The Great Filter is the idea that, in the development of life from the earliest stages of abiogenesis to reaching the highest levels of development on the Kardashev scale, there is a barrier to development that makes detectable extraterrestrial life exceedingly rare. The Great Filter is one possible resolution of the Fermi paradox.
https://en.wikipedia.org/wiki/Great_Filter
The Fermi paradox is the discrepancy between the lack of conclusive evidence of advanced extraterrestrial life and the apparently high likelihood of its existence. As a 2015 article put it, “If life is so easy, someone from somewhere must have come calling by now.”
https://en.wikipedia.org/wiki/Fermi_paradox
Personally I think it’s photosynthesis. Life itself developed and spread but photosynthesis started an inevitable chain of ever-greater and more-efficient life. I think a random chain of mutations that turns carbon-based proto-life into something that can harvest light energy is wildly unlikely, even after the wildly unlikely event of life beginning in the first place.
I have no data to back that up, just a guess.
I think that the great filter/fermi paradox is a combination of two facts,
- Our entire radio output (the only example we have to go by) is pitiful compared to the sun, like a candle in front of a flood light, you’ll only be able to see it so far before it’s completely drowned out. After a few dozen light years our radio output is less than the margin of error of a stars detectable radio output.
- As a civilization advances it must reduce radio leakage. As data gets more important, it gets more important that you’re not wasting energy moving it around. Narrow beamed radio transmission becomes the norm and even less radio signals escape the system than when radio was messy and overpowered.
They’re not missing or gone, they’ve just moved beyond messy radio signals. Even we tightened up our radio emissions in a little over a century. Most of what we watch or listen to comes to us via fiber, cable, or short range transmissions like cell phone towers and Wi-Fi.
Accidentally replied instead of editing to fix a mistake. Disregard comment.
An alternative is we are among the first. Third generation stars are the ones that have planets with enough heavy elements to allow for complex chemistry. Sol (our star) is thought to be among the first batch of third generation stars in our gallexy.
Light speed does seem to be the upper speed limit for the universe. Talking that into account we probably haven’t had a chance to see other early life as it would likely be spread pretty thin right now.
Yeah, I have a gut feeling that a lot of the variables in the Fermi equation are a little too generous.
I do agree that in the grand scale of things we’re actually very early. That alone would explain a lot.
I don’t think there is a single filter. My personal gut feeling however is that the jump to “specialised generalists” would be a major hurdle.
Early human civilizations are very prone to collapsing. A few bad years of rain, or an unexpected change of temperature would effectively destroy them. Making the jump from nomadic tribal to a civilisation capable of supporting the specialists needed for technology is apparently extremely fragile.
Earth also has an interesting curiosity. Our moon is extremely large, compared to earth. It also acts as a gyroscopic stabiliser. This keeps the earth from wobbling on its axis. Such a wobble would be devastating for a civilisation making the jump to technological. Even on earth, we are in a period of abnormal stability.
I suspect a good number of civilizations bottleneck at this jump. They might be capable of making the shift, but get knocked back down each time it starts to happen.
Speaking of our moon, the fact that it’s roughly the same size as the sun as seen from earth and the fact that this is a complete coincidence blows my mind. Like there’s no reason for that to be the case. Total eclipses like ours (where you can see the corona) are very rare.
Even more so, the moon is slowly moving away from the earth. A couple of million years ago, it would have completely covered the sun. In a couple of million years, it will not fully cover the disc.
A million years is a long time for humanity, but a blink on the timescale of moons and stars. We didn’t just luck out with the moon’s large size, but also with the timing of our evolution.
That’s nuts. In two million years, humans will be sighing and saying wistfully “if I had a time machine, I’d want to go back to the time of the full eclipses, like 2024”
We’re currently in it. Failing to create a clean, renewable, and scalable energy source powerful enough to run a society that is ever increasing in both population and technology without destroying their only inhabited planet has got to be the most common great filter.
Asteroids strikes, super volcanoes, solar CMEs, and other planetary or cosmetic phenomena that exactly line up in both severity and timing are too rare IMO.
Every society that attempts to progress from Type 1 to Type 2 has to deal with energy production. Most will fail and they will either regress/stagnate or destroy themselves. Very few will successfully solve the energy problem before it is too late.
