An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 24 Search : thesis
ad hoc hypothesis
  انگاره‌ی ِ پدیم   
engâre-ye pad im

Fr.: hypothèse ad hoc   

Addition of adjustments to a theory to save it from being falsified by compensating for anomalies not anticipated by the theory in its unmodified form. Theories that rely on continual, ad hoc adjustments are distrusted.

ad hoc; → hypothesis.

alternative hypothesis
  انگاره‌ی ِ دگرینه   
engâre-ye degarine

Fr.: hypothèse alternative   

Statistics: In → significance testing, any hypothesis which differs from the one being tested. A hypothesis alternative to the → null hypothesis is denoted by H1.

alternative; → hypothesis.

antithesis
  پاد-داین   
pâd-dâyan

Fr.: antithèse   

Logical or verbal opposition.
Philo. The second of two opposed propositions in Hegelian dialectic, the first of which is the → thesis; → synthesis.

anti-; → thesis.

aperture synthesis
  هندایش ِ دهانه   
handâyeš-e dahâné

Fr.: synthèse d'ouverture   

The method of combining the signals received by several smaller telescopes distributed over a very large area or baseline to provide the high angular resolution of a much large telescope.

aperture; → synthesis.

Big Bang nucleosynthesis (BBN)
  هسته‌هندایش ِ مهبانگ، ~ بیگ بنگ   
haste-handâyeš-e Meh Bâng, ~ Big Bang

Fr.: nucléosynthèse de Big Bang   

The production of → light elements, roughly three minutes after the → Big Bang when the temperature of the → Universe dropped from 1032 K to approximately 109 K. In a short time interval → protons and → neutrons collided to produce → deuterium. Most of the deuterium then fused with other protons and neutrons to produce → helium and a small amount of → tritium. The element → lithium 7 could also arise form the coalescence of one tritium and two deuterium nuclei. According to the Big Bang nucleosynthesis theory, roughly 25% of the mass of the Universe consists of helium. It also predicts about 0.01% deuterium, and even smaller quantities of lithium. These predictions depend critically on the → baryon-photon ratio. Same as → primordial nucleosynthesis.

Big Bang; → nucleosynthesis.

chemosynthesis
  شیمی‌هندایش   
šimihandâyeš

Fr.: chimiosynthèse   

In biochemistry, the ability to produce organic compounds using energy contained in inorganic molecules. Chemosynthesis is similar to → photosynthesis. Instead of using light as an energy source to make food, energy or compounds from chemical reactions is used. Most chemosynthetic organisms are bacteria.

chemo-; → synthesis.

de Broglie hypothesis
  انگاره‌ی ِ دوبروی   
engâre-ye de Broglie

Fr.: hypothèse de de Broglie   

The suggestion by Louis de Broglie in 1924 whereby if → electromagnetic waves possess particle properties (→ particle nature), then it might be reasonable to suppose that material particles, such as → electrons, should possess wave properties (→ wave nature). The de Broglie hypothesis was based on the intuitive feeling that nature seems to have strong attachment to symmetry. In other words, if radiation has particle-like properties, then material particles should possess wave-like properties. At the time no direct experimental evidence was present for the validity of this suggestion. The first confirmation of de Broglie's hypothesis was provided by the → Davisson-Germer experiment. See also → wave-particle duality;

de Broglie equation; → hypothesis.

explosive nucleosynthesis
  هسته اندایش ِ اسکفتی   
hasté andâyeš-e oskafti

Fr.: nucléosynthèse explosive   

The explosive processes that are believed to occur in supernovae. Explosive carbon burning occurs at a temperature of about 2 × 109 degrees and produces the nuclei from neon to silicon. Explosive oxygen burning occurs near 4 × 109 degrees and produces nuclei between silicon and calcium in atomic weight.At higher temperatures, still heavier nuclei are produced.

explosive; → nucleosynthesis.

hypothesis
  انگاره، اوپاداین   
engâre (#), upâdâyan

Fr.: hypothèse   

A statement which is based on previous observations and which serves as a starting point for further investigation by which it may be proved or disproved. See also → theory, → model, → ad hoc hypothesis, → Kant-Laplace hypothesis, → arge number hypothesis, → nebular hypothesis, → null hypothesis, → statistical hypothesis, → statistical hypothesis testing.

Hypothesis, from M.Fr. hypothèse, from L.L. hypothesis, from Gk. hypothesis "base, basis of an argument, supposition," literally "a placing under," from → hypo- "under" + thesis "a placing, proposition," from root of tithenai "to place, put, set," didomi "I give;" from PIE base *dhe- "to put, to do;" cf. Mod.Pers. dâdan "to give," Mid.Pers. dâdan "to give," O.Pers./Av. dā- "to give, grant, yield," dadāiti "he gives;" Skt. dadáti "he gives;" L. dare "to give, offer," facere "to do, to make;" Rus. delat' "to do;" O.H.G. tuon, Ger. tun, O.E. don "to do."

Engâré, from engâridan, engâštan "to → suppose."
Upâdâyan, from upâ-, → hypo-, + dâyan, → thesis.

