In my opinion, aliens do not exist. Earth is the only known planet that can sustain living creatures; this is a fact that has been proven time and time again by scientists. Therefore, in our galaxy, there is no other place that living beings could come from and thus there are no aliens.
some people have different views to this but honestly there are none. they woud've revealed themselves by now or over run us. but nope, all we have is fake ufo sightings and hollywood influence of these things.