CINXE.COM

<!DOCTYPE html> <html class="client-nojs" lang="en" dir="ltr"> <head> <meta charset="UTF-8"/> <title>Gravity - RationalWiki</title> <script>document.documentElement.className="client-js";RLCONF={"wgBreakFrames":!1,"wgSeparatorTransformTable":["",""],"wgDigitTransformTable":["",""],"wgDefaultDateFormat":"dmy","wgMonthNames":["","January","February","March","April","May","June","July","August","September","October","November","December"],"wgRequestId":"Z7moRzw7KvE1r9dyu7hNFQAAAJc","wgCSPNonce":!1,"wgCanonicalNamespace":"","wgCanonicalSpecialPageName":!1,"wgNamespaceNumber":0,"wgPageName":"Gravity","wgTitle":"Gravity","wgCurRevisionId":2473513,"wgRevisionId":2473513,"wgArticleId":4908,"wgIsArticle":!0,"wgIsRedirect":!1,"wgAction":"view","wgUserName":null,"wgUserGroups":["*"],"wgCategories":["Pages using DynamicPageList parser function","Articles with unsourced statements","Physics","Articles with funspace counterparts","Astronomy","Science"],"wgPageContentLanguage":"en","wgPageContentModel":"wikitext","wgRelevantPageName":"Gravity","wgRelevantArticleId":4908,"wgIsProbablyEditable":!0, "wgRelevantPageIsProbablyEditable":!0,"wgRestrictionEdit":[],"wgRestrictionMove":[],"wgMediaViewerOnClick":!0,"wgMediaViewerEnabledByDefault":!0};RLSTATE={"site.styles":"ready","noscript":"ready","user.styles":"ready","user":"ready","user.options":"loading","ext.cite.styles":"ready","ext.math.styles":"ready","skins.vector.styles.legacy":"ready","mediawiki.toc.styles":"ready"};RLPAGEMODULES=["ext.cite.ux-enhancements","ext.math.scripts","site","mediawiki.page.startup","mediawiki.page.ready","mediawiki.toc","skins.vector.legacy.js","ext.gadget.ReferenceTooltips","mmv.head","mmv.bootstrap.autostart"];</script> <script>(RLQ=window.RLQ||[]).push(function(){mw.loader.implement("user.options@1hzgi",function($,jQuery,require,module){/*@nomin*/mw.user.tokens.set({"patrolToken":"+\\","watchToken":"+\\","csrfToken":"+\\"}); });});</script> <link rel="stylesheet" href="/w/load.php?lang=en&modules=ext.cite.styles%7Cext.math.styles%7Cmediawiki.toc.styles%7Cskins.vector.styles.legacy&only=styles&skin=vector"/> <script async="" src="/w/load.php?lang=en&modules=startup&only=scripts&raw=1&skin=vector"></script> <meta name="ResourceLoaderDynamicStyles" content=""/> <link rel="stylesheet" href="/w/load.php?lang=en&modules=site.styles&only=styles&skin=vector"/> <meta name="generator" content="MediaWiki 1.35.6"/> <meta name="description" content="Gravity is a fundamental force of nature that has been speculated about since at least 800 BCE, albeit inconclusively till Sir Isaac Newton began his scientific career in the late 1600s. Today, Albert Einstein's theory of General Relativity is commonly considered the most accurate description of how objects move under gravity, although there are still unsolved complexities with the integration of relativity with quantum mechanics."/> <link rel="alternate" type="application/x-wiki" title="Edit" href="/w/index.php?title=Gravity&action=edit"/> <link rel="edit" title="Edit" href="/w/index.php?title=Gravity&action=edit"/> <link rel="shortcut icon" href="/favicon.ico"/> <link rel="search" type="application/opensearchdescription+xml" href="/w/opensearch_desc.php" title="RationalWiki (en)"/> <link rel="EditURI" type="application/rsd+xml" href="https://rationalwiki.org/w/api.php?action=rsd"/> <link rel="license" href="/wiki/RationalWiki:Copyrights"/> <link rel="alternate" type="application/atom+xml" title="RationalWiki Atom feed" href="/w/index.php?title=Special:RecentChanges&feed=atom"/> <meta property="og:type" content="article"/> <meta property="og:site_name" content="RationalWiki"/> <meta property="og:title" content="Gravity"/> <meta property="og:description" content="Gravity is a fundamental force of nature that has been speculated about since at least 800 BCE, albeit inconclusively till Sir Isaac Newton began his scientific career in the late 1600s. Today, Albert Einstein's theory of General Relativity is commonly considered the most accurate description of how objects move under gravity, although there are still unsolved complexities with the integration of relativity with quantum mechanics."/> <meta property="og:url" content="https://rationalwiki.org/wiki/Gravity"/>  </head> <body class="mediawiki ltr sitedir-ltr mw-hide-empty-elt ns-0 ns-subject mw-editable page-Gravity rootpage-Gravity skin-vector action-view minerva--history-page-action-enabled skin-vector-legacy"> <div id="mw-page-base" class="noprint"></div> <div id="mw-head-base" class="noprint"></div> <div id="content" class="mw-body" role="main"> <a id="top"></a> <div id="siteNotice" class="mw-body-content"><div id="localNotice" lang="en" dir="ltr"><div id="2025_RationalWiki_.27Oregon_Plan.27_Fundraiser"> <table role="presentation" style="margin: 1em auto 1em auto; width: 100%;"> <tbody><tr> <td style="width: 60%; text-align: left;"><big><center><b><a href="/wiki/RationalWiki:Fundraiser" title="RationalWiki:Fundraiser">2025 RationalWiki 'Oregon Plan' Fundraiser</a></b></center></big> <p><b>There is no RationalWiki without you.</b> We are a small non-profit with no staff—we are hundreds of volunteers who document pseudoscience and crankery around the world every day. We will never allow ads because we must remain independent. We cannot rely on big donors with corresponding big agendas. We are not the largest website around, but <a href="/wiki/RationalWiki:Fundraiser" title="RationalWiki:Fundraiser">we believe we play an important role in defending truth and objectivity</a>. </p> </td> <td style="width: 40%; text-align: center;"><big><b><a href="/wiki/RationalWiki:Fundraiser" title="RationalWiki:Fundraiser">Fighting pseudoscience isn't free</a>.<br />We are 100% user-supported! Help and donate $5, $10, $20 or whatever you can today with <img alt="PayPal Logo.png" src="/w/images/thumb/f/fb/PayPal_Logo.png/61px-PayPal_Logo.png" decoding="async" width="61" height="17" srcset="/w/images/thumb/f/fb/PayPal_Logo.png/92px-PayPal_Logo.png 1.5x, /w/images/thumb/f/fb/PayPal_Logo.png/122px-PayPal_Logo.png 2x" data-file-width="883" data-file-height="244" />!</b></big><a href="https://www.paypal.com/donate/?hosted_button_id=67BJMQC85CUFW" title="Donate via PayPal" rel="nofollow"><img alt="" src="/w/images/thumb/1/10/DonateButton.png/100px-DonateButton.png" decoding="async" width="100" height="32" srcset="/w/images/thumb/1/10/DonateButton.png/150px-DonateButton.png 1.5x, /w/images/thumb/1/10/DonateButton.png/200px-DonateButton.png 2x" data-file-width="759" data-file-height="241" /></a> </td></tr></tbody></table> <div role="progressbar" style="width: 100%; border: 2px solid black; position: relative; padding: 2px; border-radius: 18px;"> <a href="/wiki/RationalWiki:Fundraiser" title="RationalWiki:Fundraiser"><span style="text-shadow: -1px -1px 0 #FFFFFF, 1px -1px 0 #FFFFFF, -1px 1px 0 #FFFFFF, 1px 1px 0 #FFFFFF; color: black; font-size: 125%; position: absolute; left: 0%; margin: 0 0 0 10px"><b>Donations so far: $2973.89</b></span></a><a href="/wiki/RationalWiki:Fundraiser" title="RationalWiki:Fundraiser"><span style="text-shadow: -1px -1px 0 #FFFFFF, 1px -1px 0 #FFFFFF, -1px 1px 0 #FFFFFF, 1px 1px 0 #FFFFFF; color: black; font-size: 125%; position: absolute; right: 0%; margin: 0 10px 0 0"><b>Goal: $10000</b></span></a><div style="height: 28px; border-radius: 14px; background-color: hsl(23.79112,100%,45%); width: 29.7389%;"></div> </div></div></div></div> <div class="mw-indicators mw-body-content"> </div> <h1 id="firstHeading" class="firstHeading" lang="en">Gravity</h1> <div id="bodyContent" class="mw-body-content"> <div id="siteSub" class="noprint">From RationalWiki</div> <div id="contentSub"></div> <div id="contentSub2"></div> <div id="jump-to-nav"></div> <a class="mw-jump-link" href="#mw-head">Jump to navigation</a> <a class="mw-jump-link" href="#searchInput">Jump to search</a> <div id="mw-content-text" lang="en" dir="ltr" class="mw-content-ltr"><div class="mw-parser-output"><table class="infobox" cellpadding="1" cellspacing="0" style="float: right; margin: 0 0 0.5em 0.5em; text-align:left; border: 1px solid #E3A857; width:175px;"> <tbody><tr> <td style="font-size: 95%; text-align:center; color:white; background-color:#E3A857"><b>The