Etymology: [ad. med.L. virtulis, f. L. virtus virtue, after L. virtusus. From L. virtut-, virtus manliness, valour, worth, etc., f. vir man.]
Definition:
- Existing or resulting in essence or effect though not in actual fact, form, or name.
- Existing in the mind, especially as a product of the imagination.
- Created, simulated, or carried on by means of a computer or computer network.
- Simulated using electronic, optical, or other indirect means in order to resemble something Physical.
- In particle physics: applied to particles and processes that cannot be directly detected and occur over very short intervals of time and space with correspondingly indefinite energy and momenta, which are not necessarily conserved within the time involved.
D'Alembert's principle, or the principle of virtual work, is a statement of the fundamental classical laws of motion. It is equivalent to Newton's second law. It states that the sum of the differences between the generalized forces acting on a system and the time derivative of the generalized momenta of the system itself along an infinitesimal displacement compatible with the constraints of the system (a virtual displacement), is zero.
He had undergone some strange experiences in his absence; he had seen the virtual Faustina in the literal Cornelia, a spiritual Lucretia in a corporeal Phryne; he had thought of the woman taken and set in the midst as one deserving to be stoned, and of the wife of Uriah being made a queen; and he had asked himself why he had not judged Tess constructively rather than biographically, by the will rather than by the deed? - Thomas Hardy - Tess of the d'Urbervilles - A Pure Woman
According to the theory..the emission of alpha particles by radio active nuclei is to be explained by the assumption that there exists in the nucleus a ‘virtual’ level of positive energy, which is occupied by an alpha particle. -Proceedings of the Royal Society A. CXXXIII. 228, 1931.
The Virtual Gallery, by Stephen Peters
This image was inspired from the April '95 cover of Scientific American. It features paintings from several artists, all texture mapped onto different surfaces. The floor is a light blue marble, generated with Perlin's noise function, with a perfectly reflective gazing sphere sitting in the middle.
For those interested in the artwork, the paintings are, from left to right, Magritte's "Chateau des Pyrenees", DaVinci's "Mona Lisa", Seurat's "Sunday Afternoon on the Grande Jatte", Dali's "Persistence of Memory", and Vermeer's "The Concert". In the sphere you can make out Escher's "Dewdrop".
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