Gravitation is a natural phenomenon by which all objects with mass attract each other. In everyday life, gravitation is most familiar as the agency that gives objects weight. It is responsible for keeping the Earth and the other planets in their orbits around the Sun; for keeping the Moon in its orbit around the Earth, for the formation of tides; for convection (by which hot fluids rise); for heating the interiors of forming stars and planets to very high temperatures; and for various other phenomena that we observe. Gravitation is also the reason for the very existence of the Earth, the Sun, and most macroscopic objects in the universe; without it, matter would not have coalesced into these large masses and life, as we know it, would not exist. In general and scientific usage: Casually, gravity and gravitation are used as synonyms. ... Gravitation may have several meanings: Gravitation - a physical force that is responsible for interactions between objects with mass. ... For other uses, see Phenomena (disambiguation). ... For other uses, see Mass (disambiguation). ... For other uses, see Weight (disambiguation). ... Two bodies with a slight difference in mass orbiting around a common barycenter. ... This article is about Earths moon. ... This article is about tides in the ocean. ... Convection in the most general terms refers to the movement of currents within fluids (i. ... This article is about Earth as a planet. ... Sol redirects here. ... For other uses, see Universe (disambiguation). ... This article is about life in general. ...

Modern physics describes gravitation using the general theory of relativity, but the much simpler Newton's law of universal gravitation provides an excellent approximation in most cases. A magnet levitating above a high-temperature superconductor demonstrates the Meissner effect. ... General relativity (GR) or general relativity theory (GRT) is the theory of gravitation published by Albert Einstein in 1915. ... Isaac Newtons theory of universal gravitation (part of classical mechanics) states the following: Every single point mass attracts every other point mass by a force pointing along the line combining the two. ...

In scientific usage gravitation and gravity are distinct. "Gravitation" is the attractive influence that all objects exert on each other, while "gravity" specifically refers to a force which all massive objects (objects with mass) are theorized to exert on each other to cause gravitation. Although these terms are interchangeable in everyday use, in theories other than Newton's, gravitation is caused by factors other than gravity. For example in general relativity, gravitation is due to spacetime curvatures which causes inertially moving objects to tend to accelerate towards each other. Another (discredited) example is Le Sage's theory of gravitation, in which massive objects are effectively pushed towards each other. For other uses, see Force (disambiguation). ... For a less technical and generally accessible introduction to the topic, see Introduction to general relativity. ... This article is about inertia as it applies to local motion. ... Le Sages theory of gravitation is the most common name for the kinetic theory of gravity originally proposed by Nicolas Fatio de Duillier in 1690 and later by Georges-Louis Le Sage in 1748. ...

Gravitation keeps the planets in orbit about the Sun. (Not to scale)

Image File history File linksMetadata Download high-resolution version (1440x904, 254 KB) Edited Solar_sys. ... Image File history File linksMetadata Download high-resolution version (1440x904, 254 KB) Edited Solar_sys. ...

History of gravitational theory

Main article: History of gravitational theory

In physics, theories of gravitation postulate mechanisms of interaction governing the movements of bodies with mass. ...

Early history

Efforts to understand gravity began in ancient times. Philosophers in ancient India made attempts to explain the phenomenon from the 8th century BC.^[1] According to Kanada, founder of the Vaisheshika school, "Weight causes falling; it is imperceptible and known by inference."^[2] The term Indian philosophy may refer to any of several traditions of philosophical thought, including: Hindu philosophy Buddhist philosophy Jain philosophy Sikh philosophy Carvaka atheist philosophy Lokayata materialist philosophy Tantric religious philosophy Bhakti religious philosophy Sufi religious philosophy Ahmadi religious philosophy Political and military philosophy such as that of Chanakya... In prehistoric times, advice and knowledge was passed from generation to generation in an oral tradition. ... (2nd millennium BC - 1st millennium BC - 1st millennium) Ruins of the training grounds at Olympia, Greece. ... Kanada (also transliterated as Kanad and in other ways; Sanskrit कणाद) was a Hindu sage who founded the philosophical school of Vaisheshika. ... Vaisheshika, also Vaisesika, (Sanskrit: वैशॆषिक)is one of the six Hindu schools of philosophy (orthodox Vedic systems) of India. ... For other uses, see Mass (disambiguation). ... Inference is the act or process of deriving a conclusion based solely on what one already knows. ...

