An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 8 Search : stable
metastable state
  حالت ِ متاپایدار   
hâlat-e matâpâydâr

Fr.: état métastable   

An excited state in an atom, which is at the origin of the spectral lines called → forbidden lines. The time duration of the excited state being relatively long, under laboratory conditions the atom cannot pass directly to the ground state by emitting radiation. In the extremely rarefied interstellar medium, however, such highly improbable transitions do occur.

meta-; → stable; → state.

stable
  پایدار   
pâydâr (#)

Fr.: stable   

Physics: 1) Having the ability to react to a disturbing force by maintaining or regaining position or condition.
2) Incapable of becoming a different isotope or element by radioactive decay.

M.E., from O.Fr. estable, from L. stabilis "firm, steadfast," literally "able to stand," from stem of stare "to stand;" cognate with Pers. istâdan "to stand" (Mid.Pers. êstâtan; O.Pers./Av. sta- "to stand, stand still; set;" Av. hištaiti; cf. Skt. sthâ- "to stand;" Gk. histemi "put, place, weigh," stasis "a standing still;" L. stare "to stand;" Lith. statau "place;" Goth. standan; PIE base *sta- "to stand").

Pâydâr "stable, firm" literally "having feet," from pâ(y) "foot; step" (Mid.Pers. pâd, pây; Av. pad- "foot;" cf. Skt. pat; Gk. pos, genitive podos; L. pes, genitive pedis; P.Gmc. *fot; E. foot; Ger. Fuss; Fr. pied; PIE *pod-/*ped-) + dâr present stem of dâštan "to have, hold, maintain, possess" (Mid.Pers. dâštan; O.Pers./Av. root dar- "to hold, keep back, maintain, keep in mind;" cf. Skt. dhr-, dharma- "law;" Gk. thronos "elevated seat, throne;" L. firmus "firm, stable;" Lith. daryti "to make;" PIE *dher- "to hold, support").

stable equilibrium
  ترازمندی ِ پایدار   
tarâzmandi-ye pâydâr (#)

Fr.: équilibre stable   

An equilibrium state of a system in which if a small perturbation away from equilibrium is applied, the system will return to its equilibrium state. An example is a pendulum hanging straight down. If it is pushed slightly, it will experience a force back toward the equilibrium position. It may oscillate around the equilibrium position for a while, but it will finally regain its equilibrium position. → unstable equilibrium.

stable; → equilibrium.

stable nuclide
  هسته‌وار ِ پایدار   
hastevâr-e pâydâr

Fr.: nucléide stable   

A nuclide that is not → radioactive and therefore does not spontaneously undergo → radioactive decay.

stable; → nuclide.

testable
  آزمون‌پذیر   
âzmunpazir (#)

Fr.: testable   

The quality of a claim, hypothesis, or theory that can be verified by tests or experiments. See also → falsifiable.

test; → -able.

unstable
  ناپایدار   
nâpâydâr (#)

Fr.: instable   

Not → stable, as in → unstable atom, → unstable equilibrium.

un-; → stable.

unstable atom
  اتم ِ ناپایدار   
atom-e nâpâydâr (#)

Fr.: atome instable   

An atom whose nuclei → decay by → radioactivity.

unstable; → atom.

unstable equilibrium
  ترازمندی ِ ناپایدار   
tarâzmandi-ye nâpâydâr

Fr.: équilibre instable   

An equilibrium state of a system in which if a small perturbation away from equilibrium is applied, the system will move farther away from equilibrium state. For example, mechanical equilibrium in which the potential energy is a maximum, as a sphere placed on top of a hill. Mathematically, if the second derivative of the energy with respect to the coordinate of interest is negative, the system is in an unstable equilibrium. → stable equilibrium.

unstable; → equilibrium.