When in the US Paul Wild spent hours with Margaret's son, Tom Haddock, also a research scientist, discussing general relativity, the origin of inertia, the clever way the Soviet scientists Landau and Lifshitz developed their arguments on field theory, and then-current experiments such as the Gravity Probe B satellite to detect the general relativistic Lense-Thirring frame-dragging effect from the Earth's spin. The origin of inertia was a special interest Wild had, which they discussed at great length. Haddock reflected, "Physics went well beyond being Paul's profession; it was his hobby as well."