Comment by Balgair

A late uncle of mine did his thesis at Arizona on the practical limitations of interstellar travel.

The TLDR of it is that teenagers suck.

They assumed the physics of those days (mostly unchanged) and no faster than light travel [0] and that you can't reasonably cryo-sleep a human or grow them on site[1].

From that, you follow the logic and if you want to run a ship out to some star, it's going to take a long ass time. So much so that you have to have kids, a 'generation' ship. And that's where the trouble starts. Because teenagers are going to teenager, they just will not trust you when you say that the outside of their very little world is deadly. And then when you get there, it's going to take a lot of convincing to reprogram them to jump out and start colonizing.

The only solution is to build a really big spaceship. He reasoned that it's usable surface area needed to be about that of Japan [2]. So you get to a Stanford Torus or the like. That's when you can finally 'trust' that the people living on this thing wont blow up halfway there and can remain 'stable' enough over the (possibly) millennia of travel.

The issue, of course, is that you'd just build all these things for use in the Sol system anyway - why bother traveling?

Something something new lands something exploration something.

Okay, so, like, the end result is that putting human on a new planet in another system is just not happening when you really take a look. That was the essential conclusion to the thesis.

It's too hard, teenagers suck too much, and the 'cheaper' alternatives are too good.

[0] He made a great point that you should not assume that our modern understanding of physics should remain the same when doing really long term calculations like this. We have advanced so much in our knowledge and likely the understandings of other fields will compound much faster in the future.

[1] Same for biology, but they had to start somewhere.

[2] this assumption is a bit much for me even today, but the steps he takes are sound. You can argue them down a lot though, I feel.