Unfortunately, Feudalism would have been our only hope when aliens attack. See, they sent the Black Plague in order to destroy feudalism, to pave the way for their future take-over.

Of course, the premise of shows like Journeyman and Quantum Leap were that they were fixing the timeline.

Awfully hard to know if the timeline you're in is the right one.

I sure wish I had the powers of divination required to deduce what happens in seven hundred years of history when an incredibly major event was changed.

I go back 50 years make a few bets at the race track, put my winnings into a high yield account. No harm no foul. That's why self serving time travel is the only way to... time... travel

If only Ayn Rand wrote the "Virtue of Selfness - In Time Travel and Paradox"

I'm betting, if time travel is possible, it can only be done in the past (no future travel) and when you go back, you can't change anything really major that would cause you to not exist or not go back in the first place. So, you go back in time to try and kill Hitler, but every time you try, something goes wrong that couldn't have gone wrong, but it still did, eventually making you go insane.

Hell, time travel would probably make you insane. Meeting yourself and whatnot.

@Bob_of_Mars: or things would just balance out eventually anyways, like in End of Eternity

I have a time machine in my closet. Just get in there with me and it'll take us to the future. It only goes at the rate of one second per second though, because I don't have any polonium.

Time travel to the future is theoretically possible according to current physics, using relativistic time dilation. Travel at a sufficiently high speed away from Earth, then return, and more time will have passed on Earth than passed for you. You have essentially traveled to the future.

Of course, we don't have ships that go that fast, but nothing we know about physics forbids the scenario above.

As for actions in the past (killing Hitler, etc.) being forbidden by some mysterious force that prevents you from taking certain actions, well, that sort of goes against our common sense understanding of how reality works. We don't normally experience such restrictions on our free will, so it is hard for me to understand how a time traveler in the past would have these mysterious restrictions placed on his or her free will.

This article by Theodore Sider explores some of these issues.

@Bob_of_Mars: We already saw what happens when you kill hitler: You get an outlandish war with the Soviet Union where Kari Wuhrer goes commando in a tank top. At least, that's what Red Alert 2 told me....

Steve Holt!

@jamescole: Time Travel into the future isn't just possible, its mandatory! Time dilation can alter the speed of travel, but not the direction.