accurate to n decimal places rašmand bâ n raqam pas az jodâgar yâ momayez Fr.: précis à n décimale, ~ avec n chiffres après la virgule, à
n décimales près An expression specifying the number of meaningful digits to the right of the → decimal point. For example, e = 2.71828 ... = 2.718 is said to be accurate to three decimal places and 2.72 to two decimal places. |
apparent place jâ-ye padidâr Fr.: position apparente Same as → apparent position. |
catalog place jâ-ye kâtâlogi Fr.: position catalogue Same as catalog position and → mean catalog place. |
decimal place raqam pas az jodâgar, ~ ~ ~ momayez Fr.: décimale, chiffre après la virgule The position of a digit to the right of a → decimal point written in decimal notation. In 0.032, for example, 0 is the first decimal place, 3 is the second decimal place, and 2 is the third decimal place. Raqam, → digit; pas, → after; jodâgar, momayez, → decimal point. |
displacement jâ-be-jâyi (#) Fr.: déplacement Physics:
A vector quantity that specifies the change of position of a body or
particle from the mean position or position of rest. From displace, from → dis- + place + -ment. Jâ bé jâyi, noun of jâ bé jâ literally "place to place," from jâ "place," from Mid.Pers. giyag "place," O.Pers. ā-vahana- "place, village," Av. vah- "to dwell, stay," vanhaiti "he dwells, stays," Skt. vásati "he dwells," Gk. aesa (nukta) "to pass (the night)," Ossetic wat "room; bed; place," Tokharian B wäs- "to stay, wait;" PIE base ues- "to stay, live, spend the night." |
displacement current jarayân-e jâ-be-jâyi (#) Fr.: courant de déplacement In electromagnetism, a quantity which is not a real current (movement of charge), but has the units of current and has an associated magnetic field. The physical meaning of this displacement current is that a changing electric field makes a changing magnetic field. → displacement; → current. |
Kant-Laplace hypothesis engâre-ye Kant-Laplace Fr.: hypothèse de Kant-Laplace The hypothesis of the origin of the solar system proposed first by Kant (1755) and later by Laplace (1796). According to this hypothesis, the solar system began as a nebula of tenuous gas. Particles collided and gradually, under the influence of gravitation, the condensing gas took the form of a disk. Larger bodies formed, moving in circular orbits around the central condensation (the Sun). Named after the German prominent philosopher Immanuel Kant (1724-1804) and the French great mathematician, physicist, and astronomer Pierre-Simon Marquis de Laplace (1749-1827); → hypothesis. |
Laplace Laplace Fr.: Laplace The French great mathematician, physicist, and astronomer Pierre-Simon Marquis de Laplace (1749-1827). → Laplace operator; → Laplace plane; → Laplace resonance; → Laplace transform; → Laplace's demon ; → Laplace's equation ; → Kant-Laplace hypothesis |
Laplace operator âpârgar-e Laplace Fr.: opérateur de Laplace Same as → Laplacian. |
Laplace plane hâmon-e Laplace Fr.: plan de Laplace The plane normal to the axis about which the pole of a satellite's orbit → precesses. In his study of Jupiter's satellites, Laplace (1805) recognized that the combined effects of the solar tide and the planet's oblateness induced a "proper" inclination in satellite orbits with respect to Jupiter's equator. He remarked that this proper inclination increases with the distance to the planet, and defined an orbital plane (currently called Laplace plane) for circular orbits that lies between the orbital plane of the planet's motion around the Sun and its equator plane (Tremaine et al., 2009, AJ, 137, 3706). |
Laplace resonance bâzâvâyi-ye Laplace Fr.: résonance de Laplace An → orbital resonance that makes a 4:2:1 period ratio among three bodies in orbit. The → Galilean satellites → Io, → Europa, → Ganymede are in the Laplace resonance that keeps their orbits elliptical. This interaction prevents the orbits of the satellites from becoming perfectly circular (due to tidal interactions with Jupiter), and therefore permits → tidal heating of Io and Europa. For every four orbits of Io, Europa orbits twice and Ganymede orbits once. Io cannot keep one side exactly facing Jupiter and with the varying strengths of the tides because of its elliptical orbit, Io is stretched and twisted over short time periods. This commensurability was first pointed out by Pierre-Simon Laplace, → Laplace; → resonance. |
