I'm not sure that anything about staying on Earth 9000 years obviously or necessarily implies extinction, so I definitely prefer your actual explanation to your

I'm not sure that anything about staying on Earth 9000 years obviously or necessarily implies extinction, so I definitely prefer your actual explanation to your original remark. Thank you for it. However, it must be admitted that there is some time before 9k years where a 1.1% population growth rate becomes a problem, not to mention the fact that the 9k-year result is not about a sustainable population, but rather about the point where every particle in the Universe would be a constituent part of a human body. A great many doublings (multiples of ~65 years) before that, we've exhausted the local resources of this star system and have to put growth "on hold" to reach another one. We don't seem to be able, right now, to put either our growth or industry on hold long enough to save the planet we're on. Furthermore, it's not at all demonstrable that we can move a significant fraction of 8 billion people off of the planet in a timely manner, even if we could get them all to volunteer. Using conventional rockets, it's going to be like 10 tons of CO2 per person per trip in fuel, and that's just to lift the passenger's weight, to say nothing of the fraction of the weight of the spacecraft per passenger. And that's just to LEO. A low estimate is handily 4 or 5 years of current CO2 emissions just to move half the population. (Launch guns and the like could possibly reduce this, but there's certainly going to be a CO2 cost to building them if they are possible.) The remaining 4 billion would, presently, need to learn the lessons that neither the 9k-year discussion nor this discussion seem to have landed for you: growth, per se, is unsustainable; and we will have to manage both growth (into territory that oscillates about 0) and efficiency to survive. In reality, we're just boxed in on Earth, waiting for a miracle like fusion. Whether this discussion turns out to be productive or not, the fact that steady positive exponential growth always overtakes resource availability for any finite set of actually finite resources is germane. In other words, there is no real difference between "in the Solar System" and "on Earth" as far as our ability to live within foreseeable constraints is concerned. If we "move out into the solar system" now and behave as we do now, we will just die a few hundred years later (subject to even being able to meaningfully get there). Sci-fi futures don't arrive just because you're on a rocket. You still have to learn the lessons and build the systems with the political will you can muster. That's the point. Just because you can't or don't want to take in the implications of growth at a rate proportional to the amount present doesn't mean that I'm not making productive points. I would, however, appreciate more precision from you in the future, please, just by way of striving toward being productive.