Alter the Past

The entire premise of X-Men: Days of Future Past is altering the past to create a new future/present. I don't want to include too many spoilers, but I will say the dude stealing away behind/between Wolverine and the young Professor X is William Stryker. Nothing like meeting your nemesis when he's a younger punk!

Rather than chatting about the movie itself, I am once again fascinated by and enamored of yet another view of time travel. Our culture, for the most part, believes time to be immutable and only running one way.  In science fiction, time often shows up as fluid. Sometimes it's immutable; sometimes it's changeable; sometimes it's a combination of the two ~ some incidents are fixed in time (like the death of JFK, the U.S. Civil War, the rise of Adolph Hitler....) and some are not. What a wild concept!

What do you think? Is time travel possible? Would you be interested in it? Why or why not? Do you think you can alter the past? Why would you want to?