Laplace transform tarâdis-e Laplace (#) Fr.: transformée de Laplace An integral transform of a function obtained by multiplying the given function f(t) by e^{-pt}, where p is a new variable, and integrating with respect to t from t = 0 to t = ∞. |
Laplace's demon pari-ye Laplace Fr.: démon de Laplace An imaginary super-intelligent being who knows all the laws of nature and all the parameters describing the state of the Universe at a given moment can predict all subsequent events by virtue of using physical laws. In the introduction to his 1814 Essai philosophique sur les probabilités, Pierre-Simon Laplace puts forward this concept to uphold → determinism, namely the belief that the past completely determines the future. The relevance of this statement, however, has been called into question by quantum physics laws and the discovery of → chaotic systems. |
Laplace's equation hamugeš-e Laplace Fr.: équation de Laplace A → linear differential equation of the second order the solutions of which are important in many fields of science, mainly in electromagnetism, fluid dynamics, and is often used in astronomy. It is expressed by: ∂^{2}V/ ∂x^{2} + ∂^{2}V/ ∂y^{2} + ∂^{2}V/ ∂z^{2} = 0. Laplace's equation can more concisely expressed by: ∇^{2}V = 0. The function V may, for example, be the potential at any point in the electric field where there is no free charge. The general theory of solutions to Laplace's equation is known as potential theory. |
mean catalog place jâ-ye miyângin-e kâtâlogi Fr.: position catalogue moyenne That point on the → celestial sphere at which an object would be seen from the solar system → barycenter affected by the → e-terms → aberration. |
mean place jâ-ye miyângin Fr.: position moyenne An object's celestial position as determined for a given mean equator and equinox. → mean position. |
place jâ (#) Fr.: place, lieu An area, position, or portion of space. → mean place O.E. from O.Fr. place, from M.L. placea "place, spot," from L. platea "courtyard, open space, broad street," from Gk. plateia (hodos) "broad (way)," feminine of platus "broad;" cognate with Av. pərəθu- "broad;" Skt. prthú- "broad, wide;" Lith. platus "broad;" Ger. Fladen "flat cake;" O.Ir. lethan "broad;" PIE base *plat- "to spread." Jâ "place" (from Mid.Pers. giyag "place;" O.Pers. ā-vahana- "place, village;" Av. vah- "to dwell, stay," vanhaiti "he dwells, stays;" Skt. vásati "he dwells;" Gk. aesa (nukta) "to pass (the night);" Ossetic wat "room; bed; place;" Tokharian B wäs- "to stay, wait;" PIE base ues- "to stay, live, spend the night"). |
place-value notation nemâdgân-e jâ-arezeši Fr.: notation positionnelle A mathematical notation system in which the → numerals get different values depending on their position relative to the other numerals. Same as → positional notation and → positional number system. |
virtual displacement jâbejâyi-ye virâgin Fr.: déplacement virtuel In → analytical mechanics, any infinitesimal change in the configuration of a material system, consistent with any constraints acting on the system at a given instant. If the constraints are stationary (→ scleronomous), then the actual displacement of the system, in an infinitesimal length of time dt, coincides with one of its virtual displacements. In the case of time-dependent (→ rheonomous) constraints, the actual displacement of the system does not coincide with any of the virtual ones, since the conditions imposed by the constraints vary during the time dt. → virtual; → displacement. |
Wien's displacement law qânun-e jâ-be-jâyi-ye Wien (#) Fr.: loi du déplacement de Wien The wavelength corresponding to the maximum emissive power of a black body is inversely proportional to the absolute temperature of the body: λ_{max}.T = 0.29 cm-deg. Wien's law explains why objects of different temperature emit spectra that peak at different wavelengths. Hotter objects emit most of their radiation at shorter wavelengths; hence they will appear to be bluer. Wien's law was an early attempt to describe the → blackbody radiation. The law closely approximated the true shape of the blackbody spectrum at short wavelengths, but ultimately failed because it relied solely on classical physics. It was superseded by → Planck's radiation law, which correctly describes the blackbody spectrum at all wavelengths. After the German physicist Wilhelm Wien (1864-1928), who found the law in 1896. He was awarded the 1911 Nobel Prize in physics; → displacement; → law. |