This question already has an answer here:
Say nothing new can be learned anymore about the past by mere historical deduction from the present. Can a giant mirror-like thing out there that's let's say 2000 light years away from earth (and has been there since 4000 years ago) show us how things were on earth 4000 years ago? Could that be possible? I was thinking of this for some time and especially since it's been said that aliens would probably see dinosaurs and not humans on earth if they looked from millions of light years away, perhaps with some "super-binoculars".