Let’s say that, throughout sci-fi means you care to postulate, we discover with absolute certainty that the Sun is going to go nova in one year. (Yes, I know stars of Sol’s type don’t go nova. Play along.)
Let us also say that through different sci-fi means I, ersonally, have discovered an earth-type planet, conveniently uninhabited by sapient beings and ripe for colonization, around, say Alpha Centauri, and also possess an FTL drive capable of propelling a ship there in a reasonable period of time–one year, say. (We won’t worry about relativistic effects; it’s not like we’re coming back). But in the time remaining, Earth can only build enough ships to transport one million people (along with supplies, livestock, et cetera).
Finally let us assume that I, Maxie, am in command of this fleet. I have both the will and the power to enforce my edicts. I and my colleagues have a lunar base, beyond the reach of any technological power on Earth, so there’s no question of President Bush or Putin or anyone else interfering; and my colleagues are all as loyal to me as Cubs fans, so there’s no thought or hope of a mutiny.
The first 800,000 berths go to families with young children. The next hundred K spots go to engineers, physicians, farmers, teachers, et cetera, persons possessing skills that will be clearly needed on Tellus Secunds. I and my staff are choosing the spots, and we make sure to keep the first two groups ethnically mixed.
We’ve a hundred thousand spots left to fill. We screen propective ark passengers for genetic defects, STDs and other diseases, and so forth. You come up green on all counts.
Persuade me to give you a spot.