A bright, confusing, and excessive grouping of light sources. Light clutter is a type of → light pollution. It is a general term relating to lights put up everywhere, without regard to what their purpose really is.
maxrut-e nur (#)
Fr.: cône de lumière
The set of all directions in which a light signal can travel toward an event (past light cone) or from an event (future light cone).
nur-xam, xam-e nur
Fr.: courbe de lumière
Fr.: cylindre de lumière
A cylinder of radius cP/(2π) around a → pulsar's spin axis, where P is the pulsar period and c the → speed of light. At this surface, the velocity of a hypothetical object that corotates with the → neutron star would reach the speed of light.
Fr.: déflexion de la lumière
The deviation of a light ray by the gravitational field of a massive body. For example, stellar light passing near the Sun will be deviated by 1''.75 at the Sun's limb.
pažvâk-e nuri (#)
Fr.: écho de lumière
Reflection of light from a stellar outburst by successively more distant clouds of dust surrounding the star. For example, the light echoes from two shells of dust near supernova 1987A, or those of star V838 Mon.
bonpâr-e sabok (#)
Fr.: élément léger
In astrophysics, a chemical element that has an atomic number of one, two, or three, such as hydrogen, helium, and lithium; sometimes also beryllium and boron.
Fr.: colonne lumineuse
An atmospheric optical phenomenon appearing as a vertical shaft of light extending from the Sun or other bright light source during very cold weather. Light pillars or → sun pillars occur when artificial light or sunlight near the horizon is reflected from falling ice crystals associated with thin, high-level clouds. The ice crystals have a hexagonal plate shape and fall with a horizontal orientation, gently rocking from side to side as they fall.
âludegi-ye nuri (#)
Fr.: pollution lumineuse
The inappropriate or excessive use of artificial light. It brightens the sky and has a particularly damaging effect on astronomical observations. More generally, light pollution can have serious environmental consequences for humans, wildlife, and our climate. Types of light pollution include: → glare, → skyglow, → light trespass, and → light clutter.
Fr.: rayon de lumière
An imaginary line directed along the path that the light follows. In other words, light pictured simply in terms of straight lines.
Fr.: lumière intrusive
A type of → light pollution which is light falling where it is not wanted or needed. Light trespass occurs when poorly shielded or poorly aimed fixtures cast light into unwanted areas, such as buildings, neighboring property, and homes. This light is a main contributor to → skyglow which interferes with astronomical instruments.
nur-sâl (#), sâl-e nuri (#)
tavân-e gerdâvari-ye nur (#)
Fr.: pouvoir collecteur de lumière
The most important function of an astronomical telescope, which is directly related to the area (or to the square of the diameter) of the main mirror or lens.
Tavân, → power; gerdâvari, verbal noun of gerd âvardan, from gerd "round; around" (Mid.Pers. girt "round, all around," O.Iranian *gart- "to twist, to wreathe," cf. Skt. krt "to twist threads, spin, to wind, to surround," kata- "a twist of straw;" Pali kata- "ring, bracelet;" Gk. kartalos "a kind of basket," kyrtos "curved") + âvardan "to bring," Mid.Pers. âwurtan, âvaritan; Av. ābar- "to bring, to possess," from prefix ā- + Av./O.Pers. bar- "to bear, carry," bareθre "to bear (infinitive)," bareθri "a female that bears (children), a mother;" Mod.Pers. bordan "to carry;" Skt. bharati "he carries;" Gk. pherein; L. fero "to carry;" nur, → light.
nur-sâniyé, sâniye-ye nuri
The distance travelled by light in free space in one second. It is equivalent to 2.997924580 × 108 m or 2.998 × 105 km. This unit of length is mainly used in astronomy, telecommunications, and relativistic physics. Some quantities expressed in this unit are as follows. The mean diameter of the Earth: about 0.0425 light-seconds. The average distance from the Earth to the Moon: about 1.282 light-seconds. The diameter of the Sun: about 4.643 light-seconds. The average distance from the Earth to the Sun: 499.0 light-seconds.
nur-zamân, zamân-e nuri (#)
The time it takes for light, travelling at about 300 000 km per second, to travel a certain distance.
apest-e safar-e nur
Fr.: distance du voyage de la lumière
The distance traversed by a photon between the time it is emitted and the time it reaches the observer. It is also referred to as the → look-back time.
nur-sâl (#), sâl-e nuri (#)
Fr.: faisceau de fibres optiques; guide d'ondes optique
A bundle of optical fibers arranged randomly for the purpose of transmitting energy, not an image.
Fr.: genre lumière
Fr.: intervalle genre lumière
The space-time interval between two events if it is zero, i.e. ds2 = 0.