{"page":"\u003clink rel=\"stylesheet\" href=\"https://lessonplanet.com/assets/packs/css/resources-572d6a42.css\" /\u003e\n\u003clink rel=\"stylesheet\" href=\"https://lessonplanet.com/assets/packs/css/lp_boclips_stylesheets-f4d0de30.css\" media=\"all\" /\u003e\n\u003cdiv data-title='Understanding 4D Spacetime and Relativity Visually and Simply' data-url='/boclips/videos/689564777cbf35e76a835625' data-video-url='/boclips/videos/689564777cbf35e76a835625' id='bo_player_modal'\u003e\n\u003cdiv class='boclips-resource-page modal-dialog panel-container'\u003e\n\u003cdiv class='react-notifications-root'\u003e\u003c/div\u003e\n\u003cdiv class='rp-header'\u003e\n\u003cdiv class='rp-type'\u003e\n\u003ci aria-hidden='true' class='fai fa-regular fa-circle-play'\u003e\u003c/i\u003e\nVideo\n\u003c/div\u003e\n\u003ch1 class='rp-title' id='video-title'\u003e\nUnderstanding 4D Spacetime and Relativity Visually and Simply\n\u003c/h1\u003e\n\u003cdiv class='rp-actions'\u003e\n\u003cdiv class='mr-1'\u003e\n\u003ca class=\"btn btn-success\" data-posthog-event=\"Signup: LP Signup Activity\" data-posthog-location=\"body_link_boclips\" data-remote=\"true\" href=\"/subscription/new\"\u003e\u003cspan\u003e\u003cspan\u003eGet Free Access\u003c/span\u003e\u003cspan class=\"\"\u003e for 10 Days\u003c/span\u003e\u003cspan\u003e!\u003c/span\u003e\u003c/span\u003e\u003c/a\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv class='rp-body'\u003e\n\u003cdiv class='rp-info'\u003e\n\u003cdiv aria-label='Hide resource details' class='rp-hide-info' role='button' tabindex='0'\u003e\u0026times;\u003c/div\u003e\n\u003ci aria-label='Expand resource details' class='rp-expand-info fai fa-solid fa-up-right-and-down-left-from-center' role='button' tabindex='0'\u003e\u003c/i\u003e\n\u003ci aria-label='Compress resource details' class='rp-compress-info fai fa-solid fa-down-left-and-up-right-to-center' role='button' tabindex='0'\u003e\u003c/i\u003e\n\u003cdiv class='rp-rating'\u003e\n\u003cspan class='resource-pool'\u003e\n\u003cspan class='pool-label'\u003ePublisher:\u003c/span\u003e\n\u003cspan class='pool-name'\u003e\n\u003cspan class='text'\u003e\u003ca data-publisher-id=\"30356011\" href=\"/search?publisher_ids%5B%5D=30356011\"\u003eCurated Video\u003c/a\u003e\u003c/span\u003e\n\u003c/span\u003e\n\u003c/span\u003e\n\u003c/div\u003e\n\u003cdiv class='rp-description'\u003e\n\u003cspan class='short-description'\u003eSummary: How to visualize Minkowski four dimensional spacetime and relativity using light cones and world lines. These are three spatial dimensions and one time dimension in the universe. With these 4 coordinates, you could rendezvous...\u003c/span\u003e\n\u003cspan class='full-description hide'\u003eSummary: \u003cbr/\u003eHow to visualize Minkowski four dimensional spacetime and relativity using light cones and world lines. These are three spatial dimensions and one time dimension in the universe. With these 4 coordinates, you could rendezvous with anyone anywhere in the universe. In fact these 4 dimensions can describe any event in the universe. \u003cbr/\u003e  \u003cbr/\u003eBut how did the idea of time as a dimension come about? How can we best visualize these 4 dimensions? And what really happens when space and time start doing seemingly weird things when two objects move relative to each other? \u003cbr/\u003e\u003cbr/\u003eIn the late 1800’s, scientists had recognized that there was an inconsistency between two theories – Newton’s laws of motion, and Maxwell’s equations describing electricity and magnetism. The problem was the speed of light. \u003cbr/\u003e\u003cbr/\u003eMaxwell had shown that light was a self-propagating electromagnetic wave. And his theory predicted its speed to be about 300,000 km/s. \u003cbr/\u003e\u003cbr/\u003eThe question was what would the measured speed of light be if the person measuring it was moving. According to Newton, this moving observer should measure