The modern method consists of numerical integration in 3-dimensional space. One starts with a high accuracy value for the position ("x", "y", "z") and the velocity ("vx", "vy", "vz") for each of the bodies involved. When also the mass of each body is known, the acceleration ("ax", "ay", "az") can be calculated from Newton's Law of Gravitation. Each body attracts each other body, the total acceleration being the sum of all these attractions. Next one chooses a small time-step Δ"t" and applies Newton's Second Law of Motion. The acceleration multiplied with Δ"t" gives a correction to the velocity. The velocity multiplied with Δ"t" gives a correction to the position. This procedure is repeated for all other bodies.