Earth's gravity measured by NASA GRACE mission, showing deviations from the theoretical gravity of an idealized, smooth Earth, the so-called Earth ellipsoid. Red shows the areas where gravity is stronger than the smooth, standard value, and blue reveals areas where gravity is weaker (Animated version).[1]
The gravity of Earth, denoted by g, is the net acceleration that is imparted to objects due to the combined effect of gravitation (from mass distribution within Earth) and the centrifugal force (from the Earth's rotation).[2][3]
It is a vector quantity, whose direction coincides with a plumb bob and strength or magnitude is given by the norm .
In SI units, this acceleration is expressed in metres per second squared (in symbols, m/s2 or m·s−2) or equivalently in newtons per kilogram (N/kg or N·kg−1). Near Earth's surface, the acceleration due to gravity, accurate to 2 significant figures, is 9.8 m/s2 (32 ft/s2). This means that, ignoring the effects of air resistance, the speed of an object falling freely will increase by about 9.8 metres per second (32 ft/s) every second. This quantity is sometimes referred to informally as little g (in contrast, the gravitational constant G is referred to as big G).
The precise strength of Earth's gravity varies with location. The agreed upon value for standard gravity is 9.80665 m/s2 (32.1740 ft/s2) by definition.[4] This quantity is denoted variously as gn, ge (though this sometimes means the normal gravity at the equator, 9.7803267715 m/s2 (32.087686258 ft/s2)),[5]g0, or simply g (which is also used for the variable local value).
The weight of an object on Earth's surface is the downwards force on that object, given by Newton's second law of motion, or F = ma (force = mass × acceleration). Gravitational acceleration contributes to the total gravity acceleration, but other factors, such as the rotation of Earth, also contribute, and, therefore, affect the weight of the object. Gravity does not normally include the gravitational pull of the Moon and Sun, which are accounted for in terms of tidal effects.
^NASA/JPL/University of Texas Center for Space Research. "PIA12146: GRACE Global Gravity Animation". Photojournal. NASA Jet Propulsion Laboratory. Retrieved 30 December 2013.
^Cite error: The named reference Boynton was invoked but never defined (see the help page).
^Hofmann-Wellenhof, B.; Moritz, H. (2006). Physical Geodesy (2nd ed.). Springer. ISBN 978-3-211-33544-4. § 2.1: "The total force acting on a body at rest on the earth's surface is the resultant of gravitational force and the centrifugal force of the earth's rotation and is called gravity."
^Bureau International des Poids et Mesures (1901). "Déclaration relative à l'unité de masse et à la définition du poids; valeur conventionnelle de gn". Comptes Rendus des Séances de la Troisième Conférence· Générale des Poids et Mesures (in French). Paris: Gauthier-Villars. p. 68. Le nombre adopté dans le Service international des Poids et Mesures pour la valeur de l'accélération normale de la pesanteur est 980,665 cm/sec², nombre sanctionné déjà par quelques législations. Déclaration relative à l'unité de masse et à la définition du poids; valeur conventionnelle de gn.
^Moritz, Helmut (2000). "Geodetic Reference System 1980". Journal of Geodesy. 74 (1): 128–133. doi:10.1007/s001900050278. S2CID 195290884. Retrieved 2023-07-26. γe = 9.780 326 7715 m/s² normal gravity at equator
The gravityofEarth, denoted by g, is the net acceleration that is imparted to objects due to the combined effect of gravitation (from mass distribution...
determines the motion of planets, stars, galaxies, and even light. On Earth, gravity gives weight to physical objects, and the Moon's gravity is responsible...
the Earth is due to the combined effects ofgravity and centrifugal acceleration from the rotation of the Earth (but the latter is small enough to be negligible...
The gravity anomaly at a location on the Earth's surface is the difference between the observed value ofgravity and the value predicted by a theoretical...
attraction of massive bodies in general GravityofEarth, the acceleration caused by the combination of gravitational attraction and centrifugal force of the...
Gravity ofEarth Horizon §§ Distance and Curvature Meridian arc Theoretical gravity History Pierre Bouguer Earth's circumference#History Earth's radius#History...
Newton's Third Law. The gravity assist maneuver was first used in 1959 when the Soviet probe Luna 3 photographed the far side ofEarth's Moon, and it was used...
Artificial gravity is the creation of an inertial force that mimics the effects of a gravitational force, usually by rotation. Artificial gravity, or rotational...
roughly a quarter as wide as Earth. The Moon's gravity helps stabilize Earth's axis, causes tides and gradually slows Earth's rotation. Tidal locking has...
because they have "escaped Earth'sgravity" is perpetuated further (and falsely) by almost universal misuse of the word "zero gravity" to describe the free-falling...
at a distance, of the gravitational field which it produces. In the relativistic sense, the "speed ofgravity" refers to the speed of a gravitational...
surface would take under the influence of the gravityofEarth, including gravitational attraction and Earth's rotation, if other influences such as winds...
of heavy bodies, such as the element earth and water, was related to their nature (gravity), which caused them to move downward toward the center of the...
theoretical gravity or normal gravity is an approximation of the true gravity on Earth's surface by means of a mathematical model representing Earth. The most...
The acceleration due to gravity on the surface of the Moon is approximately 1.625 m/s2, about 16.6% that on Earth's surface or 0.166 ɡ. Over the entire...
to 9.80665 m/s2. The value of the gn is defined as approximately equal to the acceleration due to gravity at the Earth's surface, although the actual...
per year over the last nine billion years. Physics portal GravityofEarth Standard gravity Gaussian gravitational constant Orbital mechanics Escape velocity...
1960s is close to 1/298.25. Earth is massive enough that the pull ofgravity maintains its roughly spherical shape. Most of its deviation from spherical...
part per million. The mass ofEarth is measured indirectly by determining other quantities such as Earth's density, gravity, or gravitational constant...
by the force ofgravity if it is resting on a flat, horizontal surface, because it is an equipotential surface. For the gravityofEarth, the corresponding...
children born and raised in low gravity such as on Titan would not be well adapted for life under the higher gravityofEarth. In situ energy resources on...
the constant of gravitation. On Earth the effect on gravityof elevation is 0.3086 mGal m−1 decrease when going up, minus the gravityof the Bouguer plate...
Entropic gravity, also known as emergent gravity, is a theory in modern physics that describes gravity as an entropic force—a force with macro-scale homogeneity...
of 60,000 km (37,000 mi), the gravityofEarth intervenes enough to make lunar orbits unstable at a distance of 690 km (430 mi). Orbits around Earth-Moon...
A gravity train is a theoretical means of transportation for purposes of commuting between two points on the surface of a sphere, by following a straight...
objects, for example the Newtonian gravity centre of the whole Earth (physical barycentre) or the Newtonian gravity centre of only the continents as uniform...
Global Information
