Newtonian gravity cannot explain galaxy dynamics and their rotation curves. But can General Relavity explain them? We explore the linear approximation of General Relativity (gravitomagnetism) and apply it the orbits of stars in galaxies. The question of whether boundary conditions can play a role in explaining the dark matter effects in galaxies is also addressed.
How General Relativity fails to explain Galaxy Dynamics Read More »
Mach’s principle deeply influenced Einstein’s General Relativity, and following attempts to extend gravity theories. It’s implications and ideas are explained in relation to relative acceleration, inertial forces, Newton’s bucket of water experiment, and the gravitational constant, as an introduction to theories of modified inertia such as MOND.
Mach’s principle: introduction to MOND and modified inertia Read More »
The lack of a phenomenological explanation of Modified Newtonian Dynamics and its falling short in galaxy clusters suggest that MOND is an approximation of a more fundamental theory of modified gravity or inertia. There are strong indications that point towards a Machian origin of MOND, providing an explanation for the apparent dark matter effects in galaxies. The origin of inertia and a derivation of the gravitational constant are also related to these problems in gravitation.
Milgrom’s Modified Newtonian Dynamics (MOND) correction to Newtonian gravity is shown to be equivalent to a more fundamental transformation between a non-inertial local reference frame and the fixed background of the observable universe, complying with Mach’s principle. This Machian MOND approximation is a necessary feature of a nonlinear phenomenological theory of modified inertia or modified gravity which incorporates Mach’s principle in agreement with galaxy rotation curves.