Extraterrestrials and Ultraterrestrials: Competing Explanations for UFO Phenomena

To the point

Two main explanations for UFOs divide the idea of beings from beyond Earth into extraterrestrials, from other worlds, and ultraterrestrials, from realms outside ordinary reality, with the extraterrestrial hypothesis long favored and supported by Drake's equation but criticized for long travel times and inconsistent or myth-like sightings, while ultraterrestrials propose extradimensional or custodial origins championed by John Keel and Jacques Vallee and remain untestable, leaving the true nature of UFOs unsettled, as Martin Luther King Jr. warned that visitors from beyond Earth might judge humanity harshly.