A filter for sure, but not a great one. Call me optimistic, but I don’t think that will set us back more than 10.000 years. If humanity can survive, society will re-emerge, and we are back here 2-3000 years into the future.
Is +5°C Earth a good place to be? No. Will the majority of humans die? Absolutely. Will the descendants get to try this society thing again? I believe so.
On a cosmic scale 10.000 years is just a setback, and cannot be considered a great filter.
Unfortunately we’ve pretty much used up all easily available resources. Anyone ‘starting over’ would have a much harder time getting the things they need to really get the ball rolling again.
When humans first discovered gold they practically only had to scoop it out of rivers. You’ll be hard pressed to find any streams with such appreciable production anywhere in the world today.
We’ve already discovered fission and photocells. We’re past the point of needing fossil fuels for a new civilization (or existing civilization). Fossil fuels are only hanging around for economic reasons.
I think that is thinking a bit too narrow. A lot of the stuff we use today might just be our bronze to our successors iron - you can build an unstable society on either. And what we do use up today could still work if used more efficiently - we might not have enough rare metals to give everyone a smartphone in the post-post-apocalypse, but I could see us still launching satellites if only big governments had computers - because they did.
Everyone is talking about society or physiology stuff. That is just things that might get humans.
Stars going super-nova is the real great filter. Our sun is 4.6 billion years old. Life started 4 billion years ago. In 4 billion years, the sun goes supernova. We are halfway to the end of the earth.
Smaller stars last longer, but have smaller ranges that life can exist in - and planets tend to move in or out in their orbits. Bigger stars have giant habitable zones - but some large stars born when humans took their first steps are in their last decades of life. You couldn’t get from the pyramids to NASA in that time, never mind the 4 billion years it took to get to humans.
I think it’s supposed to actually less than that, the sun’s luminescence will increase over the next 1 billion years to the point that it will boil off the earth’s oceans. No life will be able to exist past that, and earth will just be a barren rock in orbit for the next 3 billion years.
While that is true I would counter point that humans have a bit of a handicap as earth got hit by a big astroid that killed just about everything on it making terran life have to start all over again but at the other hand I saw someone else on here mentioned that oil has given us a head start at space ferrang advancement and oil is made from dead life so granted I haven’t done much reacerch on how oil forms naturally but I do wonder if we would have oil if earth never got blown up but on top of all that there are theorys that mars used to have life so if astroids haven’t interfered with our solar system intelligent life may have formed faster and maybe twice also there used to be multiple species of humans in the past so maybe 4 or five times in the same solar system
For a technological civilization like ours, I think it’s just that Earth/humans are weird and we’re past the main ones (like going from single-cell to multi-cellular organisms).
Having to overcome the physical obstacles on other planets rules out the type of spacefaring technological civilizations like ours. No matter how intelligent a civilization on a water world is, it’s not starting fires, much less building rockets. Just getting out of the water would be their space program. Even a totally Earth-like planet that’s a bit bigger and has an intelligent species wouldn’t be able to get to space with chemical rockets.
And also, humans are weird. It could be as basic as “we have hands for building complex tools.” We have a seemingly insatiable need to compete and explore, even beyond all logic—maybe no other intelligent species wants to strap someone to a rocket and send them to space because it sucks up there. We’re violent: without WWII and the Cold War, do we even have a space program?
So many things had to come together to create an intelligent, tool-building species with hands that lives on a planet with the right balance of land and water. As far as we know, it never even happened on Earth before and even then, we had thousands of years of civilizations before anyone was dumb enough to strap themselves to a rocket just to see what would happen.
I definitely subscribe to the “humans are insane” theory of galactic lifeforms
My thought is the evolution of intelligent life itself. If you think about it, intelligence is contrary to most of the principles of evolution. You spend a shit ton of energy to think, and you don’t really get much back for that investment until you start building a civilization.
As far as we can tell, sufficient intelligence to build technological civilizations has only evolved once in the entire history of the Earth, and even then humans almost went extinct
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space
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We’ve been producing noticeable radio waves for a matter of decades. We’ve been capable of detecting even super-powerful, super-deliberate, super-targeted broadcasts for even less time.
And on top of that, it doesn’t look as though our civilisation is going to exist for more than a handful more decades, in any detectable-from-light-years-away form.
The chances of that onionskin-thin slice of lightcone intersecting with that of any other civilisation out there seems ludicrously remote.
