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

A soft, usually white fibrous substance like fine wool surrounding the seeds of various tropical and subtropical plants of the mallow family. It is extensively used in making threads, yarns, and fabrics.

M.E. coton, from O.Fr. coton, from O.It. cotone, from Ar. qutn (قطن), perhaps of Egyptian origin.

Panbé "cotton" (dialectal Lori pamma, Kurd. pemû, maybe Tajik, Afqân pakta, pakhta, bakhta, bakta), from Mid.Pers. pambag "cotton," pambagin "made of cotton," perhaps loaned in Gk. bombux "silk, any silk-like fine fiber;" L. bombyx "silk, cotton," L.L. bombax "cotton," hence O.Fr. bombace "cotton, cotton wadding," E. bombast "cotton wool; inflated language."

A particle → collision where the dominant force is described by → Coulomb's law. The collision results in deflections of the particles away from their initial paths.

→ coulomb; → collision.

The transition to a higher → energy level than → ground state undergone by an atomic nucleus when a → charged particle of appropriate energy moves past it.

→ coulomb; → excitation.

The reciprocal force between two or more → charged particles according to → Coulomb's law.

→ coulomb; → interaction.

In nuclear physics, a constant that indicates a measure of how strongly two particles interact.

→ coupling; → constant.

A chemical bond between two atoms of the same or different elements, in which each atom contributes one electron to be shared in a pair.

Covalent, adj. of → covalence; → bond.

1) The act of producing or causing to exist.
2) The act of being created. See also → creation operator.

Verbal noun of → create.

An operator that acts on the → eigenstate describing the → harmonic oscillator to raise its → energy level by one step. The creation operator is the → Hermitian conjugate operator of the → annihilation operator.

→ creation; → operator.

The religious belief that considers the account of creation given in Genesis to be a scientific description and rejects the Big Bang theory and the theory of evolution. Creationism is a → pseudoscience. Same as "creation science" and "scientific creationism."

→ creation; → -ism.

The first sighting of the → New Moon after its → conjunction with the Sun. Although the date and time of each New Moon can be computed exactly, the visibility of the lunar → crescent as a function of the → Moon's age depends upon many factors and cannot be predicted with certainty. The sighting within one day of New Moon is usually difficult. The crescent at this time is quite thin, has a low surface brightness, and can easily be lost in the → twilight. Generally, the lunar crescent will become visible to suitably-located, experienced observers with good sky conditions about one day after New Moon. However, the time that the crescent actually becomes visible varies from one month to another. The visibility depends on sky conditions and the location, experience, and preparation of the observer. Ignoring atmospheric conditions, the size and brightness of the lunar crescent depend on the → elongation which in turn depends on several factors: 1) The Moon's elongation at New Moon (the elongation of the Moon at New Moon is not necessarily 0). 2) The speed of the Moon in its elliptical orbit. 3) The distance of the Moon, and 4) The observer's location (parallax). The combined effect of the first three factors gives geocentric elongation of the Moon from the Sun at an age of one day which can vary between about 10 and 15 degrees. This large range of possible elongations in the one-day-old Moon is critical (US Naval Observatory).

→ crescent; → moon; → visibility.

The → mass extinction event that destroyed the dinosaurs and a majority of other species on Earth approximately 65 million years ago. This event is believed to have been the impact of a 10 km-size → asteroid or → comet nucleus and its aftereffects, including a severe → impact winter. The collision would have released the energy equivalent to 100 million megatonnes (teratonnes) of → TNT, i.e. more than 10⁹ times the energy of the atomic bomb dropped on Hiroshima on August 6, 1945. Same as the → Cretaceous-Tertiary event.

→ Cretaceous; → Paleogene; → extinction; → event.

A standard or rule that can serve as basis for a judgment or decision.

From Gk. kriterion "means for judging, standard," from krites "judge," from krinein "to separate, distinguish, judge." L. cribrum "sieve" *krei- "to sieve, discriminate, distinguish."

Sanjidâr verbal noun from sanjid- past tense stem of sanjidan "to compare; to measure" (Mid.Pers. sanjidan "to weigh," from present tense stem sanj-, Av. θanj- "to draw, pull;" Proto-Iranian *θanj-) + suffix -âr.

The upper value of mass that a → Bonnor-Ebert sphere must have in order that → hydrodynamic equilibrium be maintained. This → critical mass is given by: M_crit = 1.18 (a⁴/G^3/2)P_ext^-1/2, where a = (kT/m)^1/2 is the isothermal → sound speed inside the sphere, G is the → gravitational constant, and P_ext the pressure of the external medium (see, e.g., F. H. Shu, 1977, ApJ 214, 488).

→ critical; → Bonnor-Ebert mass.

In radio astronomy, the process performed by a → cross correlator or the result of the process.

→ cross; → correlation.

Dispersion of a light beam by using two dispersing elements (grating, grism), one for separating spectral orders, the other for resolving spectral features within an order.

→ cross; → dispersion.

The identification of an object in a data base or catalog and matching it with the same object identified in another catalog.

→ cross; → identification.

1) Math: The intersection of a plane with a geometric figure, usually at right angles to an axis of symmetry.
2) Physics: A quantity that expresses the effective area that a given particle presents as a target to another incident particle, giving a measure of the probability that the incident particle will induce a particular atomic or nuclear reaction. Also called collision cross section. The cross section has the dimensions of a surface. In nuclear and particle physics, the commonly used units for the cross section are the barn and cm².

In classical mechanics, the cross section for the collision of a point particle with a hard sphere is just be the surface of a section through the middle of the sphere. This explains the name "cross section." → cross; → section.

A process by which a homogeneous solution becomes crystal.

Noun from crystallize, → crystal.

Noun from bolur, from verb boluridan "to crystallize" + verbal noun suffix -eš.

An equation containing unknowns of the third power; the general form: ax³ + bx² + cx + d = 0.

Cubic, of or pertaining to → cube; → equation.

A function defined by a → polynomial of → degree three. Its generalized form is: f(x) = ax³ + bx² + cx + d, where a, b, c and d are constants, and a≠ 0.

→ cubic; → function.