time travel

[Jhairric]

if someone were to travel back in time and change something how would you know. And if someone did change something they would have an immediate understanding of what they did and how it turned out wouldn't they? because up until the time they traveld throught time they would be living in the changed world and would have no idea that it was him that changed it. but really what is time it's just how long it takes the earth to rotate so how could you go back.....and what is the past? just your memories and how you precived things, so to go back in time you would in a sense have to convert everyones memories into reality which would only allow you to go back a limited amount of years. If any of this makes sense tell me becasue i always confuse myself when i think about this subject......