Mach's principle parvaz-e Mach Fr.: principe de Mach The local → inertial frame and the → inertia of any body results from the distribution of all matter in the Universe. This principle has been neither confirmed nor refuted. → Mach number; → number. |
Newtonian principle of relativity parvaz-e bâzânigi-ye Newton Fr.: principe de relativité de Newton The Newton's equations of motion, if they hold in any → reference frame, they are valid also in any other reference frame moving with uniform velocity relative to the first. → Newtonian; → principle; → relativity. |
Pauli exclusion principle parvaz-e sokolân-e Pauli Fr.: principe d'exclusion de Pauli A quantum mechanical principle according to which no two identical → fermions can share the same → quantum state. Also known as → exclusion principle. In honor of Wolfgang Pauli (1900-1958), Austrian theoretical physicist, who formulated the principle in 1925; → exclusion; → principle. |
perfect cosmological principle parvaz-e keyhânšenâsik-e farsâxt Fr.: principe cosmologique parfait The → assumption, adopted by the → steady-state theory, that all observers, everywhere at all times, would view the same large-scale distribution of matter in the → Universe in all regions and in every direction. In contrast to the → cosmological principle, the perfect cosmological principle adds the assumption that the Universe does not change with time on the large scale. → perfect; → cosmological; → principle. |
principle parvaz (#) Fr.: principe A fundamental, primary assumption, or general law from which others are derived. From M.E., from O.Fr. principe, from L. principium "a beginning, first part," from princeps "first, chief, prince," literally "that takes first," from primus "first" + root of capere "to take." Parvaz "origin, root, stock" (as used in particular by Ferdowsi); cf. Av. fra-vāza- "drawing from; leading onward," from Av. fra-, frā- "before; forward, forth" (fratəma- "first, front," pouruua- "first," fra-cara- "preceding;" O.Pers. fra- "forward, forth;" Mid.Pers. fra-; cf. Skt. pra- "before, formerly," prathama- "earliest, initial," pūrva- "first;" Gk. pro; L. pro; O.E. fyrst "foremost," superlative of fore) + vaz- "to draw, guide; bring; possess; fly; float," vazaiti "guides, leads" (cf. Skt. vah- "to carry, drive, convey," vahati "carries," pravaha- "bearing along, carrying," pravāha- "running water, stream, river;" L. vehere "to carry;" O.E. wegan "to carry;" O.N. vegr; O.H.G. weg "way," wegan "to move," wagan "cart;" M.Du. wagen "wagon;" PIE base *wegh- "to drive;" see also → flight). |
principle of action and reaction parvaz-e žireš va vâžireš, ~ koneš va vâkoneš Fr.: principe d'action et de réaction Newton's third law of motion, which states that for every action there must be an equal and opposite reaction. |
principle of constancy parvaz-e pâyâyi tondi-ye nur Fr.: principe de la constance de la vitesse de la lumière The second postulate in Einstein's theory of → special relativity whereby the → velocity of light in → vacuum has the same absolute value in all → inertial reference frames irrespective of the direction and speed of propagation of the light source. It should be emphasized that this constancy of the speed of light holds among → reference frames moving uniformly with respect to each other. An observer accelerated with respect to a light source will measure a speed of light that is smaller than the speed of light measured in a → rest frame. See also → principle of relativity. |
principle of covariance parvaz-e hamvartâyi Fr.: principe de covariance In special relativity, the principle that the laws of physics take the same mathematical form in all inertial frames of reference. → principle; → covariance. |
principle of equivalence parvaz-e hamug-arzi Fr.: principe d'équivalence In → general relativity the principle which states that in the immediate proximity of an → accelerating system the acceleration is physically equivalent to → gravitational force. This principle also implies the equivalence of → gravitational mass and → inertial mass. Same as the → equivalence principle. See also → Einstein's elevator. → principle; → equivalence. |
principle of excluded middle parvaz-e miyâni sokalândé Fr.: principe du milieu exclu, ~ ~ tiers ~ The second principle of → formal logic introduced in Aristotle's theory of the → syllogism: A statement is either → true or → false. In other words, two → contradictory → propositions cannot both be true. The truth of one implies the falsehood of the other. Also called law of excluded middle and → principle of excluded third. |
principle of excluded third parvaz-e sevomi sokalândé Fr.: principe du tiers exclu Same as → principle of excluded middle. |
principle of identity parvaz-e idâni Fr.: principe d'identité The first principle of → formal logic introduced in Aristotle's theory of the → syllogism: If a statement is true then it is true. Also called → law of identity. |
principle of least action parvaz-e kamtarin žireš, ~ ~ koneš Fr.: principe de moindre action The principle that, for a system whose total mechanical energy is conserved, the path to be taken for the system from one configuration to another is the one whose action has the least value relative to all other possible paths and from the same configurations. Also called Maupertuis' principle, least-action principle. |
principle of non-contradiction parvaz-e nâpâdguyi Fr.: principe de non-contradiction The third principle of → formal logic introduced in Aristotle's theory of the → syllogism: No statement can be both → true and → false at the same time. Also called → law of non-contradiction. → principle; → non-; → contradiction. |
principle of relativistic causality parvaz-e bonârmandi-ye bâzânigi-mand Fr.: principe de la causalité relativiste One consequence of the theory of → special relativity, according to which no two events separated by a distance greater than their separation in time multiplied by the → speed of light may have a → causal influence on each other. Violation of this principle leads to → paradoxes, such as that of an → effect preceding its → cause. → principle; → relativistic; → causality. |
principle of relativity parvaz-e bâzânigi Fr.: principe de relativité The first postulate in Einstein's theory of → special relativity whereby all the laws of physics are the same in every → inertial reference frame. In other words, no physical measurement can distinguish one inertial reference frame from another. See also → principle of constancy. → principle; → relativity. |
relativity principle parvaz-e bâzânigi Fr.: principe de relativité The requirement employed by Einstein in his relativity theories, that the equations describing the laws of physics are the same in all frames of reference. This statement and that of the constancy of the speed of light constitute the founding principles of special relativity. Relativity; → principle. |
Ritz combination principle parvaz-e miyâzeš-e Ritz Fr.: principe de combinaison de Ritz An empirical rule discovered before the advent of quantum mechanics which states that it is possible to find pairs of spectral lines, which have the property that the sum of their wavenumbers is also an observed spectral line. Named after Walther Ritz (1878-1909), a Swiss theoretical physicist; → combination; → principle. |
strong anthropic principle parvaz-e ensân-hasti-ye sotorg Fr.: principe anthropique fort A version of the → anthropic principle that claims that the → Universe must be suitable for the formation of → intelligent life at some point. Compared with the → weak anthropic principle, this version is very controversial. Its implications are highly speculative from a scientific viewpoint. |
superposition principle parvaz-e barhamneheš Fr.: principe de superposition 1) Math.: The principle concerned with homogeneous and
non-homogeneous → linear differential equations,
stating that two or more solutions to a linear equation or set of linear equations can be added
together so that their sum is also a solution. → superposition; → principle. |