What I cannot imagine is how (I assume a person) could get objectivly outside of time or space to journey around this so-called denisity, he would need to become non-phyical it seems? But your example of the hill - running up and down, or down and up, and down again, might offer an alternative pathway that would be faster, flying over the hill like a bird. Same distance and same amount of gravity but with less resistance.
But then, with my lack of knowledge about physics I might not even be "on topic".
I once had this one book (formally being a book dealer) that seemed like it would be interesting. It took some of the science fiction ideas used for the Star Trek TV show and proved they are workable if you did the math. The process used to "beam me up Scotty" and the ideas of "time warp speed" were written about in this physics book. Anyone here read it?
Amazon.com: The Physics of Star Trek: Books: Lawrence M. Krauss,Stephen Hawking