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class="tumblr-white sprite"></div> </div> </div> </div> </div> </a><a href="#" data-component="shareButtonsVertical" data-source="Social_Share_Vertical" data-type="shareGoogleplus" data-ordinal="1" data-network="googleplus" title="Share to Google+" data-ordinal="4" class="s-btn bg-googleplus" data-pin-do="skipLink"> <div class="long wrapper"> <div class="item v-middle"> <div> <div> <div class="googleplus-white sprite"></div> </div> </div> </div> <div class="text item v-middle"> <div> <div> Share </div> </div> </div> </div> <div class="short wrapper"> <div class="item v-middle"> <div> <div> <div class="googleplus-white sprite"></div> </div> </div> </div> </div> </a> </div> </div> </div> </div> <div class="col-push-2 col-push-tablet-1 content-responsive"> <p class="heading by-line-top hide-desktop">By Andrew Zimmerman Jones</p> <p><b>History of the Laws:</b></p><p>Johannes Kepler was a German astronomer and mathematician of the late sixteenth and early seventeenth centuries. His work was largely based on the work of his mentor, Tycho Brahe. Kepler was able to use Bahe's precise measurements (made before telescopes) to determine, mostly by trial and error, three laws that described the motion of the five planets then known.</p><p><b>First Law: Kepler's Elliptical Orbit Law:</b></p><p>Each planet moves in an elliptical orbit, with the sun at one focus of the ellipse.</p><p><b>Second Law: Kepler's Equal-Area Law:</b></p><p>A line from the sun to each planet sweeps out equal areas in equal time.</p><p>The picture to the right depicts this law.</p><p><b>Third Law: Kepler's Law of Periods:</b></p><p>The periods of the planets (<i>T</i>) are proportional to the 3/2 powers of the major axis lengths of their orbits (<i>L</i>).</p><p>Expressed mathematically, then, this says that:</p><blockquote class="yes"><i>T is proportional to L</i><sup>3/2</sup><br/>or<br/><i>T</i><sup>2</sup><i>is proportional to L</i><sup>3</sup></blockquote><p><b>Proving Kepler's Laws:</b></p><p>Though they fit with observation and certainly seemed to work, he had no theoretical basis for explaining why they were true.</p> <div id="inArticleVideo_2-0" class="comp inArticleVideo inArticleVideoPlaceHolder videoPlaceholder"> <figure class="video-placeholder parent-bg group large"> <span class="close"></span> <p>continue reading below our video <span></span></p> <figcaption class="group"> <p class="pull-left">Overview of Kepler's Laws of Planetary Motion</p> </figcaption> <div id="inArticlePlayer_2-0" class="comp inArticlePlayer video-player mntl-video-player" data-player="418de2d8-bf4b-4b9b-8551-f1ece21973b0" data-account="4013" data-video-id="ref:create_95195_title1"> <video data-embed="default" data-video-url="http://physics.about.com/video/Overview-of-Kepler-s-Laws-of-Planetary-Motion.htm" data-ref-id="create_95195_title1" data-frequency-capping="true" data-pause-on-scroll="true" data-volume="4" data-direct-ad-ids="288415327,1grqmf,1grqme,1grqmg,1grafp,1grafn,1grafm,1grafo,1h5r7a,306498723,306501520,306497573,306501519,1h6iho,moat_ad,1273229,299022128,300234477,1273226,299176595,1273227,1273228,1hd3kg,1273230,e9RvM8KWX3lt5o5loocr,0,1hemer,349617894,IntegralAds,342509574,359750694,363636294,349618014,16284097,300771921,1h0pbj,1h0pbi,IntegralAds,1h5r7a,1h5fpr,1h5fpt,1h5fps,307871072,1473876332.1952.17972,1iou9m,1475181209.7727.27788,1475181209.766.27788,1imbd0,1io11u,1478817895.0541.17337,1478817895.0382.17337" data-range-to-play="40" data-disable-preload="false" data-disable-autoplay="false" data-plugins="ga" class="video-js" controls> </video> <div class="loc loadingIcon"> <span id="loading-icon_2-0" class="comp loading-icon"> <div class="spinner"> <div> <div></div> </div> <div> <div></div> </div> <div> <div></div> </div> <div> <div></div> </div> <div> <div></div> </div> <div> <div></div> </div> <div> <div></div> </div> <div> <div></div> </div> <div> <div></div> </div> <div> <div></div> </div> <div> <div></div> </div> <div> <div></div> </div> <div> <div></div> </div> </div> </span> </div> </div> </figure> </div> <p class="cb-split"> The theoretical framework came in the form of <a href="/web/20161118041151/http://physics.about.com/od/classicalmechanics/a/gravity.htm" data-component="link" data-source="inlineLink" data-type="internalLink" data-ordinal="1">Newton's Law of Gravity</a>, nearly a century later. Newton's universal gravitation can be used to prove that Kepler's Laws do indeed describe the motion of planetary bodies in orbit.