An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



<< < -ne Nao nat nea neg nes neu New New niv noi non non nor nov nuc nul num > >>

Number of Results: 357
null geodesic
  کهین‌ره ِ نول   
kehinrah-e nul

Fr.: géodésique nulle   

1) The path taken by a light ray in a curved → space-time just as a → timelike geodesic describes the path of a material particle.
2) A → geodesic of length zero.

null; → geodesic.

null hypothesis
  انگاره‌ی ِ نول   
engâre-ye nul

Fr.: hypothèse nulle   

Statistics: The assumption of the absence of a particular pattern in a set of data. The null hypothesis, denoted by H0, is put forward to be rejected in order to support an → alternative hypothesis.

null; → hypothesis.

null lens
  عدسی ِ نول   
adasi-ye nul


A lens used in the optical testing of an aspheric surface. It converts a spherical wavefront into one that precisely matches the surface under test. When the wavefront is reflected from that surface, it reverses its path and, if the surface is perfect, results in a perfect emerging spherical wavefront, which is easily evaluated.

null; → lens.

null matrix
  ماتریس ِ نول   
mâtris-e nul

Fr.: matrice nulle   

An m × n matrix whose elements are all zeros. Also known as zero matrix.

null; → matrix.

null method
  روش ِ نول   
raveš-e nul

Fr.: méthode de zéro   

A method of comparing, or measuring, forces, electric currents, etc., by so opposing them that the pointer of an indicating apparatus remains at, or is brought to, zero, as contrasted with methods in which the deflection is observed directly. Same as zero method.

null; → method.



A device using the → nulling interferometry technique.

Agent noun of the verb → null.

nulling fraction (NF)
  برخه‌ی ِ نولش   
barxe-ye nuleš

Fr.: fraction de phase d'arrêt   

The fraction of time that a → pulsar undergoes → pulse nulling. For most → nulling pulsars this fraction can range from zero (for the → Vela pulsar) to more than 50%.

null; → -ing; → fraction.

nulling interferometry
  اندرزنش‌سنجی ِ نولی   
andarzanešsanj-ye nuli

Fr.: interférométrie annulante   

A technique for blocking the light of a bright source in order to reveal a faint source near it. This technique uses destructive → interference between two or more → coherent beams from a number of telescopes to make the bright center dark. Nulling interferometry can be used to search the region immediately around a star for → extrasolar planets and → circumstellar dust clouds by suppressing the star's glare.

Nulling, from → null; → interferometry.

nulling pulsar
  پولسار ِ نولنده   
pulsâr-e nulandé

Fr.: pulsar à phase d'arrêt   

A → pulsar that undergoes → pulse nulling.

null; → -ing; → pulsar.

  ۱) عدد، شماره؛ ۲) شمار   
1) adad (#), šomâré (#); 2) šomâr (#)

Fr.: 1) nombre, numéro; 2) numéro   

1) Any real or complex numeral quantity.
2) The sum, total, count, or aggregate of a collection of units.

From M.E. nombre, from O.Fr. nombre, from L. numerus "a number, quantity," from PIE base *nem- "to divide, distribute, allot."

Adad, loan from Ar.
Šomâr, šomâré, noun from šomârdan "to count, reckon, calculate, enumerate, account for," from Mid.Pers. ôšmârtan; Av. base (š)mar- "to have in mind, remember, recall," pati-šmar- "to recall; to long for," hišmar-; cf. Skt. smar- "to remember, become aware," smarati "he remembers;" L. memor, memoria; Gk. mermera "care," merimna "anxious thought, sorrow," martyr "witness."

number density
  چگالی ِ عددی   
cagâli-ye adadi

Fr.: densité nmérique   

Number of a particular type of object found in each unit volume.

number; → density.

number e
  عدد ِ e   
'adad-e e

Fr.: nombre e   

The → base of the → natural logarithm. It is defined as: e = lim (1 + 1/n)n when n→ ∞. For n = 1, e = 2 and for n = 10, e = 2.5937424601, etc. The number e is → irrational (Euler, 1737) and → transcendental (Hermite, 1873).


number pi
  عدد ِ پی   
adad-e pi (π)

Fr.: nombre pi (π)   

Symbol, π, for the ratio of the circumference of a circle to its diameter in Euclidean geometry; a fundamental mathematical constant, equal to 3.14159... π is an → irrational number (Lambert, 1761) and also a → transcendental number (von Lindemann, 1882). The most accurate determination of π prior to the Scientific Revolution belongs to the Iranian mathematician Jamshid Kashani, who gave 16 correct decimal places in A.D. 1424. With the advent of → calculus and more recently the invention of powerful computers, the decimal representation of π has now been computed to more than 1012 digits.