In the 4th century BC, the Greek philosopher Aristotle believed that there was no effect without a cause, and therefore no motion without a force. He hypothesized that everything tried to move towards its proper place in the crystalline spheres of the heavens, and that physical bodies fell toward the center of the Earth in proportion to their weight. For other uses, see Aristotle (disambiguation). ... A result is the final consequence of a sequence of actions or events (broadly incidents and accidents) expressed qualitatively or quantitatively, being a loss, injury, disadvantage, advantage, gain, victory or simply a value. ... This article or section is in need of attention from an expert on the subject. ... For other uses, see Force (disambiguation). ... For other uses, see Sphere (disambiguation). ... This article is about Earth as a planet. ... For other uses, see Weight (disambiguation). ...

Brahmagupta, in the Brahmasphuta Siddhanta (628 AD), responded to critics of the heliocentric system of Aryabhata (476–550 AD) stating that "all heavy things are attracted towards the center of the earth" and that "all heavy things fall down to the earth by a law of nature, for it is the nature of the earth to attract and to keep things, as it is the nature of water to flow, that of fire to burn, and that of wind to set in motion... The earth is the only low thing, and seeds always return to it, in whatever direction you may throw them away, and never rise upwards from the earth."^[3][4] Brahmagupta (ब्रह्मगुप्त) ( ) (589–668) was an Indian mathematician and astronomer. ... The main work of Brahmagupta, Brahmasphutasiddhanta (The Opening of the Universe), written in 628, contains some remarkably advanced ideas, including a good understanding of the mathematical role of zero, rules for manipulating both positive and negative numbers, a method for computing square roots, methods of solving linear and some quadratic... Heliocentric Solar System Heliocentrism (lower panel) in comparison to the geocentric model (upper panel) In astronomy, heliocentrism is the theory that the sun is at the center of the Universe and/or the Solar System. ... For other uses, see Aryabhata (disambiguation). ...

In the 9th century, the eldest Banū Mūsā brother, Muhammad ibn Musa, in his Astral Motion and The Force of Attraction, discovered that there was a force of attraction between heavenly bodies,^[5] foreshadowing Newton's law of universal gravitation.^[6] In the 1000s, the Iraqi scientist Ibn al-Haytham (Alhacen), in the Mizan al-Hikmah, discussed the theory of attraction between masses, and it seems that he was aware of the magnitude of acceleration due to gravity.^[7] In 1121, Al-Khazini, in The Book of the Balance of Wisdom, differentiated between force, mass, and weight,^[8] and discovered that gravity varies with the distance from the centre of the Earth,^[9] though he believed that the weight of heavy bodies increase as they are farther from the centre of the Earth.^[10] It has been suggested that Ahmad ibn MÅ«sā ibn Shākir be merged into this article or section. ... It has been suggested that this article or section be merged into BanÅ« MÅ«sā. (Discuss) Ja‘far Muḥammad ibn MÅ«sā ibn Shākir (800 - 873) (Arabic: ) was a 9th century Persian astronomer, engineer, mathematician and physicist from Baghdad, the eldest of the BanÅ« MÅ«sā brothers. ... Isaac Newtons theory of universal gravitation (part of classical mechanics) states the following: Every single point mass attracts every other point mass by a force pointing along the line combining the two. ... In the history of science, Islamic science refers to the science developed under the Islamic civilisation between the 8th and 15th centuries (the Islamic Golden Age). ... (Arabic: أبو علي الحسن بن الحسن بن الهيثم, Latinized: Alhacen or (deprecated) Alhazen) (965 – 1039), was an Arab[1] Muslim polymath[2][3] who made significant contributions to the principles of optics, as well as to anatomy, astronomy, engineering, mathematics, medicine, ophthalmology, philosophy, physics, psychology, visual perception, and to science in general with his introduction of the... For other uses, see Mass (disambiguation). ... The magnitude of a mathematical object is its size: a property by which it can be larger or smaller than other objects of the same kind; in technical terms, an ordering of the class of objects to which it belongs. ... Acceleration is the time rate of change of velocity and/or direction, and at any point on a velocity-time graph, it is given by the slope of the tangent to the curve at that point. ... This article is about a 12th century scientist. ... For other uses, see Force (disambiguation). ... For other uses, see Mass (disambiguation). ... For other uses, see Weight (disambiguation). ...

