Einstein’s general theory of relativity (GR), the standard theory of gravity, has passed every high-precision test in the solar system, where gravitational fields are relatively weak. In those familiar precincts, the 97-year-old theory correctly predicts the gravitational bending, redshifting, and delaying of light; the precession of planetary orbits; and the strict equivalence of gravitational and inertial mass. But because GR has problems with quantization, spacetime infinities, cosmological inflation, and the unification of the fundamental forces, theorists widely anticipate that the true macroscopic gravity theory must diverge significantly from it in places with much stronger gravitational fields.
The gravitational field exerted by an extended object of mass M is said to be strong, in the sense of GR, when its Schwarzschild radius
Rs(M) ≡ 2GM/c2
is comparable to some physically relevant distance. The closest thing to a strong field in the solar system...
