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

A change taking place in a system that has perfect thermal insulation, so that heat cannot enter or leave the system and energy can only be transferred by work.

→ adiabatic; → change.

A periodic change in one of the components of the orbit of a celestial object.

→ canonical; → change.

1) (v.intr.) To undergo change.
2a) (v.tr.) To → alter, modify, or make different; to make to pass from one state to another; to → exchange.
2b) To transform or convert.
3) To substitute another or others for; exchange for something else, usually of the same kind.
4) The act of changing; alteration or variation of any kind. → adiabatic change, → canonical change, → polytropic change, → secular change, → exchange.

M.E., from O.Fr. changier, from L.L. cambiare, from L. cambire "to exchange, barter," of Celtic origin, cf. Breton kamm "curved, bent;" Gk. kampe "a corner, a joint;" L. campus "a field;" Lith. kampus "corner;" PIE *kamb- "to bend, crook."

Galnidan, variant of gardidan, gaštan "to change, to turn," → Universe, cf. Awromani gelnây, geln- "to turn over" (Cheung 2007).

A collisional process in which an → ion collides with a neutral → atom or → molecule and captures one of its electrons. One of the most important charge-exchange processes occurring in the → interstellar medium is: O⁺ + H → H⁺ + O + 0.020 eV.

→ charge; → exchange.

1) To give and receive reciprocally.
2) The act, process, or an instance of exchanging. → exchange force, → exchange particle, → Prevost's law of exchanges.

O.Fr. eschangier, from V.L. *excambiare, from L. → ex- "out" + cambire "barter."

Mod.Pers. gahulidan "to exchange," Kurd. guhartin/guhêr- "to exchange," Mid.Pers. wihir "to change," wihirišn "change," Manichean Mid.Pers. hr'g; Buddhist Mid.Pers. hlg "duty, tribute; work, effort;" Arm. loanword hark "duty, tribute;" Ar. loanword xarj "expense," xarâj "land, property tax;" Proto-Iranian *har- "to barter, trade; to pay tribute;" IE cognates: Gk. elein "to take (by force)," elor "loot, booty, catch;" Goth. saljan "to bring, to sacrifice;" O.E. sellan "to hand over, sell;" O.H.G. sala "delivery of goods."

The force that governs the exchange of particles in the interaction between bodies. → exchange particle.

→ exchange, → force.

In quantum field theory, a particle that transfers momentum and energy between interacting objects, and is said to mediate the interaction. All four of the fundamental forces involve the exchange of one or more particles. For example, photon is the exchange particle of the electromagnetic force.

→ exchange, → particle.

A change in the → pressure or → volume of a → gas in a → polytropic process.

→ polytropic; → change.

A statement concerned with thermodynamic heat exchange, according to which bodies in → thermal equilibrium are simultaneously absorbing and emitting radiant energy. A body radiates in the same way whether other bodies are present or not. Also called Prevost's theory of exchanges.

Named after Pierre Prévost (1751-1839), a Swiss philosopher and physicist, who, in 1791, put forward the statement; → law; → exchange.

A continuous, non-periodic change in one of the attributes of the states of a system. Often, a change in an orbit due to dissipation of energy. See also → canonical change.

→ secular; → change.