Why is this so unbelievable to so many? More than likely, these aliens have a 'do not interfere' policy (or at least, most of them from the stories I've heard over the years).
If one were to think logically about it, with so many sightings over the decades (including my own), these aliens are already here or just visiting (and I am also assuming many different alien races, not just one). If they were hostile or not, and wanted the human race dead, we would be dead now (and we couldn't do anything about it, in reality).
And they are certainly not here for raw materials, water, etc. Plenty of that elsewhere in the Universe vs. coming to Earth for. More than likely, just like us, they are curious and watching/studying the human race and other species on Earth (just like us studying the Amazon tribes and others).
I assume that some kind of non-interference policy is in effect.
So yes, it maybe unbelievable to some that someone traveled thousands of light years at least to visit Earth but we've just scratched the surface of technology and knowledge of the heavens ('real' knowledge) in the last century or so here on Earth, so why isn't it possible to travel thousands of light years faster than the speed of light? Sure the technology or physics isn't available yet, but think about the advances we've seen over just the last 100 years alone, and think about the future possibilities to come. Exciting!
Unfortunately they are people on this planet today that don't believe we've traveled to the moon and back. They are people who are constantly harping about the evils that we're undergoing in today's society, blah, blah, blah, and that mankind is doomed! My answer to them? Get away from me, you doomsayer! Throughout history, your kind has been preaching irresponsibly to tens of millions of people, of the numerous dooms awaiting mankind, and you've been wrong ALL of the time.
If these craft really are from some state-sponsored agency here on Earth, then we would have already known about them, because I guarantee you this, that if someone had the technology to develop these vehicles, they would have already used them against their 'adversaries' here on Earth, and wouldn't hesitate to use them either against their adversaries.
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