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

An → interference process in which the → amplitude of the resultant wave is greater than that of either individual waves. See also → destructive interference.

Constructive, from M.Fr. constructif or from M.L. constructivus, from L. construct-, p.p. stem of construere "to heap up," from → con- + struc- variant stem of struere "to build," → structure; → interference.

Andarzaneš, → interference; sâzandé "constructive," from sâxtan, → structure.

An → interference process in which the → amplitude of the the amplitude of the resultant wave is less than that of either individual waves. See also → constructive interference.

Destructive, from O.Fr. destructif, from L.L. destructivus, from destruct-, p.p. stem of destruere, from → de- + struere "to build," → structure; → interference.

Andarzaneš, → interference; virângar "destructive," from virân, "destroyed, ruined."

A space project, initially → LISA, consisting of a configuration of three satellites, aimed to detect low frequency → gravitational waves that cannot be measured by ground-based detectors. The detection range will be from about 0.1 milliHz to 1 Hz. One "mother" and two "daughter" spacecrafts will be brought into an orbit around the Sun, which is similar to the Earth's orbit. The satellites will fly in a near-equilateral triangle formation, with a constant distance of one million km between, following the Earth along its orbit at a distance of around 50 million km. The mother spacecrafts carries two and each of the daughter spacecraft carry one free-flying → test masses that will be kept as far as possible free of external disturbances. The mutual distances of the test masses from satellite to satellite will be measured by means of high-precision, → Michelson-like laser → interferometry. In this way, the extremely small distance variations between the test masses of two satellites can be detected which are caused by the passages of a gravitational waves. The required measurement accuracy of the distances amounts to typically 1/100 of the diameter of a hydrogen atom (10^-12 m) at a distance of two million km.

→ evolve; → laser; → interferometer; → space; → antenna.

A type of interferometer wherein the beam of light undergoes multiple reflections between two closely spaced partially silvered surfaces. Part of the light is transmitted each time the light reaches the second surface, resulting in multiple offset beams which can interfere with each other. The large number of interfering rays produces an interferometer with extremely high resolution, somewhat like the multiple slits of a diffraction grating increase its resolution.

The design was conceived by French physicists Charles Fabry (1867-1945) and Alfred Pérot (1863-1925) in the late nineteenth century; → interferometer.

An → interferometer using a technique that involves introducing a small → frequency shift between the optical frequencies of the two interfering light beams. This results in an intensity modulation at the → beat frequency of the two beams for any given point of the → interference pattern. A convenient way of introducing such a frequency shift is by means of an acousto-optic modulator.

→ heterodyne; → interferometer.

Physics: To cause → interference.

Interfere, from M.Fr. entreferer "to strike each other," from entre, → inter-, + ferir "to strike," from L. ferire "to knock, strike."

Andarzadan, from andar, → inter-, + zadan "to strike, beat," from Mid.Pers. zatan, žatan; O.Pers./Av. jan-, gan- "to strike, hit, smite, kill" (jantar- "smiter"); cf. Skt. han- "to strike, beat" (hantar- "smiter, killer"); Gk. theinein "to strike;" L. fendere "to strike, push;" Gmc. *gundjo "war, battle;" PIE *g^when- "to strike, kill."

The phenomenon occurring when two or more waves of the same → frequency having a constant → phase difference traverse simultaneously in the same region of a medium and cross each other. In the region of superposition, the the resulting wave intensity is different from the sum of intensities due to individual waves at that point. This phenomenon proved the validity of the wave theory of light. See also → constructive interference, → destructive interference, → interference fringe, → Young's experiment, → wave theory of light.

Interference, from → interfere + -ence a noun suffix equivalent to -ance, corresponding to the suffix -ent in adjectives.

Andarzaneš, verbal noun of andarzadan, → interfere.

A filter that uses the phenomenon of optical interferences between plane-parallel semi-transparent reflectors to transmit light selectively over a narrow wavelength band.

→ interference; → filter.

One of the alternating bright or dark bands produced by optical interference.

→ interference; → fringe.

