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: 12948 Search : far
gravitational contraction
  ترنگش ِ گرانشی   
terengeš-e gerâneši

Fr.: contraction gravitationnelle   

Decrease in the volume of an astronomical object under the action of a dominant, central gravitational force.

gravitational; → contraction.

gravitational encounter
  رویارویی ِ گرانشی   
ruyâruyi-ye gerâneši

Fr.: rencontre gravitationnelle   

An encounter in which two moving bodies alter each other's direction and velocity by mutual → gravitational attraction.

gravitational; → encounter.

gravitational energy
  کاروژ ِ گرانشی   
kâruž-e gerâneši

Fr.: énergie gravitationnelle   

Same as → gravitational potential energy.

gravitational; → energy.

gravitational equilibrium
  ترازمندی ِ گرانشی   
tarâzmandi-ye gerâneši (#)

Fr.: équilibre gravitationnel   

The condition in a celestial body when gravitational forces acting on each point are balanced by some outward pressure, such as radiation pressure or electron degeneracy pressure, so that no vertical motion results.

gravitational; → equilibrium.

gravitational field
  میدان ِ گرانشی   
meydân-e gerâneši (#)

Fr.: champ gravitationnel   

The region of space in which → gravitational attraction exists.

gravitational; → field.

gravitational force
  نیروی ِ گرانشی   
niru-ye gerâneši (#)

Fr.: force gravitationnelle   

The weakest of the four fundamental forces of nature. Described by → Newton's law of gravitation and subsequently by Einstein's → general relativity.

gravitational; → force.

gravitational instability
  ناپایداری ِ گرانشی   
nâpâydâri-ye gerâneši (#)

Fr.: instabilité gravitationnelle   

The process by which fluctuations in an infinite medium of size greater than a certain length scale (the Jeans length) grow by self-gravitation.

gravitational; → instability.

gravitational interaction
  اندرژیرش ِ گرانشی   
andaržireš-e gerâneši

Fr.: interaction gravitationnelle   

Mutual attraction between any two bodies that have mass.

gravitational; → interaction.

gravitational lens
  عدسی ِ گرانشی   
adasi-ye gerâneši (#)

Fr.: lentille gravitationnelle   

A concentration of matter, such as a galaxy or a cluster of galaxies, that bends light rays from a background object, resulting in production of multiple images. If the two objects and the Earth are perfectly aligned, the light from the distant object appears as a ring from Earth. This is called an Einstein Ring, since its existence was predicted by Einstein in his theory of general relativity.

gravitational; → lens.

gravitational lens equation
  هموگش ِ عدسی ِ گرانشی   
hamugeš-e adasi-ye gerâneši

Fr.: équation de lentille gravitationnelle   

The main equation of gravitational lens theory that sets a relation between the angular position of the point source and the observable position of its image.

gravitational; → lens; → equation.

gravitational lensing
  لنزش ِ گرانشی   
lenzeš-e gerâneši

Fr.: effet de lentille gravitationelle   

The act of producing or the state of a → gravitational lens.

gravitational; → lensing.

gravitational lensing time delay
  درنگ ِ زاییده‌ی ِ لنزش ِ گرانشی   
derang-e zâyide-ye lenzeš-e gerâneši

Fr.: retard dû à l'effet de lentille gravitationnelle   

The difference in light travel times along the various light paths from the source to the observer when the source image is divided into several images because of → gravitational lensing. According to the theory of → general relativity, light rays are deflected in the vicinity of massive objects. If the light source and the deflector are sufficiently well aligned with the observer, and obey some conditions on their distances (→ Einstein radius), we can observe several (generally distorted and magnified) images of the source. A property of → strong lensing is that the light travel time from the source to the observer is generally not identical for the different images. In other words, we not only see several images of one same object, but we also see this object, in each image, at different times. This means, in one image the lensed object will be observed before the other image. Given a physical model of the gravitational lens, the light travel time for each image can be computed. The expression giving the time delay has two components: a term is called → geometric delay, and the second term, known as the → Shapiro time delay. The latter is due to time dilation by the gravitational field of the lens, a direct consequence of general relativity. See also → time delay distance.

gravitational; → lensing; → time; → delay.

gravitational mass
  جرم ِ گرانشی   
jerm-e gerâneši (#)

Fr.: masse gravitationnelle   

The mass of an object measured using the effect of a gravitational field on the object.

gravitational; → mass.

gravitational potential energy
  کاروژ ِ توند ِ گرانشی   
kâruž-e tavand-e gerâneši

Fr.: énergie potentielle gravitationnelle   

1) The energy that an object possesses because of its position in a → gravitational field, especially an object near the surface of the Earth where the → gravitational acceleration can be assumed to be constant, at about 9.8 m s-2.
2) In a two body system. It is the amount of work done in bringing the mass m to the distance R from M: EP = -GMm/R, where G is the → gravitational constant.
3) For a uniform sphere. It is EP = -(3/5)GM2/R, where G is the gravitational constant and M is the mass contained in the sphere of radius R.

gravitational; → potential; → energy.

gravitational radiation
  تابش ِ گرانشی   
tâbeš-e gerâneši (#)

Fr.: rayonnement gravitationnel   

The → energy transported by → gravitational waves. Gravitational radiation is to → gravity what light is to → electromagnetism.

gravitational; → radiation.

gravitational redshift
  سرخ‌کیب ِ گرانشی   
sorxkib-e gerâneši

Fr.: décalage vers le rouge gravitationnel   

The change in the wavelength or frequency of electromagnetic radiation in a gravitational field predicted by general relativity.

gravitational; → redshift.

