No one knows for sure what a long-range space journey will be like for the people on board. Nobody in the history of our species has ever had to deal with the “Earth-out-of-view” phenomenon, for instance. How will it feel to live in close quarters with a small group, with no escape hatch? How will space travelers deal with the prospect of not seeing family or friends for years, or even ever again? How will they occupy themselves for years with nothing much to do?
Researchers do know some