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{{Portal|Gravitation}} | |||
In [[physics]], '''theories of gravitation''' postulate mechanisms of interaction governing the movements of bodies with mass. There have been numerous theories of [[gravitation]] since ancient times. | |||
==Antiquity== | |||
{{See also|Aristotelian physics}} | |||
In the 4th century BC, the [[ancient Greece|Greek]] philosopher [[Aristotle]] believed that there is no [[Causality|effect]] or [[Motion (physics)|motion]] without a [[causality|cause]]. The cause of the downward motion of heavy bodies, such as the element [[Earth (classical element)|earth]], was related to their [[Nature (philosophy)|nature]], which caused them to move downward toward the center of the universe, which was their natural place. Conversely, light bodies such as the element [[Fire (classical element)|fire]], move by their nature upward toward the inner surface of the [[Celestial spheres|sphere]] of the Moon. Thus in Aristotle's system heavy bodies are not attracted to the earth by an external force of gravity, but tend toward the center of the universe because of an inner ''gravitas'' or heaviness.<ref>Edward Grant, ''The Foundations of Modern Science in the Middle Ages'', (Cambridge: Cambridge Univ. Pr., 1996), pp. 60-1.</ref><ref>Olaf Pedersen, ''Early Physics and Astronomy'', (Cambridge: Cambridge Univ. Pr., 1993), p. 130</ref> | |||
In Book VII of his ''[[De Architectura]]'', the Roman engineer and architect [[Vitruvius]] contends that gravity is not dependent on a substance's "weight" but rather on its "nature" (cf. [[specific gravity]]). | |||
<blockquote> | |||
If the [[Mercury (element)|quicksilver]] is poured into a vessel, and a stone weighing one hundred pounds is laid upon it, the stone swims on the surface, and cannot depress the liquid, nor break through, nor separate it. If we remove the hundred pound weight, and put on a scruple of gold, it will not swim, but will sink to the bottom of its own accord. Hence, it is undeniable that the gravity of a substance depends not on the amount of its weight, but on its nature.<ref> | |||
{{Cite book | last = Vitruvius| first = Marcus Pollio | author-link = Marcus Vitruvius Pollio | editor = Alfred A. Howard | title = De Architectura libri decem | trans_title = Ten Books on Architecture | place = Harvard University, Cambridge | publisher = Harvard University Press | year = 1914 | chapter = 7 | page = 215 | url = http://www.gutenberg.org/files/20239/20239-h/29239-h.htm#Page_215 | others = Herbert Langford Warren, Nelson Robinson (illus), Morris Hicky Morgan | work = VII | |||
}} | |||
</ref></blockquote> | |||
In the 7th Century the [[Indian mathematician]] [[Brahmagupta]] stated "Bodies fall towards the earth as it is in the nature of the earth to attract bodies, just as it is in the nature of water to flow."<ref>Thomas Khoshy, ''Elementary Number Theory with Applications'', Academic Press, 2002, p. 567. ISBN 0-12-421171-2.</ref> | |||
==Modern era (Origin of Gravitation)== | |||
{{Unreferenced section|date=February 2009}} | |||
Gravity was described by the 11th century Indian Mathematician [[Bhāskara II|Bhaskaracharya]] in his book called ''Siddhantha Siromani.'' | |||
"Aakrishti sakthischa mahee thayaa yathkhastham guru swa abhimukham swa sakthyaa . aakrushyathe thath pathathi iti bhaathi same samanthaath kwa pathathi ayam khe" is the verse which describes that the earth attracts the solid objects in the sky by its own force towards itself. Bhaskaracharya further discusses the forces between the celestial bodies using a question: Where can the celestial bodies fall since they attract each other? <ref>{{cite book|last=Sharma|first=Shashi S|title=Mathematics & Astronomers of Ancient India|year=2007|publisher=Pithambar publishing company (P) limited|location=New delhi|isbn=81-209-1421-X|url=http://books.google.com/?id=g9ykYZlzV1oC&printsec=frontcover#v=onepage&q&f=false}}</ref><ref>{{cite web|last=Gopalakrishnan|first=N|title=Indian discoveries|url=http://www.homebusinessandfamilylife.com/support-files/weclaimtheseareindiandiscoveries.pdf|publisher=Indian institute of scientific heritage|accessdate=8 August 2011}}</ref> | |||
Before 1543 in [[De revolutionibus orbium coelestium]] [[Nicolaus Copernicus|Copernicus]] wrote :''"...inter centrum gravitatis terrae, & centrum magnitudis..."'' | |||
During the 17th century, [[Galileo Galilei|Galileo]] found that, counter to Aristotle's teachings, all objects accelerated equally when falling. | |||
