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Earth EARTH is the third planet from the Sun Sun and the only object in the Universe Universe known to harbor life . According to radiometric dating and other sources of evidence, Earth Earth formed over 4 billion years ago . Earth\'s gravity interacts with other objects in space, especially the Sun Sun and the Moon Moon , Earth's only natural satellite . Earth Earth revolves around the Sun Sun in 365.26 days, a period known as an Earth Earth year . During this time, Earth Earth rotates about its axis about 366.26 times. Earth's axis of rotation is tilted, producing seasonal variations on the planet's surface [...More...]  "Earth" on: Wikipedia Yahoo 

Volume VOLUME is the quantity of threedimensional space enclosed by a closed surface , for example, the space that a substance (solid , liquid , gas , or plasma ) or shape occupies or contains. Volume Volume is often quantified numerically using the SI derived unit SI derived unit , the cubic metre . The volume of a container is generally understood to be the capacity of the container; i. e., the amount of fluid (gas or liquid) that the container could hold, rather than the amount of space the container itself displaces. Three dimensional mathematical shapes are also assigned volumes. Volumes of some simple shapes, such as regular, straightedged, and circular shapes can be easily calculated using arithmetic formulas [...More...]  "Volume" on: Wikipedia Yahoo 

Kelvin 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 . The KELVIN (symbol: K) is the base unit of temperature in the International System of Units (SI). The kelvin is defined as the fraction 1⁄273.16 of the thermodynamic temperature of the triple point of water (exactly 0.01 °C or 32.018 °F). In other words, it is defined such that the triple point of water is exactly 273.16 K. The Kelvin Kelvin scale is named after the Belfastborn, Glasgow University engineer and physicist William Thomson, 1st Baron Kelvin (1824–1907), who wrote of the need for an "absolute thermometric scale". Unlike the degree Fahrenheit Fahrenheit and degree Celsius Celsius , the kelvin is not referred to or typeset as a degree [...More...]  "Kelvin" on: Wikipedia Yahoo 

Temperature TEMPERATURE is a physical quantity expressing hot and cold . Temperature Temperature is measured with a thermometer , historically calibrated in various temperature scales and units of measurement . The most commonly used scales are the Celsius scale , denoted in °C (informally, degrees centigrade), the Fahrenheit scale (°F), and the Kelvin scale . The kelvin (K) is the unit of temperature in the International System of Units International System of Units (SI), in which temperature is one of the seven fundamental base quantities . The coldest theoretical temperature is absolute zero , at which the thermal motion of all fundamental particles in matter reaches a minimum. Although classically described as motionless, particles still possess a finite zeropoint energy in the quantum mechanical description [...More...]  "Temperature" on: Wikipedia Yahoo 

Meridional The terms ZONAL and MERIDIONAL are used to describe directions on a globe . ZONAL means "along a latitude circle " or "in the west–east direction"; while MERIDIONAL means "along a longitude circle " (a.k.a. meridian ) or "in the north–south direction". These terms are often used in the atmospheric and earth sciences to describe global phenomena, such as "meridional wind flow", or "zonal temperature". (Strictly speaking, ZONAL means more than simply a direction as it also implies a degree of localization in the meridional direction, so that the phenomenon in question is localized to a zone of the planet.) "Meridional" is also used to describe the axis close to the chain orientation in a polymer fiber, while the term "equatorial" is used to describe the direction normal to the fiber axis. For vector fields (such as wind velocity ), the zonal component (or xcoordinate ) is denoted as u, while the meridional component (or ycoordinate) is denoted as v [...More...]  "Meridional" on: Wikipedia Yahoo 

Invariable Plane The INVARIABLE PLANE of a planetary system , also called LAPLACE\'S INVARIABLE PLANE, is the plane passing through its barycenter (center of mass) perpendicular to its angular momentum vector . In the Solar System , about 98% of this effect is contributed by the orbital angular momenta of the four jovian planets ( Jupiter Jupiter , Saturn Saturn , Uranus , and Neptune Neptune ). The invariable plane is within 0.5° of the orbital plane of Jupiter, and may be regarded as the weighted average of all planetary orbital and rotational planes. This plane is sometimes called the "Laplacian" or "Laplace plane" or the "invariable plane of Laplace", though it should not be confused with the Laplace plane , which is the plane about which orbital planes precess [...More...]  "Invariable Plane" on: Wikipedia Yahoo 

