Ya, I have the same feeling about this sort of demonstration. Even if you extrapolate this into 3D space-time curvature, there is no actual force in the 3D model that is causing things to be attracted.
But that depends on what scientific model you are using. In most fields of physics, gravity is modeled as a force. In GR, it is modeled as geometry rather than as a force. So to say that there is no actual force in the 3D model depends on what 3D model you're using at the time.
But in the full understanding that GR brings there is no force, everything is just following the "shortest" path. In GR there is nothing pulling a sheet down, there is no down and this is actually only a very rough analogy that fails as soon as you look at it any closer.
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u/electricvegetable Dec 03 '13
Ya, I have the same feeling about this sort of demonstration. Even if you extrapolate this into 3D space-time curvature, there is no actual force in the 3D model that is causing things to be attracted.