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 don’t think life is rare, nor photosynthesis, but complex life might be. A planet needs to be really thriving with life for it to be worth it to go down the path to something like animals
But I think the bigger filter is much stranger.
Humans are a hive-like species. We’re not just social - we’re insanely interdependent, we don’t function on our own and yet we’ve ended up in this place where we (often) try to individually succeed, even at the cost to our community
We’re greedy enough to want the stars, yet interdependent enough we could only swarm over them in endless numbers
There’s many problems with the fermi “paradox”, but personally I think one of the largest is assuming all species would spread like a cancer blotting out the stars
A more individualistic and long lived species might instead be careful explorers, taking what they need and leaving little sign of their passage. A more communal species might be careful and control themselves to not destroy pointlessly. They might also feel no desire to contact other species
We’re just the right mix to want everything a star could give, and to want to find others at great energy cost
God help the universe if we ever discover FTL travel and escape the prison of lightspeed.
I have a new religion!
Prometheus didn’t gift us fire and cognition. Lies. We are Prometheus’s curse on the universe. Nothing more than a plague on the gods creation, concocted for some slight we can never understand. The sum of us, brought into being, then tossed into the void and forgotten. To spread like an oil stain across creation.
“And behold, I Myself am bringing floodwaters on the earth, to destroy from under heaven all flesh in which is the breath of life; everything that is on the earth shall die.” - Genesis 6:7
“If you had not committed great sins, God would not have sent a punishment like me upon you.” - Genghis Khan
seriously though, I think life on other planets probably just usually evolves underground, so even if they develop some sort of intelligence they’re not looking up at the sky so they have no motivation to explore beyond their atmosphere no matter how advanced they get.
there was a planet in The hitchhiker’s Guide to the Galaxy universe that had thick cloud cover so that people never even conceived of an existence beyond their planet. when a spaceship crashed there, it never even occurred to them that it might have come from the sky
Sadly it may be the speed of light.
All these intelligent species are simply trapped in their own solar systems for all eternity by an unbreakable natural law.
But surely generational ships would get us over that?
Not really, no. Generational ships might make colonizing the nearest star systems possible, but even colonizing our own galaxy would require some kind of suspended animation. The milky way is between 100,000-200,000 light years in diameter so even at the speed of light, you’re looking at a travel time that is ~33-66% of the time that humanity has even existed(homo sapiens are currently estimated to have become a distinct species 200,000-300,000 years ago)… just to go to ONE star system out of the hundreds of BILLIONS that exist in our galaxy. You’re gonna need generational ships so self-sustaining and capable that the generation that actually arrives at the destination will have long forgotten the point of the trip and might not want to leave the comfort of the ship.
Still, colonizing our own galaxy is at least theoretically possible, given enough time. The real filter is just how unimaginably large the universe is. The vast, VAST majority of the observable universe is FOREVER out of our reach, as it is expanding away from us faster than the speed of light. Then there’s the unobservable universe, which could literally be infinitely bigger than the observable universe for all we actually know.
That’s why faster than light travel is the holy grail. Without it, we’re just kind of stuck.
Imagine if wormholes had zero constraints on the physical location of the other side of the wormhole though. We could open a portal to OUTSIDE the observable universe. What a mindfuck. We might even find a false vacuum decay racing towards us at the speed light, or regions of space that are contracting instead of expanding, or initiate a new big bang by opening a wormhole to an area of space where that hasn’t happened…we could travel to a point where we can watch the milky way get formed, since the light of its formation is just reaching that region of space. If it turns out the heat death of the universe is just a local phenomenon, we could continue expanding forever beyond it. World without end.
Generational ships wouldn’t have to reach the edge of the galaxy, just the next planetary system. There’s no reason civilization needs to remain centered on Earth, either. Think of it as a wave traveling outward, where it eventually reaches the edge, by many smaller hops. It will also eventually reach earth, where they might wonder at signs of a prehistoric civilization. Actually, think of it like the Middle East, where empires rise and fall, crusades and jihads burst through, religions rise out of nowhere, people speak many different languages. A galactic civilization could be dynamic and ever changing, distance can make us strangers to each other, the fate of any planet matter only to its inhabitants and neighbors
Sure, that’s an option. It doesn’t really change my overall point though that anything beyond galactic colonization is unrealistic on any time scale. Our next nearest neighbor, the Andromeda Galaxy, is over 2.5 MILLION light years away, over 10 times farther than my “crossing the milky way” example, with nothing in-between to make a pit stop if needed, you have to cross the true void of space to get there.
And that’s just to get the next nearest galaxy. Current estimates suggest the observable universe contains 2 TRILLION galaxies.
True, you’re not getting to the next galaxy. However within the galaxy, your generation ships only need to work for a century or two per voyage. That’s at least conceivable
AFAIK there is no known energy source that would keep a generation ship powered for the duration of an interstellar flight.
