UFOs, or unidentified flying objects, have perplexed humanity throughout our history. In the modern era, we speculate that sightings of objects that are not weather or other natural phenomena are technology-based. If they are not classified, or other not publicly known technology then they are speculated to be of alien origin (from other civilizations not of the Earth). Most UFO sightings have been explained away, but a tiny percentage (perhaps 5%) have not. These sightings usually have highly credible persons who have been the witnesses: pilots, military officers and personnel, scientists, law enforcement officers and others respected in their fields. There exists in the public record many photographic stills and videos but none are of high quality. Other evidence, such as radiation readings from soil where craft are said to have landed, and impressions made from indentations from these crafts’ landing gear have also been obtained. Again, nothing definitive. If there exists irrefutable evidence, it is held closely by government and military authorities for a variety of possible reasons.