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

1) General: Not limited by restrictions or exceptions; perfect in quality or nature; unqualified in extent or degree; complete.
2) Physics: Relating to measurements or units of measurement derived from fundamental units of length, mass, and time.
3) Physics: Having an ideal value as opposed to a conditional or relative one.
See also: → absolute acceleration, → absolute dating, → absolute humidity, → absolute luminosity, → absolute magnitude, → absolute permeability, → absolute space, → absolute temperature, → absolute tensor, → absolute time, → absolute viscosity, → absolute zero.

From M.Fr. absolut, from L. absolutus "unrestricted," p.p. of absolvere "to set free," from ab- "away" + solvere "to loosen," from PIE *leu-. → solve.

Avast from negation prefix → a- + vast, variant of bast, basté "tied, bound," 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.

Synonymous: motalq(مطلق), from Ar.

For a body that moves with respect to a rotating → reference frame, the vector sum of the observed acceleration, the → Coriolis acceleration, and the → centrifugal acceleration. See also the → Coriolis theorem.

→ absolute; → acceleration.

Any method of measuring the age of an event or object in years. For example, in geology, this method can, unlike → relative dating, give us the age of a rock or fossil in x number of years. The most widely used and accepted method of absolute dating is → radioactive dating. See also: → radiocarbon dating, → radiometric dating.

→ absolute; → dating.

The difference between the measured value of a quantity x₀ and its (true) actual value x, given by Δx = x₀ - x. See also: → relative error.

→ absolute; → error.

In a system of moist air, the ratio of the mass of water vapor to the total volume of the system. → humidity.

→ absolute; → humidity.

A star's → intrinsic brightness, i.e. the total amount of energy radiated by the star per second. → Luminosity is often expressed in units of watts or erg/sec. The Sun's absolute luminosity is 3.86 × 10³³ erg/sec.

→ absolute; → luminosity.

1) The → magnitude a star would have if it were at a distance of 10 → parsecs in a void space, without → interstellar absorption. The absolute magnitude is usually deduced from the → visual magnitude, measured through a V filter (→ UBV system), when it is written as M_V. If it is defined for another wavelength, it gets another index (U, B, etc). If the radiation on all wavelengths is included, it becomes absolute → bolometric magnitude, M_bol. The Sun has the absolute magnitude + 4.8. Most of the stars have absolute magnitudes ranging between -9 (→ supergiants) and + 19 (→ red dwarfs) (M.S.: SDE).
2) The brightness a → comet or → asteroid would have if it were at a distance of 1 → astronomical unit both from the Sun and the Earth and were completely illuminated by the Sun (M.S.: SDE).

→ absolute; → magnitude.

A measurement in which the comparison is directly with quantities whose units are basic units of the system. For example, the measurement of speed by measurements of distance and time is an absolute measurement, but the measurement of speed by a speedometer is not an absolute measurement. Note that the word absolute measurement implies nothing about → precision or → accuracy (IEEE Standard Dictionary of Electrical and Electronics Terms).

→ absolute; → measurement.

→ magnetic permeability.

→ absolute; → permeability.

A fixed space in which physical phenomena occur and whose properties do not depend on what occupies it, nor on the observer. It is a distinguished frame of reference that could show bodies to be truly moving or truly at rest. Absolute space is one of the basic assumptions of → Newtonian mechanics, but it was abandoned in Einstein's → special relativity. See also → absolute time; → space-time.

→ absolute; → space.

Also called → thermodynamic temperature, the value of a → temperature in the → Kelvin scale. It is is equal to the temperature on the → Celsius scale -273.15 °C.

→ absolute; → temperature.

A → tensor of → weight  → zero.

→ absolute; → tensor.

A universal time supposed to be the same for all observers at any place in the Universe. Absolute time is one of the foundations of → Newtonian mechanics, but it fails to account for physical phenomena in → reference frames with relative motion. Its abandoning was one of the starting points of → special relativity. See also → absolute space; → space-time.

→ absolute; → time.

For any → real number a, the non-negative value of a without regard to its sign; denoted by |a|. Same as → modulus. The absolute value of a is always either → positive or → zero, but never negative. The absolute value of a number may be thought of as its → distance from zero. The following rules hold:
|ab| = |a||b|
|a + b|  ≤  |a| + |b|
|a - b|  ≥  |a| - |b|
For a> 0, |x|  ≤  a if and only if -a  ≤  x  ≤  a.

→ absolute; → value.

Same as → viscosity and → dynamic viscosity.

→ absolute; → viscosity.

The → zero point of the → Kelvin scale of → temperature; the theoretical point at which all molecular activity ceases, -273.16 °C.

→ absolute; → zero.

A suspension of fine solid or liquid particles in a gas.

Aerosol from aero "air" + sol(ution).

Havâlu from havâ "weather" + lu from → luyé, luyeš, → solution.

Of a telescope, the smallest angle betwwen two → point sources that produces distinct images. It depends on both the wavelength at which observations are made and on the diameter of the telescope. Same as → spatial resolution.

→ angular; → resolution.

Meteo.: The point on the → celestial sphere that lies directly opposite the Sun from the → observer, observer, that is, on the line from the Sun through the observer. The antisolar point is the center of the rainbow, and can be easily found on a sunny day: it it located at the shadow of one's head; it is 180° away from the Sun. If the Sun is in the sky, the antisolar point is below the horizon. If the Sun has set, the antisolar point is above the horizon.

→ anti-; → solar; → point.

The duration of one rotation of the Earth on its axis (→ Earth's rotation), with respect to the → apparent Sun. It is measured by successive transits of the apparent Sun over the lower branch of a → meridian.

→ apparent; → solar day.