We all know that this questions is totally related to the science. So there are many theories on this question, that have aliens ever visited Earth. The most recent one says, Yes Alien did visit Earth. A Harvard professor believe has miffed the scientific community. He says that he has scene a moving object into the air back in 2017. But there are many good reasons that scientist has listed to disagree with them. Nearly all scientist believe that they must have seen some asteroid or a comet like object that has left another star and travel through interstellar space. It happens every time when a scientist or a astrologer see something unusual into the atmosphere they mistake it by a spaceship. It maybe shipped by us, but of course not everyone agrees on this. Avi-Loeb, a Harvard professor of astronomy suggested in a recent book that it is indeed an alien spaceship. But how feasible is this and how come most scientists disagree with this claim. Researches estimate the milky way should contain around hundred million billion billion comets and asteroids adjectives from other planetary system and that one of these should pass through our solar system every year or so. So it makes sense that it could be one of these. We spotted another last year which is very common nowadays. So like this there are so many theories and incidents that says that aliens has visited the earth but there are so many facts that disagree with these theories and those all are sensible and valid at most of the point. By now there is no such confirmation that aliens ever have visited Earth.