But unlike the multi-generational effort of cathedral-building, sailing always came with the promise that a few lucky survivors might live to see the end of the voyage. Makes me wonder if under current laws conspiring to condemn your unborn children to life in the confines of a spaceship might have legal repercussions while still in earth.
(actually I'm not even sure about cathedrals, to the best of my limited knowledge the idea of starting them as multigenerational projects might just as well be a retrospective fiction. Are there sources that show that they were not just started I unrealistic schedule expectations?)
You're right about cathedrals, and it applies to several such big architecture projects (temples, etc). It's also how science operates when you think about it — that quest so far has always been far bigger than anyone, you know you'll die trying from the beginning, that you won't see where it all leads eventually.
- such ships are likely to be orders of magnitude more 'modern', comfortable, heaven compared to anything we know in terms of habitat even on Earth — a very basic promise of space habitats is that you can make them much, much better than any planet can do 'randomly'; and that would happen far before we even think of physically going to another star.
- assuming generations on a ship, it's entirely possible that colonizing a planet feels "ancient", "backwards" to these people now born and raised in space; such "spatians" might just choose to remain so (bummer for the founders of the mission, but a decently good move for evolution too).
- there are several ways to "colonize" a distant world. One is to go there and breed on the way. Another is to send a genetic "boot" (think a few million distinct human DNAs that machines would grow in vitro just prior to arrival, AI to teach them whatever it is they need, etc). This is within known science, but maybe cryogenics are also possible (that's a third option then).
These questions become incredibly complex (and fascinating) the deeper you dig. I think we can rely on 'truths' that were valid for 'enough' generations as being 'plausibly also true' in the near future (symmetrically in time: so if something's been true for human beings for ~5000 years, then it stands to reason that it won't change before, on average, at least as long).
It should thus be observed that culturally, we are currently have an extremely short-term view in the Western world; there's a huge contrast with Asia in that regard — where it's not uncommon for businesses to plan for 2030-2040, and 2050-2060 looking at 2100 in politics. Think about it, that's only 3 generations away at the current rate. It's really not that far. It will be vastly different because tech, but also vastly the same because human beings.
Do watch that video, he talks about these things very astutely! :)
(actually I'm not even sure about cathedrals, to the best of my limited knowledge the idea of starting them as multigenerational projects might just as well be a retrospective fiction. Are there sources that show that they were not just started I unrealistic schedule expectations?)