Kant-Laplace hypothesis
  انگاره‌ی ِ کانت-لاپلاس   
engâre-ye Kant-Laplace

Fr.: hypothèse de Kant-Laplace   

The hypothesis of the origin of the solar system proposed first by Kant (1755) and later by Laplace (1796). According to this hypothesis, the solar system began as a nebula of tenuous gas. Particles collided and gradually, under the influence of gravitation, the condensing gas took the form of a disk. Larger bodies formed, moving in circular orbits around the central condensation (the Sun).

Named after the German prominent philosopher Immanuel Kant (1724-1804) and the French great mathematician, physicist, and astronomer Pierre-Simon Marquis de Laplace (1749-1827); → hypothesis.

large number hypothesis
  انگاره‌ی ِ عددهای ِ بزرگ   
engâre-ye adadhâ-ye bozorg

Fr.: hypothèse des grands nombres   

The idea whereby the coincidence of various → large numbers would bear a profound sense as to the nature of physical laws and the Universe. Dirac suggested that the coincidence seen among various large numbers of different nature is not accidental but must point to a hitherto unknown theory linking the quantum mechanical origin of the Universe to the various cosmological parameters. As a consequence, some of the → fundamental constants cannot remain unchanged for ever. According to Dirac's hypothesis, atomic parameters cannot change with time and hence the → gravitational constant should vary inversely with time (G∝ 1/t). Dirac, P. A. M., 1937, Nature 139, 323; 1938, Proc. R. Soc. A165, 199.

large; → number; → hypothesis.

nebular hypothesis
  انگاره‌ی ِ میغ   
engâre-ye miq

Fr.: hypothèse nébulaire   

The hypothesis first put forward in the 18-th century that the solar system formed from a primeval nebula around the Sun. Same as the → Kant-Laplace hypothesis.

nebular; → hypothesis.

no boundary hypothesis
  انگاره‌ی ِ گیتی بی کران ِ آغازین   
engâre-ye giti bi karân-e âqâzin

Fr.: l'hypothèse de l'Univers sans limite initiale   

The proposal whereby the → Universe would not have begun with a → singularity. Instead, the → Big Bang would be an ordinary point of → space-time. The proposal, advanced by James Hartle and Stephen Hawking (1983) results from an attempt to combine aspects of → general relativity and → quantum mechanics. Based on an imaginary time assumption, it predicts a closed Universe that would start at a single point, that can be compared to the North Pole of the Earth on a two-dimensional space. Before the → Planck era there was space, but the real time began with the Big Bang event. → Hartle-Hawking initial state.

boundary; → hypothesis.

nucleosynthesis
  هسته‌هندایش   
haste-handâyeš

Fr.: nucléosynthèse   

The process by which → nuclear reactions at very high temperatures and pressures produce the various → chemical elements of the → periodic table, either in the → Big Bang or in stellar interiors. See also → primordial nucleosynthesis, → stellar nucleosynthesis, → explosive nucleosynthesis.

From nucleo-, combining form of → nucleus + → synthesis.

Haste-handâyeš, from hasténucleus + handâyešsynthesis.

null hypothesis
  انگاره‌ی ِ نول   
engâre-ye nul

Fr.: hypothèse nulle   

Statistics: The assumption of the absence of a particular pattern in a set of data. The null hypothesis, denoted by H0, is put forward to be rejected in order to support an → alternative hypothesis.

null; → hypothesis.

photosynthesis
  شیدهندایش   
šidhandâyeš

Fr.: photosynthèse   

The process in green plants, algae, diatoms, and certain forms of bacteria by which carbohydrates are synthesized from carbon dioxide and water using light as an energy source. Most forms of photosynthesis release oxygen as a byproduct.

photo- + → synthesis.

primordial nucleosynthesis
  هسته‌هندایش ِ بن‌آغازین   
haste-handâyeš-e bonâqâzin

Fr.: nucléosynthèse primordiale   

The formation of → chemical elements in the → early Universe, between about 0.01 seconds and 3 minutes after the → Big Bang, when the nuclei of primordial matter collided and fused with one another. Most of the → helium in the → Universe was created by this process. Same as → Big Bang nucleosynthesis

primordial; → nucleosynthesis.

spectral synthesis
  هندایش ِ بینابی   
handâyeš-e binâbi

Fr.: synthèse spectrale   

The process of computing line strengths in stellar spectra using an appropriate stellar atmosphere model, atomic and molecular data, and the numerical solution of the → radiative transfer equation at each point in the spectrum.

spectral; → synthesis.

statistical hypothesis
  انگاره‌ی ِ آماری   
engâre-ye âmâri

Fr.: hypothèse statistique   

An assumed statement about the way a → random variable is distributed. A statistical hypothesis generally specifies the form of the → probability distribution or the values of the parameters of the distribution. The statement may be true or false. See also → null hypothesis.

statistical; → hypothesis.

statistical hypothesis testing
  آزمون ِ انگاره‌ی ِ آماری   
âzmun-e engâre-ye âmâri

Fr.: test d'hypothèse statistique   

A method of making decision between rejecting or not rejecting a → null hypothesis on the basis of a set of observations.

statistical; → hypothesis; → test.

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