I wonder if it would be possible to peek directly in our past-self by using gravitational lensing in such a way where we could (would be able to) calculate/triangulate the exact path and point a very powerful telescope in this very specific direction (on 2-3 or even more supermassive celestial objects) resulting in a bending of our vision (kind of like a slingshot stuff we do with probes/satellites) back at our direction capturing the emitted light (visual) of our past state (eg. the point we were in the past tense).

Would this be possible if we would have unlimited resources/technology? Or is space/universe too wast to pull this off?


1 Answer 1


It appears that the essence of the question is, "If light from an event is returned to the location of the event after some delay, does the light carry an image of the event and thus provide a view of the past?"

The answer is "yes". If there is a light-emitting event at point A, and the light travels to a mirror that is a distance D away from point A and is then reflected back to point A, it arrives back at point A after a delay of D/c seconds (c is the speed of light). Looking toward the mirror from point A, you will see what happened D/c seconds ago.

Your question was more specifically asking about steering light gravitationally rather than by mirrors in order to see into the past. A gravitational system to steer light back to a source is possible, so yes, it's possible (in principle) to see into the past. But the amount of angular deflection when light passes close to the Sun, for example, is only about 2 arc-seconds: about 1/3600 of a degree. So to turn a light ray 180 degrees and return it to the source would require on the order of 600,000 near-misses past masses comparable to the Sun.

Of course, there would be no travel into the past; at best it is only possible to see into the past.


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