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.
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.
That is very sad.
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
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.
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
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.
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.
I do agree that in the grand scale of things we’re actually very early. That alone would explain a lot.
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 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.
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.
Probably too optimistic and unhinged, but maybe a species advanced enough for interstellar travel, building mega structures etc. are advanced enough to ascend to a higher plane of existence or alternate dimensions or whatever. Maybe there’s some alternative to this reality that will be unlocked by advanced technology that made all advanced life prefer that, to here.
That’s a really neat idea I’ve never heard before. Like, maybe our entire universe is analogous to the ocean floor sea-vents that life arose out of. Cold, and dead, and boring, and difficult. And one day we’ll discover how to ascend.
I also like this theory. In the Ian Banks Culture series civilizations that get advanced enough head off into the “sublime” they call it. Basically a higher level of existence. In my own more simple version, I’d figure VR and the biological/cyborg mix get so good the powerful can start living kind of forever, so they head for that substrate and don’t need big megastructures for anything, they just need computing power.
Yeah, it seems very possible that at one point, civilization will turn inward instead of outward. Why go through the time and effort to colonize the stars when you can just create a cyber-utopia? If you’re advanced enough, you could make it feel like an eternity while almost no time passes on the outside.
Sure, your planet might get destroyed by a cataclysmic event in the far future, but if you can make that feel like billions or trillions of years, who really cares?
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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.
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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.
It may very well be republicans
I like the “Dark Forest” theory I learned from the Three Body Problem books. Basically it’s dumb for civilizations to make a big footprint and reveal themselves because other civilizations won’t know how powerful and dangerous you might become, and so out of precaution they might just zap you. Ironic and over dramatic, but just because that’s a possibility it might be wise to keep a low profile and not invite trouble.
The “Dark Forest” is fine for a scary sci-fi series, but it has many flaws that make it unrealistic as a real solution to the Fermi paradox.
- Earth has been quite obviously life-bearing for at least 2 billion years. We should have been wiped out long ago.
- The book series made up fantasy magic tech for how exactly a civilization can be destroyed by another without giving away their own location. I’ve yet to see an explanation for how that would be done in reality that doesn’t give away the attacker’s location.
- It doesn’t explain why nobody has colonized the galaxy.
I think others wouldn’t bother with us until we started demonstrating likelihood of using dangerous tech or crazy exponential expansion.
I don’t remember well, but I think civilizations stationed their defensive or offensive tech away from their own civilizations, just dispersed around.
I think its explanation for why no one or anything has colonized the galaxy though is that if anyone shows signs of becoming that strong, they get zapped. Nobody wants to see a neighbor rise up into a behemoth, you get that bold you’re a threat.
My real preferred theory of why we don’t see other civilizations though is that I think they choose more inward, VR, computer-based evolution that doesn’t result in big mega structures.
I think others wouldn’t bother with us until we started demonstrating likelihood of using dangerous tech or crazy exponential expansion.
Why do you think that, though? It doesn’t make sense, frankly - if you’re worried about competition evolving you shouldn’t wait until the last possible second to destroy it. That raises so many unnecessary risks of being slightly slow on the draw, and then it’s too late. Why not do it at the earliest convenience, when it’s super easy to do by comparison and there’s an incredibly long margin of error if you somehow miss the first couple of tries?
I don’t remember well, but I think civilizations stationed their defensive or offensive tech away from their own civilizations, just dispersed around.
I think its explanation for why no one or anything has colonized the galaxy though is that if anyone shows signs of becoming that strong, they get zapped.
But they’re already doing it, you just said they’re putting outposts out there. If they can’t do that secretly then the Dark Forest doesn’t work in the first place. Placing a secret weapon base in another solar system is no different from placing a colony there.
My real preferred theory of why we don’t see other civilizations though is that I think they choose more inward, VR, computer-based evolution that doesn’t result in big mega structures.
As with many Fermi paradox solutions this one fails on account of requiring every single civilization (and every single subset of those civilizations) to all decide to do exactly the same thing, forever, with no exceptions. In a scenario like this what happens if a single subculture of a single advanced civilization decides for whatever reason that they prefer not to do that? They would be able to spread throughout the cosmos without opposition, everyone else is locked in their little dream boxes and therefore is basically irrelevant. It only needs to happen once, and the universe has been around for a very long time.
I agree, I don’t think they’d wait until the last possible moment when the civilization becomes super powerful or builds the mega weapon. I just mention it along the range of development to highlight the why.
I think they might let weaker civilizations keep going, though, just out of hope they wouldn’t be too mean. Also, zapping other civilizations when you don’t need to exposes yourself and your own aggression.
About the shift to VR /computer substrate worlds that wouldn’t have huge footprints, I agree that not all would do that, and it only takes one to go the big building and footprint route and it’s weird we don’t see it.
My guess then would be that maybe they do build big, but they just conceal well…? You get good enough tech at some point you can choose to be hard to see.