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We have had Millions of years of (presumably) intelligent Dinosaurs on this planet, but only 200.000 years of mankind were enough to create Civilization IV, the best Strategy game and peak of life as we know it.
So clearly, Civilization™ is what sets us apart.
Jokes aside, the thing evolution on earth spend the most time on is getting from single celled life-forms to multicellular life (~2 billion years). If what earth life found difficult is difficult for all, multicellular collaboration is way harder than photosynthesis, which evolved roughly half a billion years after life formed.
The most boring one: most species off themselves before they fully get off their starting planet. We will go the same way. Take your pick from climate change, war, pandemic, … or even a combination of several!
I agree. The threshold for becoming the “dominant species” of a planet is so low that the species still has its primal wiring for tribalism, competitiveness, etc. by the time it can build rockets. We humans should’ve had more time in the evolutionary oven to become more empathetic and cooperative for longer-term survival. Instead we have people willing (and able) to literally burn the world down to become richer or more powerful. And we have most of society cheering them on.
We’ve been on the verge of destroying ourselves for decades now, and humans have just barely started doing space stuff (a blink compared to the life of the universe). How in the world can anyone expect us to get to Dyson sphere levels of progress with how fragile our existence is?
I disagree with your last point. I think we’ll be at Dyson sphere levels in a thousand years, easily. Maybe two thousand if we an hero ourselves.
I read an article about Fermi paradox (I cannot find the link) that stated the humans are one of the first intelligent beings in the universe. That’s why we haven’t encountered any green men so far. We just might came too soon to the party.
Definitely possible. I’ve read that the projected end of our sun is a “black dwarf”, and that our sun’s generation of stars is so young that there currently aren’t any known black dwarf stars anywhere in the universe.
I don’t think there is a great filter. I think there’s an easy solution to the fermi paradox that doesn’t require great filters, we’re just the first intelligence in this galaxy.
Here’s my reasoning: intelligent species that manage to develop space travel probably do tend to expand out into their galaxy. When they achieve this level of technology they can settle most of all of their galaxy in a matter of 10,000 years or so. That time period is very brief on an evolutionary scale. It’s estimated that life began on earth 3.7 billion years ago. That means it took about 3.7 billion years for earth to produce intelligent life, and then from that point it would take a mere 10,000 years to reach modern day, and 10,000 more years to settle the whole galaxy. That expansion happens so quickly compared to how long it took the planet to develop intelligent life, that the chance of two civilizations rising at the same time becomes very small.
It all boils down to this: there are no intelligent aliens out there in our galaxy, because we are the first intelligent species in our galaxy. We know we’re the first because if we were second, then aliens would already have settled this star system.
Probably there are lots of alien civilizations out there in the universe, but they’re in different galaxies.
That assumes that interstellar travel is possible. Physically, economically, socially, there’s a lot of boxes to check for near-light extrasolar expansion (let alone FTL, which probably is impossible)
I think the easy solution to the Fermi Paradox is that we’re stuck in our fish bowl and so is everyone else.
That’s true, it does assume interstellar travel is physically possible, but at this point there are forms of interstellar travel that we know are possible.
Solar sails for instance, we know those work, we’ve tried it. Now if you wanted to travel to another star system with a solar sail, it’s just a matter of scaling that proven technology way up. We’re not ready to do that today, and we won’t be ready in the next 20 years, but to think that we wouldn’t be ready in 500 years, I find that idea far fetched.
But a much better technology would be fusion propulsion. With fusion drives you could get your cruising speed up to a meaningful fraction of the speed of light (perhaps 5-10%). At that rate you can make it to the closest stars in less than 100 years. And that technology is not at all far fetched. We truly are approaching working fusion power plants, it’s extremely likely that we can eventually develop fusion propulsion, or at the very least, fusion powered electrical propulsion (ion drive).
As for if it will ever be economically possible, I’m not at all worried about that. The fact is, there are a lot of resources and opportunities right here in our solar system, just waiting for people to utilize them. So people definitely will start mining and manufacturing in space eventually. And as we start to operate more in space, we will naturally continue to iterate and improve our methods of getting around. In short, over time it’s going to get cheaper and cheaper to make space ships and we’re going to get better and better at doing it. The economic factors are likely to fall into place eventually.
