Plotting the Gravitational Force Field in 3-Dimensions

> fieldplot3d(F_grav,x=-2..2,y=-2..2,z=-2..2,scaling=constrained,thickness=2,arrows=SLIM,shading=zhue,axes=frame,orientation=[30,75]);

The arrows are hard to see, away from the origin. This is because the length of the vectors becomes infinite as r goes to zero. It may be better to plot the vector field in an octant of space which doesn't include the origin. This is done in the next example.

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