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

A phenomenon occurring when a light ray traveling cross an → interface from a higher → refractive index medium to a lower refractive index medium hits the interface at an angle larger than the → critical angle. In these conditions the light will not pass through to the second → medium at all. Instead, all of it will be reflected back into the first medium.

→ total; → internal; → reflection.

An inherited or common body of beliefs or practices belonging to a particular people, family, or institution over a relatively long period. Also their transmission over time.

M.E. tradicion, from  O.Fr. tradicion, from L. traditionem "delivery, surrender, a handing down," from traditus, p.p. of tradere "to deliver, hand over," from → trans- "over" (time) + dare  "to give," → datum.

Tarâdâd, from tarâ- "over time," → trans-, + dâd past stem of dâdan "to give," → datum.

A function which is not → algebraic. For example y = cosx, y = 10^xx.

→ transcendental; → function.

The mathematical relationship between the output of a control system and its input: for a linear system, it is the Laplace transform of the output divided by the Laplace transform of the input under conditions of zero initial-energy storage.

→ transfer; → function.

1) The act or process of transforming. The state of being transformed.
2) The relationship between description of a physical phenomenon in one → reference frame to another. → Galilean transformation; → Lorentz transformation.
3) Math.: The act, process, or result of transforming or mapping.

Verbal noun of → transform.

1) Passage from one position, state, stage, subject, concept, etc., to another.
2) A change between phases such as solid to liquid or liquid to gas.
3) A change in the → energy level or state of an atom or nucleus. → atomic transition, → bound-bound transition, → bound-free transition, → cascade transition, → discrete transition, → forbidden transition, → hyperfine transition, → nuclear transition, → permitted transition, → phase transition, → quark-hadron phase transition, → radiative transition, → rotational transition, → semi-forbidden transition, → transition disk, → transition function, → transition probability, → vibrational transition.

From L. transitionem (nominative transition) "a going across or over," noun of action from transire "go or cross over," from → trans- "across" + ire "to go."

Gozareš, verbal noun of gozaštan "to transit, pass," → transit, + -eš, → -tion.

The → accretion disk of a → T Tauri star that displays very weak or no → infrared excess at → near infrared wavelengths, but shows strong excess at → intermediate infrared and longer wavelengths. This happens when the hot inner dust disk has dissipated whereas the cooler outer disk is still intact.

→ transition; → disk.

The → probability of finding the → Universe in a → state labelled X₂ at a time t₂, if it was in a state X₁ at an earlier time t₁.

→ transition; → function.

The probability that a quantum-mechanical system will make a transition from a given initial state to a given final state.

→ transition; → probability.

In fluid mechanics, a flow composed of → laminar and → turbulent flows, for which the → Reynolds number is between 2300 and 4000.

→ transition; → flow.

1) Mechanics: A motion of a rigid body characterized by parallel paths of all particles. Every point of the body in translation has the same velocity and acceleration at any particular instant. The translation motion may be rectilinear or curvilinear.
2) Math.: A transformation which moves all points on a plane through the same distance in the same direction. The object and its image are congruent. Also a function obtained from a given function by adding the same constant to the value of each of its variables.
3) A rendering from one language into another; a version of such a rendering.

Verbal noun of → translate.

Tarâjâyeš, verbal noun of tarâjâyidan, tarâzabâneš, verbal noun of tarâzabânidan, → translate.

1) The act or process of transmitting. The fact of being transmitted.
2) The broadcasting of electromagnetic waves from one location to another, as from a transmitter to a receiver.

Verbal noun of → transmit.

The frequency range above the cutoff frequency in a waveguide or transmission line.

→ transmission; → band.

The ratio given by the → amplitude (or energy) of a transmitted wave divided by the amplitude (or energy) of the incident wave.

→ transmission; → coefficient.

A diffraction grating that has grooves ruled onto a transparent material so that a beam of light passed through the grating is partly split into spectral orders.

→ transmission; → grating.

A decrease in power in transmission from one point to another.

→ transmission; → loss.

An assembly of elements which are capable of functioning together to transmit power or signals.

→ transmission; → system.

The act or process of transmuting.
Physics: Any process in which a nuclide is transformed into a different nuclide, usually one of a different element.

Verbal noun of → transmute.

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.

In medieval astronomy, a spurious oscillatory motion of the equinoxes thought to have a period of 7,000 years. This concept, attributed to Thâbit ibn Qurra (c. 830-901), had a profound influence on medieval astronomy. In order to explain trepidation, Thâbit was said to have added a new sphere to the eight Ptolemaic spheres beyond the sphere of fixed stars.

From L. trepidationem "agitation, trembling," from trepidare "to tremble, hurry," from trepidus "anxious, scared;" cf. Skt. trprá- "hasty;" PIE base *trep- "to shake, tremble."

Larzeš, verbal noun of larzidan "to tremble, shiver;" Mid.Pers. larzidan "to shake, tremble;" Manichean Mid.Pers. rarz- "to shiver with fever;" Proto-Iranian *rarz- "to shake, tremble."