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

The distance derived from the → proper motion of an object. If an object has a known → transverse velocity  u, and has an observed angular motion of dθ/dt, then the proper motion distance is defined as: d = u/(dθ/dt).

→ proper; → motion; → distance

Comparative relation between things, sizes, quantities, numbers, parts, etc.
Math.: A statement of the equality of two ratios.

M.E. proporcio(u)n, from O.Fr. proportion, from L. proportio "comparative relation, analogy," from the phrase pro portione "according to the relation" (of parts to each other), from pro "for" + portio "part, shar."

Barpâreš, from bar- "on; up; upon; in; into; at; forth; with; near; before; according to" (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") + pâr "part, portion, piece" (variants pâréparré "portion, segment (of an orange)," pargâlé, "piece, portion; patch;" (dialects Kermâni pariké "portion, half;" Tabari perik "minute quantity, particle;" Lârestâni pakva "patch;" Borujerdi parru "patch"); Mid.Pers. pârag "piece, part, portion; gift, offering, bribe;" Av. pāra- "debt," from par- "to remunerate, equalize; to condemn;" PIE *per- "to sell, hand over, distribute; to assigne;" Gk. peprotai "it has been granted;" L. pars, as above; Skt. purti- "reward;" Hitt. pars-, parsiya- "to break, crumble") + -eš suffix.

Being in or characterized by proportion.
Math.: Of two quantities, having the same or a constant ratio or relation.

→ proportion + → -al.

A device in which an electronic detection system receives pulses that are proportional to the number of ions formed in a gas-filled tube by ionizing radiation.

→ proportional; → counter.

Math.: A relationship bewteen two quantities such that if one quantity changes the other changes in the same proportion; denoted as y ∝ x.

→ proportional + → -ity.

Math.: A → constant that converts a proportionality into an → equation. Thus the proportionality constant k converts the proportionality y ∝ x into the equation y = kx.

→ proportionality + → constant.

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.

The act or process of propelling. The state of being propelled.

Verbal noun from → propel.

1) The act of protesting.
2) Formal expression or declaration of objection, dissent, or disapproval (Dictionary.com).

→ protest; → -tion.

A particle of the hadron family which is one of the two particles that make up atomic nuclei. It has an electric charge of one positive fundamental unit, a diameter of about 1.65 x 10^-13 cm, and a mass of about 1.67 x 10^-24 g (about 938 MeV c^-2).

From Gk. proton, neuter of protos "first." Coined by Eng. physicist Ernest Rutherford (1871-1937).

The temperature in the → solar wind, as derived from the mean kinetic energy of protons: mv²/2 = (3/2)kT_p, where k is → Boltzmann's constant. There are two types of proton temperature: parallel temperature, measured from protons moving parallel to the magnetic field, and perpendicular temperature relating to protons at right angles to the magnetic field. The proton temperature is usually derived using particle detectors on board space probes that determine the velocity → distribution function of the particles from their energies (N. Meyer-Vernet, 2007, Basics of the Solar Wind, Cambridge Univ. Press). See also → electron temperature.

→ proton; → temperature.

A series of → thermonuclear reactions, taking place mainly in → low-mass stars, such as the Sun, which transforms four hydrogen nuclei (protons) into one helium (⁴He) nucleus and thereby generates energy in the stellar core. First, two protons (¹H) combine to form a → deuterium nucleus (²H) with the emission of a → positron (e⁺) and a → neutrino (ν): ¹H + ¹H → ²H + e⁺ + ν. The deuterium nucleus then rapidly captures another proton to form a helium-3 nucleus (³He), while emitting a → gamma ray (γ): ²H + ¹H → ³He + γ. There are three alternatives for the next step. In the PP I chain, occurring in 86% of the cases, two ³He nuclei fuse to a final ⁴He nucleus while two protons are released: ³He + ³He → ⁴He + ¹H + ¹H. The mass of the resulting ⁴He nucleus is less than the total mass of the four original protons used to produce ⁴He (→ mass defect). The difference, ~ 0.7% of the total mass of the protons, is converted into energy and radiated by the Sun. In this process, the Sun loses some 4 million tons of its mass each second. See also → CNO cycle.

→ proton; → chain.

A → thermonuclear reaction in which two protons collide at very high velocities and combine to form a → deuterium. See also → proton-proton chain.

→ proton; → reaction.

A compact, hot, and → neutrino-rich object that results from a → supernova explosion and is a transition between an → iron core and a → neutron star or → black hole. The life span of a protoneutron star is less than one minute.

→ proto-; → neutron; → star.

1) The act of provoking.
2) Something that → incites, → instigates, angers, or irritates (Dictionary.com).

Verbal noun of → provoke.