Parallel Universes, Alternate Dimensions, Virtual Worlds, and Other Fictional Places

A fictional universe is a self-consistent fictional setting with elements which differ from the real world. It may be called, variously, a fictional or imaginary realm, world, or universe.

A fictional universe can be almost indistinguishable from the real world, except for the presence of invented characters and events which characterize a work of fiction. It can also bear little or no resemblance to reality, with invented fundamental principles of space and time. The subject is most commonly addressed in reference to fictional universes which differ markedly from reality, such as those which introduce entire imaginary cities, countries, or even planets, those which contradict commonly known facts about the world and its history, or those which feature fantasy or science fiction concepts such as magic or faster than light travel, and especially those in which the deliberate development of the setting is a substantial focus of the work.

It may be contained in a single work, or be developed in a succession of works, as frequently happens in fantasy or science fiction series. Its history and geography may be well-defined, and even languages may be constructed. When subsequent works are written within the same universe, care is usually taken to ensure that established facts of the canon are not violated.

The computer accesses a computer-simulated world and presents perceptual stimuli to the user, who in turn can manipulate elements of the modeled world and thus experiences telepresence to a certain degree. Such modeled worlds may appear similar to the real world or instead depict fantasy worlds. The model world may simulate rules based on the real world or some hybrid fantasy world. Example rules are gravity, topography, locomotion, real-time actions, and communication. Communication between users has ranged from text, graphical icons, visual gesture, sound, and rarely, forms using touch, voice command, and balance senses.

Massively multiplayer online games commonly depict a world very similar to the real world, with real world rules and real-time actions, and communication. Communication is usually textual, with real-time voice communication using VOIP also possible.

Virtual worlds are not limited to games but, depending on the degree of immediacy presented, can encompass computer conferencing and text based chatrooms. Sometimes, emoticons or 'smilies' are available, to show feeling or facial expression. Emoticons often have a keyboard shortcut. Edward Castronova is an economist who has argued that "synthetic worlds" is a better term for these cyberspaces.