The idea of an elevator to the heavens may sound preposterous, like an updated version of the Tower of Babel. But it’s a serious proposition. Two independent NASA teams recently thrashed out the technological requirements for such a project and found them to be feasible. Extraordinarily demanding, yes, but feasible. “You’re looking at something we can seriously consider building by the end of this century,” says David Smitherman of NASA’s Marshall Space Flight Center in Huntsville, Alabama, who led one of the teams. The space elevator — an idea long consigned to the wastebasket of pipe-dream technologies — now looks like a real possibility.