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

The current geologic era on Mars that began around 2 billion to 3 billion years ago. It is characterized by lower geologic activity such as volcanism and only occasional releases of underground water. A dry environment with a very thin atmosphere in which water can only exist as a solid or a gas, not as a liquid. → Noachian era; → Hesperian era.

Named for the young lava-covered plains called Amazonia Planitia. → era.

A hard translucent yellow, orange, or brownish-yellow fossil resin. Amber becomes negatively charged when rubbed with wool, because it attracts negative charges (electrons) and will take them from wool.

M.E. ambre, from O.Fr., from L. ambra, ambar, from Ar. 'anbar "ambergris, amber," from Mid.Pers. ambar, → ambergris.

Kahrobâ, from kah "straw" + robâ "attractor." The first component kah, kâh "straw, hay," from Mid.Pers. kâh "chaff, straw;" cf. Pali kattha- "a piece of wood;" Skt. kastha- "stick;" Gk. klados "twig;" O.Ir. caill "wood;" P.Gmc. *khulto-; Ger. Holz "wood;" E. holt; PIE *kldo-. The second component robâ, from robudan "to attract, to grab, rob;" Av. urūpaiieinti "to cause racking pain(?);" cf. Skt. rup- "to suffer from abdominal pain," rurupas "to cause violent pain," ropaná- "causing racking pain," rópi- "racking pain;" L. rumpere "to break;" O.E. reofan "to break, tear." In Arabic kahrobâ, a loanword from Persian, is used as equivalent for electricity.

A wax-like, ash-colored, strongly scent substance present in the intestines of → whales and found in seas or cast ashore. Used in perfumery.

From M.Fr. ambre gris "gray amber," → gray; → amber.

Anbar "ambergris," from Mid.Pers. ambar.

Both, on both sides.

L. ambi "around, about," akin to Gk. amphi "around, about," Skt. abhi "on both sides," Av. aibi, aiwi, O.Pers. aiby "to, against, in addition to," Mid.Pers. aw-, ab-, Mod.Pers. af- (as in afzudan "to increase, add," afruxtan "to inflame, kindle, blaze," afqân "lamentation, groaning, cires for help"); O.H.G. umbi, O.E. ymb(e); PIE *ambhi- "around".

Ubâ- from O.Pers./Av. uba- (variants uva-, ava-, va-) "both," Skt. ubha "both," PIE *ubho(u); cf. Gk. ampho, L. ambo, Goth. bai, O.H.G. beide, Slav. oba, Lith. abhu.

The quality of state of being → ambiguous.

→ ambiguous; → -ity.

Having more than one possible interpretation or meaning.

From L. ambiguus "having double meaning; doubtful," from ambigere "to be uncertain," from → ambi- "both; around" + agere "to drive, lead," → act; cf. Av. az- "to drive, lead;" Pers. niyâz "need, want, misery,"

Ubâznâk, from ubâz, literally "having double directions," from ubâ, → ambi-, + âz, from Av. az- "to lead, direct, drive," → act, + -nâk adj. suffix.

1) Applying equally to both positive and negative ions.
2) Operating in two opposite directions simultaneously. → bipolar.

Ambipolar, from → ambi- + → polar.

A physical process which allows a → molecular cloud to decouple from → interstellar magnetic field in order to undergo → gravitational collapse. A cloud of pure molecular gas would form stars very fast through collapse since neutral matter does not respond to the magnetic field. However, the magnetic field holds up a collapse because the ions present in the cloud collide with the neutrals and tie them to the field. The collapse can then only proceed if the magnetic field can be separated from the gas. In denser molecular cores the ionization degree decreases substantially and therefore neutrals and ions decouple.

→ ambipolar; → diffusion.

A defect of vision due to abnormal development, without detectable organic lesion of the eye.

From Gk. amblyopia "dim-sightedness," from amblys "dulled, blunt" + ops, → eye.

Tambalcašmi, literally "eye laziness," from tambal "lazy" + cašm, → eye.

An artificially produced → radioactive→ chemical element; symbol Am. → Atomic number 95; → atomic weight of most stable → isotope 243; → melting point about 1,175°C; → boiling point about 2,600°C; → specific gravity 13.67 at 20°C; → valence +2, +3, +4, +5, or +6. Its most stable isotope, ²⁴³Am, has → half-life of 7.4 x 10³ years.

