An Etymological Dictionary of Astronomy and Astrophysics
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Statistics: The correlation coefficient of two random variables X and Y is in general defined as the ratio of the Cov(X,Y) to the two standard deviations of X and Y. It varies between 1 and -1 corresponding to complete correlation or anticorrelation.

Anticorrelation, from → anti- + → correlation.

Pâdhambâzâneš, from pâd-, → anti-, + hambâzâneš, → correlation.

Rays of → sunlight that appear to converge at the → antisolar point. Like → crepuscular rays, they are parallel beams of sunlight from holes in the clouds, and their apparently odd directions are a perspective effect.

→ anti-; → crepuscular rays.

Meteo.: A weather phenomenon associated with atmospheric high pressure. In the Northern Hemisphere an anticyclone rotates in the clockwise direction. The rotation is caused by the movement of colder higher pressure air that is moving away from the poles toward the equator being affected by the rotation of the Earth.

→ anti-; → cyclone.

Having a sense of rotation about the local vertical opposite to that of the Earth's rotation. In other words, → clockwise in the Northern Hemisphere, → counterclockwise in the Southern Hemisphere, and undefined at the equator. The opposite of → cyclonic (Meteorology Glossary, American Meteorological Society).

→ anticyclone; → -ic.

The function F(x) is called the antiderivative of the function f(x) on the interval [a,b] if at all points of this interval F'(x) = f(x). Same as primitive.

→ anti- + → derivative.

Karyâ, → function; noxostin "primitive," → first.

A property possessed by some → metals, → alloys, and salts of transition elements in which there is a lack of → magnetic moment due to the antiparallel or spiral arrangement of atomic → magnetic moments.

→ anti- + → ferromagnetism.

An atom made from an → antiproton and a → positron. In 2010 a research collaboration at CERN combined decelerated antiprotons with positrons to produce antihydrogen atoms. They managed 38 times to confine single antihydrogen atoms in a magnetic trap for more than 170 milliseconds (Andersen et al. 2010, Nature, 17 Nov.).

→ anti- + → hydrogen.

A unique Greek geared device, constructed around the end of the second century BC to display the movement of the Sun, the Moon, and possibly the planets around the Earth, and predict the dates of future eclipses. It measures about 32 by 16 by 10 cm and contains at least 30 interlocking gear-wheels, all of them having triangular teeth, from 15 to 223 in number. This device is one of the most stunning artefacts remained from antiquity, revealing an unexpected degree of technical creativity for the period. Nothing close to its technological sophistication appears again for well over a millennium, when astronomical clocks appear in the medieval Europe. It was discovered in 1901 in a sunken ship just off the coast of Antikythera, an island between Crete and the Greek mainland. Its significance and complexity were not understood until decades later. After lots of study involving several research fields, a copy of the device has recently been constructed. See, e.g., Freeth et al. 2006, Nature 444, 587.

Named after the Greek island in the Ionia Sea from which the fragments of the device were discovered in 1901 by sponge divers, who found a sunken Roman ship. Several pieces of evidence indicate that the Roman ship carrying the device wrecked sometime shortly after 85 BC. The ship also contained an enormous booty of bronzes, glassware, jewelry and pottery; → mechanism.

Matter composed entirely of → antiparticles. See also → antihydrogen.

Antimatter from Gk. → anti- "opposite, opposing, against" + → matter.

Pâdmâddé from pâd-, → anti-, + mâddé, → matter.

A silver white metallic element of a flaky nature, extremely brittle, occurring in nature free or combined, symbol Sb. → Atomic number 51; → atomic weight 121.75; → meting point 630.74°C; → boiling point 1,750°C; → specific gravity (metallic form) 6.69 at 20°C. Antimony is recognized in compounds from antiquity, and as a metal since the 17th century. The minerals stibnite (Sb₂S₃) and stibine (SbH₃) are two of a multitude of mineral species which were known in the ancient world. Antimony is a poor conductor of heat and electricity. It greatly increases the hardness of metals with which it makes → alloys. Its various unstable isotopes have a half-life of 16 min (Sb¹²⁰) to 2.7 years (Sb¹²⁵).

From M.E. antimonie, from M.L. antimonium, an alchemist's term, of obscure origin, maybe a Latinization of Gk. stimmi or stibi, probably ultimately from Egyptian stm "cosmetic powder" used to paint the eyelids. The chemical symbol, Sb, comes from the original name, stibium, which is derived from Gk. stibi for "mark," since it was used for blackening eyebrows and eyelashes. The name was changed from stibium to antimonium to antimony.

Ântimuân, loan from Fr. antimoine.

The → antiparticle counterpart of the → neutrino.

→ anti-; → neutrino.

The → antiparticle of the → neutron. It has the same mass, → spin, and → electric charge (zero) as the neutron but has opposite → baryon number (+1 for neutron, -1 for the antineutron). This is because the antineutron is composed of → antiquarks, while neutrons are composed of → quarks. The antineutron consists of one up antiquark and two down antiquarks.

→ anti-; → neutron.

The position of maximum → amplitude midway between two adjacent → nodes in a → standing wave.

→ anti-; → node.

A unique → binary asteroid (90) which has two similar-sized components. The components, 91 and 86 km in diameter respectively, are separated by 171 km, and circle each other every 16.5 hours. Belonging to the main → asteroid belt, Antiope was discovered in 1866 by the German Robert Luther. Its binarity was discovered in 2000 by W. Merline and collaborators.

Antiope, from Gk. mythology, but it is not clear whether Antiope the Amazon or Antiope the mother of Amphion and Zethus.

A → pair of → vectors whose directions are parallel but having the opposite sense.

→ anti-; → parallel.

Any → elementary particle with a → charge of opposite sign to the same particle in normal matter.

→ anti- "opposite, opposing, against" + → particle.

1) Of or relating to the → antipodes.
2) Describing two points when a line drawn from one to the other does not pass through the geometric centre of the Earth.

→ antipode; → -al.

1) The exact or direct opposite.
2) Either or both of two points, places, or regions that are situated diametrically opposite to one another on the Earth's surface (Dictionary.com).

M.E., from L., from Gk. antipod-, antipous, literally "with feet opposite," from → anti- "against," + pod-, pous, → foot.

Pâdpây, from pâd-, → anti-, + pây, → foot.

The antiparticle of a proton, identical in mass and spin but of opposite (negative) charge.

From → anti- + → proton.

The → antiparticle of a → quark.

→ anti-; → quark.