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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."
Yep, it's the distance.
And whatever constitutes "teeming with aliens". Is that 10 planets per galaxy? 100? 1,000?
And the time involved. How long ago did life start on Earth? How many mass extinctions have there been? Would ANY of those have been detected by aliens on their home planet using technology equivalent to ours?
The Fermi "paradox" is based upon alien expansion. Which is, in turn, based upon tech advances that we don't have.
The galaxy could be "teeming with aliens" that we cannot detect and that we cannot reach with our technology. Nor can they detect us or reach us.
'Sometimes I think the surest sign that intelligent life exists elsewhere in the universe is that none of it has tried to contact us.'
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.
Just some of the things that had to happen for us to be where we are now:
1) Life had to evolve
2) Multicelluar life had to evolve (this took a billion years after life itself arose so is probably not a forgone conclusion)
3) Life had to climb out of the oceans (dolphins might be smart but they won't be building any rockets with their flippers anytime soon)
4) Suitable intelligence had to evolve. Had it not been for the asteroid the dinosaurs would still be in charge.
5) Humans had to survive numerous climate changes and if the genetics is to be believed we almost died out and everyone today comes from a very small population who made it.
6) Farming had to be created to allow people to do something other than hunting and gathering.
7) For the industrial revolution plenty of freely available energy had to be lying around near the surface - ie coal. You can't melt iron with wood fires.
8) Someone had to invent radio.
I'm sure there are dozens of other things that could fit inbetween those points but my basic point is that a technological civilisation than can broadcast information out from his own planey is very VERY unlikely. IMO we could well be the only one surrounded by planets full of the equivalents of bacteria and jellyfish but little more.
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...
Monty Python
Maybe the aliens aren't quite dead yet . . . they are merely resting?
Tired and shagged out after a long squawk . . . ?
Or it's intern-planetary censorship . . . their governments are blocking them from contacting us . . . ?
Schroedinger's Brexit: The UK is both in and out of the EU at the same time!
We don't even have the Concorde anymore, or the SR-71, in some ways we've gone backwards.
The only way in which the Concorde and SR-71 were not primitive is that they were fast. But the mindset of burning up that much fuel so that Rod Stewart can get a haircut in another country and still wind up looking like an aged lesbian or so that we can spy on another country so that we can more effectively wage a cold war against them is seriously fucking backwards.
Getting rid of the Concorde and the SR-71 might seem technologically backwards, but in fact, it is a huge step in the correct direction. Do you seriously suggest that advanced aliens would be flying around at supersonic speeds for no good reason? How inefficient.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
Supersonic in interstellar/interplanetary terms would be like going cross country on a push bike
In space, no one can hear you trying to exceed the speed of sound.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
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.
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.
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 *
Or we're all living in a simulator and the 'alien' expansion pack hasn't been released....yet.
Life is not for the lazy.
All speculation about alien life tends to founder on the issue of small sample size, but already we observe that our machines 'like' space and extraterrestrial surface environments much better than our squishy carbon-based bodies do. So perhaps the leading candidate for LNAWKI would be something like our silicon-based emissaries. If the same process has been going on elsewhere we may find that (a) the most likely aliens we encounter will be machines, and (b) the encounter will be by our own machines.
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.
One thing to bear in mind is that life here existed in the form of anaerobic bacteria for a staggeringly long time. Photosynthesis began as a way to split hydrogen sulphide into useful hydrogen ions and a useless waste product of elemental sulphur, which was also usefully inert. Early photosynthesis therefore didn't require much in the way of biochemical sophistication to operate; the waste sulphur is where some large sulphur deposits originated.
That changed with a mutation which let the photosynthesis split not hydrogen sulphide, but water into useful hydrogen and (to anaerobic bacteria) highly toxic and dangerous oxygen. That initially wasn't all that big a problem to early water-splitters; the oceans they were in were rich in iron-II salts which readily absorbed oxygen to become insoluble iron-III salts (this is where the banded iron rock formations come from).
Everything changed when most of the iron-II in solution in the early earth's oceans was used up. Oxygen levels slowly rose, and virtually all bacterial species either adapted or went extinct. Oxygen is toxic to most bacteria.
I would hypothesise that most alien worlds either never make the switch from anaerobic atmosphere to aerobic one, or fail to establish a homeostatic oxygen-nitrogen atmosphere quickly enough and effectively enough to become self-regulating.
True but usually you can see some signs that there are neighbours there such as hearing their car or the music they are playing. In our case we have not heard anything so either we are not listening in the right way, they make practically no 'noise' or they don't exist at least close by.
When humans first invented radio, we broadcast strong simple signals because our technology was primitive. These signals would be detectable from very long distances away. But we are rapidly moving to much weaker and complex transmissions. This has the benefit of using far less power, and has much greater bandwidth. But it also makes the signal harder to detect and almost indistinguishable from background noise. There was only a 150 year window from when we started to transmit, and when our transmissions became indistinguishable from static. Compared to the age of the Universe, that window was a very tiny blip.
wild, speculation like this is a waste of time
Wasting time on wild speculation is the whole point of Slashdot.
Unfortunately, these geek acronyms tend to be English-specific. Some others you will encounter here:
RTKBA - Right to keep and bear arms;
TEOTWAWKI - The end of the world as we know it;
DYKWIA - "Do you know who I am?"
SJW - Social justice warrior
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.
All of the time spans you give here are inconsequential when compared to the age of the universe. Even if it took us 10 million years to go from current technology to quick interstellar travel, if life is not unique to Earth then we are either the first sapient species or the only one. 10 million years is simply not a long time at this scale.
Star systems started forming within a billion years of the big bang (source), over 13 billion years ago, and it took less than 5 billion years for life to reach its current state on Earth since its creation. That leaves over 8 billion years for potential sapient civilizations to emerge before us. One physist claims it would take 5 - 10 billion years to colonize the entire known galaxy even with current propulsion technology.
We may find out life is so rare we are either the only ones or among only a few dozen inhabited planets. But if life is common at all, it is very likely there are intergalactic civilizations which have been around for billions of years. That is what leads many people, myself included, to believe life is an extreme rarity.
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 have people on our planet devoting their careers to researching earth worms, so it doesn't take hubris to believe that out of potentially near infinite civilizations there may be some who have scientists interested in studying pre-interstellar civilizations like us.
-- All that is necessary for the triumph of evil is that good men do nothing. -- Edmund Burke
The elephant in the room is that cosmological distances are unbelievably large. The energy expenditure and sheer material cost of building something that can move any further than the outer reaches of a solar system is so huge as to make almost pointless even if possible. Currently it is blind faith rather than physics that suggests that the human race will ever be able to visit even the nearest star.
What is slightly more puzzling is that if the galaxy is teaming with technological civilizations we can detect no sign of their signals. Though this may just be the inadequacy of current technology. Discriminating against stars for any electromagnetic signal even for a focused laser is probably beyond our means at the moment. I have not seen any analysis of this from people like the SETI institute, has anyone seen this analysis?
Facts are history now plebs have politics for religion on social media.
> ND have the hubris to assume that someone this advanced would actually want to have anything to do with us?
Because it isn't hubris. Humans are interesting. Perhaps not to some rock-being, or whatever space opera alien is in your head that is Sooooooooo advanced that they find us boring, but to SOMETHING at SOME TIME. You posit a pretty strange concept: that if there's a zillion advanced lifeforms out there, that literally NONE of them would find Earth, or humanity, interesting in the slightest. That's the problem: it's trivial to imagine a species "so advanced" that we are very very boring to them. It's much harder to imagine that the universe is EXCLUSIVELY filled with these beings.