Well, that’s a very novel approach to deleting your own posts. We’ll have to keep that in mind if we ever post nude pictures of ourselves after drinking 15 Molson’s and some sadistic mod locks out our account.
But seriously, how do you propose that it’s even possible to go back in time? Even if you don’t change anything, and just go back as a hands off observer, where are you? If you went back in time, you can’t deny that you’re in a real, tangible place. Everything in the universe—every last star, planet, and speck of dust is in the same place it was back then. What happened to the future? Have you erased it and now it’s gone? Or does it exist somewhere else? If so, where is this ‘somewhere else’? Let’s say you get bored one day and hop into your time machine. You go back ten years, look around for about an hour, and get back in and go back another ten years. Then you do this a few more times. Where are all these places? Have you recreated the entire universe in several different locations? Or, if you have erased the future, how can you be where you are? The future is gone—therefore the act of you getting in the time machine never occurred.
There might be a way to
observe the past, however. Remember that you don’t see an event until the light from the event reaches your eyes. So let’s say you want to witness JFK’s assassination. The light from that event is right now reaching a point forty light years away from Earth. At high warp, you could get out to that point in a few hours. You could then record the event, and recreate it on the holodeck. You could also use this technique to blackmail the mod into unlocking your account. As soon as your hangover goes away, you hightail yourself out to a point a few light days away from Earth, and you use infrared imaging to photograph him tossing off in the bathtub.
for explaining and this link 