The only explanation that makes sense is that the UFOs that are supposedly visiting Earth are actually humen time traveling to the past.
I thought it's already an accepted fact that time travel is possible, through time dilation. Although the term is used loosely. The theory is that when an object, in this case a person, moves at the speed of light, time stops for the traveler. The traveler is not necessary 'time traveling', but everything that is not moving at his/her speed is, in respect to the traveler. So the person moving at the speed of light is not traveling to the future, rather just not aging. Example, if a 20 year old person stops aging, 100 years later, that person would still be 20 years old, but everything else would have aged by 100, so that person traveled forward 100 years (again, term used loosely). I think the term 'gaining time' is more appropriate.
It sounds like you are basically adopting a theory of multiple parallel timelines or universes. In your scenario, you travel back in time and that particular "you" continues on his own timeline doing his own thing with everybody else's parallel "thems" while the rest of humanity in the future continues on their own timelines and may only know that you went back in time. The whole multiple universe/timeline thing is about the only way you can get away from the possible butterfly/grandfather paradox that may otherwise occur : you fly back in time, you make a small change that alters something, which in turn alters something else, and the change propagates forward to the point that you wouldn't exist in the future. For example, you go back and shoot your grandfather before he can create your father. If this happens then you, obviously, no longer can exist on this timeline since your father is no longer around. And if you no longer exist on this timeline, then how can you possibly fly back in time from the future to do what you just did? If you can't fly back to do what you just did, then you do exist in the future. But then ... well, you get the idea. :grin: Any philosophy majors around? Or better yet, any time travelers around?
I think time dilation and the time travel we're talking about are two different things. Time dilation and what you just proposed is the special theory of relativity's "twin paradox". I think what we're talking about, though, is people in 2050 going back to 1987 and putting some money down on the market. The dilation of time has been proven to happen among astronauts although at a miniscule level (I think B-Bob may have mentioned this).
Time travel could happen, but you'd need a far better car than that crappy DeLorean. At least a Camry or better.
Let's say multiple universe possibilities are infinite, then wouldn't mucking around with time travel (killing your grandfather) compound the possibilities even more? It'd be like visiting different worlds despite being in the same 3 dimensional coordinate in time, so then there'd be a world that happens 10 minutes before or 10 minutes after, maybe one that exists entirely in gas or water. Or a ripoff of the sci-fi show Sliders. And if multiple universes on a macro scale were the case, what if there were beings that exist in that extra dimension like a 3 dimensional being perceiving more than a 2 dimensional being. Imagine filling up water in a fish tank and dividing up each plane. When you put your hand through the water, each plane would have a different representation of your hand. If that were the case, then maybe there aren't multiple universes but are rather parts of a larger picture and scale that our minds can't begin to comprehend.
