Gravitons?How can a spin of 2 and a mass of zero be assigned to it,if were not sure they exist. in space?

Answer 1

Because gravity is a 2nd rank tensor field, and the equations governing it operate in such a way. Is just a fancy way of saying gravity exhibits variable geometry. As such the equations dont make sense with spin 0 or 1. Theres no law saying spin cant be 2, it just has to be a whole number. and the zero mass just means the graviton moves at the speed of light and can never be at rest, like a photon.