80 plus planets seem to have reunited as the Ekumen – a name derived from the Greek "oikoumene", meaning "the inhabited world", although characters occasionally refer to it as "the Household", which is in turn a reference to the Greek "oikos", a word which developed from the same root as "oikoumene". Unexplained references are made by the protagonist from Terra in the Left Hand of Darkness to a long-past "Age of the Enemy", which presumably refers to the time that the Shing controlled Terra, portrayed in City of Illusions. Planets The Ekumen (or the League of All Worlds, though that is also believed to be the previous planetary coalition, before some sort of galactic crisis) contains a very large number of planets and is continually exploring new ones. Genly Ai in The Left Hand of Darkness explains that there are 83 planets in the Ekumen, with Gethen a candidate for becoming the 84th. The process of reaching out to potential civilizations is a tedious and sometimes dangerous one. Technology Societies tend to use sophisticated but unobtrusive technologies. Most notable is the ansible, an instant-communication device that keeps worlds in touch with each other. Physical communication is by NAFAL (Nearly As Fast As Light) ships. The physics is never explained; the ship vanishes from where it was and reappears somewhere else many years later. The trip takes slightly longer than it would to cross the same distance at the speed of light, but ship-time is just a few hours for those on board. It cannot be used for trips within a solar system. Trips can begin or end close to a planet, but if used without a "retemporalizer", there are drastic physical effects at the end of long trips, at least according to the Shing, whose information may be suspect. It is also lethal if the traveler is pregnant. City of Illusions mentions automatic death-machines that work on the same principle as the ansible and can strike instantly at distant worlds. Such a device is clearly used in the events of Rocannon's World. The weapons are not mentioned again in later books. Churten theory, as developed by the physicists of Anarres, should allow people to go instantly from solar system to solar system. It is a development of the work of Shevek, whose tale is told in The Dispossessed. Shevek's work made the ansible possible—it is mentioned in his tale that