I'm trying to follow the derivation in http://arxiv.org/pdf/physics/0508030v4.pdf, but I have no idea where equation 5 comes from: ------ For a light particle with mass m, total energy E and angular momentum L (with respect to the Sun's center) and where the Sun has mass M, the eccentricity epsilon is epsilon = sqrt(1 + (2 E L^2)/(G^2 m^3 M^2)) (5) ------ I could probably get some of that by dimensional analysis, but certainly not all of it. How would one derive this? -- Mike Stay - metaweta@gmail.com http://www.cs.auckland.ac.nz/~mike http://reperiendi.wordpress.com