An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 474 Search : pH
phase angle
  زاویه‌ی ِ فاز   
zâviye-ye fâz (#)

Fr.: angle de phase   

1) Physics: Of a → periodic wave, the number of suitable units of angular measure between a point on the wave and a reference point.
2) Astro.: For an object in the solar system, the angle "Sun-object-Earth" that is, the angle between the Sun and the observer as seen from the given object. It is 0° when the object is fully illuminated, 90° when the object is half-illuminated (like the Moon at first quarter and last quarter), and 180° when the object is between Earth and the Sun.
3) More generally, the angle between star light incident onto a related revolving object and the light reflected from the object to the observer (Earth).

phase; → angle.

phase curve
  خم ِ فاز   
xam-e fâz

Fr.: courbe de phase   

1) Astro.: A curve describing the → brightness of a reflecting → natural satellite as a function of its → phase angle.
2) Math.: A plot of the solution to a set of equations of motion in a phase space as a function of time.

phase; → curve.

phase delay
  درنگ ِ فاز   
derang-e fâz

Fr.: délai de phase   

The ratio of the phase shift of a sinusoidal signal in transmission through a system to the frequency of the signal.

phase; → delay.

phase diagram
  نمودار ِ فاز   
nemudâr-e fâz

Fr.: diagramme de phases   

A graph showing the equilibrium relationships between phases (such as vapor-liquid, liquid-solid) of a chemical compound, mixture of compounds, or solution.

phase; → diagram.

phase difference
  دگرسانی ِ فاز   
degarsâni-ye fâz

Fr.: différence de phase   

The difference of phase (usually expressed as a time or an angle) between two periodic quantities which vary sinusoidally and have the same frequency.

phase; → difference.

phase equilibrium
  ترازمندی ِ فاز   
tarâzmandi-ye fâz

Fr.: équilibre de phases   

The condition of temperature and pressure under which different phases (e.g. gas, liquid, and solid) of a substance coexist.

phase; → equilibrium.

phase function
  کریای ِ فاز   
karyâ-ye fâz

Fr.: fonction de phase   

The variation in brightness of a target as the phase angle (the angle between Sun and observer as seen from the target) varies between 0° and 180°. The directional distribution of reflected (or scattered) radiation. The phase angle is the supplement of the scattering angle (the angle between the incident ray and the emerging ray); in other words, the sum of the phase angle and the scattering angle is always 180° (Ellis et al., 2007, Planetary Ring Systems, Springer).

phase; → function.

phase lag
  دگرسانی ِ فاز   
degarsâni-ye fâz

Fr.: différence de phase   

1) General: Same as → phase difference.
2) Cepheids: The observed phase difference between luminosity and velocity in classical (radially pulsating) → Cepheids. On the basis of adiabatic pulsation theory, one would expect the maximum luminosity to occur when the radius of the star is minimal. This means that the maximum outward velocity would be one quarter period out of phase with the maximum velocity. However, in the observations the maximum luminosity and maximum outward velocity are nearly in phase. This effect is due to the → kappa mechanism which is responsible for driving the → pulsations. The pulsations in Cepheids are excited by the helium → partial ionization zone, He+↔ He++, which is located below the He ↔ He+ and H ↔ H+ zones. These latter two regions are too shallow to contribute significantly to the driving of the fundamental modes of Cepheids; so their only effect is to introduce a phase shift.

phase; lag, possibly from a Scandinavian source; cf. Norw. lagga "go slowly."

Degarsâni, → difference; fâzphase.

phase lock
fâz bast

Fr.: blocage de phase   

In electronics, a technique of adjusting the phase of an oscillator signal so that it will follow the phase of a reference signal.

phase; lock, from O.E. loc "bolt, fastening, enclosure;" cf. O.N. lok "fastening, lock," Goth. usluks "opening," O.H.G. loh "dungeon," Ger. Loch "opening, hole," Du. luck "shutter, trapdoor."

