This would be my guess. We see complex ecosystems arise and all kinds of niches filled again and again and again after each mass extinction and subsequent diversification event. We’ve run the laboratory experiment here on Earth a number of times over the last few million years, and our sort of intelligence has shown up only once (and greatly changed the planet at a staggering pace when it did). I think life, even complex multicellular life, could have arisen in older solar systems a couple billion years ago, evolved and into complex ecosystems that suffered numerous extinction and rediversification events, lasted for a few billion years until their suns changed and changed conditions on the planet, and died out - with intelligent species never evolving.
Once we have a significant presence in space, with habitats capable of indefinitely supporting hundreds or thousands of humans without solar power in the outer solar system (or at least as long as the fission or fusion supplies last) and once these habitats have the capacity to harvest resources in-situ and to manufacture things (like space habitats) out of those resources - I don’t see how we would STOP people from hopping over to the next star over.
Are we all just assuming that humans will magically overcome the light speed limit?
Because the answer of how to prevent people from “hopping over to the next star” is that they would die of old age very early on in the thousand-year trip.
The light speed limit itself may be the great filter. Maybe it’s not possible to overcome.
Well, war. We blow up any colonies that try to leave. It’s not like they can be really sneaky about it, and we would certainly have the capability of doing so.
It’s not my most optimistic outcome, but I see it as a real possibility.
Nope.
The next star over could probably be reached in a couple decades with a ship we could realistically build someday, but even if it took millenia, how is that a problem?
If the people living in a station that orbits Neptune, or out in the Oort Cloud, who were born on a station and had never set foot on a planet in their lives, decide they want to shove their station to Alpha Centauri - that just means they won’t have any visitors for a few centuries until they arrive in Alpha Centauri and start building more stations.
No, we are not, not at all. Where would you even get such a notion?
As already stated, it is not an individual person travelling star to star, but civilization itself expanding.
If a dumb rock like Oumuamua can travel between the stars, I don’t see anything stopping doing it intentionally with much smarter rocks.
As mentioned in this thread several times, it’s not necessary to overcome in order for a species to expand its influence across the galaxy.
Not to mention that self replicating AI could also seed the galaxy, even if the parent species stays home.
Or even if the parent species was wiped out in the AI revolution.
The concept of an interstellar civilization doesn’t make any sense if we’re confined by the speed of light. Sending arks out as self-sufficient pockets of civilization that are completely on their own forever would make those pockets functionally equivalent to aliens. They would have no contact with, help from, trade with, or any kind of interaction with any other star system.
That would not be an interstellar civilization, so I guess I assumed that’s not what we were talking about.
I agree that the point of the Fermi paradox is not an overarching civilization, but just intelligent life expanding without any kind of overall political structure, but…
What if instead of figuring out FTL travel, instead we just figured out how to make humans live tens of thousands of years. Trade with/migration to other star systems would still be onerous, but at least people would get some benefit from doing it and would have some benefit to doing it and it would be worthwhile participating in some kind of overarching government that regulated it.
If aliens visited us, would it really make any practical difference to us whether they’re still in communication with and governed by their homeworld?
@the mods: I’m aware that this thread has basically shifted into discussing the Fermi paradox, let me just say, as the OP I’m cool with it. 
Information is the best and easiest thing to be traded. It would not be that hard for the homeworld to maintain contact with pretty much the entire galaxy, if it so wanted, by simply sending lasers out targeting each one, and updating them on the current news and science.
If a civ is on the other side of the galaxy, sure, the info would be out of date, but would it matter?
The point is this: it appears that the resources required to either litter the universe with probes, or make any kind of detectable signal, is pretty small. A small faction, or even individual, of an advanced species could leave such evidence with months, or less, of effort.
We do not need to assume humanlike behavior to see a conflict between this observation and the proposition of advanced life existing elsewhere.
In fact the problem is the opposite of your framing: it is people that wish to use psychological explanations for the Fermi paradox who need to make claims about how aliens think.
Finally on the Fermi paradox nomenclature itself: I really wish it wasn’t called “paradox” as people consistently get the wrong idea about it.
And, in fairness, I think in its initial formulation it was indeed making the claim we should see aliens, and why dont we?
But I think it has long since evolved past to the more generic “Based only of what we know of the universe, it’s entirely consistent that there would be many advanced species and lots of evidence of their existence. We see no such evidence. And that means there are significant unknowns beyond our current understanding. Let’s discuss what those might be, and which we can rule out”.
It’s a basic evolutionary drive for all lifeforms on Earth to copiously reproduce and expand into every available niche. We’ve still got Donald Trump types who desire spreading their seed far and wide, gaudify the landscape with a hotel on every street corner and fight tooth and nail for power and control over others.
And then you have people like me who are content with a modest house, a couple kids who I can keep an eye on, and care about not destroying the environment for future generations.
I think my mindset is more enlightened and the result of higher conscious awareness. Perhaps our advanced alien civilizations are more like me. Perhaps they are happy and content controlling a cluster of half a dozen local star systems, keeping there population in a viable state of homeostasis and doing their own thing with no care for the Universe at large. Bigger isn’t always better. Maybe they figured that out.
Yeah, that’s kinda the whole point of life. It’s what life has done since the moment that some complex molecules found a way to reproduce themselves billions of years ago. It’s pretty well ingrained.
And your family lineage will be out competed by the people who “spread their seed far and wide”.
And as far as future generations go, those are numbered as long as we stay here on this rock, in this solar system. That number of potential future generations goes up a whole lot once we leave it behind.
The environment of the galaxy is extremely wasteful, ever second burning fuel that would keep a modest civilization running for a trillion years. I would say that going out and harvesting the galaxy is protecting the environment for future generations. Sitting on our rock and looking at the pretty lights in the sky is what is wasteful and destructive.
Perhaps, perhaps. And it’s quite possible there are some out there like that. However, in order for it to be a solution to the Fermi paradox, you have to show why every alien civ would be like that.
Or conversely, maybe they’ve developed fantastic technologies that allow them to explore other universes in the multiverse, which they find far more interesting than this boring one, which they’ve long since discovered to be much the same everywhere, just with biological variations.
No, they wouldn’t, given the right propulsion technology. There is no apparent limit to the speed of a spaceship as measured by the proper time inside the ship, due to time dilation. There is only an increasing disparity between the ship’s proper time and the time at its original point of departure.
As has frequently been mentioned, a photon experiences no time at all. Even if its lifetime was just a nanosecond before decaying, it could travel arbitrarily great distances.
It may well be the great filter.
There are limits. If nothing else, at a high enough speed, the CMB turns to hard gamma radiation.
There’s a high probability I’m confused, so let me restate my understanding of what the conversation was.
We should see aliens because we’re an eyeblink away from getting to the stars ourselves, so they should be too, or already did so long ago.
I say we’re not an eyeblink away, we’re infinitely far because at this point our only solution to the light speed problem is essentially magic.
Alternately, if we travel at conventional speeds in self-contained arks, we could make it to the closest stars. But my point here is that we would not then be an analog for the alien races we should be seeing. In other words, we did not progress that eye blink in this hypothetical. We should not be obviously detectable in this hypothetical. So if that’s really how it works, why should we see aliens?
My main point is that there’s probably hundreds of civilizations thousands of light years away, and they can’t see us and we can’t see them and never the twain shall meet because light speed is the great filter. And that’s why we don’t see them.
Yes I was going to mention that. Spacecraft travelling fast enough to experience significant time dilation would suffer damaging impacts with microscopic dust, as well as the radiation hazard you mention.
Better to take a little longer and arrive in safety.