Does anyone believe in time travellers

First...time is real. It is not just a construct of mankind's mind. The proof of that is that the rate of time can be altered by relativistic effects.

For example, at 1/4 light speed, one second on a spaceship would take 1.03 seconds to tick off as observed by someone on the outside, like on Earth. This so-called time dilation has been observed; so it's not just someone's pipe dream. If time were just someone's imagination, time dilation would not happen.

Second, the time line arrow points in only one direction...forward or increasing time interval. This is a result of something called entropy, which is just a fancy word for disorder. For example, when an egg breaks, that's increased entropy because now that once smooth well-ordered shell is now all over the kitchen cabinet in so-many bits and pieces that cannot be put back together.

Our universe is one of positive entropy, which means increasing disorder. Because of this trend from order to disorder, time can only go one direction...forward. In fact some models, like the causal dynamical triangularization theory, show that, without forward only time, our universe could not have formed as we now know it to be. [See source.]

Third, traveling forward into the future is possible using time dilation. For example, that space ship traveling 1/4 light speed would end up .03 years into the future after traveling in space for one year according to the space man's calendar.

So after a years junket according to the space man's chronometer, he'd find that his twin sister who remained on Earth would be .03 X 12 = .36 months (about 11 days) older than he is. Thus, if he landed on Earth on 15 December by his calendar, so as to be home for Christmas, he'd discover that it was already 26 December on Earth...bummer.

Scifi time travel is mostly fiction and very little science. Makes for fun viewing, but that's all it is...fun.

BTW: The fact that we've not met anyone from the future is not prima faciae evidence that time travel into the past is impossible. It might be evidence that time travel into the past beyond which time time travel was first created is impossible. Or that there is some law preventing an earlier body from coexisting with itself from the future. My point is, there are other explanations other than impossible time travel for why we've not met anyone from the future.

Source(s): July 2008 "Scientific American."