Please help me to find a formula to determine the actual position of two objects, depending on time. Imagine two identical (mass, size, etc) object, no other effect on them only the gravity of each other (Newton). Let's imagine these objects are non corporal, so they will not collide. The begining state: speed, v=0, distance between them: 2*a; If there would be constant acceleration, we could use the f(t)=x=v0*t+(a/2)*t^2 to determine their actual position depending on time. But our case is different, the acceleration is changing. F=G*(m*m)/(d*d) Is there a simple formula now to determine the positions of the objects? I tried to thinking this way: Unlike by the constant acceleration, now we will get a periodic path. The two objects are the special case of a circle/elliptic path (the objects are circulating around each other) The formula for the ellipse: x=a*cos(q) y=b*sin(q) In our case b=0. But now I'm stucked, because I think that the q is not representing the time. (Am I right?) Thank you for your help!