Let's wonder a little that there is no earth, no other planet, no sun, no galaxy, no universe, there is nothing at all. Somewhere in that nothingness a huge (or little, actually doesn't matter, as there is nothing else to compare with) amount of fluid, let's say a huge drop of fluid appeared. The water drop might have a distinct surface or it might have something like earth's atmosphere that doesn't have a distinct line separating from outside space. Though n this case, there is no outside space. Whatever happens, has to happen in the inside of it. Nothing can exist outside of it. Now, think, something appears in it. Well, whatever appears in the fluid has very much different properties than the fluid. Let's make the fluid's properties as much different from the bodies in it as you can imagine. As if it runs on completely different physical laws. As something has appeared in it, the fluid had to make it some space and the fluid has curved around ...