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{{Short description|Theory in modern physics that describes gravity as an entropic force}}
[[Image:NewtonsLawOfUniversalGravitation.svg|thumb|right|200px|The theory of ''entropic gravity'' abides by Newton's law of universal gravitation on Earth and at interplanetary distances but diverges from this classic nature at interstellar distances.]]

'''Entropic gravity''', also known as '''emergent gravity''', is a theory in modern physics that describes [[Physics:Gravity|gravity]] as an ''[[Physics:Entropic force|entropic force]]''—a force with macro-scale homogeneity but which is subject to [[Physics:Quantum fluctuation|quantum-level]] disorder—and not a [[Physics:Fundamental interaction|fundamental interaction]]. The theory, based on [[Physics:String theory|string theory]], [[Astronomy:Black hole|black hole]] physics, and quantum information theory, describes gravity as an ''emergent'' phenomenon that springs from the [[Quantum entanglement|quantum entanglement]] of small bits of [[Physics:Spacetime|spacetime]] information. As such, entropic gravity is said to abide by the [[Physics:Second law of thermodynamics|second law of thermodynamics]] under which the [[Physics:Entropy|entropy]] of a physical system tends to increase over time.

The theory has been controversial within the physics community but has sparked research and experiments to test its validity.

==Significance==
At its simplest, the theory holds that when gravity becomes vanishingly weak—levels seen only at interstellar distances—it diverges from its classically understood nature and its strength begins to decay ''linearly with distance'' from a mass.

Entropic gravity provides an underlying framework to explain Modified Newtonian Dynamics, or MOND, which holds that at a [[Physics:Gravitational acceleration|gravitational acceleration]] threshold of approximately {{val|1.2e-10|u=m/s2}}, gravitational strength begins to vary inversely ''linearly'' with distance from a mass rather than the normal [[Inverse-square law|inverse-square law]] of the distance. This is an exceedingly low threshold, measuring only 12&nbsp;trillionths [[Physics:Standard gravity|gravity's strength at Earth's surface]]; an object dropped from a height of one meter would fall for 36 hours were Earth's gravity this weak. It is also 3,000 times less than the remnant of Earth's gravitational field that exists at the point where {{nowrap|''[[Astronomy:Voyager 1|Voyager 1]]''}} crossed the solar system's heliopause and entered interstellar space.

The theory claims to be consistent with both the macro-level observations of Newtonian gravity as well as Einstein's [[Physics:General relativity|theory of general relativity]] and its gravitational distortion of spacetime. Importantly, the theory also explains (without invoking the existence of dark matter and tweaking of its new [[Free parameter|free parameter]]s) why [[Astronomy:Galaxy rotation curve|galactic rotation curves]] differ from the profile expected with visible matter.

The theory of entropic gravity posits that what has been interpreted as unobserved dark matter is the product of quantum effects that can be regarded as a form of ''positive [[Astronomy:Dark energy|dark energy]]'' that lifts the [[Physics:Vacuum energy|vacuum energy]] of space from its ground state value. A central tenet of the theory is that the positive dark energy leads to a thermal-volume law contribution to entropy that overtakes the area law of [[Anti-de Sitter space|anti-de Sitter space]] precisely at
the [[Astronomy:Hubble volume|cosmological horizon]].

Thus this theory provides an alternative explanation for what mainstream physics currently attributes to [[Astronomy:Dark matter|dark matter]]. Since dark matter is believed to compose the vast majority of the universe's mass, a theory in which it is absent has huge implications for [[Astronomy:Cosmology|cosmology]]. In addition to continuing theoretical work in various directions, there are many experiments planned or in progress to actually detect or better determine the properties of dark matter (beyond its gravitational attraction), all of which would be undermined by an alternative explanation for the gravitational effects currently attributed to this elusive entity.

