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

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

   Homepage   
   


A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

<< < R a rad rad rad rad rad rad ran rar ray rea rea rec rec red red ref reg reg rel rel rem res res res res ret rev Ric rig rin roc ROS rot Ruf Ryd > >>

Number of Results: 701
rocket
  روکت   
roket

Fr.: fusée   

A projectile driven by reaction propulsion that carries its own propellants. → missile = mušak (موشک).

From It. rocchetto "a rocket," literally "a bobbin," diminutive of rocca "a distaff," with reference to its shape.

rocket astronomy
  اخترشناسی با روکت   
axtaršenâsi bâ roket

Fr.: astronomie par fusée   

The study of celestial bodies in the wavelengths that are almost completely absorbed by the atmosphere, by using a rocket to carry instruments above 250 km to measure the searched for phenomena.

rocket; → astronomy.

rocketry
  روکت‌شناسی، روکت‌گری   
roket šenâsi, roketgari

Fr.: fuséologie   

The science of rocket design, development, and flight.

rocket + -ry a noun suffix.

Roket šenâsi, from roket, → rocket, + šenâsi, → -logy; roketgari with suffix -gari, from -gar, → -or.

rockoon
  روکلون   
roklon

Fr.: fusée-sonde lancée à partir d'un ballon   

A rocket launched from a balloon at a pre-determined height and fired by a ground-controlled radio relay when some particular event, e.g. a solar flare, occurs.

From rocket + balloon.

From roket + lon, → ballon astronomy.

Roemer's measurement
  اندازه‌گیری ِ رؤمر   
andâzegiri-ye Rømer

Fr.: mesure de Rømer   

The first successful measurement of the → speed of light carried out by the Danish astronomer Ole Rømer in 1675 at Paris Observatory. Astronomers knew that the mean period of revolution for Jupiter's innermost satellite → Io (Jupiter I) was 42.5 hours. During this period Io was sometimes eclipsed by Jupiter. Astronomers expected that if Io was visible at some time it must be visible 42.5 hours later. But Ole Rømer discovered that there were many irregularities in Io's orbital period. Sometimes Io appeared too early and other times too late in relation to the expected times. The irregularities repeated themselves precisely at a one-year interval, which meant that they must be connected to the Earth's rotation around the Sun. Rømer attributed this difference in time to the additional distance the light from Io had to travel at different times, and used this information to calculate the speed of light. He found that it takes light 22 minutes to traverse the Earth's orbital diameter; the correct figure was later determined to be 16 minutes and 40 seconds. Rømer was able to measure the speed of light to be 230,000 km s-1. Although this figure was very close to the currently accepted value of 300,000 km s-1, it was rejected by the scientific community of the time, who assumed it to be much too high a figure.

Ole Rømer (1664-1710); → measurement.

roentgen
  رونتگن   
rontgen (#)

Fr.: roentgen   

A unit of radiation exposure defined as a charge release rate of 258 micro-coulombs per kilogram of air.

Named after the German physicist Wilhelm Konrad Röntgen (1845-1923), one of the early investigators of radioactivity.

roentgenium
  رونتگنیوم   
rontgeniom (#)

Fr.: roentgenium   

An artificially produced radioactive chemical element; symbol Rg. Atomic number 111; mass number of most stable isotope 272; melting point, boiling point, specific gravity, and valence unknown.

Named after the German physicist Wilhelm Konrad Röntgen (1845-1923), one of the early investigators of radioactivity.

rogue
  ولگرد   
velgard (#)

Fr.: vagabond   

A vagabond or tramp. A dishonest or unprincipled person.

Perhaps short for obsolete roger "begging vagabond."

Velgard "vagabond, roamer, tramp."

rogue planet
  سیاره‌ی ِ ولگرد   
sayyâre-ye velgard

Fr.: planète vagabonde   

Same as → free-floating object.

rogue; → planet.

roll cloud
  ابر ِ لوله‌وار   
abr-e lule-vâr

Fr.: nuage en rouleau   

A low, horizontal, tube-shaped, and relatively rare type of → arcus cloud.

M.E. scroll, inscribed scroll, register, cylindrical object < OF ro(u)lle M.E. rolle, from O.Fr. roule, rolle, from M.L. rotulus "a roll of paper," from L. rotula "small wheel," diminutive of rota "wheel;" → cloud.

Abr, → cloud; lule-vâr "tube like," from lulé "tube, pipe," related to lulidan "to roll, rotate; to stir, vibrate" + -vâr suffix of resemblance.

Rolle's theorem
  فربین ِ رول   
farbin-e Rolle

Fr.: théorème de Rolle   

If a function f(x) is → continuous on an interval [a,b] and is → differentiable at all points within this interval, and vanishes at the end points x = a and x = b, that is f(a) = f(b) = 0, then inside [a,b] there exists at least one point x = c, a < c < b, at which the derivative f'(x) vanishes.

Named after Michel Rolle (1652-1719), a French mathematician; → theorem.

