Why is there 0 gravity in space? From what I know, in fact I do not know much about SR and GR, so I'm hoping to learn more. In GR, it states that anything which has mass causes a curvature in spacetime, which causes gravity. Why is it that even though we have mass, astronauts travelling in space do not experience gravity at all? Also, why is it that massless photons do feel the gravitational force.