In the late 17th century, as a result of Robert Hooke's suggestion that there is a gravitational force which depends on the [[inverse-square law|inverse square]] of the [[distance]],<ref>{{Cite book| publisher = Cambridge University Press| isbn = 978-0-521-65696-2| last = Cohen| first = I. Bernard| coauthors = George Edwin Smith| title = The Cambridge Companion to Newton| year = 2002|pages = 11–12}}</ref> [[Isaac Newton]] was able to [[mathematical model|mathematically]] derive [[Johannes Kepler#Scientific work|Kepler's]] three [[kinematics|kinematic]] [[Kepler's laws of planetary motion|laws of planetary motion]], including the [[ellipse|elliptical]] [[orbits]] for the seven known [[planet]]s: | |||
{{quote|"I deduced that the forces which keep the planets in their orbs must be reciprocally as the squares of their distances from the centres 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 to answer pretty nearly." | |||
|Isaac Newton, 1666}} | |||
So Newton's original formula was: | |||
:<math>{\rm Force\,of\,gravity} \propto \frac{\rm mass\,of\,object\,1\,\times\,mass\,of\,object\,2}{\rm distance\,from\,centers^2}</math> | |||
where the symbol <math>\propto</math> means "is proportional to". | |||
To make this into an equal-sided formula or equation, there needed to be a multiplying factor or constant that would give the correct force of gravity no matter the value of the masses or distance between them. This [[gravitational constant]] was first measured in 1797 by [[Henry Cavendish]]. | |||
In 1907 [[Albert Einstein]], in what was described by him as "''the happiest thought of my life''", realized that an observer who is falling from the roof of a house experiences no gravitational field. In other words, gravitation was exactly equivalent to [[acceleration]]. Between 1911 and 1915 this idea, initially stated as the [[Equivalence principle]], was formally developed into Einstein's theory of [[general relativity]]. | |||
===Newton's theory of gravitation=== | |||
{{Main|Law of universal gravitation}} | |||
In 1687, English mathematician [[Sir Isaac Newton]] published ''[[Philosophiæ Naturalis Principia Mathematica|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.” | |||
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. | |||
Years later, it was another discrepancy in a planet's orbit that showed Newton's theory to be inaccurate. By the end of the 19th century, it was known that the orbit of [[Mercury (planet)|Mercury]] could not be accounted for entirely under Newtonian gravity, and all searches for another perturbing body (such as a planet orbiting the [[Sun]] even closer than Mercury) have been fruitless. This issue was resolved in 1915 by [[Albert Einstein]]'s new general theory of relativity, which accounted for the discrepancy in Mercury's orbit. | |||
[[Paul Dirac]] developed the hypothesis that gravitation should have slowly and steadily decreased over the course of the history of the universe.<ref>{{cite book |first=Heinz|last=Haber|title=Unser blauer Planet |trans_title=Our blue planet |edition=Rororo Taschenbuch Ausgabe [Rororo pocket edition] |series=Rororo Sachbuch [Rororo nonfiction] |year=1967 |origyear=1965 |publisher=[[Rowohlt Verlag]] |location=Reinbek |language=German |page=52 |trans_chapter=The expansion of the Earth |chapter=Die Expansion der Erde |quote=Der englische Physiker und Nobelpreisträger Dirac hat [...] vor über dreißig Jahren die Vermutung begründet, dass sich das universelle Maß der Schwerkraft im Laufe der Geschichte des Universums außerordentlich langsam, aber stetig verringert." '''English:''' "The English physicist and Nobel laureate Dirac has [...], more than thirty years ago, substantiated the assumption that the universal strength of gravity decreases very slowly, but steadily over the course of the history of the universe.|authorlink=Heinz Haber}}</ref> | |||
Although Newton's theory has been superseded, most modern non-relativistic gravitational calculations still use it because it is much easier to work with and is sufficiently accurate for most applications. | |||
===Mechanical explanations of gravitation=== | |||
{{Main|Mechanical explanations of gravitation}} | |||
The mechanical theories or explanations of the gravitation are attempts to explain the law of gravity by aid of basic mechanical processes, such as pushes, and without the use of any [[Action at a distance (physics)|action at a distance]]. These theories were developed from the 16th until the 19th century in connection with the [[aether theories]].<ref>{{Cite journal | author=Taylor, W. B. | title =Kinetic Theories of Gravitation | journal = Smithsonian | year =1876 | pages =205–282 | postscript=<!--None-->}}</ref> | |||
[[René Descartes]] (1644) and [[Christiaan Huygens]] (1690) used [[vortices]] to explain gravitation. | |||
[[Robert Hooke]] (1671) and [[James Challis]] (1869) assumed, that every body emits waves which lead to an attraction of other bodies. | |||
