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

The ratio of an amount of heat, dQ, transferred to a body in some process to the corresponding change in the temperature of the body: C = dQ/dT. The heat capacity depends upon the mass of the body, its chemical composition, thermodynamic state, and the kind of process employed to transfer the heat. The word "capacity" may be misleading because it suggests the essentially meaningless statement "the amount of heat a body can hold," whereas what is meant is the heat added per unit temperature rise. → specific heat.

→ heat; → capacity.

A type of → heat transfer by means of molecular agitation within a material without any motion of the material as a whole.

→ heat; → conduction.

A type of → heat transfer involving mass motion of a fluid such as air or water when the heated fluid is caused to move away from the source of heat, carrying energy with it.

→ heat; → convection.

Assuming that the Universe is a thermodynamically → isolated system, a state of absolute uniformity in the Universe in which all temperature differences would reduce to zero and no energy will be available for use, according to the → second law of thermodynamics. In that condition of maximum → entropy, the Universe would be in a state of unchanging death. First introduced by the German physicist Hermann von Helmholtz (1821-1894) in 1854, on the basis of William Thomson's (1824-1907) idea.

→ heat; → death; → Universe.

The amount of heat energy required to transform an amount of a substance from the liquid phase to the gas phase. → molar heat of vaporization.

→ heat; → vaporization.

A structure that protects against excessive heat, especially that which covers the vulnerable surfaces of a → spacecraft and protects it when re-entering the Earth's atmosphere.

→ heat; → shield.

The spontaneous transportation of heat through matter, from a region of higher temperature to a region of lower temperature.

→ heat; → transfer.

Meteorology: A period of several successive days of abnormally hot and usually humid weather occurring in summer.

→ heat; → wave.

Celle-ye tâbestân literally "the fortieth of summer," i.e. "midsummer," from cellé pertaining to "forty (days)," from cel, cehel, → forty, + tâbestân, → summer.

1) The process whereby a system's temperature increases. → warming.
2) A device or system for supplying heat, especially central heating, to a building; the heat supplied.

→ heat; → -ing.

The sky or Universe as seen from the Earth; the firmament. Often used in the plural.

From M.E. heven, O.E. heofon, possibly from P.Gmc. *khemina- (cf. M.L.G. heben, O.N. himinn, Goth. himins, Du. hemel, Ger. Himmel "heaven, sky"); PIE base *kem-/*kam- "to cover."

Âsmân, from Mid.Pers. âsmân "sky, heaven;" O.Pers. asman- "heaven;" Av. asman- "stone, sling-stone; heaven;" cf. Skt. áśman- "stone, rock, thunderbolt;" Gk. akmon "heaven, meteor, anvil;" Akmon was the father of Ouranos (Uranus), god of sky; Lith. akmuo "stone;" Rus. kamen; PIE base *akmon- "stone, sky." The link between the "stone" and "sky" concepts indicates that the sky had once been conceived as a stone vault by prehistoric Indo-Europeans.

→ astronomical object.

→ heaven; → -ly; → body.

→ Kennelly-Heaviside layer.

English physicist Oliver Heaviside (1850-1925).

Of great weight; of great amount, quantity.

M.E. hevi; O.E. hefig, from P.Gmc. *khabigas (cf. O.N. hebig).

Sangin "heavy, weighty; stony, like stone, hard," from sang "stone, rock" (Mid.Pers. sang; O.Pers. aθanga-; Av. asenga- "stone" (related to Mod.Pers. âsmân "sky" → heaven); PIE *aken-) + -in adj. suffix.

In astrophysics, any → chemical element heavier than → helium. Such elements are also inappropriately referred to as "→ metals."

→ heavy; → element.

→ deuterium.

→ heavy; → hydrogen.

Water in which the hydrogen is replaced by → deuterium. Deuterium Oxide (D₂O).

→ heavy; → water.

