general relativity
https://plus.maths.org/content/taxonomy/term/478
enWhat is time?
https://plus.maths.org/content/what-time-0
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Marianne Freiberger </div>
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Everyone knows what time is. We can practically feel it ticking away,
marching on in the same direction with horrifying regularity. Time has
enslaved the Western world and become our most precious commodity. Turn it
over to the physicists however, and it begins to
morph, twist and even crumble away. So what is
time exactly? </div>
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<p><em>In the latest poll of our <a href="https://plus.maths.org/content/science-fiction-science-fact-reports-frontiers-physics">Science fiction, science fact project</a> you told us that you wanted to know what time is. Here is an answer, based on an interview with <a href="http://cosmos.asu.edu/">Paul Davies</a>, a theoretical physicist and cosmologist at
Arizona State University and Director of <a
href="http://beyond.asu.edu/">BEYOND: Centre for Fundamental Concepts
in Science</a>.<p><a href="https://plus.maths.org/content/what-time-0" target="_blank">read more</a></p>https://plus.maths.org/content/what-time-0#commentsFrontiers of physicsmathematical realityentropygeneral relativitygravityquantum mechanicsrelativityspecial relativitythermodynamicstimetime dilationTue, 23 Aug 2011 15:25:34 +0000mf3445524 at https://plus.maths.org/contentWhat is time: The podcast
https://plus.maths.org/content/science-fiction-science-fact-what-time
<div class="rightimage" style="width: 280px;"><img src="/issue36/features/davies/pauldavies.jpg" width="280" height="210" alt="Paul Davies"/><p>Paul Davies</p></div><p>As part of our joint project with <a href="http://www.fqxi.org/community">FQXi</a> called <a href="https://plus.maths.org/content/science-fiction-science-fact-reports-frontiers-physics">Science fiction, science fact</a>, we asked you what question on the frontiers of physics you'd like to have answered. The question that topped our first poll was 'What is time?'. </p><p><a href='http://plus.maths.org/content/sites/plus.maths.org/files/podcast/davies_final.mp3'>Listen to "What is time?"</a></p><p><a href="https://plus.maths.org/content/science-fiction-science-fact-what-time" target="_blank">read more</a></p>https://plus.maths.org/content/science-fiction-science-fact-what-time#commentsFrontiers of physicsmathematical realitygeneral relativitygravityquantum mechanicsrelativityspecial relativitytimetime dilationtime travelTue, 23 Aug 2011 15:02:44 +0000mf3445536 at https://plus.maths.org/contentWhat is general relativity?
https://plus.maths.org/content/what-general-relativity
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David Tong (with the Plus team) </div>
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<p>To celebrate the centenary of the general theory of relativity we asked physicist David Tong to explain the theory and the equation that expresses it. Watch the video or read the article!</p>
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<p><em>When physicists talk about Einstein's equation they don't
usually mean the famous <em>E=mc<sup>2</sup></em>, but another
formula, which encapsulates the celebrated general theory of
relativity. Einstein published that theory a hundred years ago, in
1915. To celebrate its centenary we asked physicist <a href="http://www.damtp.cam.ac.uk/user/tong/">David Tong</a> of the
University of Cambridge to explain what general relativity is and how
Einstein's equation expresses it. You can watch his explanation in the video
below, or read on.</em></p><p><a href="https://plus.maths.org/content/what-general-relativity" target="_blank">read more</a></p>https://plus.maths.org/content/what-general-relativity#commentsEinsteinFP-carouselgeneral relativityrelativityUniversity of CambridgeFri, 12 Jun 2015 10:17:46 +0000mf3446375 at https://plus.maths.org/contentEinstein and relativity: Part I
https://plus.maths.org/content/einstein-relativity
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David Tong </div>
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<p>Read about the rocky road to one of Einstein's greatest achievements: the general theory of relativity, which celebrates its centenary this year.</p>
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<p><em>This article is an abridged version of a talk David Tong gave at the Southbank Centre in London in 2013. You can listen to a sound recording of the talk on <a href="https://soundcloud.com/southbankcentre/david-tong-on-einsteins-theory/">Soundcloud</a>, or watch a video of a very similar talk, aimed at 16 to 17 year-olds, <a href="https://plus.maths.org/content/stories-einstein">here</a>.</em></p>
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<p>2015 is a special year for physics. It is the 100th
