Gravity... reversal... problem...!

What is gravity? Yep we know what it does but what is it? One of my little theories is this: Gravity is the effect of matter passing through space (by 'space' I mean whatever space is really made of), I kind of negative pressure across a multidimensional surface.
Illustration: When riding a bike and being passed by a bus, you can feel yourself being drawn towards the bus. As the moving bus cuts through the still air it creates a negative pressure around and behind itself.