facts of the matter</b><br /><a href="/wiki/Physics" title="Physics"><font size="5" color="white"><b>Physics</b></font></a> </td></tr> <tr> <td style="background-color:#f0d2a8;" align="center"><a href="/wiki/Category:Physics" title="Category:Physics"><img alt="Physicon.png" src="/w/images/thumb/6/67/Physicon.png/100px-Physicon.png" decoding="async" width="100" height="100" srcset="/w/images/thumb/6/67/Physicon.png/150px-Physicon.png 1.5x, /w/images/6/67/Physicon.png 2x" data-file-width="180" data-file-height="180" /></a> </td></tr> <tr> <td style="font-size: 95%; color:white; background-color:#E3A857; text-align:center;"><b>May the mass times acceleration be with you</b> </td></tr> <tr> <td style="font-size: 95%; background-color:#f0d2a8;"> <ul><li><a href="/wiki/Electromagnetism" title="Electromagnetism">Electromagnetism</a></li> <li><a href="/wiki/Quantum_mechanics" title="Quantum mechanics">Quantum mechanics</a></li> <li><a href="/wiki/Relativity" title="Relativity">Relativity</a></li> <li><a href="/wiki/Thermodynamics" class="mw-redirect" title="Thermodynamics">Thermodynamics</a></li></ul> </td></tr> <tr> <td style="font-size: 95%; color:white; background-color:#E3A857; text-align:center;"><b>Let's get physical!</b> </td></tr> <tr> <td style="font-size: 95%; background-color:#f0d2a8;"> <ul><li><a href="/wiki/Laws_of_thermodynamics" title="Laws of thermodynamics">Laws of thermodynamics</a></li> <li><a href="/wiki/EPR_paradox" title="EPR paradox">EPR paradox</a></li> <li><a href="/wiki/Electron" title="Electron">Electron</a></li> <li><a href="/wiki/Weight" title="Weight">Weight</a></li> <li><a href="/wiki/Deutsche_Physik" title="Deutsche Physik">Deutsche Physik</a></li></ul> </td></tr> <tr> <td style="font-size: 95%; color:white; background-color:#E3A857; text-align:center;"><b>Atoms trying to understand atoms</b> </td></tr> <tr> <td style="font-size: 95%; background-color:#f0d2a8;"> <ul><li><a href="/wiki/Petr_Beckmann" title="Petr Beckmann">Petr Beckmann</a></li> <li><a href="/wiki/Linus_Pauling" title="Linus Pauling">Linus Pauling</a></li> <li><a href="/wiki/Robert_L._Park" title="Robert L. Park">Robert L. Park</a></li> <li><a href="/wiki/Jason_Lisle" title="Jason Lisle">Jason Lisle</a></li> <li><a href="/wiki/Paul_Dirac" title="Paul Dirac">Paul Dirac</a></li></ul> <div class="vte plainlinks" style="font-size:smaller; text-align:center;"><a href="/wiki/Template:Physics" title="Template:Physics">v</a> - <a href="/wiki/Template_talk:Physics" title="Template talk:Physics">t</a> - <a rel="nofollow" class="external text" href="https://rationalwiki.org/w/index.php?title=Template:Physics&action=edit">e</a></div> </td></tr></tbody></table> <table class="messagebox mb-brainwatermark mb-warning-orange" style=""> <tbody><tr> <td class="mb-image"><a href="/wiki/File:Warning_icon_orange.svg" class="image"><img alt="Warning icon orange.svg" src="/w/images/thumb/4/4f/Warning_icon_orange.svg/50px-Warning_icon_orange.svg.png" decoding="async" width="50" height="50" srcset="/w/images/thumb/4/4f/Warning_icon_orange.svg/75px-Warning_icon_orange.svg.png 1.5x, /w/images/thumb/4/4f/Warning_icon_orange.svg/100px-Warning_icon_orange.svg.png 2x" data-file-width="400" data-file-height="400" /></a> </td> <td class="mb-text"><b>This page contains too many unsourced statements and needs to be improved</b>. <hr /> <p><b>Gravity</b> could use some help. Please research the article's assertions. Whatever is credible should be sourced, and what is not should be removed. </p> </td></tr></tbody></table> <p><b>Gravity</b> is a fundamental force of nature that has been speculated about since at least 800 <a href="/wiki/BCE" class="mw-redirect" title="BCE">BCE</a>, albeit inconclusively till Sir <a href="/wiki/Isaac_Newton" title="Isaac Newton">Isaac Newton</a> began his scientific career in the late 1600s. Today, Albert Einstein's theory of General Relativity is commonly considered the most accurate description of how objects move under gravity, although there are still unsolved complexities with the integration of relativity with quantum mechanics. </p><p>Because Einstein's theory of gravity is quite complicated and hard to understand, various other theories have been proposed, and the production of alternative explanations is still a cottage industry for kooks and cranks.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1">[1]</a></sup> Meanwhile more serious physicists are still trying to iron out some problems with alternative theories.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2">[2]</a></sup> </p> <div id="toc" class="toc" role="navigation" aria-labelledby="mw-toc-heading"><input type="checkbox" role="button" id="toctogglecheckbox" class="toctogglecheckbox" style="display:none" /><div class="toctitle" lang="en" dir="ltr"><h2 id="mw-toc-heading">Contents</h2><span class="toctogglespan"><label class="toctogglelabel" for="toctogglecheckbox"></label></span></div> <ul> <li class="toclevel-1 tocsection-1"><a href="#General_Relativity"><span class="tocnumber">1</span> <span class="toctext">General Relativity</span></a> <ul> <li class="toclevel-2 tocsection-2"><a href="#From_Newton_to_Einstein"><span class="tocnumber">1.1</span> <span class="toctext">From Newton to Einstein</span></a></li> <li class="toclevel-2 tocsection-3"><a href="#Law_of_Universal_Gravitation"><span class="tocnumber">1.2</span> <span class="toctext">Law of Universal Gravitation</span></a></li> <li class="toclevel-2 tocsection-4"><a href="#More_advanced_versions"><span class="tocnumber">1.3</span> <span class="toctext">More advanced versions</span></a></li> <li class="toclevel-2 tocsection-5"><a href="#Effects_of_general_relativity"><span class="tocnumber">1.4</span> <span class="toctext">Effects of general relativity</span></a></li> <li class="toclevel-2 tocsection-6"><a href="#Quantum_gravity"><span class="tocnumber">1.5</span> <span class="toctext">Quantum gravity</span></a></li> </ul> </li> <li class="toclevel-1 tocsection-7"><a href="#Quirks_and_misconceptions"><span class="tocnumber">2</span> <span class="toctext">Quirks and misconceptions</span></a> <ul> <li class="toclevel-2 tocsection-8"><a href="#Gravity_is_weak"><span class="tocnumber">2.1</span> <span class="toctext">Gravity is weak</span></a></li> <li class="toclevel-2 tocsection-9"><a href="#Higgs_boson"><span class="tocnumber">2.2</span> <span class="toctext">Higgs boson</span></a></li> <li class="toclevel-2 tocsection-10"><a href="#Antigravity_of_antimatter.3F"><span class="tocnumber">2.3</span> <span class="toctext">Antigravity of antimatter?</span></a></li> </ul> </li> <li class="toclevel-1 tocsection-11"><a href="#Alternative_theories"><span class="tocnumber">3</span> <span class="toctext">Alternative theories</span></a> <ul> <li class="toclevel-2 tocsection-12"><a href="#Intelligent_falling"><span class="tocnumber">3.1</span> <span class="toctext">Intelligent falling</span></a></li> <li class="toclevel-2 tocsection-13"><a href="#There_really_is_no_such_thing_as_gravity.21"><span class="tocnumber">3.2</span> <span class="toctext">There really is no such thing as gravity!