Scientific revolution

Modern work on gravitational theory began with the work of Galileo Galilei in the late 16th century and early 17th century. In his famous (though probably apocryphal) experiment dropping balls from the Tower of Pisa, and later with careful measurements of balls rolling down inclines, Galileo showed that gravitation accelerates all objects at the same rate. This was a major departure from Aristotle's belief that heavier objects are accelerated faster. (Galileo correctly postulated air resistance as the reason that lighter objects may fall more slowly in an atmosphere.) Galileo's work set the stage for the formulation of Newton's theory of gravity. Galileo redirects here. ... The Leaning Tower of Pisa (Italian: ) or simply The Tower of Pisa (La Torre di Pisa) is the campanile, or freestanding bell tower, of the cathedral of the Italian city of Pisa. ... Duquesne Incline, Pittsburgh, Pennsylvania with full length parallel tracks A funicular, also called funicular railway or inclined railway, inclined plane, or in England a cliff railway, consists of a system of transportation in which cables attach to a tram-like vehicle on rails to move it up and down a...

Newton's theory of gravitation

Main article: Newton's law of universal gravitation

In 1687, English mathematician Sir Isaac Newton published Principia, which hypothesizes the inverse-square law of universal gravitation. In his own words, “I deduced that the forces which keep the planets in their orbs must be reciprocally as the squares of their distances from the centers about which they revolve; and thereby compared the force requisite to keep the Moon in her orb with the force of gravity at the surface of the Earth; and found them answer pretty nearly.” Isaac Newtons theory of universal gravitation (part of classical mechanics) states the following: Every single point mass attracts every other point mass by a force pointing along the line combining the two. ... Sir Isaac Newton in Knellers portrait of 1689. ... Newtons own copy of his Principia, with handwritten corrections for the second edition. ... This diagram shows how the law works. ...

Newton's theory enjoyed its greatest success when it was used to predict the existence of Neptune based on motions of Uranus that could not be accounted by the actions of the other planets. Calculations by John Couch Adams and Urbain Le Verrier both predicted the general position of the planet, and Le Verrier's calculations are what led Johann Gottfried Galle to the discovery of Neptune. For other uses, see Neptune (disambiguation). ... For other uses, see Uranus (disambiguation). ... John Couch Adams (June 5, 1819 – January 21, 1892), was a British mathematician and astronomer. ... Urbain Le Verrier. ... Johann Gottfried Galle Johann Gottfried Galle (June 9, 1812 in Radis, Saxony-Anhalt – July 10, 1910 in Potsdam, Brandenburg) was a German astronomer at the Berlin Observatory who, with the assistance of student Heinrich Louis dArrest, was the first person to view the planet Neptune, and know what he...

Ironically, it was another discrepancy in a planet's orbit that helped to point out flaws in Newton's theory. By the end of the 19th century, it was known that the orbit of Mercury could not be accounted for entirely under Newton's theory, but all searches for another perturbing body (such as a planet orbiting the Sun even closer than Mercury) had been fruitless. The issue was resolved in 1915 by Albert Einstein's new General Theory of Relativity, which accounted for the discrepancy in Mercury's orbit. This article is about the planet. ... Sol redirects here. ... “Einstein” redirects here. ... For a less technical and generally accessible introduction to the topic, see Introduction to general relativity. ...

Although Newton's theory has been superseded, most modern non-relativistic gravitational calculations are still made using Newton's theory because it is a much simpler theory to work with than General Relativity, and gives sufficiently accurate results for most applications. For a less technical and generally accessible introduction to the topic, see Introduction to general relativity. ...

General relativity

Main article: Introduction to general relativity

In general relativity, the effects of gravitation are ascribed to spacetime curvature instead of a force. The starting point for general relativity is the equivalence principle, which equates free fall with inertial motion. The issue that this creates is that free-falling objects can accelerate with respect to each other. In Newtonian physics, no such acceleration can occur unless at least one of the objects is being operated on by a force (and therefore is not moving inertially). Newton’s conception and quantification of gravitation held until the beginning of the 20th century, when Albert Einstein extended the special relativity to form the general relativity (GR) theory. ... For a less technical and generally accessible introduction to the topic, see Introduction to general relativity. ... For other uses of this term, see Spacetime (disambiguation). ... In mathematics, curvature refers to a number of loosely related concepts in different areas of geometry. ... In the physics of relativity, the equivalence principle is applied to several related concepts dealing with gravitation and the uniformity of physical measurements in different frames of reference. ... Classical mechanics is a model of the physics of forces acting upon bodies. ...