Pascal (unit) The PASCAL (symbol: Pa) is the SI derived unit of pressure used to quantify internal pressure , stress , Young\'s modulus and ultimate tensile strength . It is defined as one newton per square metre . It is named after the French polymath Blaise Pascal . Common multiple units of the pascal are the hectopascal (1 hPa = 100 Pa) which is equal to one millibar , and the kilopascal (1 kPa = 1000 Pa) which is equal to one centibar. The unit of measurement called standard atmosphere (atm) is defined as 101,325 Pa and approximates to the average pressure at sealevel at the latitude 45° N. Meteorological reports typically state atmospheric pressure in hectopascals [...More...]  "Pascal (unit)" on: Wikipedia Yahoo 

ETRS89 The EUROPEAN TERRESTRIAL REFERENCE SYSTEM 1989 (ETRS89) is an ECEF (EarthCentered, EarthFixed) geodetic Cartesian reference frame , in which the Eurasian Plate Eurasian Plate as a whole is static. The coordinates and maps in Europe based on ETRS89 are not subject to change due to the continental drift . The development of ETRS89 is related to the global ITRS geodetic datum , in which the representation of the continental drift is balanced in such a way that the total apparent angular momentum of continental plates is about 0. ETRS89 was officially born at the 1990 Florence Florence meeting of EUREF , following its Resolution 1, which recommends that the terrestrial reference system to be adopted by EUREF will be coincident with ITRS at the epoch 1989.0 and fixed to the stable part of the Eurasian Plate. According to the resolution, this system was named European Terrestrial Reference System 89 (ETRS89) [...More...]  "ETRS89" on: Wikipedia Yahoo 

Nitrogen NITROGEN is a chemical element with symbol N and atomic number 7. It was first discovered and isolated by Scottish physician Daniel Rutherford in 1772. Although Carl Wilhelm Scheele and Henry Cavendish had independently done so at about the same time, Rutherford is generally accorded the credit because his work was published first. The name nitrogen was suggested by JeanAntoineClaude Chaptal in 1790, when it was found that nitrogen was present in nitric acid and nitrates ; this name derives from the Greek roots νἰτρον "nitre " and γεννᾶν "to form" [...More...]  "Nitrogen" on: Wikipedia Yahoo 

Bond Albedo The BOND ALBEDO, named after the American astronomer George Phillips Bond (1825–1865), who originally proposed it, is the fraction of power in the total electromagnetic radiation incident on an astronomical body that is scattered back out into space. Because the Bond albedo accounts for all of the light scattered from a body at all wavelengths and all phase angles , it is a necessary quantity for determining how much energy a body absorbs. This, in turn, is crucial for determining the equilibrium temperature of a body. Because bodies in the outer Solar System are always observed at very low phase angles from the Earth, the only reliable data for measuring their Bond albedo comes from spacecraft [...More...]  "Bond Albedo" on: Wikipedia Yahoo 

Geometric Albedo In astronomy , the GEOMETRIC ALBEDO of a celestial body is the ratio of its actual brightness as seen from the light source (i.e. at zero phase angle ) to that of an idealized flat, fully reflecting, diffusively scattering (Lambertian ) disk with the same crosssection. (This phase angle refers to the direction of the light paths and is not a phase angle in its normal meaning in optics or electronics .) Diffuse scattering implies that radiation is reflected isotropically with no memory of the location of the incident light source. Zero phase angle corresponds to looking along the direction of illumination. For Earthbound observers this occurs when the body in question is at opposition and on the ecliptic . The VISUAL GEOMETRIC ALBEDO refers to the geometric albedo quantity when accounting for only electromagnetic radiation in the visible spectrum [...More...]  "Geometric Albedo" on: Wikipedia Yahoo 

