[shiroiushi]

Sure, it's obviously an enormous challenge and totally beyond our current capabilities, but my point is that it's not at all impossible, it's just a matter of priorities. Humanity could do it if they really wanted to. The physics aren't that hard or in the realm of sci-fi. (I'm not sure the resulting ship would survive, but that's another matter. They'd really need to make many of such ships to make sure at least one survives the trip.) It would require developing significant capabilities for space-based construction of course, which means mining operations in space, manufacturing, etc., none of which we currently possess, so it's not even something that could be done in a decade like the Apollo moonshot, but if humanity really wanted to do this, it could be done in a century I think.

Humanity doesn't really want to do a project like this, however.