Exactly. I don't understand what's new in this paper. We've known for decades that since gravity is a force with unlimited range and information cannot be destroyed, you could work out the positions, masses, and motions of the entire earth and everything on it by monitoring a single object with enough precision and isolation.
It's non-unique - there are an infinite number of configurations of mass that could have cause that single object to move in exactly the way it was measured.
