The majority of all alien encounters can be explained as tricks of lighting, as illusions, or as identifiable physical phenomena. But not all reports fit any of these categories, and researchers conclude that there remains a category of UFO sightings that are unexplainable by appealing to physical law. This category--dubbed rUFOs for 'residual UFOs'--is, of course, the most interesting type.
This being the case, a good deal of research has been centered on rUFOs, and such research is made easy by the very wealth of available information and evidence. If you're at all interested in the findings of such research, I can do no better than recommend a comprehensive treatment of the issue (which remains, nonetheless, an easy read), Lights in the Sky and Little Green Men. But here, in a nutshell, is what can be known about rUFOs.
rUFOs are capable of producing physical effects but are not themselves physical. The physical effects produced by them include physical trauma (to soil, plants, animals, humans, and machines). Physical symptoms most commonly reported by humans who claim to have seen rUfOs include nausea, headache, blindness, paralysis, numbness, and recurring nightmares. Other observers have experienced serious injury or even death.
But while causing these and other physical effects, rUFOs are not themselves physical. They defy well-known laws of physics, they leave behind no physical artifacts (even when they have crashed to earth), they disintegrate and reintegrate, and make physically impossible turns and stops. Importantly, they are not seen most often by people who spend most of the night hours outside or watching the skies, and they appear most often to single individuals or very small groups, at 3:00 am (more often than earlier or later), and in rural rather than populated settings.
In short, rUFOs are real, but they are not physical. And to the modern scientific naturalist, this is nonsensical. But (as I have been at great pains to express in numerous other posts) scientific naturalism does not itself make adequate sense of the real world in which we live, and so we may reasonably continue this discussion.
Many scientists who have studied this phenomenon have come to the same conclusion, that rUFOs are demonic in nature. This conclusion is supported by a number of facts, including the following... They appear to a select few, and make repeat visits to the same individuals; they appear to be alive; they cause disturbing emotions and bodily and psychological harm; and they deceive their human contacts. Interestingly, throughout history, rUFOs have stayed just ahead of human technology in their appearance and claims, though these claims are clearly false to scientists of that day or of the next generation. Most importantly, those involved in encountering rUFOs invariably have a link in their lives to occult phenomena (participating in seances, astrology, ouija boards, channeling, and such).
The connection between rUFOs and occultism is especially clear with regard to encounters of the fourth and fifth kinds--abductions and contacts. Abduction is generally a negative experience ("ya think?"), with abductees suffering long-term emotional and psychological trauma, and often seeking professional therapy.
Contactees are those who claim to serve as human mouthpieces for alien 'masters' whom they perceive as wise and benificent. The most extreme and charismatic of these contactees become the founders of UFO cults, new religions that mix occult practices and UFOlogy. Some of the most famous of these are the Raelians and Heaven's Gate, the latter of which committed mass suicide in 1997 in order to catch a ride with the alien spaceship they believed was traveling with the Hale-Bopp comet.
With regard to contactees and their cults, researcher John Saliba writes,
Many UFO groups have borrowed heavily from both spiritualism and Theosophy. They have incorporated in their ideology the concepts of cosmic wisdom and cosmic masters who exist on other planets. Their leaders often channel, or communicate with, these masters through some psychic means (such as telepathy) or by entering into a trance-like state.*So there you have it. If extra-terrestrials existed, they would face insurmountable barriers--based in the laws of physics--to making contact with us. But modern astronomy and physics have demonstrated that Earth is uniquely designed for supporting intelligent life, and that it is astronomically unlikely that any other intelligent life exists in the entire universe. And those UFO sightings that cannot be explained by appealing to identifiable physical phenomena invariably involve people with a link to occult practices in their lives.
rUFOs are neither more nor less than demonic manifestations to those who have willingly opened their lives to such influences.
* Saliba, J.A. "Religious Dimensions of UFO Phenomena" in Gods have Landed. Cited in Ross, H, K. Samples, and M. Clark, Lights in the Sky and Little Green Men.