The thing about aliens and UFO’s is simple. Earth is crawling with them. We are literally infested by them. We just don’t see them very often because they are in a different plane of reality. I’m not sure if their reality is faster or slower then ours but my guess would be faster. But once in while. . . when their space craft impulse engines misfire ( as impulse engines are known to do on occasion ) the craft slows way down ( or speeds way the hell up. . whichever ) this momentarily changes their natural reality, that’s when they become visible to us Earthlings. To them it probably happens so fast they don’t notice it but to us their space crafts may be visible for many seconds. It’s doubtful they even know humans exist on Earth. Or they might have a urban legend alleging the existence of Earthlings and laugh about it. Hope that clears up the whole UFO/Alien mess for everyone. . .