I think that you're giving it a bad focus.
Why do WE have to be abe to reach stars?, if we can travel at 0'01·C, then none of us will reach Alpha Centauri... but if you can build a self sufficient vessel, with an habitable biosphere, maybe the gradchilds of our grandchilds could settle in a far distant world. The matter is NOT lifespan, a human individual cannot live forever and i hope we never reach that point, but the HUMAN beeings can, as specie
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