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

The convention for measuring angles on the sky in astronomy (Abbreviated as PA). It is the direction of an imaginary arrow in the sky, measured from north through east: 0° = north, 90° = east, 180° = south, and so on to 359° and back to 0°. Applied to a binary system it is the direction of a secondary body or feature from a primary, measured in the system. .

→ position; → angle.

In single dish astronomy, an observing mode in which the telescope is moved between the object position and a user defined reference position. The aim is to eliminate unwanted signals in the baseline. → beam switching; → frequency switching.

→ position; → switching.

Relating to or determined by position.

→ position; → -al.

The branch of astronomy that is used to determine the location of objects on the celestial sphere, as seen at a particular date, time, and location on the Earth. Same as → spherical astronomy.

→ positional; → astronomy.

A system of representing → numbers in which the → position of a → digit in a string of digits affects its value. The decimal system is a positional notation for expressing numbers. Same as → place-value notation and → positional number system.

→ positional; → notation.

A → number system in which the value of each digit is determined by which place it appears in the full number. The lowest place value is the rightmost position, and each successive position to the left has a higher place value. In the → number system conversion, the rightmost position represents the "ones" column, the next position represents the "tens" column, the next position represents "hundreds", etc. The values of each position correspond to powers of the → base of the number system. For example, in the usual decimal number system, which uses base 10, the place values correspond to powers of 10. Same as → place-value notation and → positional notation. See also → number system conversion.

→ positional; → number; → system.

The act or process of putting in a particular position or determining the psition of.

Verbal noun of → position; → -ing.

A word used with a noun or pronoun to mark its relation with another word.

From L. praepositionem "a putting before," from praepositus, p.p. of praeponere "put before," from prae "before," → pre-, + ponere "put, set, place," → position.

Pišhel, from piš-, "before," → pre-, + hel-, helidan, heštan "to place, put," → leap.

1) The act of offering or suggesting something to be considered, accepted, adopted, or done.
2) A plan or scheme proposed.
3) Logic: A statement in which something is affirmed or denied, so that it can therefore be significantly characterized as either true or false.
4) Math.: A formal statement of either a truth to be demonstrated or an operation to be performed; a theorem or a problem (Dictionary.com).

Verbal noun of → propose.

Logic: Of, relating to, or in the form of a → proposition.

→ proposition; → -al.

Logic: A → propositional symbol that represents a → specific → proposition.

→ propositional; → constant.

A branch of logic that deals with the → truth values of logical statements (→ sentences, → propositions) and uses → logical connectives to build more complex → expressions. The distinctive feature of propositional logic is that it does not deal with logical relationships and properties that involve the parts of a statement smaller than the simple statements making it up. The propositions are evaluated as → true or → false. A more expressive system is provided by the → first-order logic.

→ proposition; → -al; → logic.

An upper case letter, e.g. "A," "B," "C," etc. representing a → proposition. Propositional symbols are divisible into two sorts: → propositional constants and → propositional variables.

→ propositional; → symbol.

Logic: A → propositional symbol that represents any → proposition whatsoever.

→ propositional; → variable.

1) The act of placing upon; the state of being placed upon.
2) Math. The act of placing (one geometric figure) over another so that all like parts coincide.

→ super- + → position.

Barhamneheš, from bar- "on, upon, up" (Mid.Pers. abar; O.Pers. upariy "above; over, upon, according to;" Av. upairi "above, over," upairi.zəma- "located above the earth;" cf. Gk. hyper- "over, above;" L. super-; O.H.G. ubir "over;" PIE base *uper "over") + -ham- "together, with," → syn-, + neheš, → position.

1) Math.: The principle concerned with homogeneous and non-homogeneous → linear differential equations, stating that two or more solutions to a linear equation or set of linear equations can be added together so that their sum is also a solution.
2) One of the most fundamental principles of → quantum mechanics which distinctly marks the departure from classical concepts. It holds that any linear superposition of → wave functions is also a possible wave function. Simply put, the state of an object is all its possible states simultaneously, as long as we do not look to check. It is the measurement itself that causes the object to be limited to a single possibility. The superposition principle is rooted in the linearity of → Schrödinger's equation. Hence if two solutions of the wave function, ψ₁ and ψ₂, are known, other solutions, of the form: ψ = a₁ψ₁ + a₂ψ₂ also represent possible states of the system.

→ superposition; → principle.

Math.: A permutation of a set of elements that interchanges two elements and leaves the remaining elements in their original positions. For example, the swapping of 2 and 5 to take the list 123456 to 153426 is a transposition.
Optics: The changing of the relative curves of a lens without changing its refractive value.

→ trans-; → position.

The coordinates of an object for a given date, with respect to the true equator and the true equinoxes for the instant of time in question.

→ true; → position.