In his notes, physicist and engineer Robert Goddard described a futuristic scenario based on the premise that the Sun is burning out and human beings will face extinction on Earth. To survive, people would have to build a fleet of enormous space arks (or colonize and then redirect entire asteroids), each of which would travel toward a different cluster of stars where a solar system with a habitable world might exist. Each ship must contain all the human knowledge, literature, art, and technology necessary to seed a new civilization.
Goddard suggested that the ships might travel the immense distances to other stars using something he called "intra-atomic energy" (foreseeing atomic power). Otherwise, liquid hydrogen and oxygen, the fuel used in many rockets today, would combine with solar energy to power the arks.
