exceent article:
http://www.howstuffworks.com/time-travel.htm
howstuffworks.com is a great place for all technical answers like this one.
[quote:d40be]According to Einstein's theory of special relativity, time slows as an object approaches the speed of light. This leads many scientists to believe that traveling faster than the speed of light could open up the possibility of time travel to the past as well as to the future. [/quote:d40be]