbit in the same timeframe, that formed together at the same time - the outer one will be significantly younger because time slows down as you speed up. It may be a matter of seconds per rotation - but there's been many billions of rotations for those to add up. And planets around more massive stars are regardless of when they formed relative to the big-bang, have had less time pass on them than those around smaller stars - because time slows down near bigger gravity wells.
The amount of "time" that passed on the surface of a planet is only very vaguely connected to the age of the universe and even to the age of that planet (which we measure relative to the age of the universe). The one decidedly does not offer any indications of the other. The only reason they happen to be the same on earth is because we happen to measure "years" by the time it takes our planet to rotate, but Jupiter formed at the same time as Earth did - and quite a lot less time has passed on Jupiter than on Earth. Even less have passed on the sun.
This is, actually, one reason why - if there is life on Io or Europa - that life is likely to be "bacterial" rather than fishes - those moons circle a massive planet, any life there has had significantly less time to evolve than life on earth has had. No, I don't feel like doing the math to figure out how much.
Unicode killed the ASCII-art *
I think you're missing the point.
An alien civilisation with a mere few hundred years head start on humanity would probably have technology that was nearly magical to us if we were to meet them today.
Stretch that out to a few tens of thousands of years - still utterly irrelevant on a timescale measured in billions of years - and you've easily got the kind of civilisation the OP was talking about. Undetectable by us and completely uninterested in us.
From memory, even with the technology we have today we could colonise the entire galaxy in a million years. Not that I think any civilisation could remain stable for that long, but consider it in the context of the mere hundreds or thousands of years "head start" required as discussed earlier.
Even if we're not, look at our development. Even if another civilization was on par with us, they could not even communicate with us if they wanted.
Whenever the topic gets to alien life forms, everyone assumes that the aliens must be advanced compared to us and have mastered interstellar, maybe even intergalactic, travel. Says who? Who says it's even possible to do this akin to various SciFi movies? What if the aliens would have to use newtonian physics to get here? Even if they developed 20 LJ away their journey would take centuries.
Our development from "duh, me make fire" to "duh, remote control is broken, need new TV" took about 10,000 years. And we're still in no position whatsoever to fly to any other star than our own. Hell, even reaching the next planet is something we've been working on for half a century now. And every time we actually manage to get a non-manned robot there on a one way trip we celebrate it hugely. What makes us think that anyone else in this universe is actually so far ahead of us to be able to fly about between the stars AND have the hubris to assume that someone this advanced would actually want to have anything to do with us?
We used to have a Bill of Rights. Now, with the rights gone, all we have left is the bill.
even with the technology we have today we could colonise the entire galaxy in a million years
No we could not. The milkyway has a diameter of about 100,000 light years, give or take.
To fly every where you would need at least 0.1c and may not be to far at the edge, which unfortunately is the case for the solar system.
With our technology we have no means to accelerate and decelerate a space ship with life on it to 0.1c.
You probably could "seed" the whole galaxy in 10 - 100 million years, but not in 1 million.
And bottom line: why would anyone really want to do that? Except for the curiousity like "wow lets dive as deep as we can and look what is there" there never will be a big appeal to space for most of the humans.
Would i like to go out visit the next star system? Yes, absolutely.
Would I like to go out to the next star system on a journey that will take so long that I definitely die on the way before we reach the destination? Absolutely not. There are much more fun activities I can do here on earth than on a what ever luxuries it might have, space ship.
Cost free eBook I read (by iBook/Kobo/Amazon/ObookO/Gutenberg etc.): "The Green Odyssey" by Philip Jose Farmer.
For four billion years, life on Earth was microscopic blobs of goo.
Then 600 million years ago - BAM - complex life emerged pretty much in the blink of an eye.
We have no idea how likely that transition to complex life 600 million years ago was - we have a sample size of ONE.
Now go back an read my first sentence: For four billion years, life on Earth was microscopic blobs of goo.
