1. The problem statement, all variables and given/known data The best relative gravimeters have a relative uncertainty of 10-12, that corresponds to a height difference of 3 µm. 2. Relevant equations g∝(1/r2) The local gravitational acceleration g outside the Earth is proportional to 1/r2, which means (Δg)/g = -2 (Δr)/r. With (Δg)/g = 10-12 we get Δr = 0.5 * 10-12 r where r is the radius of Earth. 3. The attempt at a solution I've tried to get to the equation I highlighted in red, but I fail. I know it has derived from taking derivatives, but my derivatives result in different equations. g∝1/r2 → g=k(1/r2) → ?