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hard X-rays partowhâ-ye X-e saxt (#) Fr.: rayons X durs The short wavelength, high energy end of the electromagnetic spectrum. Hard X-rays are typically those with energies greater than around 10 keV. The dividing line between hard and soft X-rays is not well defined and can depend on the context. |
hardware saxt-afzâr (#) Fr.: matériel Any physical equipment. The physical equipment comprising a computer system; opposed to → software. → hard + ware, from M.E., from O.E. waru, from P.Gmc. *waro (cf. Swed. vara, Dan. vare, M.Du. were, Du. waar, Ger. Ware "goods"). Saxt-afzâr, from saxt, → hard + afzâr "instrument, means, tool," from Mid.Pers. afzâr, abzâr, awzâr "instrument, means," Proto-Iranian *abi-cāra- or *upa-cāra-, from cāra-, cf. Av. cārā- "instrument, device, means" (Mid.Pers. câr, cârag "means, remedy;" loaned into Arm. aucar, aucan "instrument, remedy;" Mod.Pers. câré "remedy, cure, help"), from kar- "to do, make, build;" kərənaoiti "he makes" (Pers. kardan, kard- "to do, to make"); cf. Skt. kr- "to do, to make," krnoti "he makes, he does," karoti "he makes, he does," karma "act, deed;" PIE base k^{w}er- "to do, to make"). |
harmonic hamâhang (#) Fr.: harmonique (adj.) Of, pertaining to, or noting a series of oscillations in
which each oscillation has a frequency that is an integral multiple of the same basic
frequency. From L. harmonicus, from Gk. harmonikos "harmonic, musical," from harmonia "agreement, concord of sounds," related to harmos "joint," arariskein "to join together;" PIE base *ar- "to fit together." Hamâhang, "harmonious, concordant," from ham- "together, with; same, equally, even" (Mid.Pers. ham-, like L. com- and Gk. syn- with neither of which it is cognate. O.Pers./Av. ham-; Skt. sam-; also O.Pers./Av. hama- "one and the same," Skt. sama-; Gk. homos-; originally identical with PIE numeral *sam- "one," from *som-) + âhang "melody, pitch, tune; harmony, concord," from Proto-Iranian *āhang-, from prefix ā- + *hang-, from PIE base *seng^{w}h- "to sing, make an incantation;" cf. O.H.G. singan; Ger. singen; Goth. siggwan; Swed. sjunga; O.E. singan "to chant, sing, tell in song;" maybe cognate with Gk. omphe "voice; oracle." |
harmonic mean miyângin-e hamâhang Fr.: moyenne harmonique A number whose reciprocal is the → arithmetic mean of the reciprocals of a set of numbers. Denoted by H, it may be written in the discrete case for n quantities x_{1}, ..., x_{n}, as: 1/H = (1/n) Σ(1/x_{i}), summing from i = 1 to n. For example, the harmonic mean between 3 and 4 is 24/7 (reciprocal of 3: 1/3, reciprocal of 4: 1/4, arithmetic mean between them 7/24). The harmonic mean applies more accurately to certain situations involving rates. For example, if a car travels a certain distance at a speed speed 60 km/h and then the same distance again at a speed 40 km/h, then its average speed is the harmonic mean of 48 km/h, and its total travel time is the same as if it had traveled the whole distance at that average speed. However, if the car travels for a certain amount of time at a speed v and then the same amount of time at a speed u, then its average speed is the arithmetic mean of v and u, which in the above example is 50 km/h. |
harmonic motion jonbeš-e hamâhang (#) Fr.: mouvement harmonique A motion that repeats itself in equal intervals of time (also called periodic motion). |
harmonic oscillator navešgar-e hamâhang (#) Fr.: oscillateur harmonique Any oscillating particle in harmonic motion. → harmonic; → oscillator. |
harmonic progression farâyâzi-ye hamâhang Fr.: progression harmonique Math.: Any ordered set of numbers, the reciprocals of which have a constant difference between them. For example 1, ½, 1/3, ¼, ..., 1/n. Also called → harmonic sequence. → harmonic; progression. |
