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

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 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.