66 relations: Applied Physics Laboratory, Astronomer, Astronomical object, Astronomical seeing, Atmosphere, Atmosphere of Earth, Atmospheric optics, Atmospheric pressure, Bar (unit), Cartography, Celsius, Culmination, Density of air, Dispersion (optics), Electromagnetic radiation, Ernest Shackleton, Fata Morgana (mirage), Friedrich Bessel, George Comstock (astronomer), Height, Horizon, Horizontal coordinate system, Humidity, Ibn al-Haytham, Imperial Trans-Antarctic Expedition, International Astronomical Union, International Standard Atmosphere, Jet Propulsion Laboratory, Kelvin, Lapse rate, Levelling refraction, Light, Looming and similar refraction phenomena, Millimeter of mercury, Millisecond, Minute and second of arc, Mirage, Moon, Naked eye, National Observatory of Athens, Novaya Zemlya effect, Optical telescope, Pascal (unit), Pressure, Radian, Ray tracing (physics), Refraction, Refraction (sound), Refractive index, Scattering, ..., Semidiameter, Shen Kuo, Star, Sun, Sunrise, Sunset, Surveying, Temperature, The Nautical Almanac, Trigonometric functions, Turbulence, Twinkling, United States Naval Observatory, Visible spectrum, Water vapor, Zenith. Expand index (16 more) » « Shrink index
The Johns Hopkins University Applied Physics Laboratory, commonly known as simply the Applied Physics Laboratory, or APL, located in Howard County, Maryland, near Laurel and Columbia, is a not-for-profit, university-affiliated research center (or UARC) employing 6,000 people.
An astronomer is a scientist in the field of astronomy who concentrates their studies on a specific question or field outside the scope of Earth.
An astronomical object or celestial object is a naturally occurring physical entity, association, or structure that exists in the observable universe.
Astronomical seeing is the blurring and twinkling of astronomical objects like stars due to turbulent mixing in the Earth's atmosphere, causing variations of the optical refractive index.
An atmosphere is a layer or a set of layers of gases surrounding a planet or other material body, that is held in place by the gravity of that body.
The atmosphere of Earth is the layer of gases, commonly known as air, that surrounds the planet Earth and is retained by Earth's gravity.
Atmospheric optics deals with how the unique optical properties of Earth's atmosphere cause a wide range of spectacular optical phenomena.
Atmospheric pressure, sometimes also called barometric pressure, is the pressure within the atmosphere of Earth (or that of another planet).
The bar is a metric unit of pressure, but is not approved as part of the International System of Units (SI).
Cartography (from Greek χάρτης chartēs, "papyrus, sheet of paper, map"; and γράφειν graphein, "write") is the study and practice of making maps.
The Celsius scale, previously known as the centigrade scale, is a temperature scale used by the International System of Units (SI).
In astronomy, the culmination of a planet, star, or constellation is its transit over an observer's meridian.
The density of air ρ (Greek: rho) (air density) is the mass per unit volume of Earth's atmosphere.
In optics, dispersion is the phenomenon in which the phase velocity of a wave depends on its frequency.
In physics, electromagnetic radiation (EM radiation or EMR) refers to the waves (or their quanta, photons) of the electromagnetic field, propagating (radiating) through space-time, carrying electromagnetic radiant energy.
Sir Ernest Henry Shackleton (15 February 1874 – 5 January 1922) was a polar explorer who led three British expeditions to the Antarctic, and one of the principal figures of the period known as the Heroic Age of Antarctic Exploration.
A Fata Morgana is an unusual and complex form of superior mirage that is seen in a narrow band right above the horizon.
Friedrich Wilhelm Bessel (22 July 1784 – 17 March 1846) was a German astronomer, mathematician, physicist and geodesist.
George Cary Comstock (February 12, 1855 – May 11, 1934) was an American astronomer and educator.
Height is the measure of vertical distance, either how "tall" something or someone is, or how "high" the position is.
The horizon or skyline is the apparent line that separates earth from sky, the line that divides all visible directions into two categories: those that intersect the Earth's surface, and those that do not.
The horizontal coordinate system is a celestial coordinate system that uses the observer's local horizon as the fundamental plane.
Humidity is the amount of water vapor present in the air.
Hasan Ibn al-Haytham (Latinized Alhazen; full name أبو علي، الحسن بن الحسن بن الهيثم) was an Arab mathematician, astronomer, and physicist of the Islamic Golden Age.
The Imperial Trans-Antarctic Expedition (1914–17), also known as the Endurance Expedition, is considered the last major expedition of the Heroic Age of Antarctic Exploration.
The International Astronomical Union (IAU; Union astronomique internationale, UAI) is an international association of professional astronomers, at the PhD level and beyond, active in professional research and education in astronomy.