harmonic sequence peyâye-ye hamâhang Fr.: suite harmonique |
harmonic series seri-ye hamâhang Fr.: série harmonique Overtones whose frequencies are integral multiples of the → fundamental frequency. The fundamental frequency is the first harmonic. |
Haro galaxy kahkešân-e Hâro (#) Fr.: galaxie de Haro A type of galaxies characterized by strong emission in the blue and violet regions of the spectrum. They are often elliptical or lenticular. Named after the Mexican astronomer Guillermo Haro (1913-1988), who first compiled a sample of these objects; → galaxy. |
Harshad number adad-e Harshad Fr.: nombre Harshad A number that is divisible by the sum of its digits. For example, 18 is a Harshad number because 1 + 8 = 9 and 18 is divisible by 9 (18/9 = 2). The simplest Harshad numbers are the two-digit Harshad numbers: 10, 12, 18, 20, 21, 24, 27, 30, 36, 40, 42, 45, 48, 50, 54, 60, 63, 70, 72, 80, 81, 84, 90. They are sometimes called Niven numbers. The name Harshad was given by Indian mathematician Dattaraya Kaprekar (1905-1986) who first studied these numbers. Harshad means "joy giver" in Sanskrit, from harṣa- "joy" and da "to give," → datum. |
Hartle-Hawking initial state estât-e âqâzin-e Hartle-Hawking Fr.: état initial de Hartle-Hawking A proposal regarding the initial state of the → Universe prior to the → Planck era. This → no boundary hypothesis assumes an imaginary time in that epoch. In other words, there was no real time before the → Big Bang, and the Universe did not have a beginning. Moreover, this model treats the Universe like a quantum particle, in an attempt to encompass → quantum mechanics and → general relativity; and attributes a → wave function to the Universe. The wave function has a large value for our own Universe, but small, non-zero values for an infinite number of other possible, parallel Universes. Hartle, J., Hawking, S., 1983, "Wave function of the Universe," Physical Review D 28; → initial; → state. |
Hartmann test âzmun-e Hârtman (#) Fr.: test de Hartmann A way of testing the quality of optical systems. In this method, incident rays from a point source are isolated by small holes in an opaque screen located close to the lens or mirror under test. Photographic plates are inserted into the beam within and beyond the focal region. The black dots on the exposed plates, which reveal differences of optical focus in the various zones of the lens or mirror, are analyzed to yield the objective's figure. → Shack-Hartmann wavefront sensor. Named after the German astronomer Johannes Hartmann (1865-1936), who developed the method. → test. |
hartree hartree Fr.: hartree A unit of energy used in atomic and molecular physics; symbol Ha or E_{h}. It is defined as: 1 Ha = m_{e}e^{4}/(4ε_{0}^{2}ħ), where m_{e} is the mass of electron, e its charge, ε_{0} the → permittivity of vacuum, and ħ → reduced Planck's constant. Its value is 2 → rydbergs, or 4.3597 x 10^{-18} → joule, or 27.213 → electron-volts. Named for the British physicist and mathematician Douglas R. Hartree (1897-1958). |
Harvard classification radebandi-ye Hârvârd (#) Fr.: classification de Harvard A classification of stellar spectra published in the Henry Draper catalogue, which was prepared in the early twentieth century by E. C. Pickering and Miss Annie Canon. It is based on the characteristic lines and bands of the chemical elements. The most important classes in order of decreasing temperatures are as follows: O, B, A, F, G, K, M. Harvard, named for John Harvard (1607-1638), the English colonist, principal benefactor of Harvard College, now Harvard University. → classification |
