Quote Originally Posted by The_Mark
And they will probably be greeted by a thriving human colony established by the first human visitors of Gliese, who left 200 years after the generation ship, using some snappy anti-matter propulsion.
This "paradox" gets even funnier if they're traveling near the speed of light, then you can have the same persons that borded the ship to be 200 years late. Poor buggers
Point was, that we can evacuate "humanity" within a few years if things go badly. That I wouldn't recommend it unless you're very, very desperate (and the sun turning too hot or into a red giant would be such a thing) is another matter.