→ order of interference.

→ interference; → order.

A wave pattern that results when two or more waves interfere with each other, generally showing → interference fringes. In acoustics, the interference pattern appear as the effect of → beats.

→ interference; → pattern.

1) Physics: A device that divides a beam of light into a number of beams and re-unites them to produce → interference. → Fabry-Perot interferometer; → Michelson interferometer.
2) Astro.: An arrangement of two or more separate telescopes placed at some distance from one another, each one receiving electromagnetic radiation (optical, infrared, or radio) from a celestial object and brought together to form an interference pattern.

Interferometer, from interfer, → interfer, + -o- a connective/euphonic infix + → -meter.

Andarzanešsanj, from andarzaneš→ interference + -sanj, → -meter.

Of or relating to → interferometry.

→ interferometer; → -ic.

A system of several telescopes coupled together in a particular configuration to carry out → interferometry.

→ interferometric; → array.

An observational technique based on principles of → interferometry.

→ interferometric; → technique.

1) The technique and study of the → interference phenomenon produced by → coherent electromagnetic waves.
2) Astro.: An observational technique that uses the interference phenomenon to substantially increase the → resolving power of telescopes.

Interferometry, from interfer, → interfer, + -o- a connective/euphonic infix + → -metry.

An optical instrument using laser → beams to form → interference pattern. There are two types of laser interferometers: → homodyne and → heterodyne. A homodyne interferometer, like → Michelson interferometer, uses a single-frequency laser source. A → heterodyne interferometer uses a laser source with two close frequencies.

→ laser; → interferometer.

A facility dedicated to the detection and measurement of cosmic → gravitational waves. It consists of two widely separated installations, or detectors, within the United States, operated in unison as a single observatory. One installation is located in Hanford (Washington) and the other in Livingston (Louisiana), 3,000 km apart. Funded by the National Science Foundation (NSF), LIGO was designed and constructed by a team of scientists from the California Institute of Technology, the Massachusetts Institute of Technology, and by industrial contractors. Construction of the facilities was completed in 1999. Initial operation of the detectors began in 2001. Each LIGO detector beams laser light down arms 4 km long, which are arranged in the shape of an "L." If a gravitational wave passes through the detector system, the distance traveled by the laser beam changes by a minuscule amount -- less than one-thousandth of the size of an atomic nucleus (10^-18 m). Still, LIGO should be able to pick this difference up. LIGO directly detected gravitational waves for the first time from a binary → black hole merger (GW150914) on September 14, 2015 (Abbott et al., 2016, Phys. Rev. Lett. 116, 061102). The Nobel Prize in physics 2017 was awarded to three physicists (Rainer Weiss, Barry C. Barish, and Kip S. Thorne) for decisive contributions to the LIGO detector and the observation of gravitational waves. LIGO had a prominent role in the detection of → GW170817, the first event with an → electromagnetic counterpart.

→ laser; → interferometer; → gravitational; → wave; → observatory.

A collaborative project between → NASA and → ESA to develop and operate a space-based gravitational wave detector sensitive at frequencies between 0.03 mHz and 0.1 Hz. LISA detects gravitational-wave induced strains in → space-time by measuring changes of the separation between fiducial masses in three spacecraft 5 million km apart. Ultimately, NASA and ESA decided in 2011 not to proceed with the mission. LISA was not the highest ranked mission in the 2010 Decadal Survey and funding constraints prevented NASA from proceeding with multiple large missions (http://lisa.nasa.gov). → LISA pathfinder.

→ laser; → interferometer; → space; → antenna.

An apparatus that produces interference fringes by splitting a beam of monochromatic light so that one beam strikes a fixed mirror and the other a movable mirror. When the reflected beams are brought back together, an interference pattern results. It is used to measure very precise lengths, such as the wavelength of light, and for high-resolution spectroscopy.

Named after Albert Abraham Michelson (1852-1931), German-American physicist, who built the interferometer for the → Michelson-Morley experiment of 1887; → interferometer.

Andarzanešsanj, → interferometer.