Alien Visitors or Time Travelers?

Simply put, time travel is not feasible.  A don't know of a website that engages in speculation about time travel other than some science fiction sites but your attempt to take aliens out of alien encounters is to be commended.

Uh, have you been paying attention to the news? You really think somebody is “bettering” the course of human history?

Are there people who take that scenario seriously? Probably. Is it worth pursuing? No, because time travel is impossible. Alien visitation is only improbable.

This sounds like the plot for at least 2 movies and several TV shows I have seen.

You’re the expert. Why don’t you know already? 

I saw two UFOs while in the Army (at the same time) so I have given this a lot of thought.  They moved at what I as an engineer would call impossible acceleration using what I know of physics.  They clearly were able to stop on a literal dime and accelerate to what seemed thousands of miles an hour in what appeared to me to be instantaneous.  I have concluded they must be from alien technology or from the future.  Since they are able to move so fast so rapidly, the necessity for them to be from the future is reduced and the likelihood that they can actually fly through interstellar space greatly increased.  

Have you considered that UFOs might be natural phenomena or military aircraft or mistaken witnesses or hoaxes? These are all much more likely than either extraterrestrials or time travelers. And there is no physical evidence at all for either ET or time travelers. 

It would seem to me that a great deal of your life has been wasted because your study of UFOs has failed to teach you that UFO is an abbreviation of unidentified flying object. That term refers to object seen by an observer that appears to be overhead but which the observer cannot identify. They are natural phenomena, e.g. flock of birds, or a man made phenomenon, e.g. weather balloon.

A UFO is not a spacecraft from another planet.

The Vulcan science directorate has determined that time travel is impossible. Therefore, the existence of time traveler is illogical. 

Thank you for all your answers, I guess I should have elaborated my question a little bit better to engage a stronger debate. I'm quite new to this platform, hopefully will get to find some good knowledge around here

Yes, that is one hypothesis.  However, UFOs can be adequately explained in much less interesting ways, e.g. misidentifications of Venus or secret military aircraft.

Everyone talks about bending space to go back in time, the only problem with that is that no matter how big the dimple you put in space, at one point to create a tunnel with two ends you have to tear through space and time, something that not even the largest black hole in the universe can do.  About the aliens, if there are aliens visiting this planet, then they are the ones who put us here.  What did one neutrino say to the other after traveling a billion years, nothing, it was alone the whole time and never once saw anything to let it believe otherwise even though the universe holds an infinite amount of them.  This applies to any lifeform in space, including us. Space is too big, the speed of light is infinitesimally too slow when compared to that size. 

Time traveling aliens from another dimension. 

There are ufo's and then there are UFO's.

there have been and there ARE Unidentified Flying Objects which to date, nobody has explained who,what where they came from.

we have had cases of strange debris , like spherical devices 'falling' out of skies and landing in forests and places around the world, made of elements unknown to man (they're not in our periodic table).

we cannot even drill through these or create a temperature high (or low) enough to alter their chemical, physical state even at the molecular and atomic level. 

which begs the question,  just WTF are these things and are they being deployed by an extremely smart entity ? could this entity be some form of alien species or dare i say it, some 'self aware' or even programmed UFO that deploys them ??

Aliens, in general, on other worlds? Certainly, it would almost be statistically impossible for them to NOT exist somewhere in the universe. Aliens advanced enough to come here?

Interstellar travel is SUCH an ENORMOUSLY difficult undertaking that automatically and by definition, any alien race capable of it is so advanced, that we could do nothing against them if they were hostile, and if they were interested in observation and/or blending in,,,,, they would be so good at it, that it would never seriously occur to us that they were visiting us. They'd be mind-bogglingly good at covering their tracks, better than any Area 51/X-Files (MIB, SciFi comedy etc...) would have us believe. Therefore, I don't know what UFO sighters/abductees are seeing, but I know what they are NOT seeing, namely, Aliens. So, no, I (and most other scientifically literate people) don't believe in aliens having visited Earth.

I've wondered about that for over 50 years, but you still can't reverse entropy. JFK was still assassinated in the universes I live in. What really happened over Washington D.C. in July 1948 and how many current members of Congress know about it? 

Try some of the physics stack exchanges. 

Your personal study appears to be too narrow. You are indeed correct in concluding that "alien encounters" are very definitely NOT from out of this world. There is in fact no evidence that this is so. But it should be pointed out that there is also no evidence that anything can "travel" backwards through time. Do you know enough of relativity and thermodynamics to understand why this is so?
But "alien encounters" are are real phenomenon. There is plenty of evidence that many people truly believe that a vague dot they see flying up in the air is a machine full of space boogiemen rather than a balloon, bird or plane. There are even folks who claim they have personal acquaintance with the occupants of these alleged machines. Peer reviewed physical evidence is distinctly absent in all cases. So what we are dealing with is a psychological phenomenon, and has nothing to do with the physical sciences such as astronomy.
To understand "alien encounters" you need to recruit the science of psychology. This will allow you to understand the source of these encounters and help you understand why some people passionately WANT space aliens to not only exist, but to crave to interact with them personally. You could start by participating in the psychology and mental health forums of which there are plenty.

Not something I contemplate often, but I came to same conclusion as you. No clue on studies and discussions about it.