I’ve never read the three body problem (started it but just couldn’t finish…it was very slow paced and there were moments when the Chinese…I don’t want to call it propaganda but more like promotion…took me out of it, like the supposedly international coalition of scientists where the non Chinese ones were just cardboard cutouts) but I can speak to this:
The book series made up fantasy magic tech for how exactly a civilization can be destroyed by another without giving away their own location. I’ve yet to see an explanation for how that would be done in reality that doesn’t give away the attacker’s location.
Relativistic missiles. Nothing moves faster than the speed of light. So if you can get a big rock to go 95% of the speed of light, we’d only be able to detect that it’s coming right as it hits. Sure, you can calculate the origin of the missile after it obliterates its target, but it’s almost impossible to form a counterattack especially if the attacker just yoinked an asteroid from a different star system than their own and strapped an engine on it. And ESPECIALLY if your civilization is still mostly planetbound.
And a rock moving at some appreciable fraction of the speed of light could obliterate the Earth.
Relativistic missiles. Nothing moves faster than the speed of light. So if you can get a big rock to go 95% of the speed of light, we’d only be able to detect that it’s coming right as it hits.
This is a very common answer to “how”, but it comes with lots of problems in the Dark Forest context.
- If you actually calculate how much energy is required to boost a big rock up to that speed you run into lots of difficulties. It takes a lot, a heck of a lot. How does a civilization that is “hiding” accumulate that energy? How does it store it long-term?
- How is that energy actually put into the rock? This is basically a starship accelerating up to that speed and getting a starship up to that velocity is not easy even if you have the energy available. Does it have a rocket? The rocket equation for getting up to near-lightspeed requires ridiculous amounts of propellant. Is it beam-propelled? You’re not being at all stealthy that way. How much acceleration can you get out of your system? It takes a full year at one Earth gravity of acceleration to get up near lightspeed, and that’s a really high acceleration - you generally trade acceleration for efficiency so the faster you want to get up to speed the more energy you need and the noisier you’ll be.
- It actually is possible to counter an RKV. It’s much easier to hit and destroy an RKV than it is to launch it, all you need to do is get a pebble in its path. The key is detection, and the above points give some pretty good options for detecting it before and during launch. That gives you time to fire your countermeasures.
And ESPECIALLY if your civilization is still mostly planetbound.
Absolutely not guaranteed to be the case. Earth’s civilization could have easily had offworld colonies by now if circumstances had been slightly different, so a Fermi paradox solution that requires reliably blowing up Earthlike civilizations before they can get offworld doesn’t work. They’re already too late.
As I said previously, Earth has been quite obviously life-bearing for at least 2 billion years. Why wait until something like an RKV is needed, and even that is not guaranteed? They could have destroyed life on Earth far easier, and thus far more stealthily, if they’d done it a billion years ago.
I agree, either we’ve escaped detection or the dark forest theory is wrong.
Couldn’t antimatter bursts get an object to extremely high speeds relatively cheaply?
Well, “relatively cheaply” is a hard standard to nail down. I would say “no”, though. Antimatter is very expensive to manufacture and store and you’re going to need a lot of it. All of the energy that comes out of an RKV hitting its target has to be put into it in the first place, probably several times over given the inefficiencies likely inherent in the process.
Fair enough, guess it depends on how many resources they’re willing to sink into first strike capability. Maybe a strongly expansionist civilization would have such a more efficient use of resources it would quickly catch up to a dark forest predator trying to wipe them out. Like a swarm of piranha eating a shark.
Tbf we are noises as fuck. We’ve been sending so much out for decades.
Sure, but it’s just small game chatter. We start building a Dyson sphere powered starkiller cannon or some such nonsense we might pop up on somebody’s radar.
The problem for the Fermi paradox is that there’s no reason to do stuff like that before we start colonizing other solar systems.
Also, how do you destroy a civilization that has a Dyson swarm already? That’s not exactly an easy task, and if you insist on remaining stealthy yourself it’s nigh impossible.
Military Industrial Complex: “Hold my beer”
The galaxy is a bowl of M&Ms. One of every hundred M&Ms is poisoned and will immediately kill you. It’s only a 1% chance you’ll die. Well maybe pike 5% if you eat a handful.
Most of the civilizations might even be moral enough not to destroy us, but all it takes is one.
How do they do it, though? It’s not really a valid solution unless you can explain how it works, otherwise it’s just “maybe some magic happens that kills civilizations.”
Once a civilization has begun spreading to hundreds of other solar systems I have yet to hear of any plausible way to reliably “kill” it.
Guns? Bombs? Surely you can kill a civilization. Not sure why magic would be required.
I don’t think you’ve thought through the logistics required for the sort of war where you’d just go around and shoot everyone who lives in hundreds of solar systems. Even assuming they do nothing at all to defend themselves, how do you even find them all?
Yep exactly. Who knows how murderous other civs might be, maybe they’re nice but maybe not.
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”
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.
There seem to be so many coincidences that make our solar system unique that it’s really upsetting lol It’s like we are so perfect for stability because of things like Jupiter keeping the inner system “clean” of large impactors, our part of the galaxy being more “quiet” than typical as far as supernovae, stuff like that which makes it seem even less likely for life to exist anywhere else. :(
Life will almost certainly be fairly common, given the right conditions. On earth, it seems to have appeared not long after conditions made it possible. We either won the lottery on the first week, or the odds aren’t actually that bad.
