gravitational lensing

[jasonj]

would it be possible to look back at the earth through refracting of gravitational lensing. I'm not part of the scientific community, but I'd like to know if that's possible in any way. With all the massive gravitational fields in this galaxy maybe it could be a possibility to see a picture of the planet millenia ago?

[timo]

I'm not sure what you call "would it be possible". On the paper, you can take an isolated black hole and get any amount of light deviation you want; including the light-rays bending around 180° and coming back. In practice this 1) requires an isolated black hole and 2) does not ensure that the few rays being bent 180° are enough to provide any useful information. The gravitational field of a sun or any amount of suns is not going to be sufficient if that was your question. The reason is that the light deviation becomes stronger the closer you are to the center of the gravitating object. At a sun you have reached the sun's surface long before you get a sufficient deviation (e.g. deviations at our sun were measured in the order of 1°-2°, if I remember that correctly).

[swansont]

It was 1 - 2 seconds of arc, which is why it was so hard to do in ca. 1919.