[[Nicolas Fatio de Duillier]] (1690) and [[Georges-Louis Le Sage]] (1748) proposed a [[Le Sage's theory of gravitation|corpuscular model]], using some sort of screening or shadowing mechanism. Later a similar model was created by [[Hendrik Lorentz]], who used [[electromagnetic radiation]] instead of the corpuscles. | |||
[[Isaac Newton]] (1675) and [[Bernhard Riemann]] (1853) argued that aether streams carry all bodies to each other. | |||
Newton (1717) and [[Leonhard Euler]] (1760) proposed a model, in which the aether loses density near the masses, leading to a net force directing to the bodies. | |||
[[Lord Kelvin]] (1871) proposed that every body pulsates, which might be an explanations of gravitation and the [[electric charges]]. | |||
However, those models were overthrown because most of them lead to an unacceptable amount of [[drag (physics)|drag]], which is not observed. Other models are violating the [[energy conservation law]] and are incompatible with modern [[thermodynamics]].<ref>{{Cite journal | author=Zenneck, J. | author-link =Jonathan Zenneck| title =Gravitation | journal =Encyklopädie der mathematischen Wissenschaften mit Einschluss ihrer Anwendungen | volume =5 | issue =1 | pages =25–67 | year =1903 | place=Leipzig | postscript=<!--None--> | url=http://dz-srv1.sub.uni-goettingen.de/sub/digbib/loader?did=D189514}}</ref> | |||
===General relativity=== | |||
{{Main|Introduction to general relativity}} | |||
In '''[[general relativity]]''', the effects of gravitation are ascribed to [[spacetime]] [[curvature]] instead of to 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). | |||
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 (general relativity)|geodesic]]). More specifically, Einstein and Hilbert discovered the [[field equation]]s of general relativity, which relate the presence of matter and the curvature of spacetime and are named after Einstein. The [[Einstein field equations]] are a set of 10 [[simultaneous equation|simultaneous]], [[Nonlinearity|non-linear]], [[differential equation]]s. The solutions of the field equations are the components of the [[metric tensor (general relativity)|metric tensor]] of spacetime. A metric tensor describes the geometry of spacetime. The geodesic paths for a spacetime are calculated from the metric tensor. | |||
Notable solutions of the Einstein field equations include: | |||
* The [[Schwarzschild solution]], which describes spacetime surrounding a [[spherical symmetry|spherically symmetric]] non-[[rotation|rotating]] uncharged massive object. For compact enough objects, this solution generated a [[black hole]] with a central [[gravitational singularity|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 black hole|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 an [[event horizon]] surrounding a [[Cauchy horizon]]. | |||
* The [[Kerr solution]] for rotating massive objects. This solution also produces black holes with multiple horizons. | |||
* The [[physical cosmology|cosmological]] [[Robertson-Walker coordinates|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: | |||
* General relativity accounts for the anomalous [[apsis|perihelion]] [[precession]] of the planet [[Mercury (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 [[pulsar]]s. | |||
* The expansion of the universe (predicted by the [[Robertson-Walker metric]]) was confirmed by [[Edwin Hubble]] in 1929. | |||
===Gravity and quantum mechanics=== | |||
{{Main|Graviton|Quantum gravity}} | |||
Several decades after the discovery of general relativity it was realized that it cannot be the complete theory of gravity because it is incompatible with [[quantum mechanics]].<ref name="Randall, Lisa 2005">{{cite book | author=Randall, Lisa | title=Warped Passages: Unraveling the Universe's Hidden Dimensions | publisher=Ecco | year=2005 | id=ISBN}}</ref> 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 particle|virtual]] [[gravitons]], in the same way as the electromagnetic force arises from exchange of virtual [[photons]].<ref>{{cite book |last= Feynman |first= R. P. |coauthors= Morinigo, F. B., Wagner, W. G., & Hatfield, B. |title= Feynman lectures on gravitation |publisher= Addison-Wesley |year= 1995 |isbn=0-201-62734-5 }}</ref><ref>{{cite book | author=Zee, A. |title=Quantum Field Theory in a Nutshell | publisher = Princeton University Press | year=2003 | id=ISBN}}</ref> This reproduces general relativity in the [[classical limit]]. However, this approach fails at short distances of the order of the [[Planck length]].<ref name="Randall, Lisa 2005"/> | |||
It is notable that in general relativity, gravitational radiation, which under the rules of quantum mechanics must be composed of gravitons, is created only 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. | |||
==References== | |||
