Parameterized post-Newtonian formalism | Wikipedia audio article
Channel: wikipedia tts
Date: 08/12/2018

This is an audio version of the Wikipedia Article:
Parameterized post-Newtonian formalism


00:01:27 1 History
00:02:21 2 Beta-delta notation
00:03:51 3 Alpha-zeta notation
00:04:39 4 How to apply PPN
00:04:49 5 Comparisons between theories of gravity
00:09:40 6 Accuracy from experimental tests
00:10:18 7 See also
00:28:55 8 References
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00:40:36 undefined
00:41:33 undefined



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SUMMARY
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Post-Newtonian formalism is a calculational tool that expresses Einstein's (nonlinear) equations of gravity in terms of the lowest-order deviations from Newton's law of universal gravitation. This allows approximations to Einstein's equations to be made in the case of weak fields. Higher-order terms can be added to increase accuracy, but for strong fields, sometimes it is preferable to solve the complete equations numerically. Some of these post-Newtonian approximations are expansions in a small parameter, which is the ratio of the velocity of the matter forming the gravitational field to the speed of light, which in this case is better called the speed of gravity. In the limit, when the fundamental speed of gravity becomes infinite, the post-Newtonian expansion reduces to Newton's law of gravity.
The parameterized post-Newtonian formalism or PPN formalism, is a version of this formulation that explicitly details the parameters in which a general theory of gravity can differ from Newtonian gravity.  It is used as a tool to compare Newtonian and Einsteinian gravity in the limit in which the gravitational field is weak and generated by objects moving slowly compared to the speed of light. In general, PPN formalism can be applied to all metric theories of gravitation in which all bodies satisfy the Einstein equivalence principle (EEP). The speed of light remains constant in PPN formalism and it assumes that the metric tensor is always symmetric.