You know that when our telescopes see very distant stars, we are seeing the star's past. That light takes so long to get here that by the time we see it, the star may already be burned out. So we are, essentially, looking into the past. That raises the intriguing concept of aliens looking at our past from extremely far distances. What if we were to travel those distances ourselves, and see the Earth's own past? It would be like time traveling! As Dr. Phil Plait explains, that's not possible because we'd have to travel faster than the speed of light -much faster in order to see our past.
The impossible is what science fiction is for. In the short film Telescope, travel at faster-than-light speed has been achieved. The setting is 170 years in the future. The Earth is dead, with no evidence of organic life left. An astronaut they refer to as a "cosmic archaeologist" is in a spaceship on a quest to capture images of what Earth once was. He must travel further and further away to see that light from a time in which the Earth was alive. It's a sad but visually stunning mission.