{{Reflist}} | |||
{{theories of gravitation}} | |||
{{DEFAULTSORT:History Of Gravitational Theory}} | |||
[[Category:Theories of gravitation]] | |||
[[Category:History of physics]] | |||
Latest revision as of 09:40, 15 March 2013
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Antiquity
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In the 4th century BC, the Greek philosopher Aristotle believed that there is no effect or motion without a cause. The cause of the downward motion of heavy bodies, such as the element earth, was related to their nature, which caused them to move downward toward the center of the universe, which was their natural place. Conversely, light bodies such as the element fire, move by their nature upward toward the inner surface of the sphere of the Moon. Thus in Aristotle's system heavy bodies are not attracted to the earth by an external force of gravity, but tend toward the center of the universe because of an inner gravitas or heaviness.[1][2]
In Book VII of his De Architectura, the Roman engineer and architect Vitruvius contends that gravity is not dependent on a substance's "weight" but rather on its "nature" (cf. specific gravity).
If the quicksilver is poured into a vessel, and a stone weighing one hundred pounds is laid upon it, the stone swims on the surface, and cannot depress the liquid, nor break through, nor separate it. If we remove the hundred pound weight, and put on a scruple of gold, it will not swim, but will sink to the bottom of its own accord. Hence, it is undeniable that the gravity of a substance depends not on the amount of its weight, but on its nature.[3]
In the 7th Century the Indian mathematician Brahmagupta stated "Bodies fall towards the earth as it is in the nature of the earth to attract bodies, just as it is in the nature of water to flow."[4]
Modern era (Origin of Gravitation)
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Gravity was described by the 11th century Indian Mathematician Bhaskaracharya in his book called Siddhantha Siromani. "Aakrishti sakthischa mahee thayaa yathkhastham guru swa abhimukham swa sakthyaa . aakrushyathe thath pathathi iti bhaathi same samanthaath kwa pathathi ayam khe" is the verse which describes that the earth attracts the solid objects in the sky by its own force towards itself. Bhaskaracharya further discusses the forces between the celestial bodies using a question: Where can the celestial bodies fall since they attract each other? [5][6]
Before 1543 in De revolutionibus orbium coelestium Copernicus wrote :"...inter centrum gravitatis terrae, & centrum magnitudis..."
During the 17th century, Galileo found that, counter to Aristotle's teachings, all objects accelerated equally when falling.
In the late 17th century, as a result of Robert Hooke's suggestion that there is a gravitational force which depends on the inverse square of the distance,[7] Isaac Newton was able to mathematically derive Kepler's three kinematic laws of planetary motion, including the elliptical orbits for the seven known planets:
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So Newton's original formula was:
where the symbol means "is proportional to".
To make this into an equal-sided formula or equation, there needed to be a multiplying factor or constant that would give the correct force of gravity no matter the value of the masses or distance between them. This gravitational constant was first measured in 1797 by Henry Cavendish.
In 1907 Albert Einstein, in what was described by him as "the happiest thought of my life", realized that an observer who is falling from the roof of a house experiences no gravitational field. In other words, gravitation was exactly equivalent to acceleration. Between 1911 and 1915 this idea, initially stated as the Equivalence principle, was formally developed into Einstein's theory of general relativity.
Newton's theory of gravitation
Mining Engineer (Excluding Oil ) Truman from Alma, loves to spend time knotting, largest property developers in singapore developers in singapore and stamp collecting. Recently had a family visit to Urnes Stave Church. 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.”
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.
Years later, it was another discrepancy in a planet's orbit that showed Newton's theory to be inaccurate. By the end of the 19th century, it was known that the orbit of Mercury could not be accounted for entirely under Newtonian gravity, and all searches for another perturbing body (such as a planet orbiting the Sun even closer than Mercury) have been fruitless. This issue was resolved in 1915 by Albert Einstein's new general theory of relativity, which accounted for the discrepancy in Mercury's orbit.
