(I am science fiction writer. I had a goal in my novel to argue that time travel to past will not be available even in future. I asked here how to argue that. I collected answers and analyzed them and in conclusion I came to following question:)
Question: It is said that there can be found theoretical observer somewhere in universe (moving with specific speed to specific direction) for whom for in his current moment there will be for example 1900 on earth, while you are reading this question in 2013. Is this statement true ?
If yes: Then can this phenomena used to build time machine ? (For example if such kind of observer exists he theoretically can teleport on prehistoric or on future earth).
If no: I d like to know why.
This subject is described in documentary movie - "Time in nutshell" on the example of alien. You can see the scene directly on link below (youtube)
It is awkward because if that is true for some alien on some place my grandmother is still alive.
Edit: Imagine the observer has no eyes to process light. It would be more interesting not to focus on the light or on the image of earth delivered to observer for the moment, but to focus on observer's INDIVIDUAL "now" or what is happening on earth for observer in the moment when he is far on another planet and moves with specific speed.