“As long as we are a single-planet species, we are vulnerable to extinction by a planetwide catastrophe, natural or self-induced. Once we become a multiplanet species, our chances to live long and prosper will take a huge leap skyward.” — David Grinspoon (American astrobiologist) One of the greatest challenges of traveling to another star has to do with the sheer amount of energy necessary to get humans to another star within their own lifetimes. Hence why some proponents of interstellar travel recommend sending spacecraft that are essentially miniaturized worlds that can accommodate travelers for centuries or longer. These “Generation Ships” (aka. worldships or Interstellar Arks) are spacecraft that are built for the truly long haul. — Matt Williams (From Universe Today: Space and astron