Now you are getting into the realms of fantasy.
If anyone has come back from the future sooner or later one of them would commit the ultimate paradox. One of them would alter the time line that would eventually lead to the none birth of the person committing the paradox. So he couldn’t come back and alter the time line because he didn’t exist. And if he didn’t exist there would be no one to come back and alter the time line.
There are undoubtedly strange goings on in our skies and our government, at least, must know something. Otherwise why keep the UFO files locked away for 30 years?
What you say about the paradox of time travel is correct.
It doesn’t rule out future technologies allowing it to be a possibility though. It may not be so fanciful after all.