</span></a></li> <li class="toclevel-2 tocsection-14"><a href="#Legitimate_alternative_theories"><span class="tocnumber">3.3</span> <span class="toctext">Legitimate alternative theories</span></a></li> <li class="toclevel-2 tocsection-15"><a href="#Changes_in_earth.27s_gravity"><span class="tocnumber">3.4</span> <span class="toctext">Changes in earth's gravity</span></a></li> </ul> </li> <li class="toclevel-1 tocsection-16"><a href="#Quotations"><span class="tocnumber">4</span> <span class="toctext">Quotations</span></a></li> <li class="toclevel-1 tocsection-17"><a href="#See_also"><span class="tocnumber">5</span> <span class="toctext">See also</span></a></li> <li class="toclevel-1 tocsection-18"><a href="#External_links"><span class="tocnumber">6</span> <span class="toctext">External links</span></a></li> <li class="toclevel-1 tocsection-19"><a href="#References"><span class="tocnumber">7</span> <span class="toctext">References</span></a></li> </ul> </div> <h2><span class="mw-headline" id="General_Relativity">General Relativity</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Gravity&action=edit&section=1" title="Edit section: General Relativity">edit</a><span class="mw-editsection-bracket">]</span></span></h2> <h3><span class="mw-headline" id="From_Newton_to_Einstein">From Newton to Einstein</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Gravity&action=edit&section=2" title="Edit section: From Newton to Einstein">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <p>Since his day, Newton's <i>Law of Gravity</i> has proven sufficiently accurate to enable the prediction of the location of the planet <a href="/wiki/Neptune" title="Neptune">Neptune</a>. In the late 19<sup>th</sup> century, small irregularities in the orbit of the innermost planet, Mercury, could not be explained through Newtonian Gravity Theory, and it began to be questioned. <a href="/wiki/Einstein" class="mw-redirect" title="Einstein">Einstein</a>'s General Theory of <a href="/wiki/Relativity" title="Relativity">Relativity</a> solved the problem. </p><p>Everyone will be familiar with the visual and physical representation of gravitation as described by the General Theory, i.e., a stretched elastic membrane deflected by the weight of objects placed on it. This is a difficult visualisation of the mathematical idea of curvature in <a href="/wiki/Spacetime" title="Spacetime">spacetime</a>, requiring that the four dimensions of spacetime be visualised as a two dimensional elastic sheet which is distorting in some other dimension. Once this mental leap has been performed it is easy to see how varying <a href="/wiki/Mass_(physics)" title="Mass (physics)">masses</a> have varying effects on the curvature of spacetime; the larger the mass, the greater the distortion and the further reaching its effect.<sup id="cite_ref-3" class="reference"><a href="#cite_note-3">[3]</a></sup> This is most often shown by placing a large, dense object (a bowling ball or cannonball) on the membrane and then rolling other balls past it at varying distances. As a thought experiment one can envisage fairly well the effects of the two objects on each other. The trouble with this demonstration is, of course, friction with the membrane. </p> <h3><span class="mw-headline" id="Law_of_Universal_Gravitation">Law of Universal Gravitation</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Gravity&action=edit&section=3" title="Edit section: Law of Universal Gravitation">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <p>The Law of Universal Gravitation, published in 1687 by <a href="/wiki/Isaac_Newton" title="Isaac Newton">Newton</a> in his <i><a href="/wiki/Philosophi%C3%A6_Naturalis_Principia_Mathematica" class="mw-redirect" title="Philosophiæ Naturalis Principia Mathematica">Principia Mathematica</a>,</i> is a <a href="/wiki/Theory" title="Theory">theory</a> which seeks to explain the force of attraction between all bodies of the universe. It is a theory, not fact, and as such the contents of this article are to be approached critically. </p><p>Mathematically, the law applied to two bodies is: </p> <center> <p><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle F=G{\frac {m_{1}m_{2}}{r^{2}}},}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>F</mi> <mo>=</mo> <mi>G</mi> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <msub> <mi>m</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>1</mn> </mrow> </msub> <msub> <mi>m</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msub> </mrow> <msup> <mi>r</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msup> </mfrac> </mrow> <mo>,</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle F=G{\frac {m_{1}m_{2}}{r^{2}}},}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/48f74b3b4d591ba1996c4d481f74ac3ab7e279d7" class="mwe-math-fallback-image-inline" aria-hidden="true" style="vertical-align: -2.171ex; width:14.338ex; height:5.009ex;" alt="{\displaystyle F=G{\frac {m_{1}m_{2}}{r^{2}}},}"/></span> </p> </center> <p>In which: </p> <ul><li><i>F</i> is the magnitude of the force between the bodies.</li> <li><i>G</i> is the gravitational constant. In our <a href="/wiki/Universe" title="Universe">universe</a>, G = 6.67 × 10<sup>-11</sup> <a href="/w/index.php?title=Newton_(unit)&action=edit&redlink=1" class="new" title="Newton (unit) (page does not exist)">N</a> m<sup>2</sup> kg<sup>-2</sup></li> <li><i>m<sub>1</sub></i> and <i>m<sub>2</sub></i> are the masses of the bodies.</li> <li><i>r</i> is the distance between the centres of the bodies, not the radius, don't forget that.</li></ul> <p>In other words, the law states that the gravitational force between two objects is proportional to the mass of each object and inversely proportional to the square of the distance between them. </p> <h3><span class="mw-headline" id="More_advanced_versions">More advanced versions</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Gravity&action=edit&section=4" title="Edit section: More advanced versions">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <p>The law of universal gravitation fails when confronted with situations involving strong gravitational effects. For example, it does not account for small perturbations in <a href="/wiki/Mercury" title="Mercury">Mercury</a>'s orbit around the <a href="/wiki/Sun" title="Sun">Sun</a>, or for gravitational lensing. <a href="/wiki/Relativity" title="Relativity">General Relativity</a>, which interprets the gravitational force as a consequence of warped spacetime, can accurately account for these observations, and has therefore surpassed Newton's theory as the preferred explanation for gravitation. However, the above equation is adequate for almost all practical calculations. </p> <h3><span class="mw-headline" id="Effects_of_general_relativity">Effects of general relativity</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Gravity&action=edit&section=5" title="Edit section: Effects of general relativity">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <p>General relativity predicts many phenomena that are unfamiliar to everyday experience. Many of these effects are extremely small, and require cutting-edge scientific instrumentation to detect. </p><p>General relativity predicts that space is curved around a mass, and allows one to calculate how light, which follows the curvature of space, bends around massive objects. The best-known detection of this effect was Eddington's detection of the apparent change of position of stars near the Sun measured during a solar eclipse. However, even more massive objects such as galaxy clusters have been shown to act as "magnifying glasses" that distort the images of galaxies behind them. </p><p>Gravitational redshift is an effect that has been measured with high precision in the Pound-Rebka experiment and its improvements. Briefly, a variation of Mössbauer gamma-ray spectroscopy is used to detect the change of wavelength of a gamma ray as it falls from a tower or from an airplane. This is considered a precise test of general relativity. Any competing theory should be able to predict the same effect. </p><p>There should be gravitational waves created (analogous to bursts of electromagnetic energy) when massive events, such as the collapse of a star into a <a href="/wiki/Neutron_star" class="mw-redirect" title="Neutron star">neutron star</a> or <a href="/wiki/Black_hole" title="Black hole">black hole</a>, occur. In an attempt to detect or measure these, there are several devices in place and under construction on the surface of the <a href="/wiki/Earth" title="Earth">Earth</a> which rely on the compression or expansion of physical objects at angles to each other. These are normally kilometer-plus long tubes whose lengths are constantly monitored by laser reflection/interference. The anticipated difference in these lengths is of the order of 10<sup>-10</sup> cm or less. Scientists claim to have detected gravitational waves in the background radiation from the <a href="/wiki/Big_Bang" title="Big Bang">Big Bang</a>, indirect evidence previously existed from two <a href="/wiki/Pulsar" class="mw-redirect" title="Pulsar">pulsars</a> spiraling inwards and losing energy.