"The Spacecraft Flyby Mystery" - Is Dark Matter the Culprit or is There a New Physics Waiting to be Discovered?

"The Spacecraft Flyby Mystery" - Is Dark Matter the Culprit or is There a New Physics Waiting to be Discovered?: "When scientists send their spacecraft across the universe, they save fuel by performing “slingshot fly-bys”. This is where, rather than firing up the thrusters, the craft changes its trajectory by harnessing the enormous gravitational pull of a planet. However, this trick has had an unexpected side-effect: it seems to produce a change in speed that no one, since it was first discovered in the early 1990's, can account for."