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.).
Fr.: machine d'Anticythère
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.
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 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.
pâdgereh (#), šekam (#)
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.
1) Of or relating to the → antipodes.
1) The exact or direct opposite.
The antiparticle of a proton, identical in mass and spin but of opposite (negative) charge.
Fr.: direction antisolaire
Meteo.: The point on the → celestial sphere that lies directly opposite the Sun from the → observer, observer, that is, on the line from the Sun through the observer. The antisolar point is the center of the rainbow, and can be easily found on a sunny day: it it located at the shadow of one's head; it is 180° away from the Sun. If the Sun is in the sky, the antisolar point is below the horizon. If the Sun has set, the antisolar point is above the horizon.
A small tail-like structure on a comet that, unlike most comet tails, seems to point toward the Sun. This rare event is an optical illusion due to larger dust particles left along the comet's orbit. And typically occurs when the Earth crosses the plane of the comet's orbit. It seen when the observer is in the plane of the cometary orbit.
Pâddom, from pâd-, → anti-, + dom "tail."
1) Of the nature of or involving → antithesis.
Fr.: Machine pneumatique
The Air Pump. A faint constellation in the southern hemisphere, at about alpha 10h, delta -35 deg. Abbreviation: Ant; genitive form: Antliae.
L. antlia "pump," from Gk. antlia "ship's hold, bilge water," from antlos.
Tolombé "pump," from Turkish tulumba "pump," from It. tromba.
Fr.: équation d'Antoine
A mathematical expression, derived from the → Clausius-Clapeyron equation, of the relation between the vapor pressure and the temperature of pure substances. It shows that the logarithm of vapor pressure is linearly dependent on the reciprocal of → absolute temperature.
Named after Louis Charles Antoine (1825-?), a French marine engineer, who derived the equation; → equation.