um, the GR equivalence principle states that gravity is indistinguishable from acceleration.
I don't like the bowling ball on the rubber sheet thing either. Apart from the fact that the emphasis is on the third dimension (ie down) when it's supposed to be a 2D model, it also appears to rely on gravity itself to to pull the marble or whatever in towards the bowling ball.
Not that I have any better way of visualising curvature of 4D spacetime I'm afraid :-/
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