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4">[4]</a></sup> The detection of gravitational waves is considered definitive evidence in favor of the existence of <a href="/wiki/Black_hole" title="Black hole">black holes</a>. However, one may remain skeptical until more detection events are publicized. In fact, physicists are now highly confident they have detected two signals from two black hole binaries. The dawn of gravitational wave astronomy is upon us.<sup id="cite_ref-5" class="reference"><a href="#cite_note-5">[5]</a></sup> </p> <h3><span class="mw-headline" id="Quantum_gravity">Quantum gravity</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Gravity&action=edit&section=6" title="Edit section: Quantum gravity">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <p>In order to discuss gravity and <a href="/wiki/Quantum" class="mw-redirect" title="Quantum">quantum</a> field theory in the same mathematical environment, gravitation is theorised to be communicated by the exchange of virtual particles called <i><a href="https://en.wikipedia.org/wiki/graviton" class="extiw" title="wp:graviton" rel="nofollow"><span style="color:#477979 !important;" title="Wikipedia: graviton">graviton</span>s</a><sup><img alt="" src="https://upload.wikimedia.org/wikipedia/commons/thumb/5/5a/Wikipedia%27s_W.svg/12px-Wikipedia%27s_W.svg.png" decoding="async" width="12" height="12" srcset="https://upload.wikimedia.org/wikipedia/commons/thumb/5/5a/Wikipedia%27s_W.svg/18px-Wikipedia%27s_W.svg.png 1.5x, https://upload.wikimedia.org/wikipedia/commons/thumb/5/5a/Wikipedia%27s_W.svg/24px-Wikipedia%27s_W.svg.png 2x" data-file-width="128" data-file-height="128" /></sup></i> between masses. So far, nobody has been able to formulate a consistent and sound theory of quantum gravity. String theory is currently thought to be the best hope for this, although it is not certain. To date, string theory, as well as its competitors, remain under development. And since none of them have garnered any support from experiments or observation, they strictly speaking should be called hypotheses. This is a legitimate mystery, and mystery attracts cranks: many cranks - that claim to prove Einstein wrong - from claiming to have solved quantum gravity. </p><p>Gravity is one of the basic forces of the <a href="/wiki/Universe" title="Universe">Universe</a>, and the gravitational constant is thought to have remained the same since a vanishingly small time (<a href="/wiki/Planck%27s_constant#Planck_units" title="Planck's constant">the Planck time</a>) following the Big Bang. As with the other forces, any variation, however small, would result in a very different universe. </p><p>The above has been extracted loosely from <a href="https://en.wikipedia.org/wiki/Gravitation" class="extiw" title="wp:Gravitation" rel="nofollow"><span style="color:#477979 !important;" title="Wikipedia: Gravitation">Wikipedia's "Gravitation" article</span></a><sup><img alt="" src="https://upload.wikimedia.org/wikipedia/commons/thumb/5/5a/Wikipedia%27s_W.svg/12px-Wikipedia%27s_W.svg.png" decoding="async" width="12" height="12" srcset="https://upload.wikimedia.org/wikipedia/commons/thumb/5/5a/Wikipedia%27s_W.svg/18px-Wikipedia%27s_W.svg.png 1.5x, https://upload.wikimedia.org/wikipedia/commons/thumb/5/5a/Wikipedia%27s_W.svg/24px-Wikipedia%27s_W.svg.png 2x" data-file-width="128" data-file-height="128" /></sup> which is a good start for a more in-depth view of the subject. </p> <h2><span class="mw-headline" id="Quirks_and_misconceptions">Quirks and misconceptions</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Gravity&action=edit&section=7" title="Edit section: Quirks and misconceptions">edit</a><span class="mw-editsection-bracket">]</span></span></h2> <h3><span class="mw-headline" id="Gravity_is_weak">Gravity is weak</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Gravity&action=edit&section=8" title="Edit section: Gravity is weak">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <p>Of the four fundamental forces, gravity, the strong force, electromagnetism and the weak force, gravity is by far the weakest.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6">[6]</a></sup> It is significant on the large scale because it is it is the only one of the four that is universal—it never completely stops with distance—and affects <i>all</i> normal mass-energy (nothing has a gravitational <i>charge</i> of zero, not even light) and always attractively. (Compare electromagnetism, which may attract or repel, and as a consequence of that can be shielded by materials or masses of charged particles, or not affect a particle at all, e.g. a neutron or photon. The strong force dies-off completely at super-nuclear distances and doesn't affect leptons like electrons.) ("<a href="/wiki/Dark_energy" title="Dark energy">dark energy</a>" <i>might</i> interact repulsively to cause the accelerated expansion of the universe, but this is not a settled matter). </p> <h3><span class="mw-headline" id="Higgs_boson">Higgs boson</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Gravity&action=edit&section=9" title="Edit section: Higgs boson">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <p>Gravity and the <a href="/wiki/Higgs_boson" title="Higgs boson">Higgs boson</a> aren't directly connected.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7">[7]</a></sup> General relativity treats mass and energy as equivalent; therefore, if a particle has an energy, from afar it looks like it has mass. Most of the mass of ordinary objects comes from the field energy of the strong nuclear force that keeps protons and neutrons together. Unfortunately, this explains only 99% of their mass. Protons and neutrons consist of quarks, which retain their (relatively small) mass at all times, even when not affected by electromagnetic or other external fields. Particles that move slower than light have mass, and vice versa, particles that move at the speed of light don't have mass. So, you need an explanation for what is the energy that quarks and other massive particles still retain on their own right. </p><p>It's been experimentally confirmed that the bosons W+, W- and Z0 that transmit the weak nuclear force - the force responsible for radioactive decay - are massive. The Higgs mechanism is an explanation for this: it proposes the existence of a Higgs field, which is present everywhere in space. Unlike the familiar electromagnetic field, its value is not zero in empty space. Therefore, the bosons gain energy simply by standing still in space. From afar, this appears as mass. Fermions - like the quarks that constitute protons and neutrons, and so all ordinary matter - also interact with the Higgs field, although in a more complicated way than the weak bosons. In this way, they gain mass and cause gravitational attraction. So, the connection of gravity and Higgs is indirect. If you could switch off the Higgs field, the particles in the atoms we're made of would immediately disintegrate and fly away at the speed of light.<sup id="cite_ref-8" class="reference"><a href="#cite_note-8">[8]</a></sup> </p><p>If there exists a Higgs field, there must also exist a single wave in this field, a quantum of the Higgs field, a "Higgs boson". The Higgs boson was detected by two experiments at LHC. Unfortunately, the omnipresence of the Higgs field has elicited claims that the Higgs is a "God particle", a term that the physicists involved hate.<sup id="cite_ref-9" class="reference"><a href="#cite_note-9">[9]</a></sup> It's somewhat puzzling that this is something that scientists and creationists finally agree on: it's not a "God particle". The Higgs field is a simple scalar field, not a "god". From something that would be ordinarily a highly technical detail in particle physics research, a surprisingly amount of popular interest has been generated. </p><p><a href="/wiki/Frank_Tipler" title="Frank Tipler">Frank Tipler</a>, who tries to prove the existence of God through physics, has claimed in this <a href="/w/index.php?title=Omega_Point&action=edit&redlink=1" class="new" title="Omega Point (page does not exist)">Omega Point</a> cosmology that the universe could be made to collapse by annihilating the protons and neutrons in the universe, and other such extraordinary claims about Higgs, cosmology and gravity. None of this research has been accepted into a peer-reviewed journal. Physicist Lawrence M. Krauss referred to Tipler's <i>The Physics of Christianity</i> as "a collection of half-truths and exaggerations, I am tempted to describe Tipler's new book as nonsense—but that would be unfair to the concept of nonsense" in a New Scientist article. </p> <h3><span id="Antigravity_of_antimatter?"