Paul Dirac developed the hypothesis that gravitation should have slowly and steadily decreased over the course of the history of the universe.[8]
Although Newton's theory has been superseded, most modern non-relativistic gravitational calculations still use it because it is much easier to work with and is sufficiently accurate for most applications.
Mechanical explanations of gravitation
Mining Engineer (Excluding Oil ) Truman from Alma, loves to spend time knotting, largest property developers in singapore developers in singapore and stamp collecting. Recently had a family visit to Urnes Stave Church. The mechanical theories or explanations of the gravitation are attempts to explain the law of gravity by aid of basic mechanical processes, such as pushes, and without the use of any action at a distance. These theories were developed from the 16th until the 19th century in connection with the aether theories.[9]
René Descartes (1644) and Christiaan Huygens (1690) used vortices to explain gravitation. Robert Hooke (1671) and James Challis (1869) assumed, that every body emits waves which lead to an attraction of other bodies. Nicolas Fatio de Duillier (1690) and Georges-Louis Le Sage (1748) proposed a corpuscular model, using some sort of screening or shadowing mechanism. Later a similar model was created by Hendrik Lorentz, who used electromagnetic radiation instead of the corpuscles. Isaac Newton (1675) and Bernhard Riemann (1853) argued that aether streams carry all bodies to each other. Newton (1717) and Leonhard Euler (1760) proposed a model, in which the aether loses density near the masses, leading to a net force directing to the bodies. Lord Kelvin (1871) proposed that every body pulsates, which might be an explanations of gravitation and the electric charges.
However, those models were overthrown because most of them lead to an unacceptable amount of drag, which is not observed. Other models are violating the energy conservation law and are incompatible with modern thermodynamics.[10]
General relativity
Mining Engineer (Excluding Oil ) Truman from Alma, loves to spend time knotting, largest property developers in singapore developers in singapore and stamp collecting. Recently had a family visit to Urnes Stave Church. In general relativity, the effects of gravitation are ascribed to spacetime curvature instead of to 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).
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 and Hilbert discovered the field equations of general relativity, which relate the presence of matter and the curvature of spacetime and are named after Einstein. 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 the geometry of spacetime. The geodesic paths for a spacetime are calculated from the metric tensor.
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 an event horizon surrounding a Cauchy horizon.
- The Kerr solution for rotating massive objects. This solution also produces black holes with multiple 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:
- 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.
Gravity and quantum mechanics
Mining Engineer (Excluding Oil ) Truman from Alma, loves to spend time knotting, largest property developers in singapore developers in singapore and stamp collecting. Recently had a family visit to Urnes Stave Church. Several decades after the discovery of general relativity it was realized that it 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.[11]
It is notable that in general relativity, gravitational radiation, which under the rules of quantum mechanics must be composed of gravitons, is created only 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.
References
43 year old Petroleum Engineer Harry from Deep River, usually spends time with hobbies and interests like renting movies, property developers in singapore new condominium and vehicle racing. Constantly enjoys going to destinations like Camino Real de Tierra Adentro.
Template:Theories of gravitation
- ↑ Edward Grant, The Foundations of Modern Science in the Middle Ages, (Cambridge: Cambridge Univ. Pr., 1996), pp. 60-1.
- ↑ Olaf Pedersen, Early Physics and Astronomy, (Cambridge: Cambridge Univ. Pr., 1993), p. 130
- ↑
20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.
My blog: http://www.primaboinca.com/view_profile.php?userid=5889534 - ↑ Thomas Khoshy, Elementary Number Theory with Applications, Academic Press, 2002, p. 567. ISBN 0-12-421171-2.
- ↑ 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.
My blog: http://www.primaboinca.com/view_profile.php?userid=5889534 - ↑ Template:Cite web
- ↑ 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.
My blog: http://www.primaboinca.com/view_profile.php?userid=5889534 - ↑ 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.
My blog: http://www.primaboinca.com/view_profile.php?userid=5889534 - ↑ One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting
In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang
Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules
Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.
A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running
The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more
There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang - ↑ One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting
In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang
Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules
Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.
A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running
The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more
There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang - ↑ 11.0 11.1 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.
My blog: http://www.primaboinca.com/view_profile.php?userid=5889534 - ↑ 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.
My blog: http://www.primaboinca.com/view_profile.php?userid=5889534 - ↑ 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.
My blog: http://www.primaboinca.com/view_profile.php?userid=5889534