a different speed, than someone who was not moving. The measured speed should be the speed of the person, PLUS the speed of light. \u003cbr/\u003e\u003cbr/\u003eIn 1887, Michelson and Morley devised a highly sensitive experiment to measure the speed of light in the direction of motion of the earth. They found that the speed of light does not vary at all, due to the motion of the earth. A resolution of this unexpected result came from Albert Einstein who proposed that Newton’s laws of motion needed to be modified. He determined that the speed of light does not change in any reference frame, and worked out the implications of this idea. \u003cbr/\u003e\u003cbr/\u003eEinstein showed that observers moving at different speeds will disagree about distance and time between two events. In other words, they will experience space and time differently. \u003cbr/\u003e\u003cbr/\u003eHermann Minkowski realized that relativity is really a theory about the geometrical relationship between space and time, and coined the term \"spacetime.\" He suggested an easier way to visualize these four dimensions - by eliminating one of the dimensions, and making the vertical axis time, but in terms of length.\u003cbr/\u003e\u003cbr/\u003eSomething not moving spatially would be depicted as a vertical line. This is called called this a world line for the particle. \u003cbr/\u003e\u003cbr/\u003eA uniformly moving point would be depicted as a diagonal line on this graph because it would be moving in at least one of the spatial coordinates as it is moving forward in time. An accelerating particle would be a curved line. A light flash somewhere in this 2D space would spread in all directions with time. This forms the shape of a cone. So Minkowski called this a light cone. \u003cbr/\u003e\u003cbr/\u003eA light cone represents all the future events in spacetime that the light reaches from its initial event A. An upside down cone is the past light cone, and represents all the past events in spacetime that reach Event A.\u003cbr/\u003e\u003cbr/\u003eEvent A can be you here and now. The points outside these two light cones are causally disconnected from event A, meaning they cannot reach or be reached by event A. \u003cbr/\u003e\u003cbr/\u003eHow does special relativity enter affect world lines and light cones. Two observers moving relative to each other will not agree on simultaneity. Each will perceive the other's light cone as being tilted such that their observations being different can be explained. \u003cbr/\u003e#minkowskispacetime\u003cbr/\u003e#lightcones\u003cbr/\u003e#worldlines \u003cbr/\u003eWhat this shows is that simultaneity is relative to the observer. There is no absolute simultaneity in the universe. But each observer sees and experiences exactly the same spacetime. And both will agree on causality. Causality is always preserved in a universe with a finite speed of light. I will have more details on this issue of causality in a future video.\u003c/span\u003e\n\u003c/div\u003e\n\u003cdiv class='action-container flex justify-between'\u003e\n\u003cbutton aria-expanded='false' aria-label='Read more description' class='rp-full-description' type='button'\u003e\n\u003ci class='fai fa-solid fa-align-left'\u003e\u003c/i\u003e\n\u003cspan id='read_more'\u003eRead More\u003c/span\u003e\n\u003c/button\u003e\n\u003cdiv class='rp-report'\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv aria-labelledby='resource-details-heading' class='rp-info-section'\u003e\n\u003ch2 class='title' id='resource-details-heading'\u003eResource Details\u003c/h2\u003e\n\u003cdiv class='rp-resource-details clearfix'\u003e\n\u003cdiv class='detail'\u003e\n\u003cdl\u003e\n\u003cdt\u003eCurator Rating\u003c/dt\u003e\n\u003cdd\u003e\u003cspan class=\"star-rating\" aria-label=\"4.0 out of 5 stars\" role=\"img\"\u003e\u003ci class=\"fa-solid fa-star text-action\" 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