Time Travel IS possible. Maybe not in our lifetime but certainly in the next 200-300 years.
To accomplish this amazing feat we must adjust/ manipulate space in order to  change time. You cannot have one without the other. Space and time are the same : spacetime. So by changing one you will inevitably change the other. The twin paradox hints at this as well as new theories such as warpdrives. There are plenty of ideas, concepts and theories that physicists have that could potentially allow us to time travel.

for more info :

http://news.discovery.com/space/is-time-travel-possible.html

http://www.msnbc.msn.com/id/39152254/ns/technology_and_science-space/t/stephen-hawking-says-time-travel-should-be-possible-big-if/

http://news.yahoo.com/science-fiction-fact-time-travel-possible-163204591.html