PHYSICS · Subjective · Fermi University Physics · Relativity & Gravitation · Schwarzschild spacetime and the tests of general relativity · Schwarzschild spacetime and the tests of general relativity
The Geometry of Gravity, Ch Orbits and light rays in Schwarzschild spacetime
Problem
Someone argues: "Light falls freely, so the equivalence principle alone tells us it bends near a mass, exactly like a Newtonian particle moving at speed c. Doing that calculation at the solar limb (b=R⊙=6.96×108 m) gives Δϕ=2GM⊙/bc2=4.24×10−6 rad =0.875′′. Since the measured deflection is 1.75′′, exactly twice this, the equivalence principle has given half the answer with a numerical factor left over; a more careful equivalence-principle argument, done properly, must give the other half too, so the full 1.75′′ deflection is, in the end, purely a consequence of the equivalence principle." Find the error in this argument, and say which classical test(s) among the redshift, the deflection, the delay and the perihelion advance are, and are not, purely consequences of the equivalence principle.