==Origin==
The thermodynamic description of gravity has a history that goes back at least to research on [[Astronomy:Black hole thermodynamics|black hole thermodynamics]] by [[Biography:Jacob Bekenstein|Bekenstein]] and [[Biography:Stephen Hawking|Hawking]] in the mid-1970s. These studies suggest a deep connection between [[Physics:Gravity|gravity]] and thermodynamics, which describes the behavior of heat. In 1995, Jacobson demonstrated that the [[Physics:Einstein field equations|Einstein field equations]] describing relativistic gravitation can be derived by combining general thermodynamic considerations with the [[Astronomy:Equivalence principle|equivalence principle]].<ref>{{cite journal |last=Jacobson |first=Theodore|title=Thermodynamics of Spacetime: The Einstein Equation of State|doi=10.1103/PhysRevLett.75.1260|date=4 April 1995|pages=1260–1263|issue=7|volume=75|journal=Phys. Rev. Lett.|arxiv=gr-qc/9504004|bibcode=1995PhRvL..75.1260J|pmid=10060248|s2cid=13223728}}</ref> Subsequently, other physicists, most notably Thanu Padmanabhan, began to explore links between gravity and [[Physics:Entropy|entropy]].<ref>{{cite journal|last=Padmanabhan|first=Thanu|title=Thermodynamical Aspects of Gravity: New insights|year=2010|pages=6901|issue=4|volume=73|journal=Rep. Prog. Phys. |arxiv=0911.5004|doi=10.1088/0034-4885/73/4/046901|bibcode=2010RPPh...73d6901P|s2cid=209835245 }}</ref><ref>{{cite arXiv|last=Mok|first=H.M.|title=Further Explanation to the Cosmological Constant Problem by Discrete Space-time Through Modified Holographic Principle|eprint=physics/0408060|date=13 August 2004}}</ref>

==Erik Verlinde's theory==
In 2009, [[Biography:Erik Verlinde|Erik Verlinde]] proposed a conceptual model that describes gravity as an entropic force.<ref>{{cite news|last=van Calmthout|first=Martijn|title=Is Einstein een beetje achterhaald?|url=http://www.volkskrant.nl/wetenschap/article1326775.ece/Is_Einstein_een_beetje_achterhaald|access-date=6 September 2010|newspaper=de Volkskrant|date=12 December 2009|language=nl}}</ref> He argues (similar to Jacobson's result) that gravity is a consequence of the "information associated with the positions of material bodies".<ref>{{cite journal |author=E.P. Verlinde |doi=10.1007/JHEP04(2011)029 |journal=JHEP |title=On the Origin of Gravity and the Laws of Newton |bibcode = 2011JHEP...04..029V |arxiv = 1001.0785 |volume=2011|issue=4 |pages=29 |year=2011 |s2cid=3597565 }}</ref> This model combines the thermodynamic approach to gravity with [[Biography:Gerard 't Hooft|Gerard 't Hooft]]'s [[Physics:Holographic principle|holographic principle]]. It implies that gravity is not a [[Physics:Fundamental interaction|fundamental interaction]], but an emergent phenomenon which arises from the statistical behavior of microscopic [[Chemistry:Degrees of freedom (physics and chemistry)|degrees of freedom]] encoded on a holographic screen.  The paper drew a variety of responses from the scientific community. [[Biography:Andrew Strominger|Andrew Strominger]], a string theorist at Harvard said "Some people have said it can't be right, others that it's right and we already knew it – that it’s right and profound, right and trivial."<ref name="nytimes">{{cite news|last=Overbye|first=Dennis|title=A Scientist Takes on Gravity|url=https://www.nytimes.com/2010/07/13/science/13gravity.html?_r=1|access-date=6 September 2010|newspaper={{wipe|The New York Times}}|date=12 July 2010}}</ref>

In July 2011, Verlinde presented the further development of his ideas in a contribution to the Strings 2011 conference, including an explanation for the origin of dark matter.<ref>[http://www2.physics.uu.se/external/strings2011/presentations/5%20Friday/1220_Verlinde.pdf E. Verlinde, The Hidden Phase Space of our Universe], Strings 2011, Uppsala, 1 July 2011.</ref>

