Do you think there can't be any civilizations in the universe which exist indefinitely? For the past millions or even billions of years? If humans get past the next couple of centuries and start spreading out into the solar system and possibly beyond, what would cause us to have a last generation?
That's so far away that "indefinitely" applies. If I told you could live until there was no more usable energy left in space, would you worry about not being immortal?
This gets straight into realms of like eschatology and the sources of and constraints on life, areas in which I hold deeply unpopular beliefs compared to the norm here.
The most neutral way I can phrase this is that I think life is a planetary expression, more or less fundamentally inseparable from the planet on which it emerges. We may eventually be able to break those bonds but I don't think we're anywhere near as close to that as we think we are, nor do I think we should even try.
I can't see that there's a moral way for people exit the solar system boundary out "into the stars." No one making that choice can arrive there, or even experience an appreciable part of the trip in one life. It's committing generations to be born, live and die for no purpose except to exist and to breed for some future goal of some past people. I believe this to be wicked.
People have always migrated into the unknown in the hope of something better for the people who will call them ancestors. But they've also always been able to make certain promises: that the sun will shine on them as it does on us, that crops will grow even if they aren't the crops we know, that the air is safe to breathe, that god will hear them there. Some of those people have been wrong about some of those things, but they always had good reason to trust in them.
We don't have reason to believe any of that about anywhere other than here. It's possible to imagine a future so grim that the best chance for our offspring is for us to force them to risk these unknowns. It's our responsibility to prevent that choice being necessary.
We can imagine things that could change this calculation. FTL, centuries-long human cryogenics, cross-lightyear microbiology. These are fantasies. If these powers are ever in anyone's grasp, that people will be fundamentally different from what we are, even if they came from us. I don't know what will be right for them and I have no claims on what they do.
Focusing on those far off fantasies of another people is a failure to appreciate our place here, the cosmic gift we've been given with our solar system. It is an understandable weakness but we should fight it. We have enough future in front of us as ourselves, we should leave the unrecognizable far depths of it to the unrecognizable people who will inhabit it.
Highly recommend Kim Stanley Robinson's novel Aurora, an exploration of precisely these concepts written in the fascinating perspective of a generation ship's AI instructed to narrate its journey.
The idea of going multiplanetary is not to abandon Earth out of necessity, but out of precaution. When you make a backup of your hard disk, it's usually not because you intend to go use your other one for target practice. Waiting to leave Earth when problems become clearly insurmountable is akin to waiting to backup your HDD until you notice it's failing. Indeed the very first thing we should start doing once we begin colonizing our second planet is planning to colonize the third.
There are countless ways human civilization, if not the human species, can come to a rather abrupt end: supervolcano explosion blotting out the sky, directed gamma ray burst destroying the atmosphere ( hypothesized as one of the reasons for the great ordovician extinction ), comet impact acting similar to the supervolcano, random evolution creating a supervirus, and so on. And the countless ways we might manage to kill ourselves go without saying: nuclear war, nukes, deploying weaponized viruses, even far more innocuous things like fertility < 2.5 for too long.
Many of these causes can, have, and will happen abruptly.
Human lives aren't data to be stored against future need. These "backups" aren't redundant; they will have worth, and demands, and dreams, and rights of their own. Are we adequately accounting for that when we imagine this interstellar future? Are we able to meet our responsibility to them with the dignity they deserve? I strongly do not think we are.
It's chilling but correct that so much of the language around this concept talks of colonies, because that is what we're discussing. Other lives, kept far away, for some benefit to ourselves, but not to them.
Until we can present a plausible vision for "the good life" in space, away from the earth that birthed us, we should not be pursuing this goal. If we end then so be it. We have many other means to reduce that possibility, much more accessible, that we're refusing to use right now. Let's pick up that shovel and see how far we can get first.
I don't necessarily agree with giraffe_lady, but I can see the argument where leaving the planet fundamentally changes what we currently consider "human" society to a point where it no longer can be a considered a continuation of the general earthly society. Evolution maybe, but less star trek and more belters from the expanse but taken to an absolutely extreme extent. Maybe closer to something like Seven Eves.
There definitely can be human civilizations that last indefinitely, so long as we stop keeping all our eggs in one basket, planet-wise.
Once we get humans living far enough apart that information about pandemics travels faster than pandemics do, then we should be largely invincible, barring suicide from ennui.
The larger our sub-galactic civilization, the more resilient it becomes to things like total war, total political revolution, etc.
It's really hard to be a galactic emperor at multi light-year distances. By the time you wipe out half the population of the empire, the other half will have doubled.
It's also easily conceivable that in less than 100 decades from now, global unrest or war will make us regress 100 decades. Climate change in particular is going to cause a lot of problems with feeding people.
Maybe so, but that would be straying from the point.
GP said "there can't be any human civilizations that last indefinitely" and in response I gave an easily conceivable version of how human civilizations can last indefinitely.
But what you've posted is science fiction, in contrast there have been a number of historical civilization collapses. Something that's easily conceivable in the mind isn't necessarily practical or going to happen.
It's been over 50 years since humans last set foot on the moon. While there's hope that man will land on the moon again by 2025, success is not assured, and a catastrophic accident could set manned space missions back by decades.
Yes, we might collapse and never recover, but the universe is a really big place, so there might be civilizations which avoid that. And if they did, then maybe we can also.
The fact that no one has figured it out in over 13 billion years kinda suggests not, doesn't it? That's pretty much the Fermi Paradox, and perhaps the answer.
The psychological tension that is inherent to capitalism (indefinite exponential growth is required, unbounded exponential growth is impossible) requires that the system be under plausible existential threat at all times.
