Uncountably many photons have come from the sun, bounced off of me, and shot back into space. One day one of them is going to come back. Photons turn as they pass heavy things. A photon retreating from me is being turned, slowly, over billions of empty years, all the way around. A black hole can turn them around in one shot. Ancient photons are returning simultaneously, from all over, right now.
What it means is that we can see ourselves in the sky. At least one of those dots is the Earth in the past. If we manage to see it at all, we won’t start out seeing much more than a fuzzy dot, “Yep, there it is.” But there could be thousands or millions of earths in the sky. Each fragile broken circuit of light is a channel, or rather a mirror, showing the earth as it was or wasn’t 1, 2, 5, 8 billion years ago. Between them, you have the entire history of the earth being projected back to it at each moment.
The most interesting action is in the past millions and thousands of years. To open up the Earth’s human past we would need a black hole very close, within a few thousand light years, like V4641 Sgr, 1600 light years away. I want to watch the decline of Rome. Going further back, I want to see the earthquake that split the temple curtain. And I want to look in the sky and see an ancestor’s eyes as they look up to God. Not to be God, but to make eye contact full of love, and excitement, and no answers.