Verlinde's article also attracted a large amount of media exposure,<ref>[https://www.newscientist.com/article/mg20527443.800-the-entropy-force-a-new-direction-for-gravity.html?page=1 The entropy force: a new direction for gravity], New Scientist, 20 January 2010, issue 2744</ref><ref>[https://www.wired.com/beyond_the_beyond/2010/01/gravity-is-an-entropic-form-of-holographic-information/ Gravity is an entropic form of holographic information], ''Wired Magazine'', 20 January 2010</ref> and led to immediate follow-up work in cosmology,<ref>{{cite journal |arxiv=1001.3237 |author1=Fu-Wen Shu |author2=Yungui Gong |title=Equipartition of energy and the first law of thermodynamics at the apparent horizon |year=2011 |doi=10.1142/S0218271811018883 |volume=20 |issue=4 |journal=International Journal of Modern Physics D |pages=553–559|bibcode = 2011IJMPD..20..553S |s2cid=119253807 }}</ref><ref>{{cite journal |author1=Rong-Gen Cai |author2=Li-Ming Cao |author3=Nobuyoshi Ohta |doi=10.1103/PhysRevD.81.061501 |journal=Phys. Rev. D |volume=81 |title=Friedmann Equations from Entropic Force |issue=6 |pages=061501 |year=2010 |arxiv=1001.3470|bibcode = 2010PhRvD..81f1501C |citeseerx=10.1.1.756.6761 |s2cid=118462566 }}</ref> the [[Astronomy:Dark energy|dark energy hypothesis]],<ref>[https://web.archive.org/web/20100119223903/http://www.scientificblogging.com/hammock_physicist/it_bit_how_get_rid_dark_energy It from Bit: How to get rid of dark energy], Johannes Koelman, 2010</ref> [[Physics:Metric expansion of space|cosmological acceleration]],<ref>{{cite journal |author1=Easson |author2=Frampton |author3=Smoot |doi=10.1016/j.physletb.2010.12.025 |journal=Phys. Lett. B |volume=696 |title=Entropic Accelerating Universe |issue=3 |pages=273–277 |year=2011 |arxiv=1002.4278|bibcode = 2011PhLB..696..273E |s2cid=119192004 }}</ref><ref>{{cite journal |author1=Yi-Fu Cai |author2=Jie Liu |author3=Hong Li |doi=10.1016/j.physletb.2010.05.033 |journal=Phys. Lett. B |volume=690 |title=Entropic cosmology: a unified model of inflation and late-time acceleration |issue=3 |pages=213–219 |year=2010 |arxiv=1003.4526|bibcode = 2010PhLB..690..213C |s2cid=118627323 }}</ref> [[Astronomy:Inflation (cosmology)|cosmological inflation]],<ref>{{cite arXiv |eprint=1001.4786 |author1=Yi Wang |title=Towards a Holographic Description of Inflation and Generation of Fluctuations from Thermodynamics |year=2010|class=hep-th }}</ref> and [[Physics:Loop quantum gravity|loop quantum gravity]].<ref>{{cite arXiv |eprint=1001.3668 |author1=Lee Smolin |title=Newtonian gravity in loop quantum gravity |class=gr-qc |year=2010}}</ref> Also, a specific microscopic model has been proposed that indeed leads to entropic gravity emerging at large scales.<ref>{{cite arXiv |eprint=1001.3808 |author1=Jarmo Mäkelä |title=Notes Concerning "On the Origin of Gravity and the Laws of Newton" by E. Verlinde |class=gr-qc |year=2010}}</ref> Entropic gravity can emerge from quantum entanglement of local [[Physics:Rindler coordinates#The Rindler horizon|Rindler horizons]].<ref>{{Cite journal|last1=Lee|first1=Jae-Weon|last2=Kim|first2=Hyeong-Chan|last3=Lee|first3=Jungjai|date=2013|title=Gravity from quantum information|journal=Journal of the Korean Physical Society|language=en|volume=63|issue=5|pages=1094–1098|doi=10.3938/jkps.63.1094|issn=0374-4884|arxiv=1001.5445|bibcode=2013JKPS...63.1094L|s2cid=118494859}}</ref>

==Derivation of the law of gravitation==
The law of gravitation is derived from classical statistical mechanics applied to the [[Physics:Holographic principle|holographic principle]], that states that the description of a volume of space can be thought of as <math>N</math> bits of binary information, encoded on a boundary to that region, a closed surface of area <math>A</math>. The information is evenly distributed on the surface with each bit requiring an area equal to <math>\ell_\text{P}^2</math>, the so-called ''Planck area'', from which <math>N</math> can thus be computed:
<math display="block">N = \frac{A}{\ell_\text{P}^2} </math>
where <math>\ell_\text{P}</math> is the [[Planck length]]. The Planck length is defined as:
<math display="block">\ell_\text{P} = \sqrt\frac{\hbar G}{c^3}</math>
where <math>G</math> is the universal gravitational constant, <math>c</math> is the speed of light, and <math>\hbar</math> is the reduced [[Physics:Planck constant|Planck constant]]. When substituted in the equation for <math>N</math> we find:
<math display="block">N = \frac{A c^3}{\hbar G}</math>

The statistical [[Physics:Equipartition theorem|equipartition theorem]] defines the temperature <math>T</math> of a system with <math>N</math> degrees of freedom in terms of its energy <math>E</math> such that:
<math display="block">E = \frac{1}{2} N k_\text{B} T</math>
where <math>k_\text{B}</math> is the [[Physics:Boltzmann constant|Boltzmann constant]]. This is the [[Mass–energy equivalence|equivalent energy]] for a mass <math>M</math> according to:
<math display="block">E = Mc^2.</math>

