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130 In 1952, Leslie Shepherd of the British Interplanetary Society published what may have been the first technical article on human interstellar flight. After analyzing propulsion requirements, he found that travel to other stars might be possible if we are willing to accept transit times of greater than 100 years, and possibly 1000 years. Shepherd concluded that there does not appear to be any fundamental reason why human communities should not be transported to planets around neighboring stars, although the transit time is so great that many generations must live and die in space. Interstellar exploration and colonization may require a revolution in our way of life, not only socially but biologically.” Mallove and Matloff came to a similar conclusion 37 years later. Our brief human existence is incompatible with the enterprise of starflight, except to the extent that we are happy to leave the joy of future discoveries and experiences in other solar systems to our descendants. Even today, analysts believe that our current understanding of physics does not allow human interstellar flight beyond nearby stars, unless we build giant world- ships and develop the concept of flight through generations.*° Such worldships are not a new idea. Tsiolkovskii had proposed a “genera- tion ship” in 1928. Stapledon, writing in 1937, visualized immense explora- tion vessels many miles in diameter, constructed in space. He foresaw high-speed artificial “worldlets” voyaging from system to system, toward the thousands upon thousands of planetless stars that awaited encirclement by rings of worlds.” Some worldship technologies might first be employed to build space colonies in our own solar system. British physicist J.D. Bernal imagined globe-shaped colonies, 10 miles across, in 1929; sooner or later, he specu- lated, pressures such as the imminent failure of the Sun would force an adventurous colony to set out beyond the bounds of our solar system. O’Neill, who developed the space colony concept in much greater detail in the 1970s, suggested that a modified version of a space community will have traveled to a nearby star within the next few centuries.” Sustaining such a society would raise significant sociological issues. Robert Heinlein’s science fiction stories “Universe” and “Common Sense,” published in 1941, showed how generations of people born on an interstel- lar ark might lose track of the original purpose of the voyage. Sociologists Direct Contact Human Voyages Interstellar travel... . is essentially not a problem in physics or engineering Lee Raves See bd but a problem in biology. —Freeman Dyson, 1964**