Hi, I had a question about reactions. I actually know how the baryon number, the lepton number, and the electric charge conservation works for reactions, but what i do not understand is the energy conservation. I searched the whole web for it, but there was no page where I could understand the stuff. i know that it has something to do with mass, that the mass of a neutron is higher than that of a proton. For example: p + p > p + n .... i know that the electric charge is not correct, so I need a positron, but then the lepton number is not correct, so i need a ve. >> p + p > p + n + e+ + ve ... but what about the energy, how can i find out if the energy conservation is oki, and what I have to add to make it work? It would be really cool if someone could help me out here!