The International Standard Atmosphere (ISA) is an atmospheric model of how the pressure, temperature, density, and viscosity of the Earth's atmosphere change over a wide range of altitudes or elevations.
The Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center in Pasadena, California, United States, with large portions of the campus in La Cañada Flintridge, California.
The Kelvin scale is an absolute thermodynamic temperature scale using as its null point absolute zero, the temperature at which all thermal motion ceases in the classical description of thermodynamics.
Lapse rate is the rate at which Earth's atmospheric temperature decreases with an increase in altitude, or increases with the decrease in altitude.
Levelling refraction refers to the systematic refraction effect distorting the results of line levelling over the Earth's surface.
Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum.
While mirages are the best known atmospheric refraction phenomena, looming and similar refraction phenomena do not produce mirages.
A millimeter of mercury is a manometric unit of pressure, formerly defined as the extra pressure generated by a column of mercury one millimetre high and now defined as precisely pascals.
A millisecond (from milli- and second; symbol: ms) is a thousandth (0.001 or 10−3 or 1/1000) of a second.
A minute of arc, arcminute (arcmin), arc minute, or minute arc is a unit of angular measurement equal to of one degree.
A mirage is a naturally occurring optical phenomenon in which light rays bend to produce a displaced image of distant objects or the sky.
The Moon is an astronomical body that orbits planet Earth and is Earth's only permanent natural satellite.
Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnifying or light-collecting optical instrument, such as a telescope or microscope.
The National Observatory of Athens (NOA; Εθνικό Αστεροσκοπείο Αθηνών) is a research institute in Athens, Greece.
The Novaya Zemlya effect is a polar mirage caused by high refraction of sunlight between atmospheric thermoclines.
An optical telescope is a telescope that gathers and focuses light, mainly from the visible part of the electromagnetic spectrum, to create a magnified image for direct view, or to make a photograph, or to collect data through electronic image sensors.
The pascal (symbol: Pa) is the SI derived unit of pressure used to quantify internal pressure, stress, Young's modulus and ultimate tensile strength.
Pressure (symbol: p or P) is the force applied perpendicular to the surface of an object per unit area over which that force is distributed.
The radian (SI symbol rad) is the SI unit for measuring angles, and is the standard unit of angular measure used in many areas of mathematics.
In physics, ray tracing is a method for calculating the path of waves or particles through a system with regions of varying propagation velocity, absorption characteristics, and reflecting surfaces.
Refraction is the change in direction of wave propagation due to a change in its transmission medium.
Refraction, in acoustics, comparable to the refraction of electromagnetic radiation, is the bending of sound propagation trajectories (rays) in inhomogeneous elastic media (gases, liquids, and solids) in which the wave velocity is a function of spatial coordinates.
In optics, the refractive index or index of refraction of a material is a dimensionless number that describes how light propagates through that medium.
Scattering is a general physical process where some forms of radiation, such as light, sound, or moving particles, are forced to deviate from a straight trajectory by one or more paths due to localized non-uniformities in the medium through which they pass.
In geometry, the semidiameter or semi-diameter of a set of points may be one half of its diameter; or, sometimes, one half of its extent along a particular direction.
Shen Kuo (1031–1095), courtesy name Cunzhong (存中) and pseudonym Mengqi (now usually given as Mengxi) Weng (夢溪翁),Yao (2003), 544.
A star is type of astronomical object consisting of a luminous spheroid of plasma held together by its own gravity.
The Sun is the star at the center of the Solar System.
Sunrise or sun up is the instant at which the upper edge of the Sun appears over the horizon in the morning.
Sunset or sundown is the daily disappearance of the Sun below the horizon as a result of Earth's rotation.
Surveying or land surveying is the technique, profession, and science of determining the terrestrial or three-dimensional positions of points and the distances and angles between them.
Temperature is a physical quantity expressing hot and cold.
The Nautical Almanac has been the familiar name for a series of official British almanacs published under various titles since the first issue of The Nautical Almanac and Astronomical Ephemeris, for 1767: this was the first nautical almanac ever to contain data dedicated to the convenient determination of longitude at sea.
In mathematics, the trigonometric functions (also called circular functions, angle functions or goniometric functions) are functions of an angle.
In fluid dynamics, turbulence or turbulent flow is any pattern of fluid motion characterized by chaotic changes in pressure and flow velocity.
Twinkling, or scintillation, is a generic term for variations in apparent brightness or position of a distant luminous object viewed through a medium.
The United States Naval Observatory (USNO) is one of the oldest scientific agencies in the United States, with a primary mission to produce Positioning, Navigation and Timing (PNT) for the United States Navy and the United States Department of Defense.
The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye.
The zenith is an imaginary point directly "above" a particular location, on the imaginary celestial sphere.