That four billion years was about half the expected lifetime of the Earth. The probability that complex life evolves may very well be infinitesimally small. WE DON'T KNOW.
Believing the universe must be teeming with intelligence is based on nothing more than faith.
Actually, the odds are worse than that. Mass extinctions have happened with monotonous regularity in the history of the world, and only comparatively recently have life forms evolved with internal skeletons that enabled them to get to be quite big. Insects and arthropods probably don't get big enough to carry large enough brains to become intelligent, but arthropods seem to evolve a lot more easily than do vertebrates.
Even when you look at vertebrates, a tendency to evolve big brains seems to be exclusively a mammal thing. Dinosaurs seem to have been ancestrally warm-blooded, ditto crocodilians and so on, but dinosaurs plot right on the expected brain to body size ratio that reptiles have. Throughout the entire age of dinosaurs there never seems to have been any sort of intelligence arms-race developed. Early in the post-dinosaur age, just such an arms race developed with mammals, forcing quite a lot to become smarter over quite a short period of time.
There's two reasons to doubt the inevitability of intelligence developing on alien worlds. There may well be plenty of life, but life more advanced than bacteria will be rare, and intelligent life vanishingly so.
On the other hand, some things can be easier underwater - for example, moving heavy objects (with buoyancy), long distance communication, etc. And of course the main drivers for advancement still exist, things like farming, hunting, armaments, defense, etc.
Electricity still works underwater (though AC not as well, and of course insulation is important). The same basic lines of progression work underwater. You can still make a "potato battery" type cell underwater with native copper, you can move lodestones next to a conductor, all of the usual stuff. Working metal underwater would be kind of an interesting challenge, of course - it would require better insulation and a good source of heat in a non-oxidizing atmosphere. But there are all sorts of oxidizers that can be made (or could exist naturally) other than O2, and other potential sources of heat beyond combustion.
Maybe, but I can barely make out what you're saying because your horse is too high.
> My personal theory is that the most likely thing for any intelligent and technologically capable alien race to be doing is exactly what *we* are doing.
Exactly - making ourselves go extinct over the cosmological blip of a few hundred years, by systematically undermining our own life conditions (us: global warming); by squandering non-replenishable resources (oil, gas, rare earth elements); by maintaining nation states that act like we don't share a planet (Putin's Russia, North Korea, China, Arab / Islam countries, USA etc.); by creating weapons that allow more and more destructive potential per user (nuclear, biological and autonomous weapons); and by resisting the completion of the surveillance police state and precrime, which are pretty much the only means to ensure that terrorists are killed before they can fake some nuclear attack, setting off WWIII, or release some plague that wipes out half of mankind and destroys economy as we know it.
Once we global-warm, war or terrorism ourselves back into a pre-technological tribe, we'll no longer have the chance for an industrial and thus technological revolution, for we have already used up most of the easily accessible oil and gas; no more radio telescopes sent to space.
Maybe we can't observe other intelligent life simply because chances are, any transmission is puny and fleeting on the cosmological scale, making reception incredibly unlikely. However maybe there are intelligent creatures that enjoyed their brief technological triumph, only to be followed by millions of years of an eternal Stone Age in the optimistic doom scenario when large bodied intelligent creatures can even survive their own technological windfall.
The rare few civilizations that survive the high mortality rate of technological infancy might evolve to such superpowers that they have unimaginable matter manipulation and computational capabilities in their hand. We, at such premature stage, already build vast, large simulations even without really trying (called games or machine learning environments). They (and maybe we) then go on building new universes which themselves beget alife, some of which may become powerful to build their own simulations. Then, we can conclude that believing that we are World #1 is the same anthropocentric view and hubris as geocentrism was a moment ago. Most probably we're currently on the bottom of a deep stack, hoping for adequate power redundancy and backup procedures in all layers above.
In conclusion, most of the fellow technological civilizations are behind us or ahead of us (time), or above us and maybe at some point, below us (simulation stack). All except the last of these are very unlikely to encounter and detect.