The 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."

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. The willingness to question previously held truths and search for new answers resulted in a period of major scientific advancements, now known as the Scientific Revolution. ... Theoretical physics attempts to understand the world by making a model of reality, used for rationalizing, explaining, and predicting physical phenomena through a physical theory. There are three types of theories in physics: mainstream theories, proposed theories and fringe theories. ... In the description of the interaction between elementary particles in quantum field theory, a virtual particle is a temporary elementary particle, used to describe an intermediate stage in the interaction. ... The Fourier transform, named after Jean Baptiste Joseph Fourier, is an integral transform that re-expresses a function in terms of sinusoidal basis functions, i. ... In quantum physics, the Heisenberg uncertainty principle, sometimes called the Heisenberg indeterminacy principle (a title prefered by Niels Bohr - see quantum indeterminacy), expresses a limitation on accuracy of (nearly) simultaneous measurement of observables such as the position and the momentum of a particle. ... Fig. ...

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. This article needs to be cleaned up to conform to a higher standard of quality. ... Quantum electrodynamics (QED) is a quantum field theory of electromagnetism. ...

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'. Virtual memory is intended to help the programmer by taking care of some memory housekeeping duties. ... Virtual reality (abbreviated VR) describes an environment that is simulated by a computer. ...

Philosophy

Numerous philosophers have advanced conceptions of the virtual. 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. Gilles Deleuze Gilles Deleuze (January 18, 1925 - November 4, 1995) was a major French philosopher of the late 20th century. ...

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. A team comprises any group of people or animals linked in a common purpose. ...