Imagine a particle that interacts strongly with gravity, but not with any of the other forces, and does not interact with normal matter (this may be analogous to the description of dark matter, I'm not sure). If this particle was travelling towards earth, where would its rest state be?

[![enter image description here](https://i.stack.imgur.com/Gqnqq.gif)](https://i.stack.imgur.com/Gqnqq.gif)

Based on the above diagram I would assume the rest point would be at the peak of the graph, in the area between the outer core and upper mantle, at a radius of roughly 3,500km. 

This would mean that gravity has two directions. If the aforementioned particle was at a radius of 2,000km, it would be attracted 'up' towards 3,500km. And if it was at 8,000km, it would be attracted 'down' towards 3,500km.

Could this be considered a kind of polarity in the gravitational field?