Fâz, → phase; bast "fastening, lock," from bastan, from Mid.Pers. bastan/vastan "to bind, shut," Av./O.Pers. band- "to bind, fetter," banda- "band, tie," Skt. bandh- "to bind, tie, fasten," PIE *bhendh- "to bind," cf. Ger. binden, E. bind, → band.

phase modulation
  دگر‌آهنگش ِ فاز   
degarâhangeš-e fâz (#)

Fr.: modulation de phase   

Modulation in which the phase angle of a sine-wave carrier is caused to depart from the carrier angle by an amount proportional to the instantaneous magnitude of the modulating wave.

phase; → modulation.

phase reversal
  واگردانی ِ فاز، وارونش ِ ~   
vâgardâni-ye fâz, vâruneš-e ~

Fr.: inversion de phase   

An angular shift in phase by 180°.

phase; → reversal.

phase shift
  کیب ِ فاز   
kib-e fâz

Fr.: décalage de phase   

Any change in the phase of a periodic quantity or in the phase difference between two or more periodic quantities.

phase; → shift.

phase space
  فضای ِ فاز   
fazâ-ye fâz

Fr.: espace des phases   

Of a dynamical system, a six-dimensional space consisting of the set of values that the position and velocity can take together (x, y, z, vx, vy, vz). → velocity space.

phase; → space.

phase transfer function (PTF)
  کریای ِ تراوژ ِ فاز   
karyâ-ye tarâvaž-e fâz

Fr.: fonction de transfert de phase   

A measure of the relative phase in the image as function of frequency. It is the phase component of the → optical transfer function. A relative phase change of 180°, for example, results in an image with the black and white areas reversed.

phase; → transfer; → function.

phase transition
  گذرش ِ فاز   
gozareš-e fâz

Fr.: transition de phase   

The changing of a substance from one phase to another, by → freezing, → melting, → boiling, → condensation, or → sublimation. Also known as phase transformation. A well known phase transition is the transition from → water to → ice. Phase transitions are often associated with → symmetry breaking. In water there is a complete symmetry under rotations with no preferred direction. Ice has a crystal structure, in which certain orientations in space are preferred. Therefore, in transition from water to ice the continuous rotational symmetry is lost.

phase; → transition.

phase velocity
  تندای ِ فاز   
tondâ-ye fâz

Fr.: vitesse de phase   

The speed at which any fixed phase (individual wave) in a → wave packet travels. It is expressed as vph = ω/k, where ω is the → angular frequency and k the → wave number. See also the → group velocity.

phase; → velocity.

phases of the Moon
  سیماهای ِ مانگ   
simâhâ-ye Mâng

Fr.: phases de la lune   

Lunar phase.

phase; → Moon.

phases of Venus
  سیماهای ِ ناهید   
simâhâ-ye Nâhid

Fr.: phases de Vénus   

The gradual variation of the apparent shape of → Venus between a small, full → disk and a larger → crescent. The first telescopic observation of the phases of Venus by Galileo (1610) proved the → Ptolemaic system could not be correct. The reason is that with the → geocentric system the phases of Venus would be impossible. More specifically, in that model Venus lies always between Earth and Sun. Hence its fully bright surface would always be toward the Sun; so Venus could not be seen in full phase from Earth. Only slim crescents would be possible. On the other hand, this phenomenon could not prove the → heliocentric system, because it could equally be explained with the → Tychonic model.

phase; → Venus.


Fr.: phénologie   

The study of the biological recurring phenomena in plants and animals (such as blossoming, hibernation, reproduction, and migration) and of their relation to changes in season and climate.

From L. phaeno-, from Gk. phaino-, from phainein "bring to light, cause to appear, show," from PIE root *bha- "to shine" + → -logy.

Zistcarxe-šenâsi, literally study of "life cycle," from zistcarxe "life cycle," from zist, → bio-, + carxe, → cycle, + -šenâsi, → -logy.

padidé (#)

Fr.: phénomène   

1) An occurrence, circumstance, or fact, in matter or spirit, which can be perceived by human senses. → physical phenomenon.
2) Philosophy: For Kant, a thing as it is apprehended by the human senses as distinguished from a noumenon, or thing-in-itself.

From L.L. phænomenon, from Gk. phainomenon "that which appears or is seen," from phainesthai "to appear," passive of phainein "to bring to light; to show," from PIE base *bhhā- "to shine;" cf. Skt. bhāati "shines, glitters;" Av. bā- "to shine, appear, seem," bāmya- "light, luminous, bright," bānu- "light, ray;" Mid.Pers. bâm "beam of light, splendor," bâmik "brilliant," bâmdâd "morning, dawn."

Padidé, noun from padid "manifest, evident, conspicuous, in sight," variant padidâr, from Mid.Pers. pad didâr "visible," from pad "to, at, for, in," evolved to "to; for; in; on; with; by" in Mod.Pers. (O.Pers. paity; Av. paiti "to, toward, in, at;" cf. Skt. práti, Gk. poti) + did past stem of didan "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").

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