Is it possible to use a black hole as a mirror to the past ?

[john.phillip]

By seeing the way light is bent when passing close to massive objects, like Einstein's cross, I was wondering would it be possible for light to be bent so much, it would swung by the other side, similar to gravity assist maneuvers, and come back in an almost parallel direction, towards its source ?

To make it clearer, let's say there is a massive object (neutron star ? black hole ? other ?) some 50,000 light years away from the solar system, not hidden by gas or dust, just a clear path. If we point some kind of very large interferometric space telescope (so it can be relocated) towards the object, would it be possible to see our sun as it was 100,000 years ago ? Moreover, would it be possible to remove the image of the sun (using a mask or nulling interferometry perhaps) and get a "clear" picture of Earth 100,000 years ago ?

 

[cesiumfrog]

Yes. See "Einstein's ring". In fact, there will be infinitely many images of the Earth (one between each consecutive ring), and each corresponds to a slightly different age of the Earth, so in principle you could watch the entire history of the planet, if only you could capture enough photons (and with enough resolution)..

In practice I'd expect no.

 

[john.phillip]

Why consecutive rings lie between images of different ages ?

If consecutive ring gaps can show different ages, could the farther black holes reveal images of structures outside the visible universe ?