The effective temperature experienced due to a uniform acceleration in a [[Physics:Vacuum state|vacuum field]] according to the [[Physics:Unruh effect|Unruh effect]] is:
<math display="block">T = \frac{\hbar a}{2\pi c k_\text{B}},</math>
where <math>a</math> is that acceleration, which for a mass <math>m</math> would be attributed to a force <math>F</math> according to Newton's second law of motion:
<math display="block">F = ma.</math>

Taking the holographic screen to be a sphere of radius <math>r</math>, the surface area would be given by:
<math display="block">A = 4\pi r^2.</math>

From algebraic substitution of these into the above relations, one derives [[Physics:Newton's law of universal gravitation|Newton's law of universal gravitation]]:
<math display="block">F = m \frac{2\pi c k_\text{B} T}{\hbar} = m \frac{4\pi c}{\hbar} \frac{E}{N} = m \frac{4\pi c^3}{\hbar} \frac{M}{N} = m 4\pi \frac{GM}{A} = G \frac{m M}{r^2}.</math>

Note that this derivation assumes that the number of the binary bits of information is equal to the number of the degrees of freedom.
<math display="block">\frac{A}{\ell_\text{P}^2} = N = \frac{2 E}{k_\text{B} T}</math>

==Criticism and experimental tests==
Entropic gravity, as proposed by Verlinde in his original article, reproduces the [[Physics:Einstein field equations|Einstein field equations]] and, in a Newtonian approximation, a <math>\ \tfrac{\ 1\ }{ r }\ </math> potential for gravitational forces. Since its results do not differ from Newtonian gravity except in regions of extremely small gravitational fields, testing the theory with earth-based laboratory experiments does not appear feasible. Spacecraft-based experiments performed at [[Astronomy:Lagrangian point|Lagrangian point]]s within our solar system would be expensive and challenging.

Even so, entropic gravity in its current form has been severely challenged on formal grounds. Matt Visser has shown<ref>{{cite journal |last=Visser |first=Matt |year=2011 |title=Conservative entropic forces |journal=JHEP |volume=1110 |issue=10 |page=140 |arxiv=1108.5240 |doi=10.1007/JHEP10(2011)140 |bibcode=2011JHEP...10..140V |s2cid=119097091}}, to appear in JHEP</ref> that the attempt to model conservative forces in the general Newtonian case (i.e. for arbitrary potentials and an unlimited number of discrete masses) leads to unphysical requirements for the required entropy and involves an unnatural number of temperature baths of differing temperatures. Visser concludes:
{{quote|There is no reasonable doubt concerning the physical reality of entropic forces, and no reasonable doubt that classical (and semi-classical) general relativity is closely related to thermodynamics [52–55]. Based on the work of Jacobson [1–6], Thanu Padmanabhan [7–12], and others, there are also good reasons to suspect a thermodynamic interpretation of the fully relativistic Einstein equations might be possible. Whether the specific proposals of Verlinde [26] are anywhere near as fundamental is yet to be seen – the rather baroque construction needed to accurately reproduce {{mvar|n}}-body Newtonian gravity in a Verlinde-like setting certainly gives one pause.}}

For the derivation of Einstein's equations from an entropic gravity perspective, Tower Wang shows<ref>{{cite arXiv |last=Wang |first=Tower |year=2012 |title=Modified entropic gravity revisited |eprint=1211.5722|class=hep-th }}</ref> that the inclusion of energy-momentum conservation and cosmological homogeneity and isotropy requirements severely restricts a wide class of potential modifications of entropic gravity, some of which have been used to generalize entropic gravity beyond the singular case of an entropic model of Einstein's equations. Wang asserts that:
{{quote| As indicated by our results, the modified entropic gravity models of form (2), if not killed, should live in a very narrow room to assure the energy-momentum conservation and to accommodate a homogeneous isotropic universe.}}

