time travel part 2?

Question

There is a paradox in the whole time travel situation, if indeed it will be possible to travel back in time in the future, wouldn't we know it? By now wouldn't someone have came back in time to inform the past that there will be time machines in the future?If in fact there will be time travel in the future then what would stop some one from going back to say the birth of our nation, giving our founding fathers all kinds of up to date history books and technology and making America the only country in the world, there would also be a butterfly effect in time, because every action that the founding fathers would do to change the future would cause a new version of the same history book that the time travelers brought back, untill inevitably the book would say, "America wins all, end of story", or they would screw up the future so bad that there would be no time travel and the meeting would never take place.
If there was time travel into the past and delicate information was obtained from the time traveler, then if the recipient of thus said delicate information acted upon this information in a way that changed the time travelers history to where time travel was not invented, then the recipient would not know of it and the meeting would have never happened.

In theory, if time travel is created in the distant future, and lets say that the creator's great, great, great, great grandfather was killed in the towers on 9/11. Now if the first thing that the creator wanted to do is right this wrong and stop the twin towers from being hit, then most likely he would go back in time to eliminate the terrorist before they could attack, most likely he would kill them while they were children since children are less able to protect themselves from danger or death. Well, what if the creator did not take into consideration that upon 9/11 his great, great, great, great grandfather's son was upset about the death of his father and joined the military to avenge his father, and while in the middle east he met a woman, who unknown to him was a daughter of one of the terrorist, and he had relations with her and they brought forth a son from this that would become the creator's great, great grandfather. That means that if he went back in time to right the wrong, his great, great, great, great grandfather would not have died, his great, great, great grandfather would not have gone to war, met the woman, who does not exist now, since her father died as a kid, and brought forth his son, who is the creator's great, great grandfather, meaning that now the creator does not exist. Wow, so not only did 9/11 not happen now, but time travel will not happen either.

Answer 1

The laws of physics do not allow for it. It's inconsistent with quantum mechanics and relativity. I can't imagine being somewhere before I left for it.

Answer 2

The intensity of the emitted potential (watts according to sq. meter) drops off simply by fact the sq. of the area from the famous person. A given cubic meter of area it is 10 easy years from the famous person, includes basically a million/4 of the famous person's photons (subsequently a million/4 of the potential) as yet another cubic meter it is 5 easy years from the famous person. The famous person's potential does not disappear. It purely disperses into an ever-increasing quantity as you get farther and farther from the famous person. simply by fact the famous person is generating a FINITE quantity of photons each and every 2nd, the density of photons (subsequently the potential density) could decrease as those photons occupy ever-larger volumes of area.

Answer 3

Unless you go along with parallel universes and time being a circle not a line, time travel isn't ever going to be possible.

Answer 4

If something is changed in our present, how would we know?