Yes, general relativity is out of my depths for now. Now I've often seen drawings of a gravitational source represented by a dimple ( downward ) on a surface. Yet GR never speaks of a fifth dimension. Nor have I ever seen a dimple upwards that I would suppose would represent repulsive gravity which I've never heard to exist. Is gravity more like an optical distortion. A gradient in the index of refraction will curve light and matter too. Surely someone has formulated this, given the "gravitational lens" effect. Is curvature misleading in that it alludes to a higher dimension?