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

→ superheterodyne technique.

→ heterodyne; → technique.

The method used to detect very brief flashes of → Cherenkov radiation generated by the → cascade shower of → relativistic charged particles produced when a very high-energy → gamma ray (in the range 50 GeV to 50 TeV) strikes the atmosphere at a typical altitude of 10 km. Owing to this technique, it possible to discriminate cosmic gamma rays from the cosmic ray background and to determine their energy and source direction. More specifically, the incoming gamma-ray photon undergoes → pair production in the vicinity of the nucleus of an atmospheric molecule. The electron-positron pairs produced are of extremely high energy and immediately radiate in a → bremsstrahlung process. This radiation is itself extremely energetic, with many of the photons undergoing further pair production. A cascade of charged particles ensues which, due to its extreme energy, produces a flash of Cherenkov radiation lasting between 5 and 20 nano-seconds. The total area on the ground illuminated by this flash corresponds to many hundreds of square meters, which is why the effective area of IACT telescopes should be large.

→ imaging; → atmospheric; → Cherenkov; → technique.

An observational technique based on principles of → interferometry.

→ interferometric; → technique.

A technique that uses a suitable arrangement of → laser beams and magnetic fields to capture → cesium (¹³³Cs) atoms from a thermal vapor and slow the motion of the atoms, cooling them to just a few micro-kelvins above the → absolute zero. The technique allows trapping some 10⁷ cesium atoms in a cloud a few millimeters in diameter in a few tenths of a second. At a temperature of 2 μK, the average thermal velocity of the cesium atoms is of the order of 1 cm s^-1, so they stay together for a relatively long time. The laser cooling technique is the key tool which enabled the operation of an → atomic fountain clock.

→ laser; → cooling; → technique.

The technique used in a radio receiver in which the frequency of an incoming signal is changed by adding it to a signal generated within the receiver to produce fluctuations or beats of a frequency equal to the difference between the two signals. See also → mixer.

→ superheterodyne receiver; → technique.

The body of specialized procedures and methods used in any specific field, especially in an area of applied science.

From Fr. technique "formal practical details in artistic expression," noun use of adj. technique "of art, technical," from Gk. tekhnikos, from tekhne "art, skill, craft, method, system;" cognate with Pers. tarâš- "to cut, hew; scape; shave," tišé "axe," as below.

Tašnik, related to Pers. tarâšidan "to cut, hew; scape; shave;" Mid.Pers. tâšitan "to cut, cleave; create by putting together different elements;" from Av. taš- "to cut off, fashion, shape, create," taša- "axe" (Mod.Pers. taš, tišé "axe;" tarâšidan "to shave"), tašan- "creator;" cf. Skt. taks- "to fom by cutting, tool, hammer, form," taksan- "wood-cutter, carpenter;" Gk. tekton "carpenter," tekhne "art, skill, craft, method, system;" L. textere "to weave;" PIE *teks- "to fashion."
Fann or fan, from Pers. fan "way, manner, mode, art, science," related to Mod/Mid.Pers. pand "path, advice, counsel;" Khotanese pande "road, path;" Ossetic fœndœg "path, road;" O.Pers. paθi- "path, way;" Av. paθ- "path, way," variants paθi-, paθā-, pantay-; cf. Skt. pánthā- "road, path, course;" Gk. patos "path, way," pontos "sea;" L. pons "bridge, path;" P.Gmc. *finthanan "to find;" E. find; PIE base *pent- "to go, to tread."