Fr.: énergie d'activation
Chemistry: The minimum amount of energy that is required to activate → atoms or → molecules to a condition in which they can undergo a → chemical reaction. Most reactions involving neutral molecules cannot take place at all until they have acquired the energy needed to stretch, bend, or otherwise distort one or more → bonds. In most cases, the activation energy is supplied by → thermal energy.
1) A broad glowing arc of radiance, sometimes seen high in the
western sky at → twilight,
caused by the → scattering effect of
→ fine dust particles
suspended in the → upper atmosphere.
Fr.: énergie alternative
Energy from a source other than the conventional fossil fuel sources.
Fr.: ambre gris
A wax-like, ash-colored, strongly scent substance present in the intestines of → whales and found in seas or cast ashore. Used in perfumery.
Anbar "ambergris," from Mid.Pers. ambar.
angle of emergence
Fr.: angle d'émergence
The angle of the light coming out of a medium. For a medium with parallel sides (such as a glass slab) it is equal to the angle of incidence.
angular kinetic energy
kâruž-e jonbeši-ye zâviye-yi
Fr.: énergie cinétique angulaier
Same as → rotational energy.
kâruž-e bandeš, ~ hamgiri
Fr.: énergie de liaison
1) Of a gravitational system, the difference
in energies between the hypothetical state where all bodies of
the system are infinitely separated from each other and the actual bound state.
black hole merger
Fr.: fusion de trous noirs
The collision of two → black holes in a → binary black hole system once they come so close that they cannot escape each other's gravity. They will merge in an extremely violent event to become one more massive black hole. The merger would produce tremendous energy and send massive ripples, called → gravitational waves, through the → space-time fabric of the Universe. Such an event (called GW150914) was first detected by the → Laser Interferometer Gravitational-Wave Observatory (LIGO) on September 14, 2015. The initial black hole masses were 36 and 29 Msun which gave a final black hole mass of 62 Msun, with 3 Msun radiated in gravitational waves. The event happened at a distance of 1.3 billion → light-years from Earth (Abbott et al., 2016, Phys. Rev. Lett. 116, 061102). Black hole merger is preceded by → inspiral and followed by → ringdown.
Fr.: supergéante bleue
characteristic thermal energy
kâruž-e garmâyi-ye sereštâri
Fr.: énergie thermique caractéristique
Fr.: énergie de cohésion
The energy associated with the chemical bonding of atoms in a solid.
conservation of energy
Fr.: conservation d'énergie
conservation of mass and energy
patâyeš-e jerm o kâruž
Fr.: conservation de masse et d'énergie
1) General: To tend to meet in a point; incline toward each other.
From L.L. convergere "to incline together" from → com- "together" + vergere "to bend."
Hamgerâyi, verbal noun from hamgerâyidan, → converge.
Coming together, as a light beam after passing through a convex lens which brings the beam into the focus.
Verbal ddj. from → converge.
âyene-ye hamgerâ (#)
Fr.: miroir convergent
A concave mirror that reflects a parallel beam into a convergent beam.
Fr.: hypergéante froide
A highly unstable, → very massive star lying just below the empirical upper luminosity boundary in the → H-R diagram (→ Humphreys-Davidson limit) with spectral types ranging from late A to M. Cool hypergiants very likely represent a very short-lived evolutionary stage, and are distinguished by their high → mass loss rates. Many of them also show photometric and spectroscopic variability, and some have large → infrared excesses and extensive circumstellar ejecta. The evolutionary state of most of these stars is not known but they are all → post-main-sequence stars (Humphreys, 2008, IAUS 250).
cosmic energy equation
hamugeš-e kâruž-e keyhâni
Fr.: équation de l'énergie cosmique
Same as the → Layzer-Irvine equation.
Fr.: énergie coulombienne
The → potential energy from which derives the repulsive electrostatic force between two → charged particles. For example, the Coulomb energy between two protons is e2/r ~ 0.5 MeV, which is small compared with the average → binding energy per particle (~ 8 Mev). However the Coulomb repulsion becomes important for heavy nuclei. The total Coulomb energy of a nucleus is given by: (3/5) Z(Z - 1)e2/R, where Z is the → atomic number, e the charge, and R the nuclear radius. Since R ∝ A1/3 and Z is roughly proportional to A, the Coulomb energy is roughly proportional to A5/3. On the other hand, the total binding energy is proportional to A, which means that the relative importance of the repulsive electrostatic energy increases with increasing mass number as A2/3.