Why do aliens come on earth? - An Unsolved Mystery

Some believe that nothing like the aliens, but on the other hand many people believe that Alien has always been present. But are the aliens present on the earth with us? Some believe that there may be aliens in the past. Many people think of the existence of aliens by looking at the sky. In the past, there have been some incidents that have indicated that the existence of aliens is essential.
Science and AliensLooking for life on other planets has been a very challenging task for science. But...