From America, where it was first synthesized in 1944 by Glenn T. Seaborg, Ralph A. James, Leon O. Morgan, and Albert Ghiorso, who bombarded plutonium-239 with neutrons to form plutonium-241, which decays to form americium-241.

An irritating, colorless, gaseous compound of → nitrogen and → hydrogen (NH₃), which is lighter than air and readily soluble in water. It is formed in nature as a by-product of protein metabolism in animals. Ammonia is used in the preparation of many substances containing nitrogen, such as fertilizers, explosives, refrigerants, and so on.

Coined in 1782 by Swedish chemist Torbern Bergman (1735-1784) for gas obtained from ammoniac, a salt and a gum resin containing ammonium chloride found near temple of Jupiter Ammon in Libya, from Gk. ammoniakos "belonging to Ammon" (Egyptian God).

Âmoniyâk, loan from Fr.

A maser source in which excited → ammonia molecules (NH₃) produce → maser emission. The first device to demonstrate the principle of → stimulated emission of radiation used ammonia molecules (Gordon et al. 1954). The hydrogen atoms of ammonia molecules have a rotation motion whereas the nitrogen atom oscillates between two positions, above and below the plane of the hydrogen atoms. These arrangements do not represent exactly the same energy, and therefore the molecule exists in two energy states. The difference in energy between the states corresponds to a frequency of 23.87 GHz, or 1.25 cm. In astrophysics, ammonia maser emission has been detected toward active star formation regions, such as W51. → interstellar masers.

→ ammonia; → maser.

A → near-Earth asteroid (NEA) with → perihelion distances between 1.017 and 1.3 → astronomical units. The Amor asteroids approach the orbit of the Earth from beyond, but do not intersect it. Most Amors do cross the orbit of Mars. It is estimated that 32% of the total number of NEAs are Amors. One of the larger Amors is → Eros.

→ Amor; → asteroid.

Quantity; measure; the sum total of two or more quantities or sums.

From M.E. amounten "to ascend," from O.Fr. amonter, from amont "upward," from L. ad montem "to the hill," from ad "to" + mons, mont "hill," → mountain.

Masâk, from Mid.Pers. masâk "size, amount, magnitude," from mas "great, large," Av. masan "greatness, importance," from mas-; maz- "long, large; great"; cp. Skt. maha "great, mighty" (Mod.Pers. meh "great, large"), Gk. megas "great, large" L. magnus "great," PIE *meg- "great".

The → SI unit of → electric current; symbol A. It is defined by taking the fixed numerical value of the → elementary charge, e, to be 1.602 176 634 × 10^-19 when expressed in the unit → coulomb (C), which is equal to A s, where the → second (s) is defined in terms of Δν_Cs.

Named after the French physicist and mathematician André-Marie Ampère (1775-1836), one of the pioneers in studying electricity, who laid the foundation of electromagnetic theory.

One of the basic relations between → electricity and → magnetism, stating quantitatively the relation of a → magnetic field to the → electric current or changing electric field that produces it. Ampere's law states that the line integral of the magnetic field around an arbitrarily chosen path is proportional to the net electric current enclosed by the path. Also known as Ampère's theorem, Ampère's circuital law.

→ ampere; → law.

1) General: The act or result of amplifying, enlarging, or extending.
2) Physics: The process of increasing the magnitude of a variable quantity, especially the magnitude of voltage, power, or current, without altering any other quantity.

Verbal noun of → amplify.

1) Electronics: The extent to which an → analogue → amplifier boosts the strength of a → signal. Also called → gain.
2) In → gravitational lensing, the ratio of the lensed brightness to unlensed brightness. This factor depends on the mass of the → lensing object and the closeness of the alignment between observer, lens, and source (→ impact parameter).

→ amplification; → factor.

Device for reproducing an electrical input at increased intensity.

Agent noun of → amplify.

General:To make larger, greater, or more powerful.
Physics:To increase the amplitude of an input signal.

From M.F. amplifier, from L. amplificare "to increase, augmant," from L. amplus "wide, large."

Dâmané, → amplitude; dâdan "to give" (Mid.Pers. dâdan "to give," O.Pers./Av. dā- "to give, grant, yield," dadāiti "he gives;" Skt. dadáti "he gives," Gk. didomi "I give," tithenai "to put, set, place;" L. dare "to give, offer;" Rus. delat "to do;" O.H.G. tuon, Ger. tun, O.E. don "to do"); gereftan "to take, seize, catch," (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").