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: 3079 Search : on
phlogiston theory
  نگره‌ی ِ فلوژیستون   
negare-ye fložiston

Fr.: phlogistique   

An obsolete theory of combustion in which all flammable objects were supposed to contain a substance called → phlogiston, which was released when the object burned. The existence of this hypothetical substance was proposed in 1669 by Johann Becher, who called it terra pinguis "fat earth." For example, as wood burns it releases phlogiston into the air, leaving ash behind. Ash was therefore wood minus phlogiston. In the early 18th century Georg Stahl renamed the substance phlogiston. The theory was disproved by Antoine Lavoisier in 1783, who proved the principle of conservation of mass, refuted the phlogiston theory and proposed the oxygen theory of burning.

phlogiston; → theory.

phone
  آوا   
âvâ (#)

Fr.: son   

A speech sound considered as a physical event without regard to its place in the sound system of a language.

From Gk. phone "voice, sound," phonein "to speak;" cf. L. fama "talk, reputation, fame."

Âva "voice, sound," related to âvâz "voice, sound, song" (both prefixed forms), bâng "voice, sound, clamour" (Mid.Pers. vâng), vâžé "word," variants vâj-, vâk-, vâ-, vâz-, vât-; Av. vacah- "word," vaocanghê "to decalre" (by means of speech), from vac- "to speak, say;" cf. Skt. vakti "speaks, says," vacas- "word;" Gk. epos "word;" L. vox "voice;" PIE base *wek- "to speak."

phoneme
  واج   
vâj (#)

Fr.: phonème   

The smallest phonetic unit in a language that can distinguish one word from another.

From Fr. phonème, from Gk. phonema "speech sound, utterance," from phonein "to sound," → phone.

Vâj "voice," variant of vâž, vâz-, âvâz etc., → phone.

phonetics
  آواییک   
âvâyik (#)

Fr.: phonétique   

A branch of linguistics dealing with the analysis, description, and classification of speech sounds. More specifically, phonetics deals with the physical production of → phonemes regardless of language, while → phonology studies how those sounds are put together to create meaningful words in a particular language.

From phonetic, from N.L. phoneticus, from Gk. phonetikos "vocal," from phonet(os) "utterable," verbal adj. of phonein "to speak clearly, utter," from → phone + -ikos, → -ics.

&ACIRC;vâyik, from âvâ, → phone, + -ik, → -ics.

phono-
  آوا-   
âvâ- (#)

Fr.: phono-   

A combining form meaning "sound, voice," used in the formation of compound words. Also phon-, especially before a vowel.

From Gk. phon-, phono-, form → phone "voice, sound, speech"

phonology
  آواشناسی   
âvâšnâsi (#)

Fr.: phonologie   

A branch of linguistics that studies the rules in any given language that govern how → phonemes are combined to create meaningful words. Phonology and → phonetics study two different aspects of sound, but the concepts are dependent on each other in the creation of language.

phono-; → -logy.

phonon
  فونون   
fonon (#)

Fr.: phonon   

A quantum of vibrational or acoustic energy in a crystal lattice, being the analog of a photon of electromagnetic energy.

phono- + → -on.

photoabsorption
  شید-درشم   
šid-daršam

Fr.: photoabsorption   

A situation in which all of the energy of a photon is transferred to an atom, molecule, or nucleus.

photo- + → absorption.

photodesorption
  شید-واشم   
šid-vâšam

Fr.: photodésorption   

Th desorption of surface substances by ultraviolet radiation.

photo-; → desorption.

photodisintegration
  شید-واپاشی، نور-واپاشی   
šidvâpâši, nurvâpâši

Fr.: photodésintégration   

The process by which atomic nuclei are broken apart into their constituent protons and neutrons by the impact of high energy gamma photons. Photodisintegration takes place during the core collapse phase of a → Type II supernova explosion.

photo- + → disintegration.

photodissociation
  شید-واهزش، نور-واهزش   
šid-vâhazeš, nur-vâhazeš

Fr.: photodissociation   

The → dissociation of a → chemical compound by → radiation  → energy.

Verbal noun of → photodissociate; → -tion.

photodissociation region (PDR)
  ناحیه‌ی ِ شید-واهزش، ~ نور-واهزش   
nâhiye-ye šid-vâhazeš, ~ nur-vâhazeš

Fr.: région de photodissociation   

A neutral region at the boundary of a → molecular cloud created by the penetration of → far ultraviolet (FUV) radiation from associated stars. The FUV radiation (6 eV ≤ hν ≤ 13.6 eV) dissociates the molecules and heats the gas and dust. A warm, atomic → H I region is thus created and the chemistry and thermal balance of the region are determined by the penetrating FUV photons. The progressive absorption of FUV photons leads to the occurrence of transitions between atomic and molecular phases, such as H I/H2 and C II/C I/CO transitions. By extension, any neutral region where the physics is controlled by FUV photons can be called a PDR, as it is the case for → diffuse interstellar clouds or the edge of → circumstellar disks. The PDR concept was first studied by A. G. G. M. Tielens and D. Hollenbach (1985, ApJ 291, 722).

photodissociation + → region.

photoelectron
  شید-الکترون، نور-الکترون   
šid-elektron, nur-elektron

Fr.: photoélectron   

An electron emitted from an atom or molecule by an incident photon in the → photoelectric effect.

photo-; + → electron.

photoevaporation
  شید-بخارش، نور-بخارش   
šidboxâreš, nurboxâreš

Fr.: photoévaporation   

A process going on in a molecular cloud surface whereby the surface material ionized by ultraviolet photons of neighboring stars is dissipated.

photo- + → evaporation.

photoexcitation
  شید-بر‌انگیزش   
šid-barangizeš

Fr.: photoexcitation   

The mechanism of raising an electron to higher energies by photon absorption, when the energy of the photon is too low to cause photoionization.

photo- + → excitation.

photoionization
  شید-یونش، نور-یونش   
šid-yoneš, nur-yoneš

Fr.: photoionisation   

The physical process in which an incident high-energy photon ejects one or more electrons from an atom, ion, or molecule.

photo- + → ionization.

photoionize
  شید-یونیدن، نور-یونیدن   
šid-yonidan, nur-yonidan

Fr.: photoioniser   

To cause, or to undergo → photoionization.

photo-; → ionize.

photoionized
  شید-یونیده، نور-یونیده   
šid-yonidé, nur-yonidé

Fr.: photoionisé   

Subject to, or produced by → photoionization.

photo-; → ionized.

photometric calibration
  کبیزش ِ شید-سنجیک، ~ سنور-سنجیک   
kabizeš-e šidsanjik, ~ nursanjik

Fr.: calibration photométrique   

A calibration which converts the measured relative magnitudes into an absolute photometry.

photometric + → calibration.

photon
  فوتون   
foton (#)

Fr.: photon   

The → quantum of the → electromagnetic field, which mediates the interaction between charged particles. It is the mass-less → boson with zero → electric charge, which propagates with the → speed of light in vacuum. The energy of a photon is connected to its → frequency ν, through the formula E = hν, where h is → Planck's constant.

From phot-, variant of → photo- before a vowel + → -on a suffix used in the names of subatomic particles (gluon; meson; neutron), quanta (photon, graviton), and other minimal entities or components. The term photon was coined by Gilbert N. Lewis in 1926 in a letter to the editor of Nature magazine (Vol. 118, Part 2, December 18, page 874).

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