I've asked this before, but received no response. What happens to light "trying to escape" from a black hole? Does it lose all its energy? Does the light leaving the sun lose some of its energy as it goes "uphill" the geometry of spacetime? And as E=hf, does this mean that the light shifts color? As light rides "downhill" as it comes to Earth, does it gain energy? Is this energy sort of like potential energy? If so, is there a level where this potential energy is zero (maybe black holes)?