></span><span class="mw-headline" id="Antigravity_of_antimatter.3F">Antigravity of antimatter?</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Gravity&action=edit&section=10" title="Edit section: Antigravity of antimatter?">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <p>Does matter attract or repel antimatter? (In other words: Does antimatter have negative "gravitational mass"? Does antimatter fall down or fall up in Earth's gravity?) It is difficult to measure. Not enough antimatter has been observable for long enough to do a simple free-fall experiment, but it is getting closer. In 2011 CERN's Antihydrogen Laser Physics Apparatus (ALPHA) trapped 309 antihydrogen atoms for up to 1000 seconds.<sup id="cite_ref-10" class="reference"><a href="#cite_note-10">[10]</a></sup> </p> <h2><span class="mw-headline" id="Alternative_theories">Alternative theories</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Gravity&action=edit&section=11" title="Edit section: Alternative theories">edit</a><span class="mw-editsection-bracket">]</span></span></h2> <h3><span class="mw-headline" id="Intelligent_falling">Intelligent falling</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Gravity&action=edit&section=12" title="Edit section: Intelligent falling">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <p><i>See also <a href="/wiki/Intelligent_falling" title="Intelligent falling">intelligent falling</a>.</i> </p><p>There is no such thing as <b>gravity</b>: the earth sucks!<sup id="cite_ref-11" class="reference"><a href="#cite_note-11">[11]</a></sup> </p><p>Also the Church of the <a href="/wiki/Flying_Spaghetti_Monster" class="mw-redirect" title="Flying Spaghetti Monster">Flying Spaghetti Monster</a> has shown that gravity is only an illusion caused by the FSM in His goodness pushing everything downwards with His noodly appendage. From this it clearly follows that public schools should <a href="/wiki/Teach_the_controversy" title="Teach the controversy">teach the controversy</a> about gravity. </p><p>Some heretics, however, claim that everything is tied down by the hairs of the mane of the <a href="/wiki/Invisible_Pink_Unicorn" title="Invisible Pink Unicorn">Invisible Pink Unicorn</a>. </p> <h3><span id="There_really_is_no_such_thing_as_gravity!"></span><span class="mw-headline" id="There_really_is_no_such_thing_as_gravity.21">There really is no such thing as gravity!</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Gravity&action=edit&section=13" title="Edit section: There really is no such thing as gravity!">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <p>Apparently it's just <a href="/wiki/Emergence" title="Emergence">a phenomenon</a> arising from other stuff. </p> <table style="margin: auto; border-collapse:collapse; border-style:none; background-color:transparent;" class="cquote"> <tbody><tr> <td><div style="padding:4px 50px;position:relative;"><span style="position:absolute;left:10px;top:-6px;z-index:1;font-family:'Times New Roman',serif;font-weight:bold;color:#B2B7F2;font-size:36px">“</span><span style="position:absolute;right:10px;bottom:-20px;z-index:1;font-family:'Times New Roman',serif;font-weight:bold;color:#B2B7F2;font-size:36px">”</span>Starting from first principles and general assumptions Newton's law of gravitation is shown to arise naturally and unavoidably in a theory in which space is emergent through a holographic scenario. Gravity is explained as an entropic force caused by changes in the information associated with the positions of material bodies. A relativistic generalization of the presented arguments directly leads to the Einstein equations. When space is emergent even Newton's law of inertia needs to be explained. The equivalence principle leads us to conclude that it is actually this law of inertia whose origin is entropic.</div> </td></tr> <tr> <td style="padding:4px 10px 8px;font-size:smaller;line-height:1.6em;text-align:right;"><cite style="font-style:normal;position:relative;z-index:2">—<a rel="nofollow" class="external text" href="https://arxiv.org/abs/1001.0785">Erik P. Verlinde 6 Jan '10</a></cite> </td></tr></tbody></table> <p>... and they said <a href="/wiki/Quantum_mechanics" title="Quantum mechanics">quantum mechanics</a> was hard to comprehend! This is an attempt to solve the problem of the weakness of gravity by claiming it is not a true force, but only an apparent force. There are several such theories, but a common thread is the lack of experimental tests. </p> <h3><span class="mw-headline" id="Legitimate_alternative_theories">Legitimate alternative theories</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Gravity&action=edit&section=14" title="Edit section: Legitimate alternative theories">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <p>Einstein's general relativity is considered the best theory of gravity as of today. It is possible to formulate, in principle, infinitely many theories that produce the same results as a given theory. It's the classical "fitting the elephant" problem: John Neumann said, "With four parameters I can fit an elephant, and with five I can make him wiggle his trunk."<sup id="cite_ref-12" class="reference"><a href="#cite_note-12">[12]</a></sup> Therefore, even though a theory might have the exact same predictions as general relativity, that isn't any achievement at all unless: 1) the theory is simpler than relativity, or 2) the theory predicts something which is observed but which relativity predicts wrong. </p><p>Nordström's theory of gravity is highly related; however, it is inconsistent with data, but it remains in use as a "toy model" for exploration of the mathematics. Modified Newtonian dynamics is another, more up-to-date attempt at proving Einstein wrong. Generally, however, these theories suffer from having more free parameters than relativity, or the infeasibility of proving them right vs. relativity. Massive amounts of work have been done to detect a "Lorentz violation", in effect anything that moves faster than the speed of light and so contradicts relativity, with no Lorentz violations detected. </p><p>Of particular interest are apparent anomalies where objects under the influence of gravity do not behave exactly as expected by general relativity. The <a href="https://en.wikipedia.org/wiki/Pioneer_anomaly" class="extiw" title="wp:Pioneer anomaly" rel="nofollow"><span style="color:#477979 !important;" title="Wikipedia: Pioneer anomaly">Pioneer anomaly</span></a><sup><img alt="" src="https://upload.wikimedia.org/wikipedia/commons/thumb/5/5a/Wikipedia%27s_W.svg/12px-Wikipedia%27s_W.svg.png" decoding="async" width="12" height="12" srcset="https://upload.wikimedia.org/wikipedia/commons/thumb/5/5a/Wikipedia%27s_W.svg/18px-Wikipedia%27s_W.svg.png 1.5x, https://upload.wikimedia.org/wikipedia/commons/thumb/5/5a/Wikipedia%27s_W.svg/24px-Wikipedia%27s_W.svg.png 2x" data-file-width="128" data-file-height="128" /></sup> was an apparent disparity in the acceleration of the space probes Pioneer 10 and Pioneer 11 which some people believed was due to an incorrect understanding of gravity, although it has been explained by the complex way spacecraft emit heat.<sup id="cite_ref-13" class="reference"><a href="#cite_note-13">[13]</a></sup> The <a href="https://en.wikipedia.org/wiki/flyby_anomaly" class="extiw" title="wp:flyby anomaly" rel="nofollow"><span style="color:#477979 !important;" title="Wikipedia: flyby anomaly">flyby anomaly</span></a><sup><img alt="" src="https://upload.wikimedia.org/wikipedia/commons/thumb/5/5a/Wikipedia%27s_W.svg/12px-Wikipedia%27s_W.svg.png" decoding="async" width="12" height="12" srcset="https://upload.wikimedia.org/wikipedia/commons/thumb/5/5a/Wikipedia%27s_W.svg/18px-Wikipedia%27s_W.svg.png 1.5x, https://upload.wikimedia.org/wikipedia/commons/thumb/5/5a/Wikipedia%27s_W.svg/24px-Wikipedia%27s_W.svg.png 2x" data-file-width="128" data-file-height="128" /></sup> is a still-unexplained anomaly in the behavior of spacecraft during planetary flybys. Another important discrepancy is in measured galaxy rotation speeds, which led to the hypothesis of <a href="/wiki/Dark_matter" title="Dark matter">dark matter</a> (and other explanations).