anniversary of Albert Einstein's greatest achievement: the <em>general theory of relativity</em>. </p><p><a href="https://plus.maths.org/content/einstein-relativity" target="_blank">read more</a></p>https://plus.maths.org/content/einstein-relativity#commentscreativityEinsteinFP-carouselgeneral relativityrelativityspecial relativityUniversity of CambridgeThu, 04 Jun 2015 15:56:07 +0000mf3446360 at https://plus.maths.org/contentEinstein and relativity: Part II
https://plus.maths.org/content/einstein-and-relativity-part-ii
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David Tong </div>
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<img class="imagefield imagefield-field_abs_img" width="100" height="100" alt="" src="https://plus.maths.org/content/sites/plus.maths.org/files/abstractpics/5/4_jun_2015_-_1621/galaxies_icon.png?1433431315" /> </div>
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<p>General relativity, Einstein's rise to international stardom, and his legacy.</p>
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<p><em>To read about Einstein's motivation for the general theory of relativity and his struggle to formulate it, read the <a href="https://plus.maths.org/content/einstein-relativity">first part</a> of this article.</em></p>
<h3>General relativity</h3>
<p>Einstein's theory changed our understanding of space and time. Before Einstein people thought of space as stage on which the laws of physics play out. We could throw in some stars or some planets and they would move around on this stage.</p><p><a href="https://plus.maths.org/content/einstein-and-relativity-part-ii" target="_blank">read more</a></p>https://plus.maths.org/content/einstein-and-relativity-part-ii#commentscreativityEinsteingeneral relativityrelativityUniversity of CambridgeThu, 04 Jun 2015 15:15:38 +0000mf3446374 at https://plus.maths.org/contentProblems of gravity
https://plus.maths.org/content/problems-gravity
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Marianne Freiberger </div>
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<img class="imagefield imagefield-field_abs_img" width="100" height="100" alt="" src="https://plus.maths.org/content/sites/plus.maths.org/files/abstractpics/5/18_jul_2014_-_1240/icon.jpg?1405683602" /> </div>
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<p>Why (some) physicists want to modify Einstein's general theory of relativity.</p>
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<p>Albert Einstein is an icon and for good reason. His general
theory of relativity, which describes the force of gravity, was an
intellectual tour de force. Not only were his ideas entirely new, they have also stood the test of
time.
Despite this success, some physicists are doing what many would consider sacrilege: they are tinkering with the theory, producing modified versions of it. But why? </p><p><a href="https://plus.maths.org/content/problems-gravity" target="_blank">read more</a></p>https://plus.maths.org/content/problems-gravity#commentsEinsteingeneral relativitygravityphilosophy of cosmologyrelativitysymmetryWed, 23 Jul 2014 09:01:32 +0000mf3446099 at https://plus.maths.org/contentWhat is cosmology?
https://plus.maths.org/content/what-cosmology
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David J. Mulryne </div>
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<p>How big is the Universe? Where did it come from and where is it going? Why is it the way it is? These are just some of the questions cosmologists study.</p>
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<div class="rightimage" style="width: 250px;"><img src="https://plus.maths.org/content/sites/plus.maths.org/files/packages/2013/QM/qmlogo_0.jpg" width="250" height="62" alt="QM logo"/></div><p><em>This article is part of the <a href="https://plus.maths.org/content/researching-unknown">Researching the unknown project</a>, a collaboration with researchers from <a href="http://ph.qmul.ac.uk/">Queen Mary University of London</a>, bringing you the latest research on the forefront of physics. Click <a href="https://plus.maths.org/content/researching-unknown">here</a> to read more articles from the project.</em></p><p><a href="https://plus.maths.org/content/what-cosmology" target="_blank">read more</a></p>https://plus.maths.org/content/what-cosmology#commentscosmologydark energydark mattergeneral relativityrelativityThu, 20 Mar 2014 10:50:06 +0000mf3446050 at https://plus.maths.org/contentA matter of gravity
https://plus.maths.org/content/matter-gravity
<div class="rightimage" style="width: 350px;"><img src="https://plus.maths.org/content/sites/plus.maths.org/files/blog/022014/snowboarder_in_halfpipe.jpg" alt="Snowboarder" width="350" height="233" />
<p>Snowboarders are vulnerable to gravity. Image: <a href="http://commons.wikimedia.org/wiki/File:Snowboarder_in_halfpipe.jpg">Picswiss.ch</a>.</p><p><a href="https://plus.maths.org/content/matter-gravity" target="_blank">read more</a></p>https://plus.maths.org/content/matter-gravity#commentsgeneral relativitygravitational wavegravitational wave detectorgravityinverse square lawspecial relativityThu, 27 Feb 2014 15:58:39 +0000mf3446051 at https://plus.maths.org/contentWhat is space?
