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

1) The ability to → comprehend something.
2) In logic, the sum of all the essential attributes which analysis can find in a concept or term. For example, the comprehension of the term man is rational animal; the → extension of the term man, is all men and women. Comprehension and extension are inversely proportional. The greater is the comprehension of a term, the less is its extension.

Verbal noun of → comprehend.

1) Completely or broadly covering; including a large proportion of something.
2) Having or showing extensive understanding.

From M.Fr. compréhensif, from L.L. comprehensivus, from L. comprehendere, → comprehend. comprehendo.

To press together; force into less space.

From O.Fr. compresser, from L. compressare "to press together," from comprimere "to squeeze," from → com- "together" + premere "to press;" PIE *prem-/*pres- "to strike."

Tanjidan "to squeeze, press, pull together," related to tang "tight," also "horse girth, a strap for fastening a load" (Mid.Pers. tang "tight, narrow"); cf. Skt. tanákti "draws together, contracts;" cognate with E. → tight; cp. Skt. tanákti "draws together, contracts;" M.H.G. dihte "dense, thick;" Ger. dicht "dense, tight;" O.H.G. gidigan; Ger. gediegen "genuine, solid, worthy;" PIE *tenk- "to thicken, clot; thick, solid."

Pressed into less space; condensed.

Past participle of → compress.

Air whose density is increased by being subjected to a pressure greater than atmospheric pressure.

→ compressed; → air.

The ability or quality to be reduced in volume. The coefficient of compressibility of a substance is given by c = (1/V).(δV/δp), where δV is the change in the volume resulting from a change of pressure δp, the temperature remaining constant.

Noun from → compressible.

Able to be reduced in volume. → compressible flow.

Adjective from → compress + -ible, variant of -able.

Tanjidani, tanješpazir from tanjidan, → compress, + adjective suffix -i; tanješpazir from tanješ, → compression, + pazir "receiving, admitting; having, endowed with;" → -able.

A flow in which changes of the density, induced by velocities and their fluctuations, are not negligible.

→ compressible; → flow.

The act or process of compressing; the state of being compressed.

Verbal noun from → compress.

In thermodynamics, the quantity Z = pV_m/RT, in which P is the gas pressure, V_m the molar volume, R the gas constant, and T the temperature. The compression factor is a measure of the deviation of a real gas from an ideal gas. For an ideal gas the compression factor is equal to 1.

→ compression; → facteur.

A → longitudinal wave that compresses the → medium along the direction of → propagation, such as a → sound wave. Same as → compressional wave.

→ compression; → wave.

Of or relating to → compression.

→ compression; → -al.

An → elastic wave that travels through a → medium with the particles of the medium moving in the same direction as the wave propagation. The compressional wave is the wave that is primarily used in → seismic exploration. Also called P-wave, primary wave, pressure wave.

→ compressional; → wave.

The American physicist Arthur Holly Compton (1892-1962), the Nobel Prize in Physics 1927, who made important contributions to the study of X- and cosmic rays.
→ Compton catastrophe, → Compton effect, → Compton equation, → Compton era, → Compton recoil, → Compton scattering, → Compton shift, → Compton suppression, → Compton wavelength, → Comptonization.

In a compact, steady radio-source where the density of relativistic electrons and the density of synchrotron radiation due to these electrons are very large, the radio photons should be transformed into X-ray and gamma-ray photons through inelastic Compton scatterings onto the relativistic electrons. Thus the radio photons should rapidly disappear and only gamma-ray photons should be observed. This phenomenon does not take place if the radio source is in relativistic expansion.

→ Compton; → catastrophe.

Increase in the wavelength of an → X-ray or → gamma ray  → photon when it collides a → free → electron. The photon transfers part of its energy to the electron, the electron recoils, and the photon itself is scattered at a reduced energy.

→ Compton; → effect.

Theoretical equation which gives the change in the photon wavelength due to the → Compton effect.

→ Compton; → equation.

The change of direction undergone by the electron in the → Compton effect. The scattered photon and the collided electron move in different directions from that of the incident photon.

→ Compton; → recoil.

Scattering of a → photon due to the → Compton effect.

→ Compton; → scattering.

Of the → Compton effect, the amount of increase in the wavelength of an energetic photon upon its collision with an electron.

→ Compton; → shift.