To deal with this difficulty, Einstein proposed that spacetime is curved by matter, and that free-falling objects are moving along locally straight paths in curved spacetime. (This type of path is called a geodesic.) More specifically, Einstein discovered the field equations of general relativity, which relate the presence of matter and the curvature of spacetime and are named after him. The Einstein field equations are a set of 10 simultaneous, non-linear, differential equations. The solutions of the field equations are the components of the metric tensor of spacetime. A metric tensor describes a geometry of spacetime. The geodesic paths for a spacetime are calculated from the metric tensor. In physics, and specifically general relativity, geodesics are the world lines of a particle free from all external force. ... A field equation is an equation in a physical theory that describes how a fundamental force (or a combination of such forces) interacts with matter. ... The Einstein field equations (EFE) or Einsteins equations are a set of ten equations in Einsteins theory of general relativity in which the fundamental force of gravitation is described as a curved spacetime caused by matter and energy. ... In mathematics, simultaneous equations are a set of equations where variables are shared. ... In mathematics, a nonlinear system is one whose behavior cant be expressed as a sum of the behaviors of its parts (or of their multiples. ... Visualization of airflow into a duct modelled using the Navier-Stokes equations, a set of partial differential equations. ... In general relativity, the metric tensor (or simply the metric) is the fundamental object of study. ...

Notable solutions of the Einstein field equations include:

• The Schwarzschild solution, which describes spacetime surrounding a spherically symmetric non-rotating uncharged massive object. For compact enough objects, this solution generated a black hole with a central singularity. For radial distances from the center which are much greater than the Schwarzschild radius, the accelerations predicted by the Schwarzschild solution are practically identical to those predicted by Newton's theory of gravity.
• The Reissner-Nordström solution, in which the central object has an electrical charge. For charges with a geometrized length which are less than the geometrized length of the mass of the object, this solution produces black holes with two event horizons.
• The Kerr solution for rotating massive objects. This solution also produces black holes with multiple event horizons.
• The Kerr-Newman solution for charged, rotating massive objects. This solution also produces black holes with multiple event horizons.
• The cosmological Robertson-Walker solution, which predicts the expansion of the universe.

General relativity has enjoyed much success because of how its predictions of phenomena which are not called for by the theory of gravity have been regularly confirmed. For example: Introduction In Einsteins theory of general relativity, the Schwarzschild metric is the most general static, spherically symmetric solution of the vacuum field equations. ... In mechanics and geometry, the rotation group is the set of all rotations of 3-dimensional Euclidean space, R3. ... This article is about rotation as a movement of a physical body. ... For other uses, see Black hole (disambiguation). ... A gravitational singularity (sometimes spacetime singularity) is, approximately, a place where quantities which are used to measure the gravitational field become infinite. ... The Schwarzschild radius (sometimes inappropriately referred to as the gravitational radius[1]) is a characteristic radius associated with every mass. ... In physics and astronomy, a Reissner-Nordström black hole, discovered by Gunnar Nordström and Hans Reissner, is a black hole that carries mass , electric charge , and no angular momentum. ... In physics, especially in the general theory of relativity, geometrized units or geometric units constitute a physical unit system in which all physical quantities are identified with geometric quantities such as areas, lengths, dimensionless numbers, path curvatures, or sectional curvatures. ... This article is on the film Event Horizon. ... In general relativity, the Kerr metric (or Kerr vacuum) describes the geometry of spacetime around a rotating massive body, such as a rotating black hole. ... The Kerr-Newman metric is a solution of Einsteins general relativity field equation that describes the spacetime geometry around a charged (), rotating () black hole of mass m. ... This article is about the physics subject. ... The Friedmann-Lemaître-Robertson-Walker (FLRW) metric describes a homogeneous, isotropic expanding/contracting universe. ... For other uses, see Universe (disambiguation). ...

• General relativity accounts for the anomalous perihelion precession of the planet Mercury.
• The prediction that time runs slower at lower potentials has been confirmed by the Pound-Rebka experiment, the Hafele-Keating experiment, and the GPS.
• The prediction of the deflection of light was first confirmed by Arthur Eddington in 1919, and has more recently been strongly confirmed through the use of a quasar which passes behind the Sun as seen from the Earth. See also gravitational lensing.
• The time delay of light passing close to a massive object was first identified by Irwin Shapiro in 1964 in interplanetary spacecraft signals.
• Gravitational radiation has been indirectly confirmed through studies of binary pulsars.
• The expansion of the universe (predicted by the Robertson-Walker metric) was confirmed by Edwin Hubble in 1929.

