Hello. I was wondering how we know the gravity field expand from its source. Theoricaly as soon as "a mass" (it could be "pure energy "but let us do simple work) appear , a field spread and expand at light speed from this point, curving space (or making it possible to attrract an other mass, the alternativ newtonian model). So fare so good... But how do we know this ? Ocham rasor ? Obvious thinking ? Observation ? Hum... <But what say science ? Nothing as far as i tried to figure out (but i am open minded and perhaps someone can give me some proof of it). An alternativ possibility (I dont say it is the truth, but unlike there is a proof against this, this is a valid hypothesis) : Mass is spreading some "mass particles", graviton or whatever. These particles "sprays" and propagate at lights speed from the mass. So. A mass m has a flux of m*k. Some of theses particles propagates at speed of light and the majority remains at proximity of the mass. The volume around the mass is filled (because of the flux) with these "mass particles" and are curving space. Therefore, around the mass, we have a 1/d*d force. But far from the mass, we have only a few "mass particles" that have colonised the space-time. This is why, the question : What is the gravitational force at d distance ? is unrelevant without specifying ... when., The gravitational field depends on the filling of the space with these "mass particles". The problem is very accurate if you consider that in a galaxy, a star is loosing mass and therfore the flux in wide space of the "mass particles" can be very different of the actual state of the star. So the question. Do we know (any observation ?) if the value of the gravitational force (space curvature) is realy spreading with the anticipated value ?