Figure 1

Figure 1: A parameter space for quantifying the strength of a gravitational field. The x-axis measures the potential ε ≡ GM ∕rc2 and the y-axis measures the spacetime curvature ξ ≡ GM ∕r3c2 of the gravitational field at a radius r away from a central object of mass M. These two parameters provide two different quantitative measures of the strength of the gravitational fields. The various curves, points, and legends are described in the text.