An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



Number of Results: 7 Search : wheel
Breit-Wheeler process
  فراروند ِ برایت-ویلر   
farâravand-e Breit-Wheeler

Fr.: processus Breit-Wheeler   

The production of an → electron-positron pair in the → collision of two → gamma ray → photons (γγ → e+e-). It is the → inverse process of → Dirac annihilation (e+e-→ γγ). The Breit-Wheeler process is the simplest way by which pure → light can be potentially transformed into → matter. However, as of 2014, this process has never been observed in practice because of the difficulty in preparing colliding → gamma ray beams.

Breit, G. & Wheeler, J. A. 1934, Collision of two light quanta. Phys. Rev. 46, 1087; → process.

Cartwheel Galaxy
  کهکشان ِ چرخ ِ ارابه   
kahkašân-e carx-e arrâbé

Fr.: galaxie de la roue de charette   

A galaxy with a striking ring-like feature lying about 400 million → light-years away in the → constellation  → Sculptor. The ring-like structure, over 100,000 light-years in diameter, is composed of regions of → star formation filled with very bright, → massive stars. The shape results from collision with another smaller galaxy.

Cartwheel, from cart from O.N. kartr; → wheel; → galaxy.

Kahkašân, → galaxy. Carx-e arrâbé "cartwheel," from carx, → wheel + arrâbé "cart, chariot," maybe related to Mid.Pers. ras, ray "wheel," O.Pers./Av. raθa- "wheel," Khotanese rrha- "car," Skt. ratha- "wheel," L. rota "wheel," PIE base *rotos "wheel."

Newton's color wheel
  چرخ ِ رنگ ِ نیوتن   
carx-e rang-e Newton

Fr.: disque de Newton   

The arrangement of the seven colors of the rainbow on a disk. When the disk rotates very fast, the eye cannot distinguish between individual colors and the disk is perceived as white. This apparatus demonstrates the discovery made by Newton (Opticks, 1704) that light is composed of seven colors.

Newton; → color; → wheel.

ferferé (#)

Fr.: moulin à vent   

A child's toy consisting of a wheel or leaflike curls of paper or plastic loosely attached by a pin to a stick, designed to revolve when blown by or as by the wind (

pin; → wheel.

Ferferé "pinwheel," of unknown origin.

toothed-wheel experiment
  آزمایش ِ چرخ ِ دندانه‌دار   
âzmâyeš-e carx-e dandâne-dâr

Fr.: expérience de la roue dentée   

The experiment which provided the first accurate measurement of the speed of light. The experiment, conducted by the French physicist Armand H. L. Fizeau (1819-1896) in 1849, used a rotating wheel containing 720 teeth. The function of the wheel was to cut a light beam into short pulses and to measure the time required for these pulses to travel to a distant mirror and back (17.34 km). The round-trip time for each pulse could be calculated to be about 1/18,000 sec, which yielded the value of 315,300 km/sec for the speed of light. Leon Foucault (1819-1868) improved on Fizeau's method by replacing the cogwheel with a rotating mirror. Foucault's estimate, published in 1862, was 298,000 km/s.

From tooth; M.E.; O.E. toth (cf. O.S., Dan., Swed., Du. tand, O.N. tönn, O.Fris. toth, O.H.G. zand, Ger. Zahn, Goth. tunthus), cognate with Pers. dandân, as below; → wheel; → experiment.

Âzmâyeš, → experiment; carxwheel; dandâne-dâr "toothed," from dandân "tooth," Mid.Pers. dandân; Av. dantan-; cf. Skt. dánta-; Gk. odontos; L. dens (Fr. dent); Lith. dantis, O.Ir. det, Welsh dent; PIE base *dont-/*dent- "tooth."

carx (#)

Fr.: roue   

1) A solid disk or a rigid circular ring arranged to turn around an axle passed through the center.
2) Anything like a wheel in shape or function.

M.E. whel(e), O.E. hweol, hweogol, from PIE *k(w)e-k(w)lo- "wheel, circle;" cf. Gk. kyklos "circle, wheel;" L.L. cyclus; Mod.Pers. carx "wheel;" Av. caxra- "wheel;" Skt. cakra- "wheel, circle;" Rus. koleso "wheel."

Carx "wheel," akin to wheel, as above.

Wheeler-DeWitt equation
  هموگش ِ ویلر-دویت   
hamugeš-e Wheeler-DeWitt

Fr.: équation de Wheeler-DeWitt   

In → quantum gravity, an equation that describes the → wave function of the → Universe. It is an adaptation of the → Schrodinger equation but includes the curved space attributes of → general relativity.

Named after American theoretical physicists John Archibald Wheeler (1911-2008) and Bryce Seligman DeWitt (1923-2004).