UFOs aren't necessarily signs of extraterrestrial intrusion into Earth environment. They are very possibly a product of some top secret Earth science. There is NO doubt, however, that material objects of varied mass HAVE entered our environment from deep space. What is in doubt is whether or not intelligent beings have made close approach, or even landfall on this planet. It is self-delusion in the extreme, in my opinion, on the part of humanity to assume that the human race is the most highly developed life form in the universe, either in intelligence or technical achievement. I cannot imagine, at the same time, that any intelligence from outside our own Galaxy can have developed any kind of travel which would enable the journey to our wee planet to be undertaken. I am a strong believer in Einstein's statement that nothing material [possessing mass] can exceed the speed of light. The abilty to do just that would --according to even Newton's laws---entail a sudden transition into the PAST. That phenomenon would usurp the "causality law" --i.e. give someone literally the power to alter their own future. So I am inclined to suggest that any extraterrestrial visitors are from somewhere in the Milky Way. In this universe, there is nothing more certain than that there are millions of potential life-forming environments. To suggest otherwise is to deny the unimaginable vastness of the universe. But to traverse a distance of, say a million light years---a mere step in the vastness--when tied by the "causality law" means a million years of travel! Keep an open mind on the subject; if there is truth in the assertion that humans have a soul, it may well be that travel beyond light into the past IS after all feasible! [ Jeeze---what a ramble!!!]