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

1) The act or process of correcting.
2) A quantity added to a calculated or observed value to obtain the true value.
3) Something that is substituted or proposed for what is wrong or inaccurate.

Noun form of → correct.

General: The degree to which two or more attributes or measurements on the same group of elements show a tendency to vary together; the state or relation of being correlated.
Statistics: The strength of the linear dependence between two random variables.

From M.Fr. corrélation, from cor- "together," → com- + → relation.

Hambâzâneš , from ham-→ com- + bâzâneš→ relation.

A number between -1 and 1 which measures the degree to which two variables are linearly related.

→ correlation; → coefficient.

→ accelerating Universe.

→ cosmic; → acceleration.

→ cosmic microwave background radiation (CMBR).

→ cosmic; → background; → radiation.

Same as the → Layzer-Irvine equation.

→ cosmic; → energy; → equation.

Same as the → expansion of the Universe.

→ cosmic; → expansion.

The polarization of the → cosmic microwave background radiation due to → Thomson scattering by → free electrons during the → recombination era. The polarization can greatly enhance the precision with which the parameters associated with → acoustic oscillations are derived; because it carries directional information on the sky. When an → electromagnetic wave is incident on a free electron, the scattered wave is polarized perpendicular to the incidence direction. If the incident radiation were → isotropic or had only a → dipole variation, the scattered radiation would have no net polarization. However, if the incident radiation from perpendicular directions (separated by 90°) had different intensities, a net → linear polarization would result. Such → anisotropy is called → quadrupole because the poles of anisotropy are 360°/4 = 90° apart.

→ cosmic; → microwave; → background; → polarization.

The diffuse → electromagnetic radiation in the → microwave band, coming from all directions in the sky, which consists of relic photons left over from the very hot, early phase of the → Big Bang. More specifically, the CMBR belong to the → recombination era, when the → Universe was about 380,000 years old and had a temperature of about 3,000 K, or a → redshift of about 1,100. The photons that last scattered at this epoch have now cooled down to a temperature of 2.73 K. They have a pure → blackbody spectrum as they were at → thermal equilibrium before → decoupling. The CMB was discovered serendipitously in 1965 by Penzias and Wilson (ApJ L 142, 419) and was immediately interpreted as a relic radiation of the Big Bang by Dicke et al. (1965, ApJL 142, 383). Such a radiation had been predicted before by Gamow (1948, Nature 162, 680) and by Alpher and Herman (1948, Nature 162, 774). This discovery was a major argument in favor of the Big Bang theory. In 1992, the satellite → Cosmic Background Explorer (COBE) discovered the first anisotropies in the temperature of the CMB with an amplitude of about 30 µK. See also: → cosmic microwave background anisotropy, → dipole anisotropy, → CMB lensing, → CMB angular power spectrum, → acoustic peak, → baryon acoustic oscillation, → WMAP.

→ cosmic; → microwave; → background; → radiation.

A crucial period in the history of the → Universe, when the bulk of stars in massive galaxies were likely formed. Observations of young stars in distant galaxies at different times in the past have indicated that the → star formation rate peaked at the → redshift of z ~ 2, some 10 billion years ago, before declining by a factor of around ten to its present value (P. Madau & Dickinson, 2014, arXiv:1403.0007).

→ cosmic; → star; → formation; → peak.

The ionization of → interstellar medium (ISM) gas by → cosmic rays. Cosmic rays are a primary source of ionization, competing with stellar → ultraviolet photons and → X-rays produced by embedded → young stellar objects. Cosmic rays play a key role in the chemistry and dynamics of the interstellar medium. The ionization fraction in turn drives the chemistry of → molecular clouds and controls the coupling of the gas with the Galactic → magnetic field. Moreover, cosmic rays represent an important source of → heating for → molecular clouds because the energy of primary and secondary electrons produced by the ionization process is in large part converted into heat by → inelastic collisions with ISM atoms and → molecules (see, e.g., Padovanit et al., 2009, arXiv:0904.4149).

→ cosmic; → ray; → ionization.

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.

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 → 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.

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

→ cross; → correlation.