A diagram of Keplerian orbital elements. ... Precession redirects here. ... This article is about the planet. ... The Pound-Rebka experiment is a well known experiment in general relativity. ... The Hafele-Keating experiment was a test of the theory of relativity. ... Over fifty GPS satellites such as this NAVSTAR have been launched since 1978. ... One of Sir Arthur Stanley Eddingtons papers announced Einsteins theory of general relativity to the English-speaking world. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... Sol redirects here. ... This article is about Earth as a planet. ... A gravitational lens is formed when the light from a very distant, bright source (such as a quasar) is bent around a massive object (such as a massive galaxy) between the source object and the observer. ... This article or section is in need of attention from an expert on the subject. ... Irwin I. Shapiro is an American astrophysicist. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... It has been suggested that Radio pulsar be merged into this article or section. ... The Friedmann-Lemaître-Robertson-Walker (FLRW) metric describes a homogeneous, isotropic expanding/contracting universe. ... Edwin Powell Hubble (November 20, 1889 – September 28, 1953) was an American astronomer. ...

Gravity and quantum mechanics

Main articles: Graviton and Quantum gravity

Several decades after the discovery of general relativity it was realized that general relativity cannot be the complete theory of gravity because it is incompatible with quantum mechanics.^[11] Later it was understood that it is possible to describe gravity in the framework of quantum field theory like the other fundamental forces. In this framework the attractive force of gravity arises due to exchange of virtual gravitons, in the same way as the electromagnetic force arises from exchange of virtual photons.^[12][13] This reproduces general relativity in the classical limit. However, this approach fails at short distances of the order of the Planck length,^[14] where a more complete theory of quantum gravity is required. Many believe the complete theory to be string theory,^[15] or more currently M Theory. This article is about the hypothetical particle. ... Quantum gravity is the field of theoretical physics attempting to unify quantum mechanics, which describes three of the fundamental forces of nature, with general relativity, the theory of the fourth fundamental force: gravity. ... For a less technical and generally accessible introduction to the topic, see Introduction to quantum mechanics. ... Quantum field theory (QFT) is the quantum theory of fields. ... A fundamental interaction is a mechanism by which particles interact with each other, and which cannot be explained by another more fundamental interaction. ... In physics, a virtual particle is a particle which exists for such a short time and space that its energy and momentum do not have to obey the usual relationship. ... In physics, the graviton is a hypothetical elementary particle that transmits the force of gravity in most quantum gravity systems. ... In physics, the photon (from Greek φως, phōs, meaning light) is the quantum of the electromagnetic field; for instance, light. ... The classical limit is the ability of a physical theory to approximate or recover classical mechanics when considered over special values of its parameters. ... The Planck length, denoted by , is the unit of length approximately 1. ... Quantum gravity is the field of theoretical physics attempting to unify quantum mechanics, which describes three of the fundamental forces of nature, with general relativity, the theory of the fourth fundamental force: gravity. ... Interaction in the subatomic world: world lines of pointlike particles in the Standard Model or a world sheet swept up by closed strings in string theory This box:      String theory is a model of fundamental physics, whose building blocks are one-dimensional extended objects called strings, rather than the zero... This box:      For a less technical and generally accessible introduction to the topic, see Introduction to M-theory. ...

Specifics

Earth's gravity

Main article: Earth's gravity

Every planetary body, including the Earth, is surrounded by its own gravitational field, which exerts an attractive force on all objects. Assuming a spherically symmetrical planet (a reasonable approximation), the strength of this field at any given point is proportional to the planetary body's mass and inversely proportional to the square of the distance from the centre of the body. Earths gravity, denoted by g, refers to the attractive force that the Earth exerts on objects on or near its surface (or, more generally, objects anywhere in the Earths vicinity). ...

The strength of the gravitational field is numerically equal to the acceleration of objects under its influence, and its value at the Earth's surface, denoted g, is approximately 9.8 m/s² as the standard average. This means that, ignoring air resistance, an object falling freely near the earth's surface increases its velocity with 9.8 m/s (32 ft/s or 22 mi/h) for each second of its descent. Thus, an object starting from rest will attain a velocity of 9.8 m/s (32 ft/s) after one second, 19.6 m/s (64 ft/s) after two seconds, and so on, adding 9.8 m/s to each resulting velocity. According to Newton's 3rd Law, the Earth itself experiences an equal and opposite force to that acting on the falling object, meaning that the Earth also accelerates towards the object. However, because the mass of the Earth is huge, the acceleration of the Earth by this same force is negligible, when measured relative to the system's center of mass. g (also gee, g-force or g-load) is a non-SI unit of acceleration defined as exactly 9. ... In physics, the center of mass of a system of particles is a specific point at which, for many purposes, the systems mass behaves as if it were concentrated. ...

