I ask this question because as demonstrated in my paper here, we can define four more components of the gravitational field and this have the potential to explain the Rotation Curves of Spiral Galaxies, The Pioneer Anomaly, Planetary Rings, the Tituis-Bode Law etc. If this work prove correct in the future, then, it will become clear than our understanding of gravitation has been lacking.
Article Four Poission-Laplace Theory of Gravitation (I)