1) Physics: Relating to the → relativity theory.
Fr.: aberration relativiste
The aberration of light for an object moving with
→ relativistic speed. In contrast to the classical case,
the → Lorentz transformation between the
→ rest frame of the observer and that of the object
must be used. Relativistic aberration is expressed by the equation:
cos φ' = (cos φ -
relativistic Doppler effect
oskar-e Doppler-e bâzânigimand
Fr.: effet Doppler relativiste
The Doppler effect when the relative motion of the source and the observer is comparable to the speed of light. In that case the classical Doppler formula should be corrected for effects of the special theory of relativity (Lorentz transformation).
Fr.: effet relativiste
Fr.: masse relativiste
In → special relativity, the mass that is assigned to a body in motion. Einstein demonstrated that the velocity of the observer has an effect on the way inertial mass is measured. The relativistic mass is expressed by mt = m0 / [1 - (v/c)2]1/2, where m0 is the → rest mass, v is the velocity, and c the → velocity of light. The experimental evidence for this phenomenon is observed in the mass of high-speed electrons accelerated by magnetic fields. This formula shows that it is impossible for a mass to be accelerated to the velocity of light in a vacuum.
Fr.: particule relativiste
A particle which has a speed comparable to the velocity of light.
Fr.: précession relativiste
A → general relativistic phenomenon in which the line joining the → apsides of an orbit gradually rotates in a → prograde direction. Also called the → orbital precession and → perihelion precession. Although the general relativistic precession of Mercury's orbit is extremely small, the similar precession observed in the orbit of the → binary pulsar PSR B1913+16 amounts to 4.23 degrees per year, i.e. 36,000 times greater than the → advance of perihelion of Mercury.
relativistic quantum mechanics
kuântom mekânik-e bâzânigimand
Fr.: mécanique quantique relativiste
A quantum theory that incorporates special relativity, for example, → quantum electrodynamics.
sorx kib-e bâzânigimand
Fr.: décalage vers le rouge relativiste
Fr.: vitesse relativiste
Same as → relativistic velocity.
relativistic spin precession
pišâyân-e âse-ye carxeš-e bâzânigi-mand
Fr.: précession de l'axe de rotation relativiste
The change in the direction of the → rotation axis of a → pulsar in a → binary pulsar. In such a system, → geodetic precession leads to a relativistic → spin-orbit coupling, analogous of → spin-orbit coupling in atomic physics. In consequence, the pulsar spin precesses about the total → angular momentum, changing the relative → orientation of the pulsar toward Earth (Damour & Ruffini, 1974). As a result, the angle between the pulsar → rotation axis and our → line of sight changes with time, so that different portions of the emission beam can be observed leading to changes in the measured pulse profile. In extreme cases, the precession may even move the beam out of our line of sight and the pulsar may disappear as predicted for PSR 1913+16 for the year 2025.
Fr.: vitesse relativiste
The velocity of a body when it is a significant fraction of the → speed of light.
relativity of simultaneity
Fr.: relatitivité de simultanéité
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.
Fr.: théorie de la relativité
The → theory of relativity.
To regard as or make one thing relative to something else.
Fr.: relaxer, se relaxer
To lessen the force, strength or intensity of something.
m M.E., from O.Fr. relaxer from L. relaxare "relax, loosen, open," from → re- "back" + laxare "loosen," from laxus "loose."
Vâhelidan, from vâ-, → re-, + helidan, heštan "to place, put" from Mid.Pers. hištan, hilidan "to let, set, leave, abandon;" Parthian Mid.Pers. hyrz; O.Pers. hard- "to send forth," ava.hard- "to abandon;" Av. harəz- "to discharge, send out; to filter," hərəzaiti "releases, shoots;" cf. Skt. srj- "to let go or fly, throw, cast, emit, put forth;" Pali sajati "to let loose, send forth."
1) The evolution of the properties of a physical system which has
been disturbed and which regains its equilibrium condition
once the disturbing action has ceased. Relaxation is the response of the
system to the perturbation. The time required by the system to regain
its condition of minimum energy is called the
→ relaxation time.
Verbal noun of → relax.
Fr.: temps de relaxation
The characteristic length of time that is required for a system undergoing → relaxation to move to its equilibrium state. If the system follows an exponential law G = G0 exp(-t / τ), the relaxation time is the time required for G to obtain the fraction 1/e of its initial value G0.