# Looking at past events by observing sky? [duplicate]

Since solar system (and our galaxy) is constantly in motion at a great speed, is it possible that we can look at our own image as it was sometime ago? Since the light of that age takes sometime to reach us, is it possible that we can look at earth as it was at that point in time. In more simple case, if I go to Mars and start looking at earth in detail, I will be looking at past as seen from earth, correct? Now, relative to current position of earth, past position would have been very far (much farther than distance between Mars and Earth). So, can we look at past? As the distance increase, we are looking at older past. Please correct me if I'm wrong.

[Not a homework. Curious question]

No, the following statement is wrong (if I understand what you mean correctly):

Now, relative to current position of earth, past position would have been very far (much farther than distance between Mars and Earth).

Because you cannot move faster than the speed of light, you will not see the Earth in a past that much distant from your present. Remember, it takes only 8 minutes for the light of the Sun to reach the Earth. As a rough order of magnitude, the distance between Earth is Mars also makes the delay about 10 minutes. So from Mars, you see the Earth as it was 8 minutes ago ... while your trip to Mars took at least a few months.

When we look at the stars, we are indeed looking at the light coming from many years ago.(meaning we see the stars as they were many years ago) But you can certainly not look at yourself in the past. The fact that we can look at stars as they were many years ago now is because of the fact that light takes many years(and hence the information) to reach us. But if you want to look at yourself in the past, then you will have to travel faster than the speed of light, which is according to relativity, not possible. Certainly, as the distance increases, we are looking at older light.

In a way I guess your idea could be possible. I am reminded of the following:

You might have heard of the possibility of "looking at the back of your own head" from inside of a black hole. The idea is that due to the strong gravity of the black hole, the very photons themselves go into orbit around the black hole. So the light reflected off of the back of your head, could go into orbit around the black hole, wrap back around and eventually hit your eyes so that you "see" the back of your own head. You would effectively be looking at yourself in the past.

This is however a very dramatic example, and I would assume that in any reasonable situation it is not even remotely feasible to look at yourself in the past.