Roman calendar
  گاهشمار ِ رومی   
gâhšomâr-e Rumi

Fr.: calendrier romain   

Any of several → lunar calendars used by Romans before the advent of the → Julian calendar in 46 B.C. The original Roman calendar, which had 10 months and 304 days, went back to the Greek calendar, although Romulas, the ruler of Rome, is given credit for starting the Roman calendar. Originally, the Roman calendar started the year in March with the → vernal equinox. The Roman calendar went through several changes from 800 B.C. to the Julian calendar. The 800 B.C. calendar had 10 months and a winter period, with a year of 304 days. In this calendar, the first month, March, was followed by Aprilis, Maius, Junius, Quintilis, Sextilis, September, October, November, December, and Winter. The months starting with and following Quintilis all used the Latin numbers for names. Finally, for political reasons, the Romans made a change around 150 B.C. when they started using January as the beginning of their calendar year. Around 700 B.C. the 304 day calendar was expanded to 355 days by adding the months of February and January to the end of the year. Later in 450 B.C., January was moved in front of February. Finally, in 150 B.C. the Romans began to use January as the beginning of the calendar year. This calendar was replaced by the Julian calendar in 46 B.C.

From L. Romanus "of Rome, Roman," from Roma "Rome," of uncertain origin.

Roman numeral system
  راژمان ِ عددهای ِ رومی   
râžmân-e adadhâ-ye Rumi

Fr.: numération romaine   

A → number system in which letters represent numbers, still used occasionally today. The cardinal numbers are expressed by the following seven letters: I (1), V (5), X (10), L (50), C (100), D (500), and M (1,000). If a numeral with smaller value is written on right of greater value then smaller value is added to the greater one. If it is preceded by one of lower value, the smaller numeral is subtracted from the greater. Thus VI = 6 (V + I), but IV = 4 (V - I). Other examples are XC (90), CL (150), XXII (22), XCVII (97), CCCXCV (395). If symbol is repeated then its value is added. The symbols I, X, C and M can be repeated maximum 3 times. A dash line over a numeral multiplies the value by 1,000. For example V- = 5000, X- = 10,000, C- = 100,000, and DLIX- = 559,000.

numeral; → system.

rook
  زاغ   
zâq (#)

Fr.: corbeau freux   

A common Old World gregarious crow (Corvus frugilegus).

M.E., from O.E. hrôc; akin to O.H.G. hruoch "crow."

Zâq, from Mid.Pers. zâγ "crow."

root
  ریشه   
rišé (#)

Fr.: racine   

1) Math.: A quantity that, when multiplied by itself a certain number of times, produces a given quantity. For example, since 3 × 3 × 3 × 3 = 81, 3 is a fourth root of 81.
2) Math.: A solution to an equation f(x) = 0. We say that x0 is a root or zero of a → polynomial if f(x0) = 0. For example, the roots of the equation x2 - 9 = 0 are +3 and -3.
3) In → graph theory, a special → vertex that turns a → tree into a → rooted tree or a graph into a → rooted graph.

From M.E., from O.E. rot, from O.N. rot "root;" cf. O.H.G. wurz "plant, herb;" Ger. Wurz; cognate with L. radix, radius "staff;" Gk. rhiza "root;" Albanian rrânzë "root;" PIE base *u(e)rad- "twig, root."

Rišé "root" (dialectal Tabari rexa; Kurd. regez, riše), from Mid.Pers. rêšak "root," maybe ultimately related to PIE *u(e)rad-, as above, although the Skt. offshoot is absent.

root mean square (rms)
  ریشه‌ی ِ چاروشی ِ میانگین، ~ ِ دوم ِ ~   
riše-ye câruši-ye miyângin, ~ dovom-e ~

Fr.: valeur quadratique moyenne   

The square root of the arithmetic mean of the squares of the numbers in a given set.

root; → mean; → square.

root-mean-square error
  ایرنگ ِ ریشه‌ی ِ چاروشی ِ میانگین، ~ ~ ِ دوم ِ ~   
irang-e riše-ye câruši-ye miyângin, ~ ~ dovom-e ~

Fr.:   

The square root of the second moment corresponding to the frequency function of a random variable.

root; → mean; → square; → error.

root-mean-square value
  ارزش ِ ریشه‌ی ِ چاروشی ِ میانگین   
arzeš-e riše-ye câruši-ye miyângin

Fr.: écart quadratique moyen, écart type   

Statistics: The square root of the arithmetic mean of the squares of the deviation of observed values from their arithmetic mean.

root; → mean; → square; → deviation.

rooted graph
  نگاره‌ی ِ ریشه‌دار   
negâre-ye rišedâr

Fr.: graphe raciné   

In → graph theory, a → graph that has one of its → vertices, called the → root, distinguished from the others.

root; → graph.

rooted tree
  درخت ِ ریشه‌دار   
deraxt-e rišedâr

Fr.: arbre raciné   

In → graph theory, a → tree in which one → vertex is distinguished from the other vertices and is called the root.

root; → tree.

<< < R a rad rad rad rad rad rad ran rar ray rea rea rec rec red red ref reg reg rel rel rem res res res res ret rev Ric rig rin roc ROS rot Ruf Ryd > >>