Equations for a falling body

Ball falling freely under gravity. See text for description.

Main article: Equations for a falling body

The kinematical and dynamical equations describing the trajectories of falling bodies are considerably simpler if the gravitational force is assumed constant. This assumption is reasonable for objects falling to Earth over the relatively short vertical distances of our everyday experience, but does not hold over larger distances, such as spacecraft trajectories, since the acceleration due to Earth's gravity is much smaller at large distances. Image File history File links Metadata Size of this preview: 178 × 598 pixelsFull resolution (819 × 2751 pixel, file size: 363 KB, MIME type: image/jpeg) Original photograph File historyClick on a date/time to view the file as it appeared at that time. ... Image File history File links Metadata Size of this preview: 178 × 598 pixelsFull resolution (819 × 2751 pixel, file size: 363 KB, MIME type: image/jpeg) Original photograph File historyClick on a date/time to view the file as it appeared at that time. ... Under normal earth-bound conditions, when objects move owing to a constant gravitational force a set of dynamical equations describe the resultant trajectories. ... This article is about Earth as a planet. ...

Under an assumption of constant gravity, Newton’s law of gravitation simplifies to F = mg, where m is the mass of the body and g is a constant vector with an average magnitude of 9.8 m/s². The acceleration due to gravity is equal to this g. An initially-stationary object which is allowed to fall freely under gravity drops a distance which is proportional to the square of the elapsed time. The image on the right, spanning half a second, was captured with a stroboscopic flash at 20 flashes per second. During the first 1/20th of a second the ball drops one unit of distance (here, a unit is about 12 mm); by 2/20ths it has dropped at total of 4 units; by 3/20ths, 9 units and so on. Newtons law of universal gravitation states the following: Every point mass attracts every other point mass by a force directed along the line connecting the two. ... For other uses, see Mass (disambiguation). ...

Under the same constant gravity assumptions, the potential energy, E_p, of a body at height h is given by E_p = mgh (or E_p = Wh, with W meaning weight). This expression is valid only over small distances h from the surface of the Earth. Similarly, the expression h = v² / 2g for the maximum height reached by a vertically projected body with velocity v is useful for small heights and small initial velocities only. In case of large initial velocities we have to use the principle of conservation of energy to find the maximum height reached. This same expression can be solved for v to determine the velocity of an object dropped from a height h immediately before hitting the ground, , assuming negligible air resistance. Potential energy can be thought of as energy stored within a physical system. ...

Gravity and astronomy

Main article: Gravity (astronomy)

The discovery and application of Newton's law of gravity accounts for the detailed information we have about the planets in our solar system, the mass of the Sun, the distance to stars, quasars and even the theory of dark matter. Although we have not traveled to all the planets nor to the Sun, we know their masses. These masses are obtained by applying the laws of gravity to the measured characteristics of the orbit. In space an object maintains its orbit because of the force of gravity acting upon it. Planets orbit stars, stars orbit galactic centers, galaxies orbit a center of mass in clusters, and clusters orbit in superclusters. The force of gravity is proportional to the mass of an object and inversely proportional to the square of the distance between the objects. Albireo, binary star system. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... For other uses, see Dark matter (disambiguation). ... Two bodies with a slight difference in mass orbiting around a common barycenter. ... For the series of books, see Galactic Center Saga. ... For other uses, see Galaxy (disambiguation). ... Superclusters are large groupings of smaller galaxy groups and clusters, and are among the largest structures of the cosmos. ...

Gravitational radiation

Main article: Gravitational wave

In general relativity, gravitational radiation is in situations where the curvature of spacetime is oscillating, such as is the case with co-orbiting objects. The amount of gravitational radiation emitted by the solar system is far too small to measure. However, gravitational radiation has been indirectly observed as an energy loss over time in binary pulsar systems such as PSR 1913+16. It is believed that neutron star mergers and black hole formation may create detectable amounts of gravitational radiation. Gravitational radiation observatories such as LIGO have been created to study the problem. No confirmed detections have been made of this hypothetical radiation, but as the science behind LIGO is refined and as the instruments themselves are endowed with greater sensitivity over the next decade, this may change. This box:      In physics, a gravitational wave is a fluctuation in the curvature of spacetime which propagates as a wave, traveling outward from a moving object or system of objects. ... This article is about the Solar System. ... PSR B1913+16 is a pulsar in a binary star system, in orbit with another star around a common center of mass. ... For the story by Larry Niven, see Neutron Star (story). ... For other uses, see Black hole (disambiguation). ... LIGO stands for Lesser Inner Greater Outer. ...

