: In contrast, Einstein provided the simpler explanation: that the astronomers' understanding of the physics of planetary motion was in error, and that the error lay in the understanding of the motion of Mercury, not the motion of any hypothetical planet inside the orbit of Mercury. | : In contrast, Einstein provided the simpler explanation: that the astronomers' understanding of the physics of planetary motion was in error, and that the error lay in the understanding of the motion of Mercury, not the motion of any hypothetical planet inside the orbit of Mercury. |