The problem is, we can’t detect life right now. We can only see potential communicating civilisations. These are a lot rarer. We currently know of 1, humanity. That will change in the next few years. We have telescopes being designed/built capable of detecting the gasses in the atmosphere of an earth sized planet. While we won’t recognise all life types this way, a lot will show up in abnormal gasses, e.g. free oxygen. This should help bound the possibilities a lot.
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.
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.
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
Boy, Lemmy sucks donkey dick. For every one legitimate answer there are two or three edgelord answers like “capitalism” and “the internet”.
Here’s an answer that hasn’t come up yet: cooperation among mono cellular organisms. I don’t mean the development of polyp analogues or colonies of single celled organisms; I mean getting down to mitochondria. Brace for wild oversimplification.
Before mitochondria, life had a hard time creating enough energy to do much more than barely stay alive. The current line of thinking is that one organism ate another and didn’t digest it. The two organisms worked symbiotically, one handled energy production and the other handled getting food and staying alive.
Just about every living thing utilizes mitochondria and if the current idea that mitochondria were actually symbiotic organisms is true, that means that what was likely a chance “sparing” of prey is the underpinning of all complex life.
The odds of that happening are ridiculously low. There could be simple life in tons of places even within our own star system, but if the mitochondria-like symbiotic capture never happens for those extraterrestrial organisms, then complex life is probably unlikely to develop.
Edgelord teenagers are a plague on lemmy
A - fucking - men
Still not as bad as reddit though
your paragraphs complaining about it are a lot more annoying than the people who might not be being totally serious on the internet for a minute.
If by “paragraphs” you mean two sentences, sure.
If you’d bothered to read past those two sentences you’d see that I was making an offhand comment before answering the question.
nah if you open up just insulting all the people around you, I don’t owe you reading the rest of your post.
Case in point for Lemmy being a shit hole.
Good answer. This seemed relevant enough to share, it’s certainly interesting. https://newatlas.com/biology/life-merger-evolution-symbiosis-organelle/
Maybe cooperation is hard wired just like competition. It might be less likely but hardly impossible.
I’d hardly describe it that way. It took untold trillions of predator/prey interactions over the hundreds of millions of years that single celled life existed for it to happen. That’s more or less brute forcing the problem and it took geologic timescales to happen.
If you ask me to point at a hurdle stopping civilizations from developing that looks awfully reasonable.
Ultimately we don’t know much about that era of time, but I suspect it was less like fumbling around for millions of years looking for a light switch, and more like the gradual warming of the planet with warmer and cooler seasons/years.
Iirc at least one of the other things related to development of eukaryotes was that atmospheric oxygen had to first be generated by early cyanobacteria.
So maybe that proverbial light switch was being flipped millions of times through random encounters but only became more viable after the voltage (atmospheric oxygen levels) became high enough. Maybe that’s the reason it took hundreds of millions of years, because transforming by bacteria just takes that long.
We just don’t know unfortunately. However, we DO know about species getting wiped out by asteroids or human cultures getting wiped out by disease or conflict with superior cultures. Any of these filters seems more of a hurdle to me than the development of eukaryotes.
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
Howabout a reasonably advanced civilization destroying itself and its homeworld after exploiting and then running out of petroleum?
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.
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 would say it’s the size of the universe and the fact that it is still expanding at an accelerated rate.
If the speed of light is really the “top speed” of the universe, it is inadequate for interstellar travel. It is barely good enough for timely communication, and not really even that.
Life can be as likely as it wants to be, but it seems to me that we’re all quite divided, to the point of not being able to communicate at all with other potential intelligent species.
Isn’t the fermi paradox specifically dealing with detection tho? Not just travel or communication.
I suppose I was focusing on detecting some sort of communications. It still matters that when we see objects at great distance in space, it’s the objects in the distant past
This universe being unfriendly to interstellar and especially intergalactic travel would seriously hamper a galactic civilization, and thus be less likely for us to notice them.
There might be hundreds of civilizations out there, each having only expanded to a few dozen stars, not caring to go further. Even the makeup of the interstellar medium might be incredibly dangerous, basically necessitating generation ships to cross. Large scale expansion might simply be too hard.
That expansion at an accelerated rate - that’s just so eerie when you think about it. The furthest objects we can see right now will slip away out of reach forever for the next generation, and so on. It’s crazy to think that as time goes on, there will be less and less universe to observe.
That’s something really interesting, though. When we look at distant objects, we aren’t limited by the distance they’re at right now. We’re limited by the distance they were at when they emitted the light.
So the observable universe is still growing because the edge of that bubble is such a long time ago that everything was still much closer together.
But the light that reaches us is constantly getting stretched (red-shifted), so I’m not sure that our bubble is growing. Instead when they’re stretched too thin, we won’t be able to see it. I’m not 100% sure on the expansion rate of the universe and the pace of red shifting. Also, eventually all the galaxies are expected to be pushed so far away from each other due to the pressures exerted by Dark Energy, that soon we’ll only be able to see just the stars of our Milky Way.
One of the weirdest facts. One that really makes you feel so small.