Alternative theories

Main article: Alternatives to general relativity

Alternatives to general relativity are physical theories that attempt to describe the phenomena of gravitation in competition to Einsteins theory of general relativity. ...

Historical alternative theories

• Aristotelian theory of gravity
• Le Sage's theory of gravitation (1784) also called LeSage gravity, proposed by Georges-Louis Le Sage, based on a fluid-based explanation where a light gas fills the entire universe.
• Nordström's theory of gravitation (1912, 1913), an early competitor of general relativity.
• Whitehead's theory of gravitation (1922), another early competitor of general relativity.

The Aristotelian theory of gravity was that all bodies move towards their natural place. ... Le Sages theory of gravitation is the most common name for the kinetic theory of gravity originally proposed by Nicolas Fatio de Duillier in 1690 and later by Georges-Louis Le Sage in 1748. ... Georges-Louis Lesage (1724 - 1803) was a Swiss physicist. ... In theoretical physics, Nordströms theory of gravitation was an early competitor of general relativity. ... In theoretical physics, Whiteheads theory of gravitation was introduced by the distinguished mathematician and philosopher Alfred North Whitehead in 1922. ...

Recent alternative theories

• Brans-Dicke theory of gravity (1961)
• Induced gravity (1967), a proposal by Andrei Sakharov according to which general relativity might arise from quantum field theories of matter.
• Rosen bi-metric theory of gravity
• In the modified Newtonian dynamics (MOND) (1981), Mordehai Milgrom proposes a modification of Newton's Second Law of motion for small accelerations.
• The new and highly controversial Process Physics theory attempts to address gravity
• The self-creation cosmology theory of gravity (1982) by G.A. Barber in which the Brans-Dicke theory is modified to allow mass creation.
• Nonsymmetric gravitational theory (NGT) (1994) by John Moffat
• The satirical theory of Intelligent falling (2002, in its first incarnation as "Intelligent grappling")
• Tensor-vector-scalar gravity (TeVeS) (2004), a relativistic modification of MOND by Jacob Bekenstein

This article or section is in need of attention from an expert on the subject. ... Sakharov proposed the idea of induced gravity as an alternative theory of quantum gravity. ... Andrei Sakharov, 1943 For the historian, see Andrey Nikolayevich Sakharov. ... For a less technical and generally accessible introduction to the topic, see Introduction to general relativity. ... Quantum field theory (QFT) is the quantum theory of fields. ... In physics, Modified Newtonian dynamics (MOND) is a theory that proposes a modification of Newtons Second Law of Dynamics, to explain the galaxy rotation problem. ... Mordehai Milgrom is a professor at the Weizmann Institute department of Condensed Matter Physics, located at 76100 Rehovot in Israel. ... Newtons laws of motion are the three scientific laws which Isaac Newton discovered concerning the behaviour of moving bodies. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Self-creation cosmology (SCC) theories are gravitational theories in which the universes mass is created out of its self-contained gravitational and scalar fields. ... This article or section is in need of attention from an expert on the subject. ... Nonsymmetric Gravitational Theory is a modification of Einsteins theory of General Relativity that tries to explain the mystery of Dark Matter. ... Intelligent falling (IF) is a parody of the intelligent design (ID) movement. ... This article or section is in need of attention from an expert on the subject. ... Jacob David Bekenstein (born May 1, 1947) is a physicist who has contributed to the foundation of black hole thermodynamics and to other aspects of the connections between information and gravitation. ...

