I was wondering about this question when I was reading my new book The Universe in a Nutshell by Stephen Hawking and the images in the book depict space time as a linear fabric. I don't understand how this could be if the sun has a spherical gravitational pull, as we see at the very outermost reaches of our solar system. So if space time is curved down on a linear fabric, how are objects gravitattionally bound below and on top of the Sun? I'm sure there is an explanation, I however can not seem to find it. So any light shed on this subject is very much appreciated.