I am getting stuck trying to solve a differential equation describing the gravitational relationship between two celestial bodies. What I have so far is this: a1 = G m2 (r2 - r1) / ||r2 - r1||^3 a2 = G m1 (r1 - r2) / ||r1 - r2||^3 where: boldface denotes vectors in 3 dimensional Cartesian space G for gravitational constant m for mass r for position a for acceleration I guess my question is where to go from here. I am assuming that the general solution will contain constants relating to initial position and initial velocity for both bodies. My goal is to arrive at a point where I can plot the trajectories of the two bodies using iterations. Essentially a system I can solve using numerical methods such as Euler's. Anyway, any insight into how to solve this kind of problem would be great! Eventually I want to expand it to more than 2 bodies but I need to get comfortable with 2 first before taking the problem to N-bodies. This is for a numerical methods class, and possibly a final project/presentation. Cheers!