Anti-de Sitter space bell. It might be described as being the "opposite" of the surface of a sphere, which has a positive curvature. General relativity is a theory of the nature of time, space and gravity in which gravity is a curvature of space and time that results from the presence of matter or energy. Energy and mass are equivalent (as expressed in the equation "E" = "mc"), and space and time can be translated into equivalent units based on the speed of light ("c" in the "E" = "mc" equation). A common analogy involves the way that a dip in a flat
Kepler's equation distance from the centre of attraction along the ray. This equation is derived by multiplying Kepler's equation by 1/2 and setting "e" to 1: and then making the substitution Calculating "M" for a given value of "E" is straightforward. However, solving for "E" when "M" is given can be considerably more challenging. There is no closed-form solution. One can write an infinite series expression for the solution to Kepler's equation using Lagrange inversion, but the series does not converge for all combinations of "e" and "M" (see below). Confusion over the solvability of Kepler's equation has persisted in the literature