<sup id="cite_ref-14" class="reference"><a href="#cite_note-14">[14]</a></sup> </p> <h3><span id="Changes_in_earth's_gravity"></span><span class="mw-headline" id="Changes_in_earth.27s_gravity">Changes in earth's gravity</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Gravity&action=edit&section=15" title="Edit section: Changes in earth's gravity">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <p>There are various fringe theories involving changes in the earth's gravity, often correlated with a change in the earth's size (if the earth expanded without gaining mass, gravity on its surface would be reduced). To some people, lower gravity in the past would explain why <a href="/wiki/Dinosaur" title="Dinosaur">dinosaurs</a> were so big.<sup id="cite_ref-15" class="reference"><a href="#cite_note-15">[15]</a></sup> Changes in the earth's size such as an <a href="/wiki/Expanding_Earth" title="Expanding Earth">Expanding Earth</a> or contraction from <a href="https://en.wikipedia.org/wiki/Geophysical_global_cooling" class="extiw" title="wp:Geophysical global cooling" rel="nofollow"><span style="color:#477979 !important;" title="Wikipedia: Geophysical global cooling">Geophysical global cooling</span></a><sup><img alt="" src="https://upload.wikimedia.org/wikipedia/commons/thumb/5/5a/Wikipedia%27s_W.svg/12px-Wikipedia%27s_W.svg.png" decoding="async" width="12" height="12" srcset="https://upload.wikimedia.org/wikipedia/commons/thumb/5/5a/Wikipedia%27s_W.svg/18px-Wikipedia%27s_W.svg.png 1.5x, https://upload.wikimedia.org/wikipedia/commons/thumb/5/5a/Wikipedia%27s_W.svg/24px-Wikipedia%27s_W.svg.png 2x" data-file-width="128" data-file-height="128" /></sup> have also been used to explain plate tectonics.<sup id="cite_ref-16" class="reference"><a href="#cite_note-16">[16]</a></sup> </p><p>This is distinct from the issue of whether the gravitational constant <i>G</i> is changing; a disparity in measurements of <i>G</i> has caused some to speculate that it may not actually be a constant.<sup id="cite_ref-17" class="reference"><a href="#cite_note-17">[17]</a></sup> </p> <h2><span class="mw-headline" id="Quotations">Quotations</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Gravity&action=edit&section=16" title="Edit section: Quotations">edit</a><span class="mw-editsection-bracket">]</span></span></h2> <table style="margin: auto; border-collapse:collapse; border-style:none; background-color:transparent;" class="cquote"> <tbody><tr> <td><div style="padding:4px 50px;position:relative;"><span style="position:absolute;left:10px;top:-6px;z-index:1;font-family:'Times New Roman',serif;font-weight:bold;color:#B2B7F2;font-size:36px">“</span><span style="position:absolute;right:10px;bottom:-20px;z-index:1;font-family:'Times New Roman',serif;font-weight:bold;color:#B2B7F2;font-size:36px">”</span>Gravity is not a version of the truth. It is the truth. Anyone who doubts it is invited to jump out a tenth-story window.</div> </td></tr> <tr> <td style="padding:4px 10px 8px;font-size:smaller;line-height:1.6em;text-align:right;"><cite style="font-style:normal;position:relative;z-index:2">—<a href="/wiki/Richard_Dawkins" title="Richard Dawkins">Richard Dawkins</a></cite> </td></tr></tbody></table> <table style="margin: auto; border-collapse:collapse; border-style:none; background-color:transparent;" class="cquote"> <tbody><tr> <td><div style="padding:4px 50px;position:relative;"><span style="position:absolute;left:10px;top:-6px;z-index:1;font-family:'Times New Roman',serif;font-weight:bold;color:#B2B7F2;font-size:36px">“</span><span style="position:absolute;right:10px;bottom:-20px;z-index:1;font-family:'Times New Roman',serif;font-weight:bold;color:#B2B7F2;font-size:36px">”</span><a href="/wiki/Christians" class="mw-redirect" title="Christians">Christians</a> don't believe in gravity!</div> </td></tr> <tr> <td style="padding:4px 10px 8px;font-size:smaller;line-height:1.6em;text-align:right;"><cite style="font-style:normal;position:relative;z-index:2">—Peter Griffin, <i>Family Guy</i>, after <a href="/wiki/Mel_Gibson" title="Mel Gibson">Mel Gibson</a> fell off Mount Rushmore</cite> </td></tr></tbody></table> <div style="clear: right; float:right; border:solid #ff8500 1px; margin: 1px 0; width:250px; padding:2px; background:#ffff80;"> <table cellspacing="0"> <tbody><tr> <td style="width:45px;height:45px;text-align:center"><span class="plainlinks"><a href="/wiki/File:Icon_fun.svg" class="image"><img alt="Icon fun.svg" src="/w/images/thumb/5/5c/Icon_fun.svg/50px-Icon_fun.svg.png" decoding="async" width="50" height="50" srcset="/w/images/thumb/5/5c/Icon_fun.svg/75px-Icon_fun.svg.png 1.5x, /w/images/thumb/5/5c/Icon_fun.svg/100px-Icon_fun.svg.png 2x" data-file-width="200" data-file-height="200" /></a></span> </td> <td style="font-size:9pt;padding:4pt;line-height:1.25em;color:red;">For those of you in the mood, <a href="/wiki/RationalWiki" title="RationalWiki">RationalWiki</a> has a <i>fun</i> article about <i><a href="/wiki/Fun:Gravitationalism" title="Fun:Gravitationalism">Gravitationalism</a></i>. </td></tr></tbody></table></div> <h2><span class="mw-headline" id="See_also">See also</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Gravity&action=edit&section=17" title="Edit section: See also">edit</a><span class="mw-editsection-bracket">]</span></span></h2> <ul><li><a href="/wiki/Electromagnetism" title="Electromagnetism">Electromagnetism</a></li> <li><a href="/wiki/Intelligent_falling" title="Intelligent falling">Intelligent falling</a></li></ul> <h2><span class="mw-headline" id="External_links">External links</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Gravity&action=edit&section=18" title="Edit section: External links">edit</a><span class="mw-editsection-bracket">]</span></span></h2> <ul><li><a rel="nofollow" class="external text" href="https://www.youtube.com/watch?v=2EkHB_WtKRQ">What you don't learn about mass (in grade school)</a>.</li></ul> <h2><span class="mw-headline" id="References">References</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Gravity&action=edit&section=19" title="Edit section: References">edit</a><span class="mw-editsection-bracket">]</span></span></h2> <div class="references-small" style="font-size:90%;"> <div class="mw-references-wrap mw-references-columns"><ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><a href="#cite_ref-1">↑</a></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://theconversation.com/why-is-einsteins-general-relativity-such-a-popular-target-for-cranks-49661">Why is Einstein's general relativity such a popular target for cranks?</a>, The Conversation, Nov 23, 2015</span> </li> <li id="cite_note-2"><span class="mw-cite-backlink"><a href="#cite_ref-2">↑</a></span> <span class="reference-text">See the <a href="/wiki/Wikipedia" title="Wikipedia">Wikipedia</a> article on <a href="https://en.wikipedia.org/wiki/Alternatives_to_general_relativity" class="extiw" title="wp:Alternatives to general relativity" rel="nofollow">Alternatives to general relativity</a>.</span> </li> <li id="cite_note-3"><span class="mw-cite-backlink"><a href="#cite_ref-3">↑</a></span> <span class="reference-text">Although technically gravity reaches from every object in the universe to every other, its effects due to very distant ones become much less noticeable.</span> </li> <li id="cite_note-4"><span class="mw-cite-backlink"><a href="#cite_ref-4">↑</a></span> <span class="reference-text"><a rel="nofollow" class="external text" href="https://www.newscientist.com/article/dn25243-einsteins-ripples-your-guide-to-gravitational-waves/">Einstein's ripples: Your guide to gravitational waves</a></span> </li> <li id="cite_note-5"><span class="mw-cite-backlink"><a href="#cite_ref-5">↑</a></span> <span class="reference-text">PBS Space Time: The Future of Gravitational Waves (<a rel="nofollow" class="external text" href="https://www.youtube.com/watch?v=eJ2RNBAFLj0">YouTube link</a>)</span> </li> <li id="cite_note-6"><span class="mw-cite-backlink"><a href="#cite_ref-6">↑</a></span> <span class="reference-text">As a demonstration of relative strength, a small magnet, representing the electromagnetic force, can hold an object up against the gravitational attraction of the whole Earth.