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

Same as → refractive index.

→ index; → refraction.

The process or state of discriminating the individual from the generic group or species.

→ individualize; → -tion.

The emission of radiation from an atom when it is bombarded by photons. The induced radiation has the same wavelength and direction as the bombarding radiation. Same as → stimulated emission.

→ induced; → emission.

Fission which takes place when a nucleon is bombarded with neutrons or high-energy radiation (gamma rays).

Induced, p.p. of → induce; → fission.

1) General: The act of inducing, bringing about, or causing.
2) Electromagnetism: A common term for the process by which a body having electric or magnetic properties produces magnetism, an electric charge, or an → electromotive force in a neighboring body without contact. For more details, see → electromagnetic induction; → electrostatic induction; → magnetic induction.
3) Math.: A method of mathematical proof typically used to establish that a given statement is true of all natural numbers. It is done by proving that the first statement in the infinite sequence of statements is true, and then proving that if any one statement in the infinite sequence of statements is true, then so is the next one.
4) Logic: Any form of reasoning in which the conclusion, though supported by the premises, does not follow from them necessarily. → inductive reasoning.

Verbal noun of → induce.

A device for producing high-voltage pulses by means of → electromagnetic induction. It consists of a primary coil of a few turns of wire, wound on an iron core, and insulated from a secondary coil of many turns which surrounds it coaxially. The current in the primary, which is interrupted periodically, sets up a magnetic field, first big, then zero. This changing field induces a large voltage in the secondary.

→ induction; → coil.

In magnetohydrodynamics, an equation that describes the transport of plasma and magnetic field lines over time:
∂B/∂t = ∇ x (v x B) + η∇²B,
where B is the → magnetic induction, v is the plasma velocity, and η = (μσ)^-1 the → magnetic diffusivity. The first term on the right side represents → magnetic advection and the second term → magnetic diffusion. The induction equation can also be expressed as:
∂B/∂t = -(v.∇)B + (B.∇)v - B(∇.v),
where the terms of the right-hand side stand for advection, stretching, and compression, respectively. Among these terms, net increase of the field can be done only through the stretching and compression.

→ induction; → equation.

A component of an electromagnetic field which is the region close to the source (an antenna) where steady-state magnetic and electrostatic forces can be detected. → radiation field.

→ induction; → field.

A collision between bodies in which there is a loss of total kinetic energy.

→ inelastic; → collision.

Motion free of any force, with constant velocity.

→ inertial; → motion.

1) A periodic motion of a particle that moves, free from external forces, over the surface of a rotating sphere, such the Earth. Inertial oscillations result from the → Coriolis force. For example, a hockey puck launched on a big enough lake in the northern hemisphere would turn to the right (east) and eventually loop back to nearly the initial point (actually west of that point). The time it takes for the huckey puck to return can be computed with the → Coriolis frequency.
2) Meteo.: An anticyclonic (clockwise) rotation in the northern hemisphere, with the Coriolis force providing the → centripetal acceleration with period of 2π/f, where f is the Coriolis frequency. The opposite should occur in the southern hemisphere.

→ inertial; → oscillation.

1) An act or fact of infecting; state of being infected.
2) An infecting agency or influence.
3) An infectious disease.
4) Computers: The presence of a virus in, or its introduction into, a computer system.

Verbal noun of → infect.

The conjunction of an inferior planet with the Sun when the planet is between the Sun and the Earth. → superior conjunction.

→ inferior; → conjunction.

The meridian transit of a star between the celestial pole and the north point of the horizon. Same as → lower culmination. → superior culmination.

→ inferior; → culmination.

A → statistical population consisting of individuals or items which either possesses the infinite property through some limiting process or is non-enumerable. For example, the population of all → real numbers between 0 and 1 and the population of all → integers are examples of infinite population. In case of random sampling with replacement, any population is always infinite.

→ infinite; → population.

1) General: The act of inflating; the state of being inflated.
2) Cosmology: A brief exponential expansion of the Universe postulated to have occurred 10^-35 seconds after the → Big Bang, in response to the separation of the → strong interaction from the → electroweak interaction. This idea aims at explaining the → flatness problem, the → horizon problem, and the → magnetic monopole problem. See also → inflaton field.

Verbal noun of → inflate.

A class of → Big Bang models of the Universe that include a finite period of accelerated expansion in their early histories. Such an event would have released enormous energy, stored until then in the vacuum of space-time. The horizon of the Universe expanded, temporarily, much faster than the speed of light. → inflaton field.

Inflationary, adj. of → inflation; → model.

A change in the form of a word to indicate a change in such grammatical features as tense, person, gender, case, number, voice, or mood. A general term for → declension and → conjugation.

Verbal noun of → inflect.

A point on a → curve at which the → tangent changes direction, from rotating in one sense to rotating in the opposite sense.

→ inflection; → point.

Of, relating to, or characterized by the use of → inflection, e.g. → inflectional affix.

→ inflection + → -al.