Cosmological observations using available technology can be used to test the theory. On the basis of lensing by the galaxy cluster Abell 1689, Nieuwenhuizen concludes that EG is strongly ruled out unless additional (dark) matter-like eV neutrinos is added.<ref>{{cite journal |first=Theodorus M. |last=Nieuwenhuizen |date=5 October 2016 |title=How Zwicky already ruled out modified gravity theories without dark matter |journal=Fortschritte der Physik |volume=65 |issue=6–8 |page=1600050 |doi=10.1002/prop.201600050 |arxiv=1610.01543 |s2cid=118676940}}</ref> A team from [[Organization:Leiden Observatory|Leiden Observatory]] statistically observing the [[Astronomy:Gravitational lens|lensing effect of gravitational fields]] at large distances from the centers of more than 33,000 galaxies found that those gravitational fields were consistent with Verlinde's theory.<ref>{{cite news |title=Verlinde's new theory of gravity passes first test |date=16 December 2016 |website=phys.org |url=http://phys.org/news/2016-12-verlinde-theory-gravity.html}}</ref><ref>{{cite journal |title=First test of Verlinde's theory of Emergent Gravity using Weak Gravitational Lensing measurements |first1=Margot M. |last1=Brouwer |display-authors=0 |date=11 December 2016 |journal=[[Organization:Monthly Notices of the Royal Astronomical Society|Monthly Notices of the Royal Astronomical Society]] |volume=466 |issue=to appear |doi=10.1093/mnras/stw3192 |arxiv=1612.03034 |pages=2547–2559 |bibcode = 2017MNRAS.466.2547B |s2cid=18916375 }}</ref><ref>{{cite news |title=First test of rival to Einstein's gravity kills off dark matter |date=15 December 2016 |magazine=New Scientist |url=https://www.newscientist.com/article/2116446-first-test-of-rival-to-einsteins-gravity-kills-off-dark-matter/ |access-date=20 February 2017}}</ref> Using conventional gravitational theory, the fields implied by these observations (as well as from measured galaxy rotation curves) could only be ascribed to a particular distribution of [[Astronomy:Dark matter|dark matter]]. In June 2017, a study by [[Organization:Princeton University|Princeton University]] researcher Kris Pardo asserted that Verlinde's theory is inconsistent with the observed rotation velocities of [[Astronomy:Dwarf galaxy|dwarf galaxies]].<ref name=QuantaMagazine2017>{{cite news | title=Researchers check space-time to see if it's made of quantum bits | date=21 June 2017 | website=Quanta Magazine | url=https://www.quantamagazine.org/researchers-check-space-time-to-see-if-its-made-of-quantum-bits-20170621/ | access-date=2017-08-11}}</ref>{{efn|
"Emergent gravity successfully predicts the rotation velocities of the smallest galaxies in the sample. But it predicts velocities far too low for the more massive galaxies, especially the ones full of gas clouds. This discrepancy could pose a serious problem for emergent gravity, since the main success of the theory so far has been predicting the rotation curves of large galaxies."<ref name=QuantaMagazine2017/>
}}<ref name=Pardo-2017-2020>{{cite journal |last=Pardo |first=Kris |orig-date=2 June 2017 (arXiv) |date=4 December 2020 |title=Testing emergent gravity with isolated dwarf galaxies |journal=[[Physics:Journal of Cosmology and Astroparticle Physics|Journal of Cosmology and Astroparticle Physics]] |volume=2020 |number=12 |page=012 |doi=10.1088/1475-7516/2020/12/012 |arxiv=1706.00785 |bibcode=2020JCAP...12..012P <!-- 2017arXiv170600785P --> |s2cid=39251260 |issn=1475-7516}} arXiv accessed 2017-06-22.</ref>  Another theory of entropy based on geometric considerations (Quantitative Geometrical Thermodynamics, QGT<ref name=":0">{{cite journal |last1=Parker |first1=M.C. |last2=Jeynes |first2=C. |date=2019-07-25 |title=Maximum entropy (most likely) double helical and double logarithmic spiral trajectories in space-time |journal=Scientific Reports |volume=9 |issue=1 |page=10779 |lang=en |doi=10.1038/s41598-019-46765-w |issn=2045-2322 |pmc=6658702 |pmid=31346186 |bibcode=2019NatSR...910779P }}</ref>) provides an entropic basis for the holographic principle<ref>{{Cite journal |last1=Parker |first1=M.C. |last2=Jeynes |first2=C. |date=2021-04-21 |title=Entropic uncertainty principle, partition function and holographic principle derived from Liouville's Theorem |journal=Physics Open |volume=7 |page=100068 |doi=10.1016/j.physo.2021.100068 |bibcode=2021PhyO....700068P |s2cid=235090066 |issn=2666-0326 |doi-access=free }}</ref> and also offers another explanation for galaxy rotation curves as being due to the entropic influence<ref name=":0"/> of the central supermassive blackhole found in the centre of a spiral galaxy.