</span> </li> <li id="cite_note-7"><span class="mw-cite-backlink"><a href="#cite_ref-7">↑</a></span> <span class="reference-text"><a rel="nofollow" class="external free" href="https://profmattstrassler.com/2012/10/15/why-the-higgs-and-gravity-are-unrelated/">https://profmattstrassler.com/2012/10/15/why-the-higgs-and-gravity-are-unrelated/</a></span> </li> <li id="cite_note-8"><span class="mw-cite-backlink"><a href="#cite_ref-8">↑</a></span> <span class="reference-text"><a rel="nofollow" class="external free" href="https://profmattstrassler.com/articles-and-posts/particle-physics-basics/the-known-apparently-elementary-particles/the-known-particles-if-the-higgs-field-were-zero/">https://profmattstrassler.com/articles-and-posts/particle-physics-basics/the-known-apparently-elementary-particles/the-known-particles-if-the-higgs-field-were-zero/</a></span> </li> <li id="cite_note-9"><span class="mw-cite-backlink"><a href="#cite_ref-9">↑</a></span> <span class="reference-text"><a rel="nofollow" class="external free" href="https://profmattstrassler.com/2013/03/20/why-the-higgs-matters-in-a-few-sentences/">https://profmattstrassler.com/2013/03/20/why-the-higgs-matters-in-a-few-sentences/</a></span> </li> <li id="cite_note-10"><span class="mw-cite-backlink"><a href="#cite_ref-10">↑</a></span> <span class="reference-text">Antihydrogen Trapped For 1000 Seconds - MIT Technology Review <a rel="nofollow" class="external free" href="https://www.technologyreview.com/s/423901/antihydrogen-trapped-for-1000-seconds/">https://www.technologyreview.com/s/423901/antihydrogen-trapped-for-1000-seconds/</a></span> </li> <li id="cite_note-11"><span class="mw-cite-backlink"><a href="#cite_ref-11">↑</a></span> <span class="reference-text">And planes take off because they use special tarmac that stops the earth sucking.</span> </li> <li id="cite_note-12"><span class="mw-cite-backlink"><a href="#cite_ref-12">↑</a></span> <span class="reference-text"><a rel="nofollow" class="external free" href="https://www.johndcook.com/blog/2011/06/21/how-to-fit-an-elephant/">https://www.johndcook.com/blog/2011/06/21/how-to-fit-an-elephant/</a></span> </li> <li id="cite_note-13"><span class="mw-cite-backlink"><a href="#cite_ref-13">↑</a></span> <span class="reference-text"><a rel="nofollow" class="external text" href="https://www.space.com/16648-pioneer-anomaly-spacecraft-mystery-solved.html">Decades-Old 'Pioneer Anomaly' Mystery Finally Solved</a>, space.com, July 18, 2012</span> </li> <li id="cite_note-14"><span class="mw-cite-backlink"><a href="#cite_ref-14">↑</a></span> <span class="reference-text">See the <a href="/wiki/Wikipedia" title="Wikipedia">Wikipedia</a> article on <a href="https://en.wikipedia.org/wiki/Galaxy_rotation_curve" class="extiw" title="wp:Galaxy rotation curve" rel="nofollow">Galaxy rotation curve</a>.</span> </li> <li id="cite_note-15"><span class="mw-cite-backlink"><a href="#cite_ref-15">↑</a></span> <span class="reference-text"><a rel="nofollow" class="external text" href="https://www.dinox.org/index.html">Dinosaur's Gravity</a>, dinox.org</span> </li> <li id="cite_note-16"><span class="mw-cite-backlink"><a href="#cite_ref-16">↑</a></span> <span class="reference-text">See the <a href="/wiki/Wikipedia" title="Wikipedia">Wikipedia</a> article on <a href="https://en.wikipedia.org/wiki/Expanding_Earth" class="extiw" title="wp:Expanding Earth" rel="nofollow">Expanding Earth</a>.</span> </li> <li id="cite_note-17"><span class="mw-cite-backlink"><a href="#cite_ref-17">↑</a></span> <span class="reference-text"><a rel="nofollow" class="external text" href="https://www.newscientist.com/article/dn24180-strength-of-gravity-shifts-and-this-time-its-serious/">Strength of gravity shifts – and this time it’s serious</a>, New Scientist, 11 Sep 2013</span> </li> </ol></div></div>    </div></div><div class="printfooter">Retrieved from "<a dir="ltr" href="https://rationalwiki.org/w/index.php?title=Gravity&oldid=2473513">https://rationalwiki.org/w/index.php?title=Gravity&oldid=2473513</a>"</div> <div id="catlinks" class="catlinks" data-mw="interface"><div id="mw-normal-catlinks" class="mw-normal-catlinks"><a href="/wiki/Special:Categories" title="Special:Categories">Categories</a>: <ul><li><a href="/wiki/Category:Physics" title="Category:Physics">Physics</a></li><li><a href="/wiki/Category:Articles_with_funspace_counterparts" title="Category:Articles with funspace counterparts">Articles with funspace counterparts</a></li><li><a href="/wiki/Category:Astronomy" title="Category:Astronomy">Astronomy</a></li><li><a href="/wiki/Category:Science" title="Category:Science">Science</a></li></ul></div><div id="mw-hidden-catlinks" class="mw-hidden-catlinks mw-hidden-cats-hidden">Hidden categories: <ul><li><a href="/wiki/Category:Pages_using_DynamicPageList_parser_function" title="Category:Pages using DynamicPageList parser function">Pages using DynamicPageList parser function</a></li><li><a href="/wiki/Category:Articles_with_unsourced_statements" title="Category:Articles with unsourced statements">Articles with unsourced statements</a></li></ul></div></div> </div> </div> <div id="mw-navigation"> <h2>Navigation menu</h2> <div id="mw-head">  <nav id="p-personal" class="vector-menu" aria-labelledby="p-personal-label" role="navigation" > <h3 id="p-personal-label"> <span>Personal tools</span> </h3>  <div class="body vector-menu-content">  <ul class="vector-menu-content-list"><li id="pt-anonuserpage">Not logged in</li><li id="pt-anontalk"><a href="/wiki/Special:MyTalk" title="Discussion about edits from this IP address [n]" accesskey="n">Talk</a></li><li id="pt-anoncontribs"><a href="/wiki/Special:MyContributions" title="A list of edits made from this IP address [y]" accesskey="y">Contributions</a></li><li id="pt-createaccount"><a href="/w/index.php?title=Special:CreateAccount&returnto=Gravity" title="You are encouraged to create an account and log in; however, it is not mandatory">Create account</a></li><li id="pt-login"><a href="/w/index.php?title=Special:UserLogin&returnto=Gravity" title="You are encouraged to log in; however, it is not mandatory [o]" accesskey="o">Log in</a></li></ul> </div> </nav> <div id="left-navigation">  <nav id="p-namespaces" class="vector-menu vector-menu-tabs vectorTabs" aria-labelledby="p-namespaces-label" role="navigation" > <h3 id="p-namespaces-label"> <span>Namespaces</span> </h3>  <div class="body vector-menu-content">  <ul class="vector-menu-content-list"><li id="ca-nstab-main" class="selected"><a href="/wiki/Gravity" title="View the content page [c]" accesskey="c">Page</a></li><li id="ca-talk"><a href="/wiki/Talk:Gravity" rel="discussion" title="Discussion about the content page [t]" accesskey="t">Talk</a></li></ul> </div> </nav>  <nav id="p-variants" class="vector-menu-empty emptyPortlet vector-menu vector-menu-dropdown vectorMenu" aria-labelledby="p-variants-label" role="navigation" > <input type="checkbox" class="vector-menu-checkbox vectorMenuCheckbox" aria-labelledby="p-variants-label" /> <h3 id="p-variants-label"> <span>Variants</span> </h3>  <div class="body vector-menu-content">  <ul class="menu vector-menu-content-list"></ul> </div> </nav> </div> <div id="right-navigation">  <nav id="p-views" class="vector-menu vector-menu-tabs vectorTabs" aria-labelledby="p-views-label" role="navigation" > <h3 id="p-views-label"> <span>Views</span> </h3>  <div class="body vector-menu-content">  <ul class="vector-menu-content-list"><li id="ca-view" class="collapsible selected"><a href="/wiki/Gravity">Read</a></li><li id="ca-edit" class="collapsible"><a href="/w/index.php?title=Gravity&action=edit" title="Edit this page [e]" accesskey="e">Edit</a></li><li id="ca-history" class="collapsible"><a href="/w/index.php?title=Gravity&action=history" title="Past