The π notation, representing the first letter of the Gk. word περιμετρον → perimeter, was first used by the British mathematician William Jones (1675-1749) in 1706. Its use was generalized after its adoption by the Swiss mathematician Leonard Euler (1707-1783) in 1737; → number.

number system
  راژمان ِ عددها، ~ عددی   
râžmân-e adadhâ, ~ adadi

Fr.: système de numération   

Same as → numeral system.

number; → system.

number system conversion
  هاگرد ِ راژمان ِ عددی   
hâgard-e râžmân-e adadi

Fr.: conversion de système de numération   

The conversion of a → number system with a given → base to another system with a different base; such as the conversion of a → decimal number (base 10) to a → binary number system (base 2). In order to convert a number into its representation in a different number base, we have to express the number in terms of powers of the other base. For example, to convert the decimal number 100 to base 3, we must figure out how to express 100 as the sum of powers of 3. We proceed as follows:
1: Divide the decimal number to be converted (100) by the value of the new base (3).
2: Get the remainder from Step 1 (that is 1) as the rightmost digit (least significant digit) of new base number.
3: Divide the quotient of the previous divide (33) by the new base.
4: Record the remainder from Step 3 (0) as the next digit (to the left) of the new base number.
Repeat Steps 3 and 4, getting remainders from right to left, until the quotient becomes zero in Step 3 (2 and 0).
The last remainder thus obtained (1) will be the most significant digit of the new base number.
Therefore, 10010 = 102013.
Conversely, to convert from another base to decimal we must:
1: Determine the column (positional) value of each digit.
2: Multiply the obtained column values (in Step 1) by the digits in the corresponding columns.
3: Sum the products calculated in Step 2. The total is the equivalent value in decimal.
For example, the binary number 1100100 is determined by computing the place value of each of the digits of the number:
(1 × 26) + (1 × 25) + (0 × 24) + (0 × 23) + (1 × 22) + (0 × 21) + (0 × 20) = 64 + 32 + 0 + 0 + 4 + 0 + 0 = 100.

number; → system; → conversion.

number theory
  نگره‌ی ِ عددها   
negare-ye adadhâ

Fr.: théories des nombres   

The branch of mathematics that studies the relationship between integers and their generalization.

number; → theory.

  ۱) شمارال؛ ۲) شماره‌ای، عددی   
1) šomârâl; 2) šomâre-yi (#), adadi (#)

Fr.: 1) numéral; 2) numéral, numérique   

1) A symbol, group of symbols, or word used to express a number. For any number there is an infinite number of numeral expressions. For example, the number two can be written as 2, II, binary 10, 4/2, 18/8, etc.
2) Of, pertaining to, or consisting of numbers or numerals.

From L.L. numeralis "of, or belonging to number," → number + → -al

Šomârâl, from šomâr, → number, + -al, → -al.

numeral system
  راژمان ِ عددی، ~ عددها   
râžmân-e adadi, é adadhâ

Fr.: système de numération   

A set of → symbols and → rules for representing → numbers. Same as → number system. See also: → Greek numeral system, → Roman numeral system, → Indian numeral system.

numeral; → system.

šomârân (#)

Fr.: numérateur   

The quantity x in a fraction x/y). The quantity y is the → denominator.

L.L. numerator "a counter, numberer," from L. numera(re) "to number," → number + -tor a suffix forming personal agent nouns from verbs and, less commonly, from nouns.

Šomârân, agent noun of šomârdan, → number.

adadi (#)

Fr.: numérique   

Relating to or expressed in numbers.

Adj. of → number.

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