Ask the Federal Government, they've had plenty of experience(s) with time travel. It's not a myth or mystery at all, just speculation by one's who don't know or don't have a need to know--you'll never be told the truth. Or mis-informed and/or also told a half-truth. There are rules you must abide by and it's not quite like "Back to the Future", but similar in some respects.

This is a good episode.

I posted this video in the one thread about aliens being us from the future.