This is a hypothetical question. What would happen if everything in the Universe was scaled up (or down) in size by a constant factor? Starting from the nuclei in atoms, ending with galaxies; assume that all proportions would be kept intact, i.e. all distances are scaled up by the same factor. Can we be sure this is not actually happening at the moment? I had a pop-sci book once that claimed we would not be able to detect the change in classical Newtonian physics (i.e. without taking into account the fact that the speed of light is constant and would not change). I found this claim doubtful. My reasoning is: because the volume of an object is proportional to the cube of its radius, while the gravitational pull towards an object is inversely proportional to the square of the distance. Therefore in a "scaled up" universe the gravitational pull would be stronger. Would the gravitational constant change as well? And inertia?