its actualy physically impossible since time is just an illusion by our brain that "explains" movement (which means that if everything stood still at the same time, you can say that time has stopped, but it would continue as soon as something moved), therefore time travel is impossible since time doesnt exist. BUT, if time actualy existed the way us humans think it does, meeting a time traveler who claims these things, there is no way she could prevent it, because the future comes from the past, and you can't change the past, practically the only thing you would have to do is doing whatever you want, since time "knows" what your mind would be thinking and therefore you believe you are doing something freely, but your actualy not.
holy forget this was hard to explain
well, my point is, some people say the past doesnt exist, and some people say the future doesnt exist, but i say time doesnt exist at all.
gg