| Astrophysics (Index) | About |
A PPN formalism (for parameterized post-Newtonian formalism) is a type of technique for representing gravity as Newtonian gravity plus a term (or terms, "correction terms") covering the differences between Newtonian gravity and general relativity (GR). In that, it is a post-Newtonian formalism (PN formalism), but it is specifically one that breaks out the full adjustment into contributions from various factors, e.g., curvatures due to various circumstances, such as the curvature specifically stemming from nearby mass. As a PN-formalism, it can be used to produce a closer approximation of GR-based gravity than Newton's laws, without carrying out an exact GR calculation. The parameterization allows customization to a particular situation, providing the means to ignore specific factors that are known to be insignificant in a particular case. It also provides a means of tinkering with GR, to explore the consequences of various GR modifications, and evaluate them by matching calculations with observed data.