text: why does gravity exists?????????? why two bodies always attract why cant they repel each other? what is the source  of gravity????????? if you're trying to visualize it, there are a couple of images that you can use as props. imagine that i have a bowling ball and i drop it into the middle of a mattress. now imagine that i take a marble and drop it onto that mattress. the path of the marble will be altered by the curvature that (in this case, the weight) of the bowling ball creates along the mattress, and the marble will roll down into the dip that it created.  now imagine that the universe retains the same qualities of the mattress, but -- to explain it very simply, because there are many more likely dimensions -- it's three dimensional, and when you drop the bowling ball, it's "suspended" (like a marble in jell-o), and the path that it creates along it in space encompasses the entire ball, and becomes greater with mass.  there you have an extremely short and deceptively simple answer that will help introduce you to the tougher concepts.   pick up a copy of hyperspace, by michio kaku, the cofounder of superstring theory. he's a brilliant physicist and a fun read.