https://plus.maths.org/content/what-space
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Marianne Freiberger </div>
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<img class="imagefield imagefield-field_abs_img" width="100" height="100" alt="" src="https://plus.maths.org/content/sites/plus.maths.org/files/abstractpics/5/9_apr_2013_-_1443/icon_space.jpg?1365515021" /> </div>
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<p>Space is the stage on which physics happens. It's unaffected by what happens in it and it would still be there if everything in it disappeared. This is how we learn to think about space at school. But the idea is as novel as it is out-dated.</p>
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<p><em>In the latest poll of our <a href="https://plus.maths.org/content/science-fiction-science-fact-reports-frontiers-physics">Science fiction, science fact project</a> you told us that you wanted to know an answer to this question. So we went to speak to Francesca Vidotto and George Ellis to find out. Click <a href="https://plus.maths.org/content/science-fiction-science-fact-what-space">here</a> to see other articles exploring this question.</em></p><p><a href="https://plus.maths.org/content/what-space" target="_blank">read more</a></p>https://plus.maths.org/content/what-space#commentsFrontiers of physicsmathematical realityblack holecurvature of spacegeneral relativitygravityPlanck unitquantum gravityquantum mechanicsquantum physicsrelativityspacetimeTue, 16 Apr 2013 14:08:03 +0000mf3445881 at https://plus.maths.org/contentQuantum physics really is strange
https://plus.maths.org/content/quantum-physics-strange
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<p>A team of physicists have curbed the hope that quantum physics might be squared with common sense. At least if we want to hang on to Einstein's highly respected theory of relativity. Their result concerns what Einstein called "spooky action at a distance" and it may soon be possible to test their prediction in the lab.</p>
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A team of physicists have curbed the hope that quantum physics might be squared with common sense. At least if we want to hang on to Einstein's highly respected theory of relativity. Their result concerns what Einstein called "spooky action at a distance" and it may soon be possible to test their prediction in the lab. </p><p><a href="https://plus.maths.org/content/quantum-physics-strange" target="_blank">read more</a></p>https://plus.maths.org/content/quantum-physics-strange#commentsmathematical realitygeneral relativityparticle spinquantum entanglementquantum mechanicsquantum physicsrelativityspeed of lightThu, 15 Nov 2012 11:07:43 +0000mf3445808 at https://plus.maths.org/contentMeet the mother theory
https://plus.maths.org/content/mother-all-theories
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Marianne Freiberger </div>
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<p>The holy grail for 21st century physics is to produce a unified theory of everything that can describe the world at every level, from the tiniest particles to the largest galaxies. Currently the strongest contender for such a theory is something called M-theory. So what is this supposed mother of all theories all about?</p>
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<div class="rightimage" style="width: 250px;"><img src="https://plus.maths.org/content/sites/plus.maths.org/files/packages/2013/QM/qmlogo_0.jpg" width="250" height="62" alt="QM logo"/></div><p><em>This article is part of the <a href="https://plus.maths.org/content/researching-unknown">Researching the unknown project</a>, a collaboration with researchers from <a href="http://ph.qmul.ac.uk/">Queen Mary, University of London</a>, bringing you the latest research on the forefront of physics. Click <a href="https://plus.maths.org/content/researching-unknown">here</a> to read more articles from the project.</em></p><p><a href="https://plus.maths.org/content/mother-all-theories" target="_blank">read more</a></p>https://plus.maths.org/content/mother-all-theories#commentsmathematical realityblack holegeneral relativitym-theoryquantum gravityquantum mechanicsquantum physicsrelativitystring theorysupersymmetryThu, 19 Apr 2012 12:47:41 +0000mf3445693 at https://plus.maths.org/contentHidden dimensions
https://plus.maths.org/content/hidden-dimensions
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Marianne Freiberger </div>
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<p>That geometry should be relevant to physics is no surprise — after all, space is the arena in which physics happens. What is surprising, though, is the extent to which the geometry of space actually determines physics and just how exotic the geometric structure of our Universe appears to be. <em>Plus</em> met up with mathematician Shing-Tung Yau to find out more.</p> </div>
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<p>Shing-Tung Yau.</p>
</div><p>That geometry should be relevant to physics is no surprise — after all, space is the arena in which physics happens. What is surprising, though, is the extent to which the geometry of space actually determines physics and just how exotic the geometric structure of our Universe appears to be. </p><p><a href="https://plus.maths.org/content/hidden-dimensions" target="_blank">read more</a></p>https://plus.maths.org/content/hidden-dimensions#commentsmathematical realitycalabi-yau manifoldcurvaturecurvature of spacedimensiongeneral relativitygravitystring theoryTue, 21 Dec 2010 15:38:56 +0000mf3445388 at https://plus.maths.org/contentHow does gravity work?