Mean Anomaly In celestial mechanics , the MEAN ANOMALY is an angle used in calculating the position of a body in an elliptical orbit in the classical twobody problem . It is the angular distance from the pericenter which a fictitious body would have if it moved in a circular orbit , with constant speed , in the same orbital period as the actual body in its elliptical orbit. CONTENTS * 1 Definition * 2 Formula * 3 See also * 4 References * 5 External links DEFINITIONDefine T as the time required for a particular body to complete one orbit. In time T, the radius vector sweeps out 2π radians or 360°. The average rate of sweep, n, is then n = 2 T or n = 360 T , {displaystyle n={frac {2pi }{T}}quad {mbox{or}}quad n={frac {360^{circ }}{T}},} which is called the mean angular motion of the body, with dimensions of radians per unit time or degrees per unit time. Define τ as the time at which the body is at the pericenter [...More...]  "Mean Anomaly" on: Wikipedia Yahoo 

Argument Of Periapsis The ARGUMENT OF PERIAPSIS (also called ARGUMENT OF PERIFOCUS or ARGUMENT OF PERICENTER), symbolized as ω, is one of the orbital elements of an orbiting body. Parametrically, ω is the angle from the body's ascending node to its periapsis , measured in the direction of motion. For specific types of orbits, words such as PERIHELION (for heliocentric orbits ), PERIGEE (for geocentric orbits ), PERIASTRON (for orbits around stars), and so on may replace the word PERIAPSIS. (See apsis for more information.) An argument of periapsis of 0° means that the orbiting body will be at its closest approach to the central body at the same moment that it crosses the plane of reference from South to North. An argument of periapsis of 90° means that the orbiting body will reach periapsis at its northmost distance from the plane of reference. Adding the argument of periapsis to the longitude of the ascending node gives the longitude of the periapsis [...More...]  "Argument Of Periapsis" on: Wikipedia Yahoo 

Flattening FLATTENING is a measure of the compression of a circle or sphere along a diameter to form an ellipse or an ellipsoid of revolution (spheroid ) respectively. Other terms used are ELLIPTICITY, or OBLATENESS. The usual notation for flattening is f and its definition in terms of the semiaxes of the resulting ellipse or ellipsoid is f l a t t e n i n g = f = a b a . {displaystyle mathrm {flattening} =f={frac {ab}{a}}.} The compression factor is b/a in each case. For the ellipse, this factor is also the aspect ratio of the ellipse. There are two other variants of flattening (see below) and when it is necessary to avoid confusion the above flattening is called the FIRST FLATTENING [...More...]  "Flattening" on: Wikipedia Yahoo 

Density The DENSITY, or more precisely, the VOLUMETRIC MASS DENSITY, of a substance is its mass per unit volume . The symbol most often used for density is ρ (the lower case Greek letter rho ), although the Latin letter D can also be used. Mathematically, density is defined as mass divided by volume: = m V {displaystyle rho ={frac {m}{V}}} where ρ is the density, m is the mass, and V is the volume. In some cases (for instance, in the United States oil and gas industry), density is loosely defined as its weight per unit volume , although this is scientifically inaccurate – this quantity is more specifically called specific weight . For a pure substance the density has the same numerical value as its mass concentration . Different materials usually have different densities, and density may be relevant to buoyancy , purity and packaging [...More...]  "Density" on: Wikipedia Yahoo 

Osculating Orbit In astronomy , and in particular in astrodynamics , the OSCULATING ORBIT of an object in space at a given moment in time is the gravitational Kepler orbit Kepler orbit (i.e. ellipse or other conic) that it would have about its central body if perturbations were not present. That is, it is the orbit that coincides with the current orbital state vectors (position and velocity). The word "osculate" derives from a Latin word meaning "to kiss". Its use in this context derives from the fact that, at any point in time, an object's osculating orbit is precisely tangent to its actual orbit, with the tangent point being the object's location – and has the same curvature as the orbit would have in the absence of perturbing forces [...More...]  "Osculating Orbit" on: Wikipedia Yahoo 