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

An → inflection that is added at the end of a root word. In English there are eight inflectional affixes, which are all suffixes. They always follow derivational suffixes and do not change the category of a word.

→ inflectional + → affix.

1) Knowledge gained through study, communication, research, instruction, etc.
2) Knowledge communicated or received concerning a particular fact or circumstance; news.
3) The act or fact of informing.
4) A sequence of signals that conveys a message to a receiver. Information does not exist on its own. It is contained within something and is coded. The notion of information involves → uncertainty and → randomness; hence the necessity for calling on → probability theory and → statistics.
See also: → information content, → information entropy, → information flow, → information paradox, → information science, → information technology, → information theory, → infosphere, → quantum information, → entropy.

Verbal noun of → inform.

The → negative of the → logarithm of the → probability that a particular → message or → symbol will be emitted by a → source.

→ information; → content.

The measure of information, which is usually expressed by the average number of bits needed for storage or communication. In other words, the degree to which the values of a → random variable X are dispersed. If the → probability density function of X is P(x), the entropy is defined by: H(X) = -Σ P(x) log P(x). Also called → Shannon entropy.

→ information; → entropy.

The flow of data into a system or to the end users.

→ information; → flow.

A paradox raised in 1976 by S. Hawking (1942-2018) whose analysis of the thermodynamic properties of → black holes led him to the prediction that black holes are not in fact black, but radiate due to quantum effects. This implied that, due to the → Hawking radiation, a black hole would eventually evaporate away, leaving nothing. This deduction presented a problem for → quantum mechanics, which maintains that information can never be lost. This topic is a matter of intense debate. Many solutions have been proposed, but all of them have serious drawbacks. In order to analyze better these solutions one needs a quantum gravity theory, which does not exist at the moment. In brief, either the idea of → quantum unitarity must be given up, or a mechanism should be found by which information is not lost after it falls into a black hole.

→ information; → paradox.

Same as → informatics.

→ information; → science.

The science and activity of receiving, storing, processing, and transmitting information by using → computers.

→ information; → technology.

The mathematical theory that defines, quantifies, and analyzes the concept of → information. It involves → probability theory in → transmission of → messages when the → bits of information are subject to various distortions. Its goal is to enable as much information as possible to be reliably stored on a medium, retrieved, or communicated.
See also:
→ information content, → information entropy, → information flow, → information paradox, → information science, → information theory, → quantum information, → entropy.

→ information; → theory.

The portion of → electromagnetic radiation from → astrophysical objects in → infrared frequencies.

→ infrared; → emission.

That part of the → electromagnetic radiation lying beyond the red, between the radio and the visible regions of the → electromagnetic spectrum. The wavelengths range from about 0.8 → microns (μm) to about 1000 μm. See also: → near-infrared; → mid-infrared; → far-infrared; → submillimeter radiation.

→ infrared; → radiation.

1) Conditions at an initial time t = t₀ from which a physical system or a given set of mathematical equations evolves.
2) Meteo.: A prescription of the state of a → dynamical system at a specified time; for all subsequent times, the → equation of motion and → boundary conditions determine the state of the system.

→ initial; → condition.

A mathematical expression describing the relative number of stars found in different ranges of mass for a cluster of stars at the time of its formation. It is defined as φ(log M) = dN / dlog M ∝ M ^-Γ, where M is the mass of a star and N is the number of stars in a logarithmic mass interval. The value of the slope found by Salpeter (1955) for → low-mass and → intermediate-mass stars in the → solar neighborhood is Γ = 1.35. The IMF can be expressed also in linear mass units: χ(M) = dN / DM ∝ M ^-α. Note that χ(M) = (1 / M lm 10) φ(log M), and α = Γ + 1. In this formalism the Salpeter slope is α = 2.35. There is a third way for representing the IMF, in which the exponent is x = -α. The IMF is not a single power law over all masses, from → brown dwarfs to → very massive stars (Kroupa, 2002, Science 295, 82). Different slopes have been found for different mass segments, as follows: α = 1.3 for 0.08 ≤ M_solar < 0.5; α = 2.3 for 0.5 ≤ M_solar < 1; α = 2.3 for 1 ≤ M_solar. The IMF at low masses can be fitted by a → lognormal distribution (See Bastian et al., 2010, ARAA 48, 339 and references therein). See also → canonical IMF.

→ initial; → mass; → function.

1) General: The act of injecting. Something that is injected.
2) Physics: The process of introducing electrons or holes into a semiconductor so that their total number exceeds the number present at thermal equilibrium. → hole injection.
3) Math.: A one-to-one → mapping. In other words, a mapping from a → set A onto a set B such that for every element in B there is at the most an element in A.

Verbal noun of → inject.

1) Something inscribed; the act of inscribing.
2) The entering of a name on or as if on a list.
3) A historical or religious text carved on stone, brick, or other hard surface.
4) A brief dedication, as of a book or a work of art.

Verbal noun of → inscribe.

The act or process of inseminating.

Verbal noun of → inseminate; → -tion.

A NASA lander designed to study the interior of the planet Mars. It will be a stationary mission, in contrast to NASA's famous Opportunity, Spirit and Curiosity rovers. Staying in place is necessary for its major science goals, which include learning more about the Martian composition, and how tectonically active the red planet is. InSight launched toward Mars on May 5, 2018, landed on Nov. 26, 2018, at the Martian Elysium Planitia, an equatorial zone just south of an ancient volcanic area. InSight will send back data about Mars' interior for about 1 Mars year, or 728 Earth-days. The lander uses sophisticated instruments, to delve deep beneath the surface and seek the fingerprints of the processes that formed the terrestrial planets. It does so by carrying out → seismology, heat flow measurements, and precision tracking.

InSight, short for Interior Exploration using Seismic Investigations, Geodesy and Heat Transport; → mission.

The amount of radiative energy received from the Sun per unit area per unit time.

Insolation, from L. insolatus p.p. of insolare "to place in the sun," from → in- + sol, → sun, + -ation a suffix denoting action or condition.

Xortâbgiri, from xor "sun," cognate with L. sol→ sun + tâb "light; heat, warmth; illuminating," from tâbidan, tâftan "to shine," tafsidan "to become hot" (Av. tāp-, taf- "to warm up, heat," tafsat "became hot," tāpaiieiti "to create warmth;" cf. Skt. tap- "to spoil, injure, damage; to suffer; to heat, be/become hot," tapati "burns;" L. tepere "to be warm," tepidus "warm;" PIE base *tep- "warm") + giri verbal noun of gereftan "to take, seize" (Mid.Pers. griftan, Av./O.Pers. grab- "to take, seize," cf. Skt. grah-, grabh- "to seize, take," graha "seizing, holding, perceiving," M.L.G. grabben "to grab," from P.Gmc. *grab, E. grab "to take or grasp suddenly;" PIE base *ghrebh- "to seize").

1) The act of inspecting or viewing, especially carefully or critically.
2) Formal or official viewing or examination (Dictionary.com).

Verbal noun of → inspect.

1) Something installed, as machinery or apparatus placed in position or connected for use.
2) The act of installing.
3) The fact of being installed (Dictionary.com).

→ install; → -tion.