Thanks for the link Jade!!!!!
The future of astronomy and space exploration gets more exciting every year...especially 2016 it seems with the Centauri System news sophisticated satelites on their way to planets and their moons.
The private ventures towards Proxima B and that group are a sea change.
Well, there are many known forces at play. The "missing mass" was not the sort of thing finding missing rocks/planets, etc, could "find".
It was the extra gravitational effect observed on KNOWN objects that indicated that energy and mass were (both) out there and unaccounted for.
So, the unknown part, above, is what they are rushing to explore.
I read the other day that the EM Drive might be using dark energy/mass for example, as a way to have it stay compliant with known physical laws.
If its thrust continues to be confirmed, and no exhaust is involved, well, action/reaction goes out the window.
If the exhaust ends up being "dark", it would explain it.
Of course, it could still be a fluke of the test methodology, etc....and not actually work.