2. Let us consider Hanging Observer (HO), standing in one place
in "r" distance to source of gravity. HO is useful, because any
body traveling through space, may be considered as body passing
spots where such observers stands. At least we, on Earth, are
such HOs. We denote HO proper time following Schwarzschild
metric as: So, we will denote above ratio as: 3. We may now
express Schwarzschild metric relative to such HO observers'
proper-times as: 4. So now, let us check geodesic for photon
relative to proper time of HO it passes. For every HO we have: