Imagine if someone actually discovered a way in which time travel is possible. Think about all the effects it would have. It would raise so many issues. People would straight away be wanting to goo back in time to fix this or kill these bad people or whatever. Others would be thinking what is ethical and should we change anything? What will the effects on our current state be?
I believe if we actually discovered a way to travel back in time, it would be one of the biggest disasters waiting to happen. What is it got into the wrong hands or someone altered something without carefully considering the after-effects? Changing something that we thought was bad, such as killing Hitler, might change the world in a negative way. I mean we simply view it as good - kill Hitler, save millions of lifes. But there are so many things that can happen as a result of this, things that we may not even begin to imagine.
Playing with the past, if we ever get the opportunity, is something that we shouldn't do. Just like angelic_ky said, everything happens for a reason.
Anyways, that's my two cents.
Greg
