An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

Opposite or contrary in position, direction, order, etc.
Acting in a manner opposite or contrary to that which is usual. → invert = vârun (وارون).

M.E. revers from O.Fr. revers "reverse, cross," from L. reversus, p.p. of revertere "to turn back," from → re- "back" + vertere "to turn," cognate with Pers. gard "to turn," as below.

Vârun "inverse, upside down," from vâ- "back, backward, again, re-," variant of bâz-, from Mid.Pers. abâz-, apâc-, O.Pers. apa- [pref.] "away, from;" Av. apa- [pref.] "away, from," apaš [adv.] "toward the back;" cf. Skt. ápāñc "situated behind."
Vâgard, from vâ-, → re-, + gard present stem of gardidan, gaštan "to turn, to change" (Mid.Pers. vartitan; Av. varət- "to turn, revolve;" cf. Skt. vrt- "to turn, roll," vartate "it turns round, rolls;" L. vertere "to turn;" O.H.G. werden "to become;" PIE base *wer- "to turn, bend").

A → shock front in a → supernova remnant (SNR) arising from the interaction of the → supersonic  → forward shock wave with the → interstellar medium (ISM) material. The reverse shock forms as the high pressure gas behind the forward shock wave expands and pushes back on the stellar ejecta. Reverse shock propagates into ejecta, starting from outside.

→ reverse; → shock.

Capable of returning to an original condition. → reversible process.

→ reverse + → -able.

Any physical process which can be performed in the reverse direction, the whole series of changes constituting the process being exactly reversed. → irreversible process.

→ reversible; → process.

A layer of relatively cool gas forming the lower part of the Sun's chromosphere, just above the photosphere, that gives rise to absorption lines in the Sun's spectrum.

Reversing verbal adj. of → reverse; → layer.

1a) A critical article or report.
1b) The process of going over a subject again in study in order to examine and summarize the facts.
2) To discuss a research subject in a critical review; write a critical report upon.

M.E., from O.Fr. reveue "a reviewing, review," from feminine p.p. of revoir "to see again, reexamine," from O.Fr. reveoir, from → re- + veoir, veeir "to see."

Bâzdâ, from bâz-, → re-, + dâ root of didan "to see" (Mid.Pers. ditan "to see, regard, catch sight of, contemplate, experience;" O.Pers. dī- "to see;" Av. dā(y)- "to see," didāti "sees;" cf. Skt. dhī- "to perceive, think, ponder; thought, reflection, meditation," dādhye; Gk. dedorka "have seen") + kardan "to do," → -or.

A talk that deals with a subject by examining, criticizing, and summarizing the facts.

→ review; → talk.

To alter something already written or printed, in order to make corrections, improve, or update (Dictionary.com).

M.E., from M.Fr. reviser, from L. revisere "to look at again, look back on," frequentative of revidere, from → re- "again" + videre "to see," → vision.

Bâznegaristan, from bâz- "again," → re-, + negaristan "to look, observe," → theory.

the act or work of revising. a process of revising. a revised form or version, as of a book.

Verbal noun of → revise.

1) An improvement in the condition, strength, or fortunes of someone or something.
2) A restoration to life or consciousness.
3) An instance of something becoming popular, active, or important again (OxfordDictionaries.com).

→ revive; → -al.

1a) Regain life, consciousness, or strength.
1b) Give new strength or energy to.
2a) Restore to life or consciousness (OxfordDictionaries.com).

Ultimately from L. revivere; → re-; → survive.

The act of revoking; annulment.

Verbal noun of → revoke.

1) To take back or withdraw; annul, cancel, or reverse; rescind or repeal.
2) To bring or summon back (Dictionary.com).

M.E., from O.Fr. revoquer, from L. revocare "rescind, call back," from → re- "back," + vocare "to call," from vox, → voice.

Vâvacidan, from vâ-, → re-, + vacidan "to call," → convoke.

The movement of a celestial body which is in orbit around another. It is often measured as the → orbital period.

Verbal noun of → revolve.

To move in a an orbit around another object. Compare with → rotate.

M.E. revolven, from L. revolvere "to turn, roll back," from → re- "back, again" + volvere "to roll."

Gardidan variants gaštan "to turn, to change," dialectal gel, gelidan, gellidan "to turn;" gardun "wheel; chariot;" (+ → ni-) navardidan, navard- "to twist; to fold; to stroll;" Mid.Pers. wardidan, walt- "to turn; twist;" Av. varət- "to turn, revolve;" cf. Skt. vart- "to turn, roll," vartate "it turns round, rolls;" L. vertere "to turn;" O.H.G. werden "to become;" PIE base *wert- "to turn, bend."

A dimensionless quantity that governs the conditions for hydrodynamic stability and the occurrence of turbulence in fluids. It is defined by the ratio, R, of the inertial force (ρ u²) and the viscous force (μ u / L), i.e. R = L u ρ/μ, where L is a typical dimension of the system, u is a measure of the velocities that prevail, ρ the density, and μ the kinematic viscosity. At low Reynolds numbers the flow is steady, since the viscous forces are predominant in controlling the flow. At a critical value of R, corresponding to a critical velocity, the flow becomes turbulent.

Named after Osborne Reynolds (1842-1912), a British physicist who pioneered the study of turbulent flows; → number.

Same as → red horizontal branch star.

→ red; → horizontal; → branch; → star.

The second largest satellite of Saturn, also known as Saturn V. It has a diameter of 1530 km and orbits Saturn at a mean distance of 527,040 km in 4.518 days. Rhea is composed primarily of water ice with rock making up less than 1/3 of its mass. It was discovered by Cassini in 1672.

In Gk. mythology Rhea was the sister and wife of Cronus (Saturn) and the mother of Demeter, Hades (Pluto), Hera, Hestia, Poseidon (Neptune), and Zeus (Jupiter).

A metallic chemical element; symbol Re. Atomic number 75; atomic weight 186.207; melting point about 3,180°C; boiling point about 5,625°C. Rhenium is a very dense, high-melting, silver-white metal; specific gravity 21.02 at 20°C. Of the elements, only carbon and tungsten have higher melting points and only iridium, osmium, and platinum are more dense. It was discovered by x-ray spectroscopy in 1925 by the German chemists, Walter Noddack, Ida Tacke and Otto Berg.

The name derives from L. rhenus for "the Rhine river in Germany".

A branch of physics dealing with the way matter flows and deforms.

From rheo- "flow, current, stream," from Gk. rheos "stream," cognate with Pers. rud "river," → Eridanus, + → -logy.

Ravâné, from ravân "flowing, running," pr.p. of raftan "to go, walk; to flow;" (Mid.Pers. raftan, raw-, Proto-Iranian *rab/f- "to go; to attack") + šenâsi, → -logy.