How big is a human's (space) bubble - in other words: how far could we (as mankind) transport a human being from Earth in such a way that the being would be still alive? (Let's not consider returning.)
I'm a novice in space travel but I suspect the most difficult part is sustaining life in space for a non-trivial period without external support; the second most difficult might be accelerating the spacecraft in such a way that it covers the most distance in the available timeframe. (Colloquially: The bigger the spacecraft the easier I'd believe to support living on it; however it makes it harder to move around.)
Since it's a fully speculative exercise, everything that's realistically available currently or could be built in a relatively short time based on what we know and possess now can be used.
I guess it's a much-discussed scenario (by beers or otherwise) but I don't know how to search for it. Any pointers are welcome.