gravitational settling
  نیاشش ِ گرانشی   
niyâšeš-e gerâneši

Fr.: décantation par gravité   

A physical process occurring in → stellar atmospheres whereby in a very stable atmosphere → heavy elements are gravitationally pulled down preferentially. If such an atmosphere is stable for long periods of time, the → absorption lines of heavy elements may therefore become very weak. Observationally, the star seems to contain only → hydrogen and → helium. Gravitational settling takes place in the Sun at the bottom of the outer → convective zone where helium is dragged down, leading to a surface He abundant smaller than the cosmic value. It occurs also in the atmospheres of → brown dwarfs and → planets. See also → radiative levitation, → element diffusion, → thermal diffusion.

gravitational; → settling.

gravitational slingshot
  فلاخن ِ گرانشی   
falâxan-e gerâneši

Fr.: fronde gravitationnelle   

Same as → gravity assist.

gravitational; slingshot, from sling, from M.E. slyngen, from O.N. slyngva "to sling, fling" + shot, from M.E., from O.E. sc(e)ot, (ge)sceot; cf. Ger. Schoss, Geschoss.

Falâxan "sling;" from Av. fradaxšana- "sling," fradaxšanya- "sling, sling-stone;" → gravitational.

gravitational wave
  موج ِ گرانشی   
mowj-e gerâneši (#)

Fr.: ondes gravitationnelles   

A → space-time oscillation created by the motion of matter, as predicted by Einstein's → general relativity. When an object accelerates, it creates ripples in space-time, just like a boat causes ripples in a lake. Gravitational waves are extremely weak even for the most massive objects like → supermassive black holes. They had been inferred from observing a → binary pulsar in which the components slow down, due to losing energy from emitting gravitational waves. Gravitational waves were directly detected for the first time on September 14, 2015 by the → Laser Interferometer Gravitational-Wave Observatory (LIGO) (Abbott et al., 2016, Phys. Rev. Lett. 116, 061102). Since then several other events have been detected by LIGO and → Laser Interferometer Space Antenna (LISA). The Nobel Prize in physics 2017 was awarded to three physicists who had leading roles in the first detection of gravitational waves using LIGO. They were Rainer Weiss (MIT), Barry C. Barish, and Kip S. Thorne (both Caltech).
2) Not to be confounded with → gravity wave.

gravitational; → wave.

gravitational-field theory
  نگره‌ی ِ میدان ِ گرانشی   
negare-ye meydân-e gerâneši (#)

Fr.: théorie de champ gravitationnel   

A theory that treats gravity as a field rather than a force acting at a distance.

gravitational; → field.

<< < -es -iv -ti 21- A r abe abs abs acc acc acc act act ada adi adu aff age alc Alf ali all alp alt ama amp ana ang ang ann ano ant ant ape apo app aps arc Arg ari art ass ast ast ast atm ato att aur aut axi B r bac Bal Bar Bar Bay bec Ber Bet Bie bij bin bio bis bla bla blu blu bol Bor bou Bra bre bro Bug C-s cal Cam can car Car Cas cat cav cel cen cer Cha cha cha che cho cir cir cir cla clo clo clu coa coe coh col col col com com com com com com com com com con con con con con con con con con con con coo cor cor cor cos cos cos Cou cou Cra Cre cri cro cub cur cyc cyl dar dat daw de- Deb dec dec dee def deg del Den dep der det deu dew dic dif dif dil dip dir dis dis dis dis dis div dog Dop dou dra dua dus dwa dyn e-m ear ecl eco eff ein Ein elb ele ele ele ele Els emi emp ene enr env epi equ equ Eri est Euc eva evo exc exc exh exo exp exp ext ext f-n Fah fam fau fee Fer fib fil fin fir fix fle flu foc for for for fra fre fre fri fun fuz gal gal gal Gan gau GCN gen geo geo geo geo Gl glo gra gra gra gra gra gre gro GW1 hab hal han HAR haz hea hel hel Hen Her heu Hig Hil hol hop hor hou Hub Hum Hyd hyd hyd hyp hys ide ign ima imp imp inc inc ind ine inf inf inf inh INP ins ins int int int int Int int int int inv ion iri irr iso iso iso Jea Jos Jun K2 Kep key kin Kol lag lam Lan lar las lav lea leg len lev lig lim lin lin lin lis lob loc log lor low lum lun lun Lym Mac mag mag mag mag mag mai Mal mar mas mas mat max mea mea mee Men mer met met met mic mid Mil min Mir mix mod mod mol mon Mor mou mul muo mys nan nat nav nec Nep neu New New NGC nob nom non non nor not nuc nuc num Nyq obj obs obs oce oen OH omn opa ope opt opt opt orb ord Ori ort osc out ove oxy pal pan par Par par par pas pea Pen per per per per per pet pha pho pho pho phy pie Pit Pla pla pla pla ple Poi pol pol pol pol pop pos pos pow pre pre pre Pre pri pri pri pro pro pro pro pro pro Pro pub pul pyr qua qua qua qua Qui rad rad rad rad rad rad ram ran rat rea rec rec rec red ref ref reg reg rel rel rem rep res res res ret rev rho Rie rim riv rol Ros rot rul S a Sah san Sat sca Sch Sch scr sec sec sec sei sel sem sep set sha she sho sid sig sil sim sin sit sky slu sno sof sol sol sol sol sou sou spa spa spe spe spe sph spi spl spr sta sta sta sta sta ste ste sti sto str str sub sub sub sug sun sup sup sup sup sur syl syn sys tal Tay tel ten ter tex the the the thi tho thu tid tim tod top tot tra tra tra tra tri tri tro tru tur twi Typ UFO ult unc uni uni uni upg ura uti val var vec vel ver ver vig vir vis voc von wak Was wav wax wea wei whi Wie win WN6 wom X-r yel you zer zod > >>