When 2 magentic objects interact with each other, it is because they interact with each others magnetic field, not because their presence alters an existing magnetic field. The way I understood spacetime, the theory goes that a spacetime fabric stretches throughout the known universe and mass bends and curves it. How do we know that is the case? Couldnt it be that there is no such thing as a spacetime fabric and that each object comes with its own spacetime and interacts with the spacetime of other objects? Does light have Mass and is therefore affected by gravity in the same way a rock and planet is affected, or is light 100% massless and therefore if we observe light bending around a gravitational field, we know it is because it follow the curved spacetime and not because it ineracts with the gravitational field as such, because light is massless?