https://plus.maths.org/content/how-does-gravity-work
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And what are gravitational waves? </div>
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<div class="pub_date">29/09/2009</div>
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<p>B.S. Sathyaprakash</p><p><a href="https://plus.maths.org/content/how-does-gravity-work" target="_blank">read more</a></p>https://plus.maths.org/content/how-does-gravity-work#commentsastronomyblack holecosmologyEinsteingeneral relativitygravitational wavegravitational wave detectorgravityinternational year of astronomy 2009Newtonspecial relativityMon, 28 Sep 2009 23:00:00 +0000plusadmin2827 at https://plus.maths.org/contentThe illusory Universe
https://plus.maths.org/content/illusory-universe
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Marianne Freiberger </div>
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With online socialising and alternative realities like <i>Second Life</i> it may seem as if reality has become a whole lot bigger over the last few years. In one branch of theoretical physics, though, things seem to be going the other way. String theorists have been developing the idea that the space and time we inhabit, including ourselves, might be nothing more than an illusion, a hologram
conjured up by a reality which lacks a crucial feature of the world as we perceive it: the third dimension. <i>Plus</i> talks to <b>Juan Maldacena</b> to find out more. </div>
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<p><i>With many of us living a good chunk of our lives online it may seem as if reality has become a whole lot bigger over the last few years. In one branch of theoretical physics, though, things seem to be going the other way. Over the last two decades string theorists have been developing the idea that the space and time we inhabit, including ourselves, might be nothing more than an
illusion, a hologram conjured up by a reality which lacks a crucial feature of the world as we perceive it: the third dimension.<p><a href="https://plus.maths.org/content/illusory-universe" target="_blank">read more</a></p>https://plus.maths.org/content/illusory-universe#comments5151ablack holecosmologyentropygeneral relativityholographic principlequantum gravityquantum mechanicsrelativitystring theoryTue, 30 Jun 2009 23:00:00 +0000plusadmin2364 at https://plus.maths.org/contentLambda marks the spot — the biggest problem in theoretical physics
https://plus.maths.org/content/lambda-marks-spot-mdash-biggest-problem-theoretical-physics
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Rachel Thomas </div>
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The mathematical maps in theoretical physics have been highly successful in guiding our understanding of the universe at the largest and smallest scales. Linking these two scales together is one of the golden goals of theoretical physics. But, at the very edges of our understanding of these fields, one of the most controversial areas of physics lies where these maps merge: the cosmological
constant problem. </div>
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<p><i>The mathematical maps of theoretical physics — the Standard Model of particle physics and the Big Bang model of cosmology — have been highly successful in guiding our understanding of the Universe at the largest and smallest scales. Linking these two scales together is one of the golden goals of theoretical physics. But at the point where these maps merge, at the very edges of our
understanding of these fields, lies one of the most controversial concepts in physics: the cosmological constant.</i></p><p><a href="https://plus.maths.org/content/lambda-marks-spot-mdash-biggest-problem-theoretical-physics" target="_blank">read more</a></p>https://plus.maths.org/content/lambda-marks-spot-mdash-biggest-problem-theoretical-physics#comments5151aBig Bangcosmological constantcosmologydark energyFRW metricgeneral relativityparticle physicsstandard modelvacuum energyMon, 01 Jun 2009 21:30:00 +0000plusadmin2362 at https://plus.maths.org/content