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

The → water molecule in which the → nuclear spin of the constituent → hydrogen atoms are → parallel (→ orthohydrogen). In astrophysics the ratio between ortho- and → para-water is used to determine temperatures in → interstellar medium.

→ ortho-; → water.

Of a triangle, the point where the three → altitudes of the → triangle converge.

→ ortho-; → center.

In elementary geometry, pertaining to or involving right angles or perpendiculars.
Of a system of real functions, defined so that the integral of the product of any two different functions is zero.
Of a linear transformation, defined so that the length of a vector under the transformation equals the length of the original vector.
Of a square matrix, defined so that its product with its transpose results in the identity matrix.

→ ortho- + gonia "angle," related to gony "knee;" L. genu "knee;" Mod.Pers. zânu "knee;" Av. žnav-, žnu- "knee;" Skt. janu-; PIE base *g(e)neu-, see below, + → -al

Ardâkonj, from ardâ-, → ortho-, + konj "angle, corner, confined place" (variants xong "corner, angle," Tabari kânj, Kurd. kunj, Hamadâni kom), maybe from the PIE base *g(e)neu-, as above, and related to Mod.Pers. zânu "knee" (Av. žnu-), Skt. kona- "angle, corner," Gk. gony, gonia, L. cuneus "a wedge," Albanian (Gheg dialect) kân "angle, corner," Albanian (Toks) kënd "angle, corner."

A set of functions, any two of which, by analogy to orthogonal vectors, vanish if their product is summed by integration over a specified interval.

→ orthogonal; → function.

Perpendicular lines.

→ orthogonal; → line.

Math.: An → isogonal trajectory where the family of curves are cut at right angles.

→ orthogonal; → trajectory.

Two non-zero vectors which are perpendicular, i.e. their → scalar product is zero.

→ orthogonal; → vector.

1) The property of → orthogonal functions.
2) The following conditions satisfied by the → Fourier series:
∫ cos (mx) sin (nx) dx = 0 (summed from -π to +π) for all m, n
∫ cos (mx) cos (nx) dx = 0 (summed from -π to +π) for all m ≠ n, = 2π for m = n = 0, = π for (m = n) > 0
∫ sin (mx) sin (nx) dx = 0 (summed from -π to +π) for m ≠ n, = π for (m = n) > 0.

→ orthogonal; → -ity.

Molecular hydrogen in which the nuclei (protons) of the two hydrogen atoms contained in the molecule have spins in the same direction. → parahydrogen

→ ortho-; → hydrogen.

Two non-zero vectors that are → orthogonal and have magnitude 1.

→ orthogonal; → vector.

Of or relating to a crystalline structure characterized by three mutually perpendicular axes of different length. → orthorhombic crystal system.

→ ortho-; → rhombic.

A → crystal system that has three mutually perpendicular axes, each of which is of a different length than the others.

→ orthorhombic; → crystal; → system.

Of or relating to an optical system corrected for → distortion.

→ ortho-; → -scopic.

A telescopic eyepiece that produces a wide field of view (between 40° and 50°). The eyepiece consists of a single element lens that is normally plano-convex, and a cemented triplet that is usually symmetrical.

→ orthoscopic; → eyepiece.

To have, produce, or generate oscillations. → vibrate.

From L. oscillatus, p.p. of oscillare "to swing," from oscill(um) "swing" + -ate a suffix forming verbs from L. words.

Navidan "to swing, oscillate," from nâvidan, literally "to swing like a ship," from nâv "ship;" O.Pers./Av. *nāv-, O.Pers. nāviyā- "fleet;" Skt. nau-, nava- "ship, boat;" Gk. naus "ship;" PIE *nau- "boat."

A cosmological model in which the Universe is closed and undergoes a series of oscillations, each beginning with a big bang and ending with a big crunch.

Oscillating, verbal adj. of → oscillate; → universe.

The state of any quantity when the value of that quantity is continually changing so that it passes through maximum and minimum values.

Verbal noun of → oscillate.

Same as → pulsation mode.

→ oscillation; → mode.

A device for producing sonic or ultrasonic pressure waves in a medium. A device with no rotating parts for converting direct current into alternating current.

Agent noun of → oscillate.

A quantum-mechanical measure of the probability that a specific atomic transition will occur. It is used in the equation for the absorption coefficient of a spectral line. Also known as f value.

→ oscillator; → strength.