harvest moon mâh-e xarman bardâri Fr.: lune de moisson The → full moon that appears closest in time to the → autumnal equinox. Harvest, from O.E. hærfest "autumn," from P.Gmc. *kharbitas (cf. Du. herfst, Ger. Herbst "autumn"), from PIE *(s)kerp- "to gather, pluck, harvest," from *(s)ker- "to cut" (cf. Skt. krpāna- "sword, knife;" Gk. karpos "fruit;" L. carpere "to cut, divide, pluck;" Av. karət- "to cut," Mod.Pers. kârd "knife," as below); → moon. Xarman "harvest; piled-up reaped corn," Qâyeni dialect xerma- "harvest;" Tabari kar "harvest" (karkub "corn-thresher"). Xarman may ultimately derive from Proto-Iranian *kartman-, from *kart- "to cut," cf. Av. karət- "to cut" (Skt. kart- "to cut"), karəta- "knife;" Mid.Pers. kârt "knife;" Mod.Pers. kârd + -man a common suffix (as in Av. asman "stone, sky;" rasman- "column, rank;" nāman- "name;" taoxman- "seed"). |
hatch 1) lâcidan; 2) lâceš; daricé Fr.: 1) éclore; 2) éclosion; volet 1) (of an egg) To open and produce a young animal; emerge from its egg. 1) M.E. hachen "to produce young from eggs by incubation," probably from
an unrecorded O.E *hæccan, of unknown origin, related to
M.H.G., Ger. hecken "to mate" (used of birds). 1) Lâcidan, from Tabari lâc "open, separated, wide aprat"
(lâc hâytan "to split, to crack," lâc bazoən "to split,
to tear"), may be from Proto-Ir. *rauj "to break, burst;"
cf. Av. (+*fra-) fra.uruxti- "destruction;" Khotanese *rrus-
"to burst, break;" Baluchi ruj- "to break open;" Bartangi, Oroshori
ruj-/ruxt- "to dig;" Skt. roj- "to break, break open;"
Pali luki- "part;" L. lugere "to mourn, grieve;"
Armenian lucanem "I break up." |
Haumea Haumea Fr.: Hauméa A → dwarf planet located beyond → Neptune's orbit (→ trans-Neptunian object). Haumea is roughly the same size as → Pluto. It spins on its axis once every four hours, making it the fastest spinning known large object in the → solar system. It has two known moons, called Hi'aka and Namaka. Named for the Hawaiian goddess of childbirth and fertility. Its moons are named for daughters of Haume |
Hawking radiation tâbeš-e Hawking (#) Fr.: rayonnement de Hawking The radiation produced by a → black hole when → quantum mechanical effects are taken into account. In the intense gravitational field generated by a black hole, → virtual particles can "borrow" energy from their surroundings and temporarily become real. They manifest themselves in pairs of particles and → antiparticles. One particle is sometimes consumed by the black hole while the other escapes. The escaping particle carries away a tiny fragment of the black hole's mass, the extra energy that allowed it to become real. Over long periods of time, the black hole will eventually evaporate, losing all of its energy to escaping particles. See also → Bekenstein formula, → Hawking temperature. Named after the British physicist Stephen Hawking, born 1942, who provided the theoretical argument for the existence of the radiation in 1974; → radiation. |
Hawking temperature damâ-ye Hawking Fr.: température de Hawking The temperature inferred for a → black hole based on the → Hawking radiation. For a → Schwarzschild black hole, one has T_{H} = ħc^{3}/(8πGMk) where ħ is the → reduced Planck's constant, c is the → speed of light, G is the → gravitational constant, M is the mass, and k is → Boltzmann's constant. The formula can be approximately be written as: T_{H}≅ 6.2 x 10^{-8} (Msun/M) K. Thus radiation from a solar mass black hole would be exceedingly cold, about 5 x 10^{7} times colder than the → cosmic microwave background. Larger black holes would be colder still. Moreover, smaller black holes would have higher temperatures. A → mini black hole of mass about 10^{15} g would have T_{H}≅ 10^{11} K. → Hawking radiation; → temperature. |
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