Little thought experiment. An observer places a mirror and a clock 1 lightyear away from a black hole. He then goes in the black hole's gravitational field at a point where he sees the clock tick at 2 seconds per second. When he blinks a laser towards the mirror, he should see the light return to him in about 1 year from his reference frame, although the light traveled 2 lightyears total.
Is it more accurate to describe that the light really only traveled 1 lightyear, or that it traveled at 2c? Are they both equally good ways to describe the situation?
Just to push this a little bit, approaching the event horizon, the light signal would return almost instantly (The observer always stays at a constant distance from the black hole when waiting for the signal to return). Does space farther from the black hole contract to 0 from the observers frame or is it better to describe it as light moving at nearly infinite speed?
