An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 471 Search : ity
hamânandi (#)

Fr.: similarité   

The state of being similar; likeness; resemblance.

similar; → -ity.

similarity transformation
  ترادیسش ِ همانندی   
tarâdiseš-e hamânandi

Fr.: transformation de similarité   

1) A transformation that preserves angles and changes all distances in the same ratio.
2) A transformation of the form B = X-1AX relating two → square matrices A and B.

similarity; → transformation.

hamzamâni (#)

Fr.: simultanéité   

The property of events occurring → simultaneously.

Noun from → simultaneous; → -ity.

takini (#)

Fr.: singularité   

1) Math.: A point at which a given mathematical object is not defined.
2) Physics: A point in → space-time in which gravitational force causes space-time to have infinite curvature; matter is crushed to infinite density and zero volume. This happens at the center of a → black hole where space and time cease to exist as we know them, and the known laws of physics break down. See also → Schwarzschild singularity; → initial singularity.

singular + → -ity.

solar activity
  ژیرندگی ِ خورشید   
žirandegi-ye xoršid

Fr.: activité solaire   

The general term for all forms of short-lived phenomena on the Sun, including → solar flares, → sunspots, → prominences, etc., indicating that the Sun is an active star.

solar; → activity.

solar activity cycle
  چرخه‌ی ِ ژیرندگی ِ خورشید   
carxe-ye žirandegi-ye xoršid

Fr.: cycle d'activité solaire   

Same as the → solar cycle.

solar activity; → cycle.

solar luminosity
  تابندگی ِ خورشید   
tâbandegi-ye xoršid (#)

Fr.: luminosité solaire   

The total → radiant energy, in all wavelengths, emitted by the Sun in all directions. It is 3.828 × 1026 W or 3.828 × 1033 erg sec-1 (International Astronomical Union, Resolution B3, 14 August 2015, Honolulu, USA). This is the luminosity unit conventionally used to give the luminosities of stars. See also: → solar constant. When the Earth first formed, 4.56 billion years ago, the Sun radiated 30% less energy than it does today, thus giving rise to the so-called → faint early Sun paradox. Ever since then, its power has increased by 7% every billion years (I. Ribas, 2009, arXiv:0911.4872).

solar; → luminosity.

solar metallicity
  فلزیگی ِ خورشیدی   
felezigi-ye xoršidi

Fr.: métallicité solaire   

The proportion of the solar matter made up of → chemical elements heavier than → helium. It is denoted by Z, which represents the sum of all elements heavier than → helium, in mass fraction. The most recent determination of the solar Z gives a value of 0.0134 (Asplund et al. 2009, ARAA 47, 481), corresponding to the present-day photospheric composition.

solar; → metallicity.

solar velocity
  تندای ِ خورشید، ~ خورشیدی   
tondâ-ye xoršid, ~ xoršidi

Fr.: vitesse solaire   

The rate of change of the Sun's position with respect to the local standard of rest toward the → solar apex.

solar; → velocity.


Fr.: solidité   

The state, property, or quality of being solid. Solidness.

solid; → -ity.

sound intensity
  درتنویی ِ صدا   
dartanuyi-ye sedâ

Fr.: intensité de son   

The average → sound power passing through a unit area perpendicular to the direction that the sound is traveling. It is usually expressed in watts per square meter.

sound; → level.

sound intensity level
  تراز ِ درتنویی ِ صدا   
tarâz-e dartanuyi-ye sedâ

Fr.: niveau de l'intensité de son   

The expression of sound intensity in decibel units. The sound intensity level (LI), in decibels, is computed as: LI = 10 log (I/I0), where I is the measured sound intensity and I0 is the reference intensity (1 x 10 -12 watt per square meter).

sound; → intensity; → level.

sound quality
  چونای ِ صدا   
cunâ-ye sedâ

Fr.: qualité de son   

The number of → overtones present in a sound and their respective intensity. Like → loudness, it is a subjective quantity and cannot be measured with instruments.

sound; → quality.

space velocity
  تندای ِ فضایی   
tondâ-ye fazây

Fr.: vitesse spatiale   

The velocity of a star relative to the Sun.

space; → velocity.

special relativity
  بازانیگی ِ ویژه   
bâzanigi-ye vižé

Fr.: relativité restreinte   

The theory formulated by A. Einstein in 1905, which is based on the following two → postulates:
1) → Principle of relativity: The laws of physical phenomena are the same when studied in terms of two reference systems moving at a constant velocity relative to each other.
2) → Principle of constancy: The → velocity of light in free space is the same for all observers and is independent of the relative velocity of the source of light and the observer.
The term "special theory of relativity" refers to the restriction in the first postulate to reference systems moving at a constant velocity relative to each other (→ inertial reference frame). See also → general relativity.

special; → relativity.

specific density
  چگالی ِ آبیزه   
cagâli-ye âbizé

Fr.: densité spécifique   

Same as → relative density.

specific; → density.

specific gravity
  گرانی ِ آبیزه   
gerâni-ye âbizé

Fr.: gravité spécifique   

The ratio of the density of a substance at the temperature under consideration to the density of water at the temperature of its maximum density (4 °C).

specific; → gravity.

specific humidity
  نم ِ آبیزه   
nam-e âbizé

Fr.: humidité spécifique   

The dimensionless ratio of the mass of water vapor to the total mass in a particular volume. → humidity

specific; → humidity.

specific intensity
  درتنویی ِ آبیزه   
dartanuyi-e âbizé

Fr.: intensité spécifique   

A measure of the amount of radiation received per unit solid angle per unit time per unit area normally from an element of surface.

specific; → intensity.


Fr.: spécifité   

The state or character of being → specific.

specific; → -ity.

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