Having developed a framework for subsuming gravity into relativity, we examine how gravity behaves as a function of the source mass (Earth, Sun, etc.) and distance from that sourcemass.We develop Newton’s inverse‐square law of gravity, and we examine the consequences in terms of acceleration fields, potentials, escape velocities, and surface gravity. Chapter 17 will build on these ideas to show how orbits are used to probe gravity throughout the universe.We also develop a tool for exposing variations in the acceleration field: the tidal acceleration field in any region is defined as the acceleration field in that region minus the average acceleration. This enables us to restate Newton’s lawof gravity as: the acceleration arrows surrounding any point show a net convergence that is proportional to the density of mass at that point. Chapter 18 will use this to develop a frame‐independent law of gravity.
Obtaining Earth surface gravity disturbances from a GPS-based ‘high-low’ satellite-to-satellite tracking experiment
