On youtube’s Kurzgesagt a new video explains why humans can’t possible far outside our solar system, due the enormous distance. Only way out would be to somehow travel faster than light (ftl) which is of course currently impossible.
Interesting to think about how this is ‘solved’ in science fiction stories:
Warp speed
One way obvious way is to make ftl possible is something like warp-speed as we all now from Star Trek. Obvious because it’s basically you suddenly can travel faster than light due to some not in detailed explained process of the bending of light. It assumes spaces is uneven, so if you can travel somehow in a ‘direct line’ you can overcome the lightspeed-barrier. In many books and movies there’s a similar mechanism like in the later novels of three-body-problem. It’s somewhat boring as it basically means spaceships do go faster, they can go to any place in a somehow linear fashing (e.g. everything further away means longer travel, you can ‘catch’ up, and there’s now slowing of time).
Stargates, portals
In series Stargate there’s another solution, conduits, gates or portals that allow you to travel near instantly from one place to another. In the Expanse books by James Corey there’s a similar mechanism. The catch is you can only travel to places where there is already such a gate. So you, or someone before you, first has to travel in an old-fashioned-way (slower than light) to a place.
In almost all books this problem is ‘solved’ be a former (usually mysteriously disappeared) civilization that has places the gates at interesting problems.
How could humans do would be interesting, first sent a robot and then wait for a few centuries to millennia for the robot to arrive at an interesting location. Wouldn’t be a very interesting science fiction series however.
Hibernate, deep freeze
Another solution is to used in some science fiction series and movies is to have travelers go into hibernation. Ships still travel slower than light, but for the passengers that’s not a direct problem as there in deep sleep, coma or frozen. Only catch of course is that time actually passes for many years or centuries. So even if they would return, the world they know would no longer be.
This might a viable way for interstellar travel. There are probably enough people who’d volunteer. People who’d stay behind might however never know in there lifetime if interstellar travel was a success at at.
The recently-made-into-a-movie ‘Hail Mary‘ by Andy Weir uses this way of travel, although the passengers only go in some coma so they do age.