In 2018, Zhi-Wei Wang and [[Biography:Samuel L. Braunstein|Samuel L. Braunstein]] showed that, while spacetime surfaces near black holes (called stretched horizons) do obey an analog of the first law of thermodynamics, ordinary spacetime surfaces — including holographic screens — generally do not, thus undermining the key thermodynamic assumption of the emergent gravity program.<ref>{{cite journal |last1=Wang |first1=Zhi-Wei |last2=Braunstein |first2=Samuel L. |year=2018 |title=Surfaces away from horizons are not thermodynamic |journal=Nature Communications |volume=9 |issue=1 |page=2977 |doi=10.1038/s41467-018-05433-9 |pmid=30061720 |pmc=6065406 |arxiv=2207.04390 |bibcode=2018NatCo...9.2977W }}</ref>

In his 1964 lecture on the Relation of Mathematics and Physics, [[Biography:Richard Feynman|Richard Feynman]] describes a related theory for gravity where the gravitational force is explained due to an entropic force due to unspecified microscopic degrees of freedom.<ref>{{cite AV media |people=[[Biography:Richard Feynman|Richard Feynman]] (lecturer) |publisher=Cornell University |year=1964 |title=The Relation of Mathematics and Physics |series=Feynman gives the Messenger Lectures |volume=#2 |medium=filmed lecture |url=https://www.youtube.com/watch?v=IaSN-3JAVTg&t=467s |via=Youtube}}</ref> However, he immediately points out that the resulting theory cannot be correct as the [[Physics:Fluctuation-dissipation theorem|fluctuation-dissipation theorem]] would also lead to friction which would slow down the motion of the planets which contradicts observations.

===Entropic gravity and quantum coherence===
Another criticism of entropic gravity is that entropic processes should, as critics argue, break quantum coherence. There is no theoretical framework quantitatively describing the strength of such decoherence effects, though. The temperature of the gravitational field in earth gravity well is very small (on the order of 10{{sup|&minus;19}}K).

Experiments with ultra-cold neutrons in the gravitational field of Earth are claimed to show that neutrons lie on discrete levels exactly as predicted by the [[Physics:Schrödinger equation|Schrödinger equation]] considering the gravitation to be a conservative potential field without any decoherent factors. Archil Kobakhidze argues that this result disproves entropic gravity,<ref>{{cite news |last=Kobakhidze |first=Archil |year=2011 |title=Gravity is not an entropic force |eprint=1009.5414 |journal=Physical Review D}}</ref> while Chaichian ''et al''. suggest a potential loophole in the argument in weak gravitational fields such as those affecting Earth-bound experiments.<ref>{{cite journal |title=On gravity as an entropic force |last1=Chaichian |first1=M. |last2=Oksanen |first2=M. |last3=Tureanu |first3=A. |year=2011 |journal=Physics Letters B |volume=702 |issue=5 |pages=419–421 |doi=10.1016/j.physletb.2011.07.019 |bibcode=2011PhLB..702..419C |s2cid=119287340 |arxiv=1104.4650}}</ref>

==See also==
{{div col|colwidth=22em}}
*{{annotated link|Physics:Abraham–Lorentz force}}
*{{annotated link|Astronomy:Black hole electron}}
*{{annotated link|Physics:Entropic force}}
*{{annotated link|Physics:Hawking radiation}}
*{{annotated link|Physics:List of quantum gravity researchers}}
*{{annotated link|Physics:Gravity}}
*{{annotated link|Induced gravity}}
{{div col end}}

==Footnotes==
{{notelist}}

==References==
{{reflist|25em}}

==Further reading==
*[http://www.science20.com/hammock_physicist/it_bit_entropic_gravity_pedestrians It from bit – Entropic gravity for pedestrians], J. Koelman
*[http://www.imsc.res.in/~iagrg/IagrgSite/Activities/IagrgMeetings/25th_Iagrg/VRtalk.pdf Gravity: the inside story], T Padmanabhan
*[https://www.technologyreview.com/2011/08/24/258052/experiments-show-gravity-is-not-an-emergent-phenomenon/ Experiments Show Gravity Is Not an Emergent Phenomenon]

{{Theories of gravitation}}
[[Category:Information theory|Gravity As An Entropic Force]]
[[Category:Thermodynamics|Gravity As An Entropic Force]]
[[Category:Emergence]]

it:Interazione gravitazionale#Derivazione delle leggi della gravitazione dalla meccanica statistica applicata al principio olografico

{{Sourceattribution|Entropic gravity}}