A → lunisolar calendar used by Jews for religious purposes. The year consists of 12 months alternating between 29 and 30 days, making a year of 354 days. In order to conform to the → solar year, a → leap month is included every third year. A month begins the day the new moon is first seen. The years are counted from the time of "creation," believed by Jewish theologians to have occurred in the year 3761 B.C. Also called → Jewish calendar.

Hebrew, from O.E., from O.Fr. Ebreu, from L. Hebraeus, from Gk. Hebraios, from Aramaic 'ebhrai, corresponding to Heb. 'ibhri "an Israelite," literally "one from the other side," in reference to the River Euphrates, or perhaps simply denoting "immigrant;" from 'ebher "region on the other or opposite side;" → calendar.

Gâhšomâr, → calendar; yahud→ Jewish calendar.

A prefix meaning hundred (10²) used in the formation of compound words.

From Fr., from Gk. hekaton "hundred."

Hekto-, loanword from Fr., as above.

Distance upward from a given level to a fixed point.

M.E., from O.E. hiehthu; → high + -th a suffix forming nouns of action (e.g., birth) or abstract nouns denoting quality or condition (depth; length; warmth).

Bolandi, bolandâ "height," noun forms from boland "high," variants bâlâ "up, above, high, elevated, height," borz "height, magnitude" (it occurs also in the name of the mountain chain Alborz), Lori dialect berg "hill, mountain;" Mid.Pers. buland "high;" O.Pers. baršan- "height;" Av. barəz- "high, mount," barezan- "height;" cf. Skt. bhrant- "high;" L. fortis "strong" (Fr. & E. force); O.E. burg, burh "castle, fortified place," from P.Gmc. *burgs "fortress;" Ger. Burg "castle," Goth. baurgs "city," E. burg, borough, Fr. bourgeois, bourgeoisie, faubourg); PIE base *bhergh- "high."
Farâzâ, noun of farâz "above, up, upon, on the top, aloft," from Mid.Pers. farâz, farâc "forward, prominent, distinguished;" Av. frānk- (adj.) "turned toward the front," fraca (adv.) "forward, forth," fraš (adv.) "forward, forth; before;" Proto-Iranian *frānk-.

A diffuse bright region surrounding the shadow that an observer's head casts on an irregular surface. It can be best observed on dewy reeds or grass. This phenomenon is reminiscent of the → glory, but without its color and regular structure.

Heiligenschein, Ger., literally "saint's shining light," from heiligen, from heilig "holy, sacred" (P.Gmc. *khailagas; M.H.G. heilec; O.H.G. heilag; Goth. hailag; O.N. heilagr; O.E. halig; E. holy) + Schein "glow, shine" (M.H.G. schinen, O.H.G. skinan, P.Gmc. *skinanan; E. shine; cf. Mod.Pers. sâyé "shadow;" Mid.Pers. sâyak "shadow;" Av. a-saya- "throwing no shadow;" Skt. chāya- "shadow;" Gk. skia "shade;" Rus. sijat' "to shine;" PIE base *skai- "bright").

Sepant foruq, from sepant "holy" (Mid.Pers. spand "holy," Spandarmat "Holy Thought; 5-th day of the month; 12-th month of the year;" from Av. spənta- "holy; beneficent," spəntô.mainyav- "coming from or belonging to the holy spirit," spəntô.təma- "holiest") + foruq "light, brightness" (related to rôšan "light; bright, luminous;" ruz "day," afruxtan "to light, kindle;" Mid.Pers. payrog "light, brightness," rošn light; bright," rôc "day;" O.Pers. raucah-; Av. raocana- "bright, shining, radiant," raocah- "light, luminous; daylight;" cf. Skt. rocaná- "bright, shining, roka- "brightness, light;" Gk. leukos "white, clear;" L. lux "light" (also lumen, luna; E. light, Ger. Licht, and Fr. lumière; PIE base *leuk- "light, brightness").