The person to whom you responded is half right. The speed of light is half of the barrier to interstellar travel. Entropy is the other half.
Would you need a power source? If you aim your ship correctly, then put everything alive into cryo, the ship could go completely dark, vent all heat and become a frozen rock. Then after [very long time] the ship enters the vicinity of a different star and can be reactivated and unfrozen using solar energy. You dont need energy to maintain cryo if the whole ship is at 1° kelvin.
(Of course that relies on cryo sleep being possible)
Or synthetic life. (Robots)
Only if they can be turned off (same as the cryo sleep). The whole ship either has to have enough energy to last potentially 100000 years (no theoretical power source exists like that) or enter a state of 0 energy consumption. Solar/radiation collectors dont work if you are to far from a star. Synthetic life still needs energy
The whole ship either has to have enough energy to last potentially 100000 years.
Well, that depends on how far you’re going. If you pick a nice close target, let’s say 3 light years away, you can potentially get there pretty quickly. With fusion propulsion systems you could make the trip is something like 70 years, coasting most of the way. I’d need to check the math to get exact numbers, but I recall fusion allowing for pretty reasonable trip times.
But if you can survive for hundreds or thousands of years, then solar sails become an option. Then it becomes a materials science problem of how thin can you make a sail that will still hold together. The greater the sail to payload ratio, the faster you go.
Also, you’d need to know for certain that the planet you’re sending your generation ship to is habitable for your species. While this may be technologically trivial for a society that can build a functional generation ship, the timescales for such projects (literally hundreds or even thousands of years from the launch of the probe to the yes/no signal) makes it extremely difficult to actually organise.
Lol we get to the planet and find it was obliterated by a gamma ray burst 50 years ago
Or just send a lot of ships and hope one or two find something good.
That and you won’t even know if the destination civilization is still there by the time you arrive.
Plus isn’t the rate of expansion of the universe increasing? So at some point, even going at light speed, your destination will recede faster than you can travel.
Not really. Galaxies are pretty stable, stars orbit around the central black hole in the galaxy. You can absolutely travel between stars in the same galaxy, even if it takes a thousand years.
just reverse entropy
INSUFFICIENT DATA FOR A MEANINGFUL ANSWER
import fuckit && !!
Until we figure out how that is possible outside of theory, it is just that. We have no plans that address actually keeping a spaceship working on such a timescale, and keeping the crew alive on top of it.
Considering we haven’t seen any generational alien ships visit, it seems like nobody else has figured it out yet, either.
No. At best maybe a few reach the nearest inhabitable solar system.
Information can travel at light speed. So, I think there’s more to it personally
There doesn’t need to be more to it than that. The observable universe is over 93 billion light years in diameter. That means even at the speed of light, it would take over 6.5x longer than the universe has even existed for anything to cross that distance… except the universe is expanding faster than the speed of light, so actually you need to go significantly faster than light to make it across. FTL is, sadly, still firmly in the realm of science fiction, so to the best of our current knowledge most of the universe is permanently inaccessible.
Light speed is very slow
That is very sad.
It may very well be republicans
Even if you had a super intelligent species that can make Dyson spheres and travel at the speed of light the observable universe is beyond vast. I don’t know much about cosmology or our ability to detect light but given humans have only been looking into the sky for a couple centuries, not being able to see a thimble in the ocean seems like a non issue. I think if you scale the observable universe down to the size of earth the speed of light becomes 0.05 mph.
evidence of human existence has only gotten what, 150 lightyears out into space?
Eh. The amount of oxygen in out atmosphere is pretty much impossible by non-living processes alone iirc. Anyone who can do astro-spectroscopy can probably tell there’s life here, from thousands of light years away.
and if life is as abundant as we think, how are they going to tell the difference between intelligent and non-intelligent life
Life is so rare, finding ANY life is worth investigation
that has nothing to do with why I asked that question lol. if you have to investigate every single one that shows signs of life, that would mean investigating a lot of worlds before you find any with intelligence.
By the color of their hats /jk
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.
Well I’m doing my part to make sure the oceans are full of Arctic ice for the great boil off
When they do boil off they need to make sure to have a hell of a lot of cocktail sauce and melted butter on hand.
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
That is an interesting idea that is not typically considered in the drake equation as far as I know. That could significantly reduce the chance of finding intelligent life elsewhere.
I think it is in the drake equation effectively, it factors into the length of time that the civilization might send and receive detectable signals - It doesn’t say why the Civilisation might collapse, but the planet becoming uninhabitable is surely one reason. On wikipedia for Drake Equation the Carl Sagan specification of L is in terms of the “fraction of planetary lifetime”.
I think a missing factor might be how directional transmission and receiving is, if we can’t broadcast to and listen to the whole sky equally then we might have a 1/r-cubed type issue with the chances of both listening and transmitting with enough strength/energy at the same time.
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.
This is my favorite, mainly because it’s been well argued by some respectable scientists.