See also

Gravitation Portal

Image File history File links Portal. ... Anti-gravity is the hypothetical idea, often considered pseudoscientific, of creating a place or object that is free from the force of gravity. ... Artificial gravity is a simulation of gravity in outer space or free-fall. ... Space Shuttle Atlantis launches on mission STS-71. ... For a less technical and generally accessible introduction to the topic, see Introduction to general relativity. ... The term g force or gee force refers to the symbol g, the force of acceleration due to gravity at the earths surface. ... Acceleration is the time rate of change of velocity and/or direction, and at any point on a velocity-time graph, it is given by the slope of the tangent to the curve at that point. ... A gravitational field is a model used within physics to explain how gravity exists in the universe. ... This box:      In physics, a gravitational wave is a fluctuation in the curvature of spacetime which propagates as a wave, traveling outward from a moving object or system of objects. ... The gravitational binding energy of an object is the amount of energy required to accelerate every component of that object to the escape velocity of every other component. ... Established in 1948 by businessman Roger Babson (also founder of Babson College), the Gravity Research Foundation was an organization designed to find ways to block or reduce the effect of gravity. ... In vector calculus, the divergence theorem, also known as Gauss theorem, Ostrogradskys theorem, or Gauss-Ostrogradsky theorem is a result that relates the flow (that is, flux) of a vector field through a surface to the behaviour of the vector field inside the surface. ... Johannes Keplers primary contributions to astronomy/astrophysics were his three laws of planetary motion. ... Newtons First and Second laws, in Latin, from the original 1687 edition of the Principia Mathematica. ... This article is about the problem in classical mechanics. ... The Pioneer anomaly or Pioneer effect is the observed deviation from expectations of the trajectories of various unmanned spacecraft visiting the outer solar system, notably Pioneer 10 and Pioneer 11. ... Scalar theories of gravitation are models of gravitation in which the gravitational field is modelled as arising out of a single scalar value. ... The speed of gravity is the speed at which changes in the location of an object propagate their gravitational effects to all other objects in the Universe. ... In astrodynamics, the standard gravitational parameter () of a celestial body is the product of the gravitational constant () and the mass : The units of the standard gravitational parameter are km3s-2 Small body orbiting a central body Under standard assumptions in astrodynamics we have: where: is the mass of the orbiting... g (also gee, g-force or g-load) is a non-SI unit of acceleration defined as exactly 9. ... For other uses, see Weight (disambiguation). ... Astronauts on the International Space Station display an example of weightlessness. ... In celestial mechanics, the Lagrangian points, (also Lagrange point, L-point, or libration point) are the five stationary solutions of the circular restricted three-body problem. ...

Notes

Max Born (December 11, 1882 – January 5, 1970) was a German physicist and mathematician. ...

References

Subhash Kak (सुभाष काक) (born March 26, 1947, Srinagar, Kashmir) is Delaune Distinguished Professor of Electrical Engineering and Professor in the Asian Studies and Cognitive Science Programs at Louisiana State University, Baton Rouge. ... arXiv (pronounced archive, as if the X were the Greek letter χ) is an archive for electronic preprints of scientific papers in the fields of physics, mathematics, computer science and quantitative biology which can be accessed via the Internet. ... For other uses, see LSU. Louisiana State University and Agricultural and Mechanical College, generally known as Louisiana State University or LSU, is a public, coeducational university located in Baton Rouge, Louisiana and the main campus of the Louisiana State University System. ... Brahmagupta (ब्रह्मगुप्त) ( ) (589–668) was an Indian mathematician and astronomer. ... The main work of Brahmagupta, Brahmasphutasiddhanta (The Opening of the Universe), written in 628, contains some remarkably advanced ideas, including a good understanding of the mathematical role of zero, rules for manipulating both positive and negative numbers, a method for computing square roots, methods of solving linear and some quadratic... A statue of Biruni adorns the southwest entrance of Laleh Park in Tehran. ... Robert Briffault (1876 - 11 December 1948) was a French novelist, social anthropologist and surgeon. ... Routledge is an imprint for books in the humanities part of the Taylor & Francis Group, which also has Brunner-Routledge, RoutledgeCurzon and RoutledgeFalmer divisions. ... Donald Routledge Hill (1922–1994) was an engineer and historian of science. ... Edinburgh University Press is a publisher that is part of the University of Edinburgh. ... Look up Cf. ...

External links

• Chapter 10. Gravity, from Light and Matter: educational materials for physics and astronomy
• Newton's Law of Universal GravitationPDF (194 KiB) on Project PHYSNET
• Gravity Probe B Experiment The Official Einstein website from Stanford University
• Center for Gravity, Electrical, and Magnetic Studies
• Gravity for kids (flash)
• Ask a scientist, Physics Archive
• How stuff works: How does gravity work?
• Alternative theory of gravity explains large structure formation -- without dark matter PhysOrg.com
• Do it yourself, gravitation experiment