And finally, will interstellar travel ever be possible socially? Hey, your guess is as good as mine. I don’t think we have any way to answer that…
But why are we the first. That’s the question. Given the age of the universe, statistically it should have already happened by now. Unless something was stopping it.
Statistically I shouldn’t fail a 99% roll 7 times during a single mission in XCOM and yet here we are.
“weird coincidence” is one potential solution to the Fermi paradox.
It could simply be that the rise of life is wildly more rare than we think.
Yeah, it totally could be.
That’s definitely the right question! And honestly we don’t know, but it’s evident that we are first.
Given the age of the universe, statistically it should have already happened by now.
I’m not sure that’s true… I’m pretty sure that our sun is old for a main sequence yellow star in our galaxy. When you compare how long it takes for a star to get to the point ours is now, compared to the age of our galaxy, I believe it suggests that sol is part of a first wave of stars of its type. So if life really requires a star like this one to start up, then intelligent life starting just now could be right on time.
Now why is our start perfect for life? Again, we don’t know, but evidently it is. Sadly we only have this one data point, this is the only star where we know there’s life. So assuming that something about our type of star is perfect is about as sensible as assuming that life could start around any star. Is it that other kinds of stars produce too much radiation in the Goldilocks zone? Or is it that other kinds of stars are too variable in the amount of heat they produce? Or that other kinds of stars don’t tend to have rocky planets? We don’t know, but something about main sequence yellow stars could be special, and we have one of the first of those stars in this galaxy.
So declaring “we’re the first” requires some assumptions, but they aren’t crazy assumptions, and a lack of evidence of other older civilizations makes those assumptions stronger.
And to your point, the universe is much older than this our star, so I suspect intelligent life has developed many times before us, at least in older galaxies. But sadly I don’t expect us to ever meet life from another galaxy. While I think stars within a galaxy are close enough for travel between them, galaxies are very, very far apart. I don’t think life has much chance of traveling to other galaxies, at least not without some method of ftl travel (which I am also not optimistic about).
In my sci Fi that I’ve been working on has this theory being true but I also play with asking what is the point of colonization. In my story humans have colonized mars to study the fossils and what life used to be like on Mars. However the people there after a few generations separate from earth. Earth doesn’t do anything about it because not only can mars use telescopes to see our ipbm years before it arrives and have that time to shoot our ipbm before it arrives but invasion will destroy the fossils we care about. And that’s all assuming history won’t just repeat itself. Eventually the mars colony expands until it breaks into different nations all fighting echother to become the first martin superpower. So everything that earth cares about gets destroyed by war anyway and earth is pointless to mars without life and water. Eventually the sun becomes so old that everyone feels the need to move their populations to another solar system. And only then de humans discover alien life. Only to discover that it’s currently 900 billion years beyond 2024 and aliens are just now figuring out radio waves and rockets and are more concerned about developing eugenics than discovering humans.
Honorable mention: we haven’t detected alien probes, because intelligent alien societies haven’t begun consuming the galaxy with exponential numbers of self-replicating robotic probes, because that’s just a really bad idea:
Simple workarounds exist to avoid the over-replication scenario. Radio transmitters, or other means of wireless communication, could be used by probes programmed not to replicate beyond a certain density (such as five probes per cubic parsec) or arbitrary limit (such as ten million within one century), analogous to the Hayflick limit in cell reproduction. One problem with this defence against uncontrolled replication is that it would only require a single probe to malfunction and begin unrestricted reproduction for the entire approach to fail – essentially a technological cancer – unless each probe also has the ability to detect such malfunction in its neighbours and implements a seek and destroy protocol (which in turn could lead to probe-on-probe space wars if faulty probes first managed to multiply to high numbers before they were found by sound ones, which could then well have programming to replicate to matching numbers so as to manage the infestation).
I think we’re the first. Or rather in the first wave of intelligent life. It could take a thousand years just for a message to reach us. On the theory that life has evolved to this point as fast as possible over the life of our Galaxy, there’s no filter. There just hasn’t been enough time for contact to occur.
I personally find the kardashev scale a pretty terrible way to measure the success of a civilization. Maybe the most successful life forms don’t become technologically obsessed materialists determined to colonize everything habitable and drain the resources of everything else, yknow?
I mean then how did they become a life form
I wasn’t clear enough I don’t think when I wrote that. I meant that as in the most successful intelligent life forms don’t separate themselves from their ecosystems nor disrupt it in the way we do.
