Assuming time travel will exist...

According to physics, time travel is possible. And assuming we don't blow ourselves up anytime soon... we can assume that at some point humans will be able to travel through time. And if that's the case then we can assume there are people living among us now that have travelled here from the future. My question is this... how do we tell present-timers from future-timers? Will they use their knowledge against us? Should I be worried? Is my wife from the future?

I always use this argument as proof that time travel does NOT exist. If it did, people from the future would come back and steal all the great inventions, making themselves all powerful and rich. Since that hasn't happened yet, it may mean that the future hasn't happened yet and you can't travel back in time from something that hasn't happened yet. Ergo there is no future. No future timers, no knowledge used against you, and your wife is NOT from the future, otherwise she would have married somebody smarter and richer!! My wife says I'm mean to say that. I guess she's not from the future either!!

Oh c'mon guys...there is no...no...legitimate theory or even WAG that even hints that we might some day travel into the past. I think it's time that everyone open up their books to time travel in "The Fabric of the Cosmos" by Brian Greene or watch "Into the Universe with Stephen Hawking" on the Discovery Channel and pay attention to the several reasons why time travel into the past cannot be done...period.

And you, Asker, cite your source. You've made an outlandish assertion; back it up with a legitimate cite that we can all visit. If you have such a cite and it says time travel into the past might be possible, I'll be the first to say "wow that's cool" and apologize for disbelieving you.

Time travel to the past is a physical theory, not fact.