Maybe that first thing that I saw really was not a spacecraft but instead some type of gate that allows space/time travel. That might explain how these unknown beings get here from some distant planet. Maybe some type of "gate" allows all kinds of different spacecraft to come through and then travel to different spots on the earth. The gate theory might explain why sightings over the centuries have described different sizes and shapes of UFOs. There may even be more than one type of being that visits the Earth.