I assume general relativity allows us in principle to calculate volumes of some region of space? If so, if I have a large volume of space far from other mass and energy does it make sense to ask how much a large volume of space changes depending on whether or not it contains the mass of single hydrogen atom? For simplicity assume a point mass. I know any such change will be very small but in principle can this question be answered? Does a large box of space with matter in it have a greater volume then a similar sized empty box? Thanks for any help!