Somewhere outside the Schwarzschild radius of every black hole is a region in which the path of incoming photons is 'bent' 180 degrees and they are sent back roughly in the direction from which they came.
In my mind this means that some infinitesimally small portion of the photons that fall on the earth every day were reflected from the earth ~50K years ago and sent in the direction of the black hole at the center of the Milky Way.
I sometimes wonder if we could build a telescope large enough to resolve these photons into an image of the earth from that time. This would likely require 5,000 years of technological development and construction, but it does seem like it's physically possible. (Maybe there's too much dust or distortion or background noise to actually pick out the signal, dunno)
We couldn't go back XXX million years, but maybe XX thousand?
In my mind this means that some infinitesimally small portion of the photons that fall on the earth every day were reflected from the earth ~50K years ago and sent in the direction of the black hole at the center of the Milky Way.
I sometimes wonder if we could build a telescope large enough to resolve these photons into an image of the earth from that time. This would likely require 5,000 years of technological development and construction, but it does seem like it's physically possible. (Maybe there's too much dust or distortion or background noise to actually pick out the signal, dunno)
We couldn't go back XXX million years, but maybe XX thousand?