Geodesic (general relativity) | Wikipedia audio article
Channel: wikipedia tts
Date: 2018-12-24

This is an audio version of the Wikipedia Article:
https://en.wikipedia.org/wiki/Geodesics_in_general_relativity


00:00:44 1 Mathematical expression
00:02:54 2 Equivalent mathematical expression using coordinate time as parameter
00:06:08 3 Derivation directly from the equivalence principle
00:18:46 4 Deriving the geodesic equation via an action
00:39:26 5 Equation of motion may follow from the field equations for empty space
00:41:07 6 Extension to the case of a charged particle
00:47:14 7 Geodesics as curves of stationary interval
00:52:16 8 See also
00:52:33 9 Bibliography



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SUMMARY
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In general relativity, a geodesic generalizes the notion of a "straight line" to curved spacetime. Importantly, the world line of a particle free from all external, non-gravitational force, is a particular type of geodesic. In other words, a freely moving or falling particle always moves along a geodesic.
In general relativity, gravity can be regarded as not a force but a consequence of a curved spacetime geometry where the source of curvature is the stress–energy tensor (representing matter, for instance).  Thus, for example, the path of a planet orbiting a star is the projection of a geodesic of the curved 4-D spacetime geometry around the star onto 3-D space.