Return Paths in the Ground Plane

So at high frequencies the return current tries to minimize the enclosed area shown in 

A thoughtless cut in the Ground Plane can divert the return current away from its preferred path (underlying the forward trace), thereby increasing the area of the enclosed high-frequency current loop and therefore also the inductance 

Roll a disc horizontally. Then, a given point on its rim will trace out a cycloid curve 

Two balls (of any size) rolling down between two points A and B The ball rolling down the brachistochrone oath always wins 

In general, the preferred path between two points is not necessarily the shortest in length (i.e., a straight line) 

---