Another is that we’re in a simulation, and aliens aren’t part of it. There are also some very good statistics pointing to the simulation theory, from just sheer scale.
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.
Howabout a reasonably advanced civilization destroying itself and its homeworld after exploiting and then running out of petroleum?
Oil has a bad reputation but how lucky we are to have it. How does a civilization on a planet without hydrocarbons make the leap to a technological species?
It’s not impossible, but it’s got to be a lot harder.
Kelp farms? Domesticated bamboo? We need large areas of land to grow food anyway, we just skipped the charcoal agriculture step. Lathes and the three plate method are the real heroes of industry any way.
A slower ascension into the computing age could mean a more stable set of cultures and a more uniform global situation to avoid anthropogenic filters. Bright candles and all that.
I think it’s a fair thought that any form of life doesn’t perfectly recycle their resources and all forms of life give off waste for other life to utilize. That said, a reasonably advanced civilization might just inevitably grow to the size where the waste they put off makes their planet unlivable for them before they can take action to control it.
For us, it’s carbon dioxide.
Don’t forget plastics and pesticides! Those get everywhere, and many are bioavailable by design.
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.
Time itself is the filter. I don’t think we are the first, but I don’t think we will every find any other intelligent life. The universe is too big and our lives are far too short to make any sort of attempt to travel or communicate across those distances ourselves. I’m also not entirely confident our idea of what a society is will last in any meaningful way over the timespans required. Our longest lasting dynasties rarely make it more than a couple hundred years. Space is just too big for us to work with using our current understanding of physics.
My favorite filter is the amount of phosphorous in the universe. Earth has an unusually high amount, and it’s vital for life. I like this one, because as more stars die, the amount of phosphorous goes up, implying we won’t be alone forever.
Anyway, look up “Issac Arthur” on YouTube for HOURS of content about the Fermi paradox and potential great filters.
I’m gonna add to this by saying phosphorus may be my favorite, but I think the most likely filter is just time, twice.
Do you know how unlikely it is that earth has been habitable for so long? Do you know how long life was single-celled? One of the theories for how advanced (eukaryotic) cells formed was the combination of at least three different branches of life into the same cell! Archaea (cell wall), bacteria (mitochondria/chloroplasts), and viruses (nucleus). Do you know how unlikely that sounds? Do you know how long it would take for that to happen randomly? Most planets probably aren’t even habitable for that long. Once we became eukaryotic, we started progressing much faster.
Then, keep in mind, the life has to continue to exist for billions of more years while it waits for the advanced life to happen again within the same section of the galaxy. So, time is two filters - both behind us and in front of us.
Thanks, I’ll check it out!
Throwing in another similar YouTube suggestion of John Michael Godier
Honesty, I don’t think that there is a Great Filter. The Fermi Paradox strikes me as not very well-reasoned. A whole hell of a lot of things would have to go exactly right for civilizations to make contact, rather than it being the default assumption. There are lots of filters, not just one Great one.
But the closest to a Great Filter is that space is really, really. stupendously big. The chances of even detecting each other across such distances is vanishingly small, much less traversing them. Add in the difficulty of jumping the metabolic energy gap to become complex life, and that could reduce the density of civilizations down to a level that they’re just not close enough to each other in spacetime to admit even the possibility of contact. And we’re hanging our hat on some highly-speculative concepts like alien mega-structures harnessing whole solar systems to allow detection.
I think a lot of persnickety, smaller filters combine to make interstellar contact between civilizations against long odds. Perhaps the best we’ll get is spectral signatures from distant planets that are almost-conclusive proof of some sort of life.
I think you’re probably closest. There aren’t “filters” so much as we live in a universe that can only support life on a highly contingent basis, entirely by accident, at random intervals. It’s filters all the way down, really. None of us are getting out alive, might as well enjoy it while it lasts.
I think at some point, almost certainly not in our lifetimes, we’ll detect the spectroscopic signatures of a planet that has an atmospheric makeup that HAS to be from life, but with no detectable signs of any civilization. Just nonsentient life. And we may never be able to get there.
Energy needed to leave your planetary system vs energy available on your planet of origin.
We have not yet overcome it and I am not sure that we will achieve it.
Well, we’ve already sent a couple of probes out of the solar system, but they’re not really going fast enough to have any meaningful interstellar impact.
Yes, but I mean leaving the planetary system not only with isolated elements, but with parts of our civilization.
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.
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.
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.
Assuming that knowledge and resource locations are retained. Roman’s had great concrete. Took a long time to reestablish what Humans already had and mixing raw materials is not complicated.
After the Roman Empire, the use of burned lime and pozzolana was greatly reduced. Low kiln temperatures in the burning of lime, lack of pozzolana, and poor mixing all contributed to a decline in the quality of concrete and mortar
We need a Foundation project to restart society If we want to avoid this. Worst case solar cells becomes myth like Greek fire.
