I've recently bean reading a book about string theory (thats not important though) and I came across something that someone here may be able to help me with, I'd really appreciate it, its been bugging me for days. I may have misinterpreted, so if I have please correct me. In a general introduction the book described the relationship between mass and energy as described by E=Mc2. It also talked about sub-atomic particles, among which there was a small passage on the Graviton (and the lack thereof). It said that it theretically has no mass. If this is so does it also mean that it has no energy? I'm probably totally wrong and will be summarily chastised for my ridiculous question, but I would be eternally greatful if someone could explain this to me. Also if you could do it as if you were talking to a rather stupid child I would appreciate it. Thanks for any clarification that can be given.