Speculum Temporis - a partial solution? All the pictures you can see in a mirror are messages from the past. Photons must first travel from the object under survay to the mirror and back to the observer. Your do not think of that in the bathroom. But imagine that the mirror is located at the distance of one light year, the image you could see would be two years old. If all celestial bodies besides black holes are reflective, at least some of the photons we are detecting by watching the sky, must be reflections from our very own history. By tuning at the distance of N ly's, you could watch direct broadcast of what happened 2N years ago. This would help us to evaluate where to travel. I think this could possibly work for some signals in the timeframe of minutes inside our solar system. But could it be possible in the timeframe of years or hundred years for any kind of reflections? What do You think?