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The term virtual is a concept applied in many fields with somewhat differing connotations, and also denotations. Colloquially, 'virtual' has a similar meaning to 'quasi-' or 'pseudo-' (prefixes which themselves have quite different meanings), meaning something that is almost something else, particularly when used in the adverbial form, e.g. "He's virtually [almost] my boyfriend."

Contents 1 Physics 2 Computing 3 Philosophy 4 Work Teams

Physics

In physics, one may speak of theoretical virtual particles, - particles which exist for period of time which is not enough to mathematically define their energy. Due to wave nature of all particles their energy and time of existence (as well as position and momentum) are entangled by mathematical definition called Fourier transform. This entanglement results in Heisenberg uncertainty principle - central principle of quantum mechanics.

Virtual particles (photons, electrons, positrons, mesons, protons, etc) must be included in calculations in order to accurately model and predict interaction of real particles (see Feynman diagram). Before such an account quantum mechanics suffered serious unaccuracies, while after inclusion of virtual interactions it became most accurate theory ever created (it is called quantum electrodynamics ). Predictions of quantum electrodynamics agree with observations to errors of measurement - currently to one part in 10^12-10^13.

Computing

In computing virtual is what does not physically exist, but is made to appear to by software: examples this usage can clearly be seen in virtual memory and, although somewhat differently, in the popular sci-fi/IT concept of 'virtual reality'. Important concept in object-oriented programming is a virtual function.

Philosophy

Numerous philosophers have advanced conceptions of the virtual.

The current definition, that can hardly be distinguished from "potential", originates in medieval Scolastics and the pseudo-Latin "virtualis". Most prominent of these in contemporary philosophy has been Gilles Deleuze, who uses the term virtual to refer to something that every object carries with it, which is neither its reality nor merely what it could have been, but rather what it is imagined to be. "Virtual" is therefore taken to mean a potential state that could become actual. "Virtual" is not opposed to "real" but to "actual", whereas "real" is opposed to "possible".

Recently this conception of the virtual has been challenged and another core meaning has been elicited (Denis Berthier, "Meditations on the real and the virtual" - in French). It is based both upon science (virtual image), technology (virtual world) and etymology (derivation from virtue - Latin virtus). At the same ontological level as "possible", "real" or "potential", "virtual" is defined as that which is not real but displays the full qualities of the real - in a plainly actual - i.e. not potential - way. The prototypical case is a reflection in a mirror: it is already there, whether I am here or not to see it; it is not waiting for any kind of actualization. This definition allows one to understand that real effects can be issued from a virtual object, so that our perception of it and our whole relation to it are fully real. It explains that virtual reality can be used to cure phobies - which remains contradictory in any conception for which the virtual is a kind of potential.

Work Teams

Internet technology fostered the environment for virtual work in teams, with members who may never meet each other in person. Communicating by phone and email, with workproducts shared electronically, virtual teams produce results without being co-located.

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