revisions of this page [h]" accesskey="h">Fossil record</a></li></ul> </div> </nav>  <nav id="p-cactions" class="vector-menu-empty emptyPortlet vector-menu vector-menu-dropdown vectorMenu" aria-labelledby="p-cactions-label" role="navigation" > <input type="checkbox" class="vector-menu-checkbox vectorMenuCheckbox" aria-labelledby="p-cactions-label" /> <h3 id="p-cactions-label"> <span>More</span> </h3>  <div class="body vector-menu-content">  <ul class="menu vector-menu-content-list"></ul> </div> </nav> <div id="p-search" role="search"> <h3 > <label for="searchInput">Search</label> </h3> <form action="/w/index.php" id="searchform"> <div id="simpleSearch"> <input type="search" name="search" placeholder="Search RationalWiki" title="Search RationalWiki [f]" accesskey="f" id="searchInput"/> <input type="hidden" name="title" value="Special:Search"> <input type="submit" name="fulltext" value="Search" title="Search the pages for this text" id="mw-searchButton" class="searchButton mw-fallbackSearchButton"/> <input type="submit" name="go" value="Go" title="Go to a page with this exact name if it exists" id="searchButton" class="searchButton"/> </div> </form> </div> </div> </div> <div id="mw-panel"> <div id="p-logo" role="banner"> <a title="Visit the main page" class="mw-wiki-logo" href="/wiki/Main_Page"></a> </div>  <nav id="p-navigation" class="vector-menu vector-menu-portal portal portal-first" aria-labelledby="p-navigation-label" role="navigation" > <h3 id="p-navigation-label"> <span>Navigation</span> </h3>  <div class="body vector-menu-content">  <ul class="vector-menu-content-list"><li id="n-mainpage-description"><a href="/wiki/Main_Page" title="Visit the main page [z]" accesskey="z">Main page</a></li><li id="n-recentchanges"><a href="/wiki/Special:RecentChanges" title="A list of recent changes in the wiki [r]" accesskey="r">Recent changes</a></li><li id="n-randompage"><a href="/wiki/Special:Random" title="Load a random mainspace article [x]" accesskey="x">Random page</a></li><li id="n-New-pages"><a href="/wiki/Special:NewPages">New pages</a></li><li id="n-All-logs"><a href="/wiki/Special:Log">All logs</a></li><li id="n-help"><a href="/wiki/Help:Contents" title="RTFM">Help</a></li></ul> </div> </nav>  <nav id="p-support" class="vector-menu vector-menu-portal portal" aria-labelledby="p-support-label" role="navigation" > <h3 id="p-support-label"> <span>Support</span> </h3>  <div class="body vector-menu-content">  <ul class="vector-menu-content-list"><li id="n-Donate"><a href="/wiki/RationalWiki:Site_support">Donate</a></li></ul> </div> </nav>  <nav id="p-community" class="vector-menu vector-menu-portal portal" aria-labelledby="p-community-label" role="navigation" > <h3 id="p-community-label"> <span>Community</span> </h3>  <div class="body vector-menu-content">  <ul class="vector-menu-content-list"><li id="n-Saloon-bar"><a href="/wiki/RationalWiki:Saloon_bar">Saloon bar</a></li><li id="n-To-do-list"><a href="/wiki/RationalWiki:To_do_list">To do list</a></li><li id="n-What-is-going-on.3F"><a href="/wiki/WIGO">What is going on?</a></li><li id="n-Best-of-RationalWiki"><a href="/wiki/RationalWiki:Contents">Best of RationalWiki</a></li><li id="n-About-RationalWiki"><a href="/wiki/RationalWiki">About RationalWiki</a></li><li id="n-Technical-support"><a href="/wiki/RationalWiki:Technical_support">Technical support</a></li><li id="n-Mod-noticeboard"><a href="/wiki/RationalWiki_talk:All_things_in_moderation">Mod noticeboard</a></li><li id="n-RMF-noticeboard"><a href="/wiki/RationalWiki_talk:RationalMedia_Foundation">RMF noticeboard</a></li></ul> </div> </nav>  <nav id="p-Social media" class="vector-menu vector-menu-portal portal" aria-labelledby="p-Social media-label" role="navigation" > <h3 id="p-Social media-label"> <span>Social media</span> </h3>  <div class="body vector-menu-content">  <ul class="vector-menu-content-list"><li id="n-Twitter"><a href="https://twitter.com/RationalWiki" rel="nofollow">Twitter</a></li><li id="n-Mastodon"><a href="https://mstdn.social/@rationalwiki" rel="nofollow">Mastodon</a></li><li id="n-Facebook"><a href="https://www.facebook.com/pages/Rationalwiki/226614404019306" rel="nofollow">Facebook</a></li><li id="n-Discord"><a href="/wiki/RationalWiki:Discord">Discord</a></li><li id="n-Reddit"><a href="/wiki/RationalWiki:Reddit">Reddit</a></li></ul> </div> </nav>  <nav id="p-tb" class="vector-menu vector-menu-portal portal" aria-labelledby="p-tb-label" role="navigation" > <h3 id="p-tb-label"> <span>Tools</span> </h3>  <div class="body vector-menu-content">  <ul class="vector-menu-content-list"><li id="t-whatlinkshere"><a href="/wiki/Special:WhatLinksHere/Gravity" title="A list of all wiki pages that link here [j]" accesskey="j">What links here</a></li><li id="t-recentchangeslinked"><a href="/wiki/Special:RecentChangesLinked/Gravity" rel="nofollow" title="Recent changes in pages linked from this page [k]" accesskey="k">Related changes</a></li><li id="t-specialpages"><a href="/wiki/Special:SpecialPages" title="A list of all special pages [q]" accesskey="q">Special pages</a></li><li id="t-print"><a href="javascript:print();" rel="alternate" title="Printable version of this page [p]" accesskey="p">Printable version</a></li><li id="t-permalink"><a href="/w/index.php?title=Gravity&oldid=2473513" title="Permanent link to this revision of the page">Permanent link</a></li><li id="t-info"><a href="/w/index.php?title=Gravity&action=info" title="More information about this page">Page information</a></li></ul> </div> </nav> </div> </div> <footer id="footer" class="mw-footer" role="contentinfo" > <ul id="footer-info" > <li id="footer-info-lastmod"> This page was last edited on 27 July 2022, at 19:57.</li> <li id="footer-info-copyright">Unless explicitly noted otherwise, all content licensed as indicated by <a name="Copyright" href="//rationalwiki.org/wiki/RationalWiki:Copyrights">RationalWiki:Copyrights</a>. <br> For concerns on copyright infringement please see: <a name="Copyright infringement" href="//rationalwiki.org/wiki/RationalWiki:Copyright_violations">RationalWiki:Copyright violations</a></li> </ul> <ul id="footer-places" > <li id="footer-places-privacy"><a href="/wiki/RationalWiki:Privacy_policy" title="RationalWiki:Privacy policy">Privacy policy</a></li> <li id="footer-places-about"><a href="/wiki/RationalWiki:About" class="mw-redirect" title="RationalWiki:About">About RationalWiki</a></li> <li id="footer-places-disclaimer"><a href="/wiki/RationalWiki:General_disclaimer" title="RationalWiki:General disclaimer">Disclaimers</a></li> </ul> <ul id="footer-icons" class="noprint"> <li id="footer-copyrightico"><a href="https://creativecommons.org/licenses/by-sa/3.0/"><img src="/w/88x31.png" alt="CC-BY-SA 3.0, or any later version" width="88" height="31" loading="lazy"/></a></li> <li id="footer-poweredbyico"><a href="https://www.mediawiki.org/"><img src="/w/resources/assets/poweredby_mediawiki_88x31.png" alt="Powered by MediaWiki" srcset="/w/resources/assets/poweredby_mediawiki_132x47.png 1.5x, /w/resources/assets/poweredby_mediawiki_176x62.png 2x" width="88" height="31" loading="lazy"/></a></li> </ul> <div style="clear: both;"></div> </footer> <script>(RLQ=window.RLQ||[]).push(function(){mw.config.set({"wgPageParseReport":{"limitreport":{"cputime":"0.118","walltime":"0.201","ppvisitednodes":{"value":918,"limit":1000000},"postexpandincludesize":{"value":12518,"limit":2097152},"templateargumentsize":{"value":3365,"limit":2097152},"expansiondepth":{"value":10,"limit":40},"expensivefunctioncount":{"value":0,"limit":100},"unstrip-depth":{"value":0,"limit":20},"unstrip-size":{"value":6829,"limit":5000000},"timingprofile":["100.00% 73.044 1 -total"," 52.56% 38.394 1 Template:Physics"," 47.94% 35.021 1 Template:Navsidebar"," 39.88% 29.128 2 Template:Navsidebar2"," 36.21% 26.450 2 Template:Randomarticles"," 15.40% 11.251 1 Template:Reflist"," 5.69% 4.157 1 Template:Fun"," 5.47% 3.999 1 Template:Sources_needed"," 5.08% 3.709 3 Template:Cquote"," 4.68% 3.422 5 Template:Wpl"]},"cachereport":{"origin":"apache5","timestamp":"20250222103447","ttl":86400,"transientcontent":false}}});mw.config.set({"wgBackendResponseTime":324,"wgHostname":"apache5"});});</script></body></html>