</p> </div> </article> <div id="chaptersChop_1-0" class="comp chaptersChop col-push-2 col-push-tablet-1"> <div class="fadeout"></div> <a href="#" data-component="chaptersChop" data-source="Navigation" data-type="viewMore" data-ordinal="1" class="btn btn-light"> <div class="label"> <span class="text">Show Full Article</span> <span class="arrow arrow-down"></span> </div> </a> </div> <div class="col-push-2 col-push-tablet-1 post-content"> <div class="relatedList bulleted-list group"> <div class="col row-fluid"> <h5 class="heading slab-heading p-col">Related</h5> <ul class="col-15 col-tablet-12"> <li><a href="https://web.archive.org/web/20161118041151/http://space.about.com/od/astronomybasics/tp/Keplers_Three_Laws.htm" data-component="relatedList" data-source="Recirculation" data-type="Data Science Link" data-ordinal="1">Meet the Scientist Who Explained Our Solar System's Motions</a></li> <li><a href="https://web.archive.org/web/20161118041151/http://space.about.com/cs/astronomy101/a/astro101c.htm" data-component="relatedList" data-source="Recirculation" data-type="Data Science Link" data-ordinal="2">Astronomy through the Renaissance</a></li> <li><a href="https://web.archive.org/web/20161118041151/http://space.about.com/od/astronomerbiographies/a/The-Death-Of-Tycho-Brahe.htm" data-component="relatedList" data-source="Recirculation" data-type="Data Science Link" data-ordinal="3">The Death of Tycho Brahe</a></li> <li><a href="https://web.archive.org/web/20161118041151/http://space.about.com/od/astronomybasics/a/Astronomy.htm" data-component="relatedList" data-source="Recirculation" data-type="Data Science Link" data-ordinal="4">Introducing the Science of Astronomy</a></li> </ul> </div> </div> <div id="zergnet_1-0" class="comp zergnet"> <div class="row"> <div class="col zergWidget col-8"> <div class="zergnet-header"> <h5 class="heading slab-heading p-col zergheading">More from the Web</h5> <div class="powered">Powered By ZergNet</div> </div> <div data-zergnetid="40874" class="zergnet-container bulleted-list"> <div id="zergnet-widget-40874"></div> </div> </div> </div> </div> </div> </div> <div class="col col-4 infinite-rail"> <div class="gpt billboard"> <div id="billboard" class="wrapper"></div> </div> <div id="newsletterSplit_3-0" class="comp newsletterSplit newsletter newsletter-container pre-submit p-bg group widget newsletter-split"> <div class="widget-heading p-b-t-col"> <div class="sprite envelope-signup"></div> <h5 class="heading p-col initial"> Sign Up for Our Free Newsletters </h5> <h5 class="heading p-col additional">Thanks, You're in!</h5> </div> <form action="/web/20161118041151/http://physics.about.com/newsletter/signup" class="d-bg-t"> <div class="checkboxes initial form-group"> <label> <input type="checkbox" name="list[]" value="todaysl"/> <span class="box p-col"></span> <span>About Today</span> </label> <label> <input type="checkbox" name="list[]" value="calcount"/> <span class="box p-col"></span> <span>Healthy Eating</span> </label> <label> <input type="checkbox" name="list[]" value="wilat"/> <span class="box p-col"></span> <span>What I Learned About Today</span> </label> </div> <div class="checkboxes additional form-group"> <div class="sub-heading">You might also enjoy:</div> <label> <input type="checkbox" name="list[]" value="healthtipsl"/> <span class="box p-col"></span> <span>Health Tip of the Day</span> </label> <label> <input type="checkbox" name="list[]" value="recipeodsl"/> <span class="box p-col"></span> <span>Recipe of the Day</span> </label> </div> <div class="email-group form-group"> <input type="email" name="email" class="email" placeholder="Enter your email"/> <div class="newsletter-submit"> <div> <button type="submit" class="btn a-bg d-col s-b-col all-caps ">Sign up</button> </div> </div> <div class="error ajax-fail">There was an error. 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