Space/time tourists getting a front row seat to the demise of a civilization? You know those historical river boat cruises you can take in Europe where it's al

Space/time tourists getting a front row seat to the demise of a civilization? You know those historical river boat cruises you can take in Europe where it's all tied into history lessons? Imagine that but for more advanced civilizations and the "UFOs" are actually tourist pods for aliens/time travelers to witness what Earth was like in the